JPWO2020070815A1 - Power conversion system - Google Patents

Abstract

The power conversion system (50) includes a power conversion device (10) and a transformer (1). The power conversion device (10) includes a converter (2a), a voltage sensor (5) for acquiring a DC voltage, and a control unit (3). The transformer (1) includes a primary winding (1a), a secondary winding (1b) and a tertiary winding (1c) to which the voltage sensor (6) is connected. The control unit (3) is a phase calculation unit (30) that calculates a reference phase from the acquired value of the voltage sensor (6), and an effective current that calculates an effective current command value based on the deviation between the DC voltage command value and the DC voltage. The first coefficient proportional to the square of the effective current command value is used by the first coefficient determined by the coupling inductance (74) of the command value calculation unit (320) and the transformer (1) and the received voltage of the transformer (1). The first invalid current command value calculation unit (324) that calculates the invalid current command value of 1, and the voltage command that calculates the AC voltage command value based on the reference phase, the effective current command value, and the first invalid current command value. A value calculation unit (34) is provided.

Description

The present invention relates to a power conversion system mounted on an electric vehicle and converting AC power output from an AC power source into DC power.

In general, an electric train is configured to take in electric power from an overhead wire with a current collector, use the taken-in electric power, and drive an electric motor with a power conversion device to run. In particular, in an electric vehicle that receives power from an AC power source, the electric vehicle passes through a transformer that steps down the overhead wire voltage, a converter that converts AC power into DC power, and an inverter that converts DC power into AC power. The mainstream method is to supply power to the electric motor that drives the transformer. Hereinafter, the term "electric vehicle" shall mean an electric vehicle that receives electric power from an AC power source. A device including a transformer, a converter, an inverter, and an electric motor is called a "propulsion control device".

Transformers for electric trains include primary windings that are connected to overhead wires, secondary windings that are connected to converters, and tertiary windings that are connected to other electrical equipment. Of these windings, the secondary winding has a one-to-one correspondence with the converter and often includes two or more. Further, the number of turns decreases in the order of the primary winding, the secondary winding, and the tertiary winding, in other words, the voltage generally decreases in the order of the primary winding, the secondary winding, and the tertiary winding. The primary winding is called a high pressure winding, and the secondary winding and the tertiary winding are called a low pressure winding.

Information on the overhead line voltage is required to control the converter. Here, a voltage sensor for acquiring the overhead wire voltage may be installed in the tertiary winding of the transformer. In the case of this configuration, the value acquired from the voltage sensor is converted by the turns ratio of the transformer and used for controlling the converter. By connecting the voltage sensor to the tertiary winding, a voltage sensor with lower withstand voltage performance can be used. The configuration of such a power conversion system is disclosed in, for example, Patent Document 1 below.

Japanese Unexamined Patent Publication No. 2005-304156

In the transformer of the electric vehicle described above, since three or more windings share a magnetic path, there is a magnetic coupling between all the windings. Therefore, the current flowing in one winding affects the voltage induced in the other winding. Specifically, the output of the voltage sensor connected to the tertiary winding changes depending on the magnitude of the power required by the converter connected to the secondary winding. As a result, there is a difference between the true overhead line voltage and the overhead line voltage obtained from the acquired value of the voltage sensor, and the power factor of the propulsion control device as seen from the overhead line, that is, the power factor on the primary side of the transformer controls the converter. There arises a problem that it is not controlled according to the command value of the vessel.

In Patent Document 1, the converter is intentionally operated so that the power factor is smaller than 1, specifically, a reactive current is passed so as to suppress fluctuations in the received voltage received by the transformer. The method of operation is disclosed. However, no consideration is given to the difference between the true overhead line voltage and the overhead line voltage obtained from the voltage sensor acquisition value, and the actual power factor is controlled according to the command value of the converter controller. There is no guarantee.

The present invention has been made in view of the above, and even when a voltage sensor is installed on the low voltage winding of the transformer to acquire the overhead line voltage, the power factor on the primary side of the transformer is set according to the command value. The purpose is to obtain a power conversion system that can be controlled.

In order to solve the above-mentioned problems and achieve the object, the power conversion system according to the present invention includes a power conversion device and a transformer. The power conversion device includes a converter that converts AC power into DC power, a first voltage sensor that acquires a DC voltage generated on the DC side of the converter, and a control unit that controls the operating state of the converter. The transformer includes a primary winding connected to an AC power supply, a secondary winding connected to a power converter, and a tertiary winding to which a second voltage sensor is connected. The control unit includes a phase calculation unit that calculates a reference phase from the acquired value of the second voltage sensor. Further, the control unit includes an effective current command value calculation unit that calculates an effective current command value based on the deviation between the DC voltage command value and the DC voltage acquired by the first voltage sensor. Further, the control unit uses the first coefficient determined by the coupling inductance of the transformer and the received voltage of the transformer as a proportional coefficient, and uses this proportional coefficient as the first invalidity proportional to the square of the effective current command value. A first invalid current command value calculation unit for calculating a current command value is provided. Further, the control unit includes a voltage command value calculation unit that calculates an AC voltage command value based on a reference phase, an effective current command value, and a first reactive current command value.

According to the power conversion system according to the present invention, even when a voltage sensor is installed on the low voltage winding of the transformer to acquire the overhead line voltage, the power factor on the primary side of the transformer can be controlled according to the command value. Play.

Configuration diagram of an electric vehicle drive system including the power conversion system according to the first embodiment Schematic diagram showing a configuration example of a main part of the power conversion system shown in FIG. A first vector diagram provided for explaining the operating principle of the converter shown in FIGS. 1 and 2. A second vector diagram for explaining the operating principle of the converter shown in FIGS. 1 and 2. A block diagram showing a basic configuration example of the control unit shown in FIGS. 1 and 2. A vector diagram relating to the current command value when the control unit shown in FIG. 5 operates. A block diagram showing a basic configuration example different from that of FIG. 5 of the control unit shown in FIGS. 1 and 2. The figure which shows the equivalent circuit which represented the transformer shown in FIG. 1 and FIG. 2 using an ideal transformer and a coupling inductance. A vector diagram provided for explaining the phase difference between the instantaneous current command and the secondary conversion power supply voltage that can occur in the control unit of FIG. 5 or FIG. The figure which shows the time waveform of the sensor acquisition voltage, the secondary conversion power supply voltage and the alternating current when the phase difference shown in FIG. 9 occurs. A first vector diagram provided for explaining the control method according to the first embodiment. The figure which shows the time waveform of the sensor acquisition voltage, the secondary conversion power supply voltage and the alternating current when the control method in Embodiment 1 is used. A second vector diagram provided for explaining the control method according to the first embodiment. A block diagram showing a configuration example of the current command value calculation unit according to the first embodiment. A block diagram showing an example of a hardware configuration that realizes an arithmetic function in the control unit of the first embodiment. A block diagram showing another example of a hardware configuration that realizes an arithmetic function in the control unit of the first embodiment. A block diagram showing a configuration example different from that of FIG. 14 of the current command value calculation unit according to the first embodiment. A first vector diagram provided for explaining the control method according to the second embodiment. A block diagram showing a configuration example of the current command value calculation unit according to the second embodiment. A block diagram showing a configuration example different from that of FIG. 19 of the current command value calculation unit according to the second embodiment. A block diagram showing a configuration example of a main part of the propulsion control device according to the third embodiment. The figure which shows the equivalent circuit which represented the transformer shown in FIG. 21 using an ideal transformer and a coupling inductance. Block diagram showing a configuration example of the current command value calculation unit according to the third embodiment A block diagram showing a configuration example of the current command value calculation unit according to the fourth embodiment.

The power conversion system according to the embodiment of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following embodiments.

Embodiment 1.
FIG. 1 is a configuration diagram of an electric vehicle drive system 100 including a power conversion system 50 according to the first embodiment. In FIG. 1, the electric vehicle drive system 100 includes a feeder system 110 and a propulsion control device 60 used for propulsion control of an electric vehicle (not shown). The feeder system 110 constitutes an AC power supply. The feeder system 110 includes a power supply facility 106 that generates AC power, and a power line 108 for supplying AC power to the propulsion control device 60.

The propulsion control device 60 includes a power conversion system 50 and a load 120. The power conversion system 50 converts the AC power received from the feeder system 110 into DC power and supplies it to the load 120. The power conversion system 50 includes a transformer 1 and a power conversion device 10. The transformer 1 steps down the received voltage and supplies it to the power converter 10.

The power conversion device 10 includes a converter 2a, a capacitor 2b, and a control unit 3. The converter 2a is a pulse width modulation (PWM) converter that mutually converts AC power and DC power. The converter 2a converts the AC power supplied from the electric power system 110 via the transformer 1 into DC power and supplies it to the load 120. The capacitor 2b is a smoothing capacitor that smoothes the output of the converter 2a.

Seen from the converter 2a, the side of the transformer 1 is called the "AC side", and the side of the load 120 is called the "DC side". The control unit 3 generates a PWM signal for PWM control of the converter 2a. The control unit 3 controls the operating state of the converter 2a by the PWM signal. Specifically, the control unit 3 controls the voltage on the DC side of the converter 2a. Further, the control unit 3 controls the current flowing in and out of the AC side of the converter 2a. Hereinafter, the voltage on the DC side of the converter 2a is referred to as "DC voltage of converter 2a" or simply "DC voltage". Further, the current flowing in and out of the alternating current side of the converter 2a is referred to as "alternating current of converter 2a" or simply "alternating current". Further, the voltage on the AC side of the converter 2a is referred to as "AC voltage of converter 2a" or simply "AC voltage". There are many well-known documents on the PWM signal generation method, and detailed description thereof will be omitted here.

The load 120 includes an inverter 120a and a motor 120b. The inverter 120a converts the DC power output from the converter 2a into AC power. The motor 120b is driven by the AC power converted by the inverter 120a. The motor 120b imparts propulsive force to an electric vehicle (not shown). The number of motors 120b driven by one inverter 120a may be plural.

Further, although FIG. 1 shows one inverter 120a connected to one power conversion device 10, one power conversion device 10 is configured to supply power to a plurality of inverters 120a. May be good. Further, a plurality of power conversion devices 10 may be configured to supply power to one inverter 120a. The case where there are a plurality of power conversion devices 10 will be described later.

FIG. 2 is a schematic diagram showing a configuration example of a main part of the power conversion system 50. In FIG. 2, in addition to the transformer 1 and the power conversion device 10 shown in FIG. 1, a current sensor 4, a voltage sensor 5 which is a first voltage sensor, and a voltage sensor 6 which is a second voltage sensor are shown. Is shown.

The transformer 1 has a primary winding 1a, a secondary winding 1b, and a tertiary winding 1c, as shown in FIG. The primary winding 1a is connected to the power line 108, the secondary winding 1b is connected to the converter 2a, and the tertiary winding 1c is connected to the voltage sensor 6. For the sake of simplicity, the number of the power conversion device 10 and the secondary winding 1b is shown as 1, but the number of the power conversion device 10 and the secondary winding 1b may be 2 or more. However, it is assumed that the power conversion device 10 and the secondary winding 1b have a one-to-one connection relationship.

The current sensor 4 acquires the current value of the alternating current is of the converter 2a. The voltage sensor 5 acquires the voltage value of the DC voltage Ed of the converter 2a. The voltage sensor 6 acquires the voltage value of the voltage v ^ s induced in the tertiary winding 1c. The acquired values of the current sensor 4 and the voltage sensors 5 and 6 are input to the control unit 3. Here, "v ^" in the notation "v ^ s" is an alternative notation of the character in which the circumflex "^" is arranged above the "v". In the present specification, the alternative notation is used except when it is inserted as an image. It is assumed that the acquired value of the voltage sensor 6 is converted into an equivalent value of the secondary voltage by using the turns ratio of the secondary winding 1b and the tertiary winding 1c in the transformer 1. The secondary voltage referred to here is a voltage induced in the secondary winding 1b. The turns ratio is also a voltage ratio. Hereinafter, "v ^ s" is referred to as "sensor acquisition voltage".

Next, the operating principle of the converter 2a will be described with reference to the drawings of FIGS. 3 and 4. FIG. 3 is a first vector diagram for explaining the operating principle of the converter shown in FIGS. 1 and 2. FIG. 4 is a second vector diagram for explaining the operating principle of the converter shown in FIGS. 1 and 2. The state in which positive power is transmitted from the AC side to the DC side of the converter 2a is defined as "power running", and the state in which positive power is transmitted from the DC side to the AC side is defined as "regeneration". According to these definitions, the alternating current is of the converter 2a acquired by the current sensor 4 has a positive direction of flowing into the converter 2a.

FIG. 3 shows the relationship between the voltage vector and the current vector in the steady state when the converter 2a consumes power at a power factor of 1. In FIG. 3, “is” is the alternating current of the converter 2a, “xl” is the leakage reactance of the transformer 1, and “vc” is the alternating voltage of the converter 2a. Further, "vs" is a value obtained by converting the received voltage received by the transformer 1 from the power line 108 into an equivalent value of the secondary voltage using the turns ratio of the primary winding 1a and the secondary winding 1b in the transformer 1. .. "Vs" is called "secondary conversion power supply voltage".

In the transformer 1, a resistance component actually exists in addition to the leak reactance xl. The combination of the resistance component and the leak reactance xl is called "leakage impedance". In the leakage impedance, the resistance component is sufficiently small as compared with the reactance component. Therefore, in the following description, the resistance component is ignored for the sake of simplicity.

In the power factor 1 and the steady state, as shown in FIG. 3, the alternating current is and the secondary conversion power supply voltage vs. have a phase relationship. The voltage drop due to the leakage reactance xl of the transformer 1 can be expressed as "jxlis". “J” is an imaginary unit, and the voltage drop jxlis has a phase advanced by 90 degrees from the alternating current is and the secondary conversion power supply voltage vs. Here, the voltage difference between the secondary conversion power supply voltage vs. the AC voltage vc of the converter 2a is applied to the leakage reactors xl to generate an AC current is. The vector addition is equal to the secondary conversion power supply voltage vs. That is, there is a relationship of vs = vc + jxlis between the secondary conversion power supply voltage vs. the AC voltage vc and the voltage drop jxlis.

Further, FIG. 4 shows the relationship between the voltage vector and the current vector in the steady state when the converter 2a is regenerating power at a power factor of 1. In FIG. 4, the alternating current is and the secondary conversion power supply voltage vs. have an opposite phase relationship. Here, the voltage drop jxlis due to the leakage reactance xl of the transformer 1 has a phase advanced by 90 degrees with respect to the alternating current is, but has a phase delayed by 90 degrees with respect to the secondary conversion power supply voltage vs. The relationship of vs = vc + jxlis is established in the same manner as in the vector diagram of FIG. 3, and the vector addition of the AC voltage vc and the voltage drop jxlis due to the leakage reactance is equal to the secondary conversion power supply voltage vs.

That is, the vector diagrams of FIGS. 3 and 4 show that the AC current is can be controlled to an arbitrary amplitude and phase by adjusting either one or both of the amplitude and phase of the AC voltage vc. There is.

Next, the basic configuration and operation of the control unit 3 shown in FIGS. 1 and 2 will be described with reference to the drawings of FIGS. 5 and 6. FIG. 5 is a block diagram showing a basic configuration example of the control unit 3 shown in FIGS. 1 and 2. FIG. 6 is a vector diagram relating to the current command value when the control unit shown in FIG. 5 operates.

The control unit 3 shown in FIG. 5 includes a phase calculation unit 30, a current command value calculation unit 32, a voltage command value calculation unit 34, and a switching command generation unit 36. The operation of each part will be described below.

The phase calculation unit 30 generates the voltage phase θ based on the sensor acquisition voltage v ^ s. The voltage phase θ serves as a reference phase when the instantaneous current command value is *, which will be described later, is generated. Hereinafter, this voltage phase is referred to as a "reference phase". The reference phase θ is input to the voltage command value calculation unit 34. As for the configuration of the phase calculation unit 30, various known methods have been proposed, and detailed description thereof will be omitted here.

The current command value calculation unit 32 sets the effective current command value Ip and the invalid current command value Iq based on the DC voltage command value Ed *, the DC voltage Ed acquired from the voltage sensor 5, and the power factor angle command value φ. It is a component that calculates. Specifically, as shown in FIG. 5, the current command value calculation unit 32 includes a subtractor 321, a voltage control unit 322, a tangent value calculation unit 336, and a multiplier 323. The DC voltage command value Ed * is a command value for controlling the DC voltage Ed to a desired value.

The subtractor 321 calculates the DC voltage deviation, which is the deviation between the DC voltage command value Ed * and the DC voltage Ed. The voltage control unit 322 calculates the effective current command value Ip based on the output of the subtractor 321. The effective current command value Ip is input to the voltage command value calculation unit 34 and the multiplier 323. The subtractor 321 and the voltage control unit 322 constitute an effective current command value calculation unit.

Further, the tangent value calculation unit 336 calculates the tangent value of the power factor angle command value φ, that is, the tangent. The multiplier 323 multiplies the effective current command value Ip by the output of the tangent value calculation unit 336. The output of the multiplier 323 is input to the voltage command value calculation unit 34 as the reactive current command value Iq. The tangent value calculation unit 336 and the multiplier 323 constitute a reactive current command value calculation unit.

A proportional integral (PI) compensator is often used for the voltage control unit 322. Further, when the power factor angle command value φ is given, the relationship between the active current command value Ip and the reactive current command value Iq that achieve the desired power factor is given by the following equation.

Therefore, in the current command value calculation unit 32 of FIG. 5, the value obtained by multiplying the effective current command value Ip by tanφ, which is the tangent value of the power factor angle command value φ, is defined as the invalid current command value Iq. In the case of FIG. 5, when the power factor angle command value φ is positive, the reactive current command value Iq is also positive, and Iq represents the advancing reactive current. When the power factor angle command value φ is negative, the reactive current command value Iq is also negative, and Iq represents the delayed reactive current. When the reactive current command value Iq is determined in this way, the instantaneous current command value is *, which will be described later, is calculated so that the power factor of the AC power follows a desired value. On the other hand, when it is desired to make the reactive electric energy follow a desired value, it is also possible to directly calculate the reactive current command value Iq by another means without using the power factor angle command value φ.

Next, the voltage command value calculation unit 34 will be described. The voltage command value calculation unit 34 is a component that calculates the instantaneous current command value is * based on the active current command value Ip, the reactive current command value Iq, and the reference phase θ. Further, the voltage command value calculation unit 34 is an AC voltage command value which is a command value of the voltage to be output to the AC side by the converter 2a based on the instantaneous current command value is * and the AC current is acquired from the current sensor 4. It is a component that calculates vc *. Specifically, as shown in FIG. 5, the voltage command value calculation unit 34 includes a sine value calculation unit 341, a cosine value calculation unit 342, a multiplier 343, 344, an adder 345, and a subtractor 346. , A current control unit 347 is provided.

The sine value calculation unit 341 calculates the sine value of the reference phase θ, and the cosine value calculation unit 342 calculates the cosine value of the reference phase θ. The multiplier 343 multiplies the effective current command value Ip, which is the output of the current command value calculation unit 32, with the sine value of the reference phase θ, which is the output of the sine value calculation unit 341. The multiplier 344 multiplies the invalid current command value Iq, which is the output of the current command value calculation unit 32, with the cosine value of the reference phase θ, which is the output of the cosine value calculation unit 342. The adder 345 adds Ipin θ, which is the output of the multiplier 343, and Iqcos θ, which is the output of the multiplier 344. The output of the adder 345 is the instantaneous current command value is *. The instantaneous current command value is * is a command value of the current to be passed to the AC side of the converter 2a.

Here, the active current command value Ip and the reactive current command value Iq are both DC quantities, whereas the instantaneous current command value is * is an AC quantity. Further, in the configuration of FIG. 5, the product of the effective current command value Ip and the sin θ which is the sine value of the reference phase θ is set as the AC amount having the same phase as the sensor acquisition voltage v ^ s, and the invalid current command value Iq and the reference phase θ The product of cos θ, which is the cosine value of, is the amount of alternating current having a phase difference of 90 degrees with respect to the sensor acquisition voltage v ^ s. That is, in the configuration of FIG. 5, the reference phase θ is based on the sine value of the sensor acquisition voltage v ^ s. Therefore, the sensor acquisition voltage v ^ s and the instantaneous current command value is * have the relationship shown in the vector diagram of FIG.

The instantaneous current command value is * is input to the subtractor 346. The subtractor 346 calculates the deviation between the instantaneous current command value is * and the alternating current is. The alternating current is is the alternating current of the converter 2a acquired by the current sensor 4. The current control unit 347 amplifies the deviation between the instantaneous current command value is * and the AC current is, and outputs the amplified signal as the AC voltage command value vc * to the switching command generation unit 36. A proportional (P) compensator or a PI compensator is often used for the current control unit 347.

The switching command generation unit 36 generates a switching command sw * based on the AC voltage command value vc *. The switching command sw * is a PWM signal for PWM control of the converter 2a. The method for generating the switching command sw * is based on a known method, and detailed description thereof will be omitted here.

The voltage command value calculation unit 34 shown in FIG. 5 may be replaced like the voltage command value calculation unit 35 shown in FIG. 7. FIG. 7 is a block diagram showing a basic configuration example different from that of FIG. 5 of the control unit 3 shown in FIGS. 1 and 2. In FIG. 7, the same or equivalent components as those in FIG. 5 are designated by the same reference numerals.

In the configuration of FIG. 5, the current command value is converted into an alternating current amount, whereas in the configuration of FIG. 7, the actual current is converted into a direct current amount. Specifically, as shown in FIG. 7, the voltage command value calculation unit 35 includes a rotating coordinate conversion unit 351, a subtractor 352, 353, a current control unit 354, 355, and a static coordinate conversion unit 356. .. The voltage command value calculation unit 35 shown in FIG. 7 has an effective current command value Ip, an invalid current command value Iq, a reference phase θ, and a current, similarly to the voltage command value calculation unit 34 shown in FIG. Based on the AC current is acquired from the sensor 4, the converter 2a calculates the AC voltage command value vc *, which is the voltage to be output to the AC side.

The rotational coordinate conversion unit 351 converts the alternating current is into a value on the rotational coordinates using the reference phase θ, and the actual reactive current Ip'which is a component in phase with the sensor acquisition voltage v ^ s and the sensor acquisition voltage v. Calculate the actual reactive current Iq', which is a component having a phase difference of 90 degrees with respect to ^ s.

The subtractor 352 calculates the deviation between the effective current command value Ip, which is the output of the current command value calculation unit 32, and the actual effective current Ip', which is the output of the rotating coordinate conversion unit 351. Further, the subtractor 353 calculates the deviation between the invalid current command value Iq, which is the output of the current command value calculation unit 32, and the actual invalid current Iq', which is the output of the rotating coordinate conversion unit 351.

The current control unit 354 amplifies the deviation between the effective current command value Ip and the actual effective current Ip', and outputs the amplified signal as the p-axis voltage command value vp * to the static coordinate conversion unit 356. Further, the current control unit 355 amplifies the deviation between the reactive current command value Iq and the actual reactive current Iq', and outputs the amplified signal as the q-axis voltage command value vq * to the static coordinate conversion unit 356.

The static coordinate conversion unit 356 converts the p-axis voltage command value vp * and the q-axis voltage command value vq * into values on the static coordinates using the reference phase θ, and uses the converted values as the AC voltage command value vc *. It is output to the switching command generation unit 36.

When the AC power is single-phase, the instantaneous space vectors of voltage and current cannot be defined, so additional arithmetic processing is required for mutual conversion between the rotating coordinates and the stationary coordinates. Specifically, when the AC current is is converted into a rotating coordinate, jis, which is a 90-degree phase-advancing component of the AC current is, is calculated in advance, and the rotating coordinate conversion is performed on the AC current is and jis. If the transformation matrix here is C, the transformation matrix C is expressed by the following equation.

It should be noted that the above equation (2) has a different transformation matrix depending on how the reference phase θ is defined.

Further, using the transformation matrix C of the above equation (2), the above-mentioned actual active current Ip'and actual reactive current Iq' are expressed by the following equations.

Further, the AC voltage command value vc * is expressed by the following equation using the conversion matrix C of the above equation (2).

Next, the influence of the transformer 1 on the control will be described with reference to the drawings of FIGS. 8 to 10. FIG. 8 is a diagram showing an equivalent circuit in which the transformers shown in FIGS. 1 and 2 are represented by using an ideal transformer and a coupling inductance. FIG. 9 is a vector diagram provided for explaining the phase difference between the instantaneous current command value is * and the secondary conversion power supply voltage vs. that may occur in the control unit of FIG. 5 or FIG. FIG. 10 is a diagram showing time waveforms of the sensor acquisition voltage v ^ s, the secondary conversion power supply voltage vs, and the alternating current is when the phase difference shown in FIG. 9 occurs.

In FIG. 8, the transformer 1 is represented by an ideal transformer 70 and a coupling inductance 74. The coupling inductance 74 represents the leakage inductance between the high-voltage winding and the low-voltage winding of the transformer 1 and the magnetic coupling between the low-voltage windings. Leakage inductance is also referred to as leakage reactance.

In FIG. 8, “v1” is the primary voltage, “v2” is the secondary voltage, “v3” is the tertiary voltage, “i1” is the primary current, “i2” is the secondary current, and “i3” is the tertiary current. There is. That is, the primary voltage v1 is the voltage applied to the primary winding, and the primary current i1 is the current flowing through the primary winding. Further, the secondary voltage v2 is the voltage induced in the secondary winding, the secondary current i2 is the current flowing in the secondary winding, the tertiary voltage v3 is the voltage induced in the tertiary winding, and the tertiary current i3 is the tertiary current. The current flowing through the winding. For convenience of explanation, the primary winding may be referred to as a "high pressure winding", and the secondary winding and the tertiary winding may be collectively referred to as a "low pressure winding". Further, "n2" represents the turns ratio of the secondary winding to the primary winding, and "n3" represents the turns ratio of the tertiary winding to the primary winding. If the number of turns of the primary winding is represented by "1" as shown in the figure, the number of turns ratio n2 and the number of turns ratio n3 are real values of 0 or more and less than 1.

Here, in the equivalent circuit of FIG. 8, the circuit equations of the following equation and the following equation are established.

The coefficient matrix on the right side in the above equation (6) is called a "reactance matrix". The reactance matrix is a parameter in which the coupling inductance 74 is expressed by impedance. The diagonal term of the reactance matrix is a term derived from the self-inductance of the low-voltage windings, and the off-diagonal term is a term derived from the mutual inductance of the low-voltage windings. The reactance matrix is a symmetric matrix. By expanding the second line of the above equation (6), the following equation is obtained.

According to the above equation (7), it can be seen that the tertiary voltage v3 changes depending on the current of the low voltage winding.

Further, by modifying the above equation (7), the following equation can be obtained.

Here, in the configuration of FIG. 2, the load of the tertiary winding 1c is only the voltage sensor 6, and the current flowing through the voltage sensor 6 is small, so that the tertiary current i3 = 0. In the case of an electric vehicle, another load such as an auxiliary power supply device may be connected to the tertiary winding 1c, but in most cases, the power capacity is smaller than that of the converter of the secondary winding. Therefore, ignoring the tertiary current i3 and setting the tertiary current i3 = 0 is a reasonable and reasonable assumption.

Further, the left side of the above equation (8) is a value obtained by secondary conversion of the primary voltage v1, and this value is defined as the secondary conversion power supply voltage vs. defined above. Further, the first term on the right side is a value obtained by quadratic conversion of the acquired value of the voltage sensor 6, and is equal to the sensor acquired voltage v ^ s. Then, the secondary current i2 of the transformer 1 is equal to the alternating current is of the converter 2a, and the alternating current is controlled by the instantaneous current command value is *, so i2 = is *. Further, assuming that the proportional coefficient of the second term on the right side is xm = (n2 / n3) x32, the following equation is obtained.

Assuming that the control target has a power factor of 1 and the reactive current command value Iq is zero, the relationship of the above equation (9) can be represented by the vector diagram of FIG. In FIG. 9, the instantaneous current command value is * is in phase with the sensor acquisition voltage v ^ s. Further, there is a phase difference angle δ between the sensor acquisition voltage v ^ s and the secondary conversion power supply voltage vs. Therefore, a phase difference corresponding to the phase difference angle δ also occurs between the instantaneous current command value is * and the secondary conversion power supply voltage vs.

At this time, the time waveforms of the sensor acquisition voltage v ^ s, the secondary conversion power supply voltage vs, and the AC current is are as shown in FIG. In FIG. 10, the sensor acquisition voltage v ^ s and the alternating current is are shown by solid lines, and the secondary conversion power supply voltage vs. is shown by broken lines. As shown in FIG. 10, there is a phase difference corresponding to the phase difference angle δ between the sensor acquisition voltage v ^ s and the secondary conversion power supply voltage vs. Further, the alternating current is is controlled to follow the instantaneous current command value is *, and as a result, has the same phase as the sensor acquisition voltage v ^ s. Therefore, a phase difference corresponding to the phase difference angle δ is also generated between the secondary conversion power supply voltage vs. the alternating current is. This means that even if the control target has a power factor of 1, the power factor seen on the primary side of the transformer 1 is not 1.

As described above, in the basic configuration shown in FIG. 5 or 7, the sensor acquisition voltage v ^ s may have a phase different from that of the secondary conversion power supply voltage vs. As a result, there may be a problem that the power factor of the AC power or the amount of ineffective power seen on the primary side of the transformer 1 does not become as instructed by the control unit 3. Therefore, the control method of the first embodiment that solves this problem by correcting the instantaneous current command value is * will be described below.

FIG. 11 is a first vector diagram provided for explaining the control method according to the first embodiment. First, as shown in FIG. 11, an axis having the same phase as the sensor acquisition voltage v ^ s is defined as the p-axis, and an axis having a phase advanced by 90 degrees with respect to the p-axis is defined as the q-axis. Next, assuming that the instantaneous current command value is * is in phase with the secondary conversion power supply voltage vs., the instantaneous current command value is * is decomposed into a p-axis component ip and a q-axis component iq1'. Here, the amplitude of the p-axis component ip corresponds to the effective current command value Ip output from the current command value calculation unit 32 in the configuration of the control unit 3 shown in FIG. 5 or FIG. Further, the amplitude of the q-axis component iq1'is newly defined as the first reactive current command correction value Iq1'. When the vector diagram of FIG. 11 is geometrically solved, the relationship between the active current command value Ip and the first reactive current command correction value Iq1'is expressed by the following equation.

Here, if k = xm / | vs |, the above equation (10) is expressed by the following equation.

At this time, the time waveforms of the sensor acquisition voltage v ^ s, the secondary conversion power supply voltage vs, and the AC current is are as shown in FIG. FIG. 12 is a diagram showing time waveforms of the sensor acquisition voltage v ^ s, the secondary conversion power supply voltage vs, and the alternating current is when the control method according to the first embodiment is used.

According to FIG. 12, there is a phase difference corresponding to the phase difference angle δ between the sensor acquisition voltage v ^ s and the secondary conversion power supply voltage vs. However, as shown in FIG. 11, since the instantaneous current command value is * is in phase with the secondary conversion power supply voltage vs., in FIG. 12, the alternating current is controlled to be in phase with the secondary conversion power supply voltage vs. Has been done. Compared with the waveform of FIG. 10, the phase difference between the secondary conversion power supply voltage vs. the alternating current is is eliminated. Therefore, it means that the power factor seen on the primary side of the transformer 1 is 1.

FIG. 13 is a second vector diagram provided for explaining the control method according to the first embodiment. FIG. 13 is a vector diagram similar to that of FIG. 11 in the case of regenerative operation having a power factor of 1. In the case of regenerative operation with a power factor of 1, the instantaneous current command value is * is in the opposite phase to the secondary conversion power supply voltage vs. the first reactive current command correction value Iq1'is 90 degrees with respect to the active current command value Ip. It becomes a lag phase. On the other hand, the relationship between the active current command value Ip and the first reactive current command correction value Iq1'is the same as in the case of FIG. 11, and satisfies the relationship of the above equation (11).

The sign of Iq1'satisfying the above equation (11) is positive regardless of the sign of Ip when k> 0. In other words, when xm> 0, the value of the first reactive current command correction value Iq1'is positive regardless of power running or regeneration. On the contrary, when xm <0, the value of the first reactive current command correction value Iq1'is negative regardless of power running or regeneration.

By the way, since the equation (11) includes the calculation and division of the square root, it cannot be said that the calculation load is light. Therefore, we try to simplify equation (11). If the base capacitance is Sb, the base voltage is | vs |, the base impedance is Zb, and xm and Ip expressed in the unit method are% x and% i, respectively, Ip = (Sb / | vs |) x% i, The relationship of xm = Zb ×% x = (| vs | ² / Sb) ×% x holds. By substituting these relationships into the denominator of the above equation (11), the following equation is obtained.

On the right side of the above equation (6), the diagonal term of the reactance matrix is several% to several tens of% with respect to the base capacitance. Further, the off-diagonal terms of the reactance matrix are generally smaller than the diagonal terms. Therefore, in the above equation (12), ^{since it can be regarded as (% x) 2} << 1, it can be approximated as ^{Iq1'≈kIp 2.} Therefore, as shown in the following equation, the first reactive current command correction value Iq1'after approximation is newly defined as the first reactive current command value Iq1.

From the above, the voltage command value calculation unit 34 may calculate the AC voltage command value vc * based on the first reactive current command value Iq1. As a result, the purpose of controlling the power factor of the AC power seen on the primary side of the transformer 1 to 1 is achieved by a very simple calculation. The configuration of the current command value calculation unit that achieves this function is as shown in FIG. 14, for example. FIG. 14 is a block diagram showing a configuration example of the current command value calculation unit according to the first embodiment. In FIG. 14, the same or equivalent components as those in FIG. 5 or 7 are indicated by the same reference numerals and symbols.

In the current command value calculation unit 32 shown in FIG. 5 or 7, the current command value calculation unit 32A shown in FIG. 14 replaces the tangent value calculation unit 336 and the multiplier 323 with the first invalid current command value calculation. A unit 324 is provided. In FIG. 14, the subtractor 321 and the voltage control unit 322 constitute an effective current command value calculation unit 320. The effective current command value Ip calculated by the effective current command value calculation unit 320 and the coefficient k, which is the first coefficient, are input to the first invalid current command value calculation unit 324. Here, the coefficient k is represented by k = xm / | vs | as described above. Further, the proportional coefficient xm is a coefficient derived from the coupling inductance 74 of the transformer 1. The secondary conversion power supply voltage | vs | is a value determined by the received voltage of the transformer 1. Therefore, the coefficient k can be determined by the coupling inductance 74 of the transformer 1 and the received voltage of the transformer 1.

The first invalid current command value calculation unit 324 calculates the first invalid current command value Iq1 which is proportional to the square of the effective current command value Ip, with the coefficient k as a proportional coefficient. The effective current command value Ip and the first reactive current command value Iq1 calculated by the current command value calculation unit 32A are input to the voltage command value calculation unit 34 or 35 shown in FIG. 5 or 7. After that, the AC voltage command value vc * is calculated based on the active current command value Ip and the first reactive current command value Iq1, and the switching command sw * is generated based on the AC voltage command value vc *, and the converter 2a The operating state of is controlled.

As described above, according to the first embodiment, the current command value calculation unit provided in the control unit uses a coefficient k determined by the coupling inductance of the transformer and the received voltage of the transformer as a proportional coefficient. The first reactive current command value proportional to the square of the effective current command value is calculated and output to the voltage command value calculation unit together with the effective current command value. Then, the voltage command value calculation unit calculates the AC voltage command value based on the reference phase calculated from the acquired value of the second voltage sensor, the effective current command value, and the first reactive current command value. As a result, even when a second voltage sensor is installed on the tertiary winding of the transformer to acquire the overhead line voltage, the power factor on the primary side of the transformer can be controlled according to the command value.

Next, the hardware configuration for realizing the calculation function in the control unit 3 of the first embodiment will be described with reference to the drawings of FIGS. 15 and 16. FIG. 15 is a block diagram showing an example of a hardware configuration that realizes a calculation function in the control unit of the first embodiment. FIG. 16 is a block diagram showing another example of a hardware configuration that realizes a calculation function in the control unit of the first embodiment.

When a part or all of the arithmetic functions in the control unit 3 of the first embodiment are realized by software, as shown in FIG. 15, the processor 300 that performs the arithmetic and the program read by the processor 300 are saved. The configuration may include a memory 302 and an interface 304 for inputting / outputting signals.

The processor 300 may be a computing means such as an arithmetic unit, a microprocessor, a microcomputer, a CPU (Central Processing Unit), or a DSP (Digital Signal Processor). Further, the memory 302 includes a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Program ROM), and an EPROM (registered trademark) (Electrically EPROM). Examples thereof include magnetic discs, flexible discs, optical discs, compact discs, mini discs, and DVDs (Digital Versailles Disc).

The memory 302 stores a program that executes all or part of the arithmetic functions of the control unit 3. The processor 300 sends and receives necessary information via the interface 304, and the processor 300 executes a program stored in the memory 302 to perform PWM control on the converter 2a.

Further, the processor 300 and the memory 302 shown in FIG. 15 may be replaced with the processing circuit 303 as shown in FIG. The processing circuit 303 corresponds to a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

The hardware configuration for realizing the arithmetic function in the control unit 3 of the first embodiment has been described above. Here, if there is a margin in the computing power of the processor 300 and the memory 302 or the processing circuit 303 described above, the configuration of the current command value calculating unit 32A shown in FIG. 14 may be changed as shown in FIG. FIG. 17 is a block diagram showing a configuration example different from that of FIG. 14 of the current command value calculation unit according to the first embodiment. In FIG. 17, the same or equivalent components as those in FIG. 14 are indicated by the same reference numerals and symbols.

The current command value calculation unit 32B shown in FIG. 17 further includes a first correction calculation unit 325 in the configuration of FIG. The first correction calculation unit 325 has an effective current command value Ip calculated by the effective current command value calculation unit 320, a coefficient k, and a first invalidity calculated by the first invalid current command value calculation unit 324. The current command value Iq1 is input.

Here, the above equation (11) can be expressed as the following equation by using the first reactive current command value Iq1 represented by the newly defined equation (13).

The first correction calculation unit 325 in FIG. 17 is a calculation unit that executes the calculation shown in the above equation (14). Specifically, the first correction calculation unit 325 has a first reactive current command value Iq1 output from the first reactive current command value calculation unit 324 and a coefficient k which is a proportional coefficient. The first reactive current command correction value Iq1', which is the correction value of the reactive current command value Iq1 of. Then, the current command value calculation unit 32B outputs the first reactive current command correction value Iq1'as the first reactive current command value to the voltage command value calculation unit 34.

The effective current command value Ip and the first reactive current command correction value Iq1'calculated by the current command value calculation unit 32B are input to the voltage command value calculation unit 34 or 35 shown in FIG. 5 or FIG. After that, the AC voltage command value vc * is calculated based on the active current command value Ip and the first reactive current command correction value Iq1', and the switching command sw * is generated based on the AC voltage command value vc *. The operating state of the converter 2a is controlled.

According to the current command value calculation unit 32B, the accuracy when controlling the power factor according to the command value can be further improved as compared with the case where the current command value calculation unit 32A is used.

Embodiment 2.
In the first embodiment, when the control target has a power factor of 1, the magnitude of the reactive current to be output by the current command value calculation unit is clarified. On the other hand, for the purpose of stabilizing the operation of the converter under light load, or for the purpose of stabilizing the power supply voltage in cooperation with the AC power supply, the power factor is controlled to a value other than 1, or the ineffective power is intentionally added. There are cases where it occurs. Even in such a case, how the current command value calculation unit should calculate the reactive current in order to control the power factor or the reactive energy amount as intended by the control unit will be described.

FIG. 18 is a first vector diagram provided for explaining the control method according to the second embodiment. First, as shown in FIG. 18, an axis having the same phase as the sensor acquisition voltage v ^ s is defined as the p-axis, and an axis having a phase advanced by 90 degrees with respect to the p-axis is defined as the q-axis. Next, assuming that the instantaneous current command value is * is in a phase advanced by the power factor angle command value φ with respect to the secondary conversion power supply voltage vs., the instantaneous current command value is * is the p-axis component ip and the q-axis. It decomposes into the component iq3. The amplitude of the p-axis component ip corresponds to the effective current command value Ip of the control unit 3. Further, the amplitude of the q-axis component iq3 is set to Iq3. Further, the phase difference angle, which is the angle formed by the secondary conversion power supply voltage vs. the sensor acquisition voltage v ^ s, is defined as δ. At this time, the amplitude of the q-axis component iq3 is expressed by the following equation.

In the above equation (15), k = xm / | vs | is set as in the first embodiment. Further, in the first embodiment, when deriving the equation (13) from the above equation (11), "xm" expressed by the unit method is defined as "% x", and (% x) ² << 1 is approximated. Was used. This approximation has essentially the same meaning as approximating δ≈0. Therefore, the relationship between the instantaneous current command value is * and the effective current command value Ip is expressed by the following equation.

Then, by substituting the above equation (16) into the above equation (15), the following equation is obtained.

Here, the desired reactive current is defined as the second reactive current command value Iq2. Further, the alternating current is is controlled so as to match the instantaneous current command value is *. Therefore, the component of the instantaneous current command value is * that is orthogonal to the secondary conversion power supply voltage vs. is sufficient to match the second reactive current command value Iq2.

Further, of the instantaneous current command value is *, the component having the same phase as the secondary conversion power supply voltage vs. corresponds to the magnitude of the actual effective current, but when δ ≈ 0, the component having the same phase is the effective current command. Can be considered equal to the value Ip. At this time, tan φ = Iq2 / Ip and 1 / cos ² φ = 1 + (Iq2 / Ip) ² . Therefore, the above equation (17) can be modified as the following equation.

The second term on the right side of the above equation (18) is equal to the first reactive current command value Iq1 described in the first embodiment. Further, if the third term on the right side of the above equation (18) is defined as the second reactive current command correction value Iq2', the above equation (18) can be expressed by the following equation.

Therefore, if the voltage command calculation unit calculates the AC voltage command based on the reactive current command value Iq3 calculated by the above equation (19), the desired reactive current can be obtained even under the condition that the phase difference angle δ exists. Can be achieved. The configuration of the current command value calculation unit that achieves this function is as shown in FIG. 19, for example. FIG. 19 is a block diagram showing a configuration example of the current command value calculation unit according to the second embodiment. In FIG. 19, the same or equivalent components as those in FIG. 14 are indicated by the same reference numerals and symbols.

The current command value calculation unit 32C shown in FIG. 19 further includes a second reactive current command value calculation unit 326 and a second correction calculation unit 327 in the configuration of FIG. In FIG. 19, the second reactive current command value calculation unit 326 has the second reactive current command value Iq2 for the purpose of stabilizing the operation of the converter at the time of light load or stabilizing the power supply voltage in cooperation with the AC power supply. Is calculated. The second correction calculation unit 327 corrects the second reactive current command, which is proportional to the square of the second reactive current command value Iq2, based on the second reactive current command value Iq2 and the coefficient k which is a proportional coefficient. Calculate the value Iq2'. Then, the second reactive current command value Iq2 and the second reactive current command correction value Iq2'are added by the adder 328. Further, the adder 329 adds the first reactive current command value Iq1, and the output after the addition is output to the voltage command value calculation unit 34 as the reactive current command value Iq3.

In FIG. 19, the sum of the second reactive current command value Iq2 and the second reactive current command correction value Iq2'is further added to the first reactive current command value Iq1 by the adder 329 to obtain a voltage. It is output to the command value calculation unit 34. Instead of this configuration, each output may be individually output to the voltage command value calculation unit 34. In this case, the sum of the second reactive current command value Iq2, the second reactive current command correction value Iq2', and the first reactive current command value Iq1 are added inside the voltage command value calculation unit 34. Needless to say, it becomes the reactive current command value.

FIG. 20 is a block diagram showing a configuration example different from that of FIG. 19 of the current command value calculation unit according to the second embodiment. In FIG. 20, the same or equivalent components as those in FIG. 17 are indicated by the same reference numerals and symbols. The current command value calculation unit 32D shown in FIG. 20 is a configuration example in the case where the calculation capacity of the control unit 3 has a margin, as in the first embodiment. The configuration of FIG. 20 is a configuration in which the first reactive current command correction value Iq1 ′ represented by the above equation (14) is used instead of the first reactive current command value Iq1 in the above equation (19). With the configuration of FIG. 20, the accuracy of controlling the reactive current to a desired value can be further improved.

The degree of freedom of the three variables of power factor, active current, and reactive current is 2, and when any two variables are determined, the remaining one variable is automatically determined. Since the active current is an operation amount for controlling the DC voltage to be constant, the remaining degrees of freedom are either reactive current or power factor. Therefore, the second invalid current command value calculation unit calculates the second invalid current command value Iq2 based on the command value of the power factor or power factor angle (not shown) and the effective current command value Ip. You may.

As described above, according to the second embodiment, the current command value calculation unit provided in the control unit calculates the second invalid current command value and uses the above-mentioned coefficient k as a proportional coefficient to obtain the second invalid current command value. The second invalid current command correction value proportional to the square of the invalid current command value of is calculated. Further, the current command value calculation unit inputs the second reactive current command value and the second reactive current command correction value to the voltage command value calculation unit together with the first reactive current command value described in the first embodiment. Output. Then, the voltage command value calculation unit has the reference phase calculated from the acquired value of the second voltage sensor, the active current command value, the first reactive current command value, the second reactive current command value, and the second. The AC voltage command value is calculated based on the reactive current command correction value of 2. As a result, the effect of the first embodiment can be obtained, a desired reactive current can be achieved even under the condition where a phase difference angle exists, and the power factor or the amount of reactive power is intended by the control unit. It can be controlled as it is.

Embodiment 3.
In the third embodiment, a case where the number of power conversion devices is a plurality of units will be described. As described above, since the power converter and the secondary winding of the transformer have a one-to-one connection relationship, for example, when the number of power converters is two, the secondary winding of the transformer There are also two lines.

FIG. 21 is a block diagram showing a configuration example of a main part of the power conversion system according to the third embodiment. FIG. 21 shows a configuration in which two power converters 10a and 10b are connected to the secondary winding 1b of the transformer 1A via a switch 12 as an example of a plurality of power converters. ing. The role of the switch 12 will be described later.

In an electric vehicle, as shown in FIG. 1, a load 120 including an inverter 120a is connected to the DC side of the converter 2a. The inverter 120a drives the motor 120b to apply a driving force to the electric vehicle. When the driving force required for the entire electric vehicle is shared by the plurality of inverters 120a, or when the power capacity per inverter 120a is large, as shown in FIG. 21, the plurality of power conversion devices 10a, The configuration is such that 10b is connected to the secondary winding 1b of the transformer 1A. If the power capacities of the devices are the same, the same device can be used, so in many cases, the rated power of each power converter is the same. Further, if the configuration is such that power is supplied to a plurality of power converters 10a and 10b via one transformer 1A as shown in FIG. 21, the power converter and the transformer are mounted on a one-to-one basis. The volume of the entire transformer can be reduced rather than the volume of the transformer.

FIG. 22 is a diagram showing an equivalent circuit in which the transformer shown in FIG. 21 is represented by using an ideal transformer and a coupling inductance. In FIG. 22, the transformer 1A shown in FIG. 21 is represented by an ideal transformer 72 and a coupling inductance 76.

In FIG. 22, “v1” is the primary voltage, “v2a” is the first group secondary voltage, “v2b” is the second group secondary voltage, “v3” is the tertiary voltage, “i1” is the primary current, and “i2a” is 1. The group secondary current, "i2b" represents the second group secondary current, and "i3" represents the tertiary current. The meanings of the other symbols are the same as those in FIG.

Here, in the equivalent circuit of FIG. 22, the circuit equations of the following equation and the following equation are established.

Compared with the circuit equation by the equivalent circuit of FIG. 8, the order of the reactance matrix is increased by 1 to 3 as the number of secondary windings is increased. By expanding the third line of the above equation (21), the following equation is obtained.

As described above, in the basic configuration shown in FIG. 5 or 7, the active current and the reactive current are controlled with reference to the reference phase θ, respectively. However, as shown in the second term on the right side of the above equation (22), the tertiary voltage v3 acquired by the voltage sensor 6 may have a different phase with respect to the primary voltage v1. As a result, there may be a problem that the power factor of the AC power or the amount of invalid power seen on the primary side of the transformer 1A does not become as instructed by the control unit 3. Therefore, the method of the third embodiment that solves this problem by correcting the instantaneous current command value is * will be described below.

First, the above equation (22) is modified as the following equation.

Here, in the configuration of FIG. 21, since the load of the tertiary winding 1c is only the voltage sensor 6, the tertiary current i3 = 0. In the case of an electric vehicle, another load such as an auxiliary power supply device may be connected to the tertiary winding 1c, but in most cases, the power capacity is smaller than that of the converter of the secondary winding. Therefore, ignoring the tertiary current i3 and setting the tertiary current i3 = 0 is a reasonable and reasonable assumption.

Further, the left side of the above equation (23) is a value obtained by secondary conversion of the primary voltage v1 and is equal to the secondary conversion power supply voltage vs. Further, the first term on the right side is a value obtained by quadratic conversion of the acquired value of the voltage sensor 6, and is equal to the sensor acquired voltage v ^ s. Since each converter generally has the same rated power as described above, it is assumed that the first group secondary current i2a and the second group secondary current i2b in the transformer 1A are equal. Further, each secondary current of the transformer 1A is equal to the alternating current is of each converter, and the alternating current is controlled by the instantaneous current command value is *, so i2a = i2b = is *. Further, if the proportional coefficient of the second term on the right side is xm'= (n2 / n3) (x3a + x3b), the following equation is obtained.

Comparing the above equation (24) with the above equation (9), in the above equation (24), the proportional coefficient of the second term on the right side is only changed from "xm" to "xm'". Therefore, if k = xm'/ | vs |, the reactive current command value Iq to be output by the current command value calculation unit is any of the following.

Next, the role of the switch 12 shown in FIG. 21 will be described. An electric vehicle power conversion system configured as shown in FIG. 21 may open the switch 12 to shut down one or more power conversion devices 10 under certain conditions. Here, the specific condition includes, for example, when a problem occurs in the operation of the power conversion device. In addition, since it is advantageous in terms of power efficiency, when the required propulsive force is small, only a small number of power conversion devices may be operated.

As an example, consider the case where the power conversion device 10b of the second group is stopped and disconnected by the switch 12 in the configurations of FIGS. 21 and 22. At this time, since i2b = 0, the above equation (23) is expressed by the following equation.

Further, as in the case of the first embodiment, i3 = 0, i2a = is *, xm "= (n2 / n3) x3a, k" = xm "/ | vs |. At this time, the current command value calculation is performed. The reactive current command value Iq to be output by the unit is one of the following.

In the above equations (28) and (29), the coefficient k is only changed to "k" as compared with the above equations (13) and (14), that is, the operation or stop of the power conversion device. When the state of is changed, the current command value calculation unit calculates the invalid current according to the equation (13) or the equation (14) as in the first embodiment, and it can be seen that only the coefficient k needs to be changed.

As an example, when the reactance matrix is defined as in the above equation (21), the coefficient k according to the operating or stopped state of the power conversion device 10a of the first group and the power conversion device 10b of the second group is It can be expressed as shown in the following table.

Further, the configuration of the current command value calculation unit that achieves the above functions is as shown in FIG. 23, for example. FIG. 23 is a block diagram showing a configuration example of the current command value calculation unit according to the third embodiment. In FIG. 23, the same or equivalent components as those in FIG. 14 are indicated by the same reference numerals and symbols.

The current command value calculation unit 32E shown in FIG. 23 further includes a coefficient calculation unit 330 in the configuration of FIG. Further, the coefficient calculation unit 330 includes a first constant selector 3301 and a divider 3302.

In FIG. 23, the operating state information of the power conversion device is input to the first constant selector 3301. Then, in the first constant selector 3301, the first constant xm is selected from the list held in advance according to the operating state of the power conversion device. Then, in the divider 3302, the first constant xm is divided by the rated value of the amplitude of the secondary conversion power supply voltage vs. The output of the divider 3302 is output to the first reactive current command value calculation unit 324 as a coefficient k. Instead of omitting the divider 3302, the first constant xm divided in advance by the rated value of the amplitude of the secondary conversion power supply voltage vs. may be stored in the list. Subsequent operations are as described above.

The coefficient calculation unit 330 may be a component of the first reactive current command value calculation unit 324. Further, the coefficient calculation unit 330 may be configured to be included in a higher-level control system (not shown), and the coefficient k determined according to the operating state of the power conversion device may be input to the current command value calculation unit. Good.

Further, in the above description, the method of switching the coefficient k used in the first reactive current command value calculation unit 324 according to the operating or stopped state of the power conversion device has been described in the example of applying to the first embodiment. Needless to say, the same method can be applied to the second embodiment.

As described above, according to the third embodiment, the control unit changes the first coefficient according to the operating or stopped state of the plurality of power conversion devices. As a result, even if the tertiary voltage acquired by the second voltage sensor has a different phase with respect to the primary voltage, the power factor of the AC power or the amount of reactive power seen on the primary side of the transformer is as instructed by the control unit. Can be controlled to.

Embodiment 4.
In the current command value calculation unit of the first to third embodiments, the coefficient k is determined based on the off-diagonal term of the reactance matrix and the amplitude of the quadratic conversion power supply voltage vs. It has been described in the third embodiment that it is desirable that the portion of these elements derived from the off-diagonal terms of the reactance matrix is variable according to the operating state of the power conversion device. On the other hand, the amplitude of the secondary conversion power supply voltage vs. also may fluctuate depending on the load state or time. In the vector diagrams of FIGS. 11, 13 and 18, the voltage drop at the reactance xm is smaller than the secondary conversion power supply voltage vs. the sensor acquisition voltage v ^ s. Therefore, the amplitude of the sensor acquisition voltage v ^ s may be treated as the amplitude of the secondary conversion power supply voltage vs. Therefore, by calculating the amplitude of the sensor acquisition voltage v ^ s and adjusting the coefficient k used in the current command value calculation unit according to the value, the power factor seen on the primary side of the transformer 1A can be controlled more accurately. It can be controlled as instructed in Part 3.

The configuration of the current command value calculation unit that achieves the above functions is as shown in FIG. 24, for example. FIG. 24 is a block diagram showing a configuration example of the current command value calculation unit according to the fourth embodiment. In FIG. 24, the same or equivalent components as those in FIG. 23 are indicated by the same reference numerals and symbols.

The current command value calculation unit 32F shown in FIG. 24 further includes an amplitude calculation unit 3303 in the coefficient calculation unit 330A in the configuration of FIG. 23. The amplitude calculation unit 3303 calculates the amplitude of the sensor acquisition voltage v ^ s. As a method for calculating the amplitude from an AC signal, a known method shall be used, and the description thereof will be omitted here. Then, the coefficient k is obtained by dividing the first constant xm by the output of the amplitude calculation unit 3303, and outputs the coefficient k to the first reactive current command value calculation unit 324. That is, in the fourth embodiment, the value of the coefficient k is changed so as to be inversely proportional to the output of the amplitude calculation unit 3303.

As in FIG. 23, the coefficient calculation unit 330A may be a component of the first reactive current command value calculation unit 324, or may be included in a higher-level control system (not shown). Further, in the above, the method of changing the value of the coefficient k used in the current command value calculation unit according to the amplitude of the sensor acquisition voltage v ^ s has been described in the example of applying to the third embodiment, but the same method can be used. Needless to say, it can be applied to the first embodiment and the second embodiment.

As described above, according to the fourth embodiment, a signal proportional to the amplitude of the output of the first voltage sensor is calculated, and the value of the first coefficient is changed so as to be inversely proportional to the calculated output. As a result, the power factor seen on the primary side of the transformer can be more accurately obtained while having the effect of the third embodiment and even when the amplitude of the secondary conversion power supply voltage fluctuates depending on the load state or time. It can be controlled as instructed by the control unit.

The configuration shown in the above-described embodiment shows an example of the content of the present invention, can be combined with another known technique, and is configured without departing from the gist of the present invention. It is also possible to omit or change a part of.

1,1A transformer, 1a primary winding, 1b secondary winding, 1c tertiary winding, 2a converter, 2b capacitor, 3 control unit, 4 current sensor, 5,6 voltage sensor, 10,10a, 10b power converter , 12 switch, 30 phase calculation unit, 32, 32A, 32B, 32C, 32D, 32E, 32F current command value calculation unit, 34, 35 voltage command value calculation unit, 36 switching command generation unit, 50 power conversion system, 60 Propulsion controller, 70,72 ideal transformer, 74,76 coupling inductance, 100 electric vehicle drive system, 106 power supply equipment, 108 power lines, 110 voltage system, 120 load, 120a inverter, 120b motor, 300 processor, 302 memory, 303 processing circuit, 304 interface, 320 effective current command value calculation unit, 321, 346,352,353 subtractor, 322 voltage control unit, 323,343,344 adder, 324 first invalid current command value calculation unit, 325 1st correction calculation unit, 326 2nd invalid current command value calculation unit, 327 2nd correction calculation unit, 328, 329, 345 adder, 330, 330A coefficient calculation unit, 336 positive contact value calculation unit, 341 sinusoidal value Calculation unit, 342 Cosine value calculation unit, 347,354,355 Current control unit, 351 Rotational coordinate conversion unit, 356 Static coordinate conversion unit, 3301 First constant selector, 3302 Divider, 3303 Fluctuation calculation unit.

Claims (6)

At least one power conversion including a converter that converts AC power into DC power, a first voltage sensor that acquires a DC voltage generated on the DC side of the converter, and a control unit that controls the operating state of the converter. A primary winding connected to the device and an AC power supply, at least one secondary winding each connected to each of the power converters on a one-to-one basis, and a tertiary winding to which a second voltage sensor is connected. A power conversion system with a transformer, with a wire,
The control unit
A phase calculation unit that calculates a reference phase from the acquired value of the second voltage sensor, and
An effective current command value calculation unit that calculates an effective current command value based on the deviation between the DC voltage command value and the DC voltage acquired by the first voltage sensor.
The first coefficient determined by the coupling inductance of the transformer and the received voltage of the transformer is used as a proportional coefficient, and the first invalid current command value proportional to the square of the active current command value is used using the proportional coefficient. The first invalid current command value calculation unit that calculates
A voltage command value calculation unit that calculates an AC voltage command value based on the reference phase, the active current command value, and the first reactive current command value.
A power conversion system characterized by being equipped with. The control unit
Based on the active current command value Ip, the first reactive current command value Iq1, and the first coefficient k, the first reactive current command correction value Iq1'is calculated using the following equation (1). Equipped with a first correction calculation unit
The power conversion system according to claim 1, wherein the first reactive current command correction value is output to the voltage command value calculation unit as the first reactive current command value.

The control unit
A second reactive current command calculation unit that calculates a second reactive current command value, and
A second correction value calculation unit that uses the first coefficient as a proportional coefficient and calculates a second invalid current command correction value proportional to the square of the second invalid current command value using the proportional coefficient.
With
The claim is characterized in that the second reactive current command value and the second reactive current command correction value are added to the first reactive current command value and output to the voltage command value calculation unit. The power conversion system according to 1 or 2. The power according to claim 3, wherein the second reactive current command calculation unit calculates the second reactive current command value based on the power factor angle command value and the active current command value. Conversion system. The number of the power converter and the secondary winding is plural, and there are a plurality of them.
The power according to any one of claims 1 to 4, wherein the control unit changes the value of the first coefficient according to the operating or stopped state of the plurality of power conversion devices. Conversion system. The control unit
It is provided with an amplitude calculation unit that calculates a signal proportional to the amplitude of the output of the second voltage sensor.
The power conversion system according to any one of claims 1 to 5, wherein the value of the first coefficient is changed so as to be inversely proportional to the output of the amplitude calculation unit.

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