JP2016010295A - Testing method of converter, and testing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a testing method and a testing device for giving a duty equal to a real operational state to a converter of MMC by means of a simple circuit.SOLUTION: A testing method including a connection step and a supply step is provided. In the connection step, a plurality of converters are bridge-connected by a bridge circuit. The converter includes first and second switching elements and a charge storage element. The bridge circuit includes a pair of input terminals connected to a DC power source, first to fourth arm parts and an AC load. In the supply step, a voltage reference in a sinusoidal wave shape is set for the unit of the plurality of converters, and voltages at a first connection point and a second connection point are controlled to be matched with the voltage reference, respectively, thereby applying a voltage to the AC load.

Description

  Embodiments described herein relate generally to a testing method and a testing apparatus for a transducer.

  There is a power conversion device of a system called a modular multilevel converter (hereinafter referred to as MMC). In MMC, a unit converter called a chopper cell is used. As the unit converter, a self-extinguishing type switching element capable of on / off control, such as an IGBT (Insulated Gate Bipolar Transistor), is used. For example, a plurality of unit converters are connected in series. Thereby, a voltage higher than the withstand voltage of the switching element can be output.

  For large-capacity power converters used in DC power transmission systems, etc., verify the operation by giving the unit converter duties equal to or greater than the current and voltage input under actual usage conditions before actual operation. Has been done.

  For example, in a conversion device in which a plurality of switching elements are bridge-connected, when the switching elements are turned on / off by comparing a triangular wave carrier wave with a sine wave voltage reference, an output is made with respect to the voltage reference value of the first phase. It has been proposed to set the voltage reference value of the second phase so that the phase of the line voltage is a phase advanced by 90 °. As a result, the phase of the current flowing through the AC load is substantially in phase with the voltage reference value of the first phase, and with a simple test circuit, the power factor equivalent to the actual operating state is applied to the switching element of the first phase. Voltage / current duty can be given in one operation. Further, by adjusting the voltage reference value of the second phase, it is possible to give an operation duty of an arbitrary power factor equivalent to the actual operation state. Furthermore, by adjusting the voltage reference value of the second phase, it is possible to reverse the direction of the power and to give the driving duty in the regenerative operation.

  However, in MMC, the unit converter itself includes a charge storage element (such as a capacitor) and a plurality of switching elements. For this reason, the test method in the case where a plurality of switching elements are single-phase bridges cannot be directly applied to the MMC. For this reason, even in the case of MMC, it is desired that the unit converter can be given the same responsibility as the actual operation state with a simple circuit.

JP-A-11-285265

  Embodiments of the present invention provide a test method and a test apparatus capable of giving a duty equivalent to an actual operation state to a unit converter of an MMC with a simple circuit.

  According to the embodiment of the present invention, there is provided a test method for a converter including a connecting step and a supplying step. In the connection step, a plurality of converters to be tested are bridge-connected by a bridge circuit. Each of the plurality of converters is connected in parallel to a first switching element, a second switching element connected in series to the first switching element, and the first switching element and the second switching element. Charge storage elements. The bridge circuit includes a pair of input terminals electrically connected to a DC power source, a first arm part electrically connected to one of the pair of input terminals, the first arm part, and the pair of inputs. A second arm portion electrically connected to the other of the terminals, a third arm portion electrically connected to the one of the pair of input terminals, the third arm portion and the pair of inputs. A fourth arm portion electrically connected to the other of the terminals, one end electrically connected to a first connection point of the first arm portion and the second arm portion, and the third arm portion. And an AC load including the other end electrically connected to the second connection point between the arm portion and the fourth arm portion. In the connecting step, at least one of the plurality of converters is connected to each of the first arm part to the fourth arm part. The supplying step sets a voltage reference in which a sinusoidal AC voltage component and a DC voltage component are superimposed for each of the plurality of converters, the voltage at the first connection point, and the AC voltage component at the second connection point. Controls the switching of the first switching element and the second switching element so as to coincide with the AC voltage components of the respective voltage references. That is, the amplitude and phase of the AC voltage component in each voltage reference of the plurality of converters are adjusted so that the AC voltage applied to the AC load has a predetermined amplitude and phase. As a result, the AC voltage of the AC load is controlled to obtain a desired current, and a voltage / current duty equivalent to the actual operation is given to the switching elements of the first arm part and the second arm part. In the following, the operation of supplying power to the AC load will be described as an example. However, since it is clear that the regenerative operation can be performed by adjusting the voltage reference, the description of the operation is omitted.

  Provided are a test method and a test apparatus capable of giving the MMC unit converter a duty equivalent to an actual operation state with a simple circuit.

1 is a block diagram schematically illustrating a test apparatus according to an embodiment. It is a graph which represents typically operation | movement of a control circuit. It is a vector diagram which represents typically operation | movement of a control circuit. It is a functional block diagram showing typically operation of a control circuit. It is a flowchart which represents typically the procedure of the testing method of a converter. It is a block diagram showing typically another bridge circuit concerning an embodiment. It is a block diagram showing typically another bridge circuit concerning an embodiment. It is a block diagram showing typically another converter concerning an embodiment.

Each embodiment will be described below with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between the parts, and the like are not necessarily the same as actual ones. Further, even when the same part is represented, the dimensions and ratios may be represented differently depending on the drawings.
Note that, in the present specification and each drawing, the same elements as those described above with reference to the previous drawings are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

FIG. 1 is a block diagram schematically illustrating a test apparatus according to the embodiment.
As shown in FIG. 1, the test apparatus 10 includes a bridge circuit 12 and a control circuit 14. The bridge circuit 12 includes a pair of input terminals 20a and 20b, first to fourth four arm portions 21a to 21d, and an AC load 22.

  The pair of input terminals 20 a and 20 b are electrically connected to the DC power supply 4. The input terminal 20 a is connected to the positive electrode of the DC power supply 4, and the input terminal 20 b is connected to the negative electrode of the DC power supply 4. The DC power source 4 is a rectifier that converts AC power supplied from a commercial power source or the like into DC power, for example. The DC power source 4 may be any power source that can supply DC power. The DC power supply 4 may be provided in the test apparatus 10 or may be provided separately from the test apparatus 10.

  The first arm portion 21a is electrically connected to the input terminal 20a. The second arm portion 21b is electrically connected between the first arm portion 21a and the input terminal 20b. That is, the first arm portion 21 a and the second arm portion 21 b are connected in series to the DC power supply 4. The third arm portion 21c is electrically connected to the input terminal 20a. The fourth arm portion 21d is electrically connected between the third arm portion 21c and the input terminal 20b. That is, the third arm part 21c and the fourth arm part 21d are connected in parallel to the first arm part 21a and the second arm part 21b.

  In the bridge circuit 12, the first leg LG1 is constituted by the first arm portion 21a and the second arm portion 21b, and the second leg LG2 is constituted by the third arm portion 21c and the fourth arm portion 21d. That is, in this example, the bridge circuit 12 is a two-leg, four-arm single-phase bridge. The first arm portion 21a is a positive arm of the first leg LG1, and the second arm portion 21b is a negative arm of the first leg LG1. The third arm portion 21c is a positive arm of the second leg LG2, and the fourth arm portion 21d is a negative arm of the second leg LG2. The bridge circuit 12 may be, for example, a three-leg, six-arm three-phase bridge.

  The converter 30 which is a test object is connected to each arm part 21a-21d. That is, in this example, four converters 30 are connected to the bridge circuit 12. The bridge circuit 12 connects the converters 30 connected to the arm portions 21a to 21d in a bridge shape. Each of the arm portions 21a to 21d has, for example, a pair of connection terminals t1 and t2, and is detachably connected to the converter 30 via the pair of connection terminals t1 and t2. In this example, one converter 30 is connected to each of the arm portions 21a to 21d. A plurality of converters 30 connected in series (cascade connection) may be connected to each of the arm portions 21a to 21d.

  In addition, a DC reactor 23 is provided in each of the arm portions 21a to 21d. That is, each of the arm portions 21 a to 21 d includes a pair of connection terminals t 1 and t 2 and a DC reactor 23. The DC reactor 23 is connected in series with the converter 30 connected to the connection terminals t1 and t2. More specifically, the DC reactors 23 of the first arm portion 21a and the third arm portion 21c that are the positive side arms are electrically connected to the connection terminal t2. The DC reactors 23 of the second arm portion 21b and the fourth arm portion 21d, which are negative arms, are electrically connected to the connection terminal t1.

  FIG. 1 shows an example of the arrangement of the DC reactor 23. The arrangement of the DC reactor 23 is between the first arm portion 21a and the input terminal 20a (the positive terminal of the DC power supply 4), or between the second arm portion 21b and the input terminal 20b (the negative terminal of the DC power supply 4). You may install in between. That is, one unit between the positive terminal of the DC power source 4 and the first connection point CP1 of the first leg LG1 and one unit between the first connection point CP1 and the negative terminal of the DC power source 4 are the same. Action and effect are obtained. The same applies to the second leg LG2.

  The converter 30 includes a first switching element 31, a second switching element 32, and a charge storage element 33. The first switching element 31 and the second switching element 32 include a pair of main terminals and a control terminal. The control terminal controls a current flowing between the pair of main terminals. For the first switching element 31 and the second switching element 32, for example, a self-extinguishing element such as an IGBT is used. The pair of main terminals is, for example, an emitter and a collector, and the control terminal is, for example, a gate.

  The pair of main terminals (current paths) of the second switching element 32 are connected in series to the pair of main terminals of the first switching element 31. The charge storage element 33 is connected to the first switching element 31 and the second switching element 32 in parallel. For example, a capacitor or a storage battery is used for the charge storage element 33.

  Further, a diode 34 is connected to the first switching element 31 in antiparallel with the pair of main terminals. The forward direction of the diode 34 is opposite to the direction of the current flowing between the pair of main terminals of the first switching element 31. Similarly, a diode 35 is connected to the second switching element 32 in antiparallel with the pair of main terminals.

  That is, in this example, the converter 30 is a bidirectional chopper. The first switching element 31 is a so-called high side switch, and the second switching element 32 is a so-called low side switch.

  The converter 30 is a two-terminal element including a pair of terminals 30a and 30b. The terminal 30 a is connected between the first switching element 31 and the second switching element 32. The terminal 30b is connected to the main terminal on the opposite side of the main terminal connected to the first switching element 31 of the second switching element 32. The connection terminal t1 is electrically connected to the terminal 30a. The connection terminal t2 is electrically connected to the terminal 30b.

  As a result, the test apparatus 10 configures an MMC power conversion apparatus by the bridge circuit 12 and each converter 30. Each converter 30 may be called a chopper cell, for example.

  One end of the AC load 22 is electrically connected between the first arm portion 21a and the second arm portion 21b. The other end of the AC load 22 is electrically connected between the third arm portion 21c and the fourth arm portion 21d. That is, the AC load 22 is electrically connected to the AC output of the bridge circuit 12. The AC load 22 is, for example, a reactor. For the AC load 22, for example, an inductance through which a rated current flows when each converter 30 is rated operated, that is, when each converter 30 is operated at a rated frequency, a rated current, and a rated voltage is selected.

  Hereinafter, the voltage at the first connection point CP1 between the first arm portion 21a and the second arm portion 21b is referred to as a first AC output voltage. The first AC output voltage is the AC output of the first leg LG1. The voltage at the second connection point CP2 between the third arm portion 21c and the fourth arm portion 21d is referred to as a second AC output voltage. The second AC output voltage is an AC output of the second leg LG2. The AC load voltage applied to the AC load 22 is adjusted by the first AC output voltage and the second AC output voltage.

  The test apparatus 10 converts DC power supplied from the DC power supply 4 into AC power and supplies it to the AC load 22. The test apparatus 10 gives each converter 30 responsibility equal to or higher than the current and voltage input under the usage conditions, and verifies the operation of each converter 30.

  In the MMC, the capacity can be increased by increasing the number of converters 30 connected in cascade, and it is possible to cope with several tens to several hundreds MW classes. In a large-capacity MMC, for example, several tens to a hundred converters 30 are cascade-connected. For this reason, if the test is to be performed with the same configuration as the usage situation, a large-capacity simulated load and a large-capacity test power supply are required, which leads to an increase in the size of test equipment and an increase in contract power. For example, the test cost increases.

  In the test apparatus 10, operation verification of each converter 30 of the MMC is performed for each converter 30. The test apparatus 10 simulates the voltage and current supplied for each converter 30 cascaded in an actual usage situation, for example. Thereby, in the test apparatus 10, operation | movement of the converter 30 can be verified, without causing the enlargement of a test facility and the increase in contract electric power.

  The control circuit 14 controls switching of the first switching element 31 and the second switching element 32 of each converter 30. The control circuit 14 is connected to the respective control terminals of the first switching element 31 and the second switching element 32, and controls the switching of each switching element 31, 32 by a voltage applied to the control terminal. Thereby, the control circuit 14 controls conversion from DC power to AC power. The control circuit 14 converts the DC power supplied from the DC power supply 4 into AC power and supplies it to the AC load 22 by controlling the switching of the switching elements 31 and 32.

  Here, the DC voltage of the charge storage element 33 is referred to as voltage VC. A voltage between the connection terminals t1 and t2 is referred to as a cell voltage. The voltage of each arm part 21a-21d is called arm voltage. In this example, the arm voltage is the same as the cell voltage. When each of the arm units 21 a to 21 d includes a plurality of converters 30, the arm voltage is the sum of the cell voltages of the respective converters 30.

  The voltages of the first leg LG1 and the second leg LG2 are referred to as leg voltages. The leg voltage of the first leg LG1 is the sum of the arm voltage of the first arm portion 21a and the arm voltage of the second arm portion 21b. The leg voltage of the second leg LG2 is the sum of the arm voltage of the third arm portion 21c and the arm voltage of the fourth arm portion 21d.

  The control circuit 14 turns on and off the first switching element 31 and the second switching element 32 alternately. When the first switching element 31 is turned on and the second switching element 32 is turned off, the cell voltage is substantially the same as the voltage VC of the charge storage element 33. When the first switching element 31 is turned off and the second switching element 32 is turned on, the cell voltage is substantially zero.

  The control circuit 14 controls the arm voltages of the arm portions 21a to 21d by turning on and off the switching elements 31 and 32, respectively. Thereby, the control circuit 14 controls the voltage applied to the AC load 22. The control circuit 14 converts the DC voltage of the DC power supply 4 into an AC voltage and applies it to the AC load 22.

Bridge circuit 12 further includes a voltage detection unit 24 and a current detection unit 25.
The voltage detection unit 24 is provided in each converter 30. In this example, four voltage detection units 24 are provided in the bridge circuit 12. The voltage detector 24 detects the voltage VC of the charge storage element 33. The voltage detection unit 24 is attached to, for example, the charge storage element 33 of the connected converter 30. For example, the voltage detector 24 may be provided in the converter 30 itself. Each voltage detection unit 24 is electrically connected to the control circuit 14. The control circuit 14 detects the voltage VC of each converter 30 based on the detection result of each voltage detection unit 24.

  The current detection unit 25 is provided in each of the arm units 21a to 21d. In this example, four current detection units 25 are provided in the bridge circuit 12. Each current detection unit 25 detects a current flowing through each arm unit 21a to 21d. Each current detection unit 25 is, for example, a direct current transformer called a Hall CT. Each current detection unit 25, for example, covers the outer periphery of the conducting wire connected to each of the arm units 21a to 21d, and detects a current flowing through the conducting wire by a change in magnetic field. Below, the electric current which flows into each arm part 21a-21d is called arm current. Each current detection unit 25 is electrically connected to the control circuit 14. The control circuit 14 detects the arm current of each of the arm units 21a to 21d based on the detection result of each current detection unit 25.

  Hereinafter, the direct current flowing through each leg LG1, LG2 is referred to as a leg current. The leg current of the first leg LG1 is the sum of the arm current of the first arm portion 21a and the arm current of the second arm portion 21b. The leg current of the second leg LG2 is the sum of the arm current of the third arm portion 21c and the arm current of the fourth arm portion 21d.

  Based on the voltage VC detected by the voltage detector 24 and the arm current detected by the current detector 25, the control circuit 14 sets the switching elements 31, 32 so that the voltage VC is substantially constant. Controls switching.

FIG. 2 is a graph schematically showing the operation of an example of the control circuit.
As shown in FIG. 2, the control circuit 14 controls on / off of the switching elements 31 and 32 based on the carrier wave CW and the voltage reference VR. The control circuit 14 sets a voltage reference VR for each converter 30. In other words, in this example, the control circuit 14 sets four voltage references VR corresponding to the four converters 30 connected to the arm portions 21a to 21d. On the other hand, the carrier wave CW is commonly used for each of the converters 30. The voltage reference VR is, for example, a sine wave. The control circuit 14 adjusts the amplitude and phase of the voltage reference VR for each converter 30. The frequency of the voltage reference VR is set according to the frequency of the AC voltage applied to the AC load 22. That is, the frequency is set according to the actual use situation. The frequency of the voltage reference VR is, for example, 50 Hz or 60 Hz. The carrier wave CW is, for example, a triangular wave. The carrier wave CW may be a sawtooth wave or the like. Thus, the control circuit 14 controls the switching of the switching elements 31 and 32 by matching the voltage reference VR with the carrier wave CW.

  Further, the control circuit 14 may be any circuit that operates so that the AC voltage component and the DC voltage component of the voltage appearing at the input terminal of the converter 30 coincide with the voltage reference VR. For example, an off-off pattern of each switching element 31 and 32 may be calculated offline, the pattern stored in a memory, and a pulse pattern generated.

  In the following, for the sake of simplicity of explanation, a control method for generating a switching pulse from the voltage reference VR and the carrier wave CW will be described. However, other control methods in which the input terminal voltage of the converter is equivalent may be used. It is clear that similar actions and effects can be obtained.

  The control circuit 14 compares the voltage reference VR with the carrier wave CW. The control circuit 14 turns on the first switching element 31 and turns off the second switching element 32 when the voltage reference VR is equal to or higher than the carrier wave CW. Then, the control circuit 14 turns off the first switching element 31 and turns on the second switching element 32 when the voltage reference VR is less than the carrier wave CW.

FIG. 3 is a vector diagram schematically showing the operation of the control circuit.
As illustrated in FIG. 3, the control circuit 14, for example, sets the voltage of each converter 30 so that the phase of the AC load voltage is 90 ° ahead of the first AC output voltage of the first leg LG <b> 1. The amplitude and phase of the AC voltage component of the reference VR are adjusted.

  The phase of the AC load current flowing through the AC load 22 is 90 ° behind the AC load voltage. Therefore, by adjusting the amplitude and phase of the AC voltage component of each voltage reference VR as described above, the phase of the AC load current is substantially in phase with the phase of the first AC output voltage. This is substantially the same as the state where each converter 30 of the first leg LG1 is operating with a power factor of 1. Thereby, the voltage / current duty of the power factor 1 equivalent to an actual driving | operation can be given to each converter 30 of 1st leg LG1. Moreover, the electric power supplied from the DC power source 4 is approximately the loss of each converter 30 and the loss of the AC load 22, and power consumption can be suppressed.

  Further, by adjusting the amplitude and phase of the AC voltage component of the second AC output voltage, the amplitude and phase of the AC load voltage with respect to the first AC output voltage can be arbitrarily adjusted. That is, it is possible to give a voltage / current duty having an arbitrary power factor equivalent to that in actual operation. Thereby, for example, when testing a plurality of types of converters 30 with different operating conditions, it is possible to eliminate the need to prepare an AC load 22 for each type of converter 30. That is, the control circuit 14 adjusts the amplitude and phase of the voltage reference VR of each converter 30 so that the AC load voltage has a predetermined amplitude and phase with respect to the first AC output voltage of the first leg LG1.

FIG. 4 is a functional block diagram schematically showing the operation of the control circuit.
FIG. 4 shows a portion of the control circuit 14 corresponding to the first leg LG1. The configuration of the portion corresponding to the second leg LG2 is substantially the same as the configuration of the portion corresponding to the first leg LG1. The second leg LG2 can be controlled with substantially the same control configuration as the first leg LG1, although the control reference and the feedback signal are different. Therefore, here, a portion of the control circuit 14 corresponding to the first leg LG1 will be described, and a description of a portion corresponding to the second leg LG2 will be omitted.

  As illustrated in FIG. 4, the control circuit 14 includes an average value calculation unit 40 that calculates an average value of the DC voltage detection values of the converters 30 of the respective arm units 21 a and 21 b constituting the first leg LG <b> 1, and a direct current A voltage average value control unit 41, a DC current calculation unit 42 for calculating a DC current flowing in the first leg LG1 from the current detection values of the two converters 30 constituting the first leg LG1, a DC current control unit 43, The DC voltage individual control unit 44 that individually controls the DC voltage of each of the arm units 21a and 21b by using the DC voltage detection values of the arm units 21a and 21b as inputs, and calculators 45 to 48 are included.

  The average value calculation unit 40 calculates the average value of the voltage VC (DC voltage) of the charge storage element 33 of each converter 30 detected by each voltage detection unit 24. In this example, two DC voltage detection values of the two converters 30 connected to the arm portions 21a and 21b are input. For example, when a total of four converters 30 are connected to each of the arm units 21 a and 21 b, four DC voltage detection values are input to the average value calculation unit 40. The calculator 45 calculates the difference between the average value calculated by the average value calculator 40 and the DC voltage reference value of the voltage VC.

  The DC voltage reference value is set in accordance with the actual driving situation. The DC voltage reference value is set to the voltage of the charge storage element 33 per one of the converters 30 that are cascade-connected in the actual operation situation. For example, in an actual use situation, when 100 converters 30 are cascade-connected to one arm and the arm voltage of the arm is 100 kV, the DC voltage reference value is set to 1 kV.

  The difference calculated by the calculator 45 is input to the DC voltage average value control unit 41. The DC voltage average value control unit 41 calculates the command value of the circulating current flowing through the arm units 21a and 21b from the input difference by PI control, for example. In the MMC, it is necessary to keep a constant current for direct current flowing in each of the arm portions 21a to 21d. This DC current does not appear in the AC load 22 but becomes a circulating current between the arms. The average value of the voltage VC of each converter 30 is controlled by correcting this direct current. Note that the calculation of the circulating current command value by the DC voltage average value control unit 41 is not limited to PI control, and other general control methods such as PID control and IP control, modern control theory, and the like are used. It may be used.

  The direct current calculation unit 42 calculates the direct current flowing through the first leg LG1 from the detected current values of the two converters 30 constituting the first leg LG1. As an example of the DC current calculation method, there is a method of calculating an average of the current detection value of the first arm portion 21a and the current detection value of the second arm portion 21b. The difference between the direct current reference and the direct current calculated by the direct current calculator 42 is input to the direct current controller 43 by the calculator 46. Further, this difference is corrected by adding the output from the DC voltage average value control unit 41.

  A plurality of DC voltage individual control units 44, computing units 47, and computing units 48 are provided corresponding to the respective converters 30. In this example, two DC voltage individual control units 44, two computing units 47, and two computing units 48 are provided.

  The calculator 48 calculates the difference between the DC voltage detection value and the DC voltage reference value of each of the two converters 30 constituting the first leg LG1. The DC voltage individual control unit 44 calculates a correction value of the voltage reference VR for each converter 30 according to the difference.

  For example, when the voltage VC of the converter 30 is lower than the DC voltage reference value, the DC voltage component of the voltage reference VR is corrected to the positive side. When the voltage VC of the converter 30 is higher than the DC voltage reference value, the DC voltage component of the voltage reference VR is corrected to the negative side. Thereby, the voltage VC of the converter 30 can be made substantially constant. Note that the correction value of the voltage reference VR is not limited to the DC voltage component of the voltage reference VR. The correction value of the voltage reference VR may be, for example, the phase or amplitude of the voltage reference VR, or a combination thereof.

  Each of the calculators 47 receives the current voltage reference VR of each converter 30 and the output of the DC current control unit 43 and the output of the DC voltage individual control unit 44 as correction values thereof. Each computing unit 47 corrects the voltage reference VR of each converter 30 by adding a correction value to the current voltage reference VR, for example. The control circuit 14 applies the corrected voltage reference VR as a new voltage reference VR of the converter 30.

  As described above, the control circuit 14 not only adjusts the voltage VC of each converter 30 to the target DC voltage reference value, but also considers the voltage balance in each arm and between arms, and the voltage reference VR of each converter 30. Correct. The control circuit 14 controls on / off of the switching elements 31 and 32 based on the corrected voltage reference VR. Thereby, for example, each leg current becomes substantially constant, and the voltage VC of each converter 30 becomes substantially constant.

Next, a test method for the converter 30 using the test apparatus 10 will be described.
FIG. 5 is a flowchart schematically showing the procedure of the testing method for the converter.
As shown in FIG. 5, when testing the converter 30 with the test apparatus 10, first, the plurality of converters 30 to be tested are connected to the arm portions 21 a to 21 d, and the plurality of converters 30 are connected. Bridge connection is performed by the bridge circuit 12 (step S110). For example, a total of four converters 30 are bridge-connected to each of the arm portions 21a to 21d.

  After the plurality of converters 30 are bridge-connected, the control circuit 14 is operated. The control circuit 14 controls the switching of the switching elements 31 and 32, converts the DC power of the DC power source 4 into AC power, and supplies the AC power 22 (step S120).

  At this time, the control circuit 14 causes the AC load voltage applied to the AC load 22 to have a predetermined amplitude and phase with respect to the first AC output voltage (the voltage at the first connection point CP1) of the first leg LG1. Further, the amplitude and phase of the AC voltage component of each voltage reference VR of the plurality of converters 30 are adjusted. For example, the control circuit 14 adjusts the amplitude and phase of the AC voltage component of the voltage reference VR of each converter 30 so that the phase of the AC load voltage is 90 ° ahead of the first AC output voltage. . Thereby, the duty of actual power factor 1 operation can be given to each converter 30 of the 1st leg LG1. Further, by adjusting the voltage reference VR, it is possible to give a duty equivalent to that of an actual operation with an arbitrary power factor. Furthermore, the same duty as regenerative operation can be given.

  After the control circuit 14 starts supplying power to the AC load 22, the control circuit 14 detects the voltage VC of each converter 30 based on the detection result of each voltage detection unit 24 and detects each current. Based on the detection result of the unit 25, the arm current of each of the arm units 21a to 21d is detected.

  The control circuit 14 corrects the voltage reference VR of each converter 30 as described above based on each detected voltage VC and each arm current (step S130). For example, the control circuit 14 corrects the DC voltage component of the voltage reference VR of each converter 30.

  The control circuit 14 controls the switching of the switching elements 31 and 32 based on the corrected voltage reference VR. For example, the control circuit 14 continuously corrects each voltage reference VR according to detection of each voltage VC and each arm current. For example, each voltage VC and each arm current may be periodically detected and each voltage reference VR may be periodically corrected.

  In the test apparatus 10 according to the present embodiment, the voltage VC of each converter 30 and the arm current of each arm unit 21a to 21d can be detected, and the voltage VC can be controlled based on each voltage and each current. Since the magnitude is equivalent to the actual operating state, and the current flowing through each converter 30 is equivalent to the actual operating state, the voltage / current duties of the switching elements 31 and 32 are equivalent to the actual operating state. Can be. Thereby, the function / performance such as energization and switching of each switching element 31, 31 can be tested in a situation equivalent to the actual use situation.

  Moreover, in the test apparatus 10, it is not necessary to perform a test with the same configuration as the usage situation, and it is possible to suppress an increase in the size of the test facility and an increase in contract power. As described above, in the test apparatus 10, the voltage / current duty equivalent to the actual operation state can be given to each converter 30 of the MMC with a simple circuit.

FIG. 6 is a block diagram schematically illustrating another bridge circuit according to the embodiment.
As illustrated in FIG. 6, in the bridge circuit 112, a plurality of converters 30 connected in series are connected to each of the arm portions 21a to 21d. In other words, in the bridge circuit 112, the plurality of converters 30 are cascade-connected in each of the arm portions 21a to 21d.

  In the bridge circuit 112, a plurality of pairs of connection terminals t1 and t2 are provided in each of the arm portions 21a to 21d. The terminals 30a and 30b of each converter 30 are connected to the connection terminals t1 and t2. Thereby, each converter 30 is connected in series in the state connected to each of each arm part 21a-21d.

  Without being limited thereto, for example, a pair of connection terminals t1 and t2 is provided for each of the arm portions 21a to 21d, and the terminal 30a of the first converter 30 of the plurality of converters 30 connected in series in advance is provided. The terminal 30b of the last converter 30 may be connected to the connection terminal t2 by connecting to the connection terminal t1.

  Thus, you may connect the some converter 30 to each arm part 21a-21d. The number of converters 30 connected to each arm part 21a-21d may be arbitrary. For example, the number of converters 30 may be set as appropriate according to, for example, the size of the building on which the test is performed or contract power.

  Note that the number of converters 30 to be connected may be the same or different in each of the arm portions 21a to 21d. When the number of converters 30 to be connected is different in each arm portion 21a to 21d, the voltage and current set in each arm portion 21a to 21d are adjusted, and substantially the same voltage and current are applied to each of the converters 30. May be input. However, considering the balance between voltage and current, the number of converters 30 to be connected is preferably the same in each of the arm portions 21a to 21d.

FIG. 7 is a block diagram schematically illustrating another bridge circuit according to the embodiment.
As illustrated in FIG. 7, the bridge circuit 212 further includes a third leg LG3. The third leg LG3 includes a fifth arm portion 21e and a sixth arm portion 21f. The fifth arm portion 21e is electrically connected to the input terminal 20a. The sixth arm portion 21f is electrically connected between the fifth arm portion 21e and the input terminal 20b. The fifth arm portion 21e and the sixth arm portion 21f are connected in parallel to the first arm portion 21a and the second arm portion 21b, and in parallel to the third arm portion 21c and the fourth arm portion 21d. Connected. That is, the bridge circuit 212 is a three-leg, six-arm three-phase bridge. Thus, the bridge circuit of the test apparatus 10 may be a three-phase bridge.

  The converter 30 is connected to each of the 5th arm part 21e and the 6th arm part 21f similarly to each arm part 21a-21d. Since the functions and configurations of the fifth arm portion 21e and the sixth arm portion 21f are the same as those of the arm portions 21a to 21d, detailed description thereof is omitted. Similarly, the voltage detection unit 24 and the current detection unit 25 are also provided in the fifth arm unit 21e and the sixth arm unit 21f.

  In the bridge circuit 212, each leg LG1 between the first leg LG1 and the second leg LG2, between the second leg LG2 and the third leg LG3, and between the third leg LG3 and the first leg LG1. An AC load 22 is provided between the LGs 3.

  When the bridge circuit 212 is used, the control circuit 14, for example, applies an AC load applied to the AC load 22 between the first leg LG1 and the second leg LG2 with respect to the first AC output voltage of the first leg LG1. The amplitude and phase of the AC voltage component of the voltage reference VR of each converter 30 of the first leg LG1 and the second leg LG2 are adjusted so that the voltage has a predetermined amplitude and phase. At this time, for example, the control circuit 14 stops each converter 30 of the third leg LG3. Alternatively, the control circuit 14, for example, in the same way as each converter 30 of the second leg LG2, with respect to the first AC output voltage of the first leg LG1, the AC between the first leg LG1 and the third leg LG3. The amplitude and phase of the AC voltage component of the voltage reference VR of each converter 30 of the third leg LG3 are adjusted so that the AC load voltage applied to the load 22 has a predetermined amplitude and phase. Thereby, even in the case of the bridge circuit 212 of a three-phase bridge, the test of each converter 30 can be performed similarly to the above.

FIG. 8 is a block diagram schematically illustrating another converter according to the embodiment.
As illustrated in FIG. 8, the converter 130 further includes a third switching element 133 and a fourth switching element 134. The third switching element 133 and the fourth switching element 134 are, for example, self-extinguishing elements such as IGBTs, like the first switching element 31 and the second switching element 32.

  The pair of main terminals of the fourth switching element 134 is connected in series to the pair of main terminals of the third switching element 133. The third switching element 133 and the fourth switching element 134 are connected in parallel to the first switching element 31 and the second switching element 32. The charge storage element 33 is connected in parallel to the first switching element 31 and the second switching element 32 and is connected in parallel to the third switching element 133 and the fourth switching element 134. A diode 135 is connected to the third switching element 133 in antiparallel with the pair of main terminals. A diode 136 is connected to the fourth switching element 134 in antiparallel with the pair of main terminals.

  The converter 130 includes a pair of terminals 130a and 130b. The terminal 130 a is connected between the first switching element 31 and the second switching element 32. The terminal 130b is connected between the third switching element 133 and the fourth switching element 134. The converter 130 is connected to the connection terminals t1 and t2 of the arm portions via the terminals 130a and 130b. That is, in this example, the converter 130 is a full bridge circuit. Thus, the converter 130 may be a full bridge circuit.

  In the converter 130, the first switching element 31 and the second switching element 32 are alternately turned on / off, and the third switching element 133 and the fourth switching element 134 are alternately turned on / off. For example, when the voltage reference VR is equal to or higher than the carrier wave CW, the control circuit 14 turns on the first switching element 31, turns off the second switching element 32, turns off the third switching element 133, and turns on the fourth switching element 134. turn on. For example, when the voltage reference VR is less than the carrier wave CW, the control circuit 14 turns off the first switching element 31, turns on the second switching element 32, turns on the third switching element 133, and turns on the fourth switching element 134. Turn off. Thereby, the test can be performed in the converter 130 as in the case of the converter 30.

  When the converter 30 is a bidirectional chopper, as shown in FIG. 2, the carrier wave CW and the voltage reference VR are a triangular wave and a sine wave that vary in the range of 0 to 1. On the other hand, when the converter 30 is a full bridge circuit, the carrier wave CW and the voltage reference VR become a triangular wave and a sine wave that change in the range of −1 to 1.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 4 ... DC power supply, 10 ... Test apparatus, 12, 112, 212 ... Bridge circuit, 14 ... Control circuit, 20a, 20b ... Input terminal, 21a-21f ... Arm part, 22 ... AC load, 23 ... DC reactor, 24 ... Voltage detector, 25 ... Current detector, 30, 130 ... Converter, 31 ... First switching element, 32 ... Second switching element, 33 ... Charge storage element, 34, 35, 135, 136 ... Diode, 40 ... Average Value calculation unit 41... DC voltage average value control unit 42... DC current calculation unit 43 43 DC current control unit 44. DC voltage individual control unit 45 to 48 ... computing unit 133 ... third switching element 134 ... Fourth switching element

Claims (8)

A connection step of bridge-connecting a plurality of converters to be tested by a bridge circuit,
Each of the plurality of transducers is
A first switching element;
A second switching element connected in series to the first switching element;
A charge storage element connected in parallel to the first switching element and the second switching element;
Including
The bridge circuit is
A pair of input terminals electrically connected to the DC power source;
A first arm portion electrically connected to one of the pair of input terminals;
A second arm portion electrically connected between the first arm portion and the other of the pair of input terminals;
A third arm portion electrically connected to the one of the pair of input terminals;
A fourth arm portion electrically connected between the third arm portion and the other of the pair of input terminals;
One end electrically connected to the first connection point of the first arm part and the second arm part, and one end electrically connected to the second connection point of the third arm part and the fourth arm part. An AC load including the other end,
Including
A connecting step of connecting at least one of the plurality of converters to each of the first arm part to the fourth arm part;
A sinusoidal voltage reference is set for each of the plurality of converters, and the first switching element and the second switching element are set so that the voltages at the first connection point and the second connection point coincide with the respective voltage references. A step of applying a voltage to the AC load by controlling the switching of the AC voltage component, wherein the amplitude and phase of the AC voltage component in each of the voltage references of the plurality of converters is the first connection point. A supply step of adjusting the difference of the AC voltage at the second connection point with respect to the AC voltage to a predetermined amplitude and phase;
Test method for transducers with   The testing method for a converter according to claim 1, wherein the supplying step controls switching of the first switching element and the second switching element by matching the voltage reference with a carrier wave.   While detecting the voltage of the charge storage element of each of the plurality of converters, detecting the current flowing through each of the first arm part to the fourth arm part, and based on the detected voltages and currents, The converter testing method according to claim 1, further comprising a correction step of correcting the voltage reference of each of the plurality of converters.   The converter testing method according to claim 3, wherein in the correcting step, the voltage reference of each of the plurality of converters is corrected so that the voltage of the charge storage element of each of the plurality of converters is constant. . The bridge circuit is
A plurality of voltage detectors provided corresponding to each of the plurality of converters and detecting the voltage of the charge storage element of each of the plurality of converters;
A plurality of current detectors provided in each of the first arm part to the fourth arm part and detecting the current flowing in each of the first arm part to the fourth arm part;
Further including
5. The converter testing method according to claim 3, wherein the correcting step detects each voltage and each current based on a detection result of each of the plurality of voltage detection units and the plurality of current detection units. .   Each of the first arm part to the fourth arm part includes a pair of connection terminals connected to the converter, and a DC reactor connected in series to the converter connected to the pair of connection terminals. The test method of the converter as described in any one of Claims 1-5 containing these.   The converter test method according to claim 1, wherein a plurality of the converters connected in series are connected to each of the first arm part to the fourth arm part. A bridge circuit that bridges a plurality of converters to be tested,
Each of the plurality of transducers is
A first switching element;
A second switching element connected in series to the first switching element;
A charge storage element connected in parallel to the first switching element and the second switching element;
Including
The bridge circuit is
A pair of input terminals electrically connected to the DC power source;
A first arm portion electrically connected to one of the pair of input terminals;
A second arm portion electrically connected between the first arm portion and the other of the pair of input terminals;
A third arm portion electrically connected to the one of the pair of input terminals;
A fourth arm portion electrically connected between the third arm portion and the other of the pair of input terminals;
One end electrically connected to the first connection point of the first arm part and the second arm part, and one end electrically connected to the second connection point of the third arm part and the fourth arm part. An AC load including the other end,
Including
Each of the first arm part to the fourth arm part is connected to at least one of the plurality of converters, and a bridge circuit;
A sinusoidal voltage reference is set for each of the plurality of converters, and the first switching element and the second switching element are set so that the voltages at the first connection point and the second connection point coincide with the respective voltage references. A control circuit for applying a voltage to the AC load by controlling the switching of
With
The control circuit has a predetermined amplitude and phase of an AC voltage component in the voltage reference of each of the plurality of converters, and a difference between an AC voltage at the second connection point and an AC voltage at the first connection point is a predetermined value. A test device that adjusts the amplitude and phase.

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