JPS6198200A - Excitation control system - Google Patents

Abstract

PURPOSE:To suppress the variation in the terminal voltage of a variable speed regulator at system defect time by providing means for calculating the time of applying the strengthened amount of an excitation on the basis of a defect phase, a slip and a machine constant when a defect occurs at a system side. CONSTITUTION:A defect state discriminator 24 judges the phase and the degree of a defect from the voltage and the current of a generator. An exciting phase controller 25 calculates the phase to be strengthened in the excitation from the machine constant, operating state and the defect state on the basis of the signal from the discriminator 24. A calculator 27 takes the difference between a terminal voltage Et and a reference voltage EtO, and a converter 28 converts the output to a slip frequency. A switch 29 is closed when the output of the converter 28 is applied to the excitor. The closing time of the switch 29 is controlled by the output of the controller 25. A calculator 30 adds the exciting amount before strengthening the excitation from the converter 26 and the strengthened amount of the excitation from the switch 29, and supplies it to an excitation amount setter 17.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an excitation control method for a variable speed power generation system that can be operated at any rotation speed using an induction machine with secondary excitation, and is particularly applicable to the This invention relates to an excitation control method for suppressing fluctuations in terminal voltage of a variable speed machine.

[, Background of the invention]

Conventional variable speed power generation systems have the following problems: the load cannot be adjusted during pumping, the efficiency of the system changes due to changes in the generated power required from the grid during power generation operation, and the efficiency of the system changes due to changes in head etc. during pumping operation. The disadvantage was that the efficiency of the system varied.

In order to eliminate these inconveniences, research is underway to operate the above system at maximum efficiency, regardless of power generation or lift. This research is progressing in the direction of creating a so-called variable speed power generation system in which a conventional synchronous pumped storage generator is operated by an induction machine with secondary excitation. In this way, by using a variable speed power generation system, the generated power can be
It is said that it will be possible to operate the system at maximum efficiency regardless of the lift height. Therefore, research is underway to realize such a variable speed power generation system.

Regarding such a variable speed power generation system, for example, it was announced in the 1981 National Institute of Electrical Engineers of Japan paper, 4553, "Variable speed operation characteristics of large capacity synchronous motor", There is no mention of a specific excitation control method for this purpose.

[Purpose of the invention]

The present invention has been made in view of the above points, and its purpose is to operate a variable speed power generation system with high efficiency under various operating conditions of power generation and pumping, and to reduce the terminal voltage of the variable speed machine in the event of a system fault. An object of the present invention is to provide an excitation control method that suppresses fluctuations.

[Summary of the invention]

The present invention operates a visiting machine with secondary excitation at an arbitrary rotation speed,
In a variable speed power generation system in which secondary excitation is performed at a frequency of 1000 Hz, when an accident occurs on the grid side, a means is provided for calculating the point at which an enhanced amount of excitation is applied based on the fault phase, 500 Hz and the mechanical constant, By closing a switch that applies an enhanced amount of excitation based on the output of this means, it is possible to control the timing at which excitation is applied to each phase of silver.

[Embodiments of the invention]

Hereinafter, we will explain the embodiments of the present invention, but first we will explain the matters that formed the basis of the present invention. □゛.

Figure 2 shows an overview of the variable speed power generation system.

In the figure, 1 is a stator and 2 is a rotor.　　.

In addition, 5a to 5C are the a, b, and C phase windings of the stator, and 6a
~6C shows the ALB and C phase windings of the rotor, respectively. Furthermore, if the rated frequency fl is S, the speed of the rotor 2 is f(1-8), so if the excitation windings 6a to 6C of the rotor 2 are all excited at the frequency bs, the rotation The rotary magnetic field of the child 20 does not rotate at zero (synchronous speed), and accordingly has the same speed as the rotating magnetic field speed of the stator 1. Reference numeral 7 denotes a measuring section that measures the number of rotations of the rotor 2, and supplies the output from this measuring section 7 to the rotational speed detecting section 3. This speed detection section 3 detects the frequency and gives the detected value to the voltage generation section 4. The voltage generating section 4 generates a voltage according to the frequency, and excites the secondary windings 6a to 6C. By doing so, even if the rotation is performed at an arbitrary number of rotations, a voltage at the system frequency can be simply generated in the secondary windings 6a to 6C. That is, in the first example, the rotating magnetic field of rotor 2 is f (1-8) + fS = f ...... (
1) Regardless of whether it is wide or wide, an output of the rated frequency □ wave number will be obtained from the stator l.

FIG. 3 is a block diagram showing a specific example of the variable speed power generation system that is the basis of this embodiment, and shows a case where the variable speed machine 1.2 is connected to the grid and is in operation. 10
1 and 2 show the same stator and rotor as in FIG. 2, respectively. Static head H and output' command P
When a is given to the command value calculation circuit 15, this command value calculation circuit 15 calculates the governor valve opening command value H in consideration of efficiency.
v and speed command value N, are calculated. Reference numeral 14 denotes a valve opening setting device of the speed governor. This valve opening setting device 14 receives the opening command value Hv from the command value calculation circuit 15, and calculates the time based on this valve opening command value Hv. The valve opening degree is set with a delay, and this determines the valve opening degree of the speed governor. 13 is a water turbine characteristic section, and this water turbine characteristic section 13 is a static head H1 valve opening setting device 1.
The valve opening degree of the speed governor from 4 and the rotation speed N from the speed generator
It is determined by The rotor 2 of the variable speed machine rotates according to the water turbine characteristic section 13. The speed generator 11 can detect the rotation of the rotor 2, and the speed changes depending on the output. Detected. 19 is a current transformer, 20 is a voltage transformer, and the outputs of these are supplied to an active power calculation section 21. The active power calculating section 21 calculates and outputs the active power P based on the outputs from the current transformer 19 and the voltage transformer 20. Reference numeral 16 denotes a phase difference angle calculation unit of the secondary winding, and this phase difference angle calculation unit 16 calculates the output from the active power calculation unit 21, the output command PO1, the speed command value N0 from the command value calculation circuit 15, and the speed deprivation machine. The phase difference is calculated based on the speed N from 11 and output to the calculation unit 17. The calculation unit 17 sets the amount of excitation of the secondary circuit (223 to 22C) from the above output. 1
Reference numeral 8 denotes a voltage adjustment section, and the voltage adjustment section 18 controls the voltage value of the excitation amount based on the voltage signal □ from the voltage transformer 20. The phase shifting parts 23a, 23b, and 23C take in the amount of excitation set by the setting part 17, and apply the amount of excitation to the a, b, and C phases using this. 22a, 22b.

If 22C is an excitation winding in which phases 9a, b, and c are excited by the amount of excitation phase shifted by the phase shifters 23a to 23c, the system will be as shown by the solid line A in FIG. In the event of an accident, the terminal voltage fluctuates at a constant frequency.

For this reason, it is necessary to establish an excitation method that prevents the terminal voltage from fluctuating at all υ frequencies even in the event of a system fault. The aim is to establish an optimal system for

Next, one embodiment of the present invention will be specifically explained with reference to FIG.

FIG. 4 is a system diagram showing a so-called variable speed power generation system that can be operated at any rotation speed using a visiting machine with secondary excitation. The variable speed generator 0 is connected to the grid 10 via a power transmission line. A voltage transformer 20 and a current transformer 19 are installed on the power transmission line.

Additionally, a Francis turbine is commonly used for pumped storage power generators. The relationship between the output of the water turbine and its efficiency is as shown in FIG. In Figure 5, the horizontal axis shows the water turbine output and the vertical axis shows the efficiency.
This is shown using the rotation speed as a parameter. P l
e P2 is the water turbine output, η section, η2 is the efficiency, N,
, Ns indicates the number of rotations. This figure shows the maximum efficiency η1 at the output P1 at the rotation speed N, and the rotation speed Nz at the output P2 at each output. This indicates that it will snow. As described above, the rotational speed N at which the efficiency η is the highest varies depending on the output P, and the present invention aims to operate at the point of maximum efficiency, and is also possible in the event of a system accident. This eliminates fluctuations in the terminal voltage of the transmission.

In FIG. 4, the variable speed power generation system GK (stator 1 and rotor 2 in FIG. 3) changes the characteristics of the generator when a command Po for the generated power required for the generator is given from the operating end T. Highly efficient operation is possible by considering the head of water□
U, rotation speed No of the generator, opening degree Hv of the governor valve V of the water turbine
are determined by the control command unit C, and control is performed so that the operation can meet these values. Note that the control command unit C includes elements 13 to 18, 23a to 23 in FIG.
It is composed of c. Further, 21 is an active power calculation unit; 1
1 is a speed generator, and Ex is an excitation circuit. In such a situation, when a command to reduce the generator output is given, the rotation is adjusted to maximize the efficiency of the generator based on the generator output and water head using a pre-specified method. By controlling the number and valve opening degree, efficient operation can be achieved.

On the other hand, the deviation of the generator rotation speed from the rated value is caused by the excitation circuit Ex
As described above, by using the sub-frequency as information on the rated frequency, an output at the rated frequency can be obtained.

Next, a specific example of secondary excitation will be explained. As shown in FIG. 3, the three-phase secondary excitation winding is constructed as follows. That is, the phase angle Δδ of the functions for obtaining the excitation amounts of the p, a, b, and c phases is determined based on the command given from the operating end T in FIG.

The excitation voltages of phases a, b, and c are Vla, V, and b.

vt, then Vf a=Esin(7r f s t+δ.+Δδ)
v t b =Esla (2πfst+δG+Δδ−
120') Vl ,=Esia(2πfst+δ0+Δ
a-240°)...(2) Here, E is a voltage value determined by the speed and the operating state of the variable speed machine, δG is a phase angle determined by the operating state of the variable speed machine, and Δδ is a phase angle controlled by the output of the control command section. When performing control using the above equation, control may be performed using voltage E for a reactive power control command, and control using a phase angle Δδ for an active power control command.

In Figure 4, an accident occurred at point F on the power transmission line, and the
Figure 6 shows the change in terminal voltage when one line of a transmission line consisting of two lines is opened at m5.As is clear from waveform A shown in the figure, the terminal voltage has vibration Unfortunately, this frequency is the highest frequency.This is because the AVR strengthens υ excitation regardless of the phase of excitation.

The reason for this is thought to be as follows. That is, when the excitation is strengthened by the AVR, a one-phase equal number circuit of the excitation section is shown as shown in FIG. Here Es1n(2πfs't
+θ) is *, 'Eosim(+rfa) after excitation reinforcement
t+θ) is the value before excitation reinforcement, ΔEs1a (2rfst
+0) is the amount of excitation reinforcement, L and R are the inductance and resistance of the secondary circuit, respectively, 2πf''s is the slip angle frequency, f is the power supply frequency, and θ is the phase angle of the excitation reinforcement application.

The current Δi due to excitation reinforcement at this time is as follows:
During dance and excitation reinforcement, a transient DC component determined by the phase (phase) is generated. As the excitation current is not excited or not, the terminal voltage is affected by the fluctuation of the slip frequency. By setting (θ−ψ) to zero, the transient DC valley of the excitation current can be made zero.

The AVR may be controlled to produce the effect. What is necessary is to control so that the amount of reinforcement is applied, and a.

Regarding the b and c phases, a phase difference of 120 degrees may be provided.

Next, a method for specifically controlling the phase will be described.

The excitation voltage of the variable speed machine fluctuates at the slip frequency (f3) as shown in waveform A in Figure 8, but after the accident occurs, it changes as shown in waveform B in the broken line in Figure 8. There is a need. At this time, as shown by ψ in the same figure, the above-mentioned through θ
If excitation is given at the dead point tP with an angle delay equal to , θ−ψ
= 0, so no transient DC component occurs. in particular,
Among the phase shifters 23a, 23b, and 23c in FIG.
You can understand that all you have to do is control the point in time when you can take advantage of the power that will be strengthened. Therefore, the present invention is constructed as shown in FIG.

FIG. 1 shows an embodiment of the excitation control method according to the present invention, and shows a specific example for controlling the amount of excitation enhanced by AVR.

In the figure, blocks 1, 2 .・11 to 21 are the third
Shows the same functionality as in the figure. Block 24 is an accident situation determination section, and this accident situation determination section 24 determines the phase of the accident and its degree from the voltage and current of the generator. In reality, this accident situation determining section 24 is implemented by providing each phase with the function of a low voltage relay or an overcurrent relay, which have been conventionally used frequently.

25 is an excitation phase control section, and this excitation phase control section 25
is activated by a signal given when an accident is detected by the accident situation determination unit 24, and only when this signal is given,
In order to strengthen the excitation, the phase at which the excitation is to be strengthened is calculated based on the mechanical constants, operating conditions, and accident type as described above, and control is performed according to this phase. In reality, the timing at which the switch SW shown in FIG. 7(C) is closed is controlled.

・Here, reference numerals 26 to 30 in the figure indicate details of the configuration of the voltage regulator 18 shown in FIG. The converter 26 is a part that converts the reference voltage Fto into a frequency, and the excitation voltage E6 before excitation reinforcement is shown in FIG. 7 Φ).
This corresponds to a calculation unit for sin (2πf'st+θ). 2
7 is a calculation section, and the calculation section 27 calculates the difference between the terminal voltage B1 and the reference voltage Eta. 28 is a conversion unit, conversion unit 28
converts this output to slip frequency. The converter 28 creates a signal corresponding to ΔEs1n (Zrfst 10) shown in FIG. 7(C).

29 is a switch, and the switch 29 closes when the output of the converter 28 is applied to excitation. The closing point of this switch 29 is controlled by the output of the excitation phase control section 25. 30 is an arithmetic unit, and the arithmetic unit 30 adds the excitation amount from the conversion unit 29 before excitation reinforcement and the amount of excitation reinforcement from the switch 29. Based on the output from the calculation section 30, the excitation amount of the excitation amount setting section 17 is calculated.

By doing this, the present embodiment is improved by creating the state shown in molding B in FIG. 6.

[Efficacy of invention]

According to the present invention, in a variable speed power generation system, fluctuations in terminal voltage at the time of a system fault can be suppressed, so stability is significantly improved.

In addition, according to the present invention, in a pumped storage power generation system that operates to generate electricity during the day and pump water at night in order to cover fluctuations, there is an advantage that it can be operated efficiently against various types of deer that are required by the system. be.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an overview of a control device that implements an embodiment of the present invention, Fig. 2 is a block diagram showing an overview of the principle of a variable speed pumped storage power generation system, and Fig. 3 is a control device of a variable speed pumped storage power generation system. 4 is a block diagram showing an overview of the present application, FIG. 5 is a waveform diagram showing the relationship between output and efficiency, FIG. 6 is a waveform diagram showing the terminal voltage fluctuation curve at the time of an accident, FIG. 7 is an equivalent circuit diagram shown to explain fluctuations in terminal voltage, and FIG. 8 is a waveform diagram shown to fully explain suppressing fluctuations in terminal voltage. Ex...excitation circuit, GI...variable speed power generation system,
L...Power transmission line, C...Control command unit, T...Operation end, l...Stator, 2...Rotor, 3...Surface detection unit, 4...Voltage Generation part, 5a to 5C... stator a, b, c phase windings, 6a to 6C... rotor a, b,
C phase winding, 7... Rotation speed measuring section, 10... System, 1
DESCRIPTION OF SYMBOLS 1... Speed generator, 13... Water turbine characteristic part, 14...
... Governor valve opening setting section, 15... Command value calculation circuit, 16... Secondary winding phase difference angle calculation section, 17... Secondary winding excitation amount setting section, 18...・Voltage y4 regular part, 19...
Current transformer, 20, Voltage transformer, 21, Active power calculation unit, 22a to 22C, 2 excitation magnets a, b,
c-phase winding, Po...output command value, N. ...Speed command value, N...Speed, 23a to 23C...
- Phase shift section, 24... Accident situation determination section, 25... Excitation phase control section.

Claims (1)

[Claims] 1. In a variable speed power generation system that operates an induction machine with secondary excitation at an arbitrary rotation speed and performs secondary excitation at a slip frequency,
When an accident occurs on the grid side, a means is provided to calculate the point in time to apply the excitation reinforcement amount based on information about the phase where the accident occurred, slippage, and the mechanical constant, and excitation is applied based on the output of this means. An excitation control method characterized by being able to control the point in time when excitation is applied to each phase by closing a switch for applying an amount of reinforcement.