JP4103051B2 - Power converter for AC motor - Google Patents

Description

  The present invention relates to a power conversion device for a rotary type or direct acting type AC motor, and in particular, in a device that performs so-called sensorless driving without a position sensor of a rotor or a mover of the motor, the motor is idling. The present invention relates to a power converter for an AC motor characterized by means for starting a power converter from a state.

FIG. 12 is a block diagram corresponding to the prior art described in Patent Document 1 described later.
In FIG. 12, a power converter 1 constituted by a switching element and a passive element is supplied with power from an AC or DC power supply 4 to perform power conversion, and supplies power to an AC motor 3 as a rotating machine. .
The power converter 1 is controlled by the control unit 2. Since AC motor 3 has a field pole in the rotor, an induced voltage is generated when the rotor is rotated with the terminal open. Such an electric motor is collectively referred to as a field-equipped synchronous motor in this specification.

Generally, in order to drive a field synchronous motor, it is necessary to supply a voltage and a current according to the position of the rotor. Known sensors for detecting the position of the rotor include a photoelectric position sensor such as a rotary encoder, and an electromagnetic position sensor using a Hall element.
However, from the viewpoint of reliability, environmental resistance, cost, and the like, so-called sensorless driving is required that estimates the rotor position without using these position sensors.

In order to perform this sensorless drive, the control unit 2 shown in FIG. 12 is configured as follows.
First, 21 is a current conversion processing unit. The current conversion processing unit 21 synthesizes a three-phase current from two-phase currents obtained from the current sensors 5A and 5B of the AC motor 3, and converts the three-phase current into orthogonal rotation coordinates.

  Reference numeral 22 denotes a control arithmetic unit. The control calculator 22 estimates the rotor position in a state where power is supplied from the power converter 1 to the AC motor 3, calculates the voltage and current to be supplied by the power converter 1, and calculates a predetermined switching element. Outputs the on / off signal given to. In estimating the rotor position, the control calculator 22 acquires various information related to the current of the AC motor 3 from the current conversion processing unit 21, and performs necessary calculations based on these information. In addition, since the sensorless drive technique of the synchronous motor with a field executed by the current conversion processing unit 21 and the control arithmetic unit 22 is well known, detailed description thereof is omitted here.

Now, one of the major problems in position sensorless driving of a field synchronous motor is a method of starting the power converter from a state where the rotor is idling (referred to as free-run starting).
That is, as shown in FIG. 1 2, in the control system because control is performed based on the current of the AC motor 3, in the state in which the power converter 1 is not current flows stopped, the AC motor 3 No information is available. If the rotor is stopped, for example, the output voltage of the power converter 1 is adjusted so that a current flows in a certain phase, and thus the operation of the rotor can be started after the position of the rotor is drawn.

  However, if the power converter 1 is randomly started and the voltage is generated while the rotor is idling, current control becomes impossible because the AC motor 3 generates a dynamic induced voltage. It may not start normally. In the worst case, the switching element of the power converter 1 is damaged by an overcurrent, and there is a risk of irreversible demagnetization when the AC motor 3 has a permanent magnet.

  As a means for solving such a problem, when the AC motor is idling, its winding is momentarily short-circuited by the power converter, and the rotor position is estimated based on the current flowing at this time to start the power converter. The method is disclosed in Patent Document 1 described later.

  In Patent Document 1, the winding of the AC motor is short-circuited by turning on at least one of the switching elements constituting the power converter for operating the AC motor, and the rotation is performed based on the winding current flowing at that time. Estimating the position of a child is disclosed. This is because the winding current that flows due to the induced voltage when the AC motor winding is short-circuited is uniquely determined by the position and speed of the rotor of the AC motor and the circuit constant of the AC motor. The focus is on the fact that the position and speed of the rotor can be calculated by analysis.

In the prior art shown in FIG. 12, the free-run start-up calculating unit 23 in the control unit 2 generates an on / off signal to the switching element in the power converter 1 for short-circuiting the winding, and a current conversion processing unit. The rotor position estimation calculation at the time of rotor idling based on the current information obtained from 21 and the start-up sequence based on the obtained rotor position information are executed.
And after starting of the power converter 1, in order to transfer to normal operation, a process is switched by the changeover switch 24 from the free run starting calculating part 23 side to the control calculating unit 22 side. The operation of the changeover switch 24 is performed by a control switching unit 25 that supervises the operation of the control unit 2.

Furthermore, as another conventional technique, a brushless DC motor driving method described in Patent Document 2 below is known.
This prior art uses a three-phase inverter to drive a brushless DC motor without a rotor position sensor. When detecting the rotor speed and rotor phase of a brushless DC motor that is idling, a series connection in the inverter is used. The voltage is output so that the output voltage value determined by controlling the on / off ratio of the two switching elements is the same for all three phases, and the motor current detection value for at least two phases at that time Is to be used.

JP-A-11-75394 (Claim 1, paragraphs [0009] to [0012], FIG. 2, FIG. 3, etc.) JP-A-10-191585 (Claim 3, paragraphs [0038] to [0041], FIG. 6 etc.)

In the embodiment of the invention in Patent Document 1, the behavior when all phase windings of an AC motor are short-circuited is described in detail. However, a specific method for estimating the rotor position by short-circuiting only some of the windings of the phases is not disclosed. In general, passive circuit components such as a filter reactor are often inserted between the power converter and the AC motor. However, Patent Document 1 does not particularly consider such a case.
Further, Patent Document 2 does not disclose a specific method for estimating the rotor position by short-circuiting only a part of the windings of the three phases.

  Therefore, the present invention discloses specific means for estimating the position of the rotor and the mover based on the current that flows by short-circuiting the windings of some phases of the multiphase during idling of the multiphase AC motor. Thus, an object of the present invention is to provide a power converter for an AC motor that can reliably and easily start a power converter.

The basic principle of the present invention that solves the above problems is as follows.
First, FIG. 1 shows an equivalent circuit of the power converter 11 in the case of performing a short-circuit operation of the field-equipped synchronous motor 31 and the windings of the motor 31. There motor 31 is multi-phase AC motor, the induced voltage of each phase winding according to the field _{e 1, e 2, e 3} , ...... and the impedance _{Z 1, Z 2, Z 3} , indicated by the ...... . The power converter 11 is assumed to be composed of a plurality of AC switches Q.

The configuration of the control unit 2 that controls the switch Q of the power converter 11 is substantially the same as that shown in FIG. 12, and the current conversion process converts the current of the motor 31 from two phases to three phases and converts it into orthogonal rotation coordinates. Part 21 and the on / off signal generation to the switch Q in the power converter 11 for short-circuiting the winding, the rotor position estimation calculation based on the current information from the current conversion processing unit 21, and the obtained And a free-run start calculating unit 23 that executes a start sequence based on the rotor position information.
In FIG. 1, illustration of the control arithmetic unit 22, the changeover switch 24, and the control switching unit 25 (see FIG. 12) in the control unit 2 is omitted.

The induced voltage of each phase of the electric motor 31 is uniquely determined by the position and speed of the rotor, and the phase difference of the induced voltage between the phases is constant as an electrical angle. On the other hand, the impedances Z ₁ , Z ₂ , Z ₃ ,... Of each phase are constant if there is no saliency in the motor 31 when the influence of magnetic saturation is small. It is determined uniquely.
Therefore, the current that flows when several phases of the multiphase windings of the motor 31 are short-circuited is also uniquely determined by the position and speed of the rotor. Therefore, it is possible to estimate the position of the rotor by analyzing the winding current at the time of this short circuit.

A specific rotor position estimation method is, for example, as follows.
Consider the case where some of the phases of the motor 31 are short-circuited in FIG.
When the rotational speed can be regarded as substantially constant, the x-phase no-load induced voltage fundamental wave e _x of the motor with an n-phase field can be generally expressed as Equation 1.
[Formula 1]
e _x = ωψsin (ωt + θ _x + θ ₀ )
Here, ω: electrical angular frequency, ψ: magnetic flux linkage number amplitude of coil by field, t: time, θ _x : phase angle of x phase (where θ ₁ = 0), θ ₀ : initial phase Corner

Usually, θ _x is a constant different for each phase, and the value of θ _x for each phase is known because of design matters. Since the first phase phase angle θ ₁ = 0 as described above, the initial phase angle θ ₀ is nothing but the phase angle of the first phase no-load induced voltage e ₁ at time t = 0.
The electrical angular frequency ω is proportional to the rotational speed of the rotor. Specifically, when the number of magnetic poles is P, the relationship of Formula 2 is always established for the electrical angular frequency ω.
[Formula 2]
ω = (P / 2) × 2π × N / 60
Here, N: Rotational speed of the rotor per minute Since the case where the rotational speed N is substantially constant is discussed, ω is unknown but is a constant here.

  Also, Ψ is a constant on the premise that the influence of magnetic saturation and eddy current on the iron core of the motor is small, and is known because it is a design matter. Usually, since the electric motor is designed so that the influence of magnetic saturation of the iron core and eddy current is small, this assumption is almost always satisfied. In the evaluation of Ψ, it is also possible to take into account the effects of magnetic saturation and eddy currents.

From the above relationship, it can be seen that the unknowns in Equation 1 are two, ω and θ ₀ . Further, if it is possible to know the two values, will be each phase of the no-load induced voltage e _x is found, so that a voltage corresponding to the system can be booted by providing an inverter.
On the other hand, the impedance Z _x of each phase is a function of only the magnetic pole position, that is, a value specified by ω and θ _{0 on} the assumption that the influence of magnetic saturation and eddy current of the iron core of the motor is small. It has been known.

From the above, in the state where the rotor is idling and ω and θ ₀ are unknown, the current that flows when each phase terminal of the motor is partially short-circuited is different information depending on ω and θ ₀ , that is, It can be seen that the specific information of ω and θ ₀ is included.
Specifically, there are two types of unknowns at ω and θ ₀ , and the obtained circuit equation is the number of short-circuited circuits (the number of short-circuited phases −1) in the case of partial phase short-circuiting. Therefore, if the number of phases to be short-circuited is 3 or more, there are two or more circuit equations for the unknown 2 and it can be understood that ω and θ ₀ can be obtained in principle.

Note that the detection error and the calculation error can be reduced by performing the short-circuit operation a plurality of times and averaging the derived values of ω and θ ₀ each time.

Next, in FIG. 1, if the number of phases for short-circuiting the winding is 2, that is, the two-phase winding is short-circuited, there is only one short-circuit loop. Is the simplest.
For example, FIG. 2 is formed when two-phase windings of the U phase and the V phase are short-circuited on the equivalent circuit when the three-phase field synchronous motor 32 is operated by the power converter 12. The short-circuit loop is indicated by a bold line.

In motor 32 shown in FIG. _{2, e u, e v,} e w are U, V, the induced voltage of the _W-phase, Z _u, Z _v, the _{Z w} is a phase of the impedance. Here, as shown in the figure, by turning on the two switches Q in the power converter 12, only one short-circuited loop having the impedances Z _u and Z _v as a load is formed, and the unknown is ω as described above. And θ ₀ , and the circuit equation becomes one, ω and θ ₀ cannot be derived as they are. Therefore, by performing the short-circuiting operation twice, different circuit equations can be obtained each time. Therefore, it is possible to derive ω and θ ₀ by combining them.
Incidentally, performed at least three times the short-circuit operation, omega in each time by averaging the derived value of theta _0, it is possible to reduce or detection error, the computational error.

On the basis of the above principle, according to the first aspect of the present invention, the control unit of the power converter gives an ON signal to the first switching element among the switching elements when the motor is idling, and at this time, each phase induction of the motor is induced. When the current does not flow due to the action of the voltage and the diode connected in reverse parallel to the switching element, the ON signal is continued or interrupted until it flows, and when the current flows, the flowing current and its flow And starting the power converter by estimating the position of the rotor or mover of the electric motor based on the detected time.

According to the second aspect of the present invention, the control unit of the power converter gives an ON signal to the first switching element among the switching elements when the motor is idling, and at this time, each phase induced voltage of the motor, and When the current does not flow due to the action of the diode, the on signal is continued or interrupted until it flows, and when the current flows, the on signal is changed to an off signal and the first switching element is extinguished. The position of the rotor or mover of the motor is estimated based on the current flowing through the series of operations and the time when the current is detected by applying an ON signal to the second switching element. Then, the power converter is started .

The invention described in claim 3, in claim 2, as a second switching element, a distinguishable from the first phase current is flowed, current is not flowing even giving an ON signal at a certain time A switching element is selected.

According to a fourth aspect of the present invention, the controller of the power converter gives an ON signal to the first switching element among the switching elements when the motor is idling. The operation of changing the signal to an off signal to extinguish the first switching element and turning on or off any one of the plurality of switching elements is repeated until no current flows even if the on signal is applied. The operation by the control unit according to any one of claims 1 to 3 is started after the current stops flowing.

According to a fifth aspect of the present invention, in the fourth aspect , the first switching element is a switching element for which the on / off operation is repeated after the first switching element is extinguished.

The invention described in claim 6, which estimates the position of the rotor or armature by combining at least two functions of the control unit according to any of claims 1 to 5, to start the power converter It is.

The invention described in claim 7 is the power converter for an AC motor according to any one of claims 1 to 6, wherein a passive circuit component inserted between the motor and the power converter is provided. In the power converter for an AC motor provided, the control unit turns on at least one of the switching elements during the idling of the motor to substantially short-circuit a circuit composed of the winding of the motor and the passive circuit component. The power converter is started by estimating the position of the rotor or mover of the electric motor based on the current flowing during the short circuit.

The invention described in claim 8, in claim 2 or 3, if the phase sequence is known, after the first switching element extinguished, the on and immediately current even if the possibility is not flowing One of the switching elements is turned on, and thereby it is determined whether or not an electric current has passed immediately, thereby specifying the rotation direction.

According to a ninth aspect of the present invention, in the eighth aspect , after the first switching element is extinguished, one of the switching elements in which current may not flow immediately even if the first switching element is turned on is turned on. If the current does not flow immediately, the switching element is selected as the second switching element. If the current flows immediately, the current flows immediately even if it is turned on. The switching element that does not exist is selected as the second switching element.

The invention described in claim 1 0, in the second aspect, after the first switching element extinguished by turning on the switching elements other than phase belongs first switching element one by one sequentially, immediately By repeating the operation of turning off the switching element and turning on another switching element when a current flows, a switching element in which no current flows immediately even when it is turned on is identified. The element is selected as the second switching element.

  According to the present invention, during the idling of a rotary or direct acting multiphase AC motor, in particular, a sensorless driven multiphase AC motor, a current that flows by short-circuiting a winding of a part of the phases. Since the position of the rotor can be estimated based on the above, the power converter can be started reliably and easily.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 3 is a circuit diagram of the main part showing this embodiment. In the following description, it is assumed that the AC motor (field synchronous motor) is a three-phase motor. Further, 3 to 7 are views for explaining an embodiment of the invention described in claim 1-4.

In FIG. 3, reference numeral 13 denotes a self-extinguishing switching element Q _u , Q _v , Q _w , Q _x , Q _y , Q _z such as an IGBT, and diodes D _u , D _v , A three-phase power converter (inverter) 33 composed of D _w , D _x , D _y , and D _z is an AC motor operated by the power converter 13.
Here, at the time of idling of the electric motor 33, as shown in FIG. 3, U-phase gives an ON signal only to the switching element Q _x of the lower arm of (the switching element Q _u, phases consisting of Q _x), the remainder of the switching element Consider a state that gives an off signal. Note that the following description applies to any switching element that is turned on.

FIG. 4 is an equivalent circuit diagram when only the switching element Q _x is turned on, and the power converter 13 is substantially composed of the switching element Q _x and diodes D _x , D _y , and D _z .
The induced voltage of each phase of the motor 33 is assumed to be a three-phase balanced sine wave, the direction of the N pole of the magnetic pole in the rotor is the d axis, and the angle between the d axis and the excitation axis of the U phase winding (electrical When the angle is θ, when the rotor rotates in the forward direction (direction in which θ increases), the induced voltage of each phase is as shown in FIG. 5, and the above relationship is represented by a vector diagram in FIG. It becomes like this. That is, the induced voltage vector e in FIG. 7 is defined as a result of projecting the induced voltage value of each phase onto the U, V, and W axes each having a phase difference of 120 ° and combining these three vectors. This induced voltage vector e generally appears on the q axis orthogonal to the d axis, and rotates at a speed ω together with the dq coordinate system.

  Here, as shown in FIG. 5, 360 ° is divided into 6 portions each having 60 °, so that regions are defined as region <I> to region <VI>. In FIG. 5 and FIG. 7 (and FIG. 6 relating to rotor reversal described later), the electrical angle θ, the induced voltage, and the position of each region are matched.

From FIG. 4 and FIG. 5, how the current flows when only one switching element is turned on when the rotor is idling depends on the phase (magnitude relation) of each phase induced voltage e _u , e _v , e _w . I understand that it will change. That is, the following three phenomena can occur.
(1) No current flows. (State of induced voltage: region <III>, <IV>)
(2) Current flows only in certain two phases. (State of induced voltage: region <II>, <V>)
(3) Current flows in all three phases. (State of induced voltage: region <I>, <VI>)

  Which of the above phenomena (1) to (3) appears depends on the position of the rotor. Therefore, in an electric motor or drive device that does not have a rotor position sensor, a specific one of the above phenomena is intentionally generated without the rotor position information, that is, one switching at idle. It is impossible to control the power converter 13 so that only the element is turned on and a short-circuit current is allowed to flow in a plurality of phases.

Considering this in reverse, by using the phenomena (1) to (3) above, by observing the current flow, the state of the induced voltage phase from region <I> to region <VI> Can be determined. For example, when only the switching element Q _x described above is turned on, the state of the corresponding induced voltage is determined depending on which of the phenomena (1) to (3) appears when the switching element Q _x is turned on, and the induced voltage phase Since it is synchronized with the position of the rotor, the position of the rotor can be known.
When the rotor reverses (direction in which θ decreases), the induced voltage of each phase is as shown in FIG. Even in this case, it is clear that the same phenomenon as in normal rotation appears . Based on Symbol principle, as described below, thereby enabling more estimation of accurate rotor position.

For example, when the rotor rotates normally in the above example, if no current flows when only the switching element Q _x is turned on, the induced voltage vector e is calculated from the region <III> or the region <IV> from FIG. Can be determined to exist.
After making this determination, the ON state of the switching element Q _x is continued or intermittent. Meanwhile, if no current flows, the induced voltage vector e continues to exist in the region <III> or the region <IV>.
On the other hand, when the rotor is reversed in the above example, if no current flows when only the switching element Q _x is turned on, the induced voltage vector e is again the region <III> or region <IV> from FIG. Can be determined to exist.

Eventually, when the phase of each phase induced voltage e _u , e _v , e _w changes due to the rotation of the rotor and the induced voltage vector e goes out of the region <III> or region <IV>, the diode was blocking current D in _{the y} or D _z is the forward voltage is applied, current starts to flow. If this current flow is detected, it is pinpointed that the induced voltage vector e exists at either the boundary between the regions <II> and <III> or the boundary between the regions <IV> and <V>. Can be specified. In other words, the phase of the induced voltage can be specified, and the position of the rotor synchronized with this can be estimated.

Furthermore, W-phase currents flowing V-phase current passing from the state of zero current when changing the state of remains zero, i.e. a current flows through the diode D _y, the diode D _z is changed to a state in which no current flows In this case, the magnitude relationship between each phase induced voltage is
W-phase induced voltage e _w > U-phase induced voltage e _u > V-phase induced voltage _ev
Since that would be, as can be seen from FIG. 5, the rotor is forward, and the electrical angle when the can you to determine immediately that the 150 ° from Fig.
On the other hand, V-phase current flowing W-phase current passing from the state of zero current when changing the state of remains zero, i.e. a current flows through the diode D _z, to the diode D _y changes to a state in which no current flows In this case, the magnitude relationship between each phase induced voltage is
V phase induced voltage e _v > U phase induced voltage e _u > W phase induced voltage e _w
Therefore, in this case, it can be immediately determined that the rotor is reversed and the electrical angle at that time is 210 ° from FIG.

  Further, the magnitude of the rotational speed | ω | may be calculated from the amplitude of the flowing short-circuit current. That is, the amplitude of the no-load induced voltage is proportional to the speed, and since the phase is known in this situation, the current amplitude is also uniquely determined by the rotational speed.

By the above, (polarity omega) and the position of the rotor rotation direction, and the rotor speed │ω│ reveals, to estimate the position theta _s of the rotor at a certain time t _s of the following formula 3 It can be, and thereby can start the power converter 13 at time t _s.
[Formula 3]
_{θ s = θ 0 + ω (} t s -t 0)
However, θ ₀ ; rotor position determined at time t ₀ Here, since a series of operations are performed in a very short time, the rotational speed ω of the rotor is assumed to be constant.
The above contents correspond to the invention of claim 1 .

Then, after detecting the short-circuit current by turning on only the switching element Q _x as described above, further one of the six switching elements, typically by turning on the switching elements other than Q _x short The position and speed of the rotor can also be obtained by passing an electric current and performing the same operation as described above. In particular, when the current does not flow after the second on, the on state is continued or interrupted until the current flows, and when the current flows, the time is set as t ₁ and the determined rotor position is θ ₁ . As a result, the rotor speed ω can be obtained with polarity using Equation 4.
[Formula 4]
ω = (θ ₁ −θ ₀ ) / (t ₁ −t ₀ )
The above contents correspond to the invention of claim 2 .

Subsequently, a method for reliably performing the above-described simple speed detection method will be described below.
In the above description, it has been described that the switching element Q _x is kept in the on-state with no current flowing, and that the phase of the induced voltage can be determined when the current flows. From this, it can be specified which switching element is turned on next and the current does not flow.

For example, the result of the current detection, the rotation direction in forward and induction voltage vector e is at time t ₀ region from <IV> and is determined to be switched to <V>. In this case, since the induced voltage vector e exists in the region <V>, the magnitude relationship of the induced voltage induced voltage of each phase is
W-phase induced voltage e _w > U-phase induced voltage e _u > V-phase induced voltage _ev
It has become.

Therefore, even immediately turn on the switching element _{Q w} or _{Q y,} current by the action of the diode _{D z} or _{D y} are not Tsuryu. Followed, if similarly continuously or intermittently ON state of the switching element Q _w or Q _y, since current flowing through eventually rotation of the rotor, and the time and t _1, the rotor can be determined in the manner described above Is set to θ ₁ , the speed ω of the rotor can be obtained with polarity according to Equation 4.

If the switching element that is turned on the second time is Q _w , the rotor moves to the region <VI> when the electrical angle is rotated by 60 °, and the magnitude relationship of the induced voltage induced voltage of each phase is
U-phase induced voltage e _u > W-phase induced voltage e _w > V-phase induced voltage e _v
Therefore, current flows.
Further, if the switching element that is turned on the second time is Q _y , the rotor moves to the region <I> when the electrical angle rotates 120 °, and the magnitude relationship of the induced voltage induced voltage of each phase is
U phase induced voltage e _u > V phase induced voltage e _v > W phase induced voltage e _w
Therefore, current flows.

When considering an error of detection timing, who selects the Q _y on mode of the current non-flowing state continues over a longer period of time, the detection error rate is reduced. On the other hand, by selecting the mode to turn on the Q _w, because the current is faster flows, it is possible to shorten the time until the start of the power converter 13.
The above contents correspond to the invention of claim 3 .

As described above, it can be understood that the position of the rotor can be estimated efficiently if current does not flow when the first switching element is turned on. Therefore, the first switching element is turned on, and when a current flows, the switching element is turned off. One of all the switching elements is selected in sequence, and the same operation is repeated until the current stops flowing. Can be considered.
This idea corresponds to the invention of claim 4 .

Further, any switching element may be selected after the second time. However, if the switching element that repeats ON / OFF is limited to the switching element that is initially selected, it is possible to save time and trouble to newly select a switching element. In addition, as long as the rotor is rotating, if a single switching element is repeatedly turned on and off, the current will eventually stop flowing due to the phase change of the induced voltage, so efficient rotor position estimation must be performed reliably. Can do.
This idea corresponds to the invention of claim 5 .

FIG. 8 is a flowchart showing the efficient series of operations detailed above. Steps S2 to S15 in this flowchart cover all operations corresponding to the inventions of claims 1 to 5 described above.

Incidentally, when a current flows by ON The first switching element may estimate the position and speed of the rotor from the current. In particular, when a three-phase current flows, it can be estimated using the method described in Patent Document 1 described above. As a result, it is not necessary to repeat an operation in which the current is not passed, and the power converter can be activated quickly.

Furthermore, as a technique corresponding to the invention of claim 6 , it is possible to estimate the rotor position and speed by combining at least two of the operations corresponding to claims 1 to 5 .
For example, when a current flows when the first switching element is turned on, the position of the rotor is specified using that current (position θ ₀ at time t ₀ ), and the current is zeroed by turning off the switching element. Then, another switching element is turned on after a predetermined period, and when the current does not flow, the on-state is continued or interrupted, and the position of the rotor is again determined when the current flows (at time t ₁₎ . and position theta _1), it is conceivable to calculate the speed according to equation 4.
If such an operation is performed, the information obtained by each switching can be used without waste, and the power converter can be started quickly.

FIG. 9 is a circuit diagram showing another embodiment of the present invention corresponding to the seventh aspect. FIG. 9 shows a case where the AC motor 33 is a three-phase motor. The overall configuration is that the passive circuit component 6 is inserted between the power converter 12 (13) and the AC motor 33. Is the same as in the previous embodiment.

As the passive circuit component 6, for example, a filter reactor for current smoothing, a choke coil for reducing normal mode noise current, and the like are assumed.
When such a circuit component 6 is inserted, its impedance is inserted into the short-circuit loop of the winding. Therefore, the circuit operation when the switching element of the power converter 12 is turned on is the same as that of the previous embodiment. Thus, the case where there is no circuit component 6 is different.

However, when the impedance and voltage drop of the circuit component 6 are known, the rotor position can be estimated by a method similar to that of the previous embodiment by considering these known values. For example, when the circuit component 6 inserts a reactor in series with each phase, it is equivalent to the case where the series reactor of the AC motor 33 is increased. Therefore, if the impedance value in FIGS. It will be good.
Of course, even when the passive circuit component 6 is inserted as shown in FIG. 9, the technical contents described in claims 1 to 6 are applicable.

In all the embodiments described above (inventions of claims 1 to 6 ), as a method for detecting the current flowing through the motor, other than the method of directly measuring the current flowing through the motor 33 as shown in FIG. As in the embodiment shown in FIG. 10, it is possible to use a method of detecting the current of each phase lower arm (or upper arm) of the power converter 14 using current sensors R _su , R _sv , R _sw such as resistors. 10, reference numeral 14 denotes a power converter, and 26 denotes a control unit. The configuration of the control unit 26 is substantially the same as that of the control unit 2 in FIG.
That is, in the operation of the switching element in the present invention, when the switching element to be operated is limited to an element belonging to the lower arm (or upper arm), the current flowing through the lower arm (or upper arm) while the element is on This is because the phase current of the motor coincides in principle.
If the switching element is turned off after detecting the current flow, the current of the phase of the switching element cannot be detected, but the current of the other phase continues to flow through the diode of the lower arm (or upper arm) of the phase. The current in the phase in which the switching element is turned off can be regarded as zero when the current can be detected continuously.

  As described above, when the current detection method as shown in FIG. 10 is used, only a method for determining that the current becomes zero after the switching element is turned off needs to be slightly changed. For the determination, the above description can be similarly applied.

  On the other hand, as a method of detecting current, in a switching element having a diode connected in reverse parallel to the self-extinguishing type switching element, the current of the self-extinguishing type switching element is bypassed as shown in FIG. In the case of detecting only this, it is necessary to partially change the method described with reference to FIG. In FIG. 11, reference numeral 15 denotes a power converter.

That is, for example, when the electrical angle rotation direction in forward as in Fig. 5 is in the 30 ° to 150 DEG °, no current flows to turn on the switching elements Q _x U-phase lower arm, i.e. 11, eventually As already described, the current flow starts when the electrical angle reaches 150 °. At this time, the current of the switching element Q _x can be detected by the current sensor R _su . This time a current also flows through the V-phase, the current in the V phase lower arm to flow through the diode D _y, can not be detected in the current detector R _sv. Therefore, even when detecting the starting current through flow by the switching element Q _x U-phase lower arm, since the feedback current can not determine is whether passes through either of the V-phase and W-phase, that can not identify the direction of rotation Become.

The above problem can be solved by the following method corresponding to the invention of claim 8.
That is, first when the current of the switching element Q _x is no longer zero from zero, the state of no-load induced voltage immediately after this, or region of FIG. 5 <V> (electrical angle 0.99 ° to 210 ° in the forward rotation) Or one of the regions <II> in FIG. 6 (electrical angle 210 ° to 150 ° during reverse rotation). At this time, due to the magnitude relationship of the no-load induced voltage, even if the switching element Q _y or Q _w is turned on in the former and the switching element Q _z or Q _v is turned on in the latter, no current flows immediately. Conversely, the switching element Q _z or Q _v in the former _state, when turning on the switching element Q _y or Q _w in the latter state, immediately current flowing. From this, if any of the switching elements Q _y , Q _w , Q _z and Q _v is turned on and it is determined whether or not a current has immediately flowed, the rotational direction can be immediately specified.
Since the current of the lower arm is detected in the configuration of FIG. 11, the current sensors R _sv and R _sw are used to determine whether or not the current flows immediately by turning on either the switching element Q _y or Q _z. The direction of rotation can be specified by discriminating them.

Then, for example, if immediately current by turning on the switching element Q _y is not to flows, it can be determined to have been normal rotation, as if continuing the on-state of the switching element Q _y, the electrical angle reaches the 270 ° of FIG. 5 At this point, current flow starts, and this may be detected by the current sensor R _sv and determined to have passed the phase angle of 270 °.
On the other hand, if immediately current by turning on the switching element Q _y is flowed, it can be determined that the there was reversal, if turning on the switching element Q _z after turning off the switching element Q _y, eventually the electrical angle 6 When the current reaches 90 °, current flow starts. Therefore, this may be detected by the current sensor R _sw and determined to have passed the phase angle of 90 °. These operations are the same as those already described.

In the above description, the case where the number of phases is 3 has been described. However, even in the case where the number of phases is 4 or more, the rotation direction, position, and speed can be estimated in the rotor idle state by the same method.
That is, if the phase sequence is known, as described in claim 9 , when detecting the current of a switching element of a certain phase, for example, the switching element of the lower arm as shown in FIG. After switching the element from zero current to a non-zero state, turning off this switching element, it is clear from the phase sequence that multiple switching elements that may not immediately pass current when turned on, If the next switching element to be turned on among these is appropriately selected as the second switching element in claim 2 , the same operation as in the case of the three-phase can be performed.

On the other hand, if the phase sequence is unknown, as described in claim 1 0, after which turns on the first switching element moves to a state not zero from the current zero, and turns off the first switching element, When detecting a switching element of a phase other than the phase to which the first switching element belongs, for example, lower arm current as shown in FIG. 11, the lower arm switching elements are turned on one by one in order, and the current flows immediately. In this case, by repeating the operation of turning off the switching element and turning on the switching element of another phase, the phase to which the switching element (second switching element) to which no current flows even if it is turned on can be specified. The phase is a phase adjacent to the phase to which the first switching element belongs. Further, by repeating such an operation a plurality of times, the phase order can be specified for the phase in which the start of current flow is detected.

  In the above description, a rotary machine is used as the AC motor. However, the present invention can also be applied to a direct-acting AC motor such as a linear motor because of the electrical similarity between the rotary machine and the linear motor. In that case, what is necessary is just to read the rotor in the above-mentioned description as a mover and rotation as movement.

  Moreover, although the case of the three-phase was mainly described, the present invention can be applied to any power converter for a multi-phase AC motor. Furthermore, the description has been made assuming that the induced voltage waveform is a three-phase balanced sine wave. However, even if some harmonics are contained or there is a phase shift substantially existing in the three-phase induced voltage, the present invention There is no effect on the essence.

Furthermore, it goes without saying that the present invention can be similarly applied whether the motor is used as a power source or as a generator.
Of course, the present invention can also be applied to a device in which the rotor or the movable element has a position sensor or a sensor for the terminal voltage of the electric motor without using information obtained therefrom. That is, for example, the present invention can be applied as a backup technique when a position sensor or the like fails.

  In the above description, the windings of the AC motor are short-circuited, but actually there is a voltage drop in both the switching element and the cable connecting the power converter and the motor. However, the voltage drop is smaller than the electric constant of the AC motor, and can be regarded as a short-circuited state. If such a small voltage drop is taken into account in the analysis of the circuit behavior, a more accurate rotation can be achieved. The child position can be estimated.

It is an equivalent circuit diagram which shows the basic principle of this invention. It is an equivalent circuit diagram which shows the basic principle of this invention. It is a circuit diagram of the principal part which shows embodiment of this invention. FIG. 4 is an equivalent circuit diagram when the winding in FIG. 3 is short-circuited. It is a figure which shows the induced voltage of each phase at the time of the rotor normal rotation in FIG. It is a figure which shows the induced voltage of each phase at the time of rotor reverse rotation in FIG. It is explanatory drawing of the induced voltage vector in FIG. It is a flowchart for performing efficient rotor position estimation in the embodiment of the present invention. It is a circuit diagram of the principal part which shows other embodiment of this invention. It is a circuit diagram of the principal part which shows another embodiment of this invention. It is a circuit diagram of the principal part which shows another embodiment of this invention. It is a block diagram which shows a prior art.

Explanation of symbols

1, 11, 12, 13, 14, 15: Power converter 2: Control unit 21: Current conversion processing unit 22: Control calculator 23: Free-run start-up calculation unit 24: Changeover switch 25: Control switching unit 26: Control unit 3, 31, 32, 33: AC motor (field synchronous motor)
4: Power 5A, 5B: a current sensor 6: Passive circuit components Q: switch _{Q u, Q v, Q w} , Q x, Q y, Q z: switching element _{D u, D v, D w} , D x, D _y , _Dz : Diode _Rsu , _Rsv , _Rsw : Current sensor

Claims (10)

In a power converter for an AC motor comprising: a power converter that operates a multiphase AC motor; and a controller that generates and outputs an on / off signal for a switching element that configures the power converter.
The switching element is formed by connecting a plurality of self-extinguishing switching elements with diodes in antiparallel,
The controller is
When the motor is idling, an ON signal is given to the first switching element among the switching elements. At this time, when current does not flow due to the action of each phase induced voltage of the motor and the diode, the ON signal is applied until the current flows. When the signal continues or is interrupted and the current flows, the position of the rotor or the mover of the motor is estimated based on the flowing current and the time when the current is detected, and the power converter is activated. A power converter for an AC motor, characterized in that. In a power converter for an AC motor comprising: a power converter that operates a multiphase AC motor; and a controller that generates and outputs an on / off signal for a switching element that configures the power converter.
The switching element is formed by connecting a plurality of self-extinguishing switching elements with diodes in antiparallel,
The controller is
When the motor is idling, an ON signal is given to the first switching element among the switching elements. At this time, when current does not flow due to the action of each phase induced voltage of the motor and the diode, the ON signal is applied until the current flows. When the signal continues or is interrupted and the current flows, the on signal is changed to the off signal and the first switching element is extinguished, and then the on signal is applied to the second switching element to pass the current. The AC motor is activated by estimating the position of the rotor or mover of the electric motor based on the current flowing through the series of operations and the time when the flow is detected. Power converter. In the power converter for AC motors described in claim 2,
An AC motor power characterized by selecting a switching element that can be discriminated from a phase through which current first flows and that does not pass current even when an ON signal is given at a certain time as a second switching element Conversion device. In a power converter for an AC motor comprising: a power converter that operates a multiphase AC motor; and a controller that generates and outputs an on / off signal for a switching element that configures the power converter.
The switching element is formed by connecting a plurality of self-extinguishing switching elements with diodes in antiparallel,
The controller is
When the motor is idling, an on signal is given to the first switching element among the switching elements, and when current flows at this time, the on signal is changed to an off signal to turn off the first switching element. The operation of arcing and turning on / off any one of the plurality of switching elements is repeated until no current flows even when an ON signal is applied, and after the current stops flowing, any one of claims 1 to 3 An operation for the AC motor is started . In the power converter for AC motors described in Claim 4,
A power conversion device for an AC motor , wherein the first switching element is a switching element for which the on / off operation is repeated after the first switching element is extinguished . A power for an AC motor, wherein the power converter is activated by estimating a position of a rotor or a mover by combining at least two functions of the control unit according to any one of claims 1 to 5. Conversion device. The AC power converter for an AC motor according to any one of claims 1 to 6, comprising a passive circuit component inserted between the motor and the power converter. ,
The controller is
At the time of idling of the motor, at least one of the switching elements is turned on to substantially short-circuit a circuit composed of the winding of the motor and the passive circuit component, and based on the current flowing at the time of the short-circuit, A power converter for an AC motor, wherein the power converter is activated by estimating a position of a rotor or a mover . In the AC motor power converter according to claim 2 or 3 ,
If the phase order is known,
After extinguishing the first switching element, turn on one of the switching elements that may not allow current to flow immediately even if it is turned on. A power converter for an AC motor, characterized by specifying a direction . In the power converter for AC motors described in claim 8 ,
After extinguishing the first switching element, turn on one of the switching elements that may not allow current to flow immediately when turned on,
If the current does not flow immediately, the switching element is selected as the second switching element. If the current flows immediately, the current is immediately passed even if it is turned on. A switching element that does not flow is selected as a second switching element . In the power converter for AC motors described in claim 2,
After extinguishing the first switching element, by sequentially turning on the switching elements other than the phase to which the first switching element belongs one by one in turn, if a current flows immediately, the switching element is turned off. By repeating the operation of turning on another switching element, a switching element in which no current flows immediately even when turned on is identified.
The specified switching element is selected as a second switching element .

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