JPH0458799A - Exciter for synchronous machine - Google Patents

Abstract

PURPOSE:To make a contribution to the stability of power system by providing a system stabilizing unit with first and second power detecting circuits, an adder, first and second phase compensating circuits and a signal amplifying circuit thereby controlling the exciting amount of a field winding with the exciting power as one component of a stabilizing signal. CONSTITUTION:A power detecting circuit 10b receives an exciting current detected through an instrument current transformer CT2b disposed on the primary of an exciting power supplt transformer 7 and a terminal voltage detected through an instrument potential transformer PT3 and detects power flowing into the exciting power supply transformer 7. A power detecting circuit 10a receives current and voltage, respectively, from an instrument current transformer CT2a and instrument potential transformer PT3 and detects output current of a synchronous machine 1. An adder circuit 15 receives power signals from the power detecting circuits 10a, 10b and produces a differential signal which is then fed to a phase compensation circuit 11a. Furthermore, the power detection circuit 10b outputs a power signal to a phase compensation circuit 10b. A signal amplifying circuit 12a combines and amplifies outputs from the phase compensation circuits 11a, 11b and thus amplified output is fed, as a stabilizing signal, to an AVR 13.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides an excitation device for a synchronous machine for stabilizing a power system, which controls the excitation of a synchronous machine operated in parallel with the power system. Regarding.

(Prior Art) An excitation device for a synchronous machine is generally used in a synchronous generator, a synchronous motor, etc., and performs control to maintain the terminal voltage of the synchronous machine at a predetermined value. Even if an automatic voltage regulator (hereinafter referred to as AVR) is used to control the terminal voltage of a synchronous machine that is operated in parallel to the power grid to a constant level, there is no control over the electromechanical fluctuations of the power system, including the synchronous machine. Not much power can be obtained and the stability of the system will not be very good. Therefore, in recent years, as a measure to improve power system stability, a stabilization signal has been created based on the amount of power change such as the rotor speed of the synchronous machine, the frequency of the terminal voltage of the synchronous machine, and the input/output of the synchronous machine. A system stabilizing device (hereinafter referred to as PSS) is now being used, which improves the braking force against power system fluctuations by inputting a signal to the AVH.

FIG. 2 is a configuration diagram of a conventional synchronous machine exciter including an AVR and a PSS.

The synchronous machine 1 is connected to a power system 6 via a circuit breaker 4 and a main transformer 5, and when the circuit breaker 4 is closed, the output of the synchronous machine 1 is boosted by the main transformer 5 and supplied to the power system 6. Synchronous machine 1 fielder #! The voltage supplied from the output terminal of the synchronous machine 1 via the excitation power transformer 7 is controlled and rectified by the thyristor rectifier 8 and supplied to the synchronous machine 14, thereby controlling the output of the synchronous machine 1. Field winding 1 due to the output of this thyristor rectifier 8
The excitation amount of 4 is controlled by the AVR 13 based on the output signal from the PSS 9 using the terminal voltage signal detected from the instrument voltage transformer (hereinafter referred to as PT) 3 as the controlled signal.

Here, PSS9 includes power detection circuit 10a, phase compensation circuit 1.1. A power detection circuit 10a detects the output power Pe from the terminal voltage signal from the PT3 and the instrument current transformer (hereinafter referred to as CT) 2a, and stabilizes it in the phase compensation circuit 11a. The output signal is phase compensated as a signal and amplified by the signal amplification circuit 12, and is output to the AVR 13. As a result, when the terminal voltage of the synchronous machine 1 deviates from the reference value, the AVR 13 controls the thyristor rectifier 8 based on the output signal whose phase has been compensated by the PSS 9, and synchronizes by controlling the field current to the field winding 14. The terminal voltage of machine 1 can be maintained at the standard value, thereby stabilizing the system.

Even the complicated power system shown above is represented by a synchronous machine, one actance, and an infinite bus (-machine-to-infinite bus system), and its operation can be explained in a relatively simple block diagram. It is common to treat the operation of power systems using such methods.

The configuration of the power generation system shown in FIG. 2 is shown in FIG. 3 as a linearized stability block diagram in a -machine-to-infinite bus system so that the operation as a power system can be understood.

In Figure 3, variable P1 is the mechanical input of the prime mover, P
e is the electrical output of the synchronous machine, ω is the rotational speed of the synchronous machine (=frequency of the synchronous machine terminal voltage), δ is the phase difference (phase difference angle) between the d-axis of the synchronous machine and the infinite bus voltage, and et is Efd is the terminal voltage of the synchronous machine, Efd is the field voltage of the synchronous machine, eql is the transient d-axis voltage, and etref is the voltage setting value of the AVR.

This block diagram is linearized and is valid only for the amount of change from the steady value of the variable, so the symbol Δ, which means the amount of change, is attached to the variable. K1- and 6 are constants determined by the synchronous machine, system constants, and operating conditions.

M is the rotor inertia constant of the synchronous machine and prime mover, D is the machine-specific damping coefficient due to the damping winding of the synchronous machine, ω0 is the unit conversion coefficient, and S is the Laplace operator. Also, Gex
(s) is the transfer function of the exciter, and Idp(s) is P
SS transfer function whose input signal is the electrical output P of the synchronous machine
It is e.

The purpose of operation of the system stabilizing device 9 will be explained with reference to the block diagram of FIG. 3. It is to produce the same effect as when the unique braking coefficient is increased by excitation control.

To express it more concretely, the electrical output change △Pe is expressed as p
Through the ss function −ρ(s), input into the transfer function Gex(s) to correct the movement of △Efd, thus changing △ω to △Pe.
The goal is to generate more components that are in phase with .

(Problem to be Solved by the Invention) By the way, the power signal Pe detected by the power detection circuit 3A with the configuration shown in FIG.
It is the sum of the power Pex which is divided into two excitation power transformers and used as excitation power.

The movements caused by their excitation control are significantly different.

However, conventionally, when the synchronous machine is in a high output state where stability is a problem, the influence of the power Pex has been completely ignored because the power Pex is smaller than the power Pso. but,
Recent high-speed dynamic excitation devices designed to contribute to improved stability are capable of generating a field voltage several times higher than the field voltage required in a steady state. As a result, the transient change in excitation power Pex has become considerably large. For this reason, control that ignores the excitation power Pex is not preferable.

Below, we will examine the nature and magnitude of the excitation power Pex. Since the excitation power Pex is the product of the field current and the field voltage, the change from the steady state PeX can be expressed by the following equation.

△pax4Kex1X△eq'+Kex2X△Efd However, Kex and Kex2 are constants determined by the characteristics and operating conditions of the synchronous machine. The first term of this △Pex (hereinafter, △Pe
△Pe (= to 2X
To △eq' +, - component (K2+△eq'
), but the second term (hereinafter referred to as ΔPex2) is a response different from any component of ΔPe determined in FIG.

Using typical constants of recent steam turbine generators and assuming reactance Xe = 0.4 pu, the following is calculated as a constant of 1 to 6 in the rated operating state.

K1=1.46, K2=1.7, K3=0.29,
K, = 2.47, K, = -0,0234, K620
．． 37 Furthermore, the field time constant Tdo' of the generator is about 8 seconds. And Kex is about 0.0025.

Now, consider a situation where the amplitude of ΔPe is 0.01 pu and the oscillation frequency is 1t (z) where the system oscillation continues.

For vibrations of about IHz, the gain of the exciter is sufficiently high, so the field voltage △Efd is the sum of the maximum positive output voltage (referred to as the positive side peak voltage) and the maximum negative output voltage (referred to as the positive side peak voltage) of the exciter.
(referred to as negative peak voltage). Assuming that the maximum output voltage of the exciter is designed to be three times the rated operating state, the fluctuation width of △Efd is 10.8 pu (1,,8[Efd at rated time]X3X2[: positive and negative are assumed to be the same) ).

Even if △Efd fluctuates this much, the resulting △e q
The variation in I is approximately 0.0% due to the delay in the field time constant Tdo'.
It becomes 21ρU. Therefore, when such oscillation continues, the change in ΔPe due to excitation control (hereinafter, ΔPe1
) is ΔPe1 = 0.357pu (Δeq'
X K2 = 0.21 Xl, 7). On the other hand, Δ
Pex, = Kex2XΔEfd=0.0025X
10.8 = 0.027. Therefore, ΔPex
, is a signal whose phase is approximately 90 degrees ahead of ΔPe1.
Because of this phase difference, the ratio of 8Pex to ΔPe□ is 7.6%. The ideal phase compensation value to be input to the function Gex(s) is different between ΔPeX and ΔPex.

Although the above numerical example shows a case where the oscillation at the typical system oscillation frequency 111z continues, various natural oscillations exist in an actual complex power system in which many synchronous machines are connected in parallel. And for higher perturbation frequencies, ΔP
The ratio of ΔPex to e becomes even larger.

The ratio between ΔPe and ΔPex2 also changes depending on the operating state.

Therefore, the present invention provides an excitation device for a synchronous machine that contributes to stability on the power system by using the excitation power as a component of the stabilization signal of the system stabilization device and controlling the amount of excitation generated in the field winding. The purpose is to provide.

[Structure of the invention]

(Means for solving problems) An excitation device for a synchronous machine according to the present invention will be explained with reference to FIG.

The system stabilizing device 9a of the excitation device of the present invention includes first and second power detection circuits 10a and 10b, and an adder circuit 15.
, first and second phase compensation circuits 11a and 11b,
A signal amplification circuit 12a is provided. First power detection circuit 10
a obtains a terminal power signal from the terminal voltage and terminal current of the synchronous machine 1. The second power detection circuit 10b obtains an excitation power signal from the terminal voltage of the synchronous machine 1 and the current flowing through the excitation power supply transformer. The adder circuit 5 obtains deviation signals of the outputs of the first and second power detection circuits 10a and 10b. First and second phase compensation circuits 11a and llb
compensate the phase of the deviation signal from the adder circuit 15 and the excitation power signal from the second power detection circuit 1, Ob, respectively. Then, the signal amplification circuit 12a synthesizes and amplifies both or either one of the outputs of the first and second phase compensation circuits 11a and llb, and outputs it as a stabilizing signal.

(Function) Even if the ratio of excitation power consumed by the field winding 14 to the terminal power of the synchronous machine cannot be ignored during high-output operation of the synchronous machine, phase compensation is performed from the deviation signal between the terminal power signal and the excitation power signal. By using this signal as a stabilizing signal, the stability of the power system will be improved.

Since there is a large phase difference between the signal obtained by subtracting the excitation power from the synchronous machine output and the excitation power signal, by performing different phase compensation for each, a more ideal stabilization signal (the control result is a power in phase with Δω). (signal whose component can be increased) can be input to AVH. Therefore, it is possible to realize an excitation device that contributes more to system stability using an excitation device with the same capacity.

(Example) Embodiments of the present invention will be described below with reference to FIG.

FIG. 1 shows a configuration diagram of an excitation device for a synchronous machine according to an embodiment of the present invention. In FIG. 1, the same or equivalent parts as in FIGS. 2 and 3 are given the same reference numerals.

The system stabilizing device 9a of the embodiment of the present invention is a power detection circuit]
, Oa, 10b, addition circuit 15, phase compensation circuit 11a
.

11b and a signal amplification circuit 12.

The power detection circuit 10b inputs the excitation current detected by the CT2b provided on the primary side of the excitation power transformer 7 and the terminal voltage detected by the PT3, and outputs the excitation power transformer 7.
detect the power flowing into the

The power detection circuit 10a receives current and voltage from the CT2a and PT3, and detects the output current of the synchronous machine 1.

Then, the adder circuit 15 obtains a deviation signal from the power signals detected by the power detection circuit Joa and the power detection circuit Ob, and outputs it to the phase compensation circuit 11a. In addition, the power detection circuit 10
b converts the power signal into a phase compensation circuit +1. Output to b. The signal amplification circuit 12a synthesizes and amplifies the outputs of the phase compensation circuits 11a and Ilb, and outputs it to the AVR 13 as a stabilizing signal.

The characteristics required for the phase compensation circuit a, ]]b vary depending on the characteristics of the applied synchronous machine 1 and the magnitude of the exciter top voltage (ratio to the rated state), but are as cited in the explanation of the prior art described above. In the case of a generator and an excitation device top voltage of It shall be possible to set the delay.

Next, the operation of the excitation device for a synchronous machine which is an embodiment of the present invention shown above will be explained.

Power detection circuit 10b from the output signal of power detection circuit 10a
By configuring the polarity to subtract the output signal of the adder circuit 1,
5, a signal (referred to as Pso') obtained by subtracting the excitation power from the output power of the synchronous machine 1 is obtained. Then, by the phase compensation circuit dedicated to the signal Pso'], 1a,
Phase compensation suitable for this can be performed.

The output signal (referred to as Pex') of the power detection circuit 10b is excitation power supplied to the field winding 14 of the synchronous machine via the excitation power transformer 7. The phase compensation circuit 11b dedicated to the signal Pex can perform phase compensation suitable for it. As already explained, the components of the signal Pex' include
△Pex1 with different response phases to power system fluctuations.
ΔFez2 is included, but phase compensation is performed with emphasis placed on ΔPex2.

In this way, the signal Pso- and the signal Pex' are subjected to separate phase compensation and input to the AVR 13.

Therefore, since signals with different phases are subjected to separate and appropriate phase compensation to obtain a system stabilization signal, even if the ratio of two signals with different phases changes due to changes in operating conditions, each signal is maintained at an almost ideal level of stability. Since excitation control is performed as a signal, an excitation device that contributes to greater stability can be realized.

As explained above, in the embodiment of the present invention, the difference between the terminal power and the excitation power output from the synchronous machine 1 is determined by the adding circuit 15, but the difference is not limited to this and can be detected in various configurations.

For example, assume that the installation location of the instrument voltage transformer 3 is changed so that the current flowing through the excitation power transformer 7 is removed from the current input to the power detection circuit 10a. Alternatively, the instrument voltage transformer 3 can be installed in the same location.

The secondary current of the instrument current transformer 2b and the secondary current of the instrument voltage transformer are combined and then used as a current input to the power detection circuit 10b.

Detection of excitation power is also not limited to the embodiments described above, and can be implemented in various configurations.

For example, detection may be performed using the product of excitation voltage and electromagnetic current. Alternatively, it can be detected from the excitation current and excitation voltage on the secondary side of the excitation power transformer 7.

Further, in the above embodiment, completely separate phase compensation circuits are provided, but a configuration may be adopted in which they are partially shared. Alternatively, for one of the signals, a phase characteristic associated with a power detection circuit or the like may be used instead of providing a special phase compensation circuit.

Further, in the above embodiment, the difference between the terminal power and the excitation power output from the synchronous machine and the excitation power are used as stabilizing signals, but in addition to these, the terminal output from the synchronous machine It is clear that the system stabilization effect can be further improved by using a combination of signals other than electric power, such as the rotational speed of the synchronous machine and the frequency of the terminal voltage of the synchronous machine, and this can be achieved by applying the gist of the present invention. It is something.

Further, in the above embodiment, both the difference between the terminal power and the excitation power output from the synchronous machine and the excitation power are used as the stabilization signal, but depending on the characteristics of the synchronous machine, only one of them may be used. However, there are cases where it is more effective than using the terminal power output from a conventional synchronous machine.

An example of this is when high-speed excitation control is applied to a superconducting generator whose field winding is made of a superconductor.

In superconducting generators, the time constant of the field winding is extremely large;
In order to control the excitation current flowing through it at high speed, the excitation power in the steady state is very small (only the loss in the normal conduction part), but in the transient state, a very large excitation power is required. Therefore, the ratio of △Pex2, which is one component of the changing power △Pex of the excitation power Pex, to the 8-force power Pso becomes large, and the control of excitation generated in the field winding ignoring the △Pex2 increases the power system stability. Not good.

Furthermore, although the above description uses terms and configurations assuming that the synchronous machine is a synchronous generator, it is clear that the present invention can also be applied to an excitation device for a synchronous motor.

〔Effect of the invention〕

Therefore, according to the present invention, as a system stabilization signal for an excitation device that uses the terminal voltage of a synchronous machine as an excitation power source, a signal obtained by appropriately phase-compensating a signal obtained by subtracting the excitation power from the high power of the synchronous machine and the excitation power. By using a signal that has undergone appropriate phase compensation, each phase compensation can be performed more ideally, and a more ideal stabilization signal can be obtained, so the excitation device can greatly contribute to system stabilization. can be realized.

In addition, a more remarkable effect is produced especially in a combination of a synchronous machine and an excitation device that require a large transient excitation power.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an excitation device for a synchronous machine according to an embodiment of the present invention, and FIG. 2 is a configuration diagram showing an excitation device for a conventional synchronous machine.
FIG. 3 is a characteristic block diagram showing the operating functions of the excitation device of the synchronous machine. 1...Synchronous machine 2a, 2b...Instrument current transformer W (CT)3...
・Instrument voltage transformer (PT) 4... Breaker 5... Main transformer 6...
Power system 7...Excitation power transformer 8...
Thyristor rectifier 9.9a... System stabilizer (PSS) 10a, I (
lb...Power detection circuit 11a, ], ], b...Phase compensation circuit 12, 12a...Signal amplification circuit 13...Automatic voltage regulator (AVR) 14/field winding agent Patent attorney Kensuke Noriyuki

Claims (2)

[Claims] (1) An automatic voltage regulator that inputs the terminal voltage of the synchronous machine and a stabilization signal from the system stabilization device controls a thyristor rectifier to which the terminal voltage of the synchronous machine is inputted via the excitation power transformer. An excitation device for a synchronous machine that supplies excitation current to a field winding, comprising: a first power detection circuit that detects a power value from a terminal voltage and a terminal current of the synchronous machine; a second power detection circuit that detects a power value from a power value of the current flowing through the power transformer; an addition circuit that outputs a deviation signal from the signals from the first and second power detection circuits; a first phase compensation circuit that performs phase compensation based on the deviation signal of the first phase compensation circuit; and a signal amplification circuit that amplifies the output of the first phase compensation circuit and outputs it as a stabilization signal to the automatic voltage regulator. An excitation device for a synchronous machine characterized by comprising a system stabilizing device. (2) A second phase compensation circuit that performs phase compensation based on the output signal from the second power detection circuit, the outputs of the first and second phase compensation circuits being amplified and used as stabilizing signals. 2. The excitation device for a synchronous machine according to claim 1, further comprising a system stabilizing device including a signal amplifying circuit that outputs to the automatic voltage regulator.