JP7117818B2 - power converter - Google Patents

Description

TECHNICAL FIELD Embodiments of the present invention relate to power converters.

A power conversion device is known that includes a main circuit section that performs at least one of conversion from AC power to DC power and conversion from DC power to AC power, and a control device that controls the operation of the main circuit section. . In such a power conversion device, a control device is configured with a standby dual system. That is, two control devices, an operating control device and a standby control device, are provided so that when an abnormality occurs in the operating control device, the control device is switched to the standby control device. Thereby, more stable operation can be obtained in the power converter.

Further, when configuring the control device in a standby duplex system, it is also being considered to configure the standby control device as a hot standby configuration. In the hot standby configuration, the control device of the operation system and the control device of the standby system send a control signal for controlling the operation of the main circuit unit and a selection signal for selecting the control signal for the operation system to the main circuit. section to select the control signal on the main circuit section side. As a result, when an abnormality or the like occurs in the operating system control device, it is possible to immediately switch to the standby system control device, and the operation of the power conversion device can be further stabilized.

When the standby system controller is configured to have a hot standby configuration, the operating system controller and the operating system controller synchronize carrier waveforms for generating control signals and matching the control amount. Make the control signals nearly identical.

However, due to individual differences in circuits that generate control signals, transmission delays of control signals, and the like, the control signals of the operating system and the standby system do not match perfectly, and an error occurs. Due to this error, if switching between the control signal for the operating system and the control signal for the standby system is instantaneously performed, unnecessary jitter pulses may be generated and unnecessary switching may be performed. Therefore, when switching between the control signal for the operating system and the control signal for the standby system, it is necessary to temporarily stop the operation of the main circuit unit. On the other hand, if the operation of the main circuit unit is stopped for switching between the operating system and the standby system, disturbance will occur in the output of the main circuit unit.

Therefore, in the power conversion device, it is desirable to be able to suppress the stoppage of the operation of the main circuit unit even when switching between the control signal for the operating system and the control signal for the standby system.

JP 2011-24287 A

An embodiment of the present invention provides a power conversion device that can suppress the stoppage of the operation of the main circuit unit even when switching between an operation-system control signal and a standby-system control signal.

According to an embodiment of the present invention, a plurality of switching elements are provided, and at least one of AC power to DC power conversion and DC power to AC power conversion is performed by turning on/off the plurality of switching elements. A main circuit unit that performs conversion, a first controller that controls operation of the main circuit unit, and a second controller that controls operation of the main circuit unit, wherein the first controller and the second controller are provided. The control device has one operating system for actually controlling the operation of the main circuit unit and the other operating system as a backup standby system for the operating system, and is capable of switching between the operating system and the standby system. a first control device for transmitting a first control signal for controlling the operation of the main circuit unit and a first selection signal for identifying the operating system and the standby system to the main circuit unit; The second control device transmits to the main circuit unit a second control signal for controlling the operation of the main circuit unit and a second selection signal for identifying the operating system and the standby system. , the main circuit unit selects a control signal for the operation system from the first control signal and the second control signal based on the first selection signal and the second selection signal, A control circuit for controlling on/off of the plurality of switching elements based on the control signal, wherein the first selection signal and the second selection signal are an operating state indicating the operating system; and a standby state indicating a standby system, wherein the first control device and the second control device receive the first selection signal and the second control device when switching between the operation system and the standby system. An overlap period is provided in which both of the selection signals are in the operating state, and the control circuit controls the operating state when the first control signal and the second control signal are in the same state during the overlap period. A power converter is provided that switches between a system and the standby system.

Provided is a power converter that can suppress the stoppage of the operation of the main circuit unit even when switching between the control signal for the operating system and the control signal for the standby system.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which represents typically the power converter device which concerns on embodiment. 1 is a block diagram schematically representing a converter; FIG. It is a block diagram which represents a 1st control apparatus and a 2nd control apparatus typically. 4 is a graph diagram schematically showing an example of the operation of a control signal generator; FIG. It is a timing chart which expresses an example of operation of a power converter typically. It is a timing chart which represents typically the reference example of operation|movement of a power converter device. FIG. 11 is a block diagram schematically showing a modified example of the converter;

Each embodiment will be described below with reference to the drawings.
Note that the drawings are schematic or conceptual, and the relationship between the thickness and width of each portion, the size ratio between portions, and the like are not necessarily the same as the actual ones. Also, even when the same parts are shown, the dimensions and ratios may be different depending on the drawing.
In addition, in the present specification and each figure, the same reference numerals are given to the same elements as those described above with respect to the already-appearing figures, and detailed description thereof will be omitted as appropriate.

FIG. 1 is a block diagram schematically showing a power conversion device according to an embodiment.
As shown in FIG. 1, the power conversion device 10 includes a first control device 11, a second control device 12, and a main circuit section . The power conversion device 10 is used, for example, in a DC power transmission system. The power converter 10 is connected to an AC power system 2 (AC circuit) and a pair of DC transmission lines 3 and 4 (DC circuit) in a DC power transmission system.

The DC power transmission system has a transformer 6, for example. A main circuit unit 14 of the power converter 10 is connected to the AC power system 2 via a transformer 6 . The transformer 6 converts the AC power of the AC power system 2 into AC power corresponding to the main circuit section 14 . The transformer 6 changes the effective value of AC power according to the main circuit section 14 . The transformer 6 is provided as required and can be omitted. The AC power of the AC power system 2 may be directly supplied to the main circuit unit 14 .

The power converter 10 converts AC power supplied from the AC power system 2 into DC power, and supplies the converted DC power to the DC transmission lines 3 and 4 . The power conversion device 10 also converts the DC power supplied from the DC transmission lines 3 and 4 into AC power, and supplies the converted AC power to the AC power system 2 . Thus, the power converter 10 performs AC-DC conversion from AC to DC and AC-DC conversion from DC to AC.

The AC power of the AC power system 2 is, for example, three-phase AC power. The power converter 10 performs, for example, conversion from three-phase AC power to DC power and conversion from DC power to three-phase AC power. The AC power of the AC power system 2 may be single-phase AC power or the like.

For example, the DC transmission line 3 is a transmission line on the high voltage side of DC power, and the DC transmission line 4 is a transmission line on the low voltage side of DC power. The power conversion device 10 outputs converted DC power to the DC transmission lines 3 and 4 so that the DC transmission line 3 side has a high voltage and the DC transmission line 4 side has a low voltage.

The power conversion device 10 is not limited to a DC power transmission system, and may be applied to any other system that requires AC-to-DC conversion and DC-to-AC conversion. The AC/DC conversion by the power converter 10 is not limited to both AC to DC and DC to AC, but may be AC to DC or DC to AC. The power conversion device 10 may be capable of performing AC/DC conversion of at least one of AC to DC and DC to AC. Also, in this example, the AC power system 2 is shown as an AC circuit, and the DC transmission lines 3 and 4 are shown as DC circuits. The AC circuit may be, for example, an AC load, an AC power source, or the like. The DC circuit may be, for example, a DC load, a DC power source, or the like.

The main circuit unit 14 is provided between the AC power system 2 and the DC transmission lines 3 and 4 . The main circuit unit 14 converts AC power to DC power and converts DC power to AC power. The main circuit unit 14 is, for example, an MMC (Modular Multilevel Converter) type power converter. The MMC type main circuit section 14 has a plurality of converters connected in series. Each converter has a plurality of half-bridge or full-bridge connected switching elements and a charge storage element connected in parallel to each switching element. The main circuit unit 14 performs AC/DC conversion by switching each switching element.

The first control device 11 and the second control device 12 are connected to the main circuit section 14 . The first control device 11 and the second control device 12 control the on/off of each switching element so that the main circuit unit 14 converts AC power to DC power and converts DC power to AC power. to control.

In this manner, the power conversion device 10 controls the operation of the main circuit section 14 using either the first control device 11 or the second control device 12 . That is, the power conversion device 10 has a redundant configuration of the first control device 11 and the second control device 12 .

In the power conversion device 10, one of the first control device 11 and the second control device 12 is used as an operating control device, and the other is used as a standby control device. The operating system control device is a control device that actually controls the operation of the main circuit unit 14 . The standby system control device is a backup control device that controls the operation of the main circuit unit 14 in place of the operation system control device at the time of failure or maintenance of the operation system control device. The power conversion device 10 switches between the operating system and the standby system of the first control device 11 and the second control device 12 according to failure, maintenance, or the like. That is, when the first control device 11 is the driving system, the second control device 12 is the standby system, and when the second control device 12 is the driving system, the first control device 11 is the standby system. As a result, even if one of the first control device 11 and the second control device 12 fails, the other can be used to continue the operation of the main circuit unit 14, and the reliability of the power conversion device 10 can be improved. can be improved.

Further, in the power conversion device 10, for example, even while the operating control device is operating normally, the standby control device is operated in synchronization with the operating control device. The first control device 11 and the second control device 12 each input a control signal to the main circuit section 14 . The main circuit unit 14 operates based on a control signal from the operating control device of the first control device 11 and the second control device 12 . That is, in the first control device 11 and the second control device 12, the standby control device operates in so-called hot standby. As a result, when a failure or the like occurs in the operating system control device, it is possible to immediately switch to the standby system control device. It is possible to suppress the stoppage of the operation of the main circuit unit 14 at the time of switching from the operating system control device to the standby system control device, and to obtain more stable operation in the power conversion device 10.

The first control device 11 and the second control device 12, for example, communicate with a higher-level controller via a network or the like, and control the operation of the main circuit unit 14 based on command values or the like input from the higher-level controller. . In addition, the first control device 11 and the second control device 12, for example, communicate with each other, synchronize the operation of the standby control device with the operation of the operating control device, and check the operation status of each other. . Communication between the first control device 11 and the second control device 12 may be wired or wireless.

The main circuit portion 14 includes first and second pairs of DC terminals 20a and 20b, first to third three AC terminals 21a to 21c, and first to sixth six arm portions 22a to 22f. , has

The first DC terminal 20a is connected to the DC transmission line 3 on the high voltage side. The second DC terminal 20b is connected to the DC transmission line 4 on the low voltage side. As a result, the DC power converted by the main circuit section 14 is supplied to the DC transmission lines 3 and 4 and the DC power supplied from the DC transmission lines 3 and 4 is input to the main circuit section 14 .

The first arm portion 22a is connected to the first DC terminal 20a. The second arm portion 22b is connected between the first arm portion 22a and the second DC terminal 20b. The first arm portion 22a and the second arm portion 22b are connected in series between the DC terminals 20a and 20b.

The third arm portion 22c is connected to the first DC terminal 20a. The fourth arm portion 22d is connected between the third arm portion 22c and the second DC terminal 20b. The third arm portion 22c and the fourth arm portion 22d are connected in parallel to the first arm portion 22a and the second arm portion 22b.

The fifth arm portion 22e is connected to the first DC terminal 20a. The sixth arm portion 22f is connected between the fifth arm portion 22e and the second DC terminal 20b. That is, the fifth arm portion 22e and the sixth arm portion 22f are connected in parallel to the first arm portion 22a and the second arm portion 22b, and the third arm portion 22c and the fourth arm portion 22d. connected in parallel.

In the main circuit section 14, the first leg LG1 is configured by the first arm section 22a and the second arm section 22b, the second leg LG2 is configured by the third arm section 22c and the fourth arm section 22d, and the fifth arm section. 3rd leg LG3 is comprised by 22e and the 6th arm part 22f. That is, in this example, the main circuit section 14 is a 3-leg, 6-arm three-phase inverter. The first arm portion 22a, the third arm portion 22c and the fifth arm portion 22e are upper arms. The second arm portion 22b, the fourth arm portion 22d and the sixth arm portion 22f are lower arms.

The first arm portion 22a has a plurality of converters UP1, UP2 . . . _UPM1 connected in series. The _second arm portion 22b has a plurality of transducers UN1, UN2 . . . UNM2 connected in series. The _third arm portion 22c has a plurality of converters VP1, VP2 . . . VPM3 connected in series. The _fourth arm portion 22d has a plurality of converters VN1, VN2 . . . VNM4 connected in series. The fifth arm portion 22e has a plurality of transducers WP1, WP2 . . . WPM ₅ connected in series. The sixth arm portion 22f has a plurality of transducers WN1, WN2 . . . WNM ₆ connected in series.

However, hereinafter, each converter UP1, UP2... _UPM1 , UN1, UN2... _UNM2 , VP1, VP2... _VPM3 , VN1, VN2... _VNM4 , WP1, WP2... _WPM5 , WN1, WN2... _WNM6 When collectively referred to, they are referred to as "converter CEL".

In each arm 22a-22f, M ₁ , M ₂ , M ₃ , M ₄ , M ₅ , M ₆ represent the number of converters CEL connected in series. In each of the arms 22a-22f, the number of converters CEL connected in series is, for example, about 100-120. However, the number of converters CEL connected in series is not limited to this, and may be any number.

The number of transducers CEL provided in each arm portion 22a-22f is substantially the same. For example, when a large number of converters CEL are connected, the number of converters CEL provided in each arm section 22a to 22f may be different as long as the operation of the main circuit section 14 is not affected. For example, when 100 transducers CEL are connected in series to one arm, the number of transducers CEL provided to another arm may differ by one or two.

Each arm portion 22a-22f further has a buffer reactor 23a-23f and a plurality of current detectors 24a-24f. Moreover, the power conversion device 10 further has a voltage detector 25 .

Each buffer reactor 23a-23f is connected in series with each converter CEL in each arm part 22a-22f. The buffer reactor 23a of the first arm portion 22a is provided between the connection point between the AC terminal 21a, the first arm portion 22a and the second arm portion 22b, and the converter UP1. The buffer reactor 23b of the second arm portion 22b is provided between the connection point between the AC terminal 21a, the first arm portion 22a and the second arm portion 22b, and the converter UN1. The buffer reactor 23c of the third arm portion 22c is provided between the connection point between the AC terminal 21b, the third arm portion 22c and the fourth arm portion 22d, and the converter VP1. The buffer reactor 23d of the fourth arm portion 22d is provided between the connection point between the AC terminal 21b, the third arm portion 22c and the fourth arm portion 22d, and the converter VN1. The buffer reactor 23e of the fifth arm portion 22e is provided between the connection point between the AC terminal 21c, the fifth arm portion 22e and the sixth arm portion 22f, and the converter WP1. The buffer reactor 23f of the sixth arm portion 22f is provided between the connection point between the AC terminal 21c, the fifth arm portion 22e and the sixth arm portion 22f, and the converter WN1.

The current detector 24a is provided on the first arm portion 22a and detects the current flowing through the first arm portion 22a. That is, the current detector 24a detects the arm current of the first arm portion 22a. The current detector 24a is connected to the first control device 11 and the second control device 12 via wiring (not shown) or the like. The current detector 24 a inputs the detected current value _Ia1 of the first arm portion 22 a to the first control device 11 and the second control device 12 . As a result, the current value _Ia1 of the first arm portion 22a is input to the first control device 11 and the second control device 12 .

Similarly, the current detector 24b detects the current flowing through the second arm portion 22b and inputs the detected current value _Ia2 to the first control device 11 and the second control device 12. FIG. The current detector 24 c detects the current flowing through the third arm portion 22 c and inputs the detected current value _Ia3 to the first controller 11 and the second controller 12 . The current detector 24 d detects the current flowing through the fourth arm portion 22 d and inputs the detected current value _Ia4 to the first controller 11 and the second controller 12 . The current detector 24e detects the current flowing through the fifth arm portion 22e and inputs the detected current value _Ia5 to the first control device 11 and the second control device 12 . The current detector 24f detects the current flowing through the sixth arm portion 22f and inputs the detected current value _Ia6 to the first control device 11 and the second control device 12 .

The voltage detector 25 detects the AC voltage (phase voltage) of each phase of the AC power system 2 and inputs the detected value to the first control device 11 and the second control device 12 . The voltage detector 25 may be connected to the primary side of the transformer 6 or may be connected to the secondary side. Here, the three phases of the AC power system 2 are assumed to be U-phase, V-phase, and W-phase, respectively. The voltage detector 25 detects the voltage value Vu of the U-phase AC voltage and inputs it to the first control device 11 and the second control device 12, and detects the voltage value Vv of the V-phase AC voltage to perform the first control. It is input to the device 11 and the second control device 12 , and the voltage value Vw of the W-phase AC voltage is detected and input to the first control device 11 and the second control device 12 .

In the main circuit portion 14, a connection point between the first arm portion 22a and the second arm portion 22b, a connection point between the third arm portion 22c and the fourth arm portion 22d, and a connection point between the fifth arm portion 22e and the sixth arm portion 22f becomes an AC output point.

The first AC terminal 21a is connected to a connection point between the first arm portion 22a and the second arm portion 22b. The second AC terminal 21b is connected to a connection point between the third arm portion 22c and the fourth arm portion 22d. The third AC terminal 21c is connected to a connection point between the fifth arm portion 22e and the sixth arm portion 22f. Each AC terminal 21a-21c is connected to a transformer 6, for example.

Each converter CEL is connected to the first controller 11 via a signal line 26 . Each converter CEL is also connected to the second controller 12 via a signal line 27 . The first control device 11 controls the operation of the converter CEL by inputting a control signal to the converter CEL via the signal line 26 . The second control device 12 controls the operation of the converter CEL by inputting control signals to the converter CEL via the signal line 27 .

FIG. 2 is a block diagram schematically representing a converter.
As shown in FIG. 2, the converter CEL includes a first connection terminal 30a, a second connection terminal 30b, a first switching element 31, a second switching element 32, a charge storage element 35, and a control circuit 40. , and drive circuits 41 and 42 .

Each switching element 31, 32 includes a pair of main terminals and a control terminal. A control terminal controls the current flowing between the pair of main terminals. Self-extinguishing elements such as IGBTs are used for the switching elements 31 and 32, for example. A pair of main terminals are, for example, an emitter and a collector, and a control terminal is, for example, a gate. For example, a normally-off semiconductor element is used for each of the switching elements 31 and 32 .

A pair of main terminals of the second switching element 32 are connected in series with a pair of main terminals of the first switching element 31 . The charge storage element 35 is connected in parallel with the first switching element 31 and the second switching element 32 . The charge storage element 35 is, for example, a capacitor. The first connection terminal 30 a is connected between the first switching element 31 and the second switching element 32 . The second connection terminal 30 b is connected to the main terminal of the first switching element 31 opposite to the main terminal connected to the second switching element 32 .

A rectifying element 31d is connected to the first switching element 31 in anti-parallel with respect to the pair of main terminals. The forward direction of the rectifying element 31 d is opposite to the direction of the current flowing between the pair of main terminals of the first switching element 31 . Similarly, in the second switching element 32, a rectifying element 32d is connected in anti-parallel with respect to the pair of main terminals. The rectifying elements 31d and 32d are so-called freewheeling diodes.

Power is supplied to the converter CEL via respective connection terminals 30a, 30b. In the converter CEL, each switching element 31, 32 is half-bridge connected. In other words, the converter CEL is a bidirectional chopper. The first switching element 31 is a so-called low-side switch, and the second switching element 32 is a so-called high-side switch.

A control terminal of the first switching element 31 is connected to the driving circuit 41 . A control terminal of the second switching element 32 is connected to the drive circuit 42 . The drive circuits 41 and 42 are connected to the control circuit 40 . The control circuit 40 inputs control signals to the driving circuits 41 and 42 . The drive circuit 41 switches ON/OFF of the first switching element 31 based on the control signal input from the control circuit 40 . Similarly, the drive circuit 42 switches ON/OFF of the second switching element 32 based on the control signal input from the control circuit 40 .

The control circuit 40 is connected to the first control device 11 via the signal line 26 . The first control device 11 inputs a first control signal and a first selection signal to the control circuit 40 of the converter CEL. The first control signal is a signal for controlling ON/OFF switching of the first switching element 31 and the second switching element 32 . The first selection signal is a signal for identifying whether the first control device 11 is an operating system or a standby system.

Also, the control circuit 40 is connected to the second control device 12 via the signal line 27 . The second controller 12 inputs a second control signal and a second selection signal to the control circuit 40 of the converter CEL. The second control signal is a signal similar to the first control signal, and the second selection signal is a signal similar to the first selection signal.

The control circuit 40 has a selection circuit 40a. The control circuit 40 inputs the first control signal and the first selection signal input from the first control device 11 to the selection circuit 40a, and the second control signal and the second selection signal input from the second control device 12. is input to the selection circuit 40a.

Based on the input first selection signal and second selection signal, the selection circuit 40a selects which of the first control signal and the second control signal is the driving system control signal. Then, the selection circuit 40a inputs the control signal of the selected operation system to the drive circuits 41 and 42, thereby turning on/off the first switching element 31 and the second switching element 32 based on the control signal of the operation system. Control switching.

Thus, the control signal for the operating system and the control signal for the standby system can be selected on the converter CEL side, and the operation of the main circuit unit 14 can be controlled based on the control of the control device for the operating system. Further, the control signal for the operating system and the control signal for the standby system can be easily switched on the converter CEL side.

FIG. 3 is a block diagram schematically showing the first control device and the second control device.
As shown in FIG. 3 , the first control device 11 has a control signal generator 50 , a selection signal generator 52 and a synchronization controller 54 . The second control device 12 has a control signal generation section 60 , a selection signal generation section 62 and a synchronization control section 64 .

The configuration of the second control device 12 is substantially the same as that of the first control device 11 . The configuration of the control signal generation section 60 is substantially the same as the configuration of the control signal generation section 50, the configuration of the selection signal generation section 62 is substantially the same as the configuration of the selection signal generation section 52, and synchronization control is performed. The configuration of the section 64 is substantially the same as that of the synchronization control section 54 . Therefore, the configuration of the first control device 11 will be described below, and the detailed description of the configuration of the second control device 12 will be omitted.

The current values I _a1 to I _a6 detected by the current detectors 24 a to 24 f and the voltage values Vu, Vv, and Vw detected by the voltage detector 25 are input to the control signal generator 50 . be. Various command values such as a current command value and a voltage command value are input to the control signal generator 50 from a host controller or the like. The control signal generator 50 generates a first control signal for each converter CEL based on the input current value, voltage value, command value, and the like.

FIG. 4 is a graph diagram schematically showing an example of the operation of the control signal generator.
As shown in FIG. 4, the control signal generator 50 generates a first control signal for controlling switching of the switching elements 31 and 32 based on the voltage reference VR and the carrier signal CW. The control signal generator 50 sets the voltage reference VR for each converter CEL. When M converters CEL are connected in series to one arm, the control signal generator 50 sets M voltage references VR for each converter CEL. The carrier signal CW may be used in common for each converter CEL, or M carrier signals CW may be set for each converter CEL.

Voltage reference VR is, for example, sinusoidal. The control signal generator 50 adjusts the amplitude and phase of the voltage reference VR for each converter CEL. The frequency of voltage reference VR is set according to the frequency of the AC voltage of AC power system 2 . That is, the frequency is set according to the actual usage. The frequency of voltage reference VR is, for example, 50 Hz or 60 Hz. The carrier signal CW is, for example, triangular. The carrier signal CW may be a sawtooth wave or the like. The frequency of carrier signal CW is higher than the frequency of voltage reference VR.

The control signal generator 50 shifts the phase of the voltage reference VR of each converter CEL. The control signal generator 50 sets, for example, a voltage reference VR whose phase is shifted by 360/M (degrees) for each converter CEL in one arm.

The control signal generator 50 compares the voltage reference VR and the carrier signal CW. The control signal generation unit 50 generates, as the first control signal, a pulse signal that, for example, becomes Lo when the voltage reference VR is less than the carrier signal CW and becomes Hi when the voltage reference VR is greater than or equal to the carrier signal CW. However, the relationship between Hi and Lo of the first control signal may be opposite to the above.

The control circuit 40 of the converter CEL turns on the first switching element 31 and turns off the second switching element 32, for example, when the first control signal is Lo. In this case, the connection terminals 30a and 30b are short-circuited by the first switching element 31, and the voltage between the connection terminals 30a and 30b becomes substantially 0V. Then, for example, when the first control signal is Hi, the control circuit 40 turns off the first switching element 31 and turns on the second switching element 32 . In this case, the voltage Vc of the charge storage element 35 appears between the connection terminals 30a and 30b. That is, when the first control signal is Hi, the converter CEL is in an output state in which it outputs a predetermined voltage, and when the first control signal is Lo, the converter CEL is in a stop state in which it stops outputting a predetermined voltage. . When the first control signal is Hi, in other words, it is the first state for setting the converter CEL to the output state. When the first control signal is Lo, in other words, it is the state for stopping the converter CEL This is the second state for

Thus, the converter CEL outputs two-level voltages of +Vc and 0 by switching the switching elements 31 and 32 . The converter CEL may also be called a power cell, for example.

In the power converter 10, the sum of the output voltages of the converters CEL connected in series is the voltage of each of the arms 22a-22f. As a result, the power conversion device 10 can perform multi-level power conversion according to the number of serial connections of the converters CEL.

The control signal generation unit 50 adjusts the amplitude and phase of the voltage reference VR so that, for example, the current value and voltage value on the DC side of the main circuit unit 14 and the current value and voltage value on the AC side of the main circuit unit 14 approach the command values. to adjust. Thereby, the operation of the main circuit section 14 can be controlled based on the command value.

The selection signal generator 52 generates a first selection signal having an operating state indicating that the first control device 11 is in the operating system and a standby state indicating that the first control device 11 is in the standby system. . The selection signal generator 52 generates, for example, a binary first selection signal with Lo indicating the standby state and Hi indicating the operating state.

The synchronization control unit 54 synchronizes the operation of the first control unit 11 and the operation of the second control unit 12 by communicating with the synchronization control unit 64 of the second control unit 12 . For example, in the case of the operating system, the synchronization control unit 54 transmits information on the voltage reference VR of each converter CEL and information on the carrier signal CW to the second control device 12 of the standby system, thereby synchronizing the control amount. synchronizing the voltage reference VR and the carrier signal CW. As a result, substantially the same control signal can be generated in each of the operating system control device and the standby system control device.

In addition, the synchronization control unit 54 mutually confirms the timing of switching between the operating system and the standby system by communicating with the synchronization control unit 64 of the second control device 12 . For example, when the control signal generation unit 50 or the selection signal generation unit 52 fails while the operation system is operating, or when an instruction to perform maintenance is given, the synchronization control unit 54 is activated by the second control device. 12 synchronization control unit 64 to confirm the timing of switching between the operating system and the standby system.

The selection signal generation unit 52 switches between the operating state and the standby state of the first selection signal based on the instruction from the synchronization control unit 54 . Note that the method of switching between the operating system and the standby system is not limited to the method of switching by communication between the first control device 11 and the second control device 12 . For example, the operation system and the standby system may be switched by inputting instructions to each of the first control device 11 and the second control device 12 from a host controller, an operator (operation unit), or the like.

FIG. 5 is a timing chart that schematically shows an example of the operation of the power converter.
FIG. 5 schematically shows an example of the operation of the power conversion device 10 when switching the operation system control device from the first control device 11 to the second control device 12 .

As shown in FIG. 5, the first control device 11 and the second control device 12 switch the first selection signal and the second selection signal when switching between the operating state and the standby state of the first selection signal and the second selection signal. An overlap period is provided in which both signals are in the operating state.

The overlap period is set by adjusting the switching timing of the first selection signal and the second selection signal by communicating with each other between the first control device 11 and the second control device 12, as described above. be done. Also, the overlap period must be set so that each converter CEL can be switched between the operating system and the standby system. Therefore, for example, as described above, when the phase of the voltage reference VR of each converter CEL is shifted by one cycle (360 degrees), it is necessary to set the overlap period to one cycle or longer.

The selection circuit 40a of the control circuit 40 of the converter CEL selects the operation system and Switch to the standby system. For example, during the overlap period, the selection circuit 40a operates when the first control signal and the second control signal respectively become the second state (when Lo) for stopping the converter CEL. switch between the system and the standby system. On the contrary, when the first state is entered, the operating system and the standby system may be switched.

FIG. 6 is a timing chart schematically showing a reference example of the operation of the power converter.
Even if the voltage reference VR and the carrier signal CW are synchronized, the first control signal and the second control signal may cause a transmission delay when transmitting the information of the voltage reference VR to the standby side, and the control signal generation unit 50 , 60, as shown in FIGS. 5 and 6, they may not match perfectly, and slight errors may occur. Due to this error, if switching between the operating system and the standby system is performed instantaneously, there is a possibility that unnecessary jitter pulses are generated and unnecessary switching is performed.

For example, in FIG. 6, if the second selection signal is changed from the standby state to the operating state at the same timing as when the first selection signal is changed from the operating state to the standby state, the second control signal changes from the first selection signal to the first selection signal. Therefore, unnecessary switching is performed so that the converter CEL is in the output state for a moment and immediately becomes the stop state.

Therefore, in the reference example shown in FIG. 6, after the first selection signal is changed from the operating state to the standby state, the second selection signal is changed from the standby state to the operating state after a predetermined period of time has elapsed. For example, at the timing when the second control signal is in the second state, the second selection signal is changed from the standby state to the operating state. This can suppress the occurrence of unnecessary switching.

When both the first selection signal and the second selection signal are in the standby state, the control circuit 40 of the converter CEL turns off both the switching elements 31 and 32 . That is, the switching elements 31 and 32 are gate-blocked (GB). As a result, a disturbance occurs in which the output of the main circuit section 14 stops momentarily.

In particular, in the main circuit section 14 in which a plurality of converters CEL are connected in series, the period of the gate block is set to one cycle or more (the voltage reference VR of each converter CEL is period of the phase shift), and the period of the gate block becomes relatively long. For example, the disturbance of the output of the main circuit section 14 becomes large.

On the other hand, in the operation of the power converter 10 according to the present embodiment, as shown in FIG. , the operation system and the standby system are switched when the first control signal and the second control signal are in the same state.

As a result, even when switching between the operating system and the standby system, it is possible to suppress the occurrence of unnecessary switching without providing a gate block period. For example, the disturbance of the output of the main circuit section 14 can be suppressed to a slight temporal variation corresponding to the error between the first control signal and the second control signal. Therefore, it is possible to provide the power converter 10 that can suppress the stoppage of the operation of the main circuit unit 14 even when switching between the control signal for the operation system and the control signal for the standby system.

FIG. 7 is a block diagram schematically showing a modification of the converter.
As represented in FIG. 7, in this example the converter CEL further comprises a third switching element 33, a fourth switching element 34 and drive circuits 43,44. Elements substantially the same as the first switching element 31 and the second switching element 32 are used for the third switching element 33 and the fourth switching element 34 .

A pair of main terminals of the fourth switching element 34 are connected in series to a pair of main terminals of the third switching element 33 . Also, the third switching element 33 and the fourth switching element 34 are connected in parallel to the first switching element 31 and the second switching element 32 . The charge storage element 35 is connected in parallel with the first switching element 31 and the second switching element 32 and is connected in parallel with the third switching element 33 and the fourth switching element 34 .

A rectifying element 33d is connected to the third switching element 33 in anti-parallel with respect to the pair of main terminals. A rectifying element 34d is connected to the fourth switching element 34 in anti-parallel with respect to the pair of main terminals.

A first connection terminal 30 a of the converter CEL is connected between a first switching element 31 and a second switching element 32 . The second connection terminal 30 b is connected between the third switching element 33 and the fourth switching element 34 . In this example, the second connection terminal 30 b is connected to the main terminal of the first switching element 31 opposite to the main terminal connected to the second switching element 32 via the third switching element 33 . That is, in this example, the switching elements 31 to 34 are connected in a full bridge. In this example the converter CEL is a full bridge circuit.

The drive circuit 43 switches ON/OFF of the third switching element 33 based on the control signal input from the control circuit 40 . The drive circuit 44 switches ON/OFF of the fourth switching element 34 based on the control signal input from the control circuit 40 .

Thus, the converter CEL used in the MMC-type main circuit section 14 may be a half-bridge circuit or a full-bridge circuit.

In the converter CEL of the full bridge circuit, when the second switching element 32 and the third switching element 33 are turned on and the first switching element 31 and the fourth switching element 34 are turned off, the connection terminals 30a and 30b +Vc is output in between.

When the first switching element 31 and the fourth switching element 34 are turned on and the second switching element 32 and the third switching element 33 are turned off, -Vc is output between the connection terminals 30a and 30b.

Then, when the first switching element 31 and the third switching element 33 are turned on and the second switching element 32 and the fourth switching element 34 are turned off, or when the second switching element 32 and the fourth switching element 34 are turned off When the switch is turned on and the first switching element 31 and the third switching element 33 are turned off, 0 V is output between the connection terminals 30a and 30b.

In this way, the converter CEL of the full-bridge circuit can output power of three levels of +Vc, 0, and -Vc by combining the switching elements 31 to 34 that are turned on and off.

In this converter CEL, for example, the state of outputting +Vc is the first output state, the state of outputting -Vc is the second output state, and the state of outputting 0V is the stop state. The switching of each state of the converter CEL can be realized, for example, by making the first control signal and the second control signal ternary signals corresponding to 3 levels. Also in this converter CEL, when the first control signal and the second control signal are in the same state during the overlap period of the first selection signal and the second selection signal, the operation system and the standby system are switched. By switching, it is possible to suppress the stoppage of the operation of the main circuit section 14 while suppressing the occurrence of unnecessary switching.

In the above embodiment, the first control signal and the second control signal are signals corresponding to each state of the converter CEL. The first control signal and the second control signal are not limited to this, and may be signals corresponding to ON/OFF of the respective switching elements 31-34. The first control signal and the second control signal are, for example, a signal representing ON/OFF of the first switching element 31, a signal representing ON/OFF of the second switching element 32, and a signal representing ON/OFF of the third switching element 33. and a signal representing ON/OFF of the fourth switching element 34 .

In each of the embodiments described above, an MMC type power converter is used for the main circuit section 14 . The main circuit unit 14 is not limited to the MMC type, and may be a power converter of another type in which a plurality of converters CEL are connected in series, such as an MV (Medium Voltage) type power converter. Moreover, the main circuit unit 14 is not limited to a multistage power converter in which a plurality of converters CEL are connected in series, and may be, for example, a two-level inverter or a three-level inverter.

The power conversion device 10 is not limited to a DC power transmission system, and may be applied to any other system that requires AC-to-DC conversion and DC-to-AC conversion. The AC/DC conversion by the power converter 10 is not limited to both AC to DC and DC to AC, and may be AC to DC or DC to AC.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

2 AC power system 3, 4 DC transmission line 6 Transformer 10 Power converter 11 First controller 12 Second controller 14 Main circuit unit 20a, 20b DC Terminals 21a to 21c First to third AC terminals 22a to 22f First to sixth arm portions 23a to 23f Buffer reactors 24a to 24f Current detectors 25 Voltage detectors 26, 27 ... signal lines 30a, 30b ... first and second connection terminals 31 to 34 ... first to fourth switching elements 35 ... charge storage elements CEL ... converter 40 ... control circuit 41 to 44 ... drive circuit 50... Control signal generation unit 52... Selection signal generation unit 54... Synchronization control unit 60... Control signal generation unit 62... Selection signal generation unit 64... Synchronization control unit

Claims (3)

a main circuit unit having a plurality of switching elements, and performing at least one of AC power conversion from AC power to DC power and conversion from DC power to AC power by turning on and off the plurality of switching elements;
a first control device that controls the operation of the main circuit unit;
a second control device that controls the operation of the main circuit unit;
with
One of the first control device and the second control device is an operation system that actually controls the operation of the main circuit unit, and the other is a standby system that is a backup of the operation system. to be able to switch between systems,
The first control device transmits to the main circuit unit a first control signal for controlling the operation of the main circuit unit and a first selection signal for identifying the operating system and the standby system. ,
The second control device transmits to the main circuit unit a second control signal for controlling the operation of the main circuit unit and a second selection signal for identifying the operating system and the standby system. ,
The main circuit section selects a control signal for the operation system from the first control signal and the second control signal based on the first selection signal and the second selection signal, and selects the operation system for the selected operation system. a control circuit for controlling on/off of the plurality of switching elements based on a control signal;
The first selection signal and the second selection signal have an operating state indicating the operating system and a standby state indicating the standby system,
When switching between the operating system and the standby system, the first control device and the second control device provide an overlap period in which both the first selection signal and the second selection signal are in the operating state. ,
The control circuit switches between the operating system and the standby system when the first control signal and the second control signal are in the same state during the overlap period. The main circuit section has a plurality of converters connected in series,
2. The power converter according to claim 1, wherein each of said plurality of converters has said plurality of switching elements and said control circuit. The plurality of converters has an output state in which a predetermined voltage is output and a stop state in which output of the predetermined voltage is stopped,
The control circuit switches between the operating system and the standby system when the first control signal and the second control signal cause the converter to be in the stopped state during the overlap period. The power converter according to claim 2.

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