JP3834356B2 - Variable speed hydropower plant - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable speed power generation or variable speed pumping plant that operates at an arbitrary rotational speed according to the operating state and operates in synchronization with the power system frequency, and in particular, a surge tank is installed in the upper pond side or lower pond side waterway. The present invention relates to a variable speed hydraulic power plant having the same.
[0002]
[Prior art]
The variable speed hydraulic power plant can perform the high-speed power control much faster than the conventional hydraulic power plant using the flywheel effect. For this reason, in order to improve the quality of the power system, a variable speed plant is expected to have automatic frequency control (AFC) and governor-free control with higher gain than before.
[0003]
However, the conventional plant having a surge tank has the following problems. That is, in general, the natural vibration period of the AFC control loop is close to the natural wave period of the surge tank, the surge tank water level is abnormally excited and the amplitude is abnormally enlarged, which may cause problems such as overflow.
[0004]
In other words, there is a limitation in the prior art on sufficiently increasing the AFC control gain of the variable speed plant due to this limitation.
[0005]
Therefore, in the past, assuming that the surge tank resonates due to repeated AFC control, raising or lowering the surge tank or rapidly expanding the surge tank cross-sectional area near the upper and lower limit water levels so as not to cause problems. Or devised a surge tank structure. However, the surge tank side cost was extremely high.
[0006]
The above problem is more serious particularly when a surge tank is provided in the upper pond side or the lower pond side water channel, and the surge tank side water channel is branched and shares the surge tank side water channel with other variable speed hydraulic machines. become. This is because the resonance problem becomes more serious when a plurality of variable speed hydraulic machines perform AFC control all at once.
[0007]
In addition, in a conventional pumped-storage power plant using a synchronous machine, input control was practically impossible during pumping operation at night. This is because the pump input hardly changes even when the guide vane opening is changed, and there is substantially no adjusting means other than the rotational speed. However, variable speed machines have appeared, and it has become possible to contribute to AFC control and governor-free control of the power system even in the pumping mode. Accordingly, there is a possibility that surge tank resonance occurs even in the pumping mode.
[0008]
In addition, even with conventional synchronous machines, there was a possibility of abnormal expansion of surge tank water level fluctuations. For example, when multiple pumps are started with a certain time difference, the time difference is relatively short (so that the surge tank water level fluctuation does not sufficiently attenuate during this time) and is an integral multiple of the natural frequency of the surge tank. is there. In this case, the subsequent starter is in a relationship of accelerating the surge tank water level fluctuation. As countermeasures, there are methods such as increasing the surge tank capacity, sufficiently increasing the time difference, and starting at a timing that does not promote fluctuations in the surge tank water level. However, the latter two proposals are nothing more than a plant that is not easy to use except that it restricts the power supply and demand of the power system.
[0009]
Therefore, in the prior art, there was an operation know-how that required a compromise with the surge tank like the above-described countermeasure for the time difference pumping, but there was no idea of actively controlling this.
[0010]
[Problems to be solved by the invention]
In the variable speed hydraulic power plant having the surge tank as described above, an object of the present invention is to enable stable control even when the surge tank is designed to have the minimum required economic design and reduce civil engineering costs. As long as is within the specified range, AFC control and governor-free control are fully performed without restriction to maximize the features of the variable speed machine.
[0011]
The variable speed hydraulic machine has a wider operating range than the constant speed hydraulic machine, AFC control is possible over a wider range, and higher speed control is possible, so more effective AFC control and governor-free control are expected. These functions can be fully exhibited even when a surge tank is provided.
[0012]
[Means for Solving the Problems]
In order to achieve the above purpose, the upper pond side or lower pond side waterway has a surge tank, and it is operated at an appropriate rotation speed according to the operating state while adjusting the output or input in response to an electric power command given from the outside. The variable speed hydraulic power plant is equipped with a water level detector that detects the surge tank water level, and a control arithmetic unit that outputs a signal that suppresses and controls fluctuations in the water level of the surge tank in response to the detection signal of the water level detector. It is provided with an input switching circuit for completely selecting and switching a normal operation command (power command) and a control arithmetic unit output signal or switching so that one of them substantially overrides the other. It is a thing.
[0013]
Thus, in the present invention, surge tank water level fluctuation suppression control is actively performed using a variable speed machine. In particular, the surge tank water level fluctuation suppression control is accurately performed as necessary while monitoring the surge tank water level. In this case, it is necessary to switch from normal AFC control to surge tank water level suppression control or vice versa, but the switching method of completely turning off one and turning on the other, and increasing one gain, There is also a method of switching substantially by a method of reducing the time constant and a method of shortening one time constant and lengthening the other.
[0014]
When multiple hydraulic plants are installed by branching the water channel on the surge tank side, especially when multiple variable-speed hydraulic plants are installed, the surge tank water level is at least one of the variable-speed plants. A fluctuation suppression control function is provided.
[0015]
As a result, the size of the surge tank can be minimized. That is, the surge tank can be prevented from performing an uneconomical design based on natural frequency excitation.
[0016]
And the water level fluctuation | variation which the other machine which does not comprise surge tank water level control generate | occur | produces is controlled by the variable speed machine provided with the surge tank water level fluctuation | variation control means. In other words, the economic design of the surge tank itself is realized by allocating a part of the safety valve function of the surge tank to the variable speed machine that can respond at high speed and operate in a wide range.
[0017]
When the surge tank water level is greater than or equal to a predetermined value or the fluctuation range is greater than or equal to a predetermined value, surge tank water level control is applied to give priority to suppression of surge tank water level fluctuation. Thereby, since this protection is ensured, it is usually possible to give priority to the normal operation function such as AFC and to maximize the features of the variable speed.
[0018]
Moreover, since the response of the variable speed hydraulic machine is higher than that of the constant speed machine and a wide range of output / input adjustment can be performed, the surge tank water level control more effective than the constant speed machine is possible.
[0019]
By the way, various measures for suppressing the surge tank water level fluctuation are considered as follows:
(A) First, a PID that controls the guide vane opening degree and rotation speed of the variable speed plant in a direction in which the surge tank water level fluctuation is suppressed in consideration of the direction of the surge tank water level fluctuation, the water level itself, the water level fluctuation speed, etc. A passive control circuit is provided.
[0020]
(B) Considering the direction of surge tank water level fluctuation, water level itself, water level fluctuation speed, etc., the guide vane opening and rotation speed of the variable speed plant so that a surging suppression wave having the opposite sign to that of the surge tank water level fluctuation is generated. An active control circuit for controlling the above is provided.
[0021]
(C) Surge tank water level fluctuation suppression as described above is normally excluded or substantially excluded, and is automatically activated only when necessary. Specifically, the case where the surge tank water level becomes a predetermined value or more, or the fluctuation range becomes a predetermined value or more can be considered.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 3 shows an example of a variable speed hydraulic power plant having a surge tank targeted by the present invention.
[0023]
The hydraulic plants 103A and 103B are both variable speed hydraulic machines, particularly variable speed pumped storage power generation plants. The following embodiment will be described as an example. However, if one of the hydraulic power plants sharing the pipeline is basically a variable speed type, this The object of the invention can be achieved. In a steady state, the effective head (power generation mode) or head (pumping mode) acting on these plants is determined by the difference between the upper pond water level EL1 and the lower pond water level EL2. However, transiently, there is a difference between the flow rate of the hydraulic iron pipe 105 and the flow rate of the water conduit 107, so that the water level EL3 of the surge tank 106 fluctuates up and down.
[0024]
For example, if the variable speed pumped storage power plants 103A and 103B repeatedly increase or decrease the input in the natural period of the surge tank by the same AFC control command during the pumping operation, the fluctuation range of the surge tank water level EL3 will increase, and finally the surge tank top water level Overflows beyond ELA. However, overflow is not generated by providing the variable speed machine 103A with the water level control function. In this function, the water level control is activated when the surge tank water level shown in FIG. 4 reaches ELX lower than ELA, and the variable speed machine 103A is switched from the AFC control priority to the surge tank water level control priority, and the rotation speed is automatically set. The pumping flow rate decreases. As a result, the surge tank water level fluctuation is attenuated as shown in FIG.
[0025]
FIG. 1 shows a first embodiment of a variable speed hydraulic power plant having a surge tank water level control function, which will be described below.
[0026]
The abnormal water level determination unit 33 that receives the water level detection signal 32 detected by the surge tank water level detector 31 outputs a signal corresponding to the water level exceeding the water level ELX described above. Note that when the water level exceeds ELX, the surge tank water level fluctuation suppression control ON command unit 35 operates, and the control signal selection circuit 48 performs control selection to be prioritized. That is, at this time, the mode is switched to the surge tank water level control priority mode. The surge tank water level fluctuation suppression control circuit 46 outputs the surge tank water level control signal 47 in response to the abnormal water level signal 34, that is, the water level signal exceeding the water level ELX. Thus, the composite power command 29 is substantially switched from the normal operation power command 49 to the surge tank water level control signal 47 by the control signal selection circuit 48. Then, the combined power command 29 becomes a final variable speed pumped-storage power generation command through the power command lower limit setting device 30. In this way, the variable speed machine power command 21 that is finally input to the variable speed machine is determined.
[0027]
Apparatuses 1 to 23 show the configuration of a known variable speed pumping plant.
This is the same as that disclosed in 212774 (control device for variable speed pumping device).
[0028]
This embodiment is an example showing a device configuration in the case where a winding induction machine having a primary winding 4 and a secondary winding 5 is used as a variable speed electric motor. The primary winding 4 of the winding induction machine is connected to the power system 1, the secondary winding 5 is connected to the AC exciter 7, and the input of the induction machine is input to the variable speed machine power command 21 by the AC exciter 7. Increase or decrease depending on The rotation state of the induction machine is detected by the speed detector 17 and input to the adders 19 and 20.
[0029]
FIG. 2 shows a specific example of the surge tank water level fluctuation suppression control circuit 46 and a specific example of the control signal selection circuit 48 of the embodiment of FIG. The water level adjustment rate circuit 43 is a restoration circuit for providing a localization property between the abnormal water level signal 34 and the surge tank water level control signal 42.
[0030]
The integration operation circuit 39 continues the integration operation until the surge tank water level control signal 42 reaches a target value corresponding to the abnormal water level signal 34 in consideration of the water level adjustment rate circuit 43. The proportional calculation circuit 38 is a circuit for reducing a response delay of the output surge tank water level control signal 42 with respect to the abnormal water level signal 34 that is an input. The control signal selection circuit composed of the devices 24 to 28 is a first-order lag element, and the power command response speed adjusting unit 26 that performs the integration operation is an integration element, and the gain is the surge tank water level control ON signal. When 45 comes, it is automatically reduced. As a result, the response time constant of the response speed adjusted power command 27 with respect to the normal operation power command 49 becomes significantly longer, and the response speed adjusted power command 27 is effectively maintained as it is. In this way, the combined power command is substantially influenced by the surge tank water level control signal 42, and the variable speed pump is put into the surge tank control mode.
[0031]
【The invention's effect】
It eliminates the waste of surge tank design based on the natural period vibration of the surge tank and enables economical design.
[0032]
At the same time, it is possible to eliminate unnecessary AFC control suppression, restriction, etc. on the premise of the natural period excitation of the surge tank, and to fully exhibit the high-performance AFC and high-speed governor-free function unique to the variable speed machine.
[Brief description of the drawings]
FIG. 1 is a first example of a variable speed hydraulic power plant having a surge tank water level control function.
FIG. 2 shows a second example of a variable speed hydraulic power plant having a surge tank water level control function.
FIG. 3 shows an example of a variable speed hydraulic power plant having a surge tank.
FIG. 4 is an operation explanatory diagram of surge tank water level control.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electric power system, 2,103 ... Pump turbine, 3 ... Main shaft, 4 ... Primary side winding, 5 ... Secondary side winding, 6 ... Primary side of variable speed machine, 7 ... AC excitation apparatus, 8 ... Guide vane Opening control device, 9 ... Restoration, 10, 14, 19, 20, 24, 28, 36 ... Adder, 11 ... Output of adder 10, 12 ... Actual power detection signal, 13, 29 ... Composite power command, 15 ... output of adder 14, 16 ... AC excitation of secondary winding, 17 ... speed detector, 18 ... rotational speed command function generator, 21 ... variable speed machine power command, 22 ... proper rotational speed command, 23 ... actual , 25, 37 ... deviation signal, 26 ... power command response speed adjustment unit, 27 ... response speed adjusted power command, 30 ... power command lower limit setter, 31 ... surge tank water level detector, 32 ... detection signal as above 33: Abnormal water level detector 34: Abnormal water level signal 35: Surge tank water Fluctuation suppression control ON command device, 38 ... proportional calculation circuit, 39 ... integral calculation circuit, 40 ... proportional calculation circuit output, 41 ... integral calculation circuit output, 42, 47 ... surge tank water level control signal, 43 ... water level regulation rate circuit, 44 ... Water level arbitration rate circuit output, 45 ... Surge tank water level control ON signal, 46 ... Surge tank water level fluctuation suppression control circuit, 48 ... Control signal selection circuit, 49 ... Normal operation power command, 101 ... Shimoike, 102 ... Discharge channel 104 ... Hydraulic iron pipe branch pipe, 105 ... Hydraulic iron pipe, 106 ... Surge tank, 107 ... Water conduit, 108 ... Upper pond, EL1 ... Upper pond water level, EL2 ... Lower pond water level, EL3 ... Surge tank water level, ELA ... Surge tank Top water level.

Claims (2)

In a variable speed hydropower plant with a surge tank in the upper pond side or lower pond side waterway,
A variable speed hydraulic power plant in which a pump turbine is operated at an appropriate rotation speed according to an operating state while adjusting an output or input in response to a normal operation power command,
A water level detector that detects the surge tank water level, a surging water level fluctuation suppression control circuit that outputs a signal that suppresses and controls fluctuations in the water level of the surge tank in response to a detection signal of the water level detector, and the pump turbine is pumped mode operation, based on the operation of the surging water level fluctuation suppression control oN command unit, and a control signal selection circuit for switching the surge tank water level control priority mode from the normal operation for power command by an output signal of the surging water level fluctuation suppression control circuit, A variable speed hydraulic power plant , wherein a signal switched by the control signal selection circuit is input to a variable speed machine as a variable speed machine power command to adjust the rotational speed of the pump turbine . In a variable speed pumping plant with a surge tank in the upper pond side or lower pond side waterway,
A variable-speed pumping plant in which a variable-speed electric motor that drives a pump at an appropriate rotation speed according to an operation state is operated while adjusting an input in response to a power command for normal operation,
A water level detector that detects the surge tank water level, a surging water level fluctuation suppression control circuit that outputs a signal that suppresses the water level fluctuation of the surge tank in response to a detection signal of the water level detector, and a surging water level fluctuation suppression control A control signal selection circuit for switching to the surge tank water level control priority mode from the power command for normal operation based on the output signal of the surging water level fluctuation suppression control circuit based on the operation of the ON command device, and the signal switched by the control signal selection circuit Is input to the variable speed electric motor as an electric power command, and the rotational speed of the pump is adjusted.

Images