JP2004229492A - Controller for matrix converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for a matrix converter in which the number of PWM outputs from a micro-computer for a switching command is made fewer than eighteen which is the number of switching elements, in the controller for the three-phase output matrix converter. <P>SOLUTION: A first PWM signals which has the number of systems fewer than the number of the switching elements is calculated and outputted by the micro-computer regarding the calculation of an output voltage command value. A circuit which calculates a second PWM signal having the number of the systems same as the number of the switching elements on the basis of the first PWM signal, output current information, and input voltage information is provided outside the micro-computer. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a matrix converter that directly generates an AC output of an arbitrary frequency from an AC power supply of a constant frequency.
[0002]
[Prior art]
A conventional converter has a configuration in which a commercial power supply is once converted to direct current by a rectifier unit, and an alternating current of an arbitrary frequency is output by an inverter unit. In this case, it is necessary to provide a smoothing capacitor in the DC section to reduce the ripple. In addition, when a diode rectifier is used in the rectifier device, power regeneration cannot be performed and power supply harmonics increase. A matrix converter that directly generates an AC output of an arbitrary frequency from a commercial power supply does not require a smoothing capacitor, and has advantages such as power regeneration and low power supply harmonics. Note that there is the following publication as a conventional technology of the matrix converter.
[0003]
[Patent Document 1]
JP 2001-258258 A
[Problems to be solved by the invention]
However, in a three-phase output matrix converter, a combination between the three-phase voltages (R-phase, S-phase, and T-phase) of the commercial power supply and the three-phase output voltages (U-phase, V-phase, and W-phase) is connected. It is necessary to use two bidirectional switches. Moreover, each bidirectional switch includes at least two switching elements. Therefore, in order to drive the matrix converter, it is necessary to give individual switching commands to each switching element, and a total of 18 command values are required.
[0005]
In a general converter, a command value is calculated using a microcomputer based on an output current or the like. In particular, in the conventional PWM inverter, since the number of switching elements is six, six PWM output terminals of a commercially available general-purpose microcomputer are connected to the six switching elements in a one-to-one correspondence. It can be driven by giving a command value. Further, in the case of the conventional PWM inverter, two switching elements are provided for each output phase, and only the command values to be input to one of the three devices are generated by the microcomputer and used almost as it is. It is also possible to generate the command value of the device by giving an inversion and non-lap condition using an external circuit, and to provide two sets of PWM signals to the device. In this case, the microcomputer may have three PWM output terminals, but the effect of reducing the number of output terminals from the microcomputer is only three.
[0006]
On the other hand, in the case of a matrix converter, when all the switching commands to each switching element are calculated by the microcomputer, 18 systems of PWM outputs are required. In particular, since a command value to be input to each bidirectional switch requires a complicated value including a wrap time and a non-wrap time, a simple external circuit such as a PWM inverter that generates an inverted input cannot be used. In addition, based on the input voltage state and the output current positive / negative information, the microcomputer needs to perform complicated PWM arithmetic processing in addition to normal vector control. Also, the number of PWM output terminals of a normal microcomputer is limited to about 6 to 12, so when increasing the number of PWM outputs, use a custom microcomputer with a further increased number of PWM output terminals. Alternatively, it is necessary to adopt a usage with limited functions.
[0007]
An object of the present invention is to provide a control device for a three-phase output matrix converter, in which the number of PWM outputs from a microcomputer related to the switching command is smaller than the number of switching elements of 18, which is the number of switching elements. .
[0008]
[Means for Solving the Problems]
As means for solving the above-mentioned problem, in the calculation of the output voltage command value, the microcomputer calculates and outputs the first PWM signal of the number of systems smaller than the number of switching elements. Outside the microcomputer, a circuit (hereinafter referred to as a command calculation circuit) for calculating the same number of second PWM signals as the number of switching elements based on the first PWM signal, the output current information and the input voltage information is provided.
[0009]
According to the present invention, in a three-phase output matrix converter, the number of PWM signals from a microcomputer relating to a switching command can be equivalently increased, so that the PWM output terminal of the microcomputer can be used effectively and the control function can be improved. Can be prevented from decreasing. Further, it is not necessary to use an expensive device such as a custom microcomputer having an increased number of PWM output terminals, which is effective in reducing costs.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0011]
FIG. 1 shows a matrix converter according to a first embodiment of the present invention, which comprises a commercial power supply 1, a load such as a motor, an input power supply amplitude / phase detection circuit 3, a control circuit 4, an output current detector 5, and a bidirectional switch 6. Make up. Reference numeral 7 denotes a bidirectional switch for one phase (U phase). Further, the LC filter 10 is provided for removing high-frequency noise flowing out to the power supply 1 side, and includes a reactor and a capacitor. The power switch 11 is a switch that opens between the power source 1 and the matrix converter when an abnormality occurs in the matrix converter, and includes a contactor and the like.
[0012]
The matrix converter of FIG. 1 converts AC power of a constant frequency obtained from the commercial power supply 1 into AC power of an arbitrary frequency by turning on / off a bidirectional switch 6 connected to a total of nine switches, three in each phase. Convert. In this matrix converter, the size of the device can be reduced because the smoothing capacitor, which is essential in the conventional converter, can be eliminated. In addition, power regeneration is possible, and power supply harmonics can be reduced as compared with the conventional converter.
[0013]
The input power supply amplitude / phase detection circuit 3 is a device that detects the power supply amplitude or the power supply phase of each phase of the commercial power supply 1. The input power supply amplitude / phase detection circuit 3 detects the state of the power supply 1 using a transformer or the like, and transmits an input voltage signal 8 to the control circuit 4. The input voltage signal 8 may be a signal proportional to the amplitude value of the input power supply, or a signal capable of estimating the state of the power supply 1 in the control circuit 4 (for example, a periodic signal such as a signal every 60 °). . In other words, the input power supply amplitude / phase detection circuit 3 aims at grasping the state of the power supply 1 at least by the control circuit 4. Hereinafter, an example of the latter method of transmitting a signal capable of estimating the state of the power supply 1 in the control circuit 4 to the control circuit 4 will be described.
[0014]
The output current detector 5 is a device for detecting an output current, and includes a current transformer (CT) and the like. The output current detector 5 transmits the detected current information to the control circuit 4 as an output current signal 9. The output current signal 9 is current information for three phases, or current information for two phases or one phase.
[0015]
Next, the bidirectional switch 6 in FIG. 1 will be described with reference to FIGS. FIG. 2 and FIG. 3 are detailed diagrams of the bidirectional switch 6. 2 is configured by combining conventional IGBTs 61_a and 61_b and diodes 62_a and 62_b, and FIG. 3 is configured by combining reverse blocking IGBTs 63_a and 63_b. The conventional IGBTs 61_a and 61_b of FIG. 2 and the reverse blocking IGBTs 63_a and 63_b of FIG. 3 are both unidirectional switches, each having two opposing switches, and independently controlled for each direction. A bidirectional switch is realized. In the conventional IGBTs 61_a and 61_b, it is necessary to connect diodes 62_a and 62_b having a reverse breakdown voltage as shown in FIG. 2 in order to prevent damage caused when a voltage is applied in the reverse direction. On the other hand, in the case where the reverse blocking IGBTs 63_a and 63_b having the reverse withstand voltage performance are used, the diode is not required, so that the number of chips can be reduced.
[0016]
2 and 3, one bidirectional switch 6 includes two switching elements (conventional IGBTs 61_a and 61_b or reverse blocking IGBTs 63_a and 63_b). That is, the matrix converter of FIG. 1 includes a total of 18 switching elements. Since these switching elements are individually turned on and off, it is necessary to give an independent switching command value to each of them. In a conventional general power converter, a command value is calculated using a microcomputer based on an output current or the like. For example, in a PWM inverter, since the number of switching elements is six, the microcomputer calculates and outputs PWM command values of six systems. On the other hand, when all the switching commands to each switching element are calculated by the microcomputer using the matrix converter, the microcomputer needs to output PWM command values of 18 systems. Normally, the number of PWM output terminals of the microcomputer is limited, so when increasing the number of PWM outputs, it is necessary to use a more expensive and sophisticated microcomputer or to use the function with limited functions. .
[0017]
Next, the control circuit 4 in FIG. FIG. 4 is a configuration diagram of the control circuit 4 according to the present invention, which includes a microcomputer 41, a command generation unit 42, and a current direction detection unit 43. The current direction detector 43 is a device that determines whether the output current is positive or negative. The microcomputer 41 receives the input voltage signal 8 from the input power supply amplitude / phase detection circuit 3 and the output current signal 9 obtained from the output current detector 5, and calculates a first PWM signal 44. In the example of FIG. 4, the microcomputer 41 does not directly output the command values of all the switching elements (18), but calculates the first PWM signals 44 of a total of six systems of two systems for each phase, and generates a command generation unit 42. Output to
[0018]
The command generation unit 42 is a circuit that calculates and outputs a second PWM signal 45 that is a drive signal of the bidirectional switch 6, and is composed of a logic circuit or an integrated circuit incorporating a logic circuit. The command generation unit 42 receives as input the first PWM signal 44 output from the microcomputer 41, the input voltage signal 8 from the input power supply amplitude / phase detection circuit 3, and the output current signal 9 obtained from the current detector 5. Calculate. Here, as for the input power supply voltage, the command generation unit 42 only needs to know the voltage arrangement information of the maximum phase, the intermediate phase, and the minimum phase. (For example, in FIG. 1, when the VR phase is the R phase, the VS phase is the S phase, and the VT phase is the T phase, the maximum phase at an instant is the R phase, the intermediate phase is the V phase, and the minimum phase is the W phase. Therefore, instead of transmitting the input voltage signal 8 directly to the command generation unit 42, the input voltage signal 8 from the input power source amplitude / phase detection circuit 3 is once passed through the microcomputer 41 and is required. May be converted into a signal that can be calculated by the command generation unit 42 and transmitted to the command generation unit 42 as the second input voltage signal 81. Also, regarding the output current, since the command generator 42 only needs to know the positive or negative information of the current, instead of transmitting the output current signal 9 directly to the command generator 42, the output obtained from the current detector 5 is used. The current signal 9 may be temporarily converted into a signal that can be calculated by the command generation unit 42 via the microcomputer 41 and, if necessary, and transmitted to the command generation unit 42 as the second output current signal 91. Alternatively, instead of transmitting the output current signal 9 directly to the command generation unit 42, the output current signal 9 obtained from the current detector 5 is temporarily passed through the current direction detection unit 43, and the command is issued as needed. The signal may be converted into a signal that can be calculated by the generator 42 and transmitted to the command generator 42 as the third output current signal 91. In these cases, the microcomputer 41 may use a general-purpose digital output terminal having a sufficient number of terminals compared to the PWM output terminal, and does not need to use a special microcomputer.
[0019]
Next, the control circuit 4 will be described with reference to FIGS. 5 and 6 by focusing on one phase (U phase) of the output of the command signal. FIG. 5A is a detailed view of the bidirectional switch 7 for one phase. Here, S1 and S2, S3 and S4, S5 and S6 are a set of bidirectional switches 6, respectively. Further, the output current Iout has a positive direction when flowing from the switch to the load.
[0020]
FIG. 5B shows an example of a PWM calculation process in the microcomputer, in which the ratio of turning on the switch is changed by comparing the triangular wave carrier with two command values Vt ^* and Vb ^* . Here, when the command value Vt ^* is smaller than the triangular wave, an ON signal is output, and when the command value Vb ^* is larger than the triangular wave, an ON signal is output.
[0021]
FIG. 5C shows a PWM waveform when a triangular wave comparison is performed in the microcomputer 41 according to FIG. 5B, and is input to the command generation unit 42. In the case of this example, the output of the first PWM signal 44 of the microcomputer for one phase is two systems, and the output of the first PWM signal 44 is six systems for three phases. In other words, the number of signals can be reduced to 1/3 or less of the 18 systems required for the matrix converter, so that the PWM output terminal of the microcomputer can be used effectively and the control function can be prevented from deteriorating. effective. In addition, there is no need to use an expensive high-performance microcomputer, which is effective in reducing costs. Also, in the conventional inverter, a signal for the three-phase upper arm is created by the microcomputer at the time of control, and the signal is compared with a signal obtained by inverting this signal externally and adding a non-lap time. The one PWM signal and the second PWM signal are completely different, and it is clear that the present application is not an extension of the prior art.
[0022]
Specific pulse generating means will be described below with reference to FIG. FIG. 6 is an example of a circuit configuration diagram in the command generation unit 42 of FIG. The command generation unit 42 includes a NOR circuit unit 421, a signal distribution unit 422, and a two-output generation unit 423. The input signals are the microcomputer outputs (Mout1, Mout2) of FIG. 5C, the current direction signal 9 or 91 or 92 obtained from the output current detector or current direction detection circuit 43 or the microcomputer 41, and the input power source amplitude / phase detection. These are an input voltage signal 9 or 93 (Sig1, Sig2, Sig3) obtained from the circuit 3 or the microcomputer 41, and a Reset signal obtained from a microcomputer or an external circuit or the like to stop output in an emergency. The output signal is a drive command signal (PWM_S1, PWM_S2, PWM_S3, PWM_S4, PWM_S5, PWM_S6) of the switch element. Here, the microcomputer output (Mout1, Mout2) is one phase (U phase) of the first PWM output 44 in FIG. 4, and the drive command signal of the switch element is one phase (U phase) of the second PWM output 45. Phase). Further, the current direction signal 9 or 91 or 92 here is also a signal for one phase (U phase).
[0023]
The NOR circuit section 421 performs a NOR operation on the microcomputer output (Mout1, Mout2) signals to generate a third command value signal (Pulse_NOR) shown in FIG.
[0024]
Next, the processing of the signal distribution unit 422 in FIG. 6 will be described with reference to FIG. The signal distribution unit 422 performs a process of distributing the microcomputer output (Mout1, Mout2) signal and the third command value signal (Pulse_NOR) according to the state of the input power supply. The input signals are a microcomputer output (Mout1, Mout2) signal and an input voltage signal (Sig1, Sig2, Sig3), and the output signal is a signal (PUR, PUS, PUT) that has been subjected to a sorting process. The state of the power supply (the state of the maximum phase, the intermediate phase, and the minimum phase) can be classified into six types as shown in FIG. FIG. 7B is an example in which the input voltage signals (Sig1, Sig2, Sig3) are classified into six power supply states. FIG. 7C shows the input voltage signals (Sig1, Sig2, Sig3) depending on the state of the input voltage signals (Sig1, Sig2, Sig3). Thus, the microcomputer output (Mout1, Mout2) signal and the third command value signal (Pulse_NOR) are distributed. FIG. 7D shows a configuration example of a circuit for realizing this processing. The logic circuit can distribute Mout1, Mout2, and Pulse_NOR to Sig1, Sig2, and Sig3.
[0025]
Next, the processing of the two-output generation unit 423 in FIG. 6 will be described with reference to FIG. FIG. 8 is an example of a circuit configuration of the two-output generation unit 423. The two-output generation unit 423 performs a process of converting the individual signals (PUR, PUS, PUT) that have been distributed by the signal distribution unit 422 into signals to be provided to a set of bidirectional switches 6. The input signal is a signal (PUR, PUS, or PUT) that has been subjected to the sorting process, a current direction detection signal, and a Reset signal. (PWM_S5, PWM_S6)). The drive command signal for the switch element needs to have a dead time td and a lap time tr as described later. Therefore, the generation of the dead time and the lap time is realized by using the delay circuit and the logic circuit as shown in FIG. In addition, a process of determining whether the output current is positive or negative using the current direction detection signal and generating the second PWM output 45 (PWM_S1, PWM_S2) for one phase is performed.
[0026]
As a result of the above processing, signals as shown in FIGS. 5 (e) and 5 (f) can be generated. FIGS. 5E and 5F show the second PWM output 45 of the matrix converter per one phase calculated and output by the command generation unit 42. When Iout> 0, Iout <0, respectively. Represents the case of
[0027]
The switching operation of the switching signal will be described, focusing on the section A in FIG. In the bidirectional switch for one phase shown in FIG. 5A, in order to prevent a short circuit between the respective phases (VR, VS, VT) on the power supply side, a switching element having a short-circuit loop, for example, S1 and S1 is formed. Control must be performed so that S4 or S1 and S6 are not simultaneously turned on. For this reason, when the devices having the above relationship are turned on / off, a dead time td is provided so that S4 and S1 and S3 and S2 are not simultaneously turned on to prevent a short circuit. Further, in FIG. 5E, in the switching of the switches (S1, S3, S5) in which the positive output current Iout conducts, S1 and S3 are simultaneously set during the lap time tr so that the commutation operation is performed well. It is controlled to be ON. This control is performed by the two-output generation unit 423 of FIG. 6 described above. Similarly, in FIG. 5F, the lap time tr is provided when the switches (S2, S4, S6) in which the negative output current Iout conducts perform switching.
[0028]
FIGS. 5E and 5F show the second PWM output 45 for one phase when the state of the input voltage is VR>VS> VT (state I in FIG. 7B). However, when VR>VT> VS (in the case of state II in FIG. 7B), the second PWM output 45 changes according to the distribution pattern of FIG. 7C (in this case, PWM_S3 PWM_S5, PWM_S4, and PWM_S6 are replaced with each other.)
[0029]
A conventional PWM inverter with matrix converter processing and two switching elements for each output phase generates only command values to be input to one device by a microcomputer, and command values for the other device use an external circuit. The major difference from the example where the processing is performed is as follows. The processing of the external circuit in the conventional PWM inverter is simply inverted and generated by giving a dead time condition, whereas the processing of the matrix converter is based on the input voltage and the output current signal as components, and based on the information. It differs greatly in that signals are distributed and processing for providing a dead time / lap time is performed. Also, in the conventional PWM inverter, the output signal of the microcomputer and the switching element basically correspond one-to-one. However, since the matrix converter includes a distribution process, the output signal of the microcomputer and the specific element do not correspond. different. (That is, the first PWM output 44 and the second PWM output 45 of the matrix converter of the present invention partially have substantially the same waveform, but do not basically match.) Thus, in the present application, the PWM output is used. In addition to solving the problem of the number of terminals, the following effects are also obtained. In other words, if all of the above-described complex processing is performed by software processing in the microcomputer within a high-speed switching cycle, an expensive and high-performance microcomputer is required. According to the work sharing, there is an effect of reducing the load on the microcomputer, and an effect that an inexpensive general-purpose microcomputer can be used also occurs.
[0030]
Next, the processing at the time of abnormality will be described with reference to FIG. In the circuit configuration of the two-output generation unit 423 in FIG. 8, a Reset signal is input from the microcomputer 41 or an external circuit when an abnormality occurs. In this case, since the LO signal is input to the final AND circuit, PWM_S1 and PWM_S2 can be turned off. The processing here is intended to stop the output when an abnormality occurs, and the circuit configuration may be a form other than that of FIG. In this case, if the output is suddenly stopped, an overvoltage may be applied to the switching element. Therefore, it is necessary to attach an overvoltage protection circuit near the switching device.
[0031]
Next, another example of the processing at the time of abnormality will be described with reference to FIGS. When an abnormality occurs, first, the microcomputer 41 of FIG. 4 outputs a switch release signal 46 to open the power switch 11 of FIG. In this case, although the current is regenerated from the load side, the current is recirculated by using the capacitor of the LC filter 10 in FIG. 1 to perform a switching operation such that the load can be stopped stably. The calculation of the stop processing at this time is performed by the microcomputer 41 or the command calculation unit in FIG. In FIG. 4, the switch open signal 46 of the power switch 11 is output from the microcomputer 41, but it goes without saying that the switch open signal 46 may be output from a circuit other than the microcomputer 41 in the control circuit 4, such as the command calculation unit 42.
[0032]
Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and it goes without saying that various modifications can be made without departing from the spirit and scope of the invention.
[0033]
【The invention's effect】
According to the present invention, in a three-phase output matrix converter, the number of PWM signals from a microcomputer relating to a switching command can be equivalently increased, so that the PWM output terminal of the microcomputer can be used effectively and the control function can be improved. Can be prevented from decreasing. Further, it is not necessary to use an expensive device such as a custom microcomputer having an increased number of PWM output terminals, which is effective in reducing costs.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of the present invention.
FIG. 2 is a detailed view 1 of a bidirectional switch part.
FIG. 3 is a detailed view 2 of a bidirectional switch part.
FIG. 4 is a configuration diagram of a control circuit portion of the present invention.
FIG. 5 is an explanatory diagram relating to a command signal output in the control circuit of the present invention.
FIG. 6 is an example of a circuit configuration per phase in a command generation unit of the present invention.
FIG. 7 is an example of signal distribution in a circuit configuration of a command generation unit according to the present invention.
FIG. 8 is an example of a two-output generator in the circuit configuration of the command generator of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Commercial power supply, 2 ... Load, 3 ... Input power supply amplitude / phase detection circuit, 4 ... Control circuit, 5 ... Output current detector, 6 ... Bidirectional switch, 7 ... Bidirectional switch for one phase, 8 ... Input Voltage signal, 9 output current signal, 10 LC filter, 11 power switch, 41 microcomputer, 42 command generation unit, 43 current direction detection unit, 44 first PWM signal, 45 second PWM Signal, 46: switch open signal, 61: IGBT, 62: diode, 63: reverse blocking IGBT, 81: second input voltage signal, 91: second output current signal, 92: third output current signal, 421 ... NOR circuit section, 422... Signal distribution section, 423.

Claims (10)

A bidirectional switch module comprising at least nine bidirectional switches or the bidirectional switch, wherein an input side of the bidirectional switch or the bidirectional switch module is configured to be connected to a power supply; In a matrix converter configured to connect a load to an output side of the bidirectional switch or the bidirectional switch module,
In order to control the on / off of the switching element in the bidirectional switch, a microcomputer is provided for calculating a first PWM command value, and the number of first PWM signals output by the microcomputer is determined by the switching element. A matrix converter control device characterized in that the number is less than the number. A bidirectional switch module comprising at least nine bidirectional switches or the bidirectional switch, wherein an input side of the bidirectional switch or the bidirectional switch module is configured to be connected to a power supply; and In a matrix converter configured to connect a load to an output side of the bidirectional switch or the bidirectional switch module,
In order to control on / off of the switching element in the bidirectional switch, a command generation unit including a microcomputer and a logic circuit or an integrated circuit incorporating a logic circuit is provided, and an output of a first PWM signal from the microcomputer is used. The command generation unit is configured to generate a second PWM signal for driving a switching element, and the number of outputs of the first PWM signal from the microcomputer is determined by the command generation unit supplied to the switching element. The number of outputs of the second PWM signal is smaller than the number of outputs of the second PWM signal. In claim 1 or claim 2,
A means for detecting amplitude information or phase information of the input voltage is provided. The input voltage detecting means transmits a signal to the microcomputer or the command generation unit and drives a switching element based on the signal. A control device for a matrix converter, which calculates a signal. In claim 1 or claim 2,
A means for detecting current information of the output current is provided, and the current information means transmits a signal to the microcomputer or an integrated circuit incorporating the command generation unit, and drives a switching element based on the signal. A control device for a matrix converter, which calculates a PWM signal. In claim 2,
A means for detecting amplitude information or phase information of the input voltage; converting a signal output from the input voltage detecting means into a signal that can be input to the command generation unit by the microcomputer or an external circuit; The control unit for a matrix converter, wherein the unit calculates a second PWM signal for driving a switching element based on the converted signal. In claim 2,
A means for detecting current information is provided, and a signal output from the current information detecting means is converted into a signal that can be input to the command generation unit by the microcomputer or an external circuit, and the command generation unit converts the converted signal. A control device for a matrix converter, which calculates a second PWM signal for driving a switching element based on a signal. In claim 6,
A control device for a matrix converter, wherein the output current signal converted by the microcomputer or the external circuit is a signal for determining whether the output current signal is positive or negative. In claim 1 or claim 2,
The control device for a matrix converter, wherein the microcomputer or the command generation unit has a mechanism for turning off all switching elements and stopping output when an abnormality occurs in the matrix converter. In claim 1 or claim 2,
A control device for a matrix converter, wherein a power switch is provided between an input power source and a switching element, and the microcomputer or the command generation unit has a mechanism for opening the power switch. In claim 9,
An LC filter comprising a reactor and a capacitor is provided between the power switch and the switching element, and the microcomputer or the command generation unit opens the power switch when the matrix converter is abnormal, and stably stops the load. And a driving signal for the switching element.

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