JPH02155500A - Control method of ac excited synchronous machine - Google Patents

Abstract

PURPOSE:To continue operation without defective commutation by detecting keeping within a specified value of the voltage and slip of an AC excited syn chronous machine(AESM) and conducting re-excitation. CONSTITUTION:When short-circuiting and grounding accidents 27 generated in one circuit 25 of a transmission line are detected by a system accident detec tor 14 and transmission line breakers 21, 22 are open ed, an AESM controller 19 receives a signal from the system accident detector 14 and a breaker 16 for a short circuit is turned ON, and an AESM 1 is operated continuously as an induction motor. When the accidents are removed, the transmission line breakers 21, 22 are turned ON by a re-closing circuit, the re-closing circuit is completed and terminal voltage and slip detected by a terminal-voltage detec tor 17 and a slip detector 18 are kept within specified values, the AESM control ler 19 opens the breaker 16 for the short circuit, and a rotor 2 as the secondary coil of the AESM 1 is excited by a transformer 5 for an excitation converter and a cycloconverter 6 again and operation is continued.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides a control method for an AC excited synchronous machine directly connected to a pump-turbine in, for example, a pumped storage power plant, and in particular, a control method for increasing the AFC adjustment width during pumped storage operation. This concerns the re-operation of a variable speed pumped storage power plant after a system accident.

[Conventional technology]

Recently, electric power systems have increased the proportion of nuclear power and the number of pulley start-stops for thermal power plants has increased.
-C adjustment capacity is insufficient, and as a countermeasure, it has become necessary to adjust the input of pumped storage power plants.

FIG. 6 is a block diagram showing a conventional control method for an AC excited synchronous machine directly connected to a pump-turbine.
1 is the armature of an AC excited synchronous machine (hereinafter referred to as AESM), 2 is the rotor (secondary coil) of the AESMI, 3 is a reversible pump-turbine directly connected to the rotor 2 via the shaft 4, 5 6 is a cycloconverter connected between the rotor and the excitation converter transformer 5, 7 is a rotation speed detector of the rotor 2, and 8 is a variable speed 9 is a current transformer that detects the output current of AESMI, 10 is an instrument transformer that detects the output voltage of AESMI, and 11 is the output of current transformer 9 and instrument transformer 1.
12 is a phase inverting disconnector provided in the output path of AESMI, 13 is a phase inverting disconnector 12
14 is a system fault detector that controls the opening and closing of the generator breaker 13; 15 is an AE
The secondary short-circuit resistor 16 of SMI is a short-circuit breaker for the secondary short-circuit resistor 15, and its opening and closing are controlled by the system fault detector 14.

In order to operate the pump water turbine 3 at variable speed, the above AE
A method of secondary excitation of the SMI is usually adopted. According to this method, even if the rotational speed changes, parallel operation with the grid is possible by adjusting the frequency of secondary excitation to match the grid frequency.

Next, the control operation of AESMI after a system fault will be explained.

When the system fault detector 14 detects a system fault, it opens the generator breaker 13 and closes the short-circuit breaker 16 to operate the AESMI as an induction motor. Then, the system fault detector 14 detects that the system fault has been restored, opens the short-circuit breaker 16, turns on the generator breaker 13, and connects the excitation converter transformer 5. Either re-energize the rotor 2, which is the secondary coil, in the cycloconverter 6 and continue operation, or in the event of a system failure, give up on continuing operation and turn on the N, open the machine breaker 13, and open the short-circuit breaker 16. The unit was tripped to close the guide vane (not shown) and stop the pump-turbine 3.

[Problem to be solved by the invention]

The conventional control method for AC-excited synchronous machines is configured as described above, so even if the machine is re-excited after recovery from a system fault, AES will not occur.
If the rotation of M decreases too much and the slippage becomes large, or the output voltage decreases too much, the cycloconverter will fail to commutate even if it is re-energized, resulting in equipment damage, system disturbance, or a system accident. There were problems such as having to give up on continuing operation at times.

This invention was made to solve the above-mentioned problems, and when the system is restored after a system accident, the operating status of the AESM is monitored, it is determined whether or not the operation can continue, and the status of the AESM is determined so that the operation can continue. It is an object of the present invention to provide a control method for an AC-excited synchronous machine that can re-energize the machine if so, and give up re-excitation and trip the unit if a commutation failure is expected.

[Means to solve the problem]

The control method for an AC-excited synchronous machine according to the present invention detects the voltage and slippage of the AESM after recovery from a system fault, and if both the voltage and slippage are within specified values, re-excites the machine and continues operation. If the voltage is off, the AC-excited synchronous machine is tripped.

[For production]

The control method of the AC excited synchronous machine in this invention is based on the AES
By detecting that the voltage and slippage of M are within specified values and re-exciting, the cycloconverter is within its operating limits, so commutation failure does not occur (operation can continue).

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. The same or corresponding parts as in FIG. 6 are given the same reference numerals, and redundant explanation will be omitted. 17 is the terminal voltage detector of AES Ml,
18 is an AESMI slip detector, 19 is an AESMII+ control device in case of a system fault, 20 is a main transformer installed on the power transmission line side of the generator breaker 13, 21, 22, 23, 24 is a power transmission line breaker, 25 .26 is a power transmission line.

Next, we will explain the operation 0 For example, one line of a power transmission line 2
It is assumed that a short circuit/ground fault accident 27 occurs in 5. This short circuit
When the ground fault 27 is detected by the system fault detector 14 and the transmission line breakers 21 and 22 are opened, the A23M control device 19 receives the signal from the system fault detector 14 and opens the short circuit breaker 16. The AESML continues to operate as an induction motor.

The accident has been removed and the power line breaker is closed again at 21.22
is injected and if reclosing is successful, the current AESMl
The terminal voltage and slippage are detected by the terminal voltage detector 17 and the slippage detector 18, respectively, and if the terminal voltage and slippage are within the specified values, the A23M control device 19 opens the short circuit breaker 16 and re-energizes. The rotor 2, which is the secondary coil of the AESMI, is excited by the converter transformer 5 and the cycloconverter 6 to continue operation.

On the other hand, if the voltage and slip detected by the terminal voltage detector 17 and slip detector 18 are outside the specified values, A E
The S M tltl+ control device 19 opens the generator breaker 13 and unit trips the AESMI and pump water turbine 3 to stop it.

Next, the principle of operation will be explained with reference to FIGS. 2 to 5. FIG. 2 shows the operating waveform of the cycloconverter 6. In FIG. 2, U is the commutation type angle, γ is the commutation margin angle, α is the firing angle, and the regenerative operation mode (α °)
The operating limit of the cycloconverter 6 is determined by the commutation failure limit at .

In Figure 3, the horizontal axis is the coefficient of power supply voltage drop with sea 1 and P, U
, the value, the vertical axis is Co37, and the parameter Ks-1 is.

In Figure 4, the horizontal axis is the coefficient Kv-1 of the power supply voltage drop, P, tl
, value, and the vertical axis is the reverse bias voltage value Er immediately after commutation of the thyristor, and the parameter Ks-1 is the slip coefficient of AESM1.

In Figure 5, the horizontal axis represents the coefficient of power supply voltage drop, p, u,
The value, the vertical axis is the commutation type angle U, and the parameter Ks-1!
i: AESMI slip coefficient.

In Figures 3 to 5 above, the commutation margin angle limit value is G
O9Tearn + B rlistit + ut
imttT! t and r man determine the minimum commutation margin angle considering the turn-off time of the sirisk, and cosγ1
．． Determine 1.

Eγth 1L is defined by the turn-off characteristic of the thyristor, and ETllsiL is determined based on the fact that it cannot be turned off unless the voltage is above the specified voltage.

For example, if u l 1aiL is a 12-phase cycloconverter configuration, the commutation of the cycloconverter is 30"
However, if the overlap angle U reaches 30' or more, the commutation phenomena overlap, which makes the control of the cycloconverter unstable, which is not preferable.

Since the phase angle α is constantly changing, a 5″ margin is provided in consideration of the change in the phase angle α, and the commutation type angle U is limited to within 25°. Therefore, utt+e+t=25°.

(u-180°-T-α) As shown in Figures 3 to 5 above, the operating limit changes depending on the slip coefficient Ks-1. In the illustrated example, the slip Ks-1 at the time of restarting excitation is 0.8 or more. Then, if C1 is 0.5 or more in the coefficient of power supply voltage drop, C03Tsjn I
Since neither E rz+a+t nor utisit is applied, this shows that excitation can be restarted without ignition failure even if excitation is restarted.

In the above embodiment, the case of a variable speed pumped storage power plant was explained, but it may also be a generator using an AC excited synchronous machine or a generator with a flywheel, or a cyclotron as a secondary excitation device. Although the converter has been described, other converters, such as a GTO converter, may also be used (the same effects as in the above embodiments can be achieved).

〔Effect of the invention〕

As described above, according to the present invention, after the system accident is restored, the A
The terminal voltage and slippage of the ESM are detected, and if both are within specified values, re-excitation is performed and operation continues, and if they are outside the specified values, re-excitation is abandoned and the AESM is tripped. It has the effect of increasing stability and reliability without having a negative impact on the water system.

[Brief explanation of the drawing]

Fig. 1 is a block diagram illustrating a control method of the AESM according to an embodiment of the present invention, Fig. 2 is an operating waveform diagram of the cycloconverter, and Figs. 3 to 5 are characteristics showing commutation failure limits of the cycloconverter. 6 are block diagrams illustrating a conventional AESM control method. ■ is an AC excited synchronous machine, and 2 is a rotor. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] In the event of an accident in a system to which an AC-excited synchronous machine is connected, the AC-excited synchronous machine is operated as an induction motor by short-circuiting its rotor, and after the system is restored from the accident, the output voltage and slippage of the AC-excited synchronous machine are reduced. If the output voltage and slippage are within specified values, the excitation of the AC-excited synchronous machine is restarted and operation is continued, and if the output voltage and slippage are outside the specified values, the AC-excited synchronous machine is tripped. Characteristic control method for AC-excited synchronous machines.