JP2005073473A - Power system stabilizer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power system stabilizer that is quickly returned to a constant state without being influenced by noise and without causing an interference when returned to an operation point of a linear region. <P>SOLUTION: A synchronous generator 1 connected to a system 3 is controlled to a set value in a terminal voltage by a voltage control signal of an automatic voltage control unit 11. A non-linear compensation signal obtained by the operation of the power stabilizer 9 is added to the voltage control signal of the automatic voltage control unit 11 by a dead zone device 10. A magnetic field current of the synchronous generator 1 is controlled by a compensation voltage control signal obtained by adding the non-linear compensation signal to the voltage control signal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power system stabilization device that performs field control of a synchronous generator to stabilize a power system.

Japanese Patent Laid-Open No. 8-163782

  In general, the transmission line of the power grid is not the limit that can stably transmit power (stable power transmission limit), but to transmit power that is much smaller than the stable power transmission limit in order to transmit power stably even in the event of a power line accident due to lightning strikes, etc. Yes. As the power demand increases, it is required to increase the transmission power of the transmission line to near the stable transmission limit. For this purpose, it is necessary to increase the stability of the power system in the event of a transmission line accident.

  A power system stabilizer (PSS: Power System Stabilizer) that performs field control of a synchronous generator is linearized around a predetermined operating point so as to operate stably. The power at the operating point is set to a power much smaller than the stable transmission limit. However, when the transmission capacity is increased to a point close to the stable power transmission limit, the operating point shifts to an operating point with strong nonlinearity. For this reason, a sufficient control effect cannot be obtained when the power flow of the system changes or an accident occurs only by linearizing the power stabilizer.

  In order to solve this problem, it has been proposed to add a nonlinear compensation signal to the output signal of the linearly designed power stabilizer. This is described in Patent Document 1 described above.

  The non-linear calculation for obtaining the non-linear compensation signal uses a differential value of the power state quantity such as voltage, current and frequency. For this reason, it is affected by noise. If a filter is used as a noise countermeasure, the control gain cannot be increased, so there is a problem that when the operating point is stabilized and returned to the linear region, it vibrates by interference or a delay occurs in the steady state. .

  An object of the present invention is to provide a power system stabilizing device that can quickly enter a steady state without interference when it returns to an operating point in a linear region without being affected by noise.

  A feature of the present invention is that the nonlinear compensation signal obtained by calculation in the power stabilizing device is added to the voltage control signal of the automatic voltage control device via the dead zone means, and the nonlinear compensation signal is added to the voltage control signal. This is because the field current of the synchronous generator is controlled by the added compensation voltage control signal.

  In the present invention, the non-linear compensation signal is added to the voltage control signal of the automatic voltage control device through the dead zone means. Since the noise is masked by the dead zone by providing the dead zone, the control gain of the nonlinear calculation can be increased, so that the response can be speeded up. Further, when the operating point approaches the steady state and the nonlinear compensation signal becomes small, it is masked by the dead zone, so that the steady state can be quickly achieved without vibration.

  According to the present invention, the control gain can be increased, so that the response can be speeded up and at the same time the steady state can be quickly achieved without interference when the operating point returns to the linear region.

  The synchronous generator connected to the system controls the field current by a thyristor converter. The thyristor converter converts the AC output voltage of the synchronous generator into a DC voltage and supplies it as a field current. The automatic voltage control device outputs a voltage control signal for controlling the terminal voltage of the synchronous generator to a set value. The power stabilizing device inputs a power state quantity of the system and obtains a nonlinear compensation signal by a calculation including a differential calculation. The nonlinear compensation signal is added to the voltage control signal via the dead zone means. The phase control means inputs a firing phase control signal obtained by adding a non-linear compensation signal to the voltage control signal, and performs firing control of the thyristor converter.

  FIG. 1 shows an embodiment of the present invention.

  In FIG. 1, a synchronous generator 1 is connected to a power system 3 via a circuit breaker 2. Usually, a transformer is provided between the circuit breaker 2 and the system 3, but the illustration is omitted. The output voltage (terminal voltage) of the synchronous generator 1 is input to the thyristor converter 4 via the transformer 5 and converted into a DC voltage. The field winding 1 </ b> F of the synchronous generator 1 is controlled by the thyristor converter 4. The synchronous generator 1 is self-excited.

  The terminal voltage of the synchronous generator 1 detected by the transformer 6 is input to a frequency detection device (F detection) 8, a power stabilization device (PSS) 9, and an automatic voltage control device (AVR) 11. The frequency detection device 8 detects the frequency of the power system 3 and adds it to the power stabilization device 9. The current detected by the current transformer 7 is also input to the power stabilizing device 9. The power stabilizing device 9 receives the power state quantities of the generator voltage V, current I and frequency F. The power stabilizing device 9 obtains a nonlinear compensation signal from the calculation 2 based on the power state quantity and adds it to the adding device 12 via the dead zone device 10.

  The automatic voltage control device 11 compares the input terminal voltage with the set value, and adds a voltage control signal for setting the terminal voltage to the set value to the adding device 12. The voltage control signal and the nonlinear compensation signal added by the adder 12 are added to the phase controller (APPS) 13 as a compensation voltage control signal. The compensation voltage control signal is an ignition phase control signal. The phase controller 13 controls the thyristor converter 4 based on the ignition phase control signal to adjust the field current applied to the field winding 1F.

  FIG. 2 shows an example configuration diagram of the power stabilizing device 9.

  In FIG. 2, the power state quantity of the generator voltage V, current I, and frequency F input to the input unit 21 is led to the state quantity calculation unit 22. The state quantity calculation unit 22 calculates an internal phase difference angle (phase difference with the system 3) δ, a voltage change amount ΔV, and the like of the generator 1 based on the power state quantity. The state quantity calculated by the state quantity calculation unit 22 is input to the differential calculation unit 23 and input to the coordinate conversion unit 24 to be linearized. The differential calculation unit 23 is used to set the compensation amount to an optimum value.

  The state quantity linearized by the coordinate conversion unit 24 is input to the operation amount calculation unit 25 to obtain the operation amount. The manipulated variable obtained by the manipulated variable calculator 25 is a linear compensation signal. The manipulated variable (linear compensation signal) obtained by the manipulated variable calculator 25 is coordinate-transformed by the coordinate converter 26 and converted into a nonlinear compensation signal. The nonlinear compensation signal obtained by the coordinate conversion unit 26 is output to the dead zone device 10 via the output unit 27.

  Next, the operation will be described.

  The automatic voltage control device 11 compares the terminal voltage of the synchronous generator 1 detected by the transformer 6 with the set value, outputs a voltage control signal for setting the terminal voltage to the set value, and applies it to the adder 12. In addition, the power stabilizing device 9 receives the power state quantities of the generator voltage V, current I, and frequency F. The power stabilizing device 9 receives the generator voltage V, current I and frequency F and obtains a nonlinear compensation signal by calculation. Nonlinear control operations are described in detail in, for example, the literature “Konishi et. Al.,“ Confirmation Test for Nonlinear Excitation Control System Using State-Space Linearization ”, IECON2002, Nov. 5-8, Sevilla, Spain”. Also, since it is not directly related to the gist of the present invention, an outline will be described.

  The power stabilization device 9 strictly linearizes the system 3 to which the generator 1 is connected in the state space, and formulates, for example, an evaluation function that attenuates vibration during power oscillation in the shortest time. Then, the input gain that minimizes the evaluation function is obtained by the Riccati equation.

  A variable vector Y expressed by Equation 1 is obtained from the coordinate conversion unit 24 of the power stabilizing device 9.

Y = A · Y + B · U (Formula 1)
Y: State variable
A, B: coefficient matrix
U: Input vector The manipulated variable calculator 25 receives the variable vector Y of Equation 1 and computes the linear manipulated variable u using the Riccati equation.

u = C · Y (Formula 2)
C: Gain constant The linear manipulated variable u obtained by the manipulated variable calculator 25 is coordinate transformed by the coordinate converter 26 and converted into a nonlinear compensation signal (nonlinear manipulated variable) and output from the output unit 27. The nonlinear compensation signal output from the power stabilizing device 9 is applied to the adding device 12 via the dead zone device 10. The voltage control signal and the nonlinear compensation signal added by the adder 12 are added to the phase controller 13 as a compensation voltage control signal. The compensation voltage control signal is an ignition phase control signal. The phase controller 13 controls the thyristor converter 4 based on the ignition phase control signal to adjust the field current applied to the field winding 1F. The synchronous generator 1 generates an electrical output corresponding to the magnitude of the field current and stabilizes the system 3.

  In this way, the power system is stabilized. Nonlinear control will be described with reference to FIG. 3 in order to facilitate understanding of the effect.

  FIG. 3 shows the phase angle δ of the synchronous generator on the horizontal axis and the generator output P on the vertical axis. The generator output P is expressed by Equation 3 where X is the reactance of the transmission line, Vg is the generator output voltage, Vr is the voltage at the load end, and δ is the phase difference between the voltages Vg and Vr.

P = Vg ・ Vr ・ sinδ / X (Formula 3)
Now, it is assumed that the generator is constantly operating at point a (phase angle δo). Conventionally, field control is linearized at point a, that is, linearly approximated as shown by characteristic b to determine the optimum field control circuit constant (fast response and stable). However, if the phase angle δ at the operating point of the generator increases due to a grid fault or an increase in the power line power flow, the error α between the operating point obtained from the linear approximation of point a and the actual operating point increases. For this reason, not only the control response and the control performance deteriorate, but also the system becomes unstable in some cases. In particular, it becomes unstable when it is necessary to operate in the vicinity of the stable power transmission limit in order to make effective use of existing facilities. The stable power transmission limit is about several percent smaller than the maximum value of the generator output P.

  Since non-linear control does not perform linear approximation, no control error occurs even if the operating point of the generator moves on the sine wave of the generator output P, and the control does not become unstable. However, since non-linear control uses differential values of state quantities such as voltage, current, angular velocity, etc., it becomes susceptible to noise and adversely affects control characteristics. For this reason, the gain cannot be increased, and the operation in the linear region becomes worse compared to the linear control.

  In the present invention, the nonlinear compensation signal obtained by calculation in the power stabilizing device 9 is added to the voltage control signal of the automatic voltage control device 11 through the dead zone device 10. In the normal steady state, the nonlinear compensation signal is smaller than the dead band width, linear and fast, and the control operation with good control performance can be performed.

  On the other hand, when the operating point moves to a region with strong nonlinearity due to a heavy current or a system fault, the nonlinear compensation signal becomes larger than the dead band width, and the voltage control signal of the automatic voltage controller 11 is corrected to control stability and response. Will be raised. Also, when the operating point returns to a steady state, the response becomes slow because the nonlinear compensation signal becomes small. When the nonlinear compensation signal becomes smaller than the dead zone width, the nonlinear compensation signal is masked by the dead zone, so that linear control is performed. In addition, the dead zone prevents the influence of noise that is normally associated with nonlinear control.

  As described above, according to the present invention, the nonlinear compensation signal is added to the voltage control signal of the automatic voltage control device through the dead zone means. Since the noise is masked by the dead zone by providing the dead zone, the control gain of the nonlinear calculation can be increased, so that the response can be speeded up. Further, when the operating point approaches the steady state and the nonlinear compensation signal becomes small, it is masked by the dead zone, so that the steady state can be quickly achieved without vibration.

  Therefore, since the control gain can be increased, the response can be speeded up, and the steady state can be quickly obtained without interference when returning to the operating point in the linear region.

It is a block diagram which shows one Example of this invention. It is an example detailed block diagram of the electric power stabilization apparatus of this invention. It is a characteristic view for demonstrating this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Synchronous generator, 1F ... Field winding, 2 ... Circuit breaker, 3 ... Electric power system, 4 ... Thyristor converter, 5 ... Transformer, 6 ... Transformer, 7 ... Current transformer, 8 ... Frequency detection apparatus , 9 ... Power stabilization device, 10 ... Dead band device, 11 ... Automatic voltage control device, 12 ... Addition device, 13 ... Phase control device, 21 ... Input unit, 22 ... State quantity calculation unit, 23 ... Differential operation unit, 24 ... coordinate conversion unit (linear), 25 ... manipulated variable calculation unit, 26 ... coordinate conversion unit (non-linear), 27 ... output unit.

Claims (4)

  A synchronous generator connected to the system, an automatic voltage control device that outputs a voltage control signal that controls the terminal voltage of the synchronous generator to a set value, and a power stabilization that obtains a nonlinear compensation signal that stabilizes the system by calculation And a dead band means for inputting the nonlinear compensation signal and adding it to the voltage control signal, and receiving a compensation voltage control signal obtained by adding the nonlinear compensation signal to the voltage control signal. A power system stabilizing device comprising a field control means for controlling current.   A synchronous generator connected to the system, an automatic voltage control device that outputs a voltage control signal that controls the terminal voltage of the synchronous generator to a set value, and a nonlinear compensation signal that suppresses power fluctuations of the system are obtained by calculation. A power stabilization device; dead zone means for inputting the nonlinear compensation signal and adding it to the voltage control signal; and a compensation voltage control signal obtained by adding the nonlinear compensation signal to the voltage control signal. A power system stabilizing device comprising field control means for controlling a field current.   A synchronous generator connected to the grid, a thyristor converter for controlling the field current of the synchronous generator, and an automatic voltage control device for outputting a voltage control signal for controlling the terminal voltage of the synchronous generator to a set value; A power stabilizing device that obtains a nonlinear compensation signal by calculation based on a power state quantity of the system, dead band means for inputting the nonlinear compensation signal and adding it to the voltage control signal, and the nonlinear compensation signal in the voltage control signal And a field control means for controlling the field current of the synchronous generator by inputting a compensation voltage control signal obtained by adding the power to the power system stabilizing device. A synchronous generator connected to the grid, a thyristor converter that converts the AC output voltage of the synchronous generator into a DC voltage and controls the field current of the synchronous generator, and a terminal voltage of the synchronous generator as a set value An automatic voltage control device that outputs a voltage control signal to be controlled, a power stabilization device that inputs a power state quantity of the system and obtains a nonlinear compensation signal by an operation including a differential operation, and an input of the nonlinear compensation signal A dead zone means for adding to the voltage control signal; and a phase control means for controlling the thyristor converter by inputting an ignition phase control signal obtained by adding the nonlinear compensation signal to the voltage control signal. A power system stabilizing device characterized by:

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