JPWO2019155522A1 - Power converter - Google Patents

Abstract

The power converter according to the embodiment has a plurality of cells connected in series to each other. Each cell has a capacitor, a semiconductor switch, a first power supply circuit, a discharge circuit, a discharge circuit driving unit, and a second power supply circuit. The semiconductor switch performs a switching operation for controlling charging and discharging of the capacitor. The first power supply circuit supplies power for driving the semiconductor switch to the semiconductor switch by using power stored in the capacitor. The discharging circuit discharges the capacitor. The discharge circuit driving section drives the discharge circuit. The second power supply circuit supplies power for driving the discharge circuit driving unit using the power stored in the capacitor. The lower limit voltage at which the second power supply circuit can operate is lower than the lower limit voltage at which the first power supply circuit can operate.

Description

  Embodiments of the present invention relate to a power converter.

  Outputs a voltage higher than the withstand voltage of the switching element by connecting a plurality of self-extinguishing type switching elements such as IGBTs (Insulated Gate Bipolar Transistors) and cells as unit converters with capacitors as energy storage elements in series. Self-commutated power converters are known. This type of power converter is called an MMC (Modular Multilevel Converter) or the like.

  Here, when an operator approaches the power converter for maintenance or inspection after an accident, it is necessary to discharge the charge stored in the capacitor for safety. A power supply circuit for driving a switching element using a cell capacitor as a power source always consumes power even when switching is stopped. In addition, when the power charged in the capacitor is consumed and the voltage output by the capacitor becomes lower than the operating voltage of the power supply circuit, the power supply circuit stops, and the charge stored in the capacitor of the cell can be discharged. Disappears. For this reason, it may take a long time to wait for self-discharge of the capacitor, and it may be difficult to work quickly.

JP-A-2006-208743

Hagiwara Makoto and Akagi Yasufumi, "PWM Control Method and Operation Verification of Modular Multilevel Converter (MMC)", IEEJ Transactions D, Industrial Applications Division, Vol. 9570965 (2008-7)

  The problem to be solved by the present invention is to provide a power conversion device that can reduce the time for discharging the charge stored in a capacitor included in a cell.

  The power converter of the embodiment has a plurality of cells connected in series to each other. Each cell has a capacitor, a semiconductor switch, a first power supply circuit, a discharge circuit, a discharge circuit driving unit, and a second power supply circuit. The semiconductor switch performs a switching operation for controlling charging and discharging of the capacitor. The first power supply circuit uses the power stored in the capacitor to supply power for driving the semiconductor switch to the semiconductor switch. The discharging circuit discharges the capacitor. The discharge circuit driving section drives the discharge circuit. The second power supply circuit supplies electric power for driving the discharge circuit driving unit using the electric power stored in the capacitor. The lower limit voltage at which the second power supply circuit can operate is lower than the lower limit voltage at which the first power supply circuit can operate.

FIG. 1 is a configuration diagram illustrating an overall configuration of a power conversion device. FIG. 3 is a diagram showing a configuration of a cell. The figure which shows the circuit structure of a 2nd feed circuit and a discharge circuit. FIG. 4 is a diagram illustrating a change in the voltage of a capacitor and the timing at which a discharge circuit operates. FIG. 3 is a diagram illustrating a circuit configuration of a discharge circuit. The figure which shows the circuit structure of a 2nd electric power feeding circuit and a discharge circuit drive part. The figure which shows the circuit structure of a 2nd feed circuit. The figure which shows the other example of the circuit structure of a discharge circuit.

  Hereinafter, a power converter according to an embodiment will be described with reference to the drawings. In the following description, components having the same or similar functions are denoted by the same reference numerals. In addition, duplicate descriptions of those configurations may be omitted.

(First embodiment)
With reference to FIG. 1, a power conversion device according to a first embodiment will be described. FIG. 1 is a configuration diagram illustrating the overall configuration of the power conversion device 10.

  The power converter 10 includes a central control unit 11, a plurality of positive arms 12, a plurality of negative arms 13, a transformer TR, and a plurality of buffer reactors L. The power converter 10 is, for example, an MMC. The power converter 10 converts AC power supplied to the power converter 10 via the transformer TR into DC power, and converts DC power supplied to the power converter 10 into AC power via the transformer TR. I do. In the following description, a case where power conversion device 10 converts AC power supplied to power conversion device 10 via transformer TR to DC power will be described.

  The central control unit 11 controls a plurality of cells included in the positive arm 12 and the negative arm 13, respectively. The central control unit 11 and a plurality of cells included in the positive arm 12 and the negative arm 13 are connected by, for example, a daisy chain communication network.

[Overall Configuration of Power Converter 10]
As shown in FIG.
The transformer TR is supplied with three-phase AC power from an AC power source. The transformer TR includes a set of a secondary winding and a primary winding for three phases. The three phases are, for example, an AC R phase, an AC S phase, and an AC T phase. To the secondary winding side of the transformer TR, AC R-phase AC power, AC S-phase AC power, and AC T-phase AC power are supplied, respectively. In the following description and drawings, the components of the R phase are denoted by “R”, the S phase is denoted by “S”, and the T phase is denoted by “T”.

  In the positive arm 12, a plurality of cells 100 are connected in series. In the negative arm 13, a plurality of cells 100 are connected in series. The positive arm 12 includes a positive arm 12R, a positive arm 12S, and a positive arm 12T. Further, the negative arm 13 includes a negative arm 13R, a negative arm 13S, and a negative arm 13T.

  Each of the arms included in the positive side arm 12 and the negative side arm 13 is configured by connecting N cells (N ≧ 2) in series with each other. Output any voltage. The stepwise output of the AC voltage is performed by shifting the timing of the switching operation of a switching element (not shown) included in each cell 100. Details of the configuration of the cell 100 will be described later.

  The plurality of buffer reactors L (buffer reactors L1 to L6 shown in the drawing) suppress short-circuit current flowing between three phases each including the positive arm 12, the buffer reactor L, and the negative arm 13 as a single phase. I do.

  In each of the positive side arm 12 and the negative side arm 13, the voltage of each cell 100 is added to determine the output voltage. The output voltage of the positive arm 12 is a positive (DC) voltage with respect to the neutral point. The positive (DC) voltage generated by the positive arm 12 is output to the terminal TCP. The output voltage of the negative arm 13 is a negative (DC) voltage with respect to the neutral point. The negative (DC) voltage generated by the negative arm 13 is output to the terminal TCM. As a result, the power converter 10 outputs DC power from between the terminal TCP and the terminal TCM.

  FIG. 2 is a diagram showing the configuration of the cell 100. The cell 100 is, for example, a half-bridge type chopper cell. Specifically, the cell 100 includes, for example, a cell control unit 101, a discharge circuit 102, a first power supply circuit 103, a voltage detection unit 104, a switching element driving unit 106, a switching element 107a, and a switching element 107b, a capacitor 105, a second power supply circuit 108, and a discharge circuit drive unit 109.

  The central control unit 11 outputs a control signal to the cell control unit 101. The control signal includes a converter stop command ES for stopping the power conversion operation of the cell 100. The cell control unit 101 acquires a control signal from the central control unit 11.

  The cell control unit 101 outputs a discharge circuit operation command RS to the second power supply circuit 108. The discharge circuit operation command RS is a command indicating that the power of the capacitor 105 is discharged to the discharge circuit 102. Further, the cell control unit 101 outputs a timing control signal CS for controlling the switching timing of the switching elements 107a and 107b included in the switching element driving unit 106 to the switching element driving unit 106.

  The switching element driving unit 106 acquires the timing control signal CS from the cell control unit 101. The switching element driving unit 106 drives the switching elements 107a and 107b based on the timing control signal CS obtained from the cell control unit 101.

  As shown in FIG. 2, the switching element 107a and the switching element 107b output a desired DC voltage by being turned on and off by the switching element driving unit 106 using the capacitor 105 as a voltage source.

  The capacitor 105 is connected in parallel to the switching elements 107a and 107b connected in series. As the switching elements 107a and 107b, self-extinguishing elements such as GTO, IGBT, and IEGT can be used. Feedback diodes 12a and 12b are connected in anti-parallel to the switching elements 107a and 107b. The cell 100 outputs the DC voltage stored in the capacitor 105 when the switching element 107a is turned on and the switching element 107b is turned off, and the switching element 107a is turned off. Is zero voltage when is turned on.

  Here, a portion having the same potential as the connection point between the switching element 107a and the switching element 107b is referred to as a terminal CP. A portion having the same potential as the emitter terminal of the switching element 107b and the negative terminal of the capacitor 105 is referred to as a terminal CM. In the cell 100, the terminal CP is connected to the cell 100 on the terminal TCP side of the cell 100, and the terminal CM is connected to the cell 100 on the terminal TCM side of the cell 100. Thereby, the plurality of cells 100 are connected in series. The power conversion device 10 performs power conversion by changing the on / off timing of the switching element 107a and the switching element 107b.

  The first power supply circuit 103 supplies driving power to the switching elements 107a and 107b using the power stored in the capacitor 105. Further, the first power supply circuit 103 supplies the power supplied from the capacitor 105 to the switching element driving unit 106 and the cell control unit 101.

  Voltage detecting section 104 detects a voltage between terminals of capacitor 105. Voltage detecting section 104 outputs the detected value to cell control section 101.

  The second power supply circuit 108 supplies power for driving the discharge circuit driving unit 109 using the power stored in the capacitor 105. When acquiring the discharge circuit operation command RS from the cell control unit 101, the second power supply circuit 108 starts supplying power to the discharge circuit drive unit 109.

  The discharge circuit 102 discharges the capacitor 105. The discharge circuit 102 includes a discharge resistor R1 and a discharge switch SW1. The discharge resistor R1 and the discharge switch SW1 are connected in series between the positive and negative electrodes of the capacitor 105. Note that the discharge switch SW1 is maintained in a cutoff state before the switch control signal SS is supplied from the discharge circuit driving unit 109.

  The discharge circuit driving unit 109 outputs to the discharge switch SW1 a switch control signal SS that is a signal for switching between a conductive state and a cutoff state of the discharge switch SW1 included in the discharge circuit 102. This switch control signal SS is a latch signal. That is, the discharge circuit drive unit 109 continues to output the switch control signal SS to the discharge switch SW1 while the voltage Vs is supplied from the second power supply circuit 108. The voltage Vs is an input voltage at which the discharge circuit drive unit 109 can operate, and is an input voltage at which the discharge circuit drive unit 109 can drive the discharge circuit 102.

[Circuit Configuration of Discharge Circuit 102]
Here, a circuit configuration of the second power supply circuit 108 and the discharge circuit 102 according to the first embodiment will be described with reference to FIG. FIG. 3 is a diagram showing a circuit configuration of the second power supply circuit 108 and the discharge circuit 102.

  In the following description, the voltage stored in the capacitor 105 may be described as a voltage Vc.

  The discharge switch SW1 of the present embodiment is, for example, an electromagnetic switch. When the discharge switch SW1 is turned on, the power stored in the capacitor 105 is consumed by the discharge resistor R1. That is, the discharge circuit 102 discharges the capacitor 105 by turning on the discharge switch SW1.

  The second power supply circuit 108 generates a voltage Vs for driving the discharge circuit driving unit 109. The voltage Vs is a voltage lower than the lower limit of the input voltage required for the first power supply circuit 103 to operate. Specifically, the second power supply circuit 108 includes a power supply switch SW2, a resistor R2 and a resistor R3, a current limiting resistor R4, and a Zener diode D1. The resistance value of the resistor R2 is, for example, larger than the resistance value of the resistor R3. Note that the relationship between the resistance value of the resistor R2 and the resistance value of the resistor R3 is not limited to this. The resistance values of the resistors R2 and R3 may be any resistance values as long as the voltage of the voltage Vc can be reduced to a voltage (for example, about 5 V) that can be input to the discharge circuit driving unit 109. .

  The power supply switch SW2, the resistor R2, and the resistor R3 are connected in series between the positive electrode and the negative electrode of the capacitor 105. The second power supply circuit 108 divides the voltage Vc supplied from the capacitor 105 by using the resistors R2 and R3 to generate a voltage Vs. The voltage Vs is, for example, a voltage of 5 volts.

  The second power supply circuit 108 supplies the generated voltage Vs to the discharge circuit driving unit 109. The discharge circuit driving unit 109 operates with the voltage Vs supplied from the second power supply circuit 108. The current limiting resistor R4 limits the current supplied from the second power supply circuit 108 to the discharge circuit driving unit 109.

  The power supply switch SW2 switches between a cutoff state and a conductive state in response to a discharge circuit operation command RS supplied from the cell control unit 101. The power supply switch SW2 is maintained in the cutoff state until the discharge circuit operation command RS is supplied. The second power supply circuit 108 does not generate the voltage Vs, which is the operating voltage of the discharge circuit driving unit 109, when the power supply switch SW2 is in the cutoff state. The second power supply circuit 108 generates a voltage Vs, which is an operation voltage of the discharge circuit driving unit 109, when the power supply switch SW2 is in a conductive state. The Zener diode D1 is a diode for clamping the voltage Vs.

[Discharge timing of capacitor 105]
Here, the discharge timing of the capacitor 105 will be described with reference to FIG. FIG. 4 is a diagram showing a change in the voltage Vc of the capacitor 105 and a timing at which the discharge circuit 102 operates.

  From time t0 to time t1, the cell 100 is in the operating state. For this reason, the voltage Vc of the capacitor 105 included in the cell 100 is the rated voltage of the capacitor.

  It is assumed that an abnormality (for example, an accident) such as a system accident has occurred at time t1. For example, information indicating the occurrence of an accident is input to the central control unit 11 of the power converter 10 by a monitoring device that monitors the state of the system. Note that, instead of the configuration in which the information indicating the occurrence of the accident is input by the monitoring device, when the user operating the power conversion device 10 detects the accident, the information indicating the occurrence of the accident is transmitted to the central control unit 11. The input may be configured. Further, the configuration may be such that the user inputs the converter stop command ES to the central control unit 11 with the maintenance.

  Central control unit 11 outputs converter stop command ES to a plurality of cells 100 included in power conversion device 10 at time t2 in response to input of converter stop command ES.

  The cell control unit 101 that has received the converter stop command ES stops the power conversion operation at time t3. In some cases, the power system to which the power is supplied cannot consume power due to an abnormality such as an accident, and the power supplied from the DC system may be stored in the capacitor 105. For this reason, in the example of FIG. 4, the voltage Vc of the capacitor 105 between the time t1 and the time t3 has changed to a voltage higher than the rated voltage.

  When the cell control unit 101, the first power supply circuit 103, and the switching element driving unit 106 included in the cell 100 operate, the charge stored in the capacitor 105 is consumed from time t3 to time t4. At time t4, the voltage Vc of the capacitor 105 consumes power up to the threshold voltage Vth.

  When the voltage Vc of the capacitor 105 detected by the voltage detection unit 104 becomes lower than the threshold voltage Vth, the cell control unit 101 outputs a discharge circuit operation command RS to the second power supply circuit 108. When acquiring the discharge circuit operation command RS from the cell control unit 101, the second power supply circuit 108 supplies the voltage Vs to the discharge circuit drive unit 109. Note that the user may perform an operation of detecting the accident and causing the second power supply circuit 108 to output the discharge circuit operation command RS to the cell control unit 101. Further, the user may perform an operation to output the discharge circuit operation command RS to the second power supply circuit 108 to the cell control unit 101 with the maintenance.

  The discharge circuit drive unit 109 supplied with the voltage Vs from the second power supply circuit 108 outputs a switch control signal SS to the discharge switch SW1. The discharge switch SW1, which has obtained the switch control signal SS from the discharge circuit driving unit 109, becomes conductive. As a result, the discharge circuit 102 starts discharging the electric charge of the capacitor 105. That is, the discharge circuit 102 operates when the voltage Vc of the capacitor 105 is lower than the threshold voltage Vth.

  From time t4 to time t5, the cell control unit 101, the switching element driving unit 106, the discharging circuit 102, and the second power supply circuit 108 consume the electric charge stored in the capacitor 105. For this reason, the charge stored in the capacitor 105 is consumed faster than the cell controller 101, the first power supply circuit 103, and the switching element driver 106 only consume the charge stored in the capacitor 105.

  Voltage Vc of capacitor 105 decreases to voltage Vss1 at time t5. The voltage Vss1 is a voltage at which the first power supply circuit 103 can operate, and the minimum voltage at which drive power can be supplied to the switching element driving unit 106 is the first power supply circuit 103. Is a voltage that can be output. Note that the voltage at which the cell control unit 101 and the switching element driving unit 106 can operate may be lower than the voltage Vss1.

  From time t5 to time t6, the second power supply circuit 108, the discharge circuit driving unit 109, and the discharge circuit 102 discharge the capacitor 105.

  Voltage Vc of capacitor 105 decreases to voltage Vss2 at time t6. This voltage Vss2 is a voltage at which the second power supply circuit 108 can operate, and the second power supply circuit 108 outputs a minimum voltage at which the discharge circuit drive unit 109 can operate. Is a possible voltage. The voltage at which the discharge circuit 102 operates is lower than the lower limit voltage of the operation voltage of the first power supply circuit 103. The voltage Vss2 is desirably set to a voltage lower than a voltage at which work can be performed safely (for example, around 40 V). This voltage Vss2 is, for example, a voltage of about 30 volts.

  As described above, the power conversion device 10 according to the first embodiment includes the plurality of cells 100 connected in series with each other. Each of the cells 100 controls the capacitor 105 and the charge and discharge of the capacitor 105. The power for driving the switching elements 107a and 107b is supplied to the switching elements 107a and 107b by using the switching elements 107a and 107b performing the switching operation of FIG. 1, a discharging circuit 102 for discharging the capacitor 105, a discharging circuit driving unit 109 for driving the discharging circuit 102, and a discharging circuit driving unit 109 and a discharging circuit 102 using the electric power stored in the capacitor 105. Supply the power to drive the With the feed circuit 108, the operable lower limit voltage second power supply circuit 108 includes a first power supply circuit 103 is lower than the operable lower limit voltage. Thus, the time for discharging the electric charge stored in the capacitor 105 included in the cell 100 can be reduced.

Thus, when an abnormality such as an accident occurs, the voltage Vc of the capacitor 105 can be reduced to a safe voltage in a shorter time. That is, the power conversion device 10 can reduce the time for discharging the charge stored in the capacitor 105 included in the cell 100.

  In the above description, the case where the cell control unit 101 outputs the discharge circuit operation command RS to the second power supply circuit 108 based on the converter stop command ES output from the central control unit 11 has been described. However, it is not limited to this. The cell control unit 101 outputs the discharge circuit operation command RS when the voltage drop rate of the voltage Vc of the capacitor 105 drops below a predetermined threshold value and the capacitor 105 can determine that the capacitor 105 is discharging. The data may be output to the power supply circuit 108. The voltage drop rate is a ratio (ratio) of the voltage drop amount to time. Thereby, the power conversion device 10 can discharge the charge stored in the capacitor 105 even in a state where the converter stop command ES from the central control unit 11 cannot be obtained, thereby improving safety. it can.

  Further, the cell control unit 101 may output a discharge stop signal, which is a signal for stopping the discharge operation of the discharge circuit 102, to the second power supply circuit 108. Specifically, the second power supply circuit 108 switches the power supply switch SW2 to the cutoff state based on the discharge stop signal acquired from the cell control unit 101. The second power supply circuit 108 in which the power supply switch SW2 is turned off stops supplying the voltage Vs. The power supply switch SW2 is turned off when the supply of the voltage Vs is stopped. As a result, the discharge circuit 102 stops operating.

  As a result, the power conversion device 10 can be used, for example, when the abnormality due to an accident is recovered during the discharging operation of the capacitor 105, when the user performs a stop operation for maintenance or the like, and when the power conversion device 10 is stopped due to the accident. The operation of the cell 100 can be restarted at an early stage.

  Further, the discharge circuit 102 may stop operating at a voltage lower than the voltage at which the second power supply circuit 108 operates. That is, the power conversion device 10 may stop the operation of the discharge circuit 102 even if all the charges of the capacitor 105 are not discharged. As described above, the voltage lower than the voltage at which the second power supply circuit 108 operates is a voltage at which work can be performed safely. Therefore, the worker can work safely even if all the charges of the capacitor 105 are not discharged, and does not have to wait until all the charges of the capacitor 105 have been discharged.

In addition, after the power supply operation of the second power supply circuit 108 included in the cell, the cell 100 outputs a signal indicating the operation state of the discharge circuit 102 to the central control unit 11 that controls the plurality of cells 100. You may.
Thereby, the cell 100 can output the value of the voltage Vc of the capacitor 105 to the central control unit 11 even when the capacitor 105 cannot be discharged due to a failure or the like. The central control unit 11 displays the value of the voltage of the capacitor 105 obtained from the cell 100 on a display unit (not shown). Thereby, the worker who operates the power converter 10 can know the value of the voltage Vc of the capacitor 105 for each cell 100, and can increase the work safety.

  Further, the cell 100 may output to the central control unit 11 information indicating a time change of the voltage Vc of the capacitor 105 included in the cell. In this case, the cell 100 may output the value of the voltage Vc of the capacitor 105 detected by the voltage detection unit 104 to the central control unit 11 via the cell control unit 101. Thereby, the central control unit 11 can collect information indicating a time change of the voltage Vc for each cell 100.

  Further, the central control unit 11 calculates the timing at which the voltage Vc of the capacitor 105 decreases to a voltage at which safe operation is possible, based on the information indicating the time change of the voltage of each cell 100 collected for each cell 100. The central control unit 11 causes a display unit (not shown) to display the timing at which the calculated voltage Vc of the capacitor 105 decreases to a voltage at which safe operation is possible, and the time change of the voltage Vc for each cell 100. Thus, the power conversion device 10 allows the operator to know the discharge status of the capacitor 105.

(Second embodiment)
Next, a discharge circuit 102a according to a second embodiment will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted. FIG. 5 is a diagram illustrating a circuit configuration of the discharge circuit 102b.

  The discharge circuit 102a differs from the first and second embodiments in that a thyristor TH1 is used for a discharge switch SW1, as shown in FIG.

  The thyristor TH1 is maintained in a cutoff state before a discharge circuit operation command RS is input from the cell control unit 101 to the second power supply circuit 108. The switch control signal SS from the discharge circuit driving unit 109 is input to the gate of the thyristor TH1. Once the switch control signal SS is input to the gate, the thyristor TH1 is turned on until the current stops flowing to the thyristor TH1 or a reverse voltage is applied to the thyristor TH1.

(Third embodiment)
Next, a second power supply circuit 108c according to the third embodiment will be described with reference to FIG. The same parts as those in the first embodiment, the second embodiment, and the second embodiment are denoted by the same reference numerals, and detailed description is omitted. FIG. 6 is a diagram illustrating a circuit configuration of the second power supply circuit 108c and the discharge circuit driving unit 109c.

  The second power supply circuit 108c further includes a self-holding switch SW3 and a Zener diode D2. The self-holding switch SW3 is maintained in the cut-off state before the discharge control operation command RS is supplied from the cell control unit 101 to the second power supply circuit 108c. A constant current determined by the sum of the clamp voltage of the Zener diode D2 and the voltage across the resistor R3 (that is, the voltage Vs) and the resistance value of the current limiting resistor R4 flow through the discharge circuit driving unit 109c.

  The discharge circuit driving unit 109c is, for example, a relay coil. When a constant current is applied to the relay coil, the discharge switch SW1 and the self-holding switch SW3 become conductive. When the self-holding switch SW3 is turned on, the state in which the voltage Vc is supplied to the second power supply circuit 108c is maintained.

(Fourth embodiment)
Next, a cell 100d according to the fourth embodiment will be described with reference to FIG. The same parts as those in the first embodiment, the second embodiment, the second embodiment, and the third embodiment are denoted by the same reference numerals, and detailed description is omitted. FIG. 7 is a diagram illustrating a circuit configuration of the second power supply circuit 108d.

  The second power supply circuit 108d further includes a signal processing unit 110 and an OR circuit OR in addition to the configuration of the second power supply circuit 108 described above. The OR circuit OR has two input terminals (hereinafter, a first input terminal and a second input terminal) and one output terminal. A first input terminal of the OR circuit OR is connected to the cell control unit 101. The second input terminal of the OR circuit OR is connected to the signal processing unit 110. The output terminal of the OR circuit OR is connected to a control unit (not shown) that controls opening and closing of the power supply switch SW2.

  As described above, the value of the voltage Vc of the capacitor 105 detected by the voltage detection unit 104 is input to the cell control unit 101. In this case, the cell control unit 101 outputs the discharge circuit operation command RS to the first input terminal of the OR circuit OR. For example, when the voltage drop rate of the voltage Vc of the capacitor 105 drops below a predetermined threshold value and the cell control unit 101 can determine that the capacitor 105 is discharging, the cell control unit 101 logically ORs the discharge circuit operation command RS. Output to circuit OR. The discharge circuit operation command RS is, for example, a high-level signal.

  The signal processing unit 110 is connected to an input terminal of the discharge circuit driving unit 109. The input terminal of the discharge circuit drive unit 109 is a connection point between the current limiting resistor R4, the cathode of the Zener diode D1, and the discharge circuit drive unit 109. When the power supply switch SW2 is turned on by the discharge circuit operation command RS, the voltage Vs is held at a certain value by the Zener diode D1. The signal processing unit 110 supplies the processing signal SPS to the OR circuit OR by applying a certain voltage Vs to the input terminal of the discharge circuit driving unit 109. The signal processing unit 110 is, for example, an A / D converter that converts the voltage Vs into a digital signal. The processing signal SPS is, for example, a high-level signal.

  The OR circuit OR calculates the logical sum of the discharge circuit operation command RS obtained from the cell control unit 101 and the processing signal SPS obtained from the signal processing unit 110. The logical sum circuit OR supplies the calculated logical sum to the power supply switch SW2. The power supply switch SW2 switches between a conductive state and a cutoff state based on the value of the logical sum supplied from the logical sum circuit OR. For example, when the calculation result supplied from the OR circuit OR indicates a positive value (that is, when at least one of the discharge circuit operation command RS and the processing signal SPS is supplied), the power supply switch SW2 is supplied. Becomes conductive. For example, when the calculation result supplied from the OR circuit OR indicates a negative value (that is, when both the discharge circuit operation command RS and the processing signal SPS are not supplied), the power supply switch SW2 is turned off.

  With the above-described configuration, when the cell control unit 101 outputs the discharge circuit operation command RS and the power supply switch SW2 is turned on, the Zener diode D1 is turned on, and the voltage Vs is maintained at a certain voltage. Therefore, the signal processing unit 110 supplies the processing signal SPS to the second input terminal of the OR circuit OR. Accordingly, even when the cell control unit 101 does not continue to output the discharge circuit operation command RS, the power supply switch SW2 performs signal processing until the voltage Vc decreases so that the voltage Vs cannot be kept constant. The conduction state can be maintained by the processing signal SPS supplied from the unit 110. Therefore, in the cell 100d, the change in the increase or decrease in the voltage Vc of the capacitor 105 can be used for switching the power supply switch SW2 by the cell control unit 101.

  In addition, the cell control unit 101 may stop the operation of the discharge circuit 102 when the voltage Vc of the capacitor 105 detected by the voltage detection unit 104 is lower than the voltage at which the second power supply circuit 108d operates. . Specifically, when the voltage Vs of the second power supply circuit 108d is lower than the voltage Vss2 that is the lower limit voltage of the circuit operation voltage of the discharge circuit driving unit 109, the cell control unit 101 It is supplied to the sum circuit OR. The OR circuit OR supplied with the negative signal switches the power supply switch SW2 to the cutoff state. As a result, the second power supply circuit 108d stops supplying power to the discharge circuit driving unit 109. The discharge circuit driving unit 109 to which the supply of power has been stopped stops the supply of the switch control signal SS. The discharge switch SW1 in which the supply of the switch control signal SS from the discharge circuit driving unit 109 is stopped is turned off. The operation of the discharge circuit 102 stops when the discharge switch SW1 is turned off.

  In the above-described configuration of the second power supply circuit 108d, a semiconductor switch Q1 may be used as the discharge switch SW1 included in the discharge circuit 102. FIG. 8 is a diagram illustrating another example of the circuit configuration of the discharge circuit 102.

  In the discharge circuit 102b shown in FIG. 8, a semiconductor switch Q1 is used for the discharge switch SW1. The semiconductor switch Q1 is a self-extinguishing type switching element such as a GTO (Gate Turn-Off Thyristor), an IGBT (Insulated Gate Bipolar Transistor), and an IEGT (Injection Enhanced Gate Transistor). This semiconductor switch Q1 has a large withstand voltage.

  Before the switch control signal SS is output from the discharge circuit driving unit 109, the semiconductor switch Q1 is maintained in the cutoff state. When the switch control signal SS is output from the discharge circuit driving unit 109 to the gate of the semiconductor switch Q1, the semiconductor switch Q1 becomes conductive.

  As described above, in the power conversion device 10 according to the fourth embodiment, in the discharge circuit 102, the voltage Vc of the capacitor 105 detected by the cell control unit 101 is lower than the voltage at which the second power supply circuit 108 operates. If it stops working. Thus, even if the voltage Vc of the capacitor 105 is lower than the lower limit voltage at which the first power supply circuit 103 operates, the cell control unit 101 can stop the operation of the discharge circuit 102. When the abnormality due to an accident or the like is recovered during the discharging operation of the capacitor 105, the operation of the cell 100 can be restarted at an early stage.

  In the above-described first, second, third, and fourth embodiments, the cells of the half-bridge type chopper cell have been described. It may be a configuration.

  According to at least one embodiment described above, the power conversion device includes a plurality of cells 100 connected in series with each other. Each of the cells 100 includes a capacitor 105 and a capacitor for controlling charging and discharging of the capacitor 105. First, power for driving the switching elements 107a and 107b is supplied to the switching elements 107a and 107b by using the switching elements 107a and 107b that perform the switching operation and the power stored in the capacitor 105. , A discharging circuit 102 for discharging the capacitor 105, a discharging circuit driving unit 109 for driving the discharging circuit 102, and a discharging circuit driving unit 109 and a discharging circuit 102 using the power stored in the capacitor 105. And the power to drive And a second power supply circuit 108 for supplying the power. The lower limit voltage at which the second power supply circuit 108 can operate is lower than the lower limit voltage at which the first power supply circuit 103 can operate. The time for discharging the stored charge can be reduced. In addition, the power conversion device can sufficiently discharge the charge stored in the capacitor included in the cell, and can secure the safety of a worker who performs maintenance, inspection after an accident, and the like.

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

  DESCRIPTION OF SYMBOLS 10 ... Power conversion device, 11 ... Central control part, 12 ... Positive side arm, 13 ... Negative side arm, 100, 100d ... Cell, 101 ... Cell control part, 102, 102a, 102b ... Discharge circuit, 103 ... First Power supply circuit, 104: Voltage detector, 105: Capacitor, 106: Switching element driver, 107a, 107b: Switching element, 108: Second power supply circuit, 109: Discharge circuit driver, ES: Converter stop command, RS ... discharge circuit operation command, SS ... switch control signal, SW1 ... discharge switch, SW2 ... power supply switch, SPS ... processing signal, SW3 ... self-holding switch, transformer ... TR

Claims (11)

It comprises a plurality of cells connected in series with each other, each cell comprising:
A capacitor,
A semiconductor switch that performs a switching operation for controlling charging and discharging of the capacitor,
Using a power stored in the capacitor, a first power supply circuit that supplies power for driving the semiconductor switch to the semiconductor switch,
A discharge circuit for discharging the capacitor,
A discharge circuit driving unit that drives the discharge circuit;
Using a power stored in the capacitor, a second power supply circuit that supplies power for driving the discharge circuit driving unit,
With
The lower limit voltage at which the second power supply circuit can operate is lower than the lower limit voltage at which the first power supply circuit can operate,
Power converter. The power conversion device according to claim 1, wherein the cell outputs information indicating a time change of a voltage of the capacitor included in the cell to a central control unit that controls a plurality of the cells. The discharge circuit,
Even if the voltage of the capacitor is lower than the voltage at which the semiconductor switch can operate, the capacitor operates with the power supplied by the second power supply circuit.
The power converter according to claim 1. The discharge circuit,
When the voltage of the capacitor is lower than a predetermined voltage, the capacitor operates with power supplied by the second power supply circuit.
The power converter according to claim 2. The discharge circuit,
If the ratio of the amount by which the voltage of the capacitor has decreased with respect to time exceeds a predetermined ratio, the device operates with power supplied by the second power supply circuit.
The power converter according to claim 2. The discharge circuit,
Operate when an operation of operating the discharge circuit is performed by a user;
The power converter according to claim 1 or 2. The cell, after a power supply operation of a second power supply circuit included in the cell, outputs a signal indicating an operation state of the discharge circuit to the central control unit,
The power converter according to claim 2. A control unit that supplies a discharge stop signal, which is a signal for stopping the discharge circuit, to the discharge circuit,
The discharge circuit stops operation based on a discharge stop signal supplied from the control unit,
The power converter according to claim 1. The discharge circuit stops operating when the voltage of the capacitor is lower than a voltage at which the second power supply circuit operates.
The power converter according to claim 1. The discharge circuit includes a switch and a resistor connected in series with the switch.
The power converter according to claim 1. The switch is one of a semiconductor switch and a mechanical switch,
The power converter according to claim 10.

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