KR100668104B1 - Compensator for 3-phase PWM rectifiers under switching device's fault - Google Patents

Abstract

An operation compensation device in case of a switch failure of a three-phase PWM rectifier, which determines a failure of a specific switching device by using a dq square comparison method, switches from a general switching vector method, and operates the three-phase PWM rectifier to a single-phase PWM rectifier. It is. The first comparator compares the output DC-link voltage from the PWM rectifier with the DC-link voltage command value and outputs a comparison result signal. The proportional integral controller controls the comparison result signal from the first comparator to proportionally integrate to obtain a maximum value of the input current. The first, second, and third current command value acquisition units synchronize the maximum value of the input current from the proportional integration controller with the phases of the first, second, and third input voltages, respectively, so as to synchronize the first phase and the second phase. The current command values of the phase and the third phase are obtained. The second, third, and fourth comparators compare the first, second, and third phase current command values from the first, second, and third current command value acquisition units with actual first, second, and third phases. Compare with the second and third phase input currents, respectively. The PWM controller determines whether the switching device has failed based on the outputs of the second, third, and fourth comparators, and controls the on / off of the plurality of switching devices according to the determination result. Outputs

Rectifiers, Switching Elements

Description

Compensator for 3-phase PWM rectifiers under switching device's fault}             

1 is a circuit diagram showing the configuration of a three-phase PWM AC-DC rectifier.

2 is an operation compensation device when a switch failure of the three-phase PWM rectifier according to an embodiment of the present invention.

3 is a view showing the characteristics of the normal operating state of the PWM rectifier.

4 is a diagram illustrating d-q rule of an input current in a normal operation state of a PWM rectifier.

5 is a diagram showing the characteristics of the PWM rectifier when a failure occurs in any switching element of the PWM rectifier.

Fig. 6 is a diagram showing d-q paths when a failure occurs in the upper switching element S1 of the PWM rectifier A phase.

Fig. 7 is a diagram showing d-q paths when a failure occurs in the PWM rectifier A phase lower switching element S4.

Fig. 8 is a diagram showing d-q paths when a failure occurs in the PWM rectifier B phase upper switching element S3.

9 is a diagram showing d-q rule when a failure occurs in the B-phase lower switching device S6 of the PWM rectifier.

Fig. 10 is a diagram showing d-q paths when a failure occurs in the PWM rectifier phase C upper switching element S5.

Fig. 11 is a diagram showing d-q paths when a failure occurs in the PWM rectifier C phase lower switching element S2.

12 is a diagram illustrating a method of switching to a single-phase PWM rectifier when a failure occurs in the A-phase upper switching device of the three-phase PWM rectifier.

Fig. 13 is a circuit diagram showing a state after the three-phase PWM rectifier is switched to a single phase PWM rectifier.

14 is a diagram illustrating a control method of a three-phase PWM rectifier operating mode.

15 is a diagram illustrating a control method of a single-phase PWM rectifier operating mode.

16 is a diagram illustrating a DC-link voltage after applying the driving compensation method according to the present invention.

17 illustrates an input voltage and a current after applying a driving compensation method according to the present invention.

<Description of Signs for Main Parts of Drawings>

202: first comparator 204: proportional integral control unit

206: First current command value acquisition unit 208: Second current command value acquisition unit

210: third current command value acquisition unit 212: second comparator

214: third comparator 216: PWM control unit

218: multiplier 220: fault generating circuit

The present invention relates to a PWM rectifier, and more particularly, a switch of a three-phase PWM rectifier capable of operating the rectifier normally by detecting when a power semiconductor switching element of the three-phase PWM AC-DC rectifier fails during operation. It relates to a driving compensation device in case of failure.

1 is a circuit diagram showing the configuration of a three-phase PWM AC-DC rectifier. In general, a three-phase PWM AC-DC rectifier consists of input three-phase voltages Va, Vb, and Vc, six-switch bridge circuits (S1 to S6), and a DC-link smoothing capacitor (Vd), as shown in FIG. do. These three-phase PWM AC-DC rectifiers are used in industrial applications as key devices in industrial processes such as plating, telecommunications, electric furnaces, train drives, high voltage DC transmission (HVDC), and flexible AC transmission (FACT). It occupies a very large market. In addition, the PWM rectifier is mainly related to the control part of the power part of the industrial equipment, so a short period of shutdown will cause a huge loss of the entire product production, especially in the case of a device installed in a place such as a hospital, Shutdowns cause big problems that are directly linked to human life. Therefore, in order to prevent this, a method of separately installing a spare device is used, but since the price of the device is very expensive, this situation is also a large economic burden.

Therefore, the method of increasing the operation reliability of the PWM rectifier is the most important. The most frequent cause of the failure of the PWM rectifier is the failure of a power semiconductor switching element composed of semiconductors. Since the power semiconductor switching device is composed of a semiconductor, it is a sensitive device that is decisively influenced by its lifetime due to abnormal operation for a very short time. If any of the six switching elements constituting the PWM rectifier fails during operation, the current PWM rectifier is stopped and the operator checks the six switching elements one by one to replace the failed switching element. In such a case, it is difficult to secure manpower for inspection, and it is very difficult to check it efficiently due to the large number of parts. In addition, the inspection time must be avoided, so the inspection time is short, and much labor is required. Moreover, as described above, specifying the PWM rectifier is not a suitable method because it directly affects product production and human life. As such, the lack of a method of increasing operating reliability for the PWM rectifier not only causes a problem in ensuring the safety of the PWM rectifier, but also causes a serious problem in the economic inefficiency of the device.

This establishment of a method to increase the operation reliability of the PWM rectifier not only means safe operation of the device, but also increases the stability of the entire system equipped with the PWM rectifier, and increases the availability of expensive equipment. In other words, the economic added value is important.

In general, six switching elements can generate 2³ = 8 PWM switching vectors. The eight switching vectors are (0,0,0), (0,0,1), (0,1,0), (0,1,1),

(1,0,0), (1,0,1), (1,1,0), and (1,1,1). One switching vector consists of three numbers, and represents the state of switching elements of A phase, B phase, and C phase, respectively. That is, '0' represents a state in which the upper switching element is off and the lower switching element is on, and '1' represents a state in which the upper switching element is on and the lower switching element is off. If any one of these switching elements fails and fails to operate, the general switching vector cannot be constructed and the PWM rectifier can no longer be operated. For this reason, until now, when a switching device fails, the current method is to immediately stop the operation of the PWM rectifier and find and replace the failed switching device.

Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, and after determining the failure of a specific switching device by using a general dq square comparison method, the three-phase PWM rectifier is separated from the general switching vector method. It is an object of the present invention to provide an operation compensation device in the case of a switch failure of a three-phase PWM rectifier that can be operated by switching to a single-phase PWM rectifier.

The present invention includes a power semiconductor switching device having a plurality of switching elements, the main circuit is configured to convert the three-phase input voltage of the main circuit into a DC voltage of the desired size and to synchronize the phase of the current to improve the input power factor A first comparator for outputting a comparison result signal by comparing the output DC-link voltage from the three-phase PWM rectifier including a controller with a DC-link voltage command value;

A proportional integral controller configured to proportionally integrate a comparison result signal from the first comparator to obtain a maximum value of an input current;

A first, second, and third phase current command value synchronized with the maximum value of the input current from the proportional integration controller and the phases of the first, second, and third input voltages, respectively; A second and third current command value acquisition unit;

The first, second, and third phase current command values from the first, second, and third current command value acquisition units are respectively compared with the actual first, second, and third phase input currents. Comparing second, third, and fourth comparators; And

Determining whether the switching device has failed based on the outputs of the second, third, and fourth comparators, and outputting a pulse width modulated signal for controlling on / off of the plurality of switching devices according to a determination result. Provided is an operation compensation device in case of a switch failure of a three-phase PWM rectifier including a PWM control unit.

Preferably, the first, second, third, and fourth comparators are adders, respectively. More preferably, the first, second, and third current command value acquisition units are respectively multipliers. Most preferably, the multiplier forcibly turns off another switching element of the same phase as the faulty switching element to electrically disconnect the faulty switching element from the PWM rectifier, and wherein the three phase PWM rectifier It is transformed into a single phase PWM rectifier.                         

According to the embodiment, the failure of the first phase, the second phase, and the third phase switching element is determined through the dq rule. In addition, the normally operating switching element and the failed switching element output dq paths of different input currents. Moreover, the power semiconductor switching element is SCR, BJT, MOSFET, IGBT, GTO, or IGCT. The operation compensator for a switch failure of a three-phase PWM rectifier further includes a fault generating circuit for generating a fault generating signal and a multiplier for multiplying the pulse width modulation signal from the PWM control unit with the fault generating control signal from the fault generating circuit. do.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a circuit diagram showing the configuration of a three-phase PWM AC-DC rectifier. 2 is an operation compensation device when a switch failure of the three-phase PWM rectifier according to an embodiment of the present invention. 3 is a view showing the characteristics of the normal operating state of the PWM rectifier. As shown in Fig. 1, the PWM rectifier includes input three-phase voltages Va, Vb, and Vc, six-switch bridge circuits S1-S6, and a DC-link smoothing capacitor Vd.

An operation compensating apparatus for a switch failure of a three-phase PWM rectifier according to an exemplary embodiment of the present invention includes a first comparator 202, a proportional integration controller 204, first, second, and third current command value acquisition units 206 and 208. And 210, second, third, and fourth comparators 212, 214, and 216, a PWM control unit 218, a multiplier 220, and a fault generating circuit 222.

The first comparator 202 is provided with a power semiconductor switching element having a plurality of switching elements, the main circuit is configured, and converts the three-phase input voltage of the main circuit into a DC voltage of a desired size and synchronizes the phase of the current. The output DC-link voltage from the three-phase PWM rectifier 200 including the controller for improving the power factor is compared with the DC-link voltage command value and outputs a comparison result signal.

The proportional integration control unit 204 obtains the maximum value of the input current by proportional integration control of the comparison result signal from the first comparator 202.

The first, second, and third current command value acquisition units 206, 208, and 210 are configured to provide the maximum value of the input current from the proportional integration controller 204 and the first, second, and third input voltages. The current command values of the first phase, the second phase, and the third phase are obtained by synchronizing with the phases of. According to an embodiment of the present invention, the first, second, and third current command value acquisition units 206, 208, and 210 are preferably multipliers, respectively.

Second, third, and fourth comparators 212, 214, and 216 are configured to provide the first, second, and third current command value acquisition units 206, 208, and 210 from the first, second, and third comparators. The current command values of the two-phase and the third phase are compared with the actual first, second, and third phase input currents, respectively. According to an embodiment of the present invention, the first, second, third and fourth comparators are preferably adders.

The PWM controller 218 determines whether the switching device has failed based on the outputs of the second, third, and fourth comparators 212, 214, and 216, and according to the determination result, the plurality of switching devices. Outputs a pulse width modulated signal for controlling the on / off of the signal. The failure generation circuit 222 generates a failure occurrence signal. A multiplier 220 multiplies the pulse width modulation signal from the PWM control unit with the failure generation control signal from the failure generation circuit.

The multiplier 220 forcibly turns off another switching element of the same phase as the faulty switching element to electrically disconnect the faulty switching element from the PWM rectifier 200 and, by the electrical separation, the three-phase PWM rectifier. It is preferable to operate with a single phase PWM rectifier. According to the present invention, failure of the first phase, second phase, and third phase switching elements is determined through the d-q rule.

More preferably, the normally operating switching element and the failed switching element output d-q paths of different input currents. The power semiconductor switching element may be SCR, BJT, MOSFET, IGBT, GTO, or IGCT.

Referring to FIG. 2, in order to obtain a DC-link voltage having a desired magnitude and to control an input power factor, the DC-link voltage Vd is detected and compared by the comparator 202 with the DC-link voltage command value Vd_ref and then proportionally integrated. Through the controller 204, the maximum value Is_peak of the input current is obtained. The first, second, and third current command value acquisition units 206, 208, and 210 are provided with the phases sinwt, sin (wt-120), and sin (wt-240) of the input voltages at the maximum value Is_peak of the input current. ) Are synchronized to obtain current command values Is_a_ref, Is_b_ref, and Is_c_ref of each phase.

The second, third, and fourth comparators 212, 214, and 216 are configured to obtain actual three-phase input currents Ia, Ib, and Ic from the first, second, and third current command value acquisition units 206, 208, And 210 compare the current command values Is_a_ref, Is_b_ref, and Is_c_ref. Thereafter, the PWM control unit 218 generates a PWM signal for operating each of the six switches. A signal is generated from the fault generating circuit 222 for generating a fault in any switching element during the operation of the PWM rectifier, causing a fault in any switching element during the operation.

3 is a view showing the characteristics of the normal operating state of the PWM rectifier, the DC-link voltage, the A-phase voltage / current, the B-phase voltage / current, and the C-phase voltage / current waveform is shown from the top. As shown in FIG. 3, when the PWM rectifier operates normally, the DC-link voltage is controlled to a constant value and the input voltage and current are controlled in phase. In addition, looking at the d-q rule of the input current at this time, as shown in Figure 4 almost circular.

5 is a diagram showing the characteristics of the PWM rectifier when a failure occurs in any switching element of the PWM rectifier. Compared with FIG. 3, it can be seen that the DC-link voltage is not constantly controlled and severe distortion occurs. In addition, off-set occurs in the input current, and the waveform is distorted, resulting in deterioration of the input power factor. Able to know. This is due to the switching vector described above not being generated correctly.

6 to 11 show the arrangement of the six switching elements constituting the PWM rectifier. The failure of phase A upper switch S1 is shown in FIG. 6, the failure of phase A lower switch S4 is shown in FIG. 7, the failure of phase B upper switch S3 is shown in FIG. 8, and the failure of phase B lower switch S6 is shown in FIG. 9, the failure of phase C upper switch S5 is shown in FIG. 10, and the failure of phase C lower switch S2 is shown in FIG. As can be seen in the drawings, the d-q rule according to the failure of each switching device shows a distinct change, from which it can be determined whether a problem occurs in the switching device during the PWM rectifier operation.

12 is a description of a driving compensation method according to the present invention. 12 is a diagram illustrating a method of switching to a single-phase PWM rectifier when a failure occurs in the A-phase upper switching device S1 of the three-phase PWM rectifier. When a failure occurs in the A phase upper switching element S1, the other switching element S4 of the A phase is forcibly turned off to electrically disconnect the A phase in which the failure occurs from the PWM rectifier. When the electrical separation is performed in this way, the three-phase PWM rectifier 200 can be used by modifying the circuit to a single-phase PWM rectifier as shown in FIG. This conversion to a single-phase rectifier, the voltage of the remaining two phases, that is, the B and C phases that do not cause a failure to be merged into one, and the inductors inserted into the B and C phases also merge into one, more than in the case of a three-phase rectifier 2 times larger value, 2L input inductance. After the conversion as in the circuit shown in FIG. 13, the PWM rectifier is controlled by newly configuring the switching vector with the remaining four switching elements except for the failed switching element S1 and the switching element S4 on the same phase as the element. Done. The newly formed switching vectors are 2 2 = 4, which is equal to (0,0), (0,1), (1,0), (1,1).

The controller used in the PWM rectifier includes a three-phase operation mode program and a single-phase operation mode program at the same time. After determining that the switching device has failed from the input current, the controller immediately switches to the operation mode within about one second. 14 is a diagram illustrating a control method of a three-phase PWM rectifier operating mode. 15 is a diagram illustrating a control method of a single-phase PWM rectifier operating mode.

As such, the PWM rectifier operating characteristics when the driving compensation apparatus according to the present invention is applied are illustrated in FIGS. 16 and 17. In comparison with the results of FIG. 5, after the failure, in FIG. 5, the severe distortion occurs in the DC-link voltage and the input current, but after the operation compensation method is applied, both the DC-link voltage and the input current are well controlled. It can be confirmed. The more ripple component appears in the waveforms in the single-phase operation mode than in the three-phase operation mode, because the switching vectors are reduced from eight to four. Through this, when the three-phase PWM rectifier has a failure in the switching device, it is determined which switching device has a problem without stopping during operation, and then forcibly turns off another switching device of the same phase as the failed switching device. It can be seen that the faulty switching element is separated from the PWM rectifier and the three-phase PWM rectifier is converted to a single phase PWM rectifier and continuously operated by the electrical separation.

Although the present invention has been described as a specific preferred embodiment, the present invention is not limited to the above-described embodiments, and the present invention is not limited to the above-described embodiments without departing from the gist of the present invention as claimed in the claims. Anyone with a variety of variations will be possible.

As described above, according to the present invention, after the three-phase input current is continuously detected during the normal operation of the PWM rectifier 200 and converted through the d-q conversion equation, the state of the switching elements is continuously monitored through the d-q rule. When a problem occurs in the switching element, the d-q rule shows a different rule for each of the six switching elements, so that it can be known whether the problem occurs in which switching element. Since the method of using the d-q rule is well known, a detailed description thereof will be omitted. After detecting the fault condition of the PWM rectifier through the d-q rule, normal operation, that is, DC-link voltage control and input power factor control, may be performed using only the remaining switching elements in which the fault does not occur. That is, the present invention relates to an operation compensation method capable of operating normally without interrupting the operation of a rectifier when a power semiconductor switching element, which is a main component that determines lifetime and operation characteristics, of the PWM rectifier. This ensures the safe operation of the PWM rectifier and maximizes the full utilization of expensive equipment.

Claims (9)

The main circuit is composed of a power semiconductor switching element having an adder and having a plurality of switching elements. The input power factor is improved by converting the three-phase input voltage of the main circuit into a DC voltage of a desired size and synchronizing the phase of the current. A first comparator for outputting a comparison result signal by comparing the output DC-link voltage from the three-phase PWM rectifier with a DC-link voltage command value; A proportional integral controller configured to proportionally integrate a comparison result signal from the first comparator to obtain a maximum value of an input current; A current command value of the first phase, the second phase, and the third phase, each made of a multiplier and synchronized with the maximum value of the input current from the proportional integration controller and the phases of the first, second, and third input voltages, respectively. First, second, and third current command value acquisition units for obtaining the first and second current command values; An adder and converts the first, second, and third phase current command values from the first, second, and third current command value acquisition units into actual first, second, and third phases; Second, third, and fourth comparators, each comparing with an input current; And Determining whether the switching device has failed based on the outputs of the second, third, and fourth comparators, and outputting a pulse width modulated signal for controlling on / off of the plurality of switching devices according to a determination result. The multiplier includes a PWM control unit, and the multiplier forcibly turns off another switching element of the same phase as the faulty switching element to electrically disconnect the faulty switching element from the PWM rectifier. Operation compensation device in case of switch failure of a three-phase PWM rectifier, characterized in that the modified operation to a single-phase PWM rectifier. delete delete delete The operation compensation device of claim 1, wherein the failure of the first, second, and third phase switching elements is determined based on the d-q rule. The operation compensation device of claim 1, wherein the normally operating switching element and the failed switching element output d-q paths of different input currents. The apparatus of claim 1, wherein the power semiconductor switching element is an SCR, a BJT, a MOSFET, an IGBT, a GTO, or an IGCT. The operation compensation device of claim 1, further comprising a failure generation circuit for generating a failure generation signal. The operation failure compensation device according to claim 8, further comprising a multiplier for multiplying a pulse width modulation signal from the PWM control unit and a failure generation control signal from the failure generation circuit.

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