JP4487155B2 - Protection device for PWM cycloconverter - Google Patents

Description

[0001]
[Industrial application fields]
The invention, for example, relate to the protection device of the PWM cycloconverter for converting a commercial AC voltage into an AC voltage of an arbitrary frequency.
[0002]
[Prior art]
The PWM cycloconverter does not have a smoothing capacitor like an inverter in order to convert an AC power supply (for example, a commercial AC voltage) into an AC voltage having an arbitrary frequency. Therefore, when some abnormality occurs, all the power semiconductor elements of the PWM cycloconverter are turned off to interrupt the current. At the same time, when all the semiconductor switch elements are turned off, the output side is opened. Therefore, when driving the motor, if the output side of the PWM cycloconverter becomes open during operation, a large surge voltage is generated on the output side. In the prior art, an intermediate parallel connected to the PWM cycloconverter to by snubber circuit between the first power supply and the load as a surge suppression means is observed. The snubber circuit has an effect of suppressing a surge voltage generated by commutation mistake during the normal operation, a surge voltage generated when turning off all switches when an abnormality occurs.
Further, as prior art, Japanese Patent Application No. 10-310843 (filing date: October 30, 1998) is available. This prior example is a one-way semiconductor switching element from an output phase to an input phase that becomes a maximum voltage among three-phase input voltages based on input voltage information when any abnormality occurs during operation of the PWM cycloconverter. And a protective means for performing regenerative switching to the power supply by always turning on the one-way semiconductor switching element from the input phase to the output phase, which is the minimum voltage among the three-phase input voltages.
[0003]
[Problems to be solved by the invention]
However, in the protection circuit of the PWM cycloconverter using the conventional snubber circuit, when all the semiconductor switching elements are turned off during operation, a large current flows instantaneously in the snubber capacitor, so that the capacitor capacity must be increased. There are challenges. Similarly, in the preceding example, based on the input voltage information, the one-way semiconductor switching element from each output phase to the input phase that becomes the maximum voltage in the three-phase input voltage, and the minimum voltage in the three-phase input voltage It is a protection means that performs regenerative switching to the power supply by always turning on the unidirectional semiconductor switch element from the input phase to each output phase. In this case, if the input three-phase power supply causes an instantaneous power failure, the PWM cycloconverter Power is regenerated to the input filter, and the regenerated power is consumed by the resistor, and the motor can only be short-circuited to the free-run state and the power cannot be reused. . Here, in order to wipe out all the technical bottlenecks in the conventional example and the previous example, the present invention regenerates power to the input filter unit when an instantaneous power failure occurs, and a mode for driving the motor based on the input power supply information. It is an object of the present invention to provide a protection device for a PWM cycloconverter capable of effectively using electric power by switching the input voltage level depending on the input voltage level. Furthermore, the capacitor capacity of the snubber circuit is reduced.
[0004]
In order to achieve the above object, according to the first aspect of the present invention, unidirectional semiconductor switch elements that allow current to flow in only one direction through each phase of a three-phase AC power source and each output phase are connected in opposite directions. In the PWM cycloconverter of a power converter that is directly connected by a bidirectional semiconductor switching element that can be turned on and off independently, an AC filter is provided on the input side, and a three-phase AC motor is provided on the output side, the PWM cycloconverter A fault detection means for detecting a fault and outputting a fault detection signal; and a voltage at the three terminals on the input side of the bidirectional semiconductor switch element as a three-phase input voltage, and information for determining the magnitude relationship of the three-phase input voltage Input voltage information detecting means for detecting as input voltage information;
Based on the input voltage information, only the one-way semiconductor switch element from the output phase to the input phase that is the maximum voltage in the three-phase input voltage is turned on, or the minimum in the three-phase input voltage Regenerative switching means for turning on only the one-way semiconductor switching element from the input phase to be the voltage to each output phase; and input voltage value detecting means capable of detecting a voltage level from the input voltage value on the input side of the PWM cycloconverter. With
When an input low voltage signal is generated during operation of the PWM cycloconverter (mode 1), power is regenerated to the capacitor part of the AC filter on the input side by the regenerative switching means (mode 2), and input during the power regeneration. An apparatus for protecting a PWM cycloconverter, characterized in that when the power supply voltage level exceeds a certain threshold, electric switching (mode 4) for simply driving the AC motor with the power of the AC filter is performed .
According to the first aspect of the present invention, in the case of an instantaneous power failure of the input power supply, the regenerative switching is applied and the power regenerated in the AC filter is used for driving the load AC motor so that the power can be effectively used. Play.
[0005]
According to a second aspect of the present invention, in the protection device for the PWM cycloconverter according to the first aspect, the input voltage value detecting means includes a rectifier that rectifies the three-phase full-wave voltage on the input side, and a rectified DC voltage. 2. The PWM cycloconverter protection device according to claim 1, further comprising a comparator that compares a predetermined reference direct current threshold voltage with a threshold DC voltage.
According to the second aspect of the present invention, it is possible to provide the effectiveness that enables appropriate power processing corresponding to the voltage value (voltage level) on the input side.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a circuit configuration of a PWM cycloconverter according to an embodiment of the present invention. In FIG. 1, 1 is a three-phase AC (commercial) power source, 2 is an AC line filter, 61, 62 and 63 are its reactors, and 64, 65 and 66 are their capacitors.
Reference numeral 3 denotes a PWM cycloconverter, which is composed of a unidirectional semiconductor switch element [for example, Insulated Gate Bipolar Transistor] having a self-extinguishing capability that allows current to flow only in one direction, and a diode connected in series to the unidirectional semiconductor switch element. Is represented by Sur, Ssu, Sus, Stu, Sut, Srv, Svr, Ssv, Stv, Svt, Srw, Swr, Ssw, Sws, Stw, Swt, and the diodes are represented by d1 to d18.
Here, the suffix attached to Sxy in the unidirectional semiconductor switch element is the x direction from the input x phase to the output y phase, and Syx is the unidirectional semiconductor switch element from the y phase of the output to the input x phase (x = r, s, t Y = u, v, w).
21 is a three-phase AC motor, 22 is a power supply voltage detection unit, 23 is a controller, 24 is a gate signal synthesis unit, 25 is a gate driver, 30 is an input voltage information detection unit, 40 is an input voltage value (voltage level) detection unit, Reference numeral 50 denotes a protection gate signal generator.
[0008]
Then, the power supply voltage detection unit 22 gives the power supply voltage instantaneous value 22a of each phase of the three-phase AC power supply 1 and the power supply voltage phase 22b to the controller 3 for controlling the operation of the PWM cycloconverter 3. The motor current values flowing through the respective phases are detected by current transformers 71 to 73, and those motor current values are also given to the controller 3 to control the operation of the normal PWM cycloconverter 3 in accordance with the output voltage command 23a. Yes.
By the way, the presence / absence of abnormal operation of the PWM cycloconverter 3 is always based on the monitoring of the power supply voltage on the power supply 1 side and the installation of overcurrent relays for each phase on the power supply 1 side and the motor 21 side. An abnormality in the operation of the PWM cycloconverter 3 is detected by the signal [not shown].
[0009]
FIG. 2 is a block diagram mainly showing a circuit configuration of the input voltage value (voltage level) detection unit and its periphery. The value of the input voltage applied to the PWM cycloconverter 3 from the disconnector 2a through the AC line filter 2 is detected by the input voltage value detector 40. After full-wave rectification by full-wave rectifier 401, the detected DC voltage obtained through the smoothing circuit (capacitor 402), load resistance (voltage-dividing resistors 403, 404), etc. becomes one input to comparator 406 and the other DC Compared with the reference (threshold) voltage, the input voltage value detection signal V1 is sent to the controller 3 when the detected DC voltage value exceeds the threshold value.
[0010]
FIG. 3 is a block diagram illustrating a circuit configuration of the input voltage information detection unit.
31 to 36 are current detection circuits having the same configuration, and 37 is a resistor. For example, regarding the current detection circuit 31, 41 and 42 are diodes, 43 is a photocoupler, 44 is a resistor, 45 is an output terminal, and Vcc is a positive electrode of a DC reference voltage.
When a current flows through the diode 41, the voltage at the output terminal 45 becomes Low. On the other hand, when no current flows through the diode 41, the voltage at the output terminal 45 is High. For example, the output voltage / Max = 0 when the r-phase voltage is maximum, and the output voltage / Min = 0 when the voltage is minimum. The same applies to the s phase and the t phase.
[0011]
FIG. 4 is a block diagram showing a circuit configuration before and after the protection gate signal generator.
The input voltage information of the maximum voltage, the intermediate voltage, and the minimum voltage from the input voltage information detection unit 30 is given to the protection gate signal generation unit 40, and the protection gate signal created through the inverters (phase inverting circuits) 51 to 56 G2 is given to the gate signal synthesizing unit 24 in the next stage (yx or xy in G2yx or G2xy represents a protection gate signal given to the unidirectional semiconductor switching element in the direction of current flow).
[0012]
In this way, the power supply voltage detector 22 in FIG. 1 receives the power supply voltage and outputs the power supply voltage phase 22b and the power supply voltage instantaneous value 22a. The controller 23 outputs the output voltage command 23a, the power supply voltage phase 22b and the power supply voltage. Based on the instantaneous voltage value 22a and the load current direction, a normal gate signal (abbreviated as “G1”) for turning on / off the 18 unidirectional semiconductor switch elements included in the PWM cycloconverter 3 is generated and output.
Thus, the present invention takes the logical sum of the normal gate signal G1 from the controller 23 and the protection gate signal G2 from the protection gate signal generation unit 40 by the gate signal synthesis unit 24, and uses the synthesized gate signal G3 to select each element. I have control. That is, the input voltage information detection unit 30 in FIG. 1 inputs the voltage of each unidirectional semiconductor switch element, creates and outputs information on the magnitude relation of the three-phase input voltage, and from the obtained information, When this occurs, the AC motor current continues to flow by turning on only the one-way semiconductor switching element from the input phase to the output phase, which is the minimum voltage among the three-phase input voltage, and the generation of the surge voltage is suppressed.
[0013]
FIG. 5 shows an equivalent circuit when all the normal gate signals (G1) are turned off when the PWM cycloconverter is shut off in the case of an abnormal operation, and only specific elements of the PWM cycloconverter are kept on by the gate protection signal G2. FIG.
That is, the specific element is Sup, Svp, Swp, Snu, Snv, Snw, where p or n is one of r, s, t, and Svp, Swp, Snu is the output side. Represents the current direction from the input side to the input side, and Snu, Snv, Snw indicate the current direction from the input side to the output side.
[0014]
Furthermore, the input voltage value detection unit 40 in FIG. 1 performs three-phase full-wave rectification on the input three-phase voltage, and when the voltage level exceeds a certain value / threshold value, a signal that outputs V1 = 1 is output. The input power supply voltage level detection signal V1 is generated and output to the controller 23.
The controller 23 that has received the detection signal V1 uses the electric charge regenerated to the AC line filter 2 to drive the AC motor 21 simply, thereby effectively applying the regenerative power, and then performing PWM cycling. The base block of the unidirectional semiconductor switch element of the converter is performed and the operation is stopped.
On the other hand, if the detection signal V1 is not obtained even if the failure of the PWM cycloconverter is detected and the power is regenerated to the AC line filter 2, the base block of the unidirectional semiconductor switch element of the PWM cycloconverter is used as usual. To stop operation.
[0015]
The procedure of the operation method of the present invention is shown in the flowchart of FIG.
That is, the operation is performed according to the procedures of steps 601 to 608.
FIG. 7 is a time chart showing a comparison between conventional mode (MODE) switching means based on input information and mode switching means proposed in the present invention.
As shown in (a), look at the time when a failure occurred at time t1.
In the conventional mode switching of (b), when the input low voltage signal 41 is generated during the operation of the PWM cycloconverter (mode 1:43), the regenerative switching (mode 2:44) described above is performed for a while. After the motor current converges, the base block (mode 3: 45) for turning off all the switches is performed.
In the present invention shown in (c) and (d), when the input low voltage signal 41 generated during the PWM cycloconverter operation (mode 1:43), first regenerative Control button quenching previously described (mode 2:44 ) To regenerate power in the capacitor portions 64 to 66 of the AC filter 2 on the input side. When the input power supply voltage level exceeds a certain value [threshold value] by the regenerated power, the output 421 from the input voltage value detection unit 40 becomes signal V1 = “1”.
When the controller 23 detects the output signal V1 (time point t3), the controller 23 simply performs electric switching (mode 4:46) for driving the AC motor 21 based on the information obtained from the input voltage information detection unit 30. The conventional after the motor current has converged in the same manner (time t6), performs base block (mode 3:45) to turn off all the Control button quenching.
[0016]
【The invention's effect】
As described above, in order to protect the PWM cycloconverter, according to the present invention, in the case of an instantaneous power failure of the input power supply, the motor is driven by the power regenerated by the PWM cycloconverter using the conventional regenerative switching. It is possible to exhibit a special effect of effective use. It is possible to further reduce the capacitance of the snubber circuit.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall circuit configuration including a PWM cycloconverter according to an embodiment of the present invention and its periphery. FIG. 2 mainly shows a circuit configuration of an input voltage value detection unit in the embodiment of the present invention. FIG. 3 is a block diagram showing a circuit configuration of an input voltage information section in the embodiment of the present invention. FIG. 4 is a block diagram mainly showing a circuit configuration of a protection gate signal generating section in the embodiment of the present invention. FIG. 5 is an equivalent circuit diagram at the time of power regeneration in the embodiment of the present invention. FIG. 6 is a flowchart showing an operation procedure in the embodiment of the present invention. Time chart that contrasts mode switching [Description of sign]
1 Three-phase AC power supply 2 AC line filter 3 PWM cycloconverter (the main circuit section is composed of a unidirectional semiconductor switch element)
21 Three-phase AC motor
22 Power supply voltage detector
22a Power supply voltage instantaneous value
22b Power supply voltage phase
23 Controller
24 Gate signal synthesis unit
30 Input voltage information detector
31 to 36 Current detection circuit
37,304,403,404 Resistance
301,302, d1 ~ d18 diode
303 Photocoupler
305 Output terminal
40 Input voltage value (voltage level) detector
401 full-wave rectifier
402,64-66, C capacitor
405 DC reference voltage (Vcc)
406 Comparator
43 Normal operation mode (Mode 1)
44 Regenerative switching mode (Mode 2)
45 Base block mode (Mode 3)
46 Simple operation mode (Mode 4)
50 Protection gate signal generator
51-56 inverter (phase inverter)
61-63, L reactor Sru-Swt Directional unidirectional semiconductor switching element from input side r phase to output side u phase to output side w phase to input side t phase Up to 18 elements (p = r, s, t)
Sup, Svp, Swp One-way semiconductor switching element (n = r, s, t) having directivity from output side u phase or w phase to input side r phase or t phase
Snu, Snv, Snw One-way semiconductor switching element Vp having directionality from input side r phase or t phase to output side u phase or w phase Vp Maximum voltage Vm Intermediate voltage Vn Minimum voltage G1 Normal gate signal G2 output from controller Protective gate signal G2ur to G2tw output from the protective gate signal generating unit A unidirectional semiconductor gate switch to the unidirectional semiconductor switching device Sur having a direction from the u phase to the r phase or a unidirectional direction from the t phase to the w phase Protective gate signal G3 to the semiconductor switch element Stw Synthetic gate signal V1 obtained by synthesizing (logical sum) the protective gate signal with the normal gate signal V1 Voltage level (threshold) detection signal when an input low voltage occurs

Claims (2)

A bidirectional semiconductor switching element in which each phase of the three-phase AC power supply and each output phase are connected to each other in a direction opposite to each other and each element can be turned on and off independently. In a PWM cycloconverter of a power converter that is directly connected, an AC filter is provided on the input side, and a three-phase AC motor is provided on the output side,
Fault detection means for detecting a fault in the PWM cycloconverter and outputting a fault detection signal;
An input voltage information detecting means for detecting, as input voltage information, information on which the magnitude of the three-phase input voltage can be determined as a voltage at the three terminals on the input side of the bidirectional semiconductor switch element as a three-phase input voltage;
Based on the input voltage information, only the one-way semiconductor switch element from the output phase to the input phase that is the maximum voltage in the three-phase input voltage is turned on, or the minimum in the three-phase input voltage Regenerative switching means for turning on only the one-way semiconductor switch element from the input phase to be a voltage to each of the output phases;
And an input voltage value detecting means for detecting a voltage level from the input voltage value of the input side of the PWM cycloconverter,
When an input low voltage signal is generated during operation of the PWM cycloconverter (mode 1), power is regenerated to the capacitor part of the AC filter on the input side by the regenerative switching means (mode 2), and input during the power regeneration. An apparatus for protecting a PWM cycloconverter, characterized in that when the power supply voltage level exceeds a certain threshold value, electric switching (mode 4) for simply driving the AC motor by the power of the AC filter is performed .   2. The protection apparatus for a PWM cycloconverter according to claim 1, wherein the input voltage value detecting means includes a rectifier for three-phase full-wave rectification of the voltage on the input side, a rectified DC voltage, and a threshold DC that is a preset reference. 2. The protection device for a PWM cycloconverter according to claim 1, comprising a comparator for comparing the voltage.

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