JP2011051558A - Superconductive direct current feeding system and direct current feeding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a superconductive direct current feeding system that suppresses transverse flow between direct current substations while supplying a constant voltage output by controlling an output voltage of each self-excited rectifier, normally operates even when a load is rapidly changed, and safely continues parallel driving operation of the self-excited rectifier even when the communication between the direct current substations is interrupted. <P>SOLUTION: The superconductive direct current feeding system includes: a voltage control loop (a voltage control loop in a converter 21) for basically controlling an output voltage corresponding to a voltage control command value Vr of the self-excited rectifier; a first control loop (high speed control) 30 for controlling to express output voltage characteristics (VI characteristics) corresponding to a load current I; a second control loop (middle speed control) 31 for controlling a constant voltage such that an average output voltage of the self-excited rectifier is a target value; and a third control loop (low speed control) 50 for changing the VI characteristics in the first self-excited rectifier according to a load sharing rate of the self-excited rectifier in other direct current substation and changing the load sharing rate. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a superconducting DC feeding system and a DC feeding method in which a superconducting wire (for example, a superconducting cable) is applied to a DC feeding type feeder.

  FIG. 4 is a schematic diagram of a conventional railway power feeding system (see Non-Patent Document 1 and Non-Patent Document 3). In FIG. 4, 101 is an AC power transmission line, 102 is a DC substation (SS), 103 feeder, 104 is a trolley wire, 105 is an air section, 106 is a return rail, and 107 is an electric vehicle. In the DC substation 102, a rectifier transformer 111, a rectifier (diode rectifier) 112, and a DC high-speed circuit breaker 113 are installed. As shown in this figure, the conventional feeder 103 uses aluminum or copper wire, is installed along the line from the DC substation 102, and is configured to be connected to a trolley wire 104 using copper wire at certain intervals. Has been. Since this railway power feeding system is well known, detailed description thereof will be omitted.

  Further, as the rectifier 112, a self-excited rectifier (for example, a PWM converter) has been used (see Non-Patent Document 2 and Non-Patent Document 3). This self-excited rectifier has many advantages, such as having few harmonics to the AC system, being able to operate at a power factor of 1, and having the functions of a rectifier and a power regenerative inverter. Is expected.

  FIG. 5 is a diagram showing a main circuit configuration of a PWM converter (self-excited rectifier) described in Non-Patent Document 2. The PWM converter shown in FIG. 5 includes a plurality of switching devices in consideration of withstand voltage / current capacity, voltage control performance, power supply (electric power company), harmonics flowing out to the feeder side, ease of manufacture, etc. A voltage-type converter unit (PWM converter) 121A is configured to be multiplexed six times in series or in parallel by a multiple transformer 121.

  As a switching device in the converter unit 121A, an IGBT (Insulated Gate Bipolar Transistor) element is used, and the modulation frequency of each PWM converter is, for example, about 450 Hz. Since the frequency is 2700 Hz (54th order), the harmonics of the 40th order and below that are obliged to be suppressed by the harmonic suppression countermeasure guidelines hardly flow out, and there is an advantage that no equipment such as a filter is required on the AC side. is there. In addition, a reactor L for suppressing the current change rate (di / dt) of the fault current is connected in series on the feeder side so that the DC high-speed circuit breaker can reliably protect against a short-circuit fault directly under the substation. It is connected to the.

  FIG. 6 is a block diagram showing the configuration of the control circuit of converter unit 121A shown in FIG. The control system shown in FIG. 6 simultaneously performs reactive power compensation and DC voltage control on the power receiving side, like a general self-excited rectifier. Although this converter unit has a current control loop in the minor loop and performs voltage control in the outer loop, it has a known configuration, but can be used as a self-excited rectifier in the superconducting DC feeding system of the present invention. Since it is a thing, the structure is demonstrated here.

  In FIG. 6, the AC voltage output from the multiple transformer 201 is converted into a DC voltage by a power conversion unit 202 configured with an IGBT three-phase bridge circuit. The output voltage Vdc of the power conversion unit 202 is detected by a voltage detector (VD) 203, and a DC voltage detection signal having a magnitude proportional to the DC output voltage Vdc is output from the voltage detector (VD) 203 as a feedback signal. Is output as Further, a DC current detector (CT) 204 for detecting a DC output current Idc is provided on the output side of the power conversion unit 202, and is proportional to the DC output current Idc from the DC current detector (CT) 204. A DC current detection signal having a magnitude corresponding to that is output as a feedback signal.

  Further, an AC current detector (CT) 205 for detecting an AC input current Iac is provided on the input side of the multiple transformer 201, and each phase (three phases) is provided from the AC current detector (CT) 205. An AC input current detection signal corresponding to the alternating current input current flowing through is output. In addition, an instrument transformer (PT) 206 for detecting an AC input voltage is connected to the input side of the multiple transformer 201, and each phase (three phases) is connected from the instrument transformer (PT) 206. An AC power supply voltage signal is output. In addition, the three-phase / two-phase converter 211 includes an AC power supply voltage signal for each phase output from the instrument transformer (PT) 206 and an AC input for each phase output from the AC current detector (CT) 205. Based on the current signal, the current of each phase of the three phases is converted into a two-phase signal (DC signal) orthogonal to each other and divided into two-phase (effective current component and reactive current component) signals to be output.

  In the above configuration, the voltage control command value Vr is compared with the feedback signal (DC voltage detection signal) output from the DC voltage detector (VD) 203 by the adder 221, and the comparison result (difference signal) is the voltage regulator. (AVR) 222 input signal. The voltage regulator (AVR) 222 is an amplifier composed of proportional integral (PI) elements and the like. An output signal from the voltage regulator (AVR) 222 is output to the adder 223. On the other hand, the hood forward control unit 212 generates a hood forward signal based on the DC current detection signal output from the DC current detector 204. This hood forward signal and the output signal from the voltage regulator (AVR) 222 are added by an adder 223 to become a current command signal of an effective component current. The hood forward signal is a signal used to speed up the response of the control system, and this hood forward signal system can be omitted.

  The output signal from the adder 223 is output to the adder 224 and compared with the effective component current (feedback signal) output from the three-phase / two-phase converter 211, and the comparison result (difference signal) is the current. Input to the regulator 226. In addition, a reactive power command value signal is input to the adder 225, which compares the reactive component current (feedback signal) from the three-phase / two-phase converter 211 with the comparison result (difference signal). , And input to the current regulator 226. The current regulator 226 is an amplifier composed of, for example, a proportional integration (PI) element.

  In the current regulator 226, a two-phase output voltage command signal (based on the current command signal for the effective component current output from the adder 224 and the current command signal for the reactive component current output from the adder 225 is used. DC signal) is generated and output to the 2-phase / 3-phase converter 227. The two-phase / three-phase converter 227 converts a two-phase voltage command signal (DC signal) into a voltage command signal (AC command signal) for each of the three phases and outputs the voltage command signal. In the PWM control unit 228, the voltage command signal for each phase output from the 2-phase / 3-phase converter 227 is subjected to PWM modulation (for example, PWM modulation by triangular wave comparison or the like) to generate a PWM signal for each phase. Then, a gate signal for driving the IGBT in the power conversion unit 202 is generated.

  With the above configuration, a DC output voltage Vdc corresponding to the voltage control command value Vr is output from the power conversion unit 202. Such a constant voltage output is one of the features of the self-excited rectifier. The output-side capacitor C of the power converter 202 is a smoothing capacitor (for reducing ripple by PWM), and the reactor L is a series reactor for suppressing the rate of change in fault current (di / dt). It is.

  Further, the example of the PWM converter shown in FIG. 6 has a slightly complicated configuration for performing the reactive power control and the feedforward control. However, the configuration can be generally simplified. (For example, see Patent Document 1).

  FIG. 7 is a diagram in which the configuration of the three-phase PWM converter described in FIG. As shown in this figure, a PWM converter (self-excited rectifier) should be configured with a simpler configuration when multiple transformers are not used and reactive power control and feedforward control are not required. Can do. The configuration and operation are well known to those skilled in the art, and a description thereof will be omitted.

  By the way, although studies on power transmission using superconducting wires such as superconducting cables have been actively conducted, application of superconducting wires to DC feeding systems is also being studied in the railway field (for example, patents). Reference 2). In the DC feeding system, the energization current is DC and the voltage is relatively low, such as about 1500 V. Therefore, there is a high possibility that various problems caused by the DC feeding system can be solved when a superconducting wire is used.

  In addition, the use of superconducting wires for feeders reduces the resistance of feeders, reducing power loss and voltage drop in feeders, extending the installation interval of substations, increasing the possibility of consolidation, and improving the regeneration rate. This is thought to lead to advantages such as energy saving, reduced capital investment and reduced maintenance.

  FIG. 8 is a diagram for explaining a superconducting DC feeding system using a superconducting wire. The superconducting DC feeding system shown in FIG. 8 is composed of a positive electric circuit (PF) and a trolley line (T) as a train line facility, a negative electric wire (NF) and a rail (R). Negative electric circuit (return line). Constituent materials are superconductivity for the positive wire (PF), copper for the trolley wire (T), superconductivity for the negative wire (NF), and iron for the rail (R). In the feeder branch part A, a positive electric wire (PF) and a trolley wire (T), and a negative electric wire (NF) and a rail (R) are connected. The DC substation SS line is connected between the positive electric wire (PF) and the negative electric wire (NF), and the electric vehicle 107 is connected between the trolley wire (T) and the rail (R), as in the conventional electric wire system. And constitutes a closed circuit. In other words, the superconducting DC feeder system has a configuration including a positive feeder (PF) and a negative feeder (NF) as feeders.

Japanese Patent Laid-Open No. 10-248260 Japanese Patent No. 4080073

Motonaga et al., “Introduction to Electric Railway Technology”, Ohmsha, 2008, p.118-119 Hase et al., “Study on Voltage Control of PWM Converter for Power Supply Applied to DC Electric Railway Substation”, Institute of Electrical Engineers of Japan, Institute of Electrical Engineers of Japan, Institute of Electrical Engineers of Japan, August 2003, Proceedings (3 ), P.365-368 "Electric Railway Handbook", Corona, 2007, p.495-513

  As shown in FIG. 4, a parallel operation in which a diode rectifier is connected to the same feeder circuit is generally performed conventionally. In this conventional system, the load sharing of the rectifier depends on the voltage drop characteristic of the diode rectifier and the resistance of the feeder circuit. In particular, since fluctuations of several percent (approximately the same as the voltage drop of the rectifier) are allowed between the different substations, the stable operation is performed mainly by the resistance of the feeder circuit. Here, when the feeder is superconducting, the resistance of the feeder circuit is very small. Therefore, the balance between substations (between rectifiers) is lost due to voltage fluctuations on the power company side, and a large cross current flows. For this reason, it is necessary to balance load sharing between geographically separated substations (for example, 5 km to 10 km).

  In order to ensure the balance of the output voltage between the substations, an AC / DC converter (or DC / DC converter) such as a self-excited rectifier (PWM converter) as described in FIGS. Need to use. Such self-excited rectifiers are generally installed in each substation and operated in parallel, but we expect the load sharing power circuit resistance between rectifiers for constant voltage output control. It cannot be applied to the superconducting DC feeding system for the reasons described above. In fields other than railways, load sharing control of an AC / DC converter (or DC / DC converter) is generally performed. However, conventional methods are designed on the assumption that real-time communication of physical quantities is performed between converters. That is, each converter is designed to be instantaneously controlled as a whole. However, in an electric railway environment, the communication environment is generally inferior and slow, and even when communication is disabled, it is necessary to continue operation safely without changing the system of the main circuit. Electric railways also require robust algorithms that can operate normally even under severe conditions such as sudden load changes.

  The present invention has been made in view of such circumstances, and an object of the present invention is to use a superconducting wire as a feeder, operate a self-excited rectifier installed in a plurality of DC substations in parallel, and When supplying DC voltage, by controlling the output voltage of each self-excited rectifier, it is possible to suppress the cross current flowing between each DC substation while performing constant voltage output, and normal operation is possible even under severe conditions such as sudden load changes In addition, even when communication between DC substations becomes impossible, the parallel operation of self-excited rectifiers can be safely continued, that is, the superconducting DC can be operated with a robust algorithm. It is to provide an electric system and a DC feeding method.

  Another object of the present invention is to provide a superconducting DC feeding system and a DC feeding method capable of controlling load sharing in a self-excited rectifier installed in each DC substation to a desired ratio. is there.

  (1) The present invention has been made to solve the above-mentioned problems, and the superconducting DC power feeding system of the present invention includes each self-excited rectifier installed in a plurality of DC substations arranged along the railway line. A superconducting DC feeding system that is connected in common to feeders using superconducting wires and operates the self-excited rectifier in parallel to supply a DC voltage to the feeders, and is a self-excited type installed in each DC substation The rectifier is an outer loop of the voltage control loop in addition to the basic voltage control loop that controls the output voltage according to the signal of the input voltage control command value, and has a predetermined VI characteristic according to the load current. A first control loop for controlling the voltage control command value so as to output an output voltage in accordance with (output voltage-output current characteristics), and an outer loop of the voltage control loop, wherein the first control loop And a second control loop for controlling the voltage control command value so that an average output voltage of the self-excited rectifier becomes a predetermined target voltage. To do.

  (2) Further, the superconducting DC feeding system of the present invention has a control time constant longer than that of the second control loop, and is set to 1 according to the load sharing ratio of the self-excited rectifier of another DC substation. It is further characterized by further comprising a third control loop that changes the VI characteristic in the self-excited rectifier of the DC substation and changes the load sharing ratio of the self-excited rectifier.

  (3) Further, the superconducting DC feeding system of the present invention receives the output voltage and output current data of each self-excited rectifier in each DC substation in the superconducting DC feeding system, and outputs the data Based on the voltage and output current data, the current load sharing ratio in each self-excited rectifier is calculated, and the load sharing ratio in each self-excited rectifier is set to a desired value based on the calculated current load sharing ratio. And a system controller for generating a load sharing control signal to be transmitted to each self-excited rectifier.

  (4) Further, the superconducting DC feeding system according to the present invention is configured such that the voltage control command value input to the voltage control loop is Vr, and the load current detection value of the self-excited rectifier is I. In the control loop 1, the voltage control command value Vr is controlled using parameters Vs and r according to an equation given by Vr = Vs−r × I, and the output voltage of the self-excited rectifier is changed to a load current. Control is performed so as to exhibit a drooping characteristic.

  (5) Further, in the superconducting DC feeding system of the present invention, in the second control loop, in the expression of the voltage control command value Vr, Vr = Vs−r × I, in the first control loop Feedback control is performed on the parameter Vs based on the average output voltage of the self-excited rectifier, and the average output voltage of the self-excited rectifier is controlled to coincide with a predetermined target value.

  (6) Further, in the third control loop, the superconducting DC power feeding system according to the present invention is the same as that in the first control loop in the expression of the voltage control command value Vr, Vr = Vs−r × I. For parameter r, feedback control is performed according to the load sharing rate of the self-excited rectifier of each DC substation, and control is performed so that the load sharing rate of the self-excited rectifier of each DC substation becomes a desired load sharing rate. It is characterized by that.

  (7) Moreover, the superconducting direct current feeding system of the present invention is characterized in that the self-excited rectifier is constituted by a three-phase PWM / AC / DC converter or a PWM / DC / DC converter.

  (8) In addition, the DC feeding method of the present invention is a superconducting DC feeder that feeds a DC voltage to a feeder using a superconducting wire by a self-excited rectifier installed in a plurality of DC substations arranged along the railway line. DC power feeding method in a power system, a voltage control procedure that is a basis for controlling an output voltage according to a signal of a voltage control command value input by a self-excited rectifier installed in each DC substation, A control procedure added to the basic voltage control procedure, wherein the voltage control command value is set so as to output an output voltage according to a predetermined VI characteristic (output voltage-output current characteristic) according to a load current. A first control procedure to be controlled and a control procedure added to the basic voltage control procedure, wherein a control time constant is set longer than the first control procedure, and the output of the self-excited rectifier Voltage is predetermined A second control step of controlling the voltage control command value so that the target voltage, characterized in that is carried out.

  (9) In addition, the DC feeding method of the present invention has a control time constant set longer than that of the second control procedure, and 1 according to the load sharing ratio of the self-excited rectifier of another DC substation. A third control procedure for changing the VI characteristics in the self-excited rectifier of the DC substation and changing the load sharing ratio of the self-excited rectifier of the DC substation is further performed.

(1) In the superconducting DC feeding system of the present invention, when a plurality of self-excited rectifiers are operated in parallel to supply DC voltage to the superconducting feeders, the self-excited rectifier responds to the voltage control command value. In addition to the basic voltage control loop for controlling the output voltage, a first control loop (high-speed control, diode rectifier simulation control) for controlling the output voltage characteristics (VI characteristics) according to the load current, Adds a second control loop (medium speed control, constant voltage control) to control the average output voltage of the self-excited rectifier to a predetermined target value, and configures multiple feedback control consisting of two systems with greatly different time constants To do.
As a result, when a plurality of self-excited rectifiers are operated in parallel and a DC voltage is fed to a superconducting feeder, the output voltage of each self-excited rectifier is controlled to achieve a constant voltage output between DC substations. Therefore, normal operation is possible even under severe conditions such as sudden load changes.

(2) Further, in the superconducting DC feeding system of the present invention, the VI characteristic in the self-excited rectifier of one DC substation is changed according to the load sharing ratio of the self-excited rectifier of another DC substation, A third control loop (low speed control) for changing the load sharing ratio of the self-excited rectifier is further provided.
Thereby, it is possible to control the load sharing in the self-excited rectifier installed in each DC substation so as to have a desired ratio. Even when communication between the DC substations becomes impossible, since the control by the first and second control loops described above continues, the parallel operation of the self-excited rectifier can be safely continued. Therefore, it is possible to realize a superconducting DC feeding system that can be operated with a robust algorithm.

(3) Also, in the superconducting DC feeding system of the present invention, the data of the output voltage and output current of each self-excited rectifier in each DC substation is received, and the current load sharing rate in each self-excited rectifier is based on And a system controller that generates a load sharing ratio adjustment signal in each self-excited rectifier and transmits the adjustment signal to each self-excited rectifier.
Thereby, the output voltage and output current data of the self-excited rectifier in each DC substation is received, and the load sharing in the self-excited rectifier installed in each DC substation is set to a desired ratio based on the received data. Can be controlled.

(4) In the superconducting DC power feeding system of the present invention, in the first control loop (for example, high-speed control controlled with a time constant of 1 second or less), the voltage control command value Vr in the case of the output current I Is set to “V = Vs−r × I” using the parameters Vs and r.
As a result, the voltage drop characteristics of the diode rectifier can be imitated to perform robust control against sudden load changes. In addition, when an imbalance occurs in the load of the self-excited rectifier, feedback (negative feedback) is applied in a direction to restore the balance, and generation of a cross current between the DC substations can be suppressed.

(5) Further, in the superconducting DC feeding system of the present invention, in the second control loop (for example, medium speed control controlled with a time constant of several seconds to several minutes), the average output voltage of the self-excited rectifier ( In order to keep the voltage of the feeder line at a constant value (target value), feedback control is performed on the control parameter Vs in the first control loop (high-speed control).
As a result, the feeding voltage average value can be controlled to be constant.

(6) Further, in the superconducting DC feeding system of the present invention, in the third control loop (for example, low speed control controlled with a time constant of several minutes to several hours), the self-excited rectifier of each DC substation Feedback control is performed on the control parameter r in the first control loop (high-speed control) according to the load sharing ratio.
Thereby, it is possible to control the load sharing in the self-excited rectifier installed in each DC substation so as to have a desired ratio.

  (7) Further, in the superconducting DC feeding system of the present invention, the self-excited rectifier is constituted by a PWM / AC / DC converter (or DC / DC converter). The output voltage can be easily controlled. In addition, a self-excited rectifier can be easily configured by using known techniques and general-purpose components.

It is a figure which shows the structural example of the main circuit of the DC substation with which the superconducting DC feeding system of this invention is applied. It is a figure which shows the structural example of the PWM converter in the superconducting DC feeding system of this invention. FIG. 3 is a diagram for explaining the operation of the PWM converter shown in FIG. 2. It is a figure for demonstrating the conventional DC feeding system. It is a figure which shows the main circuit structure of the PWM converter using a multiple transformer. It is a figure which shows the structure of the PWM converter shown in FIG. It is a figure which shows the structural example of the conventional PWM converter. It is a figure for demonstrating the superconducting DC feeding system using a superconducting wire.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration example of a main circuit of a DC substation to which the superconducting DC feeding system of the present invention is applied. The example shown in FIG. 1 is a diagram showing a configuration example of a DC power feeding system for a railway in which a self-excited rectifier is used for controlling a DC voltage of a feeder circuit and a superconducting wire is introduced into a feeder line.

  In the example shown in FIG. 1, a rectifier transformer 10a, 10b, 10c and a PWM converter (3) are respectively connected to a DC substation (SS1) 2a, a DC substation (SS2) 2b, and a DC substation (SSn) 2c. Phase PWM / AC / DC converters (self-excited rectifiers) 11a, 11b, 11c are installed. The PWM converters 11a, 11b, and 11c are operated in parallel to supply a DC voltage to the feeder (DC bus) 1 using superconducting wires. For example, the feeder 1 corresponds to a DC bus circuit composed of a positive wire (PF) using a superconducting wire shown in FIG. 8 and a negative wire (NF).

  As described above, superconducting wires have very low resistance, and load sharing due to electrical resistance cannot be expected as in the case of conventional feeding systems, so when operating converters at each DC substation in parallel, a cross current flows between the converters. Becomes easier to flow. For this reason, PWM converters (self-excited rectifiers) 11a, 11b, and 11c are used as converters, and the output voltage of each of the PWM converters 11a, 11b, and 11c is adjusted to suppress the cross current between the DC substations. Is configured to do.

  Each of the PWM converters 11a, 11b, and 11c includes a DC current detector (CT) 13a, 13b, and 13c that detects an output current, and a DC voltage detector 14a that detects an output voltage (voltage of the feeder 1). 14b, 14c. The voltage control units 15a, 15b, and 15c are control units that control output voltages of the PWM converters 11a, 11b, and 11c.

  The PWM converters 11a, 11b, and 11c can be configured by using, for example, a multiplex type PWM converter using the multiplex transformer shown in FIG. In addition, as a single PWM converter that is not multiplexed, for example, a single PWM converter shown in FIG. 7 can be used (however, a multiple control loop described later is added). That is, the selection can be made in consideration of the switching frequency, the filter capacity, and the equipment cost.

  In the example shown in FIG. 1, one DC converter 11a, 11b, 11c is installed in each DC substation 2a, 2b, 2c, and each DC substation 2a, 2b, 2c is connected by a communication cable 3. The example in the case of performing a cooperative operation between the PWM converters 11a, 11b, 11c of a plurality of substations is shown. The method of the present invention is not limited to this, and can be applied to a case where a plurality of PWM converters are installed in one DC substation and these are operated in parallel. That is, it can be applied regardless of the physical and electrical separation positions of the self-excited rectifiers. Further, the present invention is applicable not only to the superconducting DC feeding system.

  FIG. 2 is a diagram showing a configuration example of a PWM converter used in one DC substation (one system) of the superconducting DC feeding system in the present embodiment.

  As shown in FIG. 2, the PWM converter used in the superconducting DC feeding system of the present invention is configured to have a triple control loop. That is, in the converter shown in the figure, as its control method, a drooping characteristic control loop 30 that performs high-speed control (droop control, diode simulation) described later, a constant voltage control loop 31 that performs medium-speed control (constant voltage control), and a low speed A multi-feedback composed of three systems having different control time constants of the load sharing control loop 50 for performing control (load sharing control) is used. The control operation is the same for both power running and regeneration.

  In FIG. 2, the uppermost converter section 21 (the part surrounded by a broken line) is composed of an adder 22, a first voltage adjustment section 23, a PWM control section 24, and an IGBT three-phase bridge circuit. The converter part 21 is comprised including the power converter part 25, and this converter part 21 is a part of the basic PWM converter.

  The converter unit 21 is the same component as the PWM converter shown in FIGS. As shown in FIGS. 6 and 7, the converter unit 21 actually includes a rectifier transformer, a phase detection circuit for an AC power source, a current control loop, and the like, and a smoothing circuit on the output side. Although it has a more complicated configuration such as having a capacitor and a reactor (when used), it has a well-known configuration and is therefore simplified for easy viewing of the drawings.

  In the converter unit 21, the input voltage control command value Vr is compared with the feedback signal V1 of the DC output voltage output from the power conversion unit 25 by the adder 22, and the voltage control command value Vr and the feedback signal V1 are compared. A difference signal is output toward the first voltage adjustment unit 23. The first voltage adjusting unit 23 is composed of a proportional integral (PI) element, has a loop gain K1, amplifies the differential signal (Vr−V1) output from the adder 22, and amplifies the amplified signal. A signal is output to the PWM control unit 24. The PWM control unit 24 generates a PWM signal corresponding to the signal output from the first voltage adjustment unit 23 and drives the gate of the IGBT in the power conversion unit 25.

  As described above, the converter unit 21 has a voltage control loop that controls the output voltage to match the input voltage control command value Vr. The voltage control in the converter unit 21 is responsive to changes in the voltage control command value Vr, and is a response time determined by the control time constant of the control element of the first voltage adjustment unit 23 (time constant of the integration element) and the like. Thus, the DC output voltage can be controlled. For example, high-speed control with a control time constant in units of several tens of ms to several hundreds of ms is possible. That is, the output voltage can be controlled at a response speed close to a passive circuit response (meaning to compare with response time by program control).

In FIG. 2, the voltage control command value Vr input to the converter unit 21 is expressed by the following equation by the drooping characteristic control loop (first control loop) 30 during high speed control:
The signal is represented by Vr = Vs−r × I.
Here, Vs is a voltage command signal Vs output from the second voltage adjustment unit 23 on the constant voltage control loop 31 side described later, and the parameter “r” is set in the load sharing control unit 42 also described later. It is a control parameter. The voltage command signal Vs changes in a cycle of several seconds to several minutes as will be described later, and can be regarded as a fixed value (parameter “Vs”) during high-speed control (1 second or less). As will be described later, the parameter “r” also changes with a period of several minutes to several hours or more, and can be regarded as a fixed value during high-speed control (1 second or less).

  As described above, the voltage command signal Vs (which can be regarded as the parameter “Vs” in the high-speed control) is output from the second voltage adjustment unit 33 on the constant voltage control loop 31 side, and the parameter “r” is output from the load sharing control unit 42. By outputting a signal of the product “r × I” with the load current I, a signal obtained by subtracting the signal “r × I” from the voltage command signal Vs by the arithmetic operation of the adder 32, “Vs−r × I "is output. This signal becomes the voltage control command value Vr of the converter unit 21, and the converter unit 21 outputs a DC voltage corresponding to the voltage control command value Vr. For this reason, the output voltage of the converter unit 21 exhibits a drooping characteristic with respect to the load current I. In a normal state, the parameter “r” is set to the same level as the voltage drop rate of the conventional diode rectifier (for example, the output voltage droops by about 5% to 8% at 100% rated current).

  Thus, by providing the drooping characteristic control loop (first control loop) 30 as the outer loop of the voltage control loop of the converter unit 21, the VI characteristic (drooping characteristic) that droops the output voltage according to the load current I is provided. Can be obtained. Thereby, the control which shows the drooping characteristic which simulates a diode rectifier is realizable. This drooping control can be said to correspond to the output voltage characteristics of the generator that is controlled in speed.

  FIG. 3A shows operating characteristics of high-speed control (droop characteristic control loop) in the converter unit 21. As shown in FIG. 3A, in the PWM converter unit 21, on the power running side, as the load current I increases, the output voltage V of the converter unit 21 has a drooping characteristic (VI characteristic) corresponding to the parameter “r”. ). On the regeneration side, the increase / decrease characteristics of the output voltage are reversed. The difference in output voltage between the power running side current “0” and the regeneration side current “0” is to prevent cross current from flowing between the rectifiers when there is no load. This value is about several volts to several tens of volts.

  As described above, the high-speed control is controlled with a control time constant of 1 second or less, and can perform robust control against sudden load changes by imitating the voltage drop characteristics of a proven diode rectifier. it can. The voltage control command value Vr for the output current I is set to the parameter Vs, r (which can be regarded as a parameter during high-speed control), and is “Vr = Vs−r × I”. Since the voltage drooping characteristic is similar to that of the passive converter in this way, feedback (negative feedback) is applied in the direction of restoring the balance when an unbalance occurs in the load of the PWM converter, and the load balance of each rectifier Can be kept autonomous and stable.

In FIG. 2, the converter unit 21 is provided with a medium-speed constant voltage control loop (AVR) 31 as an outer loop of the voltage control loop of the converter unit 12. In this constant voltage control loop 31 (second control loop), as its control element, the DC output voltage V1 of the power converter 25 is sampled at a predetermined cycle (for example, several hundreds ms unit), and the sampled DC output voltage The moving average processing unit 35 that performs the moving average processing (for example, the moving average processing in a cycle of 1 minute), the second voltage adjustment unit 33, and the adder 34 are provided. In this constant voltage control loop 31, a voltage command signal that causes the DC output voltage V1 output from the power conversion unit 25 to correspond to a rated feed voltage (for example, 1500 V) is given to the adder 34 as the voltage command signal Vr ^*. .

In the adder 34, the voltage command signal Vr ^* and the voltage signal Vf (feedback signal) output from the moving average processing unit 35 are compared, and the voltage command signal Vr ^* and the voltage signal output from the moving average processing unit 35 are compared. A difference signal from Vf is output. The difference signal output from the adder 34 is output toward the second voltage adjustment unit 33. The second voltage adjusting unit 33 is composed of a proportional integral (PI) element, has a loop gain K2, amplifies the differential signal output from the adder 34, and the amplified signal is a voltage command signal. Vs is output to the adder 32. That is, in the constant voltage control loop 31 as the medium speed control, feedback control is performed on the voltage command signal Vr ^{* in} order to keep the average voltage of the output voltage (feeding line) of the converter unit 12 at a constant value (target value). And the voltage command signal Vs is changed.

  Then, the voltage command signal Vs is output from the constant voltage control loop 31, and the product of the parameter “r” and the load current I (r × I) is output from the r control unit 51, whereby the adder 32. As a result, the voltage control command value Vr (Vr = Vs−r × I) obtained by subtracting the signal (r × I) from the voltage command signal Vs is output. The converter unit 12 controls the output voltage according to the voltage control command value Vr.

  The operation characteristics in the constant voltage control loop 31 are shown in FIG. As shown in FIG. 3B, for example, on the power running side, the voltage command signal is increased or decreased as the load current I increases. That is, in the above-mentioned expression “Vr = Vs−r × I”, the voltage control command value Vr is changed by changing the voltage command signal Vs, and the average output voltage (voltage of the feeder line) of the converter unit 21 is desired. Control to be the value of.

  In FIG. 3B, when the output voltage is increased (Vs is increased) in the direction of arrow A, the output voltage (the voltage of the feeder) is smaller than a target value (for example, 1500 V). When the output voltage is decreased (Vs is decreased) in the direction of arrow B, the output voltage is larger than the target value.

  Thus, by providing the constant voltage control loop 31 as an outer loop of the voltage control loop of the converter unit 12, the converter unit 12 is simulated as a diode rectifier on a time scale of high-speed control (for example, 1 second or less). With a drooping characteristic, an automatic voltage adjustment function can be provided on a time scale (for example, several minutes) of medium speed control. The medium speed control does not need to be performed at high speed in terms of time, and can be performed by program control using a general-purpose CPU. On the other hand, the voltage control in the converter unit 21 and the above-described high-speed control require high-speed control using a DSP (Digital Signal Processor) or a control microcontroller (for example, a microcontroller equipped with an arithmetic unit). . The medium speed control can be said to correspond to automatic voltage adjustment (AVR) in the control of the generator.

  A load sharing control loop 50 is provided as an outer loop of the converter unit 21. In this load sharing control loop 50 (third control loop), the parameter “r” indicating the drooping characteristic is controlled to adjust the output voltage characteristic (VI characteristic) of the converter unit 21 to control the load sharing rate. . This load sharing control is performed by low speed control (control time constant in units of several minutes to several hours).

  The load sharing control loop 50 includes an r control unit 51 and a system control device 52 as control elements. The r control unit 51 controls the load sharing control rate in the PWM converter unit 21 by changing the parameter “r” indicating the drooping characteristic according to the load sharing control signal r 1 _cont output from the system control device 52. The r control unit 51 outputs a signal (r × I) indicating a drooping characteristic during the high-speed control described above. On the time scale (less than 1 second) in the high-speed control, The parameter “r” does not change and acts as a fixed value.

  In this load sharing control, the system controller 52 sends the output current signals (I1 to In) and the output voltage signals (V1 to Vn) of the PWM converter from the DC substations (SS1 to SSn) using a communication cable or the like. The output power at each DC substation (SS1 to SSn) is calculated, and the load sharing ratio at each DC substation (SS1 to SSn) is compared. Then, load sharing control signals r1_cont to rn_cont are generated and output so that the load sharing ratios at the respective DC substations (SS1 to SSn) become a desired load sharing ratio. In other words, in the load sharing control loop, feedback control is performed on the parameter “r” in order to control the load sharing to a desired ratio in the entire PWM converter in each DC substation (as will be described later). The change of parameter “r” (value update) is performed gradually and gradually). This desired load sharing ratio is determined by a method of evenly distributing according to the supply and demand contract conditions with the electric power company and the capacity of each DC substation (SS1 to SSn).

  In the example illustrated in FIG. 2, the load sharing control signal r <b> 1 </ b> _cont is input from the system control device 52 to the r control unit 51. The r control unit 51 changes the parameter “r” in the above-described expression “Vr = Vs−r × I” according to the load sharing control signal r1_cont and reflects it in the drooping characteristic control loop 30 that is high-speed control. The change (value update) of the parameter “r” in the r control unit 51 is transiently and gently performed. For example, the system controller 52 outputs the load sharing control signal r1_cont via a temporary delay circuit such as a low-pass filter (LPF), so that the change of the parameter “r” changes to the time constant (several seconds or more) of the primary delay circuit. ) To be reflected gradually after a delay. Then, the r control unit 51 generates a droop signal (r × I) and outputs it to the adder 32. The reason why the change in the parameter “r” is made moderate is to prevent a sudden increase in the load on the self-excited rectifier and unnecessary operation of the fault selection relay, and is equivalent to the on-load tap switching of the transformer. . In the adder 32, a difference signal (Vr = Vs−r × I) between the voltage command signal Vs output from the second voltage adjustment unit 33 and the voltage command signal (r × I) output from the r control unit 51. ) As a voltage control command value Vr.

  The operation characteristics of the low speed control in the load sharing control loop 50 are shown in FIG. As shown in FIG. 3C, for example, by changing the parameter “r” (changing the drooping characteristic) on the power running side, the voltage control command value Vr is changed, and the output voltage of the converter unit 21 is set to a desired value. Control to be a value.

  In FIG. 3C, when the output voltage is increased in the direction of arrow A, the droop rate is decreased (parameter “r” is decreased), and the output voltage is increased to increase the load sharing ratio. In the case where the output voltage is decreased in the direction of the arrow B, the droop rate is increased (parameter “r” is increased), and the output voltage is decreased to decrease the load sharing rate.

  As described above, by providing the load sharing control loop 50 for controlling the parameter “r”, the converter unit 12 is simulated as a diode rectifier on the high-speed control time scale (for example, 1 second or less) to have a drooping characteristic. In addition, an automatic voltage adjustment function can be provided on a time scale for medium speed control (for example, several minutes), and load sharing control can be performed on a time scale for low speed control (for example, several hours). This low-speed control does not need to be performed at high speed in time, and can be performed by program control using a general-purpose CPU. The low speed control can be said to correspond to load sharing control of each generator in the power system in the control of the generator.

  The control time constant in the voltage control described above is set to the same value for all self-excited rectifiers in order to coordinate the entire feeding system. Further, a limiter is added to the parameters “Vs” and “r” as necessary. For example, for the parameter “Vs”, this value is limited to a value corresponding to the range of the minimum voltage and the maximum voltage determined by the standard or the like. For example, the drop (voltage drop rate with respect to the rated voltage) is limited to a value in the range of 3% to 10%.

  In the example illustrated in FIG. 2, the system control device 52 is provided in the DC substation (SS1) 2a. However, the system control device 52 can be disposed in any DC substation. Moreover, the system control apparatus 52 can also be installed in places other than DC substations, such as a power command station, for example.

  In addition, since the control method of the present invention does not have an effect of recovering the unbalance of the parameter “Vs” of the self-excited rectifier, the system control is performed to recover the “Vs” unbalance due to a control timing shift or the like. The command value of the parameter “Vs” is transmitted from the device 52 to the all self-excited rectifier at regular intervals (simultaneously with the low speed control). The reflection of the command value is performed gently as in the case of the parameter “r”.

  As described above, in the superconducting DC power feeding system of the present invention, when the PWM converter installed in each DC substation is connected in parallel to the feeder of the superconducting wire, the PWM converter of each DC substation, High-speed control that gives characteristics that simulate the characteristics of diodes (less than 1 second), medium-speed control that performs automatic voltage adjustment (several seconds to several minutes), and low-speed control that performs load sharing control (several minutes to several hours) It is composed of a multiple feedback control system having a triple control loop.

  Of these, communication between the self-excited rectifiers is required only for low-speed control that performs the load sharing control unit, and even if communication between DC substations becomes impossible, the above-described high-speed control, and Autonomous control is possible in the parallel operation state by the medium speed control system.

  Thus, in the superconducting DC power feeding system of the present invention, by controlling the output voltage of the self-excited rectifier installed in each DC substation, the cross current flowing between the DC substations can be generated while performing constant voltage output. In addition to being able to control, normal operation is possible even under severe conditions such as sudden load changes, and even when communication between DC substations becomes impossible, the parallel operation of self-excited rectifiers is safely continued It is possible to realize a superconducting direct current feeding system that can be operated by a robust algorithm.

  In addition, the superconducting DC feeding system of the present invention is not limited to the case of using a superconducting wire, but is effective as a control method when performing parallel operation of self-excited rectifiers in a normal DC feeding system. In addition, even in the current independent operation of the self-excited rectifier, it is an effective control method in the cooperative operation with the diode rectifier of the adjacent substation. In addition, in a superconducting DC feeding system, it is electrically equivalent to the case where the substations are passed by a zero-resistance DC bus, and is an essential technology.

  In the above-described embodiment, an example in which a three-phase PWM converter (three-phase PWM / AC / DC converter) is used as a self-excited rectifier has been described. However, the present invention is not limited to this. For example, a configuration in which a converter having a voltage compensation function is connected in series to a diode rectifier is generally used. Moreover, a DC / DC converter can be used as a self-excited rectifier. In this case, the three-phase alternating current is converted to an intermediate direct current voltage (which may be different from the feeding voltage) by a diode rectifier (three-phase bridge circuit) or the like, and this intermediate direct current voltage is desired by the DC / DC converter. ) And output to the feeder circuit side. Alternatively, a configuration in which a secondary battery or a power storage medium is applied as the intermediate DC voltage source is also used (see Non-Patent Document 3).

  Although the embodiment of the present invention has been described above, in the superconducting DC feeding system shown in FIG. 2, the above self-excited rectifier constitutes a converter unit 21 and a multiple control loop added to the converter unit 21. Corresponds to the portion (except for the system control device 52). The basic voltage control loop described above corresponds to the voltage control loop in the converter unit 21 (the part of the feedback control system including the adder 22 and the first voltage adjustment unit 23). The above-described first control loop corresponds to the drooping characteristic control loop 30 including the adder 32 and the r control unit 51 (in the first control loop, the parameter “r” can be regarded as a fixed value). The above-described second control loop corresponds to the constant voltage control loop 31 including the second voltage adjustment unit 33, the adder 34, and the moving average processing unit 35. The third control loop described above corresponds to the load sharing control loop 50 including the r control unit 51 and the system control device 52.

In the superconducting DC feeding system of the present invention, a self-excited rectifier (a part constituted by the converter unit 21 and a multiple control loop added thereto) provided in each DC substation 2a is input. In addition to the voltage control loop in the converter unit 21 that controls the output voltage according to the signal of the voltage control command value Vr, this is an outer loop of this voltage control loop, and has a predetermined VI characteristic (output voltage) according to the load current. A first control loop (droop characteristic control loop 30) for controlling the voltage control command value Vr so as to output an output voltage in accordance with the output current characteristics), and an outer loop of the voltage control loop, A second control time constant is set longer than that of the first control loop, and the voltage control command value Vr is controlled so that the output voltage of the self-excited rectifier becomes a predetermined target voltage. Configured to have a control loop (constant voltage control loop 31), a.
As a result, when a plurality of self-excited rectifiers are operated in parallel and DC voltage is supplied to the superconducting feeders, by controlling the output voltage of each self-excited rectifier, Therefore, normal operation is possible even under severe conditions such as sudden load changes. Moreover, even when communication between DC substations becomes impossible, the parallel operation of self-excited rectifiers can be continued safely. Therefore, it is possible to realize a superconducting DC feeding system that can be operated with a robust algorithm.

In the superconducting DC feeding system of the present invention, the control time constant is set to be longer than that of the second control loop (constant voltage control loop 31), and according to the load sharing rate of the self-excited rectifier of other DC substations. Thus, the third control loop (load sharing control loop 50) for changing the VI characteristics of the self-excited rectifier of the DC substation 2a and changing the load sharing ratio of the self-excited rectifier is further configured.
Thereby, the load sharing in the self-excited rectifier installed in each DC substation can be controlled to a desired ratio.

  Although the embodiments of the present invention have been described above, the superconducting DC power feeding system of the present invention is not limited to the above illustrated examples, and various modifications are made within the scope not departing from the gist of the present invention. Of course you get.

1 ... feeder (superconducting wire), 2a, 2b, 2c ... DC substation, 3 ... communication cable, 10a, 10b, 10c ... transformer for rectifier, 11a, 11b, 11c ... PWM converter, 12a, 12b, 12c ... power converter, 13a, 13b, 13c ... DC current detector, 14a, 14b, 14c ... DC voltage detector, 15a, 15b, 15c ... Voltage control unit, 21 ... converter unit, 22 ... adder, 23 ... first voltage adjustment unit, 24 ... PWM control unit, 25 ... power conversion unit, 30 ... drooping Characteristic control loop, 31 ... Constant voltage control loop, 32, 34 ... Adder, 33 ... Second voltage adjustment unit, 35 ... Moving average processing unit, 50 ... Load sharing control loop 51 ... r control unit, 52 ... system control device

Claims (9)

Each self-excited rectifier installed in a plurality of DC substations arranged along the railway line is commonly connected to a feeder using a superconducting wire, and the self-excited rectifier is operated in parallel to supply a DC voltage to the feeder A superconducting DC feeding system,
The self-excited rectifier installed in each DC substation is
In addition to the basic voltage control loop that controls the output voltage according to the input voltage control command value signal,
A first control that is an outer loop of the voltage control loop and controls the voltage control command value so as to output an output voltage according to a predetermined VI characteristic (output voltage-output current characteristic) according to a load current. Loop,
An outer loop of the voltage control loop, wherein the control time constant is set longer than that of the first control loop, and the voltage control command is set so that an average output voltage of the self-excited rectifier becomes a predetermined target voltage. A second control loop for controlling the value;
A superconducting DC feeding system characterized by comprising: The control time constant is set to be longer than that of the second control loop, and the VI characteristic in the self-excited rectifier of one DC substation is changed according to the load sharing ratio of the self-excited rectifier of another DC substation, A third control loop for changing the load sharing ratio of the self-excited rectifier,
The superconducting DC feeding system according to claim 1, further comprising: In the superconducting DC feeding system,
Receiving the output voltage and output current data of each self-excited rectifier in each DC substation, and calculating the current load sharing ratio in each self-excited rectifier based on the output voltage and output current data, A system controller for generating a load sharing control signal for controlling the load sharing ratio in each self-excited rectifier to a desired value based on the calculated current load sharing ratio and transmitting the load sharing control signal to each self-excited rectifier; The superconducting DC feeding system according to claim 2. When the voltage control command value input to the voltage control loop is Vr, and the detection value of the load current of the self-excited rectifier is I,
In the first control loop,
Using the parameters Vs and r, the voltage control command value Vr is
Vr = Vs−r × I,
Control according to the formula given in
Control so that the output voltage of the self-excited rectifier exhibits a drooping characteristic with respect to the load current.
The superconducting DC feeding system according to claim 1 or 2, characterized in that In the second control loop, an expression for the voltage control command value Vr,
In Vr = Vs−r × I,
For the parameter Vs in the first control loop, feedback control is performed based on the output voltage of the self-excited rectifier, and the average output voltage of the self-excited rectifier is controlled to coincide with a predetermined target value.
The superconducting DC feeding system according to claim 4. In the third control loop, an expression of the voltage control command value Vr,
In Vr = Vs−r × I,
Feedback control is performed on the parameter r in the first control loop according to the load sharing rate of the self-excited rectifier of each DC substation, and the load sharing rate of the self-excited rectifier of each DC substation is a desired load sharing. Control to rate,
The superconducting DC feeding system according to claim 5. The self-excited rectifier includes a three-phase PWM / AC / DC converter or a PWM / DC / DC converter.
The superconducting DC feeding system according to claim 1. A DC feeding method in a superconducting DC feeding system that feeds a DC voltage to a feeder using a superconducting wire by a self-excited rectifier installed in a plurality of DC substations arranged along the railway line,
By the self-excited rectifier installed in each DC substation,
A basic voltage control procedure for controlling the output voltage in accordance with a signal of a voltage control command value input;
A control procedure added to the basic voltage control procedure, wherein the voltage control command value is set so as to output an output voltage according to a predetermined VI characteristic (output voltage-output current characteristic) according to a load current. A first control procedure to control;
A control procedure added to the basic voltage control procedure, wherein the control time constant is set longer than that of the first control procedure, and the output voltage of the self-excited rectifier becomes a predetermined target voltage. A second control procedure for controlling the voltage control command value;
A direct current feeding method, wherein: The control time constant is set longer than that in the second control procedure, and the VI characteristic in the self-excited rectifier of one DC substation is changed according to the load sharing ratio of the self-excited rectifier of another DC substation. And a third control procedure for changing the load sharing ratio of the self-excited rectifier of the DC substation is
The direct current feeding method according to claim 8, further performed.

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