JPH0568959B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a control device for a variable-speed pump-turbine generator-motor, and in particular, the present invention relates to a control device for a variable-speed pump-turbine generator-motor, and particularly to a control device that uses a wound-type induction machine as the generator-motor and excite the secondary winding with alternating current. The present invention relates to a control device for variable speed control.

[Background of the invention]

Variable-speed pumped storage power generation systems are being developed with the aim of efficiently controlling the rotation speed of pump-turbine generator motors that generate pumped storage power generation (frequency control) according to the required power of the system and static head values. . Conventionally, a synchronous motor was used as a large-capacity variable-speed pump-turbine generator-motor, and there was a thyristor motor that controlled it with a thyristor (Eto, Ito et al., "Variable-speed operation characteristics of large-capacity synchronous motors", National Institute of Electrical Engineers of Japan) (See 1981, 553). on the other hand,
Recently, a motor using a wound type large-capacity induction generator motor has been developed.

FIG. 8 shows, as an example of motor operation, the principle of torque generation in variable speed control using a method in which a wound induction generator-motor is secondarily excited. A rotor 3 is located within the stator 1 via an air gap 2, and the speed of this rotor 3 is assumed to be ω ₂ . Now, when the rotor speed ω ₂ is slower than the speed ω ₁ of the rotating magnetic field Φ generated by the primary current, that is, below the synchronous speed, the slip S = (ω ₁ −
Assuming that ω ₂ )/ω ₁ is positive (ω ₁ > ω ₂ ), the secondary winding has a frequency that is the difference between the speed ω ₁ of the rotating magnetic field Φ and the speed ω ₂ of the rotor 3, and An induced voltage 4 of the polarity shown by the small circle is generated, a current 5 of the same polarity flows, and a torque T is generated in the direction of the arrow.
At this time, ω ₁ −ω ₂ =ω ₁ −(1−S)ω ₁ =Sω ₁ =2πS ₁ (1) Therefore, the frequency of the induced voltage 4, that is, the slip frequency, becomes S ₁ . Next, consider a case where the rotor 3 has a synchronous speed S=0 (ω ₂ =ω ₁ ). At synchronous speed, the induced voltage 4 becomes zero, so if this continues, the secondary current 5 will not flow and no torque will be generated. However, by applying secondary excitation using a cycloconverter and passing a current with the same polarity as the current 5 in FIG. 8, torque T is generated and operation at synchronous speed becomes possible. The excitation frequency at this time is from S=0.
S ₁ =0, resulting in DC excitation, but this causes problems as described later in relation to the current capacity of the cycloconverter. Next, in the synchronous state, if the amount of current flowing through the secondary winding is increased in the same polar direction as in FIG. 1, the rotor 3 can rotate at a speed ω ₂ greater than the synchronous speed ω ₁ . At that time, the induced voltage 4 is reversed and has a polarity as shown in FIG. At this time, since the slip frequency is S<0, S ₁ <0, and the excitation frequency is in the opposite direction to the rotor speed ω ₂ . That is, at system frequency ₁ , the rotor frequency is (1-S) ₁ , the example slip frequency is S ₁ , and ₁ = (1-S) ₁ +S ₁ ...(2) holds true. By changing the secondary excitation voltage below the synchronous speed and above the synchronous speed,
A secondary current flows due to the voltage difference between the secondary induced voltage of the induction machine and the excitation voltage of the secondary winding, and torque is generated, allowing variable speed control.

The above is the principle of torque generation in the operation of the electric motor of an induction machine. When operating an induction machine as a generator, a cycloconverter is used to apply secondary excitation to the rotor to generate torque, and the rotor is rotated by hydraulic power against this torque to generate electricity. . Therefore, in this generator operation, as well as in the electric motor operation, a problem occurs with DC excitation when the slip S is near zero.

By the way, the problem when the secondary excitation becomes direct current with the slip S being almost 0 will be explained. Assuming that the alternating current side of the cycloconverter is three-phase alternating current, the current flowing through the thyristor of one arm forming the cycloconverter is as shown in the shaded area in FIGS. 10 and 11. Figure 10 shows the case where the frequency of the output current of the cycloconverter is relatively large, and the average on-current of the thyristor in one arm I _AV is I _AV = 1/3×1/T∫ ^T/2 ₀ √2I _G sinS
ω ₀ tdt=0.15I _G ……(3). However, when the frequency becomes low as shown in Figure 11, it can be regarded as almost direct current, and the average on-current I _AVd when this becomes direct current is I _AVd = 1/3 × √2 I _G = 0.47 I _G ... (4) becomes. If a cycloconverter is configured using a thyristor with a permissible average current capacity that allows the current expressed by equation (4) to flow through one arm, operation is possible even when the secondary excitation frequency, that is, the slip frequency, is 0 as described above. However, the larger the variable speed pumped storage power generation system becomes, the larger the installed capacity of the cycloconverter becomes. For this reason, restrictions are placed on the output current frequency of the cycloconverter, that is, the slip frequency of the induction machine, and a frequency range (this is called a forbidden band) that is only allowed to pass transiently is provided. Steady operation is not performed in this forbidden band, and therefore the cycloconverter can be configured with a thyristor that can flow the current of equation (3). However, a method of operating an induction generator motor that takes this prohibited zone into account has not been established.

[Purpose of the invention]

An object of the present invention is to solve the problems of the prior art described above, and to provide a control device for a variable speed pump-turbine generator-motor that can operate a cycloconverter stably and safely in various automatic frequency control operations during power generation and water pumping. This is what we provide.

[Summary of the invention]

In automatic frequency control operation during power generation and pumping, the speed command value passes through the prohibited zone and reaches steady operation due to input voltage increase or decrease commands, or when the speed exceeds the prohibited zone due to a system accident, etc. When the forbidden zone is reached, acceleration or deceleration control of the induction machine is performed so that the induction machine quickly escapes from this forbidden zone.

[Embodiments of the invention]

FIG. 1 shows a variable speed pump-turbine generator-motor system using the method of the present invention.
It is excited by The rotation speed of the variable speed pump turbine 8, that is, the rotation speed _Nr of the induction machine 6, is determined by the speed detector 1.
The secondary induced voltage of the inductor 6 is detected by the position detector 15. Power P of power system 16 is detected by power converter 18 . The command value calculation unit 17 receives a given system required power command P ₀ (this command is used to determine how many MW the output power should be during generator operation, for example).
In the case of electric motor operation, for example, it is a command that tells how many MW of surplus electricity to use for pumping water. ) and the detected value H of the water level difference, calculate the speed command value N ₀ at which the pump turbine 8 has the highest efficiency,
The excitation amount calculation unit 9 outputs a guide ben opening command for the governor 19 based on the deviation between this N ₀ and the speed N _r detected by the speed detector 14, and also outputs a guide ben opening command for the governor 19 based on the difference between this N 0 and the speed N r detected by the speed detector 14. The amount of excitation is calculated from the deviation from the command P ₀ and the automatic phase shifter 13 is controlled via the adder 12 .

The acceleration/deceleration compensation unit 10, which is a feature of the present invention, is a calculation unit that provides acceleration compensation or deceleration compensation when the speed command N ₀ changes by passing through the above-mentioned forbidden zone, and its operation flowchart is shown in the second section. As shown in the figure. In the figure, in step 100, a speed command value _N0 , a detected speed value _Nr , and a water level difference H are taken in. Now induction machine 6
As shown in FIG. 3, the variable speed range of the cycloconverter 7 is the shaded range with respect to the detected value of the water level difference, that is, the static head H and the grid power P.
The forbidden zone N ₊ to N _- determined from the capacity limit changes with the static head difference H as shown in the figure. Therefore, in step 101, it is determined whether the speed _{Nr just} input is within the prohibited zone corresponding to the static head difference H, and if it is within the prohibited zone, the compensation value according to the static head difference H is exemplified in Fig. 4. Read from the ROM table (stored in the acceleration/deceleration compensator 10). Also, in step 103, the read speed command N ₀ and the detected speed N _r are compared, and N ₀ > N _r
The sign of the compensation value ΔS is determined so that acceleration compensation is performed when N ₀ <N _r , and deceleration compensation is performed when N 0 <N r. Then, in step 107, the compensation value ΔS is output. step 101
If the speed N _r is outside the prohibited zone, it is determined in step 104 whether the speed command value N ₀ passes through the prohibited zone, and if it does, the compensation value ΔS to be given outside the prohibited zone is illustrated in FIG. In step 106, the same sign as in step 103 is determined, and in step 107, the controlled compensation ΔS is output. When the speed command does not pass through the prohibited zone, ΔS is set to 0 in step 108, and no compensation is performed. The compensation value ΔS output in this way is added to the output of the excitation amount calculation section 9 by the adder 12 in FIG. 1, and is applied to the phase shifter 13.

The operation of the embodiment of the present invention including the acceleration/deceleration compensator 10 as described above is as follows. For example, suppose that a command is given to increase the grid power from P _a to P _d in a state of static head H ₁ as shown in FIG.
If acceleration/deceleration compensation control is not performed at this time, the sixth
As shown in the figure, the power will increase with time t along the straight line abcd. time here
t _ad indicates the power change time set for system operation. Further, time t _bc is the time for passing through the forbidden zone without acceleration compensation, and if the maximum time allowed for passing through the forbidden zone is Δt, then if t _bc >Δt, it exceeds the allowable range of the cycloconverter. Therefore, when the speed N _r is within the prohibited zone, acceleration compensation control is performed, and the time required to pass through the prohibited zone is set to t _ef (<Δt). However, the power change time t _ad
Since a large deviation from the range will disturb the power system, deceleration compensation is performed outside the prohibited zone. Therefore, as time t passes, the grid power P changes as shown by the broken line in Figure 6.
It changes like aefd. Of course, these acceleration/deceleration compensation amounts are read out from the ROM as a function of the static head difference H, as explained in FIG. FIG. 7 corresponds to FIG. 6, and the vertical axis represents the speed N.
It also shows how the vehicle accelerates within the prohibited zone and compensates for deceleration outside the prohibited zone.

According to this embodiment, automatic frequency control operation can be performed that matches the power change time during operation by performing acceleration/deceleration compensation according to the static head, without having to set the power capacity of the excitation cycloconverter particularly large. This can be done safely, and even if the speed reaches the prohibited zone due to a sudden change in load due to a system accident, etc., stable operation can be achieved as well. In addition, although the above embodiment was explained as a case of variable speed pump operation,
It can also operate effectively in variable speed power generation operation. However, in that case, stability and controllability are improved by using acceleration/deceleration compensation as a compensation value for the guide vane opening command of the governor.

〔Effect of the invention〕

As described above, according to the present invention, by performing acceleration/deceleration compensation control, even when the variable speed pump turbine generator/motor has a large capacity, the capacity can be adjusted without increasing the installed capacity of the power converter. Since the grid frequency constant control operation can be performed stably within the compatible range without disturbing the power grid, it has great effects in terms of economy and safety.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a flowchart showing the operation of the acceleration/deceleration calculating section, and FIG.
The figure is an explanatory diagram of the variable speed range, Figures 4 and 5 are diagrams showing examples of ROM characteristics that store compensation values for static head, and Figures 6 and 7 are concrete explanations of acceleration/deceleration compensation. 8 and 9 are explanatory diagrams of the operation of the induction machine, and FIGS. 10 and 11 are explanatory diagrams of the thyristor average current. 6...Induction generator motor, 7...Cycloconverter, 8...Variable speed pump water turbine, 9...Excitation amount calculation section, 10...Acceleration/deceleration compensation calculation section, 12...Adder, 13...Phase shifter , 14... speed detector, 18
...Power converter, 19...Governor.

Claims (1)

[Scope of Claims] 1. A cycloconverter that excites a wound-type induction machine connected to a pump-turbine of pumped storage power generation and used as a variable-speed pump-turbine generator-motor, and a speed detector that detects the actual rotational speed of the induction machine. a command value calculation unit that calculates a speed command value of the induction machine from the system element power command and static head; and a command value calculation unit that calculates a guide ben opening command to be given to the governor of the pump water turbine from the speed command value and the actual rotation speed; In a control device for a variable speed pump-turbine generator-motor, the controller includes an excitation amount calculation unit that provides the cycloconverter with an excitation amount determined from a deviation between the actual grid power and the grid requested power command, The frequency range in which the cycloconverter excites the induction machine in a DC state is defined as a prohibited band, and when the rotational speed of the induction machine corresponding to the output current frequency passes through the prohibited band, the actual rotational speed is When the actual rotational speed is outside the forbidden zone, a compensation value that is obtained as a function of the static head and accelerates the rotational speed of the induction machine is obtained, and when the actual rotational speed is outside the forbidden zone, the compensation value is calculated as a function of the static head. Acceleration/deceleration compensation is provided to the cycloconverter by determining a compensation value that is obtained as a function and decelerating the rotational speed of the induction machine, and adding the determined compensation value to the excitation amount output by the excitation amount calculation section. 1. A control device for a variable speed pump water turbine generator/motor, characterized in that a control device for a variable speed pump water turbine generator motor is provided.