JPS6281999A - Operation control method for variable-speed pumped-storage power system - Google Patents

Abstract

PURPOSE:To control system frequency stably on governor free-operation under pumping operation by controlling the number of revolution of an induction machine in response to a frequency deviation on pumping operation by controlling a governor. CONSTITUTION:A power control-command converter C1 adds a power control command P01 corresponding to a deviation between system frequency fL and reference frequency f0 and a power control command value P0 transmitted from a console T, and sends an overall power control command POG to a control circuit C. The control command section C computes the optimum valve opening Y of a governor valve 12 and the exciting voltage V of a variable speed machine G1 on the basis of a head command H transmitted from the console T, the number of revolution N from a revolution detector 11, the power control command POG and effective power from an effective-power computing section 21.

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 pumped storage power generation system that can be operated at any rotation speed using a wound induction machine, and particularly relates to a method for controlling the operation of a variable speed pumped storage power generation system that can be operated at an arbitrary rotation speed using a wound induction machine, and particularly during governor free operation during pumped storage operation. The present invention relates to an operation control method suitable for stably controlling system frequency.

[Background of the invention]

In conventional pumped storage power generation systems, it is not possible to adjust the load when pumping water, and the efficiency of the power generation system changes due to changes in the generated power required by the grid and the pumping height during power generation and pumping operations. There were drawbacks.

For this reason, research is underway to operate the above system at maximum efficiency regardless of the power generated or the lift height.

In order to achieve the above objective, we replaced the synchronous machine conventionally used as a pumped storage generator with an induction machine with secondary excitation (i.e.
Research is underway to realize a so-called variable-speed power generation system operated by a wound-wound induction machine.

Here, the variable speed power generation system will be explained.

FIG. 11 shows the principle of the variable speed power generation system.

In FIG. 11, G1 is a wound induction machine (hereinafter referred to as a wound induction machine).

), 1 indicates a stator, and 2 indicates a rotor. 5a to 5c are windings of each phase of a, b, and c of stator 1;
6a to 6c indicate the windings of the a, b, and a phases of the rotor 2.

If the rated frequency is f and the fullness is S, the speed of one rotor 2 is f (1-s).

By exciting the secondary windings 6a to 6c of the rotor 2 at a frequency of S, the rotating magnetic field of the rotor 2 rotates with a slip S of zero (periodic speed), and the speed of the rotating magnetic field of the stator 1 increases. becomes the same as The rotation speed of the rotor 2 is measured by the measurement unit 7, the slip frequency is detected from this output by the slip frequency detector 3, and then a voltage corresponding to the slip frequency is generated by the frequency/voltage converter 4, and this voltage is Secondary winding 68~6C
to excite it. By doing this, even if the operation is performed at any rotational speed, the primary windings 58 to 5c are always
It is possible to generate voltage at the grid frequency. That is, in the example of FIG. 11, the rotating magnetic field of the rotor 2 is:

f(1-s)+fs=f-(1), and regardless of the slip S, an output at the rated frequency can be obtained.

Documents related to the above variable speed power generation system
Although there is a paper Nα553 "Variable Speed Operating Characteristics of Large Capacity Synchronous Motor" at the 2011 National Conference of the Institute of Electrical Engineers of Japan (held from March 28 to 30, 1982), this document does not disclose any specific control method.

[Purpose of the invention]

An object of the present invention is to provide an operation control method that can stably control system frequency during governor-free operation under pumped storage operation in a variable speed pumped storage power generation system.

[Summary of the invention]

In order to achieve the above object, the present invention provides an operation control method for a variable speed pumped storage power generation system in which a wound induction machine is operated in response to fluctuations in the system load. The invention is characterized in that the deviation between the actual grid frequency and the actual system frequency is converted into a power control command value, and the rotation speed of the induction machine is controlled based on the converted power control command value.

By doing so, the variable speed machine can absorb or compensate for the unbalance between power demand and supply, thereby preventing a drop or rise in the system frequency and ensuring a stable power supply.

[Embodiments of the invention]

Next, an embodiment of the operation control method for a variable speed pumped storage power generation system of the present invention will be described based on the drawings.

First, Fig. 7 shows an overview of the variable speed pumped storage power generation system.

In this system, a variable speed machine G1 is operated by a water turbine 13, and the output power of the variable speed machine G is supplied to a power system 10 via a power transmission line.

That is, the optimal valve opening Y of the governor valve 12 is calculated based on the lift command H given from the operator console T and the rotation speed N from the rotation speed detector 11, and the opening degree of the governor valve 12 is controlled. On the other hand, a power control command P is given from the console T. Based on the voltage transformer (PT) 20 and current transformer (CT)
The active power calculation unit 21 calculates the active power based on the value detected by step 19, and controls the excitation circuit Ex of the variable speed machine G1 by applying the excitation voltage V to the excitation circuit Ex in consideration of the active power and rotational speed N. In other words, The output is controlled under a certain fixed pumping operation.

Next, FIG. 8 shows a more specific example of the variable speed pumped storage power generation system shown in FIG. 7 above. Note that the same reference numerals are used for parts that overlap with those in FIG. In the pumping operation control system, when a pumping head command H is given, the optimum valve opening degree calculation unit 25 calculates a predetermined characteristic (
Based on FIG. 9), a lift command H and a governor valve opening degree Y corresponding to the rotational speed N are output as parameters. This governor valve opening degree Y is given to the servo system 14. The servo system 14 controls the operation amount according to the input governor valve opening Y to the governor valve 1.
2 and adjust. In this way, the water turbine 13 is controlled to output according to the head command H.

On the other hand, the operation of the control system during such pumping operation is as follows. Now, power control command P.

is given, this power control command Pl is given by the delay circuit 1
5 to the phase angle calculation section 16.

Since the delay circuit 15 receives the power control command P0 in a stepwise manner, the delay circuit 15 directly applies the power control command P0 to the secondary windings 68 to 6c of the variable speed machine G1.
If used to control the excitation voltage V of the variable speed machine G□, the output of the variable speed machine G□ would change significantly, so the delay is made to prevent this. The power control command P0 that has passed through the delay circuit 15 is input to the phase angle calculation section 16. On the other hand, active power is determined by the active voltage calculating section 21 from the voltage and current of the system from the transformers 19 and 20, and is input to the phase angle calculating section 16.

The phase angle calculating section 16 calculates the excitation voltage V to be applied to the secondary windings 68 to 6C. Namely.

According to the command given from the console T, the secondary windings 6a~
Among the functions for obtaining the excitation amount of each phase in 6c, the phase angle A
Control δ. The a, b, and a phase voltages of the secondary windings 6a to 6c are set to V1. , V fk , V , , it is given as follows. Here, E is a voltage value, δ, determined by the slip and operating conditions of the variable speed machine. is the phase angle determined by the operating state of the variable speed machine, and Aδ is the phase angle controlled by the output of the control command section. When performing control using the above equation (2), for the reactive power control command is the voltage E, and the active power control command may be controlled by one phase angle Aδ.

Therefore, in the above configuration, the phase angle (Aδ) of the secondary windings 68 to 6c is controlled to adjust the rotation speed N and electric power P to the target values, and the governor valve 12
It is necessary to control the opening degree. Therefore, active power is used as information for controlling one phase angle. In other words, one phase angle Aδ is Aδ=fk(P Pa)dt+k yo P(P P
O)...(3). Here, Po is the target value of active power, P is the actual value of active power, and kl is 1. is a constant.

The phase angle Δδ thus obtained is output to the excitation amount setting device 17.

The excitation amount setting device 17 sets the excitation voltage v of the secondary windings 6a to 6c based on the number of rotations N (frequency f) and the phase angle Aδ.
The purpose is to find v,,v,.

The calculation formula is as shown in formula (2). The calculated excitation 6Ji voltage V, , Vh * Va is the phase shifter 23a.

It is applied to each winding 6a to 6c via 23b and 23c. Note that 18 indicates a feedback adjustment section for correcting the excitation voltage.

As described above, while controlling to achieve the optimum valve opening under the head command H, the phase angle Aδ of the secondary windings 68 to 6c is calculated from the deviation between the power control command value P0 and the actual output. , to control the power to an appropriate value.

Here, the so-called "
It is necessary to consider the ``governor-free function''. In other words, when the grid load increases, the balance between supply and demand between the power generation system and the grid load is disrupted, and the grid frequency changes significantly.

For example, Fig. 11 shows the simulation results of a variable speed pumped storage power generation system without a governor-free function.As can be seen from Fig. 11, the slip frequency curve f1 of the variable speed machine G1 is constant; For generators other than variable speed machines (conventional synchronous machines), the frequency decreases over time with respect to the reference frequency f0 as shown by the curve fll.

Therefore, as shown in FIG. 1, a power control command conversion device C according to the present invention is interposed between the operator console T and the control circuit C, and the system frequency f,... and the reference frequency (target frequency) f are interposed between the operator console T and the control circuit C.
, which deviation is added to the power control command p at and the power control command value P0 given from the console T, and is given to the control circuit C as a combined power control command P0° for the power generation system.

The power control command conversion device C1 will be described below.

In FIG. 2, a block 40 indicates the transfer function of the detection section, and the actual system frequency fL is obtained via the transfer function of the block 40, and the difference between this output and the reference frequency f0 is determined by the calculation section 41. It will be done. This output is controlled by a proportional control section 43 and an integral control section 44, and added by a calculation section 46 to perform PI control. By providing a feedback control unit 45 for this output and calculating the difference between this output and the output of the calculation unit 41 in the calculation unit 42, the offset amount of this system can be made zero.6 Next, the output P of the calculation unit 46 .

and the power control command P0 are added by the calculation unit 48. Output P of the arithmetic unit 48 obtained in this manner. , is the output command value P in FIG. Close and use.

As shown in FIG. 1, the actual system frequency j, is detected from the output voltage of the voltage transformer PT using a frequency detector F such as a frequency relay or a frequency counter.

Incidentally, a Francis turbine is generally used as a pumped storage power generator, and the relationship between the turbine output and efficiency is shown in FIG. 3. In FIG. 3, the horizontal axis represents the water turbine output, the vertical axis represents the efficiency, and the rotation speed is shown as a parameter. P□
p2 is the water turbine output.

η1. Let η2 be the efficiency -N1. NZ is the rotation speed, Yo.

Y2 indicates the valve opening degree. At output P□, rotation speed N□ and valve opening Y□, and at output P2, rotation speed N2. It is shown that the maximum efficiency at each output is η1°η2 at the valve opening degree Y2. As described above, the rotational speed at which the efficiency is the highest varies depending on the output, and it is important to try to operate at these points of maximum efficiency even during governor-free operation.

In this way, the system frequency jL and the reference frequency f are applied to the delay circuit 15 in FIG. Which deviation is the power control command pH1 to make zero?
Directive P6. Because it is given.

Phase angle calculation section 16 and excitation amount setting section 1 after the delay circuit 15
Excitation voltages V, , V, , V applied to the secondary windings 6a to 6c of the variable speed machine G1 via 7. is corrected to a value that absorbs or compensates for fluctuations in the system frequency, making it possible to always stabilize the system frequency.

Next, an example will be described in which one or more variable speed pumped storage power generation systems are provided in a network formed by a plurality of power generation systems. FIG. 4 shows a network formed by four generators 01 to G4.

A variable speed machine to which the present invention is applied to G among the four generators,
It is assumed that conventional synchronous machines are used for 01 to G4. Each generator G-G is a transmission line Ll Ω2゜ transformer TP
They are connected via i to T□. L engineer.

L2 indicates load.

Here, consider a case where the load is operated only at L4. In this case, it is assumed that the power generated by each of the generators 01 to G is balanced with the power required by the load, and there is no separately installed overload. At this time, there is no variation in the system frequency f.

Suppose now that the switch SW is turned on, the load L1 increases, and the system load increases. Then, in the conventional case, the system frequency f will decrease, but in the case of the present invention, as mentioned earlier, the variable speed machine G has a reference frequency corresponding to the decrease in the system frequency f! , Since the excitation voltage of the secondary windings 68 to 6c is controlled to compensate for any deviation, the variable speed machine G□ compensates for the shortfall, and even if there is a transient decrease, the system frequency f, is returned to the reference frequency f0 and becomes stable. However, in reality, the variable speed machine G1
There is a limit to the compensation capacity (governor free capacity) of the variable speed machine G1, and it is unrealistic to apply a load exceeding the capacity of the variable speed machine G1. As a countermeasure in this case, as shown in Figure 6,
A limiter 47 matched to the capacity of the variable speed machine G may be interposed between the addition calculators 46 and 48 to limit compensation beyond a predetermined value. Therefore, for the amount that cannot be compensated for by one variable speed machine G1, it is better to consider installing another variable speed machine.

Figure 5 shows the effect of performing the above operation in a simulation. G
In order to compensate for this by mechanical engineering, the slip frequency f of the variable speed machine G□ decreases over time. On the other hand, the frequencies f of the synchronous machines 62 to G4 other than the variable speed machine G decrease slightly, but as time passes, they gradually approach the reference frequency f8 to control large fluctuations.

Furthermore, in order to cover the fluctuating load on the grid, electricity is generated during the day,
In a pumped storage power generation system that operates as pumped storage at night,
It can operate efficiently even with the power determined by the grid during pumping operation.

〔Effect of the invention〕

As described above, according to the present invention, the frequency deviation is calculated based on the system frequency and the target (reference) frequency, this value is exchanged with the power control command value, and the power control amount is converted into the frequency deviation. In governor-free operation, control is performed according to increases or decreases in system load.

Grid frequency can be maintained constant.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a block diagram showing the main parts of the invention, Fig. 3 is a characteristic diagram showing the relationship between power generation output and efficiency, and Fig. 4 is a block diagram showing the main parts of the present invention. A system diagram showing an example of incorporating the invention into a network, Fig. 5 is a characteristic diagram showing simulation results of the invention, Fig. 6 is a block diagram showing another embodiment, and Fig. 7 is a conventional variable speed pumped storage power generation system. Fig. 8 is a block diagram showing details of a conventional variable speed pumped storage power generation system, Fig. 9 is a characteristic diagram showing the characteristics of governor valve opening with respect to rotation speed, and Fig. 10 shows conventional simulation results. The characteristic diagram, FIG. 11, is a block diagram showing the principle of the variable speed power generation system. Ex...excitation circuit, G1...variable speed machine, 62~G,
...Power transmission line, C...Control command unit, T...Operation end,
1... Stator. 2... Rotor, 3... Full frequency detection section, 4...
・Frequency/voltage converter, 5a to 5C... stator a,
b. C phase winding, 6a to 6c... Rotor a, b, a phase winding, 7... Rotation speed measuring section, 10... Power system, 1'1
... Rotation speed detector, 13 ... Water turbine, 14 ... Servo system, 15 ... Delay circuit, 16 ... Secondary winding phase angle calculation unit, 17 ... Secondary winding excitation Amount setting section, 18...
Voltage adjustment section. 19... Current transformer, 20... Voltage transformer, 21.
・・Active power calculation unit, po, po engineering 1POa ・・Power control command value, N−・・Speed, 23 a, 23 b
, 23 c - phase shift section, 25... optimal valve opening calculation section, 40... detection section transfer function. 41.42, 46.48... Arithmetic section, 43... Proportional control section, 44... Integral control section, 45... Feedback control section, 47... Limiter.

Claims (1)

[Claims] 1. In the operation control method of a variable speed pumped storage power generation system in which a wound induction machine is operated in response to fluctuations in the system load, the deviation between the target value of the system frequency and the actual system frequency is controlled by power control during pumping operation using governor control. A method for controlling the operation of a variable speed pumped storage power generation system, comprising converting the power control command value into a command value, and controlling the rotation speed of the induction machine based on the converted power control command value.