JPH01136599A - Exciting method for synchronous generator - Google Patents

Abstract

PURPOSE:To prevent droppage of exciting voltage when an initial excitation power source is separated, by resetting an exciting voltage command to be provided to a phase controller to a preset value corresponding to an actual exciting voltage prior to the separation at the time of starting. CONSTITUTION:When a synchronous generator is started, a switch 3 is turned ON through a sequence controller 56 so as to feed exciting current from an initial excitation power source 2. Output signal from an error amplifier 53 is zero at this time. When terminal voltage increases to a first predetermined level (50% of rated value), the sequence controller 56 initiates error amplifying operation of the error amplifier 53. When the terminal voltage reaches to a second predetermined level (90% of rated value), the sequence controller 56 turns the switch 3 OFF to separate the initial excitation power source and turns an exciting voltage reset switch ON. Consequently, the error amplifier 53 starts control operation with a reset value being employed as an initial value of exciting voltage command.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention employs a particularly improved automatic voltage regulator.

This invention relates to a method for exciting a synchronous generator that establishes voltage reliably and quickly.

(Prior Art) In recent years, many synchronous generators are self-excited generators that derive power for excitation from their own terminal voltage.

In a self-excited generator, unless the terminal voltage is controlled, as the terminal voltage increases, the excitation voltage also increases, and the terminal voltage becomes unstable due to positive feedback in which the terminal voltage further increases.

Therefore, an automatic voltage regulator (hereinafter referred to as AVR) adjusts the excitation to keep the terminal voltage constant. When starting a self-excited generator.

Some initial voltage is required to obtain the excitation power to establish the voltage. In some cases, the terminal voltage due to the residual magnetic flux of the field core is used as this initial voltage, but in order to increase the degree of freedom in generator design and to ensure voltage establishment, a separate initial excitation power source is prepared for startup. A method is often used in which the excitation power source is taken from this power source only at certain times, and when a certain initial voltage is established, the initial excitation power source is cut off and the excitation power source is taken from the own terminal voltage.

FIG. 6 is a diagram showing an example of the configuration of such a commonly used self-excited generator. In FIG. 6, 1 is a synchronous generator, 2 is an initial excitation power source, 3 is a switch for turning off the initial excitation power source, 4 is a backflow prevention diode, and 5 is an AVR. In addition, 51 to 56 are elements constituting AVR5, and 51 to 56 are elements constituting AVR5.
is a voltage setter, 52 is a voltage detector, 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.
A wave rectifier using a pure bridge circuit is used.

SCH's pure bridge circuit has the characteristic that when the SCR control angle is an inductive load such as a generator's field circuit, the output voltage is zero when the SCR control angle is 900, positive voltage when the angle is 90° or less, and negative voltage when the angle is 90° or more. This is the circuit. This circuit is used by making the excitation voltage applied to the generator's field both positive and negative voltages, and quickly increasing and decreasing the excitation current.

This is to increase the response of synchronous generator terminal voltage control.

Further, FIG. 7 shows an example of a conventional error amplifier.

In FIG. 7, 531 is an operational amplifier, 532.533.
534 is a resistor, 535 is a capacitor, and 536 is an error amplification reset switch. The error amplifier 53 is a proportional integrator. This is to increase the DC gain and reduce the steady-state error.

A conventional method of exciting a synchronous generator will be described below with reference to FIGS. 6 and 7. First, normal operation will be explained. The voltage setting device 51 is a setting device that sets a 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, during normal operation, the sequence controller 56
Since the error amplification reset switch 536 in FIG. 7 is turned off, the error in both signals is amplified and output to the phase controller 54 as an excitation voltage command.

The phase controller 54 applies 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. In other words, if the terminal voltage feedback signal of electric machine 1 is smaller than the value of the terminal voltage command signal, the field current is increased by decreasing the SCR control angle and increasing the field voltage. Increase voltage. Conversely, if the terminal voltage feedback signal of the synchronous generator 1 is larger than the value of the terminal voltage command signal, the S'CR control angle is increased and the field voltage is decreased to reduce the field current and the synchronous generator 1 Decrease the terminal voltage of This keeps the terminal voltage of the synchronous generator 1 constant.

When starting the synchronous generator 1, the sequence controller 56 turns on the switch 3 to supply excitation current from the initial excitation power source 2. At this time, the error amplification reset switch 536
When turned on by a command from the sequence controller 56, the error amplifier 53 is reset and the excitation voltage command is set to zero. The phase controller 54 has a characteristic that when the excitation voltage command is zero, the SCR control angle of the power converter 55 is at the maximum, that is, the γ limit. When the terminal voltage increases to a predetermined first value (for example, 50% of the rating) by the initial excitation power source 2, the sequence controller 56 turns off the error amplification reset switch=4-536 to start error amplification. 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, the initial excitation power supply 2 is cut off, and normal operation begins.

(Problems to be Solved by the Invention) FIG. 8 shows the characteristics of the signals of various parts over time during starting in the conventional synchronous generator excitation system.

In the figure, signal A is the terminal voltage value of synchronous generator 1, signal B is a signal from which the sequence controller 56 instructs the switch 3 to turn on or off, signal C is the excitation voltage of synchronous generator 1, and signal 1 is the synchronous generator. Excitation current of machine 1, signal E is phase controller 54
This is the excitation voltage command signal input to the

Figure 9 shows the instantaneous waveform of the excitation voltage just before the switch 3 is turned off at time T2 in Figure 8, Figure 10 shows the instantaneous waveform of the excitation voltage just after the switch 3 is turned off at time T2, and the excitation voltage at time T3. Figure 11 shows the instantaneous voltage waveform. 9, FIG. 10, and FIG. 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 signal A in FIG. 8, according to the conventional synchronous generator excitation system, when the switch 3 is turned off and the initial excitation power source 2 is disconnected, the terminal voltage drops significantly. This is because when the initial excitation power supply is connected, most of the excitation current is supplied by this power supply, and as shown in Fig. 9, <SCR
The control angle is considerably larger than 906, and when switch 3 is turned off in this state and the initial excitation power source is cut off, the average voltage of the excitation voltage becomes a negative voltage as shown in Figure 10, and the excitation current This is because the voltage decreases and the terminal voltage drops rapidly.

At this time, since the terminal voltage is lower than the rated voltage, the error amplifier 53 works to increase the excitation voltage command as shown in signal E in Figure 8, but the error amplifier 53 responds in order to stabilize the control system. Since there is a delay, the drop in terminal voltage does not recover immediately. FIG. 11 shows the excitation voltage when the excitation voltage command increases under the control of the error amplifier 53, the SCR control angle decreases, and the terminal voltage is established.

This decrease in terminal voltage not only lengthens the starting time of the synchronous generator, but also causes the terminal voltage to be lower than the required initial voltage if the response of the error amplifier 53 is slow or the voltage of the initial excitation power supply 2 is low. In some cases, the engine speed may drop to such low levels that it may not be possible to start. In particular, the response of the error amplifier 53 must often have a delay depending on the characteristics of the power system to which the synchronous generator 1 is connected.

Designing a synchronous generator and a magnetic dynamic system in consideration of these characteristics is complicated and time-consuming, and also imposes various restrictions on the system configuration. For example, with an emergency generator, it takes a long time from a power outage to the start of the emergency generator, so it is necessary to increase the battery capacity of the uninterruptible power supply that uses the battery that supplies power during this time. Ta.

[Structure of the invention]

(Means for Solving the Problems) The synchronous generator excitation method of the present invention is characterized in that when the initial excitation power source is cut off at the time of starting the synchronous generator, the excitation voltage command given to the phase control circuit is The excitation voltage is reset to a predetermined value corresponding to the excitation voltage to prevent the excitation voltage from decreasing.

(Function) In the present invention, the above-mentioned means can prevent a drop in the excitation voltage when the initial excitation power source is turned off, and can eliminate a drop in the synchronous generator terminal voltage. As a result, not only can the voltage rise at the time of starting be made faster, but also even if the response of the error amplifier is slow or the voltage of the initial excitation power supply is low, there is no drop in the terminal voltage, so reliable starting is possible.

(Embodiment) The embodiment shown in FIGS. 1 and 5 to which the synchronous generator excitation method of the present invention is applied will be described below. In FIGS. 1 and 5, the same reference numerals as in FIG. 6 indicate the same components.

In FIG. 1, in order to realize the synchronous generator excitation method of the present invention, the excitation voltage command given to the phase controller is switched from the error amplifier 53 to the command system for the phase controller 54 when the initial excitation power source is disconnected. The present invention is characterized in that an excitation voltage command resetter 57 is provided which resets the excitation voltage to a predetermined value corresponding to the actual excitation voltage before release. FIG. 2 shows a specific example of the circuit configuration of the excitation voltage command reset units 1 to 57. In FIG. 2, 571 is an operational amplifier for adding reset values;
72 is an operational amplifier for polarity reversal, 573 to 577 are resistors for calculation, and 578 is an excitation voltage reset switch that turns on and off the bias applied to the excitation voltage command. 5
79 is a reset value setter.

Next, the excitation method of the synchronous generator of the present invention is shown in FIGS. 1 and 2.
This will be explained using FIGS. 3, 4, and 7.

First, the calculation resistors 573 to 577 of the excitation voltage command resetter 57 in FIG. 2 have the same resistance value, and therefore,
The gains of the operational amplifier 571 for adding the reset value and the operational amplifier 572 for polarity inversion are 1. During normal operation,
The excitation voltage reset I switch 578 in FIG. 2 is turned on by the sequence controller 56 in FIG. 1, and a constant value signal from the reset value setter 579 is added to the excitation voltage command. However, as shown in Figure 7, which is the same as before,
Since the error amplifier 53 is a proportional-integral amplifier, the DC gain is infinite, and the excitation voltage is controlled to a value that maintains the terminal voltage of the synchronous generator 1 at the set value, regardless of the signal from the reset value setter 579 in FIG. be done. That is, during normal operation, the characteristics are exactly the same as those of the conventional control method without any loss of characteristics.

Next, control at the time of starting the synchronous generator 1, which is a feature of the present invention, will be explained. At the time of starting, the sequence controller 56 turns on the switch 3 and supplies excitation current from the initial excitation power source 2. At this time, the error amplification reset switch 536 of FIG. 7 of the error amplifier 53 is turned on in response to a command from the sequence controller 56, resetting the error amplifier 53 and making the output signal zero voltage. Further, the excitation voltage reset switch 578 in FIG. 2 of the excitation voltage command resetter 57 is
It is turned off by a command from the sequence controller 56, the reset value setting device 579 is disconnected, and the phase controller 54 is turned off.
The excitation voltage command given to is also zero.

At this time, the phase controller 54 has the same characteristic as the conventional one that when the excitation voltage command is zero voltage, the SCR control angle of the power converter 55 is maximized to the γ limit. When the terminal voltage rises to a predetermined first value (for example, 50% of the rating) by the initial excitation power source 2, the sequence controller 5
6 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 rating), the sequence controller 56 turns off the switch 3 to cut off the initial excitation power supply, and at the same time decreases the excitation voltage. Turn on the reset switch 578.

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

FIG. 3 shows the characteristics of each part signal over time in this control process. In FIG. 3, as in FIG. 8, signal A is the terminal voltage value of the synchronous generator 1, signal B is the signal from which the sequence controller 56 instructs the switch 3 to turn on or off, and signal C is the terminal voltage value of the synchronous generator 1. Excitation voltage and signal are synchronous generator 1
The excitation current and signal E are excitation voltage command signals input to the phase controller 54. Further, the signal F is a signal that the sequence controller 56 instructs to turn on or off the error amplification reset switch 536, the signal G is the output signal of the error amplifier 53, and the signal H is a signal that the sequence controller 56 instructs to turn on or off the excitation voltage reset switch 578. This is a signal that commands OFF.

FIG. 4 shows the instantaneous waveform of the excitation voltage immediately after the switch 3 is turned off at time T2 in FIG.

Similar to 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. Time T. , T1. T, , T, are the same timings as in FIG. 8, and switch 3 is turned off at time T2.
The instantaneous waveform of the excitation voltage immediately before turning off is the same as that shown in FIG. 9, and the instantaneous waveform of the excitation voltage at time T3 is the same as that shown in FIG. 11.

As can be seen by comparing FIG. 8 and FIG. 3, according to the excitation method of the present invention, the initial excitation power source 2
It is possible to eliminate a drop in the terminal voltage of the synchronous generator 1 when the synchronous generator 1 is disconnected. This is because the value of the excitation voltage command signal is reset to the value set by the reset value setter 579 in FIG. 2 at time T2 when the initial excitation power source 2 is disconnected. In this example, the voltage set in the reset value setter 579 is the output voltage of the power converter 55 when the terminal voltage of the synchronous generator 1 is 90%, and can be easily determined by calculation or experiment in advance.
As a result, the exciting current does not decrease at time T2, and the synchronous generator can be started quickly and reliably.

Next, another embodiment of an excitation device to which the excitation method of the present invention is applied is shown in FIG. In FIG. 5, 58 is a new adder;
91 is an excitation voltage detector, 592 is an excitation voltage command calculator,
593 has a sample and hold device added. Also, the same numbers as in FIGS. 6 and 3 indicate the same components. In this example, the reset value setter 579 as in the example shown in FIG. This is a method in which the value immediately before release is held in a sample hold device 593 and used as the reset value of the excitation voltage command. According to this, preliminary tests, adjustments, etc. can be omitted.

Furthermore, in the example of FIG. 2, at time T2, the error amplifier 5
3 is reset momentarily, but 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 signal from the reset value setter 579 is sent to the error amplifier. It is sufficient to simply add it to the output signal of 53. Furthermore, although the embodiments of the present invention shown in FIGS. 1 and 5 are configured using a direct excitation method, the present invention exhibits similar effects even in a configuration using an exciter such as a brushless exciter. It is clear that

In addition, although the above embodiment shows an example in which the control is performed by analog circuit hardware, the means for realizing the present invention is not limited to this, and may be performed by a software program using a microcomputer or the like. .

〔Effect of the invention〕

As described above, in the present invention, when the initial excitation power source is cut off 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 cut off. By doing so, it is possible to prevent a drop in the excitation voltage when the initial excitation power source is turned off, and it is possible to eliminate a drop in the synchronous generator terminal voltage. This not only speeds up the voltage rise at startup, but also allows the terminal to Reliable starting is possible because there is no voltage drop. Therefore, restrictions on the design of the synchronous generator and excitation system can be significantly reduced, and the design time, which was conventionally complicated and time-consuming, can also be reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an embodiment of an excitation device to which the synchronous generator excitation method 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. Figure 3 is a waveform diagram of each part for detailed explanation of the present invention.
The figure is an instantaneous excitation voltage waveform diagram for explaining the method of the present invention, Figure 5 is a circuit configuration diagram showing another embodiment of the excitation device to which the present invention is applied, and Figure 6 is a diagram of a conventional self-excited generator. 7 is a circuit diagram of a conventional error amplifier, and Figure 8 is a circuit diagram of a conventional error amplifier.
The figure is a waveform diagram of each part to explain the conventional excitation method.
10 and 11 are instantaneous excitation voltage waveform diagrams for explaining the conventional method. 1...Synchronous generator 2...Initial excitation power supply 3...
- Switch for turning off the initial excitation power supply 4... Diode for backflow prevention 5... AVR51... 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

Claims (1)

[Claims] 1. Compare the terminal voltage of the synchronous generator and the terminal voltage command value, and adjust the excitation current via the phase controller with the excitation voltage command value according to the error value to adjust the generator voltage. It is equipped with an automatic voltage regulator that maintains a constant voltage and an initial excitation power supply, and when starting, it is excited by the initial excitation power supply and the automatic voltage regulator, and after the voltage reaches a predetermined value, the initial excitation power supply is turned off. In a synchronous generator excited only by the automatic voltage regulator, the excitation voltage command value given to the phase controller when the initial excitation power source is cut off is reset to a predetermined value corresponding to the actual excitation voltage before the initial excitation power supply is cut off. A synchronous generator excitation method characterized by: