JPH07245958A - Control method of current resonance type inverter - Google Patents

Abstract

PURPOSE:To generate output currents having a small oscillation component while generating current pulses, in which magnitude and a period are equalized from a resonance circuit, in a current resonance type inverter. CONSTITUTION:When current pulses Ip from a resonance circuit 12 are distributed to the power lines La-Lc of each phase through an inverter circuit 12, a controller 18 forms a plurality of regions for one period of one reference signal in reference signals set at every phase, specifies the power line of one phase at every region, and reduces the current pulse density of a phase when the absolute value of the output currents of the phase is made larger than that of the reference signal of the phase. On the contrary, the controller 18 fixes the current pulse density of the phase when the absolute value of the output currents of the phase is made smaller than that of the reference signal of the phase, and controls the current pulse density of the phases except the phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter, and more particularly to a method for controlling a current resonance type inverter.

[0002]

2. Description of the Related Art Conventionally, an inverter is often used as a circuit for driving various electric devices such as induction motors used in various electric appliances. Recently, it has been adopted for driving a three-phase induction motor for running an electric vehicle. In particular, current resonance type inverters have been receiving attention because they have little radio noise. Then, various methods have been proposed for controlling the output voltage supplied to the load in controlling the inverter (eg, TG Harbetler and DMDivan, "Perform
ance of a New Descrete Pulse-Modulated Current Reg
ulator ", IEEE Trans.Ind.Appl., vol.25, no.6, Nov. / De
c.1989.) and good results have been obtained.

By the way, vector control is attracting attention for induction motors. In this case, instead of controlling the output voltage, the current flowing through the electric motor must be controlled, that is, current control. Therefore, various research reports (eg Y. Murai and TALipo. "High Fre.
quency Series Resonant DC Link Power Conversion ", I
EEE IAS Annual Meeting Conference Record, 1988, pp.7
72-779.) Has been made. FIG. 5 shows the current resonance type inverter system.

In FIG. 5, an input converter 11 composed of four thyristors outputs a direct current power source E to a resonance circuit 12 as a pulse signal of a positive voltage at a predetermined interval. The resonance circuit 12 resonates based on the pulse signal input via the input converter 11 to generate the current pulse Ip.
The current pulse Ip has three upper arm thyristors a to c,
The lower arm is output to the inverter 13 including three thyristors -a to -c.

Each of the thyristors a to c, -of the inverter 13
The controllers a to -c are appropriately turned on (ignited) by a controller (not shown). Further, the turned-on thyristor is turned off when the current pulse Ip disappears.

Therefore, for example, when the upper arm thyristor a is repeatedly controlled to be turned on and off for a certain period of time and then the lower arm thyristor a is repeatedly turned on and off for the same period, the a-phase power line La is connected to the power line La. After the number of positive current pulses Ip that are turned on is output, the same number of negative current pulses Ip are output. Also, the thyristor b of the upper arm of the b-phase power line Lb
And the lower arm thyristor-b is 120 degrees out of phase with respect to the thyristors a and -a on the a-phase power line La, and the same on / off control is performed. Current pulse Ip is output. Further, when the thyristor c of the upper arm and the thyristor -c of the lower arm of the c-phase power line Lc are shifted on the a-phase power line La by 240 degrees with respect to the thyristors a and -a, and are similarly turned on / off, The brass and the negative current pulse Ip which are out of phase with each other by 240 degrees are output.

A filter capacitor C is provided between the power lines La to Lc of the inverter 13. The plus and minus current pulses Ip output from the inverter 13 to the power lines La to Lc of each phase by the filter capacitor C are smoothed into a sine wave and the three phase output currents ia, i.
b and ic are output to a load (not shown) such as a three-phase induction motor. The output waveform control of the output currents ia, ib, ic is controlled by changing the number of current pulses Ip (that is, pulse density). The control of the pulse density is performed based on the ON control of the upper arm thyristors a to c and the lower arm thyristors a to c provided in the inverter 13, and the ON control is performed by the controller.

This control method is performed as follows.
FIG. 7 shows a current control loop performed in the controller. The calculator 21 subtracts the a-phase reference current ia ^* (target value) by the a-phase output current ia (current value) to obtain the deviation Δi.
a (= ia ^* -ia) is calculated. In addition, the calculator 22 calculates the b-phase reference current ib ^* (target value) as the b-phase output current ib.
The difference Δib (= ib ^* -i
Find b). The reference currents ia ^* and ib ^* are sine waves having the same amplitude value with a phase difference of 120 degrees as shown in FIG. 6, and the reference currents ia ^* and ib ^* are the target of the a phase and the b phase, respectively. The output current is controlled to be the same. Also, c
The phase reference current ic ^* (= -ia ^* -ib ^* ) is out of phase with the reference current ia ^* by 240 degrees as shown in FIG.

The deviations Δia and Δib are respectively calculated by the integrator 2
It is output to the differentiators 25 and 26 while being output to the third and fourth. Then, the deviations Δia, Δib integrated by the integrators 23, 24 and the deviations Δia, Δib differentiated by the differentiators 25, 26 are added to the adders 27, 28, respectively.

Then, the computing units 27 and 28 have deviations Δia,
The values obtained by adding Δib and the integrated and differentiated deviations Δia and Δib are the error signals ea and eb of the a-phase and the b-phase, respectively.
Output as. In addition, the c-phase error signal ec (= -ea
-Eb) is obtained by outputting both the a-phase and b-phase error signals ea and eb to the calculator 28.

The obtained error signals ea, eb, ec
Based on the above, the output current of the phase smaller than the reference current and the output current of the phase larger than the reference current among the output currents ia to ic are determined. Then, for example, the number of times the upper and lower arm thyristors of the phase are turned on and off is increased so as to increase the pulse density of the phase so that the output current of the smallest phase approaches the reference current. Further, the number of times the thyristors of the upper and lower arms of the phase are turned on / off is reduced so that the pulse density of the phase is lowered so that the output current of the largest phase approaches the reference current. That is, the control of this number of times determines for each current pulse Ip which thyristor is turned on (ignition) based on the error signals ea, eb and ec at that time, and the thyristor determined based on the determination result. Is turned on (ignition) to control the pulse density.

In this way, by controlling the pulse density output from the inverter 13 based on the error signals ea to ec, the output waveforms of the output currents ia to ic of the respective phases are controlled. Regarding the control of this pulse density, Y. Murai and TA Lipo. "High Fre
quency Series Resonant DC Link Power Conversion, ",
IEEE IAS Annual Meeting Conference Record, 1988, pp.
See 772-779. For a clearer understanding.

[0013]

By the way, an output current ia is applied to a load including an inductance like a three-phase induction motor.
When controlling ˜ic, even if the density of the current pulse Ip is controlled by adding the respective differential value and integrated value to the deviation between the target value and the current value in the current control loop, it is not immediately reflected in the output current. The output currents ia-ic caused vibration due to the delay.

In other words, in this control method, a thyristor that always fires to minimize the phase having the largest amplitude error is selected. The thyristor of the phase to be ignited is not uniquely selected and ignited. Further, since the current of the phase having a large amplitude error is controlled and the control is not reflected immediately, when viewed from the resonance circuit 12,
The resonant circuit is connected to a load that constantly changes greatly and controls the current. Therefore, stable current control cannot be expected for the resonance circuit 12 that controls a load that changes greatly from time to time. As a result, as shown in FIG. 8, the voltage between the terminals of the resonance capacitor in the resonance circuit 12 and the current pulse Ip output from the resonance circuit 12 are not uniform in size and period, and the output waveform cannot be controlled with high accuracy. There was a problem.

The present invention has been made in order to solve the above problems, and its purpose is to generate an output current with less oscillating components and to generate a current pulse having a uniform size and cycle as seen from the resonance circuit. It is an object of the present invention to provide a control method of a current resonance type inverter that can be realized.

[0016]

In order to achieve the above-mentioned object, the invention of claim 1 distributes a current pulse from a resonance circuit to a power line of each phase through an inverter circuit, and the current pulse density is used as a reference signal. In the method of controlling the current resonance type inverter, which is performed based on the deviation of the output current of the phase, the period of one reference signal of the reference signals of each phase is divided into a plurality of periods, and the division is performed. Each of the plurality of periods is set as a region, the region at that time is determined based on the one reference signal, and the power line of one phase is specified for each region, and the absolute value of the output current of the phase is the reference signal. Is larger than the absolute value of the output current, and when the absolute value of the output current is larger, the current pulse supplied to the specified phase is short-circuited to reduce the pulse density so that the output current becomes smaller. When towards the absolute value of the output current is small, and to control the current pulse density of the phases other than the phase identified by fixing the current pulse density of the identified phases.

According to a second aspect of the present invention, in the first aspect of the invention, the power line has three phases, and the reference signals are 120 degrees apart from each other.
It is a sine wave whose phase is out of phase, and is equally divided into 6 for one cycle of one reference signal of each phase, and the power line of one phase is specified for each of the 6 divided areas. Regarding the phase, for each reference signal, the phase of the reference signal whose value is different from the value of only the other two reference signals is defined as the specific phase.

According to a third aspect of the present invention, a current pulse from a series-type resonance circuit in which a resonance capacitor and a resonance coil are connected in series is distributed to three-phase power lines via switching elements on the upper and lower arms of an inverter circuit, and a filter is provided. When outputting the output current obtained by smoothing with the capacitor to the 3-phase induction motor, create the current pulse density based on the rotation frequency of the 3-phase induction motor and the torque command value that makes the 3-phase induction motor a desired torque. In the control method of the current resonance type inverter, which is performed based on the deviation between the sine wave reference signals which are 120 degrees out of phase with each other and the output current of the phase,
One period of one reference signal of each phase is equally divided into six, and the divided six regions are judged at each time based on the one reference signal. For each reference signal at that time, the phase of the reference signal whose positive and negative values are different from the values of the other two reference signals is defined as a specific phase, and the absolute value of the output current of that phase is the absolute value of the reference signal. If the absolute value of the output current is larger, the switching elements of the upper and lower arms of the phase are operated to short-circuit the current pulse supplied to the phase so that the output current becomes smaller. When the pulse density is reduced and the absolute value of the output current is smaller, the current pulse density of the specified phase is fixed and the current pulse density of the phase other than the specified phase is switched by the switching element of the phase other than the specified phase. To control .

According to a fourth aspect of the present invention, when the current pulse from the resonance circuit is distributed to the power line of each phase through the inverter circuit, the current pulse density is controlled based on the deviation between the reference signal and the output current of the phase. In the current resonance type inverter control method as described above, one cycle of one reference signal of the reference signals of each phase is divided into period units in which the absolute value of the reference signal of a specific phase is continuously maximized. , Each of the divided multiple periods is specified as an area, and the power line that maximizes the absolute value of the reference signal is specified for each area. If the reference signal of the specified power line is positive, the specified power line is connected. If the reference signal is negative, turn on the switching element of the lower arm of the inverter circuit to which the specified power line is connected. In the on decision, if the switching elements of the upper arm ON operation is determined by selecting one of the switching elements of the lower arm to be turned on,
When the ON operation of the switching element of the lower arm is decided, one switching element of the upper arm to be turned ON is selected to control the current pulse density so that the current of each phase approaches each reference value. did.

[0020]

According to the present invention, when the absolute value of the output current of the phase is larger than the absolute value of the reference signal, the current pulse supplied to the specified phase is reduced so that the output current becomes small. Short circuit to positively reduce pulse density. On the contrary, when the absolute value of the output current is smaller, the current pulse density of the specified phase is fixed so that it is not actively controlled. In other words, the output current is always actively controlled only in the direction of decreasing the value. As a result, the output current is large, but vibration is less likely to occur, as compared with the case where the control is performed in the increasing direction. In addition, a plurality of regions are set, and in the control in the set regions, the phase to be controlled is specified. Therefore, the control is simplified and the resonant circuit is less susceptible to unexpectedly large load fluctuations.

According to the fourth aspect of the present invention, the absolute value of one of the plurality of reference signals or the area where the absolute value is continuously maximized is set,
In the control in the set area, the phase to be controlled is specified. Therefore, the control is simplified and the resonant circuit is less susceptible to unexpectedly large load fluctuations.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment embodying the present invention will now be described with reference to FIGS.
It will be described with reference to FIG. FIG. 1 shows a current resonance type inverter system. For the sake of convenience of explanation, the same components as those shown in FIG.

The resonance circuit 12 is composed of a resonance capacitor C0, a resonance coil L0 and a coil Ld. The resonance capacitor C0 and the resonance coil L0 are connected in series, the other end of the resonance capacitor C0 is connected to the plus terminal of the input converter 11, and the other end of the resonance coil L0 is the inverter 1
3 is connected to the positive terminal. The coil Ld is connected in parallel with the resonance capacitor C0.

Then, a pulse signal of a positive voltage of a predetermined cycle generated by controlling the firing of the thyristors g, h, -g, -h of the upper and lower arms of the input converter 11 is input to the resonance circuit 12. That is, the input converter 11 outputs the pulse signal which is the basis of the current pulse Ip.

The resonance capacitor C is generated by this pulse signal.
A resonance current flows through the resonance coil L0 and the resonance coil L0, and as shown in FIG. 4, a current pulse Ip is generated for the terminal voltage VC0 of the resonance capacitor C0. A current flows through the coil Ld to charge the resonance capacitor C0 while the thyristors a to c and -a to -c of the inverter 13 at the next stage are turned off. By this charging, the resonance capacitor C0 can output the current pulse Ip by the next ignition of the inverter 13.

On the other hand, the power lines La, Lb, Lc of each phase are 3
It is connected to the phase induction motor M. And the motor M
Is controlled based on the output currents ia, ib, ic output from the inverter 13 and smoothed by the filter capacitor C.

Current detectors 15 and 16 are provided on the a-phase and b-phase power lines La and Lb, and the current detectors 15 and 16 detect the output currents ia and ib at the respective times. Also, the motor M
Is provided with a rotation detector 17, and the rotation detector 17 detects a rotation frequency of the motor M at each time (hereinafter referred to as an actual rotation frequency).

Although not shown, the resonance capacitor C0
, Each of the filter capacitors C and the DC power source E are provided with a voltage detector for detecting the voltage of the capacitors C0, C and the power source voltage, respectively, and each detection signal is supplied to the controller 18
Is output to. Further, although not shown, the coil Ld is provided with a current detector for detecting a current flowing through the coil Ld, and the detection signal is output to the controller 18.

The controller 18 controls ON (ignition) of the thyristors a to c and -a to -c of the inverter 13 and the thyristors g to h and -g to -h of the input converter 11. The controller 18 inputs the detection signal at each time from the current detectors 15 and 16 and the position detector 17. The controller 18 includes the current detectors 15 and 16 and the position detector 1.
Based on the detection signal from 7, the output current i
The output waveforms of a, ib and ic are controlled.

Output currents ia, i by the controller 18
The output waveform control of b and ic is executed by the processing shown in FIG. The controller 18 uses the reference signal generation circuit section 18a as a reference for the a-phase and the b-phase based on the actual rotation frequency signal from the rotation detector 17 and the torque command value that commands the torque of the motor M from an external device, not shown. Signals ia ^* , ib
^* As a reference signal generating means for generating a angle signal θ relative to the a-phase reference signal ia ^*.

The a-phase and b-phase reference signals ia ^* and ib ^* are sine waves, and the frequency of the motor M obtained by a known method by adding / subtracting the actual rotation frequency and the slip frequency determined by the torque command value. It is a frequency for commanding torque. The amplitude values of the a-phase and b-phase reference signals ia ^* and ib ^* are values obtained by a known method using the torque command value.
That is, it can be said that the reference signals ia ^* and ib ^* are target output currents of the a-phase and b-phase output currents ia and ib.

Then, the reference signal generating circuit portion 18a generates a b-phase reference signal ib ^* which is a sine wave delayed by 120 degrees with respect to the reference signal ia ^* as shown in FIG. Incidentally, the sine wave of the c-phase reference signal ic ^{* is} a sine wave delayed by 240 degrees with respect to the reference signal ia ^* as shown in FIG. 3, but is not generated in the reference signal generation circuit section 18a.
Further, the reference signal generation circuit section 18a generates and outputs the angle signal θ based on the reference signal ia ^* .

When the a-phase and b-phase reference signals ia ^* and ib ^* are generated, the a-phase and b-phase detected by the current detectors 15 and 16 are detected.
With the phase reference signals ia and ib, the controller 18 causes the error signal generation circuit section 18b to output the error signals ea, eb, and
Find ec. The current control loop of the error signal generation circuit section 18b for obtaining the error signals ea, eb, ec is performed by the same method as the conventional current control loop shown in FIG. Therefore, the description of the error signal generation circuit section 18b is omitted for convenience.

The error signals ea, eb and ec generated by the error signal generation circuit section 18b are the thyristor selection circuit section 18c.
Is output to. The thyristor selection circuit unit 18c uses six error signals ea, eb, and ec and the angle signal θ of the reference signal generation circuit unit 18a to generate six thyristors a to c and -a to -c.
This is a thyristor selection circuit for selecting which thyristor to fire.

This selection is performed as shown in FIG. That is, one cycle 360 based on the cycle of the reference signal ia ^*
Six areas Z1 to Z6 are set at intervals of 60 degrees. The first area Z1 is in the range of 0 to 60 degrees, and the second area Z2 is 60 degrees.
Degree to 120 degrees, the third region Z3 is 120 degrees to 180 degrees
Degree range, the fourth region Z4 is in the range of 180 degrees to 240 degrees,
The fifth zone Z5 is in the range of 240 to 300 degrees, and the sixth zone Z5
6 is set in the range of 300 degrees to 360 degrees (0 degree). As shown in FIG. 3, the division of these six regions Z1 to Z6 is performed with respect to the value of the reference signal having the maximum or minimum value and the reference signal having the maximum or minimum value, respectively. And the values of the other two reference signals have positive and negative opposite values, respectively. Then, the determination of each of the areas Z1 to Z6 by the thyristor selection circuit portion 18c is made based on the angle signal θ.

The thyristor selection circuit portion 18c is provided in each area Z1.
A specific thyristor (hereinafter referred to as a specific thyristor) which is always the target of ignition for each Z6 and each error signal ea, eb,
A thyristor to be fired (hereinafter referred to as a selected thyristor) is selected based on the magnitude of ec.

In the first region Z1, the specific thyristor is the b-phase thyristor-b provided on the lower arm. When the error signal eb is eb ≧ 0, the selected thyristor is the thyristor b provided in the phase b of the upper arm. Also, eb <0
In the case of, the error signals ea and ec are compared. And
When ec ≧ ea, the thyristor c provided in the c-phase of the upper arm is set as the selected thyristor, and when ec <ea, the thyristor a provided in the a-phase of the upper arm is set as the selected thyristor to be fired.

In the second region Z2, the specific thyristor is the a-phase thyristor a provided on the upper arm. When the error signal ea is less than ea, the selected thyristor is the thyristor-a provided in the phase a of the lower arm. Also, ea ≧ 0
In the case of, the error signals eb and ec are compared. And
When ec ≧ eb, the thyristor b provided in the b-phase of the lower arm is set as the selected thyristor, and when ec <eb, the thyristor c provided in the c-phase of the lower arm is set as the selected thyristor to be fired.

In the third region Z3, the specific thyristor is the c-phase thyristor-c provided in the lower arm. Further, the selected thyristor is the thyristor c provided in the c phase of the upper arm when the error signal ec is ec ≧ 0. Also, ec <0
In the case of, the error signals ea and eb are compared. And
In the case of ea ≧ eb, the thyristor a provided in the a-phase of the upper arm is set as the selected thyristor, and in the case of ea <eb, the thyristor b provided in the b-phase of the upper arm is set as the selected thyristor for firing.

In the fourth region Z4, the specific thyristor is the b-phase thyristor b provided on the upper arm. When the error signal eb is eb <0, the selected thyristor is the thyristor-b provided in the phase b of the lower arm. Also, eb ≧ 0
In the case of, the error signals ea and ec are compared. And
When ea ≧ ec, the thyristor c provided in the c-phase of the lower arm is set as the selected thyristor, and when ea <ec, the thyristor-a provided in the a-phase of the lower arm is set as the selected thyristor to be fired.

In the fifth region Z5, the specific thyristor is the a-phase thyristor-a provided on the lower arm. When the error signal ea is ea ≧ 0, the selected thyristor is the thyristor a provided in the phase a of the upper arm. Also, ea <0
In the case of, the error signals eb and ec are compared. And
When eb ≧ ec, the thyristor b provided in the b-phase of the upper arm is set as the selected thyristor, and when ea <ec, the thyristor c provided in the c-phase of the upper arm is set as the selected thyristor to be fired.

In the sixth region Z6, the specific thyristor is the c-phase thyristor c provided on the upper arm. When the error signal ec is eb <0, the selected thyristor is the thyristor-c provided in the c-phase of the lower arm. Also, ec ≧ 0
In the case of, the error signals ea and eb are compared. And
When eb ≧ ea, the thyristor-a provided in the a-phase of the lower arm is set as the selected thyristor, and when eb <ea, the thyristor-b provided in the b-phase of the lower arm is set as the selected thyristor to be fired.

The data of the three firing patterns set for each of the areas Z1 to Z6 are stored in the storage means of the controller 18 in advance. When the specific thyristor and the selected thyristor are selected in the thyristor selection circuit unit 18c, the controller 18 outputs an ignition signal to the selected thyristor to turn on the thyristor.
The timing of outputting the ignition signal is performed by a known method, based on the voltage of the resonance capacitor C0, the voltage of the filter capacitor C and the voltage of the DC power source E. That is,
When the resonance capacitor C0 is ready to output the next current pulse Ip, the controller 18 outputs a firing signal to the selected upper and lower arm thyristors. Then, when one current pulse Ip is output to the power line through the fired thyristor and then turned off, the next thyristor to be fired is selected and fired in the same manner as described above. .

Further, the controller 18 is the input converter 1
The thyristors g, h, -g, -h provided in No. 1 are ignition controlled. Selection of which of the thyristors g, h, -g and -h is to be ignited is performed by a known method and is selected by the current flowing through the coil Ld. Similarly, the ignition timing is also determined by a known method, and is determined by the respective voltages of the resonance capacitor C0, the filter capacitor C and the DC power source E.

Next, the operation of the current resonance type inverter system configured as described above will be described. Now, when the motor M is driven by the output currents ia, ib, ic, the controller 18 outputs the current pulse Ip to the inverter 1
The following processing is executed every time the data is output via the No. 3. The reference signal generation circuit unit 18a outputs the a-phase and b-phase reference signals ia ^* and ib ^* to the error signal generation circuit unit 18b based on the actual rotation frequency and the torque command value, and also outputs the angle signal θ to the thyristor selection circuit unit. 18c. The error signal generating circuit portion 18b receives the reference signals ia ^* , ib ^* and the output current i.
The error signals ea, eb, and ec of each phase are generated with a and ib, and are output to the thyristor selection circuit unit 18c. The thyristor selection circuit unit 18c determines which region Z1 to Z6 is present based on the angle signal θ. If it is in the first region Z1, the thyristor selection circuit section 18c makes the b-phase thyristor-b provided in the lower arm the specific thyristor as shown in FIG. That is, since the b-phase reference signal ib ^* has a negative value including the minimum value in the first region Z1, the b-phase power line Lb needs to have a large value to draw current from the motor M. The thyristor-b is a specific thyristor.

Next, the thyristor selection circuit section 18c determines whether the error signal eb is eb ≧ 0, and whether the b-phase output current ib is smaller than the reference signal ib ^* . And eb ≧ 0
In this case, the thyristor b provided in the phase b of the upper arm is the selected thyristor. That is, the output current ib of the b phase at this time
Is smaller than the reference signal ib ^* , the current pulse Ip is passed through the b-phase power line Lb to output the output current ib as the reference signal ib ^*.
It is necessary to approach

When eb <0 (when the output current ib is larger than the reference signal ib ^* ), the error signal ea and the error signal ec are compared to determine whether ec ≧ ea, and the larger error signal The upper arm thyristor provided in the phase corresponding to is selected as the thyristor. That is, the error signal ea,
When both ec are positive values (both reference signals are larger values), a thyristor having a larger value is used. In this case, the reference currents ia ^* and ic ^* are both output current i.
This is because the value is larger than a and ic, and it is necessary to flow the current pulse Ip to the larger phase and average the error to a smaller value as a whole. Similarly, the error signals ea and ec
When one of the two has a positive value and the other has a negative value, the thyristor of the phase having the larger value is used.

When the error signals ea and ec are both negative (both the reference signals ia ^* and ic ^* are smaller than the output currents ia and ic), a thyristor of a phase whose absolute value is smaller is used. In this case, if the current pulse Ip is made to flow in a phase having a large absolute value (the ratio in which the output current is larger than the reference signal is large), the error is further increased. Therefore, the current pulse Ip is made to flow in a phase having a small absolute value to increase the error. This is because it is necessary to suppress

When the thyristor selection circuit section 18c selects the specific thyristor b and the selected thyristor a, b or c in the above judgment processing, the controller 18 simultaneously fires the selected thyristors at a predetermined timing to generate one current. The pulse Ip is passed through the power line of the corresponding phase.

Thereafter, each time one current pulse Ip is passed,
Performing the same processing as above, selecting the specific thyristor b and the thyristor of the upper arm and simultaneously igniting them is performed in the first area Z1.
Repeat until is over.

Next, when entering the second area Z2, the thyristor selection circuit section 18c makes the a-phase thyristor a provided in the upper arm the specific thyristor as shown in FIG. That is, since the a-phase reference signal ia ^* is a positive value including the maximum value in the second region Z2, the a-phase power line La needs to flow a large value of current to the motor M. Therefore, the a-phase thyristor is required. a is a specific thyristor.

Next, the thyristor selection circuit section 18c determines whether the error signal ea is ea <0 and whether the output current ia of the a phase is larger than the reference signal ia ^* . And ea <0
In this case, the thyristor-a provided in the phase a of the lower arm is used as the selected thyristor. That is, the a-phase output current i at this time
Since a is larger than the reference signal ia ^* , the a-phase power line Lb
This is because it is necessary to reduce the amount of current flowing to the output terminal, that is, to short-circuit the output current ia to bring it closer to the reference signal ia ^* .

When ea ≧ 0 (the output current ia is the reference
Signal ia^*Error signal eb and the error
It is judged by comparing with the signal ec whether ec ≧ eb, and it is larger.
The size of the lower arm provided in the phase corresponding to the other error signal.
The lister is selected as the thyristor. That is, the error signals eb,
When both ec are positive values (both are reference signals ib^*Ic ^*
Smaller output currents ib and ic), smaller values
It becomes the thyristor of the phase. In this case, the value is large
Phase current (the ratio of the output current is smaller than the reference signal is large)
If the current of the force line is pulled out, the error becomes larger.
Therefore, the current of the power line of the phase with a small value should be pulled out.
This is because it is necessary to suppress the expansion of the error.

When the error signals ea and ec are both negative (both the output currents ia and ic are larger than the reference signals ia ^* and ic ^* ), the thyristor of the phase whose absolute value is larger is used. In this case, both the output current ib, ics the reference signal ib ^*, ics ^* because less negative value, it is necessary to reduce the error closer to the reference signal so as to disconnect the current large phase power line of the absolute value Because. Similarly, when one of the error signals ea and ec has a positive value and the other has a negative value, a thyristor having a phase having a small value is used.

When the thyristor selection circuit section 18c selects the specific thyristor a and the selected thyristor -a, -b or -c in the above judgment processing, the controller 18 simultaneously ignites the selected thyristor at a predetermined timing. One current pulse Ip is passed through the power line of the corresponding phase.

Thereafter, each time one current pulse Ip is passed,
The same processing as above is performed, and the operation of selecting the specific thyristor a and the thyristor of the upper arm and simultaneously firing them is repeated until the second zone Z2 passes.

Next, when the third area Z3 is entered, the thyristor
The selection circuit section 18c is provided on the lower arm as shown in FIG.
The c-phase thyristor-c is changed to a specific thyristor. That is,
The third area Z3 has the same meaning as described in the first area Z1.
At C phase reference signal ic ^*Is a negative value including the minimum value
Therefore, the C-phase power line LC has a large value from the motor M.
The current must be drained and therefore the C-phase thyristor
-C is a specific thyristor.

Also, in the selection of the selected thyristor, in the third region Z3, any one of the three thyristors a to c of the upper arm is selected as the selected thyristor by the same method as the purpose described in the first region Z1. .

Next, when entering the fourth region Z4, the thyristor selection circuit portion 18c makes the b-phase thyristor b provided in the upper arm the specific thyristor as shown in FIG. That is, as in the case of the second area Z2, since the b-phase reference signal ib ^* is a positive value including the maximum value in the fourth area Z4, the b-phase power line Lb is a large value to the motor M. Since it is necessary to pass a current, the b-phase thyristor b is a specific thyristor.

In the selection of the selected thyristor, in the fourth area Z4, any one of the three thyristors -a to -c of the lower arm is selected as the selected thyristor by the same method as described in the second area Z2. select.

Similarly, in the case of the fifth region Z5, the specific and selected thyristor is selected for the same purpose as in the first and third regions Z1 and Z3. In the case of the sixth area Z6, the second and fourth areas
A specific and selected thyristor is selected for the same purpose as in the areas Z2 and Z4.

Thus, in this embodiment, the reference signal ia
^* Is divided every 60 degrees, and in each of the divided areas Z1 to Z6, three combinations of firing thyristors are set. Therefore, there is little data of the thyristor that fires in each of the areas Z1 to Z6, and the controller 1
An increase in the storage capacity of the storage means in 8 can be suppressed. Moreover, in each of the areas Z1 to Z6, there are only three combinations of thyristors that are fired, so that the control is very simple and the processing speed can be increased.

In each of the areas Z1 to Z6, when the amplitude value of one reference signal has a positive or negative value, the other two reference signals both have positive and negative opposite values with respect to the value of one reference signal. As described above, the reference signal ia ^* is set as a reference for every 60 degrees. Therefore, the specific thyristor of the upper or lower arm that is always fired can be easily selected, and if the specific thyristor is the lower arm, the upper arm thyristor, and if the specific thyristor is the upper arm, the lower arm. The thyristor can be selected as a thyristor.
The design of control data is very easy and the design mistakes are reduced.

Further, in each of the regions Z1 to Z6, a thyristor of a phase corresponding to one reference signal having a positive / negative opposite value to the values of the other two reference signals (the lower arm if the reference signal is negative). Thyristor, if positive, the upper arm thyristor) was the target of ignition as a specific thyristor. And
If the upper arm thyristor is a specific thyristor, current is supplied to the power line of the phase.

At this time, when the output current is larger than the reference signal, the thyristor of the lower arm corresponding to the reference signal is ignited and short-circuited as the selected thyristor. Therefore, the output current decreases and approaches the reference signal, and the error can be reduced.

On the contrary, when the output current is smaller than the reference signal, the thyristor of the lower arm corresponding to the reference signal is not ignited and short-circuited as the selected thyristor, and the lower arm of the two phases which do not correspond to the reference signal. One of the thyristors was the target of the selected thyristor. Therefore,
Since the current supplied to the power line is not short-circuited, the output current is controlled on the basis of the current supplied to the power line after being ignited by the specific thyristor.

At this time, the selected thyristor is selected according to the magnitudes of the error signals of the other two phases. That is,
When both error signals have a positive value (both the output current is smaller than the reference signal), the phase of the thyristor has a smaller value. Therefore, the current of the power line of the phase whose output current is smaller than the reference signal is large, that is, the current is not short-circuited, and the error of the phase is not further expanded. Further, when both error signals are negative (both the output current is larger than the reference signal), the thyristor of the phase whose absolute value is larger is used. Therefore, the electric current of the power line of the phase whose absolute value is large is pulled out, that is, short-circuited,
The output current with a large error approaches the reference signal, and the error can be reduced. Similarly, when one of the error signals has a positive value and the other has a negative value, the same applies to a thyristor having a smaller phase.

In each region Z1 to Z6, when the absolute value of the amplitude value of the output current of the phase controlled by the specific thyristor is larger than the reference signal, the selected thyristor is short-circuited so that the absolute value becomes smaller. Let me control it positively. On the contrary, when the absolute value of the amplitude value of the output current is smaller than that of the reference signal, the control that positively increases the absolute value is not performed. That is, the control for reducing the output current value, that is, the control for suppressing the output current value is performed. Therefore, when the value of the output current is controlled in a large direction to approach the reference signal, the output current overshoots and undershoots, causing vibration, but in the case of this embodiment, it is difficult to occur and a stable output waveform is generated. can do.

Further, in the conventional case, the thyristor of the phase having a large error is always controlled as the ignition target, but in the present embodiment, it is not always the ignition target, and each region Z1 is always controlled.
A thyristor within a predetermined range is selected for each Z6. Therefore, when viewed from the resonance circuit 12, it is difficult to be affected by a large load change. As a result, the resonance circuit 12 can perform a stable operation, can always output a clean and stable current pulse Ip, and can perform a current control with less vibration.

The present invention is not limited to the above-mentioned embodiment, but is embodied as a three-phase induction motor M as a load. However, the load may be a load including an inductance, for example, various other motors and transformers. It may be embodied in the control of a container or the like.

Further, in the above-described embodiment, the six regions Z1 to Z6 are divided at intervals of 60 degrees and a plurality of thyristor patterns for firing are set, but the present invention is not limited to this. For example, it is divided into three areas at 120 degree intervals,
On the contrary, it may be implemented by dividing into 12 regions at intervals of 30 degrees. When divided into three, there is an advantage that the number of firing thyristor patterns can be reduced, and when divided into 12 areas, finer and more sensitive control can be performed.

Further, each region may be divided into regions by dividing one period of one reference signal of the reference signals of each phase into a period unit in which the absolute value of the reference signal of a specific phase is continuously maximized. Good. Then, in the region, when the reference signal of the specified power line is positive, the switching element of the upper arm to which the specified power line is connected is turned on, and one switching element of the lower arm is turned on by the current of each phase. It is selected appropriately so as to approach each reference value. On the contrary, when the reference signal is negative in the region, the switching element of the lower arm to which the specified power line is connected is turned on, and
The two switching elements are appropriately selected so that the current of each phase approaches each reference value. Even in this case, the control is simplified as in the case of the above-described embodiment, and the resonance circuit is less likely to be affected by an unexpectedly large load change.

In the above embodiment, the resonance capacitor C0 and the resonance coil L0 are connected in series, and the coil Ld is connected in parallel to the resonance capacitor C0. Not something.
For example, the resonance capacitor C0 and the resonance coil L0 may be embodied as a series resonance circuit, or the resonance capacitor C0 and the resonance coil L0 may be embodied as a series resonance circuit in which a coil Ld is connected in parallel to the series circuit. Of course, the resonance capacitor C0 and the resonance coil L0 may be embodied as a parallel resonance circuit in which both are connected in parallel to the inverter circuit.

In the above embodiment, the input converter 1
1, the switch element of the inverter circuit 13 is embodied as a thyristor, but is not limited to this. For example, it may be embodied by a switching element such as a bipolar transistor, a MOS transistor, or a static induction transistor (SIT).

[0075]

As described in detail above, according to the present invention,
There is an excellent effect that it is possible to generate an output current with a small vibration component and to generate a current pulse having a uniform size and cycle as seen from the resonance circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a current resonance type inverter system embodying the present invention.

FIG. 2 is a block circuit diagram for explaining a processing operation by a controller.

FIG. 3 is a conceptual diagram for explaining a pattern of a thyristor which is an ignition target for each area.

FIG. 4 is a waveform diagram showing a relationship between a terminal voltage of a resonant capacitor and a current pulse.

FIG. 5 is a circuit diagram for explaining a conventional current resonance type inverter system.

FIG. 6 is a waveform diagram illustrating the concept of a reference signal.

FIG. 7 is a circuit diagram illustrating a current control loop for obtaining an error signal.

FIG. 8 is a waveform diagram showing a relationship between a terminal voltage of a conventional resonance capacitor and a current pulse.

[Explanation of symbols]

12 ... Resonance circuit, 13 ... Inverter circuit, 15, 16 ...
Current detector, 17 ... Rotation detector, 18 ... Controller,
Ip ... Current pulse, C0 ... Resonance capacitor, L0 ... Resonance coil, Ld ... Coil, a to c, -a to -c ... Thyristor, C ... Filter capacitor, E ... DC power supply, La, L
b, Lc ... Power line, M ... 3-phase induction motor, ia ^* , ib
^* , Ic ^* ... reference signal, ia, ib, ic ... output current.

Claims (4)

[Claims] 1. A current resonance type wherein, when a current pulse from a resonance circuit is distributed to a power line of each phase through an inverter circuit, the current pulse density is determined based on a deviation between a reference signal and an output current of the phase. In the method of controlling an inverter, one cycle of one reference signal of each phase is divided into a plurality of periods, the divided plurality of periods are defined as regions, and the period is divided based on the one reference signal. In addition to determining the region at any given time, identify the power line of one phase for each region and determine whether the absolute value of the output current of the phase is greater than the absolute value of the reference signal. When the absolute value of the output current is smaller, the current pulse of the specified phase is reduced by short-circuiting the current pulse supplied to the specified phase so that the output current becomes smaller when the output current is larger. The method of the current resonance type inverter so as to control the current pulse density of the phases other than the phase identified by fixing the degrees. 2. The power line has three phases, each reference signal is a sine wave that is 120 degrees out of phase with each other, and the reference signal of each phase has six reference signals for one cycle. The phase that equally divides and specifies the power line of one phase for each of the six divided areas is the phase of the reference signal whose value is different from the value of the other two reference signals for each reference signal. The method for controlling a current resonance type inverter according to claim 1, wherein is a specific phase. 3. A current pulse from a series type resonance circuit in which a resonance capacitor and a resonance coil are connected in series is distributed to a three-phase power line via switching elements of upper and lower arms of an inverter circuit and smoothed by a filter capacitor. When the obtained output current is output to the three-phase induction motor, the current pulse density is 120 degrees with respect to the rotation frequency of the three-phase induction motor and the torque command value that makes the three-phase induction motor a desired torque. In a control method of a current resonance type inverter, which is performed based on a deviation between a phase-shifted sine wave reference signal and an output current of the phase, a cycle of one reference signal among the reference signals of each phase is 6 Each area is divided into equal parts, and the divided six areas are judged based on the one reference signal at that time. For a signal, the phase of the reference signal whose value is different from the value of the other two reference signals is determined as a specific phase, and it is determined whether the absolute value of the output current of the phase is larger than the absolute value of the reference signal. Then, when the absolute value of the output current is larger, the switching elements of the upper and lower arms of the phase are operated to short-circuit the current pulse supplied to the phase to reduce the pulse density so that the output current becomes smaller, When the absolute value of the output current is smaller, the current pulse density of the specified phase is fixed and the current pulse density of the phase other than the specified phase is controlled by the switching element of the phase other than the specified phase. Resonant inverter control method. 4. A current resonance in which when a current pulse from a resonance circuit is distributed to a power line of each phase through an inverter circuit, the current pulse density is controlled based on a deviation between a reference signal and an output current of the phase. In the control method of the inverter, the period of one reference signal of the reference signals of each phase is divided into period units in which the absolute value of the reference signal of the specific phase is continuously maximized, and the divided plural Each period is defined as a region, and the power line that maximizes the absolute value of the reference signal is specified for each region. If the reference signal of the specified power line is positive, the specified power line is connected to the inverter circuit. Turn on the switching element of the upper arm, and if the reference signal is negative, turn on the switching element of the lower arm of the inverter circuit to which the specified power line is connected, and then turn it on. In this case, when the ON operation of the upper arm switching element is determined, one switching element of the lower arm that should be turned on is selected, and the lower arm switching element should be turned on when the ON operation is determined. A method of controlling a current resonance inverter, wherein a current pulse density is controlled so that a current of each phase approaches each reference value by selecting one switching element of an upper arm.