JP2007252127A - Independent operation detection device for synchronous generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the deterioration of power quality in system linkage and also prevent an influence from being exerted upon the other control device or the like by enabling independent operation detection without constantly imparting the micro variation of a certain cycle to a voltage set value of an automatic voltage adjusting circuit of a synchronous generator, and to exactly detect the independent operation of the synchronous generator in the system linkage at the side of a private generating set. <P>SOLUTION: The independent operation detection device 1 comprises: a frequency detector 11 that detects a machine rotation frequency of the synchronous generator; a frequency variation amount operation part 12 that extracts a frequency error signal from the machine rotation frequency; a phase adjustment part 13 that oscillates a component of a specified natural frequency; a frequency relay 14 that detects that the frequency error signal has reached a prescribed value or higher; a proportional gain 15 that determines a code (positive/negative) and the magnitude of a control signal to be output; an output limiter 16 that limits the magnitude of the control signal; and a timer 17 that measures a time elapsed from a state that the frequency error signal has reached the prescribed value or higher. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an isolated operation detection device for a synchronous generator that detects the isolated operation of a synchronous generator linked to the system and disconnects the synchronous generator from the system.

Conventionally, a synchronous generator isolated operation detection device has been used to prevent the distributed power supply from operating independently when the distributed power supply is connected to a high voltage distribution system under conditions of reverse power flow. .
As an isolated operation detecting device for a synchronous generator currently developed, there is a reactive power fluctuation method as disclosed in Patent Document 1, for example. That is, this reactive power fluctuation type isolated operation detection device uses a minute fluctuation amount generator to generate a small fluctuation (AVR voltage setting value fluctuation) with respect to the voltage setting value of the automatic voltage regulator circuit (AVR) of the synchronous generator. (Quantity) is always given. With this configuration, a slight voltage fluctuation may occur in the synchronous generator, but the frequency change is suppressed by the synchronization force in the interconnection state with the system. However, when the synchronous generator shifts to a single operation, periodic fluctuations occur in the terminal voltage and frequency of the synchronous generator. Therefore, the frequency fluctuation amount calculation unit is configured to detect the frequency fluctuation amount Δf by digital calculation or the like based on the interconnection point voltage detected by PT, and the fact that the frequency fluctuation amount Δf exceeds a predetermined constant value. When the determination unit makes a determination, it is determined that the synchronous generator has shifted to a single operation. By this determination, a trip command for the circuit breaker is generated and the synchronous generator is disconnected from the system.

As another example of the synchronous generator isolated operation detection device, there is a QC mode frequency shift method disclosed in Patent Document 2, for example. That is, the QC mode frequency shift type isolated operation detection device detects the rate of change of the frequency of the synchronous generator, and when the frequency change rate is positive, the voltage of the synchronous generator is changed in the downward direction to change the frequency. When the rate is negative, the voltage fluctuation signal is given to the voltage setting value of the automatic voltage regulator circuit (AVR) so that the voltage of the synchronous generator is changed in the upward direction. By configuring in this way, this synchronous generator acts to constantly promote frequency fluctuations, but frequency changes are suppressed by the synchronization force in the interconnected state with the system. However, when this synchronous generator shifts to a single operation, the frequency fluctuation is expanded. Therefore, the frequency fluctuation amount calculation unit is configured to detect the frequency fluctuation amount Δf by digital calculation or the like based on the interconnection point voltage detected by PT, and the fact that the frequency fluctuation amount Δf exceeds a predetermined constant value. When the determination unit makes a determination, it is determined that the synchronous generator has shifted to a single operation. By this determination, a trip command for the circuit breaker is generated and the synchronous generator is disconnected from the system.
JP 11-41820 A JP 2002-281684 A

  However, in the conventional synchronous generator isolated operation detection device disclosed in Patent Document 1 described in the background art above, in order to detect the isolated operation in a short time, the AVR voltage set value fluctuation amount is increased. Although it is well known that, it is well known, however, the fluctuation amount of the AVR voltage setting value also increases the voltage fluctuation at the time of grid connection, resulting in a decrease in power quality and to other control devices. There was a problem that there is a risk of affecting.

  This problem becomes even greater when the generator capacity is large or when the synchronous generator is connected far away from the distribution substation. That is, in such a case, the voltage fluctuation amount at the time of grid connection may exceed the allowable value with respect to the AVR voltage set value fluctuation amount determined so as to satisfy the required isolated operation detection time. is there.

  On the other hand, the conventional synchronous generator isolated operation detection device disclosed in Patent Document 2 does not apply constant fluctuations such as the AVR voltage set value fluctuation amount in Patent Document 1; There is no voltage fluctuation. However, since the synchronous generator isolated operation detection device in Patent Document 2 acts so as to always promote frequency fluctuations, not only frequency fluctuations that occur when isolated operations occur, but also frequency disturbances in the grid interconnection (always on the system frequency). Fluctuation, insertion / release of power factor capacitors, parallel / disconnection of other power generation facilities, etc.), and reduce the stability of synchronous generators. In particular, there is a problem that there is a possibility that the stable operation of the synchronous generator may be hindered when connecting to a long and long electric wire.

  The present invention has been made in view of the above-described conventional problems, and a minute fluctuation (AVR voltage set value fluctuation amount) with a constant period with respect to the voltage set value of the automatic voltage regulator circuit (AVR) of the synchronous generator. It is possible to detect isolated operation without constantly giving power, preventing deterioration of power quality during grid connection, impact on other control devices, etc., and isolated operation detection without promoting frequency disturbance in grid connection. As possible, for the synchronous generator that prevents the stability of the synchronous generator in the grid connection from being lowered and can detect and protect the independent operation of the synchronous generator in the grid connection on the private power generation equipment side. The object is to provide an isolated operation detection device.

  In order to solve the above problems, a synchronous generator isolated operation detection device according to the present invention is a synchronous generator isolated operation detection device installed together with a synchronous generator linked to a system power supply via a circuit breaker. A frequency detecting means for detecting a mechanical rotation frequency or a terminal voltage frequency of the synchronous generator; a frequency variation calculating means for extracting a frequency deviation signal from the frequency signal detected by the frequency detector; Phase adjustment means for outputting as a control signal the phase of the frequency deviation signal adjusted so as to oscillate the maximum sensitivity frequency that is the oscillation frequency component unique to the synchronous generator, and the sign and magnitude of the control signal. A control amount adjusting unit for adjusting, a control signal limiting unit for limiting the magnitude of a control signal output from the control amount adjusting unit, and the control signal limiting unit. Means for adding the output control signal as a correction signal to the voltage command value of the automatic voltage adjustment circuit of the synchronous generator, and the synchronous generator is operated independently when the frequency fluctuation amount at the interconnection point exceeds the set value And an independent operation detecting device for a synchronous generator.

  In the synchronous generator isolated operation detection device, the highest sensitivity frequency is such that M is a generator inertia constant [s], Δgov is a governor settling rate [%], and TM is a prime mover time constant [s]. (1).

  As described above, according to the synchronous generator isolated operation detection device of the present invention, the environment where both the active power and reactive power flowing out to the system are near zero, that is, the isolated operation detection is the most difficult. Even under conditions, synchronous generators can be detected reliably in a short time, and unnecessary reactive power fluctuations (voltage fluctuations) do not occur during grid connection. Synchronous generator in the grid connection because it prevents the deterioration of the power quality in the system, does not have a cascading adverse effect on other control devices, and does not promote the frequency disturbance in the grid connection There is an effect that it is possible to provide a synchronous generator isolated operation detection device in which the stability of the generator does not decrease.

BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out an independent operation detection device for a synchronous generator according to the present invention will be described in detail below with reference to the drawings.
FIG. 1 is a configuration diagram showing an overall configuration of a power supply system including an isolated operation detection device for a synchronous generator according to an embodiment of the present invention.

  The power system shown in FIG. 1 extends to an infinite power source, a host system, a distribution substation, an open circuit breaker, and a special high-voltage wire to a distributed power facility. In addition to the synchronous generator that is a component, an isolated operation detection device 1 that is an isolated operation detection device for a synchronous generator according to an embodiment of the present invention is installed.

  The isolated operation detection device 1 extracts a frequency deviation signal from the frequency detector 11 (frequency detection means) that detects the mechanical rotation frequency (or terminal voltage frequency) of the synchronous generator and the mechanical rotation frequency (or terminal voltage frequency). The frequency fluctuation amount calculation unit 12 (frequency fluctuation amount calculation unit), the phase adjustment unit 13 (phase adjustment unit) that oscillates a specific natural frequency (maximum sensitivity frequency described later) component, and the frequency deviation signal become a predetermined value or more. A frequency relay 14 (determination means) for detecting this, a proportional gain 15 (control amount adjustment means) for determining the sign (positive / negative) and magnitude of the output control signal, and an output for limiting the magnitude of the control signal. And a limiter 16 (control signal limiting means) and a timer 17 (determination means) that measures the elapsed time when the frequency deviation signal is equal to or greater than a predetermined value. .

Hereinafter, the operation of each component of the isolated operation detection device 1 will be described with reference to FIG.
The frequency detector 11 detects the mechanical rotation frequency f of the synchronous generator (or the terminal voltage frequency of the synchronous generator).

The frequency variation calculation unit 12 extracts a frequency deviation signal Δf from the machine rotation frequency f (or the terminal voltage frequency of the synchronous generator).
The phase adjustment unit 13 receives the frequency deviation signal Δf from the frequency variation calculation unit 12 and is adjusted so as to oscillate a specific natural frequency (maximum sensitivity frequency described later) component, and includes a proportional gain 15 and an output limiter. 16 is used to generate a control signal from the frequency deviation signal Δf.

  The frequency relay 14 detects that the frequency deviation signal Δf has exceeded a predetermined set value (note that the frequency relay 14 uses the frequency f from the frequency detector 11 as an input signal, from which the frequency fluctuation rate df / dt It is also possible to determine that the frequency variation rate df / dt exceeds a predetermined set value).

The proportional gain 15 adjusts the sign (positive / negative) and magnitude of the control signal and transmits it to the output limiter 16.
The output limiter 16 limits the magnitude of the control signal.

  The control signal output from the isolated operation detection device 1 is added to the voltage command value of the automatic voltage regulator circuit (AVR) of the synchronous generator. With this configuration, a specific natural frequency (maximum sensitivity frequency described later) component of the control signal is positively fed back between the synchronous generator and the independent operation detection device 1.

  The timer 17 measures the elapsed time when the frequency deviation signal Δf reaches a predetermined value or more, and outputs an isolated operation detection breaker trip signal when the elapsed time reaches a predetermined set time or longer (note that The timer 17 can also be configured to detect and determine isolated operation based on the frequency variation rate df / dt).

This isolated operation detection breaker trip signal has a function of tripping a breaker intervening in the output system of the synchronous generator to open the electric circuit.
FIG. 2 is a control block diagram showing operating characteristics as an example of the synchronous generator isolated operation detection device according to the embodiment of the present invention.

Hereinafter, with reference to FIG. 2, the operation characteristics of the synchronous generator isolated operation detection device according to the embodiment of the present invention will be described.
The frequency f at the time of the transition to the isolated operation vibrates at a specific frequency (hereinafter, this frequency is referred to as “maximum sensitivity frequency”).

  When M is the generator inertia constant [s], Δgov is the governor adjustment rate [%], and TM is the prime mover time constant [s], the maximum sensitivity frequency fs [Hz] can be expressed by the equation (1).

  When the synchronous generator shifts to single operation in a state where the load within the range of the single operation and the output of the synchronous generator are almost balanced, the voltage v and frequency f at the interconnection point hardly change. Then, the frequency relay 14 cannot detect the shift to the single operation, and thus the single operation continues.

  However, here, the isolated operation detection device 1 detects the initial vibration of the slightest sensitivity frequency generated at the time of transition to the isolated operation by the frequency detector 11 and converts it into a control signal by the above components, and the synchronous power generation By performing positive feedback with the generator, it is possible to obtain an amplification effect and reliably detect a single operation of the generator.

  In addition, input signals in frequency bands other than the highest sensitivity frequency are not positively fed back, so frequency fluctuations during grid connection (always fluctuations in the system frequency, insertion / release of power factor improvement capacitors, parallel / solution of other power generation equipment, etc.) Column, etc.), therefore, no excessive fluctuation of reactive power (or voltage) in the interconnection is generated, no frequency disturbance in the grid interconnection is promoted, It is possible to realize a synchronous generator isolated operation detection device in which the stability of the synchronous generator is not lowered.

FIG. 3 is a block diagram showing a linear operating characteristic as an example of the case where the synchronous generator is shifted to a single system in the power supply system shown in FIG. 1 (open circuit breaker opened).
However, the synchronous generator adopts a transient model that ignores the effects of braking windings, armature resistance, armature flux linkage differentiation, and saturation, and uses non-linear elements such as frequency relays, circuit breakers, limiters, etc. Is ignored.

  M is an inertia constant, D is an intrinsic braking torque coefficient, T'do is a d-axis open circuit transient time constant, Wω (s) is a block of the independent operation detection device 1, and GA (s) is an AVR block (including an exciter). ), GGov (s) is a governor block, Δω is angular frequency variation, ΔVt is terminal voltage variation, ΔVref is voltage set value variation, ΔEfd is field voltage variation, Δe′q is internal voltage variation, ΔTe is electric torque variation, ΔTm represents a mechanical torque fluctuation, and s represents a Laplace operator (the angular frequency ω shown in FIG. 3 may be regarded as equivalent to the frequency f).

  In addition, K2, K3, and K6 shown in FIG. 3 are synchronous machine characteristic constants, respectively, and are obtained by equations (2) to (7).

id0: Armature current d-axis component
iq0: Armature current q-axis component
ed0: Terminal voltage d-axis component
eq0: Terminal voltage q-axis component
xd: d-axis synchronous reactance
xd ': d-axis transient reactance
xq: q-axis synchronous reactance
Eqo ': Voltage proportional to the d-axis flux linkage number Here, when Rl and Xl are impedances of the load, equations (5) to (7) are obtained.

  Now, in FIG. 3, the transfer function Gω (s) from Δω to ΔTe via the isolated operation detection device 1 having the power system stabilization function can be expressed by the equations (8) and (9). Wω (s) is a transfer function (compensation function) of the isolated operation detection device 1, and GR (s) is a transfer function (compensated function) of a field circuit including the AVR control system.

FIG. 4 is a block diagram showing transfer function characteristics as an example of the case where the synchronous generator is shifted to a single system in the power supply system shown in FIG. 1 (open circuit breaker opened).
This figure shows a transfer function block Gω (s) from Δω to ΔTe via the isolated operation detection device 1, and the highest target in the transfer function from Δω to ΔTe via the isolated operation detection device 1. The control block constant of the phase adjustment unit 13 of the isolated operation detection device 1 is adjusted so that the phase of the sensitivity frequency fs [Hz] is 180 [deg] (or -180 [deg]). The proportional gain value of the proportional gain 15 and the limiter value of the output limiter unit 16 are set in consideration of the control effect at the maximum sensitivity frequency fs and the influence on other frequency regions.

  According to this embodiment, the isolated operation detection device 1 gives a negative braking torque with respect to the maximum sensitivity frequency fs, and the power fluctuation of the maximum sensitivity frequency fs [Hz] generated in the synchronous generator at the time of transition to the isolated operation. On the other hand, it is possible to detect an isolated operation by realizing a positive feedback transfer function that increases (oscillates) only the natural frequency fluctuation (maximum sensitivity frequency) component.

FIG. 5 is a graph showing a frequency waveform at the time of transition to an independent operation when the synchronous generator isolated operation detection device is disabled in the power supply system shown in FIG. 1.
In the configuration of the power supply system including the synchronous generator isolated operation detection device (independent operation detection device 1) according to the embodiment of the present invention shown in FIG. 1, the load is adjusted so that the open-circuit power flow is substantially zero. In addition, when the breaker at the open point was opened without any accident, the frequency waveform shown in the graph of FIG. 5 was obtained as a result.

FIG. 6 is a graph showing the frequency waveform at the time of transition to the isolated operation when the synchronous generator isolated operation detection device is effective in the power supply system shown in FIG. 1.
In the configuration of the power supply system including the synchronous generator isolated operation detection device (independent operation detection device 1) according to the embodiment of the present invention shown in FIG. From the frequency waveform (FIG. 6), in the waveform shown in FIG. 5, the frequency after the transition to isolated operation has converged with a minute change that cannot be detected in isolated operation, whereas in the frequency waveform shown in FIG. The frequency change after the transition increases, indicating that the vibration of the highest sensitivity frequency fs after the transition to the single operation is effectively positively fed back by the single operation detection device 1. From this, it can be seen that the isolated operation detection device for a synchronous generator according to the present embodiment can reliably detect the isolated operation in a short time.

It is a block diagram which shows the whole structure of the power supply system containing the independent operation detection apparatus for synchronous generators concerning embodiment of this invention. The control block diagram which shows the operation characteristic as an example of the independent operation detection apparatus for synchronous generators concerning embodiment of this invention is shown. In the power supply system shown in FIG. 1, the block diagram showing the linear operation characteristic as an example when a synchronous generator transfers to a single system (open-circuit breaker open) is shown. In the power supply system shown in FIG. 1, the block diagram showing the transfer function characteristic as an example when a synchronous generator transfers to a single system (open-circuit breaker open) is shown. 2 is a graph showing frequency waveforms at the time of transition to an isolated operation when the synchronous generator isolated operation detection device is disabled in the power supply system shown in FIG. 1. 2 is a graph showing a frequency waveform at the time of transition to isolated operation when the synchronous generator isolated operation detection device is valid in the power supply system shown in FIG. 1.

Explanation of symbols

1 Single operation detection device (single operation detection device for synchronous generator of the present invention)
DESCRIPTION OF SYMBOLS 11 Frequency detector 12 Frequency variation calculation part 13 Transfer adjustment part 14 Frequency relay 15 Proportional gain 16 Output limiter 17 Timer

Claims (2)

In the synchronous generator isolated operation detection device installed together with the synchronous generator connected to the system power supply via the circuit breaker,
A frequency detection means for detecting a mechanical rotation frequency or a terminal voltage frequency of the synchronous generator;
A frequency variation calculating means for extracting a frequency deviation signal from the frequency signal detected by the frequency detector;
Phase adjustment means for outputting as a control signal what the phase of the frequency deviation signal is adjusted so as to oscillate the highest sensitivity frequency that is the oscillation frequency component unique to the synchronous generator that occurs at the time of transition to isolated operation;
Control amount adjusting means for adjusting the sign and magnitude of the control signal;
Control signal limiting means for limiting the magnitude of the control signal output from the control amount adjusting means;
Means for adding the control signal output from the control signal limiting means as a correction signal to the voltage command value of the automatic voltage regulator circuit of the synchronous generator;
Means for determining as an independent operation of the synchronous generator when the frequency fluctuation amount of the interconnection point exceeds a settling value;
An independent operation detection device for a synchronous generator, comprising: The maximum sensitivity frequency is expressed by equation (1) when M is a generator inertia constant [s], Δgov is a governor adjustment rate [%], and TM is a prime mover time constant [s]. The independent operation detection device for a synchronous generator according to claim 1.