JPS6299677A - Operation control system for variable speed pumping-up power generating system - Google Patents

Abstract

PURPOSE:To make it possible to constantly maintain a system frequency against the increase/decrease of a load in case of the governor-free operation during pumping-up, by providing the governor-free function for controlling a power control quantity corresponding to a frequency deviation based on the difference between a desired value and an actual frequency of the system frequency. CONSTITUTION:The difference between an actual frequency <f1> and a reference frequency <f0> in the system is required by an arithmetic unit 41. The output from the unit 41 is multiplied by a coefficiency in an arithmetic unit 42, and the output from the unit 42 is supplied to a limiter 43 so as to be added by a control command value 45 in an arithmetic unit 44. And, owing to this output from the unit 44 as a command signal, the governor value opening degree of the captioned power generating system is controlled for obtaining the predetermined optimum valve opening degree.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an operation 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 particularly relates to an operation control method for a variable speed power generation system that can be operated at any rotation speed using an induction machine with secondary excitation. [Background of the Invention] Regarding an operation control method suitable for stable control, conventional pumped storage power generation systems cannot adjust the load during pumping, and during power generation operation and pumping operation, There was a drawback that the efficiency of the system changed due to changes in power generation and the head during pumping.

For this reason, research is underway to operate the above system at maximum efficiency regardless of power generation or lift. In order to achieve the above objectives, we operated a pumped storage generator, which is a conventional synchronous machine, with an induction machine with secondary excitation, as known in the 1981 Institute of Electrical Engineers of Japan National Conference Paper No. 553r Variable Speed Operation Characteristics of Large Capacity Synchronous Motor. From the viewpoint that by creating a so-called variable speed power generation system, the system can be operated at its highest efficiency regardless of power generation or head, research is being conducted to realize this. However, there are papers like the one mentioned above regarding this good system.
There is no mention of specific control methods.

[Purpose of the invention]

The present invention compensates for the above drawbacks and enables
The purpose of the present invention is to provide an operation control method that provides stable control during governor-free operation in a variable speed pumped storage power generation system that operates with high efficiency.

[Summary of the invention]

The present invention proposes a method for stably controlling pumped water during governor-free operation in a variable speed pumped storage power generation system. The operating conditions for obtaining a given pump output are determined by the relationship between the pump head, rotation speed, and governor pen opening. Among these, the efficiency of this system is determined by the rotation speed and pen opening degree. Therefore, when the lift height and rotation speed are determined, the pen opening degree is controlled to achieve the highest efficiency. On the other hand, the above rotation speed is determined by the difference between the pump output and the electric motor input.

Therefore, it is necessary to control the phase angle of the secondary excitation voltage so that the motor input matches the command value. In this system, which is an induction machine with secondary excitation, the phase angle of the secondary excitation voltage is controlled in this way, and the governor valve opening degree is also controlled.

Specifically, during governor free operation, the phase angle is controlled using values obtained by converting the difference between the command value and the actual value of electric power and the difference between the target value and the actual value of frequency into electric power. , the actual rotational speed is actively used to control the valve opening, and the valve opening is controlled to a predetermined optimum valve opening based on the actual rotational speed and lift height. It attempts to operate with the input, rotation speed, and valve opening determined by the power control command value.

[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 stator a, b, and Q phase windings; 6a to 6c are the stator a, b, and Q phase windings;
indicates the a, b, and Q phase windings of the rotor. Furthermore.

If the rated frequency is f and the slip is S, the speed of one rotor is f (1-3), and by exciting the excitation winding of the rotor at a frequency and wave number of S, the rotating magnetic field of one rotor is rotates with zero slip (synchronous speed), which is the same as the speed of the rotating magnetic field of the stator. 7 indicates a measurement unit that measures the rotation speed of the rotor, and from this output, 3 detects the slip frequency, and 4
This shows that a voltage corresponding to the slip frequency is generated to excite the secondary winding. By doing this,
Even when operating at any rotation speed, the armature winding always has
It is possible to generate voltage at the grid frequency. That is, in the example of Fig. 1, the rotating magnetic field of the rotor is J・(1-8)+f −S=f .
...(1), and the output at the rated frequency can be obtained regardless of the slippage. In this system, the gist of the present invention is to devise a system that can stably control the pumping water to a target value at any rotation speed during governor-free operation.

FIG. 2 shows a specific example of a conventional system, and shows a case where a variable speed machine is connected to a power grid and is in operation.

Reference numeral 10 indicates an electric power system, and 1 and 2 indicate the same stator and rotor as in FIG. When the lift head H and the output command Po are given, the output command P.

is given to the phase angle calculation section 16 via the slow dither circuit 15.

On the other hand, the optimal valve opening is determined in block 25 according to a predetermined function based on the head I (and rotational speed N), and this output is given to the servo system 14, and the valve opening of the governor is determined with a time delay. Become.

Reference numeral 13 denotes a water wheel whose characteristics are determined by the valve opening degree and rotational speed N of the governor with a delay of the servo system 14.

Due to this water wheel characteristic, the rotor 2 of the variable speed machine rotates.

11 indicates a speed generator, and by this output.

Speed is detected. 19 indicates a current transformer, 20 indicates a voltage transformer, and 21 indicates a current transformer 19 and a voltage transformer 2o.
Calculate the active power based on the output. 16 is a phase angle calculation unit of the secondary winding, and the phase angle is calculated based on the output of 21 and the delayed output command Po of the delay circuit 15. 17 is a setting section that sets the amount of excitation of the secondary circuit, and 18 is a voltage adjustment section that controls the voltage value of the amount of excitation.

23a, 23b, and 23c are the excitation amount set in 17.
, b, and c phases. 22
A, 22b, and 22c are excitation windings that excite phases a, b, and c with excitation amounts phase-shifted by phase shifters 23a to 23c. In this way, due to the difference between the power control command value and the actual output, 2
Control is performed by calculating the phase angle of the next winding. On the other hand, the valve opening degree is controlled to be the optimum value based on the lift head and rotation speed.

As is clear from this figure, conventional systems do not have a so-called governor-free function that responds to fluctuations in system frequency. As a result, the grid frequency was changing significantly due to an imbalance between the grid's power generation capacity and load. In contrast, in this system, as shown in Figure 3, based on the difference between the target frequency value and the actual frequency,
Calculate the power control amount, add this value to the power command value,
Control the grid frequency to the target value.

By doing so, the unbalanced power can be absorbed or compensated for by the variable speed machine, so it is possible to prevent the system frequency from decreasing or increasing, and it is possible to ensure a stable supply of electric power.

FIG. 3 shows an example of detecting the difference between the reference frequency and the actual rotational speed and controlling the electric power control command value based on this value.

Block 40 indicates the transfer function of the detection section, and the actual frequency fL is obtained via the transfer function of block 40, and the difference between this output and the reference frequency fo is determined by calculation section 41. This output is multiplied by a coefficient in the calculation section 42. A limiter 43 is provided to the output of this calculation section 42, and this output and the control command value 45 are added together in a calculation section 44. The output of the arithmetic unit 44 obtained in this way is used as the output command value Po in FIG.

Hereinafter, one embodiment of the present invention will be explained in detail with reference to FIG. In FIG. 4, the induction machine with secondary excitation can be operated at any rotation speed. This shows an example in which a so-called variable speed pumped storage power generation system G1 is connected and operated to the grid 10 via the power transmission ML. Voltage transformers PTt, P are installed on the power transmission line.
Tz, current transformers CT l, CT 2 are installed.

Generally, Francis turbines are used for pumped storage generators.
The relationship between water turbine output and efficiency is shown in Figure 5.

In this figure, the horizontal axis represents the water turbine output, the vertical axis represents the efficiency, and the rotation speed is shown as a parameter. Pi and P2 are the water turbine output, η and η2 are the efficiency, and N1. NZ is the rotation speed,
Yl and Y2 indicate the valve opening degree. At output P1, rotation speed Nl
, valve opening degree Y1, output P2, rotation speed Nz, valve opening degree Y
2, the maximum efficiency η1 at each output. This shows that η2. As described above, the rotational speed at which the efficiency is the highest varies depending on the output, and the gist of the present invention is to operate at these points of maximum efficiency even during governor-free operation.

In FIG. 4, the variable speed pumped storage power generation system G1 performs highly efficient operation when a command value Pa of the electric power required for the electric motor is given from the operating end T, taking into consideration the characteristics of the electric motor and the head H. The rotational speed N and head I of the electric motor determined from the speed generator 11 and the head I (from which the opening degree of the governor valve of the water turbine are determined in the control command section C, and it is necessary to control the operation so as to meet these values). In such a state, when a command to change the motor output is given, the lift height H1 rotation speed N is determined by the method given in advance.
In order to maximize the efficiency of the electric motor, the valve opening degree of the governor is determined, and the rotation speed is controlled to achieve these values to achieve efficient operation.

During governor free operation, the governor free operation command and target frequency JO are given from the operating terminal T, and as mentioned above, the variable speed machine compensates for the excess or deficiency of electric power and controls the system frequency to operate. It turns out.

Figure 6 shows, as an example of determining the valve opening that gives the highest efficiency from the rotational speed N and head H, the points at which the efficiency of the system is the highest at each operating point, with the horizontal axis representing the rotational speed N and the vertical axis. The valve opening degree Y is taken as , and the head is shown as a parameter.

This figure shows the case where lift height H1>lift head H2. In this diagram,
If the rotational speed changes from N+ to N2 during operation with the head H+, this indicates that the valve opening degree needs to be controlled from Yl to Y2.

On the other hand, the deviation of the motor rotation speed from the rated value is caused by the excitation circuit Ex
By using the slip 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 functions for obtaining the excitation amounts of the a, b, and c phases is controlled by a command given from the operating end T in FIG. If the a, b, c'MI voltages of the secondary excitation circuit are Vffia+V1b+''IC, then it is given as follows.Here, E: Voltage value determined by the slip and operating conditions of the variable speed machine, δ0: Operation of the variable speed machine Phase angle determined by the state, Δδ: phase angle controlled by the output of the control command section.

When performing control using the above formula, voltage E is used for reactive power control commands, and voltage E is used for active power control commands.
It may be controlled by the phase angle Δδ.

An object of the present invention is to stably control pumped water during governor-free operation in the above system. Therefore, in the above configuration, it is necessary to control the phase angle (Δδ) of the excitation circuit to adjust the rotation speed and electric power to the target values, and to control the valve opening so as to achieve optimum efficiency.

For this purpose, active power is used as information for controlling the phase angle. In other words, the phase angle Δδ is: Δδ=P-Pa)dt+kxp(P-Po)
・=(3). Here, Po: Target value of active power considering deviation of grid frequency from reference frequency, P
: Actual value of active power, k'+ kIP : Constant.

On the other hand, pump input is controlled by adjusting the valve opening of the governor. That is, as shown in FIG. 2, the valve opening of the governor is controlled based on the actual values of the lift head and rotational speed so that the valve opening is a predetermined optimum valve opening.

7 to 9 are diagrams for explaining the present invention in detail, G1 in FIG. 7 represents a variable speed machine, numbers 02 to 0 represent a synchronous machine,
Trt to Tr4 are transformers, α1. G2 is the power transmission line, L
+, L2 indicates load. The results when the load is increased by closing the circuit breaker SW in this figure are shown in FIGS. 8 and 9.

In these figures, the horizontal axis shows time, and the vertical axis shows the deviation from the reference frequency of the variable speed machine in curve a and the reference frequency of the synchronous machine other than the variable speed machine in curve a.

Figure 8 shows the results when the governor free function is not provided, and the curve a showing the slip frequency of the variable speed machine has a constant value, whereas the deviation from the reference value of the frequency of other than the variable speed machine is Due to the increase in load, the number continues to decrease.

FIG. 9 shows the results when the method of the present invention is adopted,
Since the variable speed machine compensates for the increased load, the slip frequency curve of the variable speed machine decreases. Due to this effect, the frequency of the synchronous machines other than the variable speed machine slightly decreases, but remains at a constant value, and the effect of the present invention is clearly demonstrated.

〔Effect of the invention〕

According to the present invention, by providing a governor-free function that calculates a frequency deviation based on the grid frequency and a target frequency, converts this value into a power control amount, and controls the power control amount according to the frequency deviation. In governor-free operation during pumping, the system frequency can be maintained constant even when the load increases or decreases, so the effect on stability is extremely large.

Furthermore, in a pumped storage power generation system that operates as power generation during the day and as pumped storage at night to cover the fluctuating load of the grid, it can operate efficiently with respect to the electricity determined by the grid during pumped storage operation, so the economic effect is extremely large.

[Brief explanation of drawings]

Figure 1 is an overview of the principle of a variable speed pumped storage power generation system, Figure 2 is an overview of the control of the variable speed pumped storage power generation system, Figure 3 is a diagram showing an embodiment of the present invention, and Figure 4 is a diagram showing an embodiment of the present invention. The figure shown,
Figure 5 is a diagram showing an example of the relationship between output and efficiency of a variable speed machine, Figure 6
The figure shows an example of determining the optimum valve opening, Figure 7 is a model system for determining the effects of the present invention, Figure 8 is the result when the present invention is not adopted, and Figure 9 is the effect of the present invention. Diagram showing. Ex...excitation circuit, Gl...variable speed power generation system,
L...Power transmission line, ■...Governor valve, C...Control command unit, T...Operation end, 1...Stator, 2...Rotor,
3... Slip detection section, 4... Voltage generation section, 5a-5
c...Stator a. b, c phase winding, 6 a ~ 6 c - rotor a, b, c
Phase winding, 7... Rotation speed measuring section, 10... System, 11
... Speed generator, 13... Water turbine characteristics section, 14... Servo system, 15... Delay circuit, 16... Secondary winding phase angle calculation section,] 7... Secondary winding excitation Amount setting section, 18...
Voltage adjustment section. 19...Current transformer, 20...Voltage transformer, 21...
・Active power derivation unit, 22 a , 22 b , 22
c - secondary excitation a, b, c phase windings, Po... output command value, N... speed, 23 a, 23 b,
23 c...Phase shift unit, 25...Optimum valve opening calculation unit, 40...Detection unit transfer function, 41°42.44...
- Arithmetic unit, 43...Limiter, 45...Control command value.

Claims (1)

[Claims] 1. In a variable speed power generation system that operates an induction machine with secondary excitation at any rotation speed, during governor-free operation of pumped water, the deviation of the system frequency from the target value is multiplied by a constant and converted into a power control command value. An operation control method for a variable speed pumped storage power generation system, characterized in that the governor valve opening degree of the variable speed system is controlled based on this value.