JPH0496625A - Reverse power flow suppressor - Google Patents

Abstract

PURPOSE:To suppress a reverse power flow before a reverse power relay is operated when a reverse power flow is generated and to prevent a disconnection by detecting the reverse power flow, and temporarily connecting a load based on the output signal of a reverse power flow detector. CONSTITUTION:Received power from a power system 1 is measured by a wattmeter 34, and a reverse power flow detector 7 detects whether the measured value is reduced lower than a set value or not. If the set value is set to '0' or minus value, a reverse power flow detector 7 detects the minus reverse power flow of the received power. When a temporary load of regulating power consumption is applied based on the output signal of the detector 7, the load is increased, and the reverse power flow is eliminated. Thereafter, generated power is reduced by a governor regulation of a generator 5 to regulate to maintain the received power in a range in which the detector 7 does not detect the reverse power flow. The power consumption of the temporary load is reduced, and eventually to '0' to complete the operation of suppressing the reverse power flow.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to an electric facility in which power is received from a power grid and power is generated by a private generator, in which power is supplied from the private generator to the power grid. The present invention relates to a reverse power flow suppression device that suppresses so-called reverse power flow from becoming excessive.

[Conventional technology]

FIG. 4 is a single-line diagram of a conventional electric facility that receives power from the power grid and generates power from a private generator. In this figure, a power system 1 is connected to a power distribution line 4 via a circuit breaker 2.
and the private generator 5 are connected to supply power to the load 42. The power received from the electric power system is measured by a human-powered wattmeter 34 that includes the voltage of the wiring 35 stepped down by the voltage transformer 32 and the current measured by the current transformer 3I, and a signal is generated as the measured value. is indicated by ■. Further, a reverse power relay 33 is provided in the same circuit. When a reverse power flow occurs, in which power flows from the distribution line 4 toward the power grid 1, the reverse power relay 33 detects it based on a set value and shuts off the circuit breaker 2, thereby preventing power from flowing into the power grid 1. . This separation of private power generation equipment from the power grid is called disconnection. Note that although the reverse power relay 33 and the wattmeter 34 are actually provided in different circuits, they are shown as being provided in the same circuit in the figure because they are functionally the same. The same applies to a wattmeter 41, which will be described later.

The power of the generator 5 is measured by a wattmeter 41 into which the voltage of the wiring 35 and the current from the instrument current transformer 43 are input, and the measured value is a signal as shown by 0 of the generator 5. Voltage regulation is performed by governor regulator 51.

The governor regulator 51 subtracts the power value set by the power setting device 54 from the power value indicated by the signal ■ measured by the wattmeter 4 by a subtractor 53 and inputs it to the power controller 52 for power adjustment. By inputting the output signal of the generator 52 to the governor controller 51, the generated power of the generator 5 reaches the power setting value 5.
0 generator 5 controlled to match the set point by 4
Since the governor is mechanically operated to adjust the amount of high-pressure gas sent to the turbine when the generator 5 is a thermal power generator, its time constant is relatively large, such as several tens of seconds.

The above-mentioned reverse power relay 33 is set to interrupt the circuit breaker 2, for example, when the amount of power flowing toward the power grid 1 is 10% or more of the rated power for one second or more. The set values for the power ratio and duration vary depending on the rated voltage of the power system 1, etc. In addition, when reverse power flow occurs, it is necessary to quickly disconnect the power so that the impact on other consumers is small. There is a tendency for stricter setting values to be adopted. As described above, when a reverse power flow occurs, it is virtually impossible to control the amount of power in the reverse direction or reduce the duration by adjusting the governor to avoid disconnection.

[Problems to be Solved by the Invention] Since the capacity of the power system I is usually much larger than the capacity of the generator 5, the voltage and frequency of the power distribution line 4 are almost determined by the power system I. Therefore, the generator 5 is usually not provided with a control device that controls the voltage and frequency with high precision.

When disconnected, the private power generation equipment is disconnected from the power grid 1, so the voltage and frequency of the distribution line 4 are determined by the generator 5. Many of the causes of reverse power flow are load 42
This is because the capacity of the generator 5 suddenly decreases, but if the generator 5 is disconnected in this state, the voltage generated by the generator 5 will increase and the frequency will increase, causing the problem that the power on the distribution line 4 will become unstable. . Therefore, it is desirable for the private power generation equipment side to avoid disconnecting the line as much as possible.

An object of the present invention is to provide a reverse power flow suppression device that suppresses reverse power flow and prevents disconnection before a reverse power relay operates when reverse power flow occurs.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an electric power needle for measuring received tt power and a value measured by this wattmeter in an electric equipment that receives power from the power grid and generates power from a private generator. It shall be equipped with a reverse power flow detector that detects whether the power has fallen below a set value, and a temporary load that is temporarily turned on based on the output signal of this reverse power flow detector and whose power consumption can be adjusted. .

[Effect]

In the configuration of the present invention, the power meter measures the power received from the power system, and the reverse power flow detector detects whether this measured value is less than a set value. If this set value is set to 0 or a negative value, the reverse power flow detector can detect so-called reverse i42+t in which the received power is negative. This reverse 4? When a temporary load whose power consumption can be adjusted based on the output signal of the X detector is applied, the reverse power flow is eliminated by increasing the load. After this, the generated power is narrowed down by adjusting the generator governor, and vice versa? By adjusting the received power to a range in which the reverse power flow detector does not detect reverse power flow, the power consumption of the temporary load also decreases, and finally reaches O, completing the reverse power flow suppression operation.

〔Example〕

The present invention will be explained below based on examples. FIG. 1 is a single line diagram of electrical equipment showing an embodiment of the present invention, and components common to those in FIG. 4 are given the same reference numerals and detailed explanations are omitted. In this figure, the load 6 is connected to the distribution line 4 at - time. At this time, the load 6 is the transformer 62
and a resistor 64 whose power consumption is controlled by a thyristor converter 63 via this transformer 62. The firing angle of the thyristor converter 63 is controlled by firing pulses from a pulse generator 74. Further, a wattmeter 61 is provided to measure the power consumed by the load 6 during negative times.

A dedicated resistor 64 for the negative load 6 may be prepared, or an existing resistor 64 may be used, for example, by using the rapid limit resistance of the generator 5.

The reverse power flow detector 7 consists of a power setting device 71 and a subtractor 72, and the signal ■ as a measurement value of the wattmeter 34 is subtracted by the subtractor 72 from the value set by the power setting device 71, and the subtraction result is This is used as an output signal.

This output signal is input to the reverse power flow calculation regulator moderator 73.

This reverse power flow calculation regulator 73 consists of a power regulator and a relay (not shown), and the output signal of the power regulator is input to a pulse generator 74, and the temporary load 6 consumes power that substantially matches the reverse power flow power. Generates an ignition pulse that controls the On the other hand, the relay of the reverse power flow calculation regulator 73 operates when the input signal becomes positive, and drives the contact 67 which is the a contact and the contact 68 which is the b contact, turning on the contact 67 and turning on the contact 6.
Turn off 8.

This ms device has a self-excitation function, and when it is reset, it is manually operated. Contact point 67 is subtractor 75
Then, a signal obtained by subtracting the output signal (■) of the watt-hour meter 61 from the signal (■) is manually inputted to the power** device 52.

This input signal has a value proportional to the value obtained by subtracting the generated power of the generator 5 from the power consumption of the load 42, and the power consumption value of the load 42 is used instead of the setting value of the power setting device 54 during normal operation. It is equivalent to

The power setter 54 and subtracter 53, which are provided for conventional power adjustment, are separated from the power regulator 52 by turning off the b contact 68.

FIG. 2 is a waveform diagram showing temporal changes in each electric power bond to explain the operation when a reverse power flow occurs.

PL on the vertical axis is the power consumption of the load 42 in FIG. 1, P is the received power from the power grid l, rG is the generated power of the generator 5, P
, is the power consumption of the load 6 at - time 0 The numerical value marked O in the diagram corresponds to the value measured by the corresponding power needle in FIG. Based on this figure, how the above-described configuration operates when the power consumption of the load 42 suddenly decreases at time L1 from a normal state and a reverse power flow occurs will be described below.

(a) Normal state (1<1.) When there is no reverse power flow, the signal ■ is positive, so
Since the human power signal of the reverse four-flow calculation regulator 73 is negative, there is no signal to the pulse generator 65, and the relay that drives the two contacts 67 and 68 does not operate. Therefore, during - time, the load 6 does not consume power and the generator 5 generates the power set by the power setting value 54.

Φ) Reverse ill flow generation (t-t,) The power consumption PL of the load 42 is 21. As a result, the received power P becomes negative, causing a reverse power flow, and the power meter 3
4 becomes negative, the input signal of the reverse power flow calculation controller 73 becomes positive, and the thyristor converter 63 is controlled so that the reverse power flow detector is temporarily consumed by the load 6 and the reverse power flow becomes 0. is started. On the other hand, the relay built in the reverse power flow calculation controller 73 operates to turn on the contact 67 and turn off the contact 68.

(C) -Increase in load power consumption (t+ <t<tz)
- As the power consumption P of the load 6 increases, the reverse power/JL power P becomes O at time L2, and the reverse power flow detector 7
Since the output signal becomes 0, the power consumption amount of -time negative=6 is maintained constant thereafter. - Since the power consumption of the load 6 is controlled by controlling the firing angle of the thyristor converter 63, its time constant is small, and the reverse power flow is brought to 0 in a sufficiently small time compared to the setting time of the reverse power relay 33 mentioned above. Because it can be done, it will not be disbanded.

((Support) Decrease in power generated by generator 5 (tz < t
<tx) The governor is throttled by the governor regulator 51 so that power corresponding to the power consumption PL of the load 42, which has suddenly decreased, is generated, and the generated power P0 of the generator 5 decreases. As mentioned above, the time constant at this time is several tens of seconds, so as the power P decreases from 0, which is a much slower change than the change in the temporary load 6, the received power P slightly increases. Accordingly, the power consumption P0 of temporary load 6 is
The output power is also narrowed down and decreases in accordance with the decrease in the generated power P.
It's power P.

At time t when PL matches the power consumption PL of the load 42, the power consumption of the temporary load 6 becomes 0, and the series of operations for suppressing reverse power flow is completed at this point.

(e) Return to the normal state (L>1.) Since the contact 67 remains on and the contact 68 remains off, the relay of the reverse power flow calculation regulator 73 is artificially restored by a method not shown. . A method of automatically returning by detecting the time point t is also possible. At this time, the power generated by the generator 5 is set by the power setting device 54 in consideration of the state in which the power consumption of the load 42 is reduced.

FIG. 3 is a single line diagram of electrical equipment showing another embodiment of the present invention, and the difference from the embodiment of FIG.
0 is composed of a plurality of resistors 66 and a load switch 65 that can independently turn on/off these resistors. - The amount of power consumed by the load 60 is adjusted by turning the load switch 65 on and off.

This on/off control is performed by a reverse power flow calculation regulator 76, which consists of the same relay as in the case of FIG. The resistor 66 to be turned on is determined according to the value of the input signal from the device 72, and based on the result, the corresponding load switch 65 turns off the resistor 66 that is on. A command is issued to the primary load 60 separately for the case where the load switch 65 turns on the resistor 66 which is off.

- The power consumption of the temporary load 60 can only change stepwise, but when the power consumption of the load 42 and the generator power of the generator 5 match, all the load switches 65 of the temporary load 60 are turned off. Therefore, there is no problem in transitioning to the normal state.

The two embodiments described above are embodiments for equipment that performs control to maintain the generated power of the generator 5 at a set value,
In addition, there is a method in which the received power is controlled to maintain the set value, and in this case, the handling of the power measurement value for the reverse power flow calculation controller 73, 76 and the power controller 52 is different, but the basics are as follows. However, even in such a case, by temporarily applying a temporary load of 6.60, it is possible to increase the effect of the present invention in suppressing reverse power flow and preventing disconnection. Furthermore, instead of switching the input signal through the contacts 67 and 68 when the input signal of the power 1J4S unit 52 is disconnected, a configuration may be adopted in which the set value of the power set value 54 is artificially lowered using the same circuit configuration as shown in FIG. .

In the above explanation, the setting value of the power setting device 71 is set to 0, and a positive signal is output immediately when the signal ■ becomes negative. However, for example, if the setting value of the power ratio of the above-mentioned reverse power relay 33 is 10%, The setting value of the power setting device 71 may be set to 5%, which is half of that value.

In this case, since the reverse power flow power amount does not exceed 5% continuously, disconnection does not occur.On the other hand, the reverse power flow calculation controller 73
Alternatively, there is an advantage that the amount of power consumed by the temporary load 6.60 can be reduced to some extent by operating the temporary load 6.60.

〔Effect of the invention〕

As described above, this invention detects the occurrence of reverse power flow using a reverse power flow detector that detects whether the measured value of received power is set to 0 or a negative value and falls below a certain set value,
When a temporary load is applied based on the output signal of this reverse flow detector, the reverse 71 flow is eliminated due to the sudden increase in load. After this, the generated power is narrowed down by adjusting the generator's governor, and the reverse power flow detector is set to the opposite direction. By adjusting the power consumption of the temporary load so as to maintain the received power within a range in which the il flow is not detected, the power consumption of the - time load also decreases and finally reaches 0, completing the reverse power flow suppression operation. In this way, even if a reverse power flow occurs, the power amount and duration of the reverse power flow can be suppressed to a range where the reverse power relay does not operate, so there is no disconnection, and therefore, private power generation due to disconnection is possible. This has the effect that the voltage and frequency will not become unstable during maintenance.

[Brief explanation of the drawing]

Fig. 1 is a single line diagram of electrical equipment showing an embodiment of the present invention, Fig. 2 is a waveform diagram to explain the operation when reverse power flow occurs, and Fig. 3 is a diagram showing another embodiment of the invention. FIG. 4 is a single-line diagram of electrical equipment showing a conventional example. l... Power system, 2... Breaker, 31.43... Instrument current transformer, 32... Instrument transformer, 4... Distribution line, 42... Load, 34. 41.6
DESCRIPTION OF SYMBOLS 1... Wattmeter, 5... Generator, 51... Governor controller, 52... Power regulator, 53... Subtractor, 54
．． 71...Power setting device, 6.60...-hour load, 6
2... Transformer, 63... Thyristor converter, 64.
66...Resistor, 65...Load switch, 67, 68
...Contact, 7...Reverse power flow detector, 72...Subtractor, 73, 76...Reverse power flow calculation Wsiff device, 74.
...Pulse generator.

Claims (1)

[Claims] 1) In electrical equipment that receives power from the power grid and generates electricity from a private generator, there is a wattmeter that measures the received power, and reverse power flow detection that detects whether the value measured by this wattmeter is below a set value. 1. A reverse power flow suppressing device comprising a temporary load whose power consumption can be adjusted by being temporarily turned on based on the output signal of the reverse power flow detector.