JPH0767257A - Power system stabilization system and frequency stabilization system - Google Patents

Abstract

PURPOSE:To prevent the unstable phenomenon, including the fluctuation of frequency, due to power disturbance from spreading upon occurrence of fault on a power system by determining an amount of power supply to an interconnected DC system based on system information and then determining a restriction amount of power supply to the interconnected DC system based on fault information and the amount of power supply thus determined. CONSTITUTION:Upon occurrence of a fault which may cause a network separation on a power system, means 12 detects the fault. A fault information detection value is then delivered to a DC transmission interconnection (BTB) transmission amount regulation means 17. The means 17 decides whether a BTB must be localized from the fault information detection value and a BTB transmission amount command signal and when a decision is made that a BTB must be localized, a BTB transmission amount localizing signal is delivered to an AC interconnection line. This system prevents the imbalance phenomenon, including the fluctuation of frequency, due to power disturbance from spreading upon occurrence of fault in a power system facility or on the AC interconnection line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to prevent out-of-steps when a ground fault or a short-circuit accident occurs in the power system equipment or interconnection line of a power system in which a plurality of power systems are connected by direct current transmission and alternating current. The present invention relates to a power system stabilizing device and a frequency stabilizing device for stabilizing the power system when there is a fear.

[0002]

2. Description of the Related Art When a ground fault or a short-circuit accident occurs in equipment in the power system such as a power transmission line or a bus bar in a power system, a generator connected to the system in which the accident occurred will accelerate and step out due to the continuation of these accidents. When there is a risk of grid separation, immediately after the occurrence of the accident, by disconnecting the generator assumed in advance from the power grid at the location of the accident (hereinafter referred to as "electric control"), the grid separation is prevented and the power grid is stabilized. I am trying to measure.

An example of the conventional method will be described with reference to FIG.
In FIG. 7, reference numeral 10 denotes a power system stabilizing device, which includes a power flow value detection means 11, an accident detection means 12, and an electronic control command means 13, detects the content of the accident using the power flow value and the accident information, and determines the accident location. This is to disconnect the generator that is assumed in advance.

FIG. 8 is a diagram showing an example of a conventional frequency control, and shows an interconnection system of a plurality of AC systems including a power conversion device used for frequency conversion and the like. In the figure, 1-1,
1-2 and 1-3 are AC systems, AC systems 1-1 and 1-2 are AC interconnection lines 2-1, AC systems 1-2 and 1-3 are AC interconnection lines 2-2,
The AC systems 1-1 and 1-3 are connected via AC interconnection lines 2-3 and 2-4 and a DC interconnection facility 3, respectively. DC interconnection facility 3
Is the converter AC bus 4-1, 4-2, converter transformer 5-1, 5-2
Power converters 6-1, 6-2, a smoothing reactor 7, a controller 8, and a power detector 9. Here, for convenience of explanation, the flow of electric power is assumed to be alternating current system 1-1 to 1-2, 1-1 to 1-3, 1-2 to 1-3.

In such an interconnection system, when the AC interconnection line 2-1 is cut off due to a ground fault or the like (route disconnection state), the AC system 1-1 flows to the AC interconnection line 2-1. However, the effective power will be surplus and the frequency of AC system 1-1 will rise. At this time, the DC interconnection equipment 3 is operating or stopped completely independently of the state of the AC interconnection line 2-1.

[0006]

In the former of the above conventional methods, when a large accident occurs in the electric power system, which may cause a system separation if left unattended, the previously envisioned generator is electrically controlled. , When multiple power systems are connected by an AC interconnection line, when the power fluctuation between multiple power systems expands due to an accident, the system is separated near the AC interconnection line even if the conventional equipment is used to control electricity. Is likely to occur and is difficult to stabilize. Further, in the case of such a power system in which a plurality of power systems are connected by an AC interconnection line, if a power fluctuation occurs in the power system, an electric generator is assumed to be controlled. Is difficult As described above, when an accident in which power fluctuations spread among a plurality of power systems occurs, there is a problem in that the conventional stabilization system by electric control of the device is difficult.

In the latter case, when the AC interconnection line 2-1 is in a route disconnection state due to a ground fault or the like, in the AC system 1-1, the effective power is excessive and the frequency rises, but when the frequency rises,
The frequency is controlled to return to the original frequency by disconnecting the generator by electric control or by suppressing the output of active power by the controller of the generator. However, the output control of the generator is generally poor in response, and when the frequency rise is large, the protection device operates and the generator trips, and it takes time to recover. Further, even if the trip does not occur, the large frequency fluctuation is also inconvenient for the load in the system, so it is desirable to keep the frequency of the AC system as constant as possible. Therefore, the present invention is intended to expand an unstable phenomenon including frequency fluctuation due to power fluctuation when an accident occurs in a facility in the power system or an AC interconnection line in a plurality of DC-connected and AC-connected power systems. An object is to provide a power system stabilizing device and a frequency stabilizing device that can be prevented.

[0008]

An electric power system stabilizing device according to claim 1 of the present invention has a plurality of electric power systems, and an accident occurs in an electric power facility in these electric power systems, leading to an accident occurrence system. When the generator is out of step to continue these accidents and there is a risk of grid disruption, the power system that stabilizes the power system by predicting and isolating the generator that may cause grid disruption when an accident occurs In the stabilizing device, a BTB (DC power transmission interconnection) that connects the power grids, a BTB power transmission amount command unit that determines and commands a power transmission amount to the BTB based on grid information, and the BTB power transmission amount command. It is composed of a BTB power transmission amount adjusting means for outputting the adjustment amount (narrowing amount) of the amount of electric power to the BTB from the command signal from the department and the accident information.

A frequency stabilizing device according to a second aspect of the present invention includes a device for detecting the electric energy of the AC interconnection line, a device for storing the signal thereof, and a signal for cutting off the signal and the AC interconnection line. It consists of a transfer device and a device that adjusts the power of the DC interconnection equipment according to the cutoff signal, and adds the amount of power immediately before the AC interconnection line is cut off to the DC power setting signal of the DC interconnection equipment. It is configured to do.

[0010]

In the power system stabilizing device according to the first aspect of the present invention, in a power system composed of a plurality of power systems, the power systems are connected by BTB to the power system of the generator before the accident. Depending on the power system status such as the connection status, power generation amount, power transmission amount of the transmission line, connection status of the transmission line, etc., the BTB power transmission amount is controlled before the accident, and when the accident occurs in the equipment in the power system, the magnitude of the accident B based on the accident conditions such as
Narrow the transmitted power of TB.

In the frequency stabilizing device according to the second aspect of the present invention, when the AC interconnection line is cut off, the power flowing in the AC interconnection line is transmitted to another AC system by the DC interconnection facility. Therefore, by cutting off the AC interconnection line, it is possible to prevent surplus or shortage of active power in the AC system that is a single system, and suppress the frequency fluctuation.

[0012]

Embodiments will be described below with reference to the drawings. Figure 1
FIG. 8 is a configuration diagram of an embodiment of a power system stabilizing device according to the present invention, and corresponds to the conventional example of FIG. 7. In FIG. 1, the same parts as those in FIG. The parts added by the present invention are the system information detecting means 14, the BTB power transmission amount determining means 15, the BTB power transmission amount command means 16, and the BTB power transmission amount adjusting means 17. Then, the system information detecting means 14 detects system information such as the connection state of the specific power transmission line, the power generation amount of the specific power generator, and the power transmission amount of the specific power transmission line. The BTB power transmission amount determining means 15 determines the BTB power transmission amount based on the system information detection value. The BTB power transmission amount command means 16 sends the determined BTB power transmission amount command signal to the BTB power transmission amount adjusting means 17. The BTB means a DC power transmission interconnection.

Next, the operation will be described. First, when a major accident that develops into system separation occurs in the power system, the accident detection means 12 detects the accident. The detected accident information is sent to the BTB power transmission amount adjusting means 17 as an accident information detection value. The BTB power transmission amount adjusting means 17 determines whether to narrow down the BTB from the detected accident information value and the BTB power transmission amount command signal, and if it judges that the BTB should be narrowed down, the BTB transmission amount
The power transmission amount narrowing signal is transmitted to the target AC interconnection line.

FIG. 2 is an explanatory diagram of signal transfer between a plurality of power systems and BTB when the power system stabilizing device 10 of the present invention is installed in the power system in which a plurality of power systems are connected by BTB. Is. Here, the conventional function 18 is composed of the power flow value detecting means 11, the accident detecting means 12, and the electric control commanding means 13, and the BTB transmission amount commanding section 19 is the system information detecting means.
14, BTB power transmission amount determination means 15, BTB power transmission amount command means 16
Consists of. The BTB power transmission amount command unit 19 always inputs system information from both the power system A and the power system B, and transmits a BTB power transmission amount command signal to the BTB. BT that received this
B transmits DC power between the power system A and the power system B in accordance with the BTB power transmission amount command signal.

When an accident occurs in the electric power system A or the electric power system B, the accident information is input to the electric power system stabilizing device 10 and the BT
Based on the accident information and the system information, the B power transmission amount adjusting means 17 transmits a BTB power transmission amount narrowing signal to the BTB. As a result, the BTB power transmission amount is narrowed down. Here, consider a case where the respective power systems are connected by an AC interconnection line. In this case, even if the power system sway between the respective systems is large due to the accident of the power system A or the power system B, there is no sway between the power system A and the power system B if only DC transmission of BTB is performed. Only the power system where the accident occurred will cause power fluctuation. At this time, it depends on the BTB power transmission amount before the accident and the BTB power transmission amount after the accident whether or not the power fluctuation of the power system in which the accident occurs is sustained or subsided. Furthermore, if the power fluctuation continues even after the BTB power transmission amount is narrowed down, the conventional function 18 transmits an electric control command signal to stabilize the electric power system. That is, the generator that has received the electric control command signal is disconnected from the electric power system.

FIG. 3 is an explanatory diagram showing a state before an accident in a power system in which a plurality of power systems, that is, a power system A and a power system B are connected by BTB. Here, it is assumed that the electric power P is flowing from the electric power system A to the electric power system B. If the electric power flowing through BTB is Pd,

[Equation 1] P = Pd (1) Generally, immediately after an accident occurs in the power system, the transmitted power decreases. Now, assuming that the electric power P is flowing from the electric power system A to the electric power system B, assuming that the electric power systems are connected by an AC interconnection line, the electric power of P ′ is supplied from the electric power system A after the accident occurs. It flows to the power grid B. in this case,

[Equation 2] P ′ <P ……………… (2). Here, if P '<Pd, the amount of power extracted from the power system A exceeds the amount of power generation in the power system A. In this case, the load on the generator near the BTB becomes heavy,
If the capacity of this generator is small, it will decelerate rapidly and the generator near BTB will not be able to synchronize with other generators, and the accident will spread.

Further, if P '>> Pd, there is a problem that the frequency in the system of the power system B is drastically lowered and the accident spreads due to the operation of the frequency relay. Therefore, in order to stably supply the electric power from the electric power system A to the electric power system B even after the occurrence of the accident, it is necessary to change the BTB transmission amount after the accident to a range that is assumed. The amount of BTB transmission after the occurrence of this accident is the total power generation amount of the power system A, the total power generation amount of the power system B, the power system A
Is roughly determined by the flow of power from the power supply to the power grid B. However, the capacity of the generator near the BTB and the amount of power generation also have a great influence. For this reason, when the power system is large and complicated, it is necessary to determine it by simulation to determine the BTB transmission amount.

FIG. 4 is an example of a graph for determining the amount of BTB power transmission after an accident occurs. The horizontal axis of the figure is the power P from the power system A to the data B, and the vertical axis is the BTB transmission amount. The parameters include the power generation amount of the electric power system A and the electric power system B. If the graph is expressed by an equation, it can be expressed by the function F1 shown in the equation (3).

[ _Equation 3] P _btb = F1 (PA, PB, P) (3) where P _btb : BTB transmission amount PA: Power generation amount of power system A PB: Power generation amount of power system B P: Power Power from grid A to grid B

It can also be expressed as the following equation (4).

## _EQU00004 ## P _btb = (Al * PA + Be * PB) * P (4) However, Al and Be are coefficients and differ depending on the system.
Further, the expression (3) can be expanded and expressed by the function F2 shown in the expression (5).

[ _Equation 5] P _btb = F2 (PA, PB, P, Pe) (5) However, Pe: Generator output of a generator that is greatly affected by interruption of the AC interconnection line (5) It can also be expressed as Eqs. (6) and (7).

[ _Equation 6] P _btb = (Al * PA + Be * PB) * P + Ga * Pe ...... (6) P _btb = (Al * PA + Be * PB + Ga * Pe) * P ...... (7) However, the coefficient for Ga: Pe It depends on the generator and system. The above formulas (3) and (5) are applied to determine the BTB power transmission amount after being narrowed down by the BTB power transmission amount adjusting means shown in FIG. Also, PA, PB, P, Pe are detected as the system information detection values in FIG.

In the above-mentioned embodiment, it is explained that both the electric power control command signal and the BTB power transmission amount narrowing signal are output. However, in some cases, the spread of the accident can be prevented only by narrowing down the BTB transmission amount. Therefore, it is necessary to transmit the BTB power transmission amount narrowing-down signal for the time being before outputting the electric command command signal. For that purpose, transmission signal delay means is installed to coordinate transmission.

Further, in FIG. 1, the power flow value detecting means 11 and the system information detecting means 14 may be integrated as one function. Further, in FIG. 1, instead of the BTB power transmission amount command signal, the BT
The B power transmission amount may be received from the BTB main body. According to the above embodiment, by controlling the transmission amount of BTB according to the power system condition before and after the accident, it is possible to prevent the disconnection of the generator around the BTB when the accident in which the power fluctuation is increased occurs. It is possible to perform stabilization control that prevents the expansion of power fluctuation.

FIG. 5 is a block diagram of another embodiment of the present invention, which corresponds to the conventional example of FIG. 5, parts corresponding to those in FIG. 8 are designated by the same reference numerals, and description thereof will be omitted. In the present embodiment, when the AC interconnection line connecting the power system is cut off, the DC interconnection equipment is controlled in conjunction with this interruption, and the surplus active power of the AC system which has become an independent system is changed to another one. The frequency is prevented from increasing or decreasing by transmitting power to the AC system or receiving insufficient power from another AC system.

The configuration added to FIG. 8 of the conventional example is a power detector 20 for detecting the power amount of the AC interconnection line 2-1 and a storage device 21 for storing the power amount, and a shutoff signal transfer for forwarding the shutoff signal. This is the point where the device 23 is provided, and when the AC interconnection line 2-1 is cut off, the power amount immediately before that is output from the storage device 21, and this signal (power amount) is used as the DC power setting signal by the adder 22. They are added and transferred to the control device 8 as a new DC power setting signal.

FIG. 6 is a diagram for explaining the control device 8 and the frequency stabilizing device 25 in detail. 6, the same parts as those in FIG. 5 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the controller 8 includes a constant power controller 81 and a constant current controller 82.
And the code P _dp in the adder 22 is a DC power setting signal. Others are the same as in FIG.

Next, the operation will be described. AC interconnection line 2-1
When the power is cut off due to a ground fault or the like, the storage device 21 outputs the amount of electric power flowing to the AC interconnection line 2-1 immediately before the cutoff, and the adder 22 adds it to the DC power setting signal P _dp. , And is transferred to the control device 8 of the DC interconnection facility as a new DC power setting signal. As a result, the amount of power transmitted from the AC grid 1-1 to the AC grid 1-3 by the DC grid 3 is increased, and the active power remaining in the AC grid 1-1 is reduced accordingly. In other words, the total amount of power transmission seen from AC system 1-1 has not changed before and after AC interconnection line 2-1 is cut off, so the frequency in AC system 1-1 can be kept stable. According to the present embodiment, there is an effect that the frequency can be stabilized when the AC interconnection line is cut off (route interruption) and the AC system becomes a single system.

The embodiment of FIG. 5 is based on the assumption that it is a constant power control device, and adds the amount of power immediately before the AC interconnection line 2-1 is cut off to the DC power setting signal. The value obtained by dividing the added power amount by the rated voltage of the DC interconnection facility is
Similar effects can be obtained by adding to the DC current setting signal of the constant current controller. Further, instead of operating when the cutoff signal is received, the same effect can be obtained by transferring the changed amount to the control device 8 when the power of the AC interconnection line 2-1 suddenly changes.

[0027]

As described above, according to the present invention, when an accident occurs in the equipment in the power system or the AC interconnection line,
Since it is configured to control the electric energy of the DC equipment, stable control of the electric power system is possible. In particular, according to claim 1, when an accident occurs in which power fluctuations among a plurality of power systems expand, by controlling the amount of BTB transmission, it is possible to perform stabilization control that does not cause step out of the generator or grid separation. Becomes Further, this stabilization control makes the stabilization control by electric control unnecessary, and prevents a new instability phenomenon such as a frequency decrease accompanying disconnection from the power system of the generator.
Further, according to claim 2, a certain AC interconnection line is cut off (route cut) by providing a frequency stabilizing device for controlling the DC interconnection facility in association with a change in electric power flowing through the AC interconnection line. This has the effect of adjusting the electric power that is surplus or insufficient in the AC system that becomes a separate system, and can keep the frequency in the AC system stable.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a power system stabilizing device according to the present invention.

FIG. 2 is an explanatory diagram of signal transfer between a power system stabilizing device according to the present invention, a plurality of power systems, and BTB in a power system in which a plurality of power systems are connected by BTB.

[Fig. 3] A plurality of power systems, power system A and power system B are B
Explanatory drawing which showed the state before the accident in the electric power system connected by TB.

FIG. 4 is a graph example for determining the amount of BTB power transmission after an accident.

FIG. 5 is a configuration diagram of another embodiment.

FIG. 6 is a partial view showing details of a control device and a frequency stabilizing device in FIG.

FIG. 7 is a diagram showing one of conventional examples.

FIG. 8 is a view showing another one of the conventional examples.

[Explanation of symbols]

 10 Power system stabilizing device 11 DC value detecting means 12 Accident detecting means 13 Electricity control commanding means 14 System information detecting means 15 BTB transmission quantity determining means 16 BTB transmission quantity commanding means 17 BTB transmission quantity adjusting means 18 Conventional function 19 BTB transmission quantity Command unit 20 Power detector 21 Memory device 22 Adder 23 Circuit breaker signal transfer device 24 Circuit breaker 25 Frequency stabilizer 81 Constant power controller 82 Constant current controller

Claims (2)

[Claims] 1. A system having a plurality of electric power systems, an accident occurs in an electric power facility in these electric power systems, and a generator connected to the system in which the accident occurs may be out of order to continue these accidents, which may lead to system disconnection. In a power system stabilizing device for predicting and isolating a power generator that may cause a grid disconnection when an accident occurs, and stabilizing the power system, a DC transmission interconnection (BTB) connecting the power systems. And BTB based on the system information
A BTB power transmission amount command unit that determines and commands a power transmission amount to the
An electric power system stabilizing device comprising: a BTB power transmission amount adjusting means for outputting an adjustment amount of an electric power amount to BTB from a command signal from the BTB power transmission amount command unit and accident information. 2. A power system in which a plurality of alternating current systems are interconnected by a direct current interconnection facility having an alternating current interconnection line and at least one constant power control device, the alternating current interconnection lines being interrupted by a failure. Then, the amount of electric power before the AC interconnection line is cut off is transmitted to the DC interconnection equipment, and this signal is added to the DC power setting signal, so that the surplus power in the AC grid is used by the DC interconnection equipment. Frequency stabilizing device for maintaining the frequency stability in the AC system by a power adjusting means for transmitting the power to another AC system or receiving the insufficient power from the other AC system.