JPS62126899A - Excitation control system for variable speed pumping-up power plant - Google Patents

Abstract

PURPOSE:To suppress a variation in a terminal voltage of an induction machine by controlling the gain of the secondary excitation control system of the machine on the basis of defect detection information. CONSTITUTION:A speed command and an opening command of a governor valve are calculated on the basis of a static head and an output command by a command value calculator. The phase angles of the secondary windings 22a-22c of an induction generator 11 are calculated on the basis of an output command, the output of an induction generator 1, a speed command and a speed by a phase angle calculator. An excitation amount is set on the basis of the output of the phase angle calculator, the speed and the output of an excitation amount regulator by the secondary winding excitation amount setter. Constant current controllers 23a-23c control currents of the secondary windings 22a-22c on the basis of the set excitation amount. Gains 25a-25c of the controllers 23a-23c are controlled by information obtained through a voltage transformer 27 and a current transformer 28.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to an excitation control force and formula for a variable speed pumped storage power generation system that operates an induction machine with secondary excitation at an arbitrary rotation speed, and particularly relates to power generation and pumped storage power generation systems. The present invention relates to an excitation control method for a variable speed pumped storage power generation system suitable for stable control to a target value during automatic frequency control (AFC) operation.

[Background of the invention]

In conventional pumped storage power generation systems, the efficiency of the system deteriorates due to reasons such as the inability to adjust the load during pumping, the power required by the grid changes during power generation operation, and the head change during pumped storage operation. The downside is that it changes.

For this reason, research is underway to operate the above system at maximum efficiency regardless of power generation or lift. The research trend is moving toward adopting a so-called variable-speed power generation system, in which the pumped storage generator, which was previously a synchronous machine, is replaced with an induction machine with secondary excitation, and is operated at a rotation speed other than the synchronous speed. By adopting such a variable speed power generation system.

The system can be operated at maximum efficiency regardless of power generation or lift height. Therefore, various studies are being carried out to realize this variable speed power generation system. About this variable speed power generation system.

Although it has already been introduced in the 1981 National Conference Paper of the Institute of Electrical Engineers of Japan, &553 ``Variable Speed Operating Characteristics of Large-Capacity Synchronous Motors'', there was no mention of a specific control method.

[Purpose of the invention]

An object of the present invention is to provide an excitation control method for a variable speed pumped storage power generation system that can operate with high efficiency in various operating states of power generation and pumping, can be controlled to a stable target value during AFC operation, and has small voltage fluctuations in the event of an accident. Our goal is to provide the following.

(Summary of the invention) The present invention provides that the operating conditions for obtaining any power generation are effective head,
Determined from the relationship between rotation speed and governor pen opening,
Based on the knowledge that one of these operating conditions is that the efficiency of the system is determined by the number of revolutions, and that the above number of revolutions is determined by the difference between the turbine input and the generator output, the number of revolutions was adjusted to match the target value. In addition to controlling the internal phase angle to match the generator output with the command value, the gain of the secondary excitation control system is controlled based on the accident detection information of the variable speed machine, and the terminal voltage of the variable speed machine is controlled. The aim is to suppress fluctuations in

[Embodiments of the invention]

FIG. 1 shows an outline of a variable speed power generation system, and both the negative and secondary sides are composed of three-phase windings.

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

5a to 5C are the a, b, and C phase windings of the stator, and 6a to 6c are
indicates the a, b, and c phase windings of one rotor. Furthermore, if the rated frequency is f and the clearance is S, then the rotor speed is f (1
-5), and by exciting the excitation winding of the rotor at the frequency of slip S, the rotor's rotating magnetic field rotates at zero (synchronous speed) and becomes the same as the stator's rotating magnetic field speed. . 7 indicates a measurement unit that measures the rotation speed of the rotor, and from this output, 3 detects the slip frequency, and 4 generates a voltage according to the slip frequency to excite the secondary winding. There is. By doing so, even if the engine is operated at any rotational speed, the voltage at the system frequency can always be generated in the armature winding. That is, in the example of FIG. 1, the rotating magnetic field of the rotor is.

f (1-S)+f-8=f... (1)
Therefore, regardless of slippage, output at the rated frequency can be obtained. In this system, the gist of the present application is to devise an excitation control system that suppresses fluctuations in terminal voltage in the event of a system fault.

FIG. 2 shows a specific example of this system, and shows a case where a variable speed machine is connected to the grid and is in operation. S
1 and 2 indicate a power system, and 1 and 2 indicate the same stator and rotor as in FIG. When the static head difference H and the output command P0 are given, the 15 command value calculation circuit calculates the opening command value and the speed command value of the governor valve in consideration of efficiency. 14
is a valve opening setting device of the speed governor, and the opening command value from the command value calculation circuit 15 becomes the valve opening 13 of the speed governor with a time delay by the opening setting device 14. 12 (± water turbine part, this characteristic is the valve opening degree and rotation speed N of the static head H1 governor
It is determined by The rotor 1 of the variable speed machine rotates based on the input obtained from this water wheel characteristic.

Reference numeral 11 indicates a speed generator, and the speed N is detected by the output of this generator. Reference numeral 19 indicates a current transformer, and reference numeral 20 indicates a voltage transformer. At 21, active power is calculated based on the outputs of the current transformer 19 and the voltage transformer 20.

16 is a phase angle calculating section of the secondary winding, and the output P of 21 is
, output command value P, , speed command value N0. Calculated based on speed N. 17 is a setting unit that sets the excitation amount of the secondary circuit; 18 is an excitation amount adjustment unit that controls the absolute value of the excitation amount; 23a, 23b;

23c is a, b based on the excitation amount set in step 17.

This is the part that performs constant current control of the C phase. 22a.

22b and 22c are excitation windings that are excited in the a, b, and C phases according to the excitation amounts calculated by the constant current controls 23a to 23c. In such a system, if the gain of the constant current control system is fixed based on the conventional concept, the terminal voltage will fluctuate significantly in the event of a system fault. Therefore, it is necessary to establish an excitation method that prevents terminal voltage fluctuations in the event of a system fault.

The present invention attempts to establish an optimal system for a constant current control section that controls the amount of excitation shown in FIG.

Hereinafter, one embodiment of the present invention will be explained in detail with reference to FIG.

Figure 3 shows an example in which a so-called variable speed pumped storage power generation system G1, in which an induction machine with secondary excitation is operated at an arbitrary rotation speed, is connected to grid 8 via a power transmission line and is operated. It is. For power transmission lines, voltage transformer PT, current transformer C
T is installed.

Generally, Francis turbines are used for pumped storage generators.
The relationship between water turbine output and efficiency is shown in Figure 4. The figure shows the water turbine output on the horizontal axis, efficiency on the vertical axis, and rotation speed as a parameter * Pi + Px
is the water turbine output, η8. η2 is the efficiency, N, , N2 is the rotational speed, the output P□ is the rotational speed N, and the output P2 is the rotational speed N2, and the maximum efficiency η1 at each output is
．． This shows that η2. In this way, the rotational speed at which the efficiency is the highest varies depending on the output, and a feature of this system is that it attempts to operate at these points of maximum efficiency.

In Fig. 3, when the variable speed pumped storage power generation system G1 is given a control command for the generated power required for this system from the operating end T, it is operated with high efficiency, taking into consideration the characteristics of the generator and the head of the water. The rotational speed of the generator and the opening degree of the governor valve V of the water turbine are determined by the control command unit C so that the
The vehicle is controlled to operate to meet these values. In such a situation, when a command to reduce the generator output is given, the rotation speed and valve opening are adjusted based on the generator output and head to maximize the efficiency of the generator, using a method given in advance. This will enable efficient operation.

On the other hand, the deviation of the generator rotation speed from the rated value is caused by the excitation circuit E,
By using the Suberi frequency as the information, an output at the rated frequency can be obtained as described above.

Next, a specific example of secondary excitation will be explained. As shown in FIG. 2, the three-phase secondary excitation winding is constructed as follows. That is, the phase angle Δδ of the function for obtaining the excitation amount of the a p b H′C phase is determined by the command given from the operating end T in FIG.

The excitation voltage of a, b, and Q phases is V fa y V 1> H
When V is 1°, it is expressed as follows. Here, E: voltage value, δ, determined by slip and operating conditions of the variable speed machine. : phase angle determined by the operating state of the variable speed machine, Δδ: phase angle to be 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.

FIG. 5 shows the details of the conventional constant current control units 23a to 23c, and compares the difference between the output of the secondary winding control amount setting unit 17 and the output of the current transformers 24a to 24c using a comparison unit 26a.
~26c and multiplying this output by gains 25a~25c.

is under control.

In Figure 3, an accident occurred at point F on the power transmission line, and the
When one circuit of a power transmission line composed of two circuits is opened in mp, the terminal voltage will change significantly if the gain of the constant current control system is kept constant. This is because the armature current increases due to the accident, causing a change in the rotor current. This is because there is a large difference in the current of the constant current control system, and a large amount of excitation is required.

In order to suppress this amount of excitation, as shown in FIG. (undervoltage relay, overcurrent relay, etc.) to determine whether there is an accident.

When an accident is detected, the gains 25a to 25c of the constant current control system described above are lowered to reduce the control amount of secondary excitation caused by changes in armature current.

After that, the gain of the constant current control system is restored to its original value by removing the fault. By doing this.

Fluctuations in terminal voltage can be suppressed, and in addition, AFC (
Automatic frequency control), AQR (automatic reactive power control), etc. can be quickly responded to.

〔Effect of the 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 the operational effects are extremely large.

Furthermore, in pumped storage power generation systems that operate as power generators during the day and as pumped storage at night to replenish or consume fluctuations in power, they can be operated efficiently to meet the various power requirements of the grid, resulting in economical effects. is extremely large.

[Brief explanation of drawings]

Figure 1 shows an overview of the principle of a variable speed pumped storage power generation system. Figure 2 is a control overview of a variable speed pumped storage power generation system, Figure 3 is a diagram showing an overview of the present application, Figure 4 is a diagram showing the relationship between output and efficiency, Figure 5 is a conventional example, and Figure 6 is an example of the present application. E8...excitation circuit, G1...variable speed power generation system,
L...Power line, S...System, ■...Governor valve, C
...Control command unit, T...Operation end, 1...Stator,
2...Rotor, 3...Slip detection section, 4...Voltage generation section, 58-5c...A+B+C phase winding of stator,
6a to 6c...Rotor a, b, Q phase windings, 7...
Rotation speed measuring section, 11... Speed generator, 12... Water turbine section, 13... Valve opening degree, 14... Valve opening degree setter of speed governor, 15... Command value calculation circuit , 16... Secondary winding phase angle calculation section, 17... Secondary winding excitation amount setting section, 18.
...Excitation amount adjustment section, 19...Current transformer, 20...
Voltage transformer, 21... active power calculation unit, 22 a ~
22 c - secondary excitation al bT G phase winding. P, ... Output command value, No. ... Speed command value, N.
...Speed, 23a to 23c... Constant current control section, 24a
~24c...Current transformer, 25a~25c...Gain of constant current control section, 26a~26c...Comparison section, 27
...Voltage change 1 day! V2 Hard HPa Flower 3 Hard f'2r.

Claims (1)

[Claims] In a variable speed pumped storage power generation system in which an induction machine with primary and secondary excitation is operated at an arbitrary rotation speed, the gain of a control system for exciting the secondary is controlled based on accident detection information of the system. An excitation control method for a variable speed pumped storage power generation system featuring: 2. An excitation control method for a variable speed pumped storage power generation system according to the invention as claimed in claim 1, characterized in that the control system for exciting the secondary is a constant current control system. 3. In the invention set forth in claim 2, the variable speed pumped storage power generation system is characterized in that the accident detection information is an undervoltage detection relay or an overcurrent detection relay, and the constant current control system gain is reduced when the relay is operated. excitation control method.