JP4721825B2 - Power converter for superconducting coils - Google Patents

Description

  The present invention relates to a power converter for a superconducting coil that is connected to an AC system and supplies AC power from a DC power source.

  In recent years, a distributed power supply system configured to recirculate and store current in a coil held in a superconducting state and exchange this energy with an AC power supply system via a power converter has been put into practical use. This power conversion device can control the voltage difference and phase difference from the system voltage, and can perform reactive power compensation and load leveling for flicker suppression. In addition, it is possible to maintain the supply of AC power to consumers during an instantaneous power failure due to lightning strikes and the like.

The superconducting coil power conversion device has an excitation (charge) mode for storing energy in the coil, a reflux mode for holding the energy in a stored state, and a discharge mode for extracting the energy from the coil. A power converter for a superconducting coil is configured relatively easily using two sets of positive and negative chopper circuits for the voltage type inverter and coil so that these three types of modes can be selected. Proposals have been made (see, for example, Patent Document 1).
Japanese Patent No. 2543336 (page 1-3, FIG. 1)

According to the technique disclosed in Patent Document 1, a self-excited voltage type converter is used in place of the conventional thyristor converter, so that the rated capacity according to the interchangeable power to the AC system can be obtained regardless of the magnitude of the coil current. The apparatus configuration can be obtained, and furthermore, the coil can be discharged and excited using the same circuit. However, in this method, since the polarity of the coil potential is reversed between charging and discharging , the required withstand voltage of the coil and the power conversion device is about twice that of the DC voltage, and it is difficult to increase the coil capacity. there were. On the other hand, it is conceivable that the discharge circuit and the excitation circuit are configured separately, but not only the external shape of the power conversion device with a separate circuit configuration is increased, but also the charge / discharge capacity to the coil is increased. When using a parallel configuration, there is a problem that an excessive current partially flows.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a power converter for a superconducting coil capable of outputting large power with a relatively simple circuit configuration.

  In order to achieve the above object, a power converter for a superconducting coil according to the present invention includes a positive discharge diode connected to the anode terminal from the positive electrode of the positive superconducting coil, and a coil grounded to the positive superconducting coil. The negative discharge diode connected in series from the negative electrode of the negative superconducting coil connected in series through the point to the anode terminal, and the coil from the middle point to the branch point are wired in common, from the branch point to the positive side and the negative side A series circuit comprising a common wiring means wired so as to branch to each other, and a low voltage excitation voltage output means and a semiconductor switch for the positive chopper connected between the anode end of the positive discharge diode and the positive common wiring And an anode terminal of the negative-side discharge diode and the negative-side common line, and the low-voltage excitation voltage output means and the positive-side chopper semiconductor switch have opposite polarities. A series circuit composed of a semiconductor switch for the side chopper, a positive-side and negative-side smoothing capacitor connected between the cathode ends of the positive-side and negative-side discharge diodes and the positive-side and negative-side common wires, respectively, The positive and negative voltage type inverters for converting the DC voltage applied to the smoothing capacitors on the negative side and negative side to AC voltage, respectively, and the outputs of the positive and negative voltage type inverters are connected to the power supply system. In the excitation mode of the positive and negative superconducting coils, the positive and negative chopper semiconductor switches are turned on in the excitation mode of the positive and negative superconducting coils, and the positive and negative superconductivity are output by the excitation voltage output means. In the reflux mode of the positive and negative superconducting coils, the positive and negative chopper semiconductor switches are turned on and the excitation voltage output means outputs zero. The excitation voltage output means in the discharge mode of the positive side and negative side superconducting coils is caused to return so that the current flowing in the common wiring from the coil middle point to the branch point cancels out on the positive side and the negative side. The positive and negative chopper semiconductor switches are turned on and off as step-up choppers, and power is supplied to the power supply system via the positive and negative voltage type inverters and the grid interconnection transformer. It is characterized by doing so.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the power converter device for superconducting coils which can output large electric power with a comparatively simple circuit structure.

  Embodiments of the present invention will be described below with reference to the drawings.

  Hereinafter, a superconducting coil power converter according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 3. 1 is a circuit configuration diagram of a power converter for a superconducting coil according to Embodiment 1 of the present invention.

  Superconducting coils 1A and 1B are connected in series, and the positive electrode side of superconducting coil 1A is connected to smoothing capacitor 3A via discharge / excitation circuits 2A1 and 2A2. The smoothing capacitor 3A is connected to the DC terminal of the voltage type inverter 4A, and the three-phase AC terminal of the voltage type inverter 4A is connected to the power supply system via the grid interconnection transformer 5. Similarly, the negative electrode side of the superconducting coil 1B is connected to the smoothing capacitor 3B via the discharge / excitation circuits 2B1 and 2B2, and the DC terminal of the voltage type inverter 4B is connected to the smoothing capacitor 3B. The phase AC terminal is connected to the power supply system via the grid interconnection transformer 5.

  The midpoints of the superconducting coils 1A and 1B are grounded via the ground impedance 6 and connected to the negative side of the DC end of the smoothing capacitor 3A and the voltage type inverter 4A and to the positive side of the DC end of the smoothing capacitor 3B and the voltage type inverter 4B. Has been. The wiring of this part forms a common line on the positive side and the negative side, but the wiring is shared from the midpoint of the superconducting coils 1A and 1B to the branch point P, and from the branch point P to the positive side and the negative side. Branch and wire.

  In addition, although the circuit breaker for overcurrent protection, the short circuit for overvoltage protection, etc. are provided in the circumference | surroundings of the superconducting coils 1A and 1B, the illustration is abbreviate | omitted here.

  The discharge / excitation circuit 2A1 and the discharge / excitation circuit 2A2 form a parallel circuit. Similarly, the discharge / excitation circuit 2B1 and the discharge / excitation circuit 2B2 form a parallel circuit. Therefore, the configurations of the discharge / excitation circuit 2A1 and the discharge / excitation circuit 2B1 will be described below.

  The discharge / excitation circuit 2A1 is a balance reactor 21A connected in series to the positive electrode side of the superconducting coil 1A, and connected to the balance reactor 21A in series, and connected to the positive electrode side of the smoothing capacitor 3A in the direction of current flow. A diode 22A, a balance reactor 21A, an excitation circuit 23A connected from the midpoint of the discharge diode 22A toward the common line, and a chopper semiconductor switch 24A connected in series to the excitation circuit 23A. In the above configuration, the balance reactor 21A is provided to maintain a current balance between the discharge / excitation circuit 2A1 and the discharge / excitation circuit 2A2 connected in parallel therewith. Therefore, it is possible to omit this when the discharge / excitation circuit 2A is used alone without parallel connection.

  Similarly, the discharge / excitation circuit 2B1 is also connected from the positive side of the superconducting coil 1A to the negative side of the smoothing capacitor 3B via the balance reactor 21B and the discharge diode 22B, and is common from the middle point of the balance reactor 21B and the discharge diode 22B. An excitation circuit 23B connected toward the line and a chopper semiconductor switch 24B connected in series to the excitation circuit 23B are provided. Here, the chopper semiconductor switch 21A and the chopper semiconductor switch 21B have opposite polarities with respect to the common line. This indicates that when a stack including a chopper semiconductor switch, a discharge diode, and the like is configured, the positive side stack and the negative side stack have different structures with respect to the common line.

  Hereinafter, the internal configuration of the excitation circuit 23A will be described with reference to FIGS. FIG. 2 is a circuit configuration diagram of the excitation circuit 23A.

  A series circuit composed of a reflux diode 231 and a chopper semiconductor switch 24A in the excitation circuit 23A is connected from the midpoint of the balance reactor 21A and the discharge diode 22A in FIG. 1 toward the common line. An excitation voltage is applied to both ends of the reflux diode 231 as follows.

  The alternating current from the excitation power source is stepped down by the excitation transformer 222 and the secondary output is supplied to the diode converter 233. The direct current output of the diode converter 233 is smoothed by the excitation smoothing capacitor 234, and an excitation voltage is applied to both ends of the reflux diode 231 via the excitation semiconductor switch 235. Here, the polarity of the reflux diode 231 is such that the current flows when the chopper semiconductor switch 21A is turned on. Here, this is called the same polarity.

  In the above description, the excitation transformer 222 may be integrated with the excitation transformer of the discharge / excitation circuit used in parallel with the primary winding.

  The operation of the superconducting coil power converter according to the present invention will be described below with reference to FIG.

  FIG. 3A is a diagram for explaining the operation in the excitation (charging) mode. The exciting circuit 23 </ b> A adjusts the illustrated voltage e by the on / off operation of the exciting semiconductor switch 235 and applies the exciting voltage to both ends of the reflux diode 231. At this time, if the chopper semiconductor switch 24A is turned on, current flows through the superconducting coil 1A along the route indicated by the arrow in FIG. 1A, and the superconducting coil 1A is excited. Here, the time required for excitation can be performed using a low-voltage power source because there is no problem even if the time required for excitation is considered to be relatively long even if the influence of multiple lightning or the like is taken into consideration.

  FIG. 3B is an operation explanatory diagram of the reflux mode. In this reflux mode, the current in the superconducting coil 1A flows back through the loop indicated by the arrow in FIG. 3B via the reflux diode 231 and the chopper semiconductor switch 24A. At this time, the exciting semiconductor switch 235 of the exciting circuit is in the off state, and the chopper semiconductor switch 24A is maintained in the on state.

  FIG. 3B is an explanatory diagram of the recirculation mode in the positive-side discharge / excitation circuit 2A1, and the recirculation mode of the negative-side discharge / excitation circuit 2B1 is considered together. As described above, the discharge / excitation circuit 2B1 is configured such that the chopper semiconductor switch 24B has a reverse polarity with respect to the common line. Therefore, the reflux current flowing through the superconducting coil 1B is in the direction opposite to the direction of FIG. This indicates that the currents flowing from the branch point P of the common line shown in FIG. 1 to the midpoint of the superconducting coils 1A and 1B cancel each other and become zero. Therefore, if the branch point P is selected at an appropriate position in the structure, the length of the current path through which a large current flows in the return mode can be minimized.

  FIG. 3C is an operation explanatory diagram of the discharge mode. When the semiconductor switch for excitation 235 is turned off and the chopper semiconductor switch 24A is turned on and off, the voltage across the superconducting coil 1A is boosted to charge the smoothing capacitor 3A. Then, by operating the voltage type inverter 4A, the energy stored in the superconducting coil 1A is regenerated to the power supply system via the voltage type inverter 4A.

  In each of the above operation modes, the superconducting coil 1A, the chopper semiconductor switch 24A excitation, and the excitation semiconductor switch 235 are all high-voltage unipolar, so that the voltage is applied to the power converter for the superconducting coil having a bipolar configuration. The rating can be reduced. In addition, since the positive and negative sides have opposite polarities with respect to the common line, it is not necessary to increase the withstand voltage against ground. Therefore, the superconducting coil power converter of the present invention is suitable for increasing the capacity.

  FIG. 4 shows a circuit configuration diagram of an excitation circuit of the superconducting coil power converter according to the second embodiment of the present invention. The same parts as those in the circuit configuration diagram of the excitation circuit of the superconducting coil power converter according to the first embodiment shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. The second embodiment differs from the first embodiment in that the free wheel diode 231 and the exciting semiconductor switch 235 are omitted, and an AC switch 236 is provided on the input side of the exciting transformer 232.

  The excitation semiconductor switch 235 in FIG. 2 is provided in the low-voltage direct current section, but the circuit voltage is not low, so that the withstand voltage of the circuit is large. On the other hand, if the excitation current is adjusted on the primary side of the excitation transformer 232 and the voltage on the primary side is selected to be a low voltage as in this embodiment, the withstand voltage of the AC switch 236 is reduced. It can be kept low. Further, since the diode converter 233 can also function as a freewheeling diode, the freewheeling diode 231 can be omitted.

  FIG. 5 shows a circuit configuration diagram of an excitation circuit of the power converter for a superconducting coil according to the third embodiment of the present invention. The same parts as those in the circuit configuration diagram of the excitation circuit of the superconducting coil power converter according to the first embodiment shown in FIG. 2 are denoted by the same reference numerals in the third embodiment, and the description thereof is omitted. The third embodiment is different from the first embodiment in that a thyristor converter 237 is provided instead of the diode converter 233, and accordingly, the exciting smoothing capacitor 234 and the exciting semiconductor switch 235 are omitted.

  Thus, by applying the thyristor converter 237 capable of controlling the excitation current in place of the diode converter 233, the excitation smoothing capacitor 234 and the excitation semiconductor switch 235 can be omitted, and the circuit configuration is simplified.

  FIG. 6 shows a circuit configuration diagram of an excitation circuit of a superconducting coil power converter according to a fourth embodiment of the present invention. The same parts as those of the circuit configuration diagram of the excitation circuit of the superconducting coil power converter according to the third embodiment of FIG. 5 are denoted by the same reference numerals in the fourth embodiment, and the description thereof is omitted. The fourth embodiment is different from the third embodiment in that a self-excited current type converter 238 is provided instead of the thyristor converter 237.

  In the case of the excitation circuit using the thyristor converter 237 shown in the third embodiment, it cannot be said that the controllability when the excitation current becomes small is necessarily good. On the other hand, if a self-excited converter is used as in this embodiment, the control characteristics are improved in the necessary excitation current range.

  FIG. 7 shows a circuit configuration diagram of an excitation circuit of a superconducting coil power converter according to a fifth embodiment of the present invention. The same parts as those of the circuit configuration diagram of the excitation circuit of the superconducting coil power converter according to the third embodiment of FIG. 5 are denoted by the same reference numerals in the fifth embodiment, and the description thereof is omitted. The fifth embodiment differs from the third embodiment in that a self-excited voltage type converter 239 and an exciting smoothing capacitor 234 are provided in place of the thyristor converter 237.

  According to this embodiment, not only the control characteristics are improved as in the case of the fourth embodiment, but the self-excited voltage type converter 239 is replaced with a standardized inverter device or the like widely used for a motor drive device or the like. It can be diverted. Further, if the capacity of the flywheel diode used in the self-excited voltage type converter 239 is appropriately selected, the free wheel diode 231 can be omitted.

The circuit block diagram of the power converter device for superconducting coils which concerns on Example 1 of this invention. The circuit block diagram of the excitation circuit of the power converter device for superconducting coils which concerns on Example 1 of this invention. Operation | movement explanatory drawing of the power converter device for superconducting coils which concerns on Example 1 of this invention. The circuit block diagram of the excitation circuit of the power converter device for superconducting coils which concerns on Example 2 of this invention. The circuit block diagram of the excitation circuit of the power converter device for superconducting coils which concerns on Example 3 of this invention. The circuit block diagram of the excitation circuit of the power converter device for superconducting coils which concerns on Example 4 of this invention. The circuit block diagram of the excitation circuit of the power converter device for superconducting coils which concerns on Example 5 of this invention.

Explanation of symbols

1A, 1B Superconducting coil 2A1, 2A2, 2B1, 2B2 Discharge / excitation circuit 3A, 3B Smoothing capacitor 4A, 4B Voltage type inverter 5 System interconnection transformer 6 Ground impedance

21A, 21B Balance reactor 22A, 22B Discharging diode 23A, 23B Excitation circuit 24A, 24B Semiconductor switch for chopper

231 free-wheeling diode 232 exciting transformer 233 diode converter 234 exciting smoothing capacitor 235 exciting semiconductor switch 236 AC semiconductor switch 237 thyristor converter 238 self-excited current type converter 239 self-excited voltage type converter

Claims (7)

A positive-side discharge diode wired from the positive electrode of the positive-side superconducting coil to the anode terminal;
A negative-side discharge diode connected to the anode terminal from the negative electrode of the negative-side superconducting coil connected in series via the positive-side superconducting coil and a grounded coil middle point;
Common wiring means wired in common from the coil middle point to the branch point, and wired so as to branch from the branch point to each of the positive side and the negative side;
A series circuit connected between the anode end of the positive-side discharge diode and the positive-side common wiring, and comprising a low-voltage excitation voltage output means and a positive-side chopper semiconductor switch;
A series circuit composed of a negative chopper semiconductor switch having a polarity opposite to that of the low voltage excitation voltage output means and the positive chopper semiconductor switch, connected between the anode end of the negative discharge diode and the negative common wiring. ,
Smoothing capacitors on the positive and negative sides respectively connected between the cathode ends of the positive and negative discharge diodes and the positive and negative common wires;
A positive-side and negative-side voltage type inverter that converts a DC voltage applied to the positive-side and negative-side smoothing capacitors into an AC voltage, respectively;
A grid interconnection transformer that links the outputs of the positive side and negative side voltage type inverters to a power system;
In the excitation mode of the positive and negative superconducting coils, the positive and negative chopper semiconductor switches are turned on, and the positive and negative superconducting coils are excited by the excitation voltage output means,
In the return mode of the positive and negative superconducting coils, the semiconductor switches for the positive and negative choppers are turned on, the output of the excitation voltage output means is set to zero, and the common from the coil middle point to the branch point Reflux so that the current flowing in the wiring cancels out on the positive and negative sides,
In the discharge mode of the positive and negative superconducting coils, the output of the excitation voltage output means is set to zero, the positive and negative chopper semiconductor switches are turned on and off as boost choppers, and the positive and negative choppers are turned on and off. A power converter for a superconducting coil, wherein power is supplied to a power supply system via a voltage-type inverter and the grid-connected transformer. A balance reactor is provided between the positive and negative superconducting coils and the positive and negative discharge diodes,
2. The superconducting coil power according to claim 1, wherein a plurality of discharge / excitation circuits composed of the balance reactor, the discharge diode, the excitation voltage output means, and the chopper semiconductor switch are connected in parallel. Conversion device. The excitation voltage output means includes
An excitation transformer fed from an excitation AC power supply;
A diode converter that rectifies the output of the excitation transformer;
A smoothing capacitor for smoothing the output of the diode converter;
An excitation semiconductor switch for controlling on / off of the DC output of the smoothing capacitor for excitation;
Connected to an output side of the exciting smoothing capacitor and the exciting semiconductor switch, and comprising a free-wheeling diode having the same polarity as the chopper semiconductor switch,
The power converter for a superconducting coil according to claim 1, wherein both ends of the reflux diode are used as outputs. The excitation voltage output means includes
An excitation transformer fed from an excitation AC power source via an AC semiconductor switch;
A diode converter that rectifies the output of the excitation transformer;
A smoothing capacitor for smoothing the output of the diode converter;
Comprising
2. The superconducting coil power converter according to claim 1, wherein both ends of the exciting smoothing capacitor are output. The excitation voltage output means includes
An excitation transformer fed from an excitation AC power supply;
A thyristor converter for controlling the output of the excitation transformer and outputting a direct current;
A free-wheeling diode connected in parallel to the output side of the thyristor converter and having the same polarity as the semiconductor switch for chopper,
The power converter for a superconducting coil according to claim 1, wherein both ends of the reflux diode are used as outputs. The excitation voltage output means includes
An excitation transformer fed from an excitation AC power supply;
A self-excited current type converter that controls the output of the excitation transformer and outputs a direct current;
A free-wheeling diode connected in parallel to the output side of the self-excited current type converter and having the same polarity as the semiconductor switch for chopper,
The power converter for a superconducting coil according to claim 1, wherein both ends of the reflux diode are used as outputs. The excitation voltage output means includes
An excitation transformer fed from an excitation AC power supply;
A self-excited voltage type converter that outputs direct current by controlling the output of the excitation transformer;
An excitation smoothing capacitor that smoothes the output of the self-excited voltage type converter,
2. The superconducting coil power converter according to claim 1, wherein both ends of the exciting smoothing capacitor are output.

Images