JP2524779B2 - Excitation method of synchronous generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to a method for exciting a synchronous generator that reliably and quickly establishes a voltage by using an improved automatic voltage regulator.

(Prior Art) In recent years, as a synchronous generator, a self-excited generator that uses a power source for excitation from its own terminal voltage is often used. In a self-excited generator, if the terminal voltage is not controlled, the exciting voltage rises as the terminal voltage rises, and the terminal voltage becomes unstable due to the positive feedback that the terminal voltage rises. Therefore, an automatic voltage regulator (hereinafter referred to as AVR) adjusts the excitation to keep the terminal voltage constant. At start-up of a self-excited generator, some initial voltage is needed to obtain the excitation power that establishes the voltage. The terminal voltage due to the residual magnetic flux of the field core may be used as this initial voltage, but in order to increase the degree of freedom in generator design and the certainty of voltage establishment, prepare another initial excitation power source and start it. A method is often used in which the excitation power source is taken from this power source only when a certain initial voltage is established, and the initial excitation power source is cut off to obtain the excitation power source from its own terminal voltage.

FIG. 6 is a diagram of a configuration example of a self-excited generator commonly used in this way. In FIG. 6, 1 is a synchronous generator, 2 is an initial excitation power source, 3 is a switch for cutting off the initial excitation power source, 4 is a diode for preventing backflow, and 5 is an automatic voltage regulator (hereinafter abbreviated as AVR). Further, 51 to 56 are elements constituting the AVR5, 51 is a voltage setting device, 52 is a voltage detector, and 53.
Is an error amplifier, 54 is a phase controller, 55 is a power converter, and 56 is a sequence controller.

As the power converter 55, as shown in FIG. 6, a full-wave rectifier using a pure bridge circuit of SCR is used. SC
The R pure bridge circuit has an output voltage of 0, 9 when the SCR control angle is set to 90 ° under inductive load such as the generator field circuit.
It is a circuit that has a positive voltage when it is 0 ° or less and a negative voltage when it is 90 ° or more. This circuit is used to increase the response of the synchronous generator terminal voltage control by increasing and decreasing the exciting current quickly by making the exciting voltage applied to the field of the generator both positive and negative. .

FIG. 7 shows an example of a conventional error amplifier. In FIG. 7, 531 is an operational amplifier, 532, 533 and 534 are resistors, and 535.
Is a capacitor and 536 is an error amplification reset switch. The error amplifier 53 is a proportional integrator. this is,
This is because the DC gain is increased to reduce the steady error.

Hereinafter, a conventional method for exciting a synchronous generator will be described with reference to FIGS. 6 and 7. First, the normal operation will be described. The voltage setting device 51 is a setting device that sets the terminal voltage command signal of the synchronous generator 1. This terminal voltage command signal is input to the error amplifier 53 together with the terminal voltage feedback signal of the synchronous generator 1 detected by the voltage detector 52. In the error amplifier 53, the error amplifier reset switch 536 of FIG. 7 is turned off by the sequence controller 56 during normal operation, so the error between both signals is amplified and output to the phase controller 54 as an excitation voltage command. .

The phase controller 54 gives a gate pulse to the SCR of the power converter 55 at a control angle such that the output voltage of the power converter 55 becomes a commanded value. That is, if the terminal voltage feedback signal of the synchronous generator 1 is smaller than the value of the terminal voltage command signal, the field angle is increased by decreasing the SCR control angle and increasing the field voltage to increase the synchronous generator terminal voltage. increase. vice versa,
If the terminal voltage feedback signal of the synchronous generator 1 is larger than the value of the terminal voltage command signal, the field current is reduced by increasing the SCR control angle and decreasing the field voltage to reduce the field current.
Reduce the terminal voltage of. This keeps the terminal voltage of the synchronous generator 1 constant.

At the time of starting the synchronous generator 1, the sequence controller 56 turns on the switch 3 to supply an exciting current from the initial exciting power supply 2. At this time, the error amplification reset switch 536 is turned on by the command from the sequence controller 56, and the error amplifier reset switch 536 is turned on.
53 is reset and the excitation voltage command is set to zero voltage. The phase controller 54 uses the power converter 55 when the excitation voltage command is zero voltage.
The SCR control angle is the maximum, that is, the γ limit. When the terminal voltage rises to a predetermined first value (for example, 50% of the rating) by the initial excitation power supply 2, the sequence controller 56 turns off the error amplification reset switch 536 to start error amplification. When the excitation voltage increases and the terminal voltage reaches a predetermined second value (for example, 90% of the rating), the switch 3 is turned off and the initial excitation power supply 2 is cut off to start normal operation.

(Problems to be Solved by the Invention) FIG. 8 shows the characteristics of the conventional synchronous generator excitation method with respect to the time change of the signals at the respective parts at the time of starting. In the figure,
The signal A is a terminal voltage value of the synchronous generator 1, the signal B is a signal by which the sequence controller 56 instructs the switch 3 to be turned on and off,
The signal C is the exciting voltage of the synchronous generator 1, the signal D is the exciting current of the synchronous generator 1, and the signal E is the exciting voltage command signal input to the phase controller 54.

The instantaneous waveform of the excitation voltage immediately before the switch 3 is turned off at time T ₂ in FIG. 8 is shown in FIG. 9, and the instantaneous waveform of the excitation voltage immediately after the switch 3 is turned off at time T ₂ is shown in FIG.
The instantaneous waveform of the exciting voltage at time T ₃ shown in the Figure 11.
In FIGS. 9, 10, and 11, the solid line is the excitation voltage waveform, and the broken line is the terminal voltage waveform of the synchronous generator 1. As can be seen from the signal A in FIG. 8, according to the conventional synchronous generator excitation method, the terminal voltage greatly decreases when the switch 3 is turned off and the initial excitation power supply 2 is cut off. This is because when the initial excitation power supply is connected, most of the excitation current is supplied by this power supply, and the SCR control angle is considerably larger than 90 ° as shown in FIG.
This is because when is turned off and the initial excitation power supply is cut off, the excitation voltage becomes a negative average voltage as shown in FIG. 10, the excitation current decreases, and the terminal voltage sharply decreases.

At this time, since the terminal voltage is lower than the rated voltage, the error amplification cutoff 53 works to increase the excitation voltage command like the signal E in FIG. 8, but the error amplifier 53 stabilizes the control system. Since the response has a delay, the drop in the terminal voltage does not recover immediately. FIG. 11 shows the excitation voltage when the excitation voltage command is increased by the control of the error amplifier 53, the SCR control angle is decreased, and the excitation voltage is established.

This drop in terminal voltage not only prolongs the starting time of the synchronous generator, but also when the response of the error amplifier 53 is slow or when the voltage of the initial excitation power supply 2 is low, the terminal voltage is below the required initial voltage. There are also cases in which the engine cannot be started because it has fallen to zero. In particular, the response of the error amplifier 53 often has to be delayed due to the characteristics of the power system to which the synchronous generator 1 is connected. Designing the synchronous generator and the excitation system in consideration of these characteristics is complicated and time-consuming, and various restrictions are imposed on the system configuration. For example, in an emergency generator, the time from a power failure to the start of the emergency generator becomes long, so it is necessary to increase the battery capacity of the uninterruptible power supply that uses the battery that supplies power during this period. It was

[Structure of Invention]

(Means for Solving Problems) The method for exciting a synchronous generator according to the present invention is an actual method before disconnecting the excitation voltage command given to the phase control circuit when disconnecting the initial excitation power supply at the start of the synchronous generator. It is characterized in that the excitation voltage is prevented from lowering by resetting to a predetermined value corresponding to the excitation voltage.

(Operation) In the present invention, the above-mentioned means can prevent a decrease in the excitation voltage when the initial excitation power supply is cut off, and prevent a drop in the synchronous generator terminal voltage. As a result, not only the voltage rise at the time of starting can be made faster, but also when the response of the error amplifier is slow or when the voltage of the initial excitation power source is low, the terminal voltage does not drop, so that a reliable start is possible.

(Example) An example shown in FIG. 1 and FIG. 5 to which the exciting method for a synchronous generator of the present invention is applied will be described below. 1 and 5, the same reference numerals as those in FIG. 6 indicate the same constituent elements.

In FIG. 1, in order to realize the excitation method for the synchronous generator of the present invention, the excitation voltage command to be given to the phase controller when the initial excitation power supply is cut off is set to the command system from the error amplifier 53 to the phase controller 54. Excitation voltage command reset device 57 for resetting to a predetermined value corresponding to the actual excitation voltage before release
Is provided. FIG. 2 shows a specific circuit configuration example of the excitation voltage command resetter 57. In FIG.
Reference numeral 571 is an operational amplifier for adding a reset value, 572 is an operational amplifier for polarity reversal, 573 to 577 are resistors for operation, and 578 is an exciting voltage reset switch for turning on and off a bias given to the exciting voltage command. 579 is a reset value setting device.

Next, the excitation method of the synchronous generator of the present invention will be described with reference to FIGS.
This will be described with reference to FIGS. 3, 3, 4 and 7.

First, the calculation resistance of the excitation voltage command resetter 57 shown in FIG.
573 to 577 are resistors having the same resistance value. Therefore, the operational amplifier 571 for reset value addition and the operational amplifier 5 for polarity inversion are used.
The gain of 72 is 1. During normal operation, the sequence controller 56 of FIG. 1 turns on the excitation voltage reset switch 578 of FIG. 2, and the excitation voltage command is added with a constant value signal from the reset value setter 579. . However, since the error amplifier 53 as shown in FIG. 7, which is the same as the conventional one, is a proportional-integral amplifier, the DC gain is infinite, and the excitation voltage is synchronously generated regardless of the signal from the reset value setter 579 of FIG. The terminal voltage of the machine 1 is controlled to a value that keeps the set value. That is, during normal operation, the characteristics are exactly the same without deteriorating the characteristics of the conventional control method.

Next, the control at the time of starting the synchronous generator 1 which is a feature of the present invention will be described. At the time of starting, the sequence controller 56 turns on the switch 3 to supply an exciting current from the initial exciting power supply 2. At this time, the error amplification reset switch 536 in FIG. 7 of the error amplifier 53 is turned on by a command from the sequence controller 56, resets the error amplifier 53, and sets the output signal to zero voltage. In addition, the second of the excitation voltage command reset device 57
The excitation voltage reset switch 578 in the figure is turned off by a command from the sequence controller 56, the reset value setting device 579 is cut off, and the excitation voltage command given to the phase controller 54 is also zero.

At this time, the phase controller 54 has a characteristic that the SCR control angle of the power converter 55 is maximum, that is, γ limit, when the excitation voltage command is zero, as in the conventional case. When the terminal voltage rises to a predetermined first value (for example, 50% of the rated value) by the initial excitation power supply 2, the sequence controller 56 turns off the error amplification reset switch 536 in FIG. 7 to start error amplification. . When the excitation voltage increases and the terminal voltage reaches a predetermined second value (for example, 90% of the rated value), the sequence controller 56 turns off the switch 3 to disconnect the initial excitation power supply and, at the same time, the excitation power supply. Turn on the reset switch 578.

Further, the error amplification reset switch 536 is momentarily turned on and then turned off. As a result, the electric charge of the capacitor 535 of the error amplifier 53 is discharged to zero voltage, and the signal set by the reset value setting device 579 becomes the excitation voltage command instead. When the error amplification reset switch returns to OFF, the value at this time is used as the initial value of the excitation voltage command to start control.

FIG. 3 shows the characteristics of the signals of the respective parts with respect to time in this control process. In FIG. 3, similarly to FIG. 8, signal A is a terminal voltage value of the synchronous generator 1, signal B is a signal for the sequence controller 56 to turn on and off the switch 3, and signal C is a signal for the synchronous generator 1. Excitation voltage and signal D are synchronous generator 1
The exciting current, signal E, is the exciting voltage command signal input to the phase controller 54. Further, the signal F is the sequence controller 56
Is a signal for instructing ON / OFF of the error amplification reset switch 536, signal G is an output signal of the error amplifier 53, and signal H is a signal for the sequence controller 56 instructing ON / OFF of the excitation voltage reset switch 578.

FIG. 4 is an instantaneous waveform of the exciting voltage immediately after the switch 3 is turned off at time T ₂ in FIG. 9 and 10
Similar to FIGS. 11 and 11, the solid line shows the excitation voltage waveform and the broken line shows the terminal voltage waveform of the synchronous generator 1. Time T ₀ , T ₁ , T ₂ , T ₃
Each has the same timing as in FIG. 8, and the instantaneous waveform of the exciting voltage immediately before the switch 3 is turned off at time T ₂ is shown in FIG. 9 and the instantaneous waveform of the exciting voltage at time T ₃ is shown in FIG.
It is the same as the figure.

As can be seen by comparing FIG. 8 and FIG. 3, according to the excitation method of the present invention, there is no decrease in the terminal voltage of the synchronous generator 1 when the initial excitation power supply 2 is disconnected as in the conventional method. can do. This is because the value of the excitation voltage command signal is reset to the value set by the reset value setting unit 579 of FIG. 2 at time T ₂ when the initial excitation power supply 2 is cut off. In this example, the voltage set in the reset value setting device 579 is 90% when the terminal voltage of the synchronous generator 1 is 90%.
It is the output voltage of the power converter 55 at the time of%, and can be easily obtained in advance by calculation or experiment. Thus never exciting current is decreased at time T _2, it is the start of the rapid and reliable synchronous generator.

Next, FIG. 5 shows another embodiment of the exciting device to which the exciting method of the present invention is applied. In FIG. 5, 58 is an adder and 59 is new.
1 is an excitation voltage detector, 592 is an excitation voltage command calculator, and 593 is a sample hold device. Also, the sixth
The same reference numerals as those in FIG. 3 and FIG. 3 indicate the same components.
In this example, a reset setting device like the example shown in FIG.
Without providing 579, an appropriate excitation voltage command value is calculated from the excitation voltage detected by the excitation voltage detector 591, and the initial excitation power supply 2
This is a method in which the value immediately before being cut off is held by the sample-hold device 593 and used as the reset value of the excitation voltage command. This makes it possible to omit preliminary tests and adjustments.

Further, in the example of FIG. ₂ , the error amplifier 53 at the time T ₂
However, if an error is allowed in the reset value of the excitation voltage command due to conditions such as the generator constant, the error amplifier 53 is not reset and the reset value setter
The signal of 579 may be simply added to the output signal of the error amplifier 53. Further, in the embodiment of the present invention shown in FIGS. 1 and 5, the direct excitation system is adopted, but the present invention also exhibits the same effect in a structure using an exciter such as a brushless exciter. Is clear.

In the above embodiments, the example in which the control is performed by the hardware of the analog circuit is shown, but the implementation means of the present invention is not limited to this, and may be performed by a software program using a microcomputer or the like. .

〔The invention's effect〕

As described above, in the present invention, when the initial excitation power source is disconnected at the time of starting the synchronous generator, the excitation voltage command given to the phase controller is reset to a predetermined value corresponding to the actual excitation voltage before being disconnected. As a result, it is possible to prevent a decrease in the excitation voltage when the initial excitation power supply is cut off, and it is possible to prevent a drop in the synchronous generator terminal voltage. This not only speeds up the voltage rise at start-up, but also when the error amplifier response is slow, when the excitation system loss is large and the initial voltage required for start-up is large, or when the initial excitation power supply voltage is low, the terminal Since there is no voltage drop, a reliable start is possible. Therefore, the restrictions on the design of the synchronous generator and the excitation system can be significantly reduced, and the design time, which was complicated and time-consuming in the past, can be shortened.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of an excitation device to which the excitation method for a synchronous generator of the present invention is applied, and FIG. 2 is a specific circuit configuration diagram of an excitation voltage command reset device used in the present invention. FIG. 3 is a waveform chart of each part for explaining the method of the present invention.
FIG. 5 is a waveform diagram of an instantaneous excitation voltage for explaining the method of the present invention, FIG. 5 is a circuit configuration diagram showing another embodiment of the excitation device to which the present invention is applied, and FIG. 6 is a conventional self-excited generator. FIG. 7 is a circuit configuration diagram shown in FIG. 7, FIG. 7 is a circuit configuration diagram of a conventional error amplifier, FIG. 8 is a waveform diagram of each part for explaining a conventional excitation method, and FIGS. 9, 10, and 11 are conventional methods. FIG. 6 is a waveform diagram of an instantaneous excitation voltage for explaining 1 …… Synchronous generator, 2 …… Initial excitation power source 3 …… Switch for disconnecting initial excitation power source 4 …… Backflow prevention diode, 5 …… AVR 51 …… Voltage setter, 52 …… Voltage detector 53… … Error amplifier, 54 …… Phase controller 55 …… Power converter, 56 …… Sequence controller 531 …… Operational amplifier, 532,533,534 …… Resistor 535 …… Capacitor 536 …… Error amplification reset switch

Claims (1)

(57) [Claims] 1. A synchronous generator and a terminal voltage of this synchronous generator are compared with a terminal voltage command value and the error value is amplified by an error amplifier. It is equipped with an automatic voltage regulator that regulates the current to keep the generator terminal voltage constant, and an initial excitation power supply, and is excited by the initial excitation power supply and the automatic voltage regulator at the time of starting, and the voltage becomes a predetermined value. After reaching, in the synchronous generator that disconnects the initial excitation power supply and is excited only by the automatic voltage regulator, the actual value before disconnecting the excitation voltage command value given to the phase controller when the initial excitation power supply is disconnected An exciting method for a synchronous generator, comprising: resetting to a predetermined value corresponding to an exciting voltage.