High-speed current-limiting breaker, power converter control method, and power converter control program

Abstract

To shorten a parallel-off time from a power system side to a non-utility generator side in comparison with a conventional high-speed current limiting breaker when an abnormality occurs in the power system.SOLUTION: The high-speed current breaker is provided on a power line, and includes a rectifier bridge circuit in which a reactor element is connected between a pair of DC terminals, a power converter connected in parallel with the reactor element, and a power converter control unit that controls the power converter such that the power converter outputs a voltage in a direction opposite to a direction of a voltage applied to the reactor element when an abnormality occurs in a power system.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a high-speed current-limiting circuit breaker, a power converter control method used in the high-speed current-limiting circuit breaker, and a power converter control program used in the high-speed current-limiting circuit breaker. [Background technology]

[0002] Conventionally, there has been a high-speed current-limiting circuit breaker that is installed on a power line connecting a power system and a critical load, and that disconnects a private generator connected to the critical load from the power system in the event of an abnormality in the power system.

[0003] One such type of high-speed current-limiting circuit breaker, as shown in Patent Document 1, for example, includes a circuit breaker, a single-phase rectifier circuit provided on a power line and connected to a thyristor, and a DC reactor connected between two DC terminals of the single-phase rectifier circuit. When the power system is connected to important loads, the interconnection impedance is nearly zero, and interconnection loss due to the high-speed current-limiting circuit breaker is virtually negligible. In addition, in the event of an abnormality in the power system, such as a momentary sag, the fault current is rectified by the single-phase rectifier circuit and limited by the DC reactor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-264932 Summary of the Invention [Problem to be solved by the invention]

[0005] In a conventional high-speed current-limiting circuit breaker, when an abnormality such as a momentary sag occurs in the power system, it takes about 3 / 4 of a cycle to disconnect the private generator from the power system.

[0006] Therefore, the present invention has been made in consideration of the above problems, and its main objective is to shorten the disconnection time required to disconnect the private generator from the power system side compared to conventional high-speed current-limiting circuit breakers when an abnormality occurs in the power system. [Means for solving the problem]

[0007] That is, the high-speed current-limiting circuit breaker of the present invention is provided on a power line connecting a power system and a critical load, and is a high-speed current-limiting circuit breaker that disconnects a generator connected to the critical load from the power system when an abnormality occurs in the power system, and is characterized by comprising: a rectifier bridge circuit that is provided on the power line and has a reactor element connected between a pair of DC terminals; a power converter that is connected in parallel with the reactor element; and a power converter control unit that controls the power converter so that the power converter outputs a voltage that is opposite in direction to the voltage applied to the reactor element when an abnormality occurs in the power system.

[0008] In such a high-speed current-limiting circuit breaker, the power converter is connected in parallel with the reactor element, and the power converter control unit controls the power converter so that, when an abnormality occurs in the power grid, the power converter outputs a voltage that is opposite to the direction of the voltage applied to the reactor element, so that the current flowing through the reactor element after the occurrence of an abnormality in the power grid can be reduced to zero more quickly than in conventional high-speed current-limiting circuit breakers. Therefore, when an abnormality occurs in the power grid, the parallel-off time can be made shorter than in conventional high-speed current-limiting circuit breakers. Furthermore, since the object of control of the power converter control unit is the power converter, the power converter control unit can quickly control the power converter when an abnormality occurs in the power system, compared to a mechanical switch.

[0009] The power converter may further include a current measuring unit that measures the current flowing through the reactor element, and the power converter control unit may control the power converter based on the current measured by the current measuring unit so that the current flowing through the reactor element is maintained at or above a predetermined value.

[0010] With this configuration, by maintaining the current flowing through the reactor element at a predetermined value or higher before an abnormality occurs in the power grid, it is possible to prevent a voltage drop on the private generator side connected to the important load when an abnormality occurs in the power grid.

[0011] The predetermined value is preferably 1.1 times the peak value of the interconnection current.

[0012] With this configuration, when the power system is operating normally, the current flowing through the reactor element is maintained at 1.1 times or more the peak value of the rated interconnection current. Therefore, for example, if there is a sudden increase in important load current, it is possible to reliably prevent a voltage drop on the side of the private generator connected to the important load.

[0013] The power converter control unit preferably controls the power converter based on a voltage from the generator.

[0014] With this configuration, the voltage from a generator such as a private generator connected to an important load is stable compared to the voltage from the power grid, so the power converter control unit can stably control the power converter.

[0015] A power converter control method used in a high-speed current-limiting circuit breaker, which is provided on a power line connecting a power system and a critical load and includes a rectifier bridge circuit having a reactor element connected between a pair of DC terminals, and a power converter connected in parallel with the reactor element, characterized in that, when an abnormality occurs in the power system, the power converter is controlled so that it outputs a voltage that is opposite in direction to the voltage applied to the reactor element. A power converter control program used in a high-speed current-limiting circuit breaker that is provided on a power line connecting a power system and a critical load and includes a rectifier bridge circuit having a reactor element connected between a pair of DC terminals, and a power converter connected in parallel with the reactor element, characterized in that, when an abnormality occurs in the power system, the program causes a computer to function as a power converter control unit that controls the power converter so that the power converter outputs a voltage that is opposite in direction to the voltage applied to the reactor element.

[0016] With this configuration, it is possible to obtain the same effects as those of the above-described high-speed current-limiting circuit breaker. [Effects of the Invention]

[0017] According to the present invention configured in this manner, when an abnormality occurs in the power system, the disconnection time required to disconnect the private generator side from the power system side can be made shorter than with conventional high-speed current-limiting circuit breakers. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic diagram showing a high-speed current-limiting circuit breaker according to an embodiment of the present invention; [Figure 2] 2 is a schematic diagram showing a rectifier bridge circuit in the embodiment when the power system is normal. FIG. [Figure 3] 2 is a schematic diagram showing a rectifier bridge circuit in the embodiment when an abnormality occurs in the power grid. FIG. [Figure 4] 4 is a timing chart illustrating electrode converter control in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment of a power supply system according to the present invention will be described below with reference to the drawings. Note that, for ease of understanding, some parts may be omitted or exaggerated in schematic form in all of the drawings shown below. Identical components are designated by the same reference numerals, and their descriptions will be omitted where appropriate.

[0020] <Device configuration> The high-speed current-limiting circuit breaker 100 is used when the device is connected to the power system S with an interconnection impedance of approximately 0, and when an abnormality occurs in the power system S, such as a momentary sag, the high-speed current-limiting circuit breaker 100 limits the fault current that flows from a generator G connected to an important load L toward the power system S, thereby quickly interrupting the fault current. As shown in FIG. 1 , the high-speed current-limiting circuit breaker 100 in this embodiment is provided on a power line B that connects the power system S and the important load L.

[0021] Specifically, the high-speed current-limiting circuit breaker 100 includes a circuit breaker 1 provided on the power line B, and a rectifier bridge circuit 2 provided on the power line B, with a reactor element 23 connected between a pair of DC terminals.

[0022] The circuit breaker 1 is opened when an abnormality occurs in the power system S, and cuts off the electrical connection between the power system S and the important load L. The circuit breaker 1 is provided on the power line B, closer to the power system S than the rectifier bridge circuit 2.

[0023] The rectifier bridge circuit 2 interconnects the power system S and the generator G with an interconnection impedance of approximately zero when the power system S is normal, and when an abnormality occurs in the power system S, it limits the fault current that flows from the generator G connected to the important load L toward the power system S, thereby quickly interrupting the fault current. Specifically, the rectifier bridge circuit 2 includes a first parallel circuit unit 21 and a second parallel circuit unit 22 that are provided in parallel with each other on the power line B, and a reactor element 23 connected between the DC terminals of the first parallel circuit unit 21 and the DC terminals of the second parallel circuit unit 22.

[0024] The first parallel circuit unit 21 has the first thyristor element T1 and the first diode element D1 connected in series with the cathode of the first thyristor element T1 and the cathode of the first diode element D1 facing each other. In the first parallel circuit unit 21, the cathode of the first thyristor element T1 and the cathode of the first diode element D1 form a DC terminal. In the first parallel circuit unit 21, the first thyristor element T1 is provided closer to the power grid than the first diode element D1.

[0025] The second parallel circuit unit 22 has the second thyristor element T2 and the second diode element D2 connected in series with the anode side of the second thyristor element T2 and the anode side of the second diode element D2 facing each other. In the second parallel circuit unit 22, the anode side of the second thyristor element T2 and the anode side of the second diode element D2 form DC terminals. In the second parallel circuit unit 22, the second thyristor element T2 is provided closer to the power grid than the second diode element D2.

[0026] The reactor element 23 is connected between the DC terminals of the first parallel circuit unit 21 and between the DC terminals of the second parallel circuit unit 22. In this embodiment, the reactor element 23 is a DC reactor.

[0027] With this configuration, as shown in FIG. 2, when the power system S and the generator G are interconnected (hereinafter also referred to as a steady state), a DC current corresponding to the peak value of the interconnection current, which is the current that flows when the power system S and the generator G are interconnected, flows through the reactor element 23, and the current flowing from the first parallel circuit unit 21 to the second parallel circuit unit 22 via the reactor element 23 is a DC component, so the interconnection impedance is approximately zero. A DC component having the same magnitude as the peak value of the interconnection current circulates through the first parallel circuit unit 21 and the second parallel circuit unit 22. Furthermore, a current having a waveform in which a DC component is superimposed on an AC component flows through the first parallel circuit unit 21 and the second parallel circuit unit 22, and the current that does not pass through the zero point passes through regardless of the rectification direction of each element.

[0028] On the other hand, in the event of an abnormality in the power system S, such as a momentary voltage sag, the fault current is larger than the DC component superimposed on the first parallel circuit unit 21 and the second parallel circuit unit 22 in the steady state, and is therefore rectified by the elements of the first parallel circuit unit 21 and the second parallel circuit unit 22. Specifically, as shown in FIG. 3 , the first diode element D1 of the first parallel circuit unit 21 and the second thyristor element T2 of the second parallel circuit unit 22 rectify the fault current, and the AC component passes through the reactor element 23, thereby limiting the AC component. Then, while the reactor element 23 is limiting the AC component, the second thyristor element T2 is quickly shut off. This causes the generator G to be disconnected from the power system S.

[0029] Furthermore, the high-speed current-limiting circuit breaker 100 includes a power converter 3 connected in parallel to the reactor element 23, a current measuring unit 4 that measures the current flowing through the power converter 3, and a power converter control unit 61 that constitutes a control device 6 that controls the power converter 3.

[0030] 1, the power converter 3 has a cathode connected between DC terminals of the first parallel circuit unit 21 and the first parallel circuit unit 21 side of the reactor element 23, and an anode connected between DC terminals of the second parallel circuit unit 22 and the second parallel circuit unit 22 side of the reactor element 23. In this embodiment, the power converter 3 is a DC / AC bidirectional converter.

[0031] Specifically, in the power converter 3, the anode side of the thyristor switch and the cathode side of the thyristor switch are connected in series, and the thyristor units 31 provided corresponding to each phase are connected in parallel with each other. In each thyristor unit 31, an auxiliary power supply (not shown) of the generator G is connected between the two thyristor switches via a transformer 5. Note that each thyristor unit 31 may be connected to the generator G.

[0032] The current measuring unit 4 is provided between the reactor element 23 and the anode side of the power converter 3, and measures the DC component current flowing through the power converter 3. The current measuring unit 4 is, for example, a direct current transformer (DCCT). The current measuring unit 4 may be provided between the reactor element 23 and the cathode side of the power converter 3, or may be provided in the reactor element 23.

[0033] The control device 6 is a dedicated or general-purpose computer equipped with a CPU, internal memory, input / output interface, A / D converter, etc., and performs at least the function of a power converter control unit 61 by executing programs stored in various memories and by various devices working together.

[0034] When an abnormality occurs in the power system S, the power converter control unit 61 controls the power converter 3 so that the power converter 3 outputs a voltage in the opposite direction to the direction of the applied voltage applied to the reactor element 23. Specifically, the power converter control unit 61 receives the start of operation of a high-speed undervoltage detector (not shown) or the start of current-limiting operation of the reactor element 23 due to, for example, a momentary sag in the power system S, and causes the power converter 3 to output a voltage in the opposite direction (i.e., from the second parallel circuit unit 22 to the first parallel circuit unit 21) to the applied voltage of the reactor element 23 directed from the first parallel circuit unit 21 to the second parallel circuit unit 22. More specifically, as shown in FIG. 3 , the power converter control unit 61 controls the phase of the thyristor switch constituting the power converter 3, so that the power converter 3 outputs a voltage in the direction from the anode side of the power converter 3 to the cathode side of the power converter 3 via the reactor element 23. Here, the start of the current limiting operation of reactor element 23 is determined by the generation of a voltage in a search coil (not shown) provided in reactor element 23.

[0035] As a result, the current flowing through the reactor element 23 is attenuated linearly. dc , the inductance of the reactor element 23 is L dc Then, the current flowing through the reactor element 23 is -Vdc , and more specifically, -V dc / L dc It decays linearly with a slope of

[0036] Furthermore, the power converter control unit 61 controls the power converter 3 based on the current measured by the current measurement unit 4 so that the current flowing through the reactor element 23 is maintained at or above a predetermined value. Specifically, as shown in FIG. 1 , in a steady state, the power converter control unit 61 receives the voltage of the generator G and controls the phase of the thyristor switch constituting the power converter 3, thereby maintaining the current flowing through the reactor element 23 at or above a predetermined value. Here, the voltage of the generator G received by the power converter control unit 61 is, for example, a three-phase synchronous voltage from an auxiliary power supply (not shown) on the generator G side. Furthermore, the predetermined value for maintaining the current flowing through the reactor element 23 is the maximum peak value assumed as the load current of the generator G, for example, 1.1 times the peak value of the grid-connected current.

[0037] With this configuration, the DC current peak value of the reactor element 23 is adjusted to be equal to or higher than the peak value of the interconnection current. As a result, before an abnormality occurs in the power system S, the reactor element 23 is maintained at a value equal to or higher than the peak value of the interconnection current.

[0038] <Power converter control method> Next, a power converter control method will be described with reference to FIG.

[0039] (1) Normal operation of power system S When the power system S is in a normal state, the AC impedance of the reactor element 23 is approximately zero. A DC component of the same magnitude as the interconnection current circulates in the first parallel circuit unit 21 and the second parallel circuit unit 22, and a current having a waveform in which a DC component is superimposed on an AC component flows, and the current that does not pass through the zero point passes regardless of the rectification direction of each element.

[0040] Furthermore, the current measuring unit 4 measures the current flowing from the reactor element 23 to the anode side of the power converter 3. The power converter control unit 61 acquires the current measured by the current measuring unit 4 and controls the power converter 3 so that the current flowing through the reactor element 23 is maintained at or above a predetermined value. In this case, the power converter control unit 61 controls the phase of the thyristor switch that constitutes the power converter 3 based on the voltage from the generator G.

[0041] (2) When an abnormality occurs in power system S On the other hand, when an abnormality such as a momentary voltage sag occurs in the power system S, the fault current is rectified by the elements of the first parallel circuit unit 21 and the second parallel circuit unit 22. Specifically, the AC component of the fault current is first rectified by the first diode element D1 of the first parallel circuit unit 21, passes through the reactor element 23, and is rectified by the second thyristor element T2 of the second parallel circuit unit 22. The AC component of the fault current is limited when passing through the reactor element 23.

[0042] Then, when limiting of the AC component of the fault current begins, the power converter control unit 61 begins controlling the power converter 3 so that it outputs a voltage that is reverse to the voltage applied to the reactor element 23. As a result, as shown in FIG. 4, the fault current decays linearly, and the zero point of the fault current occurs approximately 3 / 8 of a cycle after the momentary sag. As a result, the second thyristor element T2 is high-speed tripped approximately 3 / 8 of a cycle after the momentary sag occurs. This causes the generator G to be disconnected from the power grid S. Therefore, it was confirmed that the disconnection time for the generator G to be disconnected from the power grid S is shortened compared to the conventional high-speed current limiting circuit breaker, which takes approximately 3 / 4 of a cycle after the momentary sag occurs.

[0043] <Effects of this embodiment> According to this embodiment, the power converter 3 is connected in parallel with the reactor element 23, and the power converter control unit 61 controls the power converter 3 so that, when an abnormality occurs in the power grid S, the power converter 3 outputs a voltage that is opposite to the direction of the voltage applied to the reactor element 23. This makes it possible to reduce the current flowing through the reactor element 23 to zero more quickly than conventionally after an abnormality occurs in the power grid S. Therefore, when an abnormality occurs in the power grid S, the parallel-off time can be made shorter than in conventional high-speed current-limiting circuit breakers. Furthermore, since the object of control of the power converter control unit 61 is the power converter 3, the power converter control unit 61 can quickly control the power converter 3 when an abnormality occurs in the power system S, compared to a mechanical switch.

[0044] <Other embodiments> The present invention is not limited to the above-described embodiment.

[0045] In the above embodiment, the power converter 3 is a bidirectional converter, but is not limited to this and may be a PMW converter, a bidirectional chopper circuit, or the like.

[0046] In the above embodiment, the rectifier bridge circuit 2 is a mixed bridge of diode elements and thyristor elements, but it may also be a thyristor bridge or a diode bridge. Note that when the rectifier bridge circuit 2 is a mixed bridge and thyristor bridge, the high-speed current-limiting circuit breaker 100 does not need to include the circuit breaker 1.

[0047] In the above embodiment, the power converter control unit 61 performs two controls: (1) when an abnormality occurs in the power system S, controls the power converter 3 so that the power converter 3 outputs a voltage that is opposite in direction to the voltage applied to the reactor element 23, and (2) controls the power converter 3 so that the current flowing through the reactor element 23 is maintained at a predetermined value or higher based on the current measured by the current measurement unit 4. However, this is not limited to this. In order to shorten the parallel-off time, the power converter control unit 61 does not need to perform the control (2).

[0048] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0049] 100... High-speed current limiting circuit breaker 2. Rectifier bridge circuit 21...1st parallel circuit section 22...Second parallel circuit section 23 Reactor element 3. Power Converter 4...Current measurement section 5. Transformer 6. Control device 61 Power converter control section S...Power system L...Important load G···Generator B...power line D1: First diode element D2: Second diode element T1: First thyristor element T2: Second thyristor element

Claims

1. A high-speed current-limiting circuit breaker that is provided on a power line connecting a power system and a critical load, and that disconnects a generator connected to the critical load from the power system when an abnormality occurs in the power system, a rectifier bridge circuit provided on the power line and having a reactor element connected between a pair of DC terminals; a power converter connected in parallel with the reactor element; and a power converter control unit that controls the power converter so that, when an abnormality occurs in the power system, the power converter outputs a voltage that is opposite in direction to the voltage applied to the reactor element.

2. a current measuring unit for measuring a current flowing through the reactor element; 2. The high-speed current-limiting circuit breaker according to claim 1, wherein the power converter control unit controls the power converter based on the current measured by the current measurement unit so that the current flowing through the reactor element is maintained at a predetermined value or higher.

3. The high-speed current-limiting circuit breaker according to claim 2 , wherein the predetermined value is 1.1 times the peak value of the interconnection current.

4. The high-speed current-limiting circuit breaker according to claim 1 , wherein the power converter control unit controls the power converter based on a voltage from the generator.

5. A power converter control method used in a high-speed current-limiting circuit breaker, the high-speed current-limiting circuit breaker being provided on a power line connecting a power system and a critical load, and including a rectifier bridge circuit having a reactor element connected between a pair of DC terminals, and a power converter connected in parallel with the reactor element, comprising: a power converter control method for controlling the power converter so that, when an abnormality occurs in the power system, the power converter outputs a voltage that is opposite in direction to the voltage applied to the reactor element;

6. A power converter control program used in a high-speed current-limiting circuit breaker, the high-speed current-limiting circuit breaker being provided on a power line connecting a power system and a critical load, the high-speed current-limiting circuit breaker including a rectifier bridge circuit having a reactor element connected between a pair of DC terminals, and a power converter connected in parallel with the reactor element, A power converter control program that causes a computer to function as a power converter control unit that controls the power converter so that, when an abnormality occurs in the power system, the power converter outputs a voltage that is opposite in direction to the voltage applied to the reactor element.

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