JPH0226710B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an operating system for a variable-speed pump-turbine generator-motor, and in particular, the present invention relates to an operating method for a variable-speed pump-turbine generator-motor, and in particular, to maintain a constant frequency in a power system by variable-speed control by alternating current excitation of a secondary winding. The present invention relates to an operation method for a variable speed pump turbine generator motor having a plurality of units, which is suitable for controlling.

[Background of the invention]

553 Variable speed operation characteristics of large capacity synchronous motors In the field of large capacity, as described in the 1981 National Conference on Electrical Engineers, 553 Variable Speed Operating Characteristics of Large Capacity Synchronous Motors
Thyristor motors with high reliability and low tri-ripple have been applied. However, there is no pumped storage power generation system that performs highly efficient and highly reliable variable speed control by replacing the synchronous machine with a large-capacity wound induction generator motor.

In the operation of a variable speed pump-turbine generator-motor using a winding type induction generator, when the power system frequency is ₁ and the rotor is slipping S, the induced electromotive force induced in the secondary winding is at a frequency of slip frequency S ₁ . Therefore, the frequency at which the secondary winding is AC excited is also generated by the cycloconverter to create a slip frequency S ₁ that matches this, and three-phase AC excitation of the secondary winding is performed.
The slip of an induction generator motor is, at synchronous speed,
Since the slip S=0, the slip frequency becomes
S ₁ =1 ₁ =0 (direct current), and direct current flows from the cycloconverter to the secondary winding. Therefore, current flows in a concentrated manner through the thyristor of a particular phase of the cycloconverter, and as a result, the average current of the thyristor increases compared to normal times, resulting in current concentration. A variable-speed pump-turbine generator-motor using a cycloconverter configured with a thyristor with an allowable average current capacity that can withstand this current concentration can be operated at synchronous speed, but the installed capacity is enormous and requires expensive equipment. In order to achieve this, the allowable average current capacity of the thyristor is reduced, and speed control is performed within a range (hereinafter referred to as a prohibited zone) in which steady operation is not performed near the synchronous speed. The existence of the dream stop zone causes a problem with regard to constant frequency control of the power system to the extent that power adjustment is impossible.

[Purpose of the invention]

SUMMARY OF THE INVENTION In order to compensate for the above-mentioned drawbacks, it is an object of the present invention to provide an operation method that improves the constant frequency controllability of the system in a pumped storage power generation system configured with a plurality of variable speed pump turbine generator motors.

[Summary of the invention]

Conventional pumped storage power plants are generally composed of multiple synchronous generator motors, but during power generation operation they can control the frequency of the power grid at a constant rate, but during pumped storage operation they only receive input power from the power that is uniquely determined by the pumping height. Constant frequency control cannot be performed during operation. If the synchronous generator-motor is replaced with one variable-speed pump-turbine generator-motor, and if the variable-speed pump has a dream stop determined by the installed capacity of the cycloconverter, as described above, the frequency constant control of the entire system will be impossible. There are areas where this cannot be done. Therefore, by replacing it with multiple variable-speed pump-turbine generator-motors, constant frequency control over a wide range can be achieved.

[Embodiments of the invention]

In the following, an example of this power generation will be explained based on variable speed pump operation using an example in which two variable speed pump water turbine generator motors IM1 and IM2 are connected to a power grid 9 with a rated frequency of ₁ as shown in Figure 1. explain. A three-phase alternating current is applied to the electric power system 9 by the stator 1, and the rotation speed of the rotor 2 decreases due to the slip S.
When the motor is rotating with a motor, an induced electromotive force with a slip frequency of S ₁ is generated. The rotor 2 is
The pump 7 is directly connected to a speed detector 6 and a position detector 11. The speed detector 6 detects the rotational speed N, and the position detector 11 normalizes the induced voltage of the rotor 2 to determine the slip frequency _S1. Then, the secondary excitation reference signal PS is detected. The gate trigger pulse of the cycloconverter 3 that excites the rotor 2 with three-phase AC excitation at the slip frequency is sent from the automatic phase shifter 4, and the control phase shifter α uses the control calculation unit 5 to convert the power of the grid into electric power. The power detection values Pd ₁ , Pd ₂ detected by the converter 12 and the power command of the command calculation unit 10 are
The control angle α is calculated by detecting the deviation from PM ₁ or PM ₂ , performing constant power control, and giving a phase amplitude to the reference signal detected by the position detector 11. The command calculation unit 10 commands input power to each variable speed pump motor so that the frequency of the power system becomes constant. Figure 2 shows variable speed pump motor 1.
The relationship between the input power P from the system and the head H per platform is shown. The shaded area indicates pump operation.
This shows the range of power that can be adjusted to perform constant frequency control. In FIG. 2, the range from N+S to No to N-S in the vicinity of the synchronous speed No is a prohibited zone in which steady operation is impossible, which is determined by the installed capacity of the cycloconverter. Upper limit P _U and lower limit P _L of the forbidden band power value
is determined by the lifting height H. Now, as shown in the second diagram, when two variable speed pumps IM ₁ and IM ₂ are operating at a head of head H ₁ and input power P ₁ from the grid, the load on the grid is light. Assuming that the required input power command Pref to the two variable speed pump motors changes to Po as the frequency increases,
The sum of the input power of the two variable speed pumps at that time is the third
As shown in the figure, the input power is distributed in the prohibited band when rising.

Figure 3 shows the power required from the grid. If the above-mentioned prohibited band exists in the variable speed pump motor, the sum of the inputs of multiple variable speed pump motors should match the power requested from the grid. Distributes the power command of the variable speed pump motor. variable speed pump
When both IM ₁ and IM ₂ are operated above the lower limit value _PL of the forbidden zone, the same power command of PM1=PM2 (1) is given. When the lower limit P _L of the prohibited zone is reached at time t ₁ and the power command Pref from the grid further increases, one variable speed pump motor (IM ₁ ) is switched off to prevent it from operating in the prohibited zone where steady operation is impossible. Give a power command PM1 that quickly moves to the forbidden band upper limit value P _U. On the other hand, IM ₂ is given a command such as PM2=2Pref−PM1 (2) to match the power requirement Pref of the grid, and reduces the input power. At time t ₂ , IM ₁ reaches the upper limit of the prohibited band P _U , and between times t ₂ and t ₃ , PM1 = Pref + P _U - P _L ... (3) PM2 = Pref - P _U + P _L ... (4) power is distributed. The power distribution during operation during this period is the operation method when the system required power Pref is within the forbidden band of the variable speed pump motor. After that, the system required power Pref increases and reaches the lower limit of the prohibited band of the power command of the variable speed pump motor IM2 at time _t3.When the system required power Pref further increases, the variable speed pump motor IM2 is prohibited. In order to enter the belt,
The command value PM2 is immediately given from the lower limit value P _L to the upper limit value P _U by the command to pass through the prohibited zone. The command value of IM1 at that time is given by PM1=2Pref−PM2...(5), and at time _t4 , the command becomes Pref/2=PM1=PM2...(6). Thereafter, the same command is given using equation (6) to increase the required power Pref, and the final target is reached. According to this embodiment, the command calculation unit 10
By providing a
This has the effect of improving controllability of constant system frequency. Here, we have explained two variable speed pump motors as an example, but it is also fully effective in the case of multiple units.If the penstock is common as shown in Fig. 5, variable speed pump motors A and B are By giving the same command and also giving the same command to C and D, assuming that A and B are one machine and CD as one machine, and performing the command calculation for the above two machines,
Allows for more stable driving. Although the above description has been made regarding the variable speed pump motor, the present control system can be implemented by changing the sign of the command value during power generation operation.

〔Effect of the invention〕

According to the present invention, even in a variable speed pump turbine generator/motor that has a range in which steady operation is not possible determined by the installed capacity of the suncro converter, by creating a system with multiple units and distributing power commands,
The power adjustment range is wide and connected, and the controllability to keep the grid frequency constant is improved, so there is an effect of stabilizing the grid frequency.

[Brief explanation of drawings]

Figure 1 is a system configuration diagram of the variable speed pump turbine generator/motor, Figure 2 is the operating range of the variable speed pump motor, Figure 3 is the required power for the system, Figure 4 is the output of the command calculation unit, and Figure 5 is the number of units. variable speed pump turbine generator motor system. DESCRIPTION OF SYMBOLS 1... Stator, 2... Rotor, 3... Cycloconverter, 4... Automatic phase shifter, 5... Control calculation unit, 6... Speed detector, 7... Water turbine, 8...
Governor, 9...Power system, 10...Command calculation unit,
11...Position detector, 12...Power converter, Pref
...Required power for the system, PM1, PM2...Power command for each variable speed pump turbine generator/motor, H...Height,
No...Synchronous speed, Ns _t , Ns...Prohibited zone speed limit,
P _U ... Upper limit of prohibited band power, P _L ... Lower limit of prohibited band power.

Claims (1)

[Claims] 1 In a variable-speed pumped storage power generation system consisting of a pump-turbine equipped with a cycloconverter that excites the secondary winding of a winding induction generator-motor with alternating current, the cyclo-converter equipment can be improved by operating multiple variable-speed pump-turbine generator-motors. A variable-speed pump-turbine generator-motor, characterized in that it is equipped with a command calculation unit that distributes power commands for a plurality of variable-speed pump-turbine generator-motors in a system in which there is a range in which steady operation is not possible near the synchronous speed determined by the capacity. Driving method.