JP2012085475A - Induction motor control device, and induction motor control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction motor control device for controlling an induction motor so as to stably operate it.SOLUTION: Magnetic Energy Recovery Switches 100u, 100v, and 100w generate a voltage equivalent to one obtained by fluctuating the phase of a voltage generated by AC power supply VS by a value θset, and impress a voltage equivalent to the sum of the voltage and the voltage generated by the AC power supply VS on an induction motor M. A control part 200 determines the θset so that the effective value of the fundamental wave component of a load voltage detected by a voltage detecting part VM converges to a prescribed value, and determines timing of transition of each gate signal based on the θset value to supply the signal to each Magnetic Energy Recovery Switch.

Description

  The present invention relates to an induction motor control device and an induction motor control method.

  For example, Patent Document 1 discloses a technique for controlling an induction motor to operate stably while preventing an excessive current from flowing during startup. The method of Patent Document 1 is to increase the load voltage applied to the induction motor so as to follow the increase in the rotation speed of the induction motor after the start-up.

JP 2009-33942 A

  However, even in the case of the technique disclosed in Patent Document 1, during the startup of the induction motor, the rotational speed cannot be derived to a desired value, and as a result, the startup may fail.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an induction motor control device and an induction motor control method for controlling an induction motor to operate stably.

In order to achieve the above object, an induction motor control device according to a first aspect of the present invention includes:
Obtaining an input AC voltage generated by an external AC power source, generating a compensation voltage corresponding to the phase of the input AC voltage changed by an amount determined by the timing at which a predetermined control signal is supplied to itself, Series compensation means for applying a voltage corresponding to the sum of the input AC voltage and the compensation voltage to an external induction motor;
Control means for supplying the control signal to the series compensation means;
Load voltage detection means for detecting the amount of load voltage applied from the series compensation means to the induction motor, and generating a signal indicating the detected amount of the load voltage,
The control means includes
The signal generated by the load voltage detection means is acquired, the amount of the fundamental component of the load voltage indicated by the signal is specified, and the amount of the specified fundamental component is converged to a predetermined value. Timing determining means for determining timing;
Control signal supply means for supplying the control signal to the series compensation means at a timing determined by the timing determination means.

An induction motor control apparatus according to the second aspect of the present invention is
Obtaining an input AC voltage generated by an external AC power source, generating a compensation voltage corresponding to the phase of the input AC voltage changed by an amount determined by the timing at which a predetermined control signal is supplied to itself, A series compensation unit that applies a voltage corresponding to the sum of the input AC voltage and the compensation voltage to an external induction motor, and detects the amount of load voltage applied from the series compensation unit to the induction motor; An induction motor control device that controls the induction motor via a device comprising a load voltage detection unit that generates a signal indicating the amount of the detected load voltage,
The signal generated by the load voltage detection unit is acquired, the amount of the fundamental component of the load voltage indicated by the signal is specified, and the amount of the specified fundamental component is converged to a predetermined value. Timing determining means for determining timing;
Control signal supply means for supplying the control signal to the series compensator at a timing determined by the timing determination means.

An induction motor control method according to the third aspect of the present invention includes:
Obtaining an input AC voltage generated by an external AC power source, generating a compensation voltage corresponding to the phase of the input AC voltage changed by an amount determined by the timing at which a predetermined control signal is supplied to itself, A series compensation unit that applies a voltage corresponding to the sum of the input AC voltage and the compensation voltage to an external induction motor, and detects the amount of load voltage applied from the series compensation unit to the induction motor; An induction motor control method for controlling the induction motor via a device comprising a load voltage detection unit that generates a signal indicating the amount of the detected load voltage,
The signal generated by the load voltage detection unit is acquired, the amount of the fundamental component of the load voltage indicated by the signal is specified, and the amount of the specified fundamental component is converged to a predetermined value. A timing determination step for determining timing;
A control signal supply step for supplying the control signal to the series compensator at a timing determined in the timing determination step.

  According to the present invention, an induction motor control device and an induction motor control method for controlling an induction motor to operate stably are realized.

It is a figure which shows the structure of the induction motor drive device which concerns on the 1st Embodiment of this invention. It is a circuit diagram which shows the structure of MERS. It is a figure which shows the functional structure of the control part of FIG. It is a figure which shows transition of the load current at the time of starting of the three-phase induction motor by a prior art example, load voltage, the fundamental wave component of load voltage, a rotational speed, and a gate phase angle. It is a figure which shows transition of the load current at the time of starting of the three-phase induction motor by the induction motor drive device of FIG. 1, a load voltage, the fundamental wave component of a load voltage, a rotational speed, and a gate phase angle. It is a figure which shows transition of the load current at the time of starting of the three-phase induction motor by the induction motor drive device of FIG. 1, a load voltage, the fundamental wave component of a load voltage, a rotational speed, and a gate phase angle. It is a figure which shows transition of the load current at the time of starting of the three-phase induction motor by the induction motor drive device which concerns on the 2nd Embodiment of this invention, load voltage, the fundamental wave component of load voltage, rotational speed, and a gate phase angle. . It is a figure which shows twelve vectors corresponding to each phase voltage in virtual 12 phase alternating current generated from the value of each line voltage in three phase alternating current. It is a circuit diagram which shows the modification of MERS. It is a circuit diagram which shows the modification of MERS. It is a circuit diagram which shows the modification of MERS. It is a circuit diagram which shows the modification of MERS.

  Embodiments of the present invention will be described below with reference to the drawings, taking an induction motor drive device as an example.

(First Embodiment: Configuration)
As shown in FIG. 1, the induction motor drive device 10 according to the first exemplary embodiment of the present invention includes three MERSs (Magnetic Energy Recovery Switches) 100u, 100v, and 100w, and a voltage detection unit. A VM and a control unit 200 are included.

  MERS100u consists of full bridge type MERS as shown, for example in FIG. The MERS 100u shown in FIG. 1 includes four reverse conducting semiconductor switches SW1, SW2, SW3, and SW4 and a capacitor CM.

  The reverse conducting semiconductor switch SW1 includes a reverse conducting portion D1 and a switch portion S1. Similarly, the reverse conduction type semiconductor switch SW2 includes a reverse direction conduction part D2 and a switch part S2, the reverse conduction type semiconductor switch SW3 includes a reverse direction conduction part D3 and a switch part S3, and the reverse conduction type semiconductor switch SW4 includes It consists of a reverse direction conduction part D4 and a switch part S4.

  Each of the switch portions S1 to S4 includes, for example, a MOSFET (Metal-Oxide-Silicon Field Effect Transistor), an insulated gate bipolar transistor (IGBT), or other semiconductor switching elements, and includes a current path and a control terminal, respectively. It has. When a later-described ON signal is supplied to each control terminal, the current path is conducted, and when an OFF signal is supplied, the current path is interrupted.

  Each of the reverse direction conducting portions D1 to D4 is formed of a rectifying element such as a diode, for example, and includes a current path that conducts current only in one direction. This diode may be, for example, a parasitic diode of a semiconductor switch constituting the switch unit.

  In the following description, throughout each embodiment, unless otherwise specified, each reverse conducting portion is assumed to be a diode, and each switch portion is an n-channel MOSFET. In this case, the drain-source of the MOSFET forms a current path of the switch unit, and the gate forms the control end.

For each reverse conduction type semiconductor switch, the anode of the reverse conduction part is connected to the source of the switch part, and the cathode of the reverse conduction part is connected to the drain of the switch part, which is opposite to the current path of the switch part. Together, the current path of the direction conducting portion forms the current path of the reverse conducting semiconductor switch.
As a result of taking such a connection relationship, each reverse conducting semiconductor switch has a current flowing in a direction (forward direction) from the drain to the source of the switch unit to the value of the signal applied to the gate of the switch unit. Turn on / off accordingly. On the other hand, the current in the direction (reverse direction) from the source to the drain of the switch unit is always kept on as a result of the reverse direction conduction unit ensuring the bypass of this current.

  Each drain of the switch portions S1 and S3 is connected to one end (hereinafter referred to as a positive electrode) of the capacitor CM. Each source of the switch units S2 and S4 is connected to the other end (hereinafter referred to as negative electrode) of the capacitor CM.

  The source of the switch unit S1 is connected to the drain of the switch unit S2, and forms an AC input terminal AC1. The source of the switch unit S3 is connected to the drain of the switch unit S4 to form an AC output terminal AC2.

  The AC input terminal AC1 of the MERS 100u is connected to the pole U of an external AC power supply VS composed of, for example, a three-phase AC power supply having three poles U, V and W, and the AC output terminal AC2 of the MERS 100u is, for example, three It is connected to a pole U of an external induction motor M consisting of a three-phase induction motor having poles u, v and w.

  Note that the poles U, V, and W of the AC power supply VS all output a sine wave AC voltage, and the phase of the voltage output by the pole V is delayed by (2π / 3) radians with respect to the phase of the voltage of the pole U. It is assumed that the phase of the voltage output from the pole W is delayed by (4π / 3) radians with respect to the phase of the voltage at the pole U.

  The induction motor M can be represented as a network composed of three inductive loads LD1, LD2, and LD3 as shown in the figure. The inductive loads LD1, LD2, and LD3 can be represented as a series circuit of an inductor L1 and a resistor R1, a series circuit of an inductor L2 and a resistor R2, and a series circuit of an inductor L3 and a resistor R3, respectively. One end of each of the loads LD1, LD2, and LD3 forms the poles u, v, and w of the induction motor M, and the other ends of the inductive loads LD1, LD2, and LD3 can be represented as being connected to each other.

  The gates (in turn, G1u, G2u, G3u, and G4u) of the switch units S1, S2, S3, and S4 of the MERS 100u form a control end of the MERS 100u, and are all connected to the control unit 200.

Both MERS 100v and 100w have substantially the same configuration as MERS 100u.
The AC input terminal AC1 of the MERS 100v is connected to the pole V of the AC power source VS, and the AC output terminal AC2 of the MERS 100v is connected to the pole v of the induction motor M. The AC input terminal AC1 of the MERS 100w is connected to the pole W of the AC power source VS, and the AC output terminal AC2 of the MERS 100w is connected to the pole w of the induction motor M.

In the present specification and drawings, the reference numerals attached to the respective elements constituting the MERS 100u may be further indicated by “u” at the end. For example, the AC input terminal AC1, the reverse conducting semiconductor switch SW1, and the capacitor CM of the MERS 100u are also referred to as “AC input terminal AC1u”, “reverse conducting semiconductor switch SW1u”, and “capacitor CMu”, respectively.
Similarly, in this specification and the drawings, the reference numerals attached to the elements constituting the MERS 100v may be described by adding “v” at the end, and are attached to the elements constituting the MERS 100w. In addition, for reference numerals, a notation with “w” added at the end may be used.

  The voltage detection unit VM is formed of a known electric circuit that can detect an instantaneous value of an AC voltage, for example, and the value of the line voltage Vuv of the pole u with respect to the pole v of the induction motor M and the pole w of the induction motor M The value of the line voltage Vvw of the pole v and the value of the line voltage Vwu of the pole w with respect to the pole u of the induction motor M are continuously detected, and a signal representing the detected values of the line voltages Vuv, Vvw and Vwu And continuously supplied to the control unit 200. (Hereinafter, the three of the line voltages Vuv, Vvw and Vwu are collectively referred to as “Vload”.)

  The control unit 200 is constituted by a computer including a processor such as a CPU (Central Processing Unit) and a storage device such as a RAM (Random Access Memory) and a ROM (Read Only Memory), for example.

  Further, the control unit 200 includes an A / D (Analog-to-Digital) converter for converting, for example, a signal supplied from the voltage detection unit VM (that is, a signal indicating the value of the voltage Vload) into a digital signal. However, when the voltage detection unit VM supplies a signal indicating each value of the voltage Vload in a digital format, the control unit 200 does not need to include the above-described A / D converter.

  For example, the control unit 200 reads and executes a program stored in advance in its own storage device by its own processor, thereby performing processing described later, for example, the discrete Fourier transform unit DFT, the low-pass filter LPF, and the difference generation unit illustrated in FIG. Processing for performing the functions of the DFR, the proportional-plus-integral control unit PI, and the gate logic generation unit GL is executed.

  The discrete Fourier transform unit DFT obtains a signal supplied from the voltage detection unit VM, and represents a result of performing discrete Fourier transform on each value of the line voltages Vuv, Vvw, and Vwu included in this signal. Three pieces of data are generated and supplied to the low pass filter LPF.

  The low-pass filter LPF acquires each frequency domain data supplied by the discrete Fourier transform unit DFT, removes harmonic components from each of these data, and extracts each fundamental wave component of the line voltages Vuv, Vvw, and Vwu. To do. And the data which show the average Vrms of the effective value of each extracted fundamental wave component are produced | generated, and it supplies to the difference production | generation part DFR.

For example, the control unit 200 specifies the value of the above-described Vrms in order to realize the functions of the discrete Fourier transform unit DFT and the low-pass filter LPF, for example, for each of the line voltages Vuv, Vvw, and Vwu. The fundamental value of the phase voltage of each pole of the induction motor M is obtained by calculating the effective value of the inner product with the unit vector in the direction of the fundamental wave component one period before over one period and taking the arithmetic average of these three effective values. The value Vrms may be specified as a value corresponding to the average of the effective values of the components. That is, for example, a process for calculating the right side of Equation 1 shown below may be executed.
In Equation 1 and Equation 2 described later, Vuv (t), Vvw (t), and Vwu (t) represent the line voltages Vuv, Vvw, and Vwu as vector functions at time t, respectively. ω is an angular frequency of the three-phase AC voltage output from the AC power supply VS, and T is a period of the three-phase AC voltage, that is, (2π / ω). J is an imaginary unit.

The value Vrms of Equation 1 is calculated by taking the period to be calculated as a period for one period from time (t−T) to time t, in the fundamental wave component direction of Vuv (t) and the line voltage Vuv one period before. The inner product of the unit vector, the inner product of Vvw (t) and the unit vector in the fundamental wave component direction of the line voltage Vvw one cycle before, and the fundamental wave component direction of Vwu (t) and the line voltage Vwu one cycle ago For each of the inner products with the unit vector, find the effective value within the entire period to be calculated, take the arithmetic average of the total three effective values, and calculate the absolute value of these line voltages in the calculation. Is equivalent to the arithmetic average divided by (√3) in view of the fact that it becomes (√3) times the phase voltage of each pole of the induction motor M.
Note that “the effective value of the inner product of a certain voltage and its unit vector in the fundamental component direction within the entire period” specifically refers to the case where both the voltage and the unit vector are complexly expressed. The geometric mean of the value obtained by definite integration of the product of the coefficients of both real parts over the entire period and the value obtained by definite integration of the product of the coefficients of both imaginary parts over the entire period. Further, “one cycle ago” refers to a period of one cycle from (t−2T) to time (t−T).

  The difference generation unit DFR acquires data supplied by the low-pass filter LPF, generates data representing the difference Verr between the effective value Vrms indicated by this data and the target value Vset of the effective value, and supplies the data to the proportional-integral control unit PI. Supply. Data indicating the value of the target value Vset may be stored in advance in the storage device of the control unit 200, for example, or may be acquired from the outside via a known interface circuit (not shown). Then, the difference generation unit DFR may refer to the data and generate data representing the difference Verr on the assumption that the value indicated by the data is the target value Vset.

  The proportional integration control unit PI acquires data supplied from the difference generation unit DFR, and determines a gate phase angle θset, which will be described later, based on a value Verr indicated by the data. Then, data indicating the value of the determined gate phase angle θset is generated and supplied to the gate logic generation unit GL.

As processing for determining the value of θset, the proportional-plus-integral control unit PI performs, for example, processing described as (a) to (c) below.
(A) Every time the latest data representing the value Verr is supplied, the proportional-integral control unit PI acquires and stores this data, and the value Verr supplied over the predetermined past number of times including the latest data. The data representing is continuously stored. Further, whenever the latest value of θset is determined and data indicating the value is generated, this data is also stored. However, while no value of θset has been determined yet, for example, data indicating a predetermined initial value (initial phase) of θset is stored.
(B) On the other hand, every time the latest data representing the value Verr is supplied, the proportional-integral control unit PI refers to the latest data, and sets a predetermined first proportional coefficient to the value Verr indicated by the latest data. A value (first value) corresponding to the multiplied value is obtained. Further, each data representing the value Verr for the past predetermined number of times stored is referred to, and based on the value of these data, the value Verr is integrated for the most recent predetermined period and multiplied by a predetermined second proportionality constant. A value (second value) corresponding to the above is obtained. The predetermined period for integrating the value Verr is, for example, used for generating the latest data from the time when the value of the voltage Vload used for generating the oldest data stored as data representing the value Verr is measured. Any period up to the time when the value of the voltage Vload is measured may be used.
(C) Then, the proportional-plus-integral control unit PI refers to the data stored as data indicating the latest value of θset, and the three values of the data and the first and second values described above are mutually connected. Addition is performed and the obtained value is determined as the latest value of θset. (And as described above, data indicating the determined value of the new θset is generated and stored.)

  The gate logic generation unit GL acquires the data supplied by the proportional integration control unit PI, and based on the value of the gate phase angle θset indicated by this data, the timing for turning on each of the reverse conducting semiconductor switches of the MERSs 100u to 100w is described later. According to the determination result, gate signals SGG1u, SGG2u, SGG3u, SGG4u, SGG1v, SGG2v, SGG3v, SGG4v, SGG1w, SGG2w, SGG3w and SGG4w are generated, and gates G1u, G2u, G3u and G4u are generated. , G1v, G2v, G3v, G4v, G1w, G2w, G3w and G4w.

  Each gate signal is a signal that instructs on or off of a semiconductor switch including a gate to which the gate signal is supplied. For example, the gate signal (ON signal) when instructing ON takes a voltage (high level voltage) sufficient to turn on the semiconductor switch, and the gate signal (OFF signal) when instructing OFF is A voltage (low level voltage) sufficient to turn off the semiconductor switch is taken.

(First Embodiment: Operation)
Next, the operation of the induction motor driving apparatus 10 having the above configuration will be described.
First, the operation in which the MERS 100u controlled by the control unit 200 supplies an AC voltage from the pole U of the AC power supply VS to the induction motor M is described in paragraphs 0055 to 0066 of the above-mentioned patent document. The operation is substantially the same as that for supplying voltage from the motor to the motor.

That is, the control unit 200 is a pair composed of reverse conducting semiconductor switches SW2 and SW3 (hereinafter referred to as “pair P1”, which corresponds to a pair composed of reverse conducting semiconductor switches 113 and 111 in Patent Document 1) and reverse. A pair of conductive semiconductor switches SW1 and SW4 (hereinafter referred to as “pair P2”, which corresponds to a pair of reverse conductive semiconductor switches 114 and 112 in Patent Document 1) is alternately turned ON / OFF. Gate signals SGG1u to SGG4u having patterns are generated and supplied to MERS 100u.
By such a gate signal, the control unit 200 causes (i) an operation in which the pair P1 is first turned on and the pair P2 is turned off, and (ii) the pair P1 is turned off after the voltage of the pole U turns negative, and the pair P2 And the operation of turning ON, and this cycle is repeated in the MERS 100u with a period substantially equal to the period of the voltage of the pole U.

  However, in the present embodiment, the above-described gate phase angle θset is used as a value instead of “gate phase angle α” in Patent Document 1. The gate logic generation unit GL of the control unit 200 indicates that the phase of each state transition of the gate signals SGG1u to SGG4u is the latest gate phase angle θset (θset value indicated by the data supplied by the proportional integration control unit PI is still one. In an undecided state, these gate signals are generated so that the phase is substantially equal to the initial phase described above.

Note that the gate phase angle θset is a phase angle in which the zero cross point at which the phase voltage of the pole U of the AC power supply VS (voltage with respect to a reference potential not shown) turns from negative to positive is phase 0.
In order to detect the zero cross point, the control unit 200 may include a known electric circuit that detects the polarity of the phase voltage of the pole U and generates a signal indicating the detection result, for example. Specifically, for example, the control unit 200 may simply be connected to the pole U, or a signal indicating the polarity detection result obtained by dividing the phase voltage of the pole U by a voltage dividing resistor (not shown) or the like. It may be treated as.

When the pair P1 is turned on and the pair P2 is turned off, the negative electrode of the capacitor CM is electrically connected to the pole U, the positive electrode is electrically disconnected from the pole U, and is electrically connected to the pole u of the induction motor M. Is done. As a result, the AC power supply VS and the capacitor CM form a series circuit (series circuit in the first direction), and the pole u has a phase voltage of the pole U and a positive voltage with respect to the negative electrode of the capacitor CM. A voltage corresponding to the sum of is applied.
On the other hand, when the pair P1 is turned off and the pair P2 is turned on, the positive electrode of the capacitor CM is electrically connected to the pole U, and the negative electrode is electrically disconnected from the pole U and electrically connected to the pole u. . As a result, the AC power supply VS and the capacitor CM form a second series circuit in which the pole of the capacitor CM connected to the pole U is different from the series circuit in the first direction. At this time, a voltage corresponding to the sum of the phase voltage of the pole U and the voltage of the negative electrode with respect to the positive electrode of the capacitor CM is applied to the pole u.
Since the voltage generated across the capacitor CM varies by θset with respect to the phase voltage of the pole U, the voltage generated across the series circuit of the AC power supply VS and the capacitor CM is AC. It can be said that this corresponds to the voltage of the power supply VS added with phase compensation.

On the other hand, the operations of MERS 100v and 100w are substantially the same as the operations of MERS 100u except for the following points (A) to (C).
(A) The phases of the pole V and the pole W of the AC power supply VS are delayed by (2π / 3) radians and (4π / 3) radians with respect to the phase of the phase voltage of the pole U, respectively.
(B) The gate signals SGG1v, SGG2v, SGG3v, and SGG4v are obtained by delaying the phases of the gate signals SGG1u, SGG2u, SGG3u, and SGG4u by (2π / 3) radians, respectively. The gate signals SGG1w, SGG2w, SGG3w and SGG4w are obtained by delaying the phases of the gate signals SGG1u, SGG2u, SGG3u and SGG4u by (4π / 3) radians, respectively.
(C) The current flowing between the AC power supply VS and the MERS 100v flows via the pole V and the AC input terminal AC1v, and the current flowing between the induction motor M and the MERS 100v passes through the AC output terminal AC2v and the pole v. Flowing. Similarly, the current flowing between the AC power source VS and the MERS 100w flows through the pole W and the AC input terminal AC1w, and the current flowing between the induction motor M and the MERS 100w passes through the AC output terminal AC2w and the pole w. Flowing.

  By performing the operation described above, the induction motor drive device 10 supplies a three-phase AC voltage to the induction motor M. On the other hand, the induction motor driving device 10 extracts the fundamental wave component of the three-phase AC voltage, specifies the amount Vrms, and proportionally sets the value of the gate phase angle θset so that the amount Vrms converges to the constant amount Vset. Integral control.

  On the other hand, unlike the present embodiment, for example, as a conventional method, the effective value of the load voltage of each phase of the induction motor M (effective value including both fundamental and harmonic components) is constant. When the MERS 100u, 100v, and 100w are controlled so as to converge to the value, the induction motor M may not start stably. The induction motor drive device 10 according to the present embodiment suppresses this adverse effect and facilitates stable startup of the induction motor M.

That is, first, when control is performed to converge the effective value of the load voltage including both fundamental wave and harmonic components of each phase of the induction motor M to a constant value, for example, as shown in FIG. In some cases, the rotational speed of M converges to a desired target value (that is, the induction motor M is normally started).
FIG. 4 illustrates changes in load current, load voltage, fundamental component of the load voltage, rotation speed, and gate phase angle when the target value of the rotation speed of the induction motor M is 1800 [min ⁻¹ ]. Is. From FIG. 4, it can be seen that after the elapsed time from the start of about 10 seconds, the increase in the rotation speed reaches a peak and does not reach the target value.

The reason why such a phenomenon occurs may be that the harmonic component included in the load voltage causes the feedback control to the induction motor M performed via the MERSs 100u, 100v, and 100w to be erroneous.
That is, first, it can be said that the fundamental wave component contributes to normal rotation of the induction motor M among the components of the load voltage. On the other hand, it is considered that the fundamental wave component can be controlled by changing the gate phase angles of the MERSs 100u, 100v and 100w among the components of the load voltage. For this reason, even if the control unit 200 that controls the gate phase angle of the MERS 100u, 100v, and 100w determines the gate phase angle so that the total amount of load voltage or load current is controlled, and the total amount converges to a predetermined amount, The fundamental component of the load voltage or load current supplied by the MERS 100u, 100v, and 100w does not necessarily have a value that converges to a predetermined amount (that is, the difference between the amount of the fundamental component and the predetermined amount converges to 0). do not do). This is because, for example, in the transition of the load voltage shown in FIG. 4, the ratio of the harmonic component to the total amount of the load voltage increases and the amount of the fundamental component of the load voltage decreases when about 14 seconds elapse from the start. As you can see, it ’s right. This phenomenon is considered to be a cause of hindering normal startup of the induction motor M.

On the other hand, the transition of the load current, the load voltage, the fundamental component of the load voltage, the rotation speed, and the gate phase angle when the induction motor M is started by the induction motor drive device 10 according to the present embodiment is shown in FIG. 5, for example. (However, in FIG. 5, the target value of the rotational speed of the induction motor M is 1500 [min ⁻¹ ]).
As can be seen from FIG. 5, the amount of the fundamental component of the load voltage is substantially constant from the time of startup, and the rotation speed of the induction motor M reaches the target value in about 4 seconds after startup. From this, it can be inferred that the normal startup of the induction motor M is ensured if the fundamental component of the load voltage is converged to a sufficient predetermined amount.

In addition, the structure of this induction motor drive device 10 is not restricted to the above-mentioned thing.
For example, the number of phases of the AC power source VS and the induction motor M may be more than three. When the AC power source VS is composed of a p-phase AC power source (p is an integer of 3 or more) and the induction motor M is composed of a p-phase induction motor, each induction motor starting device 10 has substantially the same configuration as the MERS 100u. What is necessary is just to provide MERS. In this case, a total of p AC input terminals AC1 of these p MERSs may be connected to the p poles of the AC power supply VS on a one-to-one basis. The total of p AC output terminals AC2 may be connected to the p poles of the induction motor M on a one-to-one basis.
For example, the phase of the phase voltage of the qth pole (q is a natural number equal to or less than p) of the AC power supply VS is delayed by {2π (q−1) / p} radians with respect to the phase voltage of the first pole. Then, the control unit 200 sets the phase of the gate signal supplied to the switch units S1, S2, S3, and S4 of the MERS connected to the first pole of the AC power supply VS to {2π (q−1) / p, respectively. } What is to be delayed by radians may be supplied to the switch units S1, S2, S3, and S4 of the MERS connected to the qth pole of the AC power supply VS.

  The control unit 200 does not necessarily perform Fourier transform on the voltage Vload, but extracts a fundamental wave component by filtering the voltage Vload by an arbitrary method, and generates data indicating the value Vrms based on the obtained value. do it.

(Second Embodiment)
In the first embodiment described above, the control unit 200 specifies the value Vrms corresponding to the average of the effective values of the fundamental wave components of the phase voltage of each pole of the induction motor M, so that the line voltages Vuv, Vvw and For each Vwu, the effective value of the inner product with the unit vector in the fundamental wave component direction one cycle before was obtained over one cycle, and the arithmetic average of these three effective values was taken. However, the control unit 200 obtains the effective value of the inner product with the unit vector in the fundamental wave component direction of the previous one-third cycle for each of the line voltages Vuv, Vvw, and Vwu over one-third cycle. The value Vrms may be specified by taking the arithmetic average of the effective values.
In this case, specifically, the control unit 200 may specify the value of Vrms by executing, for example, processing for calculating the right side of Equation 2 shown below.

  The value Vrms of Equation 2 is calculated by setting Vuv (t) and the previous one-third cycle as a period for one-third cycle from time {t− (T / 3)} to time t. The inner product of the unit voltage in the fundamental wave component direction of the line voltage Vuv, the inner product of Vvw (t) and the unit vector in the direction of the fundamental wave component of the line voltage Vvw of the previous third cycle, and Vwu (t) For the inner product of the line voltage Vwu of the previous one-third cycle with the unit vector in the fundamental wave component direction, the effective value within the whole period to be calculated is obtained, and the arithmetic average of the three effective values obtained in total is obtained. And is divided by (√3). Note that “one-third cycle before” refers to a period of one-third cycle from {t− (2T / 3)} to time {t− (T / 3)}.

As a process for specifying the value Vrms, for each of the line voltages Vuv, Vvw, and Vwu, the effective value of the inner product with the unit vector in the fundamental wave component direction of the previous third cycle is obtained over a third cycle. In this way, the control unit 200 can obtain the latest value of the gate phase angle θset with a shorter cycle than when the effective value of the inner product is obtained over one cycle. For this reason, the fundamental wave component of the load voltage can be converged more quickly and constantly, and the induction motor M can be started more stably.
And according to the induction motor drive device of 2nd Embodiment, the bad effect which may still arise when the induction motor M is started by the induction motor control apparatus 10 of 1st Embodiment is suppressed.

That is, when the induction motor M is started by the induction motor drive device 10 of the first embodiment, the load current may vibrate as shown in FIG. 5 or FIG. 6, for example (in the example shown in FIG. The load current vibrates in a period of about 1 to 3 seconds from the time). This vibration is due to the fact that feedback control for converging the value of Vrms to Vset is not performed at a sufficiently high speed. As a result of such vibration, for example, an abnormality such as feedback control may diverge or the induction motor M may fail to start may occur. Further, such vibration leads to vibration of the shaft torque of the induction motor M, which causes shaft torsional resonance with the mechanical system connected to the induction motor M, resulting in shaft breakage. possible.
FIG. 6 illustrates changes in load current, load voltage, fundamental component of the load voltage, rotation speed, and gate phase angle when the target value of the rotation speed of the induction motor M is 1500 [min ⁻¹ ]. Is. In the example shown in FIG. 6, the load current vibrates in a period of about 3 seconds to 5 seconds after the start.

On the other hand, the transition of the load current, the load voltage, the fundamental component of the load voltage, the rotation speed, and the gate phase angle when the induction motor M is started by the induction motor driving device according to the second embodiment is shown in FIG. As shown in FIG.
As can be seen from FIG. 7, the amount of the fundamental component of the load voltage becomes substantially constant from the start-up time, and the load current is suppressed from vibration compared to that shown in FIG. 5. Further, the rotational speed of the induction motor M reaches the target value in about 4 seconds from the start. Further, the induction motor M can be normally started even if a value lower than the lowest value that can converge the value of Vrms in the first embodiment is used as the target value Vset.

  Similarly, when the number of phases of the AC power supply VS and the induction motor M is p (p is an integer greater than 3), the control unit 200 similarly applies p for each value of each line voltage in the p-phase AC. What is necessary is to determine the value Vrms by calculating a total of p effective values of inner products with the unit vector in the fundamental wave component direction one cycle before and taking the arithmetic average of these effective values.

(Third embodiment)
Further, the control unit 200 generates (3 · 2 ⁿ ) values corresponding to the phase voltages in the virtual (3 · 2 ⁿ ) phase AC based on the values of the line voltages Vuv, Vvw, and Vwu. (Where n is an arbitrary natural number including zero), and for each of these generated values, find (3 · 2 ⁿ ) total effective values of the above inner product over {1 / (3 · 2 ⁿ )} periods. The value Vrms may be specified by taking the arithmetic average of these effective values.
The value of each phase voltage in a virtual (3 · 2 ^{k + 1} ) phase alternating current (k is a natural number between 0 and n−1) is generated based on the value of each phase voltage in the (3 · 2 ^k ) phase alternating current, for example. it can. Moreover, the value of each phase voltage in the said three-phase alternating current can also be derived using the value of each line voltage in the three-phase alternating current.

Specifically, first, when each of the phase voltages Vu, Vv, and Vw of the poles u, v, and w and the line voltages Vuv, Vvw, and Vwu are all expressed as vectors, Vu, Vv, and Vw are (2π / 3) If the radian phase is different, each value of Vu, Vv, and Vw can be expressed using each value of Vuv, Vvw, and Vwu. On the other hand, if each phase voltage in the (3 · 2 ^k ) phase alternating current is expressed as a vector value of the phase voltage, the base point is at the origin of the coordinate plane and {2π / (3 · 2 ^k )} radian intervals Can be represented as (3 · 2 ^k ) vectors arranged radially. For example, when k = 1, the value of each phase voltage in a three-phase alternating current is radially arranged at (2π / 3) radians with the base points at the origin of the coordinate plane as shown in FIG. Can be represented as three vectors v1, v5 and v9. The vectors v1, v5 and v9 can be regarded as representing the above-mentioned phase voltages Vw, Vv and Vu, for example.
Then, for these (3 · 2 ^k ) vectors, the values of two vectors that are adjacent on the coordinate plane are added together, and the obtained vector is scalar-multiplied to normalize the vector (ie, By making the absolute value of the vector equal to the absolute value of each vector used in the above addition, (3 · 2 ^k ) vectors arranged in the middle of these vectors can be generated. By generating vector values in this way, the total number of vectors can be doubled to a total of (3 · 2 ^{k + 1} ).

By repeating such an operation for doubling the vector by increasing the value of k by 1 from 0 to n−1 (n−1) times, the control unit 200 allows each phase voltage in three-phase AC to be the value, it is possible to produce a corresponding (3 · 2 ⁿ⁾ number of values to phase voltages in the virtual (3 · 2 ⁿ⁾ phase AC.
Then, for each of these generated values, the control unit 200 calculates a total effective value of (3 · 2 ⁿ ) inner products with unit vectors in the fundamental wave component direction before {1 / (3 · 2 ⁿ )} periods. The value Vrms may be specified by obtaining and calculating the arithmetic average of these effective values.

FIG. 8 shows a case where twelve vectors are generated from the values of the respective phase voltages in the three-phase alternating current as equivalent to the respective phase voltages in the virtual 12-phase alternating current (that is, the above-mentioned n value is 2, k It is a figure which illustrates the 12 vectors in the case where the initial value of is 0).
If the vectors representing the values of the phase voltages Vw, Vv, and Vu are the vectors v1, v5, and v9 shown in FIG. 8, first, the vector v3 is used using the vectors v1 and v5, and the vector is used using the vectors v5 and v9. Vector v11 can be generated using vectors v9 and v1, respectively.
Then, the vector v1 and v3 are used, the vector v2 is used, the vectors v3 and v5 are used, the vector v4 is used, the vectors v5 and v7 are used, the vector v6 is used, the vectors v7 and v9 are used, and the vectors v9 and v11 are used. Can be used to generate a vector v10, and vectors v11 and v1 can be used to generate a vector v12.

A total of 12 vectors consisting of the vectors v2 to v4, v6 to v8 and v10 to v12 and vectors v1, v5 and v9 generated in this way are 12 virtual 12-phase alternating currents as shown in the figure. It represents the value of the phase voltage.
Then, as shown in the figure, when the waveforms of these 12 phase voltages are cut out in a period corresponding to 1/12 cycle, and the cut out waveforms are connected, it corresponds to a single-phase AC voltage for 1 cycle. Can be synthesized.
As can be seen from the above, the control unit 200 can generate 12 values corresponding to the phase voltages in the virtual 12-phase alternating current from the values of the line voltages in the three-phase alternating current, and these generated values. For each of the above, a total of 12 effective values of the inner product described above are obtained over one-twelfth period, and an arithmetic average of these effective values is taken to obtain a value corresponding to the value Vrms.

As described above, as the process for specifying the value Vrms, the effective value of the inner product described above is obtained for each of the (3 · 2 ⁿ ) values obtained based on the values of the line voltages Vuv, Vvw, and Vwu. If the value is obtained over a {1 / (3 · 2 ⁿ )} period, the control unit 200 can reduce the gate phase angle with a shorter period than when the effective value of the inner product is obtained over a third period. The latest value of θset can be obtained. For this reason, the fundamental wave component of the load voltage can be converged more quickly and constantly, and the induction motor M can be started more stably.

Similarly, when the number of phases of the AC power supply VS and the induction motor M is p (p is an integer greater than 3), the control unit 200 determines the virtual (p · 2 ⁿ⁾ corresponding to each phase voltage in-phase AC (p · 2 ⁿ⁾ to generate a number of values, for each of the generated these values, {1 / (p · 2 n)} period previous fundamental wave The value Vrms may be specified by obtaining a total of (p · 2 ⁿ ) effective values of inner products with the unit vectors in the component direction and taking the arithmetic average of these effective values.

As mentioned above, although the 1st-3rd embodiment of this invention was described, embodiment of this invention is not restricted to the above-mentioned thing.
For example, the induction motor driving device 10 may include a current detection unit including a known electric circuit capable of detecting the amount of alternating current. In this case, for example, the current detection unit continuously detects the amount of load current flowing through the induction motor M, generates a signal representing the detected amount of load current, and continuously supplies the signal to the control unit 200. Good.
On the other hand, the control unit 200 may include, for example, an A / D (Analog-to-Digital) converter for converting a signal supplied from the current detection unit into a digital signal. However, when the current detection unit supplies a signal indicating the amount of load current in a digital format, the control unit 200 does not need to include this A / D converter.
And the control part 200 may specify the value which the signal which the electric current detection part supplied shows, and may determine the value Vset based on the specified value. The determination method is arbitrary. For example, the control unit 200 stores a table including data specifying the correspondence between the amount of load current and the value Vset, and the value indicated by the signal supplied by the current detection unit is used as a search key. You may determine by searching this table. Further, by storing data indicating a predetermined mathematical expression that represents the value of Vset as a function of the load current, and calculating a value obtained by substituting the value indicated by the signal supplied by the current detection unit into the mathematical expression indicated by this data. You may decide.

  In addition, the control unit 200 does not necessarily perform proportional-integral control on the value of θset, and may perform arbitrary feedback control that can converge the value of Vrms to Vset.

Moreover, all of MERS100u, 100v, and 100w may be comprised from the vertical half bridge type MERS.
For example, when the MERS 100u is composed of a vertical half-bridge type MERS, the MERS 100u includes, for example, two reverse conducting semiconductor switches SW1 and SW2, rectifiers D3 and D4, capacitors CM1 and CM2, as shown in FIG. It is composed of

The reverse conducting semiconductor switches SW1 and SW2 have substantially the same configuration as the reverse conducting semiconductor switches SW1 and SW2 in FIG.
In the configuration of FIG. 9, each of the gates (in order, G1u and G2u) of the switch units S1 and S2 constituting the reverse conducting semiconductor switches SW1 and SW2, respectively, is connected to the control unit 200.
The drain of the switch unit S1 is connected to one end of the capacitor CM1, and the source of the switch unit S1 is connected to the drain of the switch S2. The source of the switch S2 is connected to one end of the capacitor CM2. The other ends of the capacitors CM1 and CM2 are connected to each other to form an AC output terminal AC2.

  The rectifying units D3 and D4 are both composed of rectifying elements such as diodes. In the following description, it is assumed that the rectifiers D3 and D4 are both made of diodes. The anode of the rectifier D3 and the cathode of the rectifier D4 are connected to the AC output terminal AC2, and the cathode of the rectifier D3 is the one end of the capacitor CM1 described above. The anode of the rectifying unit D4 is connected to the above-mentioned one end of the capacitor CM2.

  When the MERS 100u has the configuration shown in FIG. 9, the control unit 200 (i ′) first turns on the reverse conducting semiconductor switch SW2 and turns off SW1, and (ii ′) the phase of the pole U of the AC power supply VS. The reverse conduction type semiconductor switch SW2 is turned off and the operation in which SW1 is turned on after the voltage turns negative is combined into one cycle, and this cycle is set in the MERS 100u with a period substantially equal to the period of the phase voltage of the pole U. What is necessary is just to repeat.

In the MERS 100u of FIG. 9, the capacitor CM1 is electrically connected to the pole U by turning on the reverse conducting semiconductor switch SW1 and turning off SW2. As a result, the AC power supply VS and the capacitor CM1 form a series circuit, and a voltage corresponding to the sum of the phase voltage of the pole U with respect to the reference potential and the voltage across the capacitor CM1 is applied to the pole u. Applied.
On the other hand, the capacitor CM2 is electrically connected to the pole U by turning off the reverse conducting semiconductor switch SW1 and turning on SW2. As a result, the AC power supply VS and the capacitor CM2 form a series circuit, and a voltage corresponding to the sum of the phase voltage of the pole U with respect to the reference potential and the voltage across the capacitor CM2 is present at the pole u. Applied.

Moreover, all of MERS100u, 100v, and 100w may be comprised from the horizontal half bridge type MERS.
For example, when the MERS 100u is composed of a horizontal half-bridge type MERS, the MERS 100u is composed of two reverse conducting semiconductor switches SW2 and SW4 and capacitors CM1 and CM2, as shown in FIG.

The reverse conducting semiconductor switches SW2 and SW4 have substantially the same configuration as the reverse conducting semiconductor switches SW2 and SW4 in FIG. Also in the configuration of FIG. 10, as in the configuration of FIG. 9, each of the gates (in order, G2u and G4u) of the switch units S2 and S4 configuring the reverse conducting semiconductor switches SW1 and SW2 are connected to the control unit 200. ing.
On the other hand, in the configuration of FIG. 10, the drain of the switch unit S2 is connected to one end of the capacitor CM1 to form the AC input terminal AC1, and the source of the switch unit S2 is connected to the source of the switch S4. The drain of the switch S4 is connected to one end of the capacitor CM2 to form an AC output terminal AC2. The other ends of the capacitors CM1 and CM2 are both connected to a connection point between the sources of the switch units S2 and S4.

  When the MERS 100u has the configuration shown in FIG. 10, the control unit 200 (i ″) first turns on the reverse conducting semiconductor switch SW2 and turns off SW4, and (ii ″) the pole U of the AC power supply VS. The reverse conduction type semiconductor switch SW2 is turned off and the operation in which SW4 is turned on after the phase voltage of the current turns negative is combined into one cycle, and this cycle is substantially equal to the cycle of the phase voltage of the pole U. What is necessary is just to make MERS100u repeat.

Moreover, all of MERS100u, 100v, and 100w may be comprised from the one capacitor | condenser horizontal half bridge type MERS.
For example, when the MERS 100u is composed of a one-capacitor horizontal half-bridge type MERS, the MERS 100u is composed of two reverse conducting semiconductor switches SW2 and SW4 and a capacitor CM as shown in FIG.

The reverse conducting semiconductor switches SW2 and SW4 have substantially the same configuration as the reverse conducting semiconductor switches SW2 and SW4 in FIG. Also in the configuration of FIG. 11, the gates (in order, G2u and G4u) of the switch units S2 and S4 constituting the reverse conducting semiconductor switches SW2 and SW4, respectively, are connected to the control unit 200.
On the other hand, in the configuration of FIG. 11, the drain of the switch unit S2 is connected to one end of the capacitor CM to form an AC input terminal AC1, and the source of the switch unit S2 is connected to the source of the switch S2. The drain of the switch S4 is connected to the other end of the capacitor CM to form an AC output terminal AC2.

  Even when the MERS 100u has the configuration shown in FIG. 11, the control unit 200 first performs the operation of turning on the reverse conducting semiconductor switch SW2 and turning off SW4, and the pole U of the AC power supply VS, as in the configuration of FIG. An operation in which the reverse conducting semiconductor switch SW2 is turned off and the switch SW4 is turned on after the phase voltage has turned negative is combined into one cycle. This cycle is substantially equal to the cycle of the phase voltage of the pole U. Can be repeated.

Further, each of the MERSs 100u, 100v, and 100w may be composed of a thyristor Z that is a bidirectional thyristor and a capacitor CM as shown in FIG. 12, for example.
In the configuration of FIG. 12, the first main electrode forming one end of the current path of the thyristor Z forms the AC input terminal AC1, and the second main electrode forming the other end of the current path forms the AC output terminal AC2. The gate of the thyristor Z is connected to the control unit 200, and the capacitor CM is connected in parallel to the current path of the thyristor Z.

  In addition, the control unit 200 in each of the above embodiments may be configured by a dedicated electronic circuit including a comparator, a flip-flop, a timer, and the like.

On the other hand, the configuration of the control unit 200 in each of the above embodiments can also be realized using a normal computer system.
For example, a program for executing the above-described processing performed by the control unit 200 is stored in a CD-ROM (Compact Disk Read-Only Memory), a DVD (Digital Versatile Disk), or other computer-readable recording medium and distributed. And the above-mentioned control part 200 can be constituted by installing this program in a computer.

Further, the program may be stored in a disk device or the like included in a predetermined server device on a communication network such as the Internet, and may be downloaded onto a computer by being superimposed on a carrier wave, for example. Furthermore, the above-described processing can also be achieved by starting and executing a program while transferring it via a communication network.
In addition, when the above functions are realized by sharing an OS (Operating System), or when the functions are realized by cooperation between the OS and an application, only the part other than the OS may be stored in a medium and distributed. Alternatively, it may be downloaded to a computer.

10 Induction motor drive apparatus 100u, 100v, 100w MERS
200 Control unit VM Voltage detection unit AC1 AC input terminal AC2 AC output terminals SW1 to SW4 Reverse conducting semiconductor switches CM, CM1, CM2 Capacitors S1 to S4 Switch units D1 to D4 Reverse conducting units G1 to G4 Gates SGG1u to SGG4u, GG1v ˜SGG4v, GG1w˜SGG4w Gate signal DFT Discrete Fourier transform unit LPF Low pass filter DFR Difference generation unit PI Proportional integration control unit GL Gate logic generation unit VS AC power supply M Induction motors LD1 to LD3 Inductive loads L1 to L3 Inductors R1 to R3 Resistance Z Thyristor

Claims (8)

Obtaining an input AC voltage generated by an external AC power source, generating a compensation voltage corresponding to the phase of the input AC voltage changed by an amount determined by the timing at which a predetermined control signal is supplied to itself, Series compensation means for applying a voltage corresponding to the sum of the input AC voltage and the compensation voltage to an external induction motor;
Control means for supplying the control signal to the series compensation means;
Load voltage detection means for detecting the amount of load voltage applied from the series compensation means to the induction motor, and generating a signal indicating the detected amount of the load voltage,
The control means includes
The signal generated by the load voltage detection means is acquired, the amount of the fundamental component of the load voltage indicated by the signal is specified, and the amount of the specified fundamental component is converged to a predetermined value. Timing determining means for determining timing;
Control signal supply means for supplying the control signal to the series compensation means at a timing determined by the timing determination means,
Induction motor control device. Each of the series compensation means is a switch that has a current path, and that turns on and off each current path in response to a control signal supplied to each of the series compensation means. First to fourth switches that conduct substantially only in one direction from the predetermined end of the current path when turned off, and the other end of the current path of the first switch is one end. And a capacitor connected to the other end of the current path of the third switch, the other end connected to the one end of the current path of the second switch and the one end of the current path of the fourth switch; The one end of the current path of the first switch and the other end of the current path of the second switch are connected to the AC power source, and the one end of the current path of the third switch and Current path of the fourth switch Are those whose serial other end the induction motor is connected,
The control signal supply means applies the first control signal for turning on the current paths of the second and third switches and turning off the current paths of the first and fourth switches at the first timing. The second control signal is supplied to each control terminal of the first to fourth switches, and the second control signal for turning off the current paths of the second and third switches and turning on the current paths of the first and fourth switches. 2 is supplied to each control terminal of the first to fourth switches at the timing of 2.
The induction motor control device according to claim 1. Each of the series compensation means is a switch that has a current path, and that turns on and off each current path in response to a control signal supplied to each of the series compensation means. First and second switches that conduct substantially only in one direction from the predetermined end of the current path when turned off, and each current path is in one direction from the predetermined end to the other end First and second rectifying elements that are substantially conductive only to each other, and one end connected to the other end of the current path of the first switch and the other end of the current path of the first rectifying element. And a second capacitor having one end connected to the one end of the current path of the second switch and the one end of the current path of the second rectifying element. The one end of the current path of the switch and the second switch. The other end of the current path of the first rectifier element, the other end of the current path of the second rectifier element, and the other of the first capacitor. An end and the other end of the second capacitor are coupled to each other and connected to the induction motor;
The control signal supply means applies the first control signal for turning on the current path of the second switch and turning off the current path of the first switch at the first timing. The second control signal for turning off the current path of the second switch and turning on the current path of the first switch at the second timing. To be supplied to each control end of the switch,
The induction motor control device according to claim 1. p is an integer of 3 or more, the AC power source is a p-phase AC power source, the induction motor is a p-phase induction motor,
The induction motor control device includes p series compensation means, each of the series compensation means being connected to a pole of each phase of the AC power source in a one-to-one relationship, and of the induction motor Connected to the poles of each phase on a one-to-one basis,
The load voltage detection means detects the amount of the load voltage of each phase applied from the series compensation means to the induction motor, and generates a signal indicating the detected load voltage of each phase,
The timing determination means specifies an average amount of effective values of fundamental wave components of the load voltages of the n phases indicated by the signal generated by the load voltage detection means, and the specified average amount is a predetermined value Determining the timing for each of the series compensation means to converge to
The induction motor control device according to any one of claims 1 to 3. The timing determination means calculates an average amount of effective values of fundamental wave components in a section corresponding to substantially one cycle of p of the load voltages of the p phases indicated by the signal generated by the load voltage detection means. Specifying and determining the timing for each of the series compensators so that the specified average amount converges to a predetermined value;
The induction motor control device according to claim 4. The timing determining means includes
Means for specifying (p · 2 ⁿ ) virtual load voltage values, where n is a natural number, based on the load voltage values of the n phases indicated by the signal generated by the load voltage detection means;
An average amount of effective values of fundamental wave components in a section substantially corresponding to {1 / (p · 2 ⁿ )} periods of each specified load voltage is specified, and the specified average amount is a predetermined value Means for determining the timing to converge to
The induction motor control device according to claim 4. Obtaining an input AC voltage generated by an external AC power source, generating a compensation voltage corresponding to the phase of the input AC voltage changed by an amount determined by the timing at which a predetermined control signal is supplied to itself, A series compensation unit that applies a voltage corresponding to the sum of the input AC voltage and the compensation voltage to an external induction motor, and detects the amount of load voltage applied from the series compensation unit to the induction motor; An induction motor control device that controls the induction motor via a device comprising a load voltage detection unit that generates a signal indicating the amount of the detected load voltage,
The signal generated by the load voltage detection unit is acquired, the amount of the fundamental component of the load voltage indicated by the signal is specified, and the amount of the specified fundamental component is converged to a predetermined value. Timing determining means for determining timing;
Control signal supply means for supplying the control signal to the series compensator at a timing determined by the timing determination means,
Induction motor control device. Obtaining an input AC voltage generated by an external AC power source, generating a compensation voltage corresponding to the phase of the input AC voltage changed by an amount determined by the timing at which a predetermined control signal is supplied to itself, A series compensation unit that applies a voltage corresponding to the sum of the input AC voltage and the compensation voltage to an external induction motor, and detects the amount of load voltage applied from the series compensation unit to the induction motor; An induction motor control method for controlling the induction motor via a device comprising a load voltage detection unit that generates a signal indicating the amount of the detected load voltage,
The signal generated by the load voltage detection unit is acquired, the amount of the fundamental component of the load voltage indicated by the signal is specified, and the amount of the specified fundamental component is converged to a predetermined value. A timing determination step for determining timing;
A control signal supply step for supplying the control signal to the series compensator at a timing determined in the timing determination step;
Induction motor control method.

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