JPH05300658A - Power transmitting facility and power storing facility used for it - Google Patents

Abstract

PURPOSE:To reduce the size and cost of a power transmitting facility equipped with a power storing facility by interposing a DC circuit between AC systems. CONSTITUTION:A power storing device 33 is incorporated in a DC system 32 connected between two AC systems 31 and 34 and a controller 22 which controls the device 33 to store electric power when the systems 31 and 34 are sound and to send or absorb electric power when an accident occurs in either one of the systems 31 and 34 is provided to the system 32. Since the facility 33 is incorporated in the system 32, no power converter, such as the inverter, etc., is required and the size and cost of a power transmitting facility can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving power supply reliability of power transmission equipment in a power system including a DC power transmission system.

[0002]

2. Description of the Related Art FIG. 2 is a single-line system diagram showing a power transmission facility disclosed in, for example, Japanese Patent Laid-Open No. 4-8130. In this electric power facility, an energy storage device is installed on the AC system side of the AC / DC converter in order to stabilize the power supply of the electric power system including the DC transmission system. In the figure, the AC system 1 includes an AC power source 3, an AC power source impedance 4, an inverter 9,
The DC system 2 is composed of an AC / DC converter 6, a DC reactor 7, a DC line 8 and the like. The alternating-current power of the alternating-current power supply 3 included in the alternating-current system 1 is transmitted through the transformer 5 for the conversion device to the AC / DC converter 6
Is converted into DC power by. This DC power is converted into AC power again via another DC / AC converter via the DC reactor 7 and the DC line 8. In this way, by carrying out power transfer between different AC systems via the DC system, there is no problem of stability or increase in short-circuit capacity, which is the case when simply transmitting power by AC, and economic power operation is possible. And interconnection between different frequency systems has been realized. An inverter 9 capable of outputting an arbitrary waveform is connected to the AC system 1 side of the converter transformer 5 via a reactor 10. The voltage and current of the AC system 1 are detected by the voltage sensor 14 and the current sensor 12, respectively, and input to the control device 11. When an accident occurs in the AC system 1 and the power cannot be sent to the DC system 2, the state is the current sensor.
Immediately detected by 12 and voltage sensor 14, control device
Reference numeral 11 sends a control signal to the inverter 9. In response to this, the inverter 9 replaces the AC power supply 3 and the AC system 1
The electric power is output to and the output current is detected by the current sensor 13, and the AC system 1 is operated to return to the power transmission state before the accident. On the other hand, when the power from the AC system 1 cannot be DC-transmitted due to an accident in the DC system 2, the AC / DC converter 6 is urgently stopped, and the emergency stop signal S is sent to the controller 11. Generally, in such a case,
If the amount of power generation in the AC system 1 is sharply narrowed down, there is a problem that it takes time to return to the normal state again when the AC power supply 3 is a power source of nuclear power generation. Therefore, the control device 11 causes the energy storage device built in the inverter 9 to operate the inverter 9 so as to absorb the amount of active power supplied from the AC system 1 before the stoppage of the AC / DC converter 6. In this way, the inverter 9 always operates so as to maintain the energy balance in the event of either the AC system 1 or the DC system 2 and functions to maintain the stability of the entire power system.

[0003]

In the conventional power transmission equipment as described above, it is necessary to equip the AC system 1 with the inverter 9 for energy storage and transmission, so that an increase in the price and size of the equipment cannot be avoided. There was a problem.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a power transmission facility capable of cost reduction and size reduction.

[0005]

The power transmission equipment according to the present invention comprises a first AC system provided on the power supply side, a second AC system provided on the load side, and the first AC system. A direct current circuit interposed between the second alternating current system and the second alternating current system, and a power storage facility provided in the direct current circuit for selectively storing, absorbing and transmitting electric power are provided. Also,
A first AC-DC converter that receives AC power and outputs DC power, a DC reactor that is connected to the output side of the first AC-DC converter, and a second that receives DC power and outputs AC power. And a DC line connecting the second AC / DC converter and the first AC / DC converter via the DC reactor, and is connected to one end of the DC line to store and absorb electric power. And an electric power storage facility for selectively transmitting the electric power. The power storage facility to be provided in the DC circuit according to the present invention is a self-turn-off type first switching element, and a first rectifying element whose cathode is connected to the cathode of the first switching element. A first chopper, a self-extinguishing second switching element, and a second rectifying element whose anode is connected to the anode of the second switching element, A second chopper connected in parallel with the first chopper, a reactor that connects the cathode of the first switching element and the anode of the second rectifying element, and a current sensor that detects a current flowing through the reactor. , A capacitor connected in parallel to the first chopper and the second chopper, a voltage sensor for detecting a voltage between terminals of the capacitor, an output of the current sensor and an output of the voltage sensor are input. It is, can be configured as and a control device which produces an output for controlling the first switching element and the second switching element. The reactor is preferably a superconducting reactor.

[0006]

The power storage facility according to the present invention stores a predetermined DC power when the whole system is healthy. In the event of an AC system accident, power will be further absorbed or transmitted to restore the state before the accident. When the input to the equipment is normal, the control device in the power storage equipment forms a short-circuit closed circuit that includes a reactor to store the specified energy, and when the input is lost due to an accident, etc. The switching element is controlled to be opened / closed so that the circuit is opened to release energy, and when the load of the equipment suddenly becomes light due to an accident or the like, the short-circuit closed circuit is opened to absorb more energy.

[0007]

1 is a circuit diagram showing an embodiment of the present invention. In the figure, an AC system 31 is composed of an AC power supply 3, an AC power supply impedance 4 and a transformer 5 for a converter. The DC system 32 is composed of an AC / DC converter 6, a DC reactors 7 and 71, a power storage device 33, a DC line 8 and an AC / DC converter 23, which are composed of, for example, a 6-phase Gratz connection. Alternatively, power is directly supplied from the AC / DC converter 6. The control device 22 is connected to the power storage device 33 and the AC / DC converter 6. The power storage device 33 includes two sets of choppers 17a and 17b, a reactor 18 including a superconducting coil, a capacitor 19, a current sensor 20 and a voltage sensor 21, and stores or releases energy as described later. The choppers 17a, 17b, the capacitor 19, and the voltage sensor 21 connected in parallel with each other are applied with a DC voltage output from the AC / DC converter 6 via the DC reactor 7. The chopper 17a connects a cathode of a switching element (for example, a gate turn-off thyristor) 15a of reverse conduction type having an anode on the DC reactor 7 side and a diode 16a having an anode on the ground side to each other. On the other hand, the chopper 17b has a diode 16b having a cathode on the side of the DC reactor 7 and a switching element (similar to the switching element 15a) 15b having a cathode on the ground side as anodes of each other. They are connected in series so that they are connected to each other. The connection point between the switching element 15a and the diode 16a and the connection point between the diode 16b and the switching element 15b are connected via a reactor 18. Therefore, the switching element 15a includes the diode 16b and the switching element
The diode 15a is connected to the diode 16a via the reactor 18 in antiparallel with each other. The current flowing through the reactor 18 is detected by the current sensor 20, and the output of the current sensor 20 is sent to the control device 22. Similarly, the output of the voltage sensor 21 that measures the voltage across the terminals of the capacitor 19 is also controlled by the control device 22.
Have been sent to. On the load side (right side) of the DC line 8, a load-side AC system 34 including an AC / DC converter 23 (DC to AC converter) via a reactor 71 and a transformer 24 connected to the AC side. And are provided.

Next, the operation of the above embodiment will be described. In FIG. 1, when the entire system of the AC system 31 and the DC system 32 is healthy, the positive electrode of the AC / DC converter 6,
That is, the DC voltage V _d is output to the DC reactor 7 side, and the DC current I _d is flowing. DC voltage V _d and DC current
I _d is given to the AC / DC converter 23 and the transformer 24 on the load side (hereinafter referred to as the ri side) via the DC line 8 and the reactor 71, and is converted to AC power again here. In the power storage device 33, the control device 22 controls ON / OFF of the other switching element 15b while keeping one switching element 15a in the ON state. This ON / OFF control is performed by the current sensor 2
The current signal taken into the control unit 22 by 0 is performed so as to follow the predetermined command value set in the control unit 22. For example, as a simple example for convenience of explanation, the switching element 15b is ON / OFF-controlled so that a current equal to the current I _d flowing in the DC reactor 7 flows in the reactor 18.
Next, the switching elements 15a and 15b are held in the ON state and the OFF state, respectively, when the current flowing through the reactor 18 becomes equal to I _d . As a result, the current (I _d ) flowing through the reactor 18 circulates through the short-circuit closed circuit formed by the reactor 18, the diode 16b and the switching element 15a, and a so-called flywheel closed circuit is formed. A signal S indicating the operation or stop state of the AC / DC converter 6 is sent to the control device 22, and the control device 22 receives this signal and outputs the output signal of the current sensor 20 while the AC / DC converter 6 is operating. While the AC / DC converter 6 is stopped, the output signal of the voltage sensor 21 is captured.

Next, the operation of the power storage device 33 when an accident occurs in the AC system 31 on the generator side (hereinafter referred to as the mountain side) and the output power of the AC / DC converter 6 becomes 0, for example, will be described. When the output power of the AC / DC converter 6 becomes 0, the control device detects the occurrence of the mountain side accident due to the change of the signal S, and immediately turns ON / OFF the switching element 15a. As a result, the flywheel closed circuit is opened and closed, and the current flowing through the reactor 18 is changed to the diode.
Electric power is taken out by flowing to the village side through 16a and 16b. This ON / OFF control is performed by the control device 22 so that the inter-terminal voltage of the capacitor 19 detected by the voltage sensor 21 becomes V _d . In addition, the direct current is controlled in the AC / DC converter 23 on the rear side so that it becomes equal to I _d . In this way, the same electric power as before the accident on the mountain side was taken out from the power storage device 33, and the AC system 34 on the village side
Power transmission to. The amount of power that can be transmitted at this time is as follows, for example. Inductor L of reactor 18 is 1000
When the current I flowing in the reactor 18 is 0H and the current I is 5000A, (1/2) L · I ² = 1.25 × 10 ¹¹ [J] of energy is accumulated in the reactor 18. Therefore, this corresponds to an electric energy of, for example, 1000 MW × 125 seconds.

Next, the operation of the power storage device 33 when an accident occurs in the village side AC system 34 and the absorption destination of the output power of the AC / DC converter 6 disappears will be described. When an accident occurs in the ri side AC system 34, the ri side AC / DC converter 23 detects a sharp decrease in the AC output and sends a signal to the control device 22 to notify the decrease in the load. The control device 22 receives this and switches the switching elements 15a and 15b to the capacitor 19
ON / OFF control is performed so that the voltage between the terminals becomes V _d, and the output power of the AC / DC converter 6 on the mountain side is switched to the switching elements 15a and 15b.
To be absorbed by reactor 18 via. In this absorption process, the current flowing in the reactor 18 gradually increases from I _{d due} to the application of the output voltage of the AC / DC converter 6, and the stored energy also increases accordingly.

In the above embodiment, the power storage equipment 33 is provided in the mountain side DC circuit, but the same effect can be obtained by providing it in the village side DC circuit. In the above embodiment, when the system is healthy, as a current loop including the reactor 18,
Reactor 18, diode 16b and switching element 15a
Although the loop is shown by, the current loop formed by the reactor 18, the switching element 15b and the diode 16a,
The same operation can be performed by reversing the ON / OFF control of the switching elements 15a and 15b. Further, in the above embodiment, the explanation has been made assuming that there is a power flow from the AC system 31 to the AC system 34, but conversely, the same operation is performed when there is a power flow from the AC system 34 to the AC system 31. It is possible. Further, in the above-described embodiment, a drastic reduction in the AC output due to the system fault on the ri side was detected by the ri side AC / DC converter 23, and a route for transmitting the detected information to the control device 22 was separately provided. It is also possible to detect by the drastic reduction of the output of 6 and transmit the detection information to the control device 22. Further, in the above embodiment, the AC system is assumed to be a power system and the DC system is assumed to be DC power transmission, but the system is applicable regardless of the magnitude of the power to be handled as long as it is a system for exchanging power between different AC circuits via the DC circuit. It is possible.

[0012]

As described above, according to the present invention, since the power storage facility is provided in the DC circuit interposed between the two AC systems, the power conversion device such as an inverter is not required.
Therefore, it is possible to reduce the price and downsize the power storage facility in the power transmission facility.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

[Fig. 2] Single-line system diagram showing conventional power transmission equipment

[Explanation of symbols]

 6 AC / DC converter 7 DC reactor 8 DC line 15a, 15b Switching element 16a, 16b Diode 17a, 17b Chopper 18 Reactor 19 Capacitor 20 Current sensor 21 Voltage sensor 22 Control device 23 AC / DC converter 31 AC system 32 DC system 34 AC system 71 DC reactor

Claims (4)

[Claims] 1. A first alternating current system provided on the power supply side, a second alternating current system provided on the load side, and a first alternating current system interposed between the first alternating current system and the second alternating current system. A power transmission facility comprising: a DC circuit; and a power storage facility that is provided in the DC circuit and selectively stores, absorbs, and sends out power. 2. A first AC-DC converter that receives AC power and outputs DC power, a DC reactor connected to the output side of the first AC-DC converter, and DC power that receives DC power. Is connected to one end of the DC line, and a second AC-DC converter that outputs the DC line connecting the second AC-DC converter and the first AC-DC converter via the DC reactor. A power transmission facility that includes a power storage facility that selectively stores, absorbs, and transmits power. 3. A power storage facility provided in a DC circuit, comprising a self-extinguishing first switching element and a cathode.
A first chopper having a first rectifying element connected to the cathode of the switching element of, a second switching element of self-extinguishing type, and an anode of the second switching element.
A second rectifier element connected to the anode of the switching element of, and a second chopper connected in parallel with the first chopper, a cathode of the first switching element and the second chopper. A reactor that connects the anode of the rectifying element, a current sensor that detects the current flowing through the reactor, a capacitor that is connected in parallel to the first chopper and the second chopper, and a voltage across the terminals of the capacitor is detected. A voltage sensor, and a controller that receives the output of the current sensor and the output of the voltage sensor and produces an output that controls the first switching element and the second switching element. Electricity storage equipment to do. 4. The power storage facility according to claim 3, wherein the reactor is a superconducting reactor.