JPH07106080B2 - Variable speed generator control method - Google Patents

Description

The present invention relates to a control method for a variable speed generator, and more particularly to an automatic frequency control operation method for a generator capable of variable speed operation.

(Prior Art) For example, when the power demand exceeds the generated power (supplied power), the power system frequency decreases, and conversely, when the generated power exceeds the demand, the frequency increases. Therefore, it is necessary to change the load (electric power) of the water turbine that supplies the generated power in a constant cycle so that the generated power and the demand are balanced as much as possible. Since the conventional turbine has a constant synchronous speed, when varying the load, the guide vanes that adjust the water volume of the turbine are controlled to open and close at regular intervals to vary the water volume at regular intervals to adjust the load power of the turbine. Was there. That is, the conventional load adjustment has only a method of mechanically changing the guide vane which is the water amount adjusting device of the water turbine. In this case, the fluctuation range of electric power is usually 50 to 70% of the maximum output.

FIG. 6 shows how the load, the guide vane opening, the iron pipe water pressure, and the main engine rotation speed change with time in the conventional automatic frequency control operation and the like.

In the figure, in the case of automatic frequency control operation in which the load is required fluctuation range ΔP (KW) and the fluctuation cycle is f (second), the guide vane of the turbine is changed to a guide vane opening width corresponding to the required fluctuation range ΔP. The opening / closing control is performed at the cycle f (seconds), but in that case, the water pressure of the penstock fluctuates greatly due to the water hammer phenomenon due to the fluctuation of the water turbine flow rate. Also, if there is a surge tank in the headrace, the water level in this surge tank will also fluctuate significantly.

In such an operating state, if the unique vibration cycle of the water channel system and the load fluctuation cycle required for the automatic frequency control operation match, an unstable phenomenon occurs.

On the other hand, if the load fluctuation width ΔP is large, the water amount adjustment width is correspondingly widened and the opening / closing level of the guide vane is also large. It is generally known that the water pressure fluctuation due to a water hammer of a penstock becomes more severe as the flow rate fluctuation increases. In other words, if the load fluctuation range is wide, the water amount adjustment range will be large, and eventually the water pressure fluctuation will be large, and the water level fluctuation of the surge tank in the hydraulic conduit will be severe. For this reason, when the load fluctuation range is large, the water level fluctuation in the surge tank, that is, the surge tank fluctuation height becomes large, so a surge tank with a larger capacity is required, which significantly increases the cost of power plant construction. ,
In addition, when the load is reduced, there is a disadvantage that the vortex flow often generated in the draft tube, which is often seen during light load operation, causes the vibration to increase and the operating condition becomes unstable. Big restrictions were needed.

(Problems to be solved by the invention) When automatic frequency control operation is performed in a conventional hydroelectric power generation facility in this way, it is truly necessary due to constraints such as the conditions of the waterway system and the stability of the light load operation state of the water turbine. There is a drawback that load fluctuation and fluctuation cycle cannot be obtained.

The present invention has been made to eliminate the above-mentioned drawbacks in the background art, and is not limited by the conditions of the water channel system or the characteristics of the water turbine, and an automatic frequency control operation method that reduces water pressure fluctuations over a wide output range. The purpose is to provide.

[Structure of Invention]

(Means for Solving Problems) The control method of the present invention converts an AC-excited induction generator and an electrical frequency electrically generated by the generator by being electrically coupled to the induction generator into a system power supply frequency. In a control method for a variable speed power generator equipped with a cycloconverter, a detector that detects the current power generation output, a detector that detects the current excitation amount, and a calculation device that calculates the required excitation amount are installed in parallel. , The AC excitation amount of the induction generator is increased / decreased so as to correspond to a predetermined cycle and fluctuation amount required for the system to perform load increase / decrease control, and automatic frequency control operation is performed. To do.

(Operation) In the control method for the variable speed power generator of the present invention configured as described above, the AC excitation induction generator is supplied with the amount of excitation commensurate with the output by the AC excitation device, and is rotated at a predetermined rotation speed. , Its output is converted to a system frequency by a cycloconverter and transmitted.

Here, when the automatic frequency control operation command is issued, the change width of the load and the fluctuation cycle are determined, and then the power generation output and the excitation amount at that time are detected, and the excitation amount calculator calculates the AC excitation width, Based on this calculated value, automatic frequency control operation is performed by increasing / decreasing the AC excitation amount.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, running water is introduced from a penstock 1 to a water turbine 2,
The water turbine 2 is rotated with the energy of running water, and the AC excitation induction generator 3 directly connected to the turbine 2 generates electric power. The induction generator 3 is supplied with an excitation amount corresponding to the output and the rotation speed by the AC excitation device 4 and is operated at the operation rotation speed No. The output is converted into a system frequency by the cycloconverter and transmitted.

1 and 2, when the automatic frequency control operation command 10 is issued from the power supply command center, the load change width and the fluctuation cycle 11 are determined as command conditions. Next, the detector 6 detects 12 the current power generation output and the amount of excitation, and the excitation amount calculator 7 calculates the AC excitation widths + ε ₁ and −ε _2.
Then, based on the result, the automatic frequency control device 8 starts the automatic frequency control operation 4.

The above operation will be described based on a general hydraulic turbine characteristic diagram shown in FIG.

Fig. 3 shows that the guide vane openings A ₁ , A ₂ , and A ₃ are constant (A ₁ ＞ A ₂ ＞
A ₃ ) shows the relationship between the rotational speed N of the water turbine and the output P, and now the guide vane opening before the command is A ₂ ,
When the rotation speed of the water turbine is set to No, the output change width according to the command △
When the AC excitation width ± ε corresponding to p is changed according to the period determined by the amount of excitation corresponding to the load P ₀ , the turbine output changes from P ₁ to P ₂ . In this case, since the rotational speeds of the turbines corresponding to the turbine outputs P ₁ and P ₂ are N ₁ and N ₂ , the speed of the generator changes periodically between this N ₁ and N ₂ , but the cycloconverter The output to the system is controlled to a constant frequency by 5.

Therefore, according to the present invention, the predetermined automatic frequency control operation can be performed only by controlling the change of the AC excitation amount.

(Other Embodiments) In the above-mentioned embodiment, with the guide vanes fixed,
The output change width ΔP was obtained only by controlling the AC excitation amount.
It is difficult to deal with a demand for a slightly larger output ΔP than the power supply command center. This is the turbine output P shown in FIG.
This is because = 0 is a non-constrained speed operation state of the water turbine, and vibration and noise are greatly increased in the vicinity thereof, which is not preferable as an operation state.

In such a case, the output change width may be increased by the method shown in FIG.

In the same figure, when the automatic frequency control operation command 20 is issued and the output change width and the fluctuation cycle 21 are given, the current load P ₀ and the excitation amount ε are detected and the required fluctuation width is responded to as in the above embodiment. The excited amounts + ε ₁ and −ε ₂ are calculated, and the current guide vane opening A ₂ and the turbine rotation speed No are detected.

On the other hand, the turbine performance calculator 23 and the speed change width calculator 24, which are separately added, calculate the rotation speed change width limit values N ₁ and N ₂ with respect to the water turbine performance and the current rotation speed.

That is, the turbine performance calculator 23 and the speed change width calculator 24 are the fifth
As shown in the figure, it has the ability to calculate the turbine characteristics by inputting numerical values, and sets N ₁ and N ₂ with the frequency conversion ability of the cycloconverter as the limit value, and corrective opening + a ₁ and Calculate -a ₂ . Then, the excitation fluctuation amount (+ ε ₁ , −ε ₂ ) and the guide vane opening correction amount (+ a ₁ ,
-A ₂ ) and calculate the amount of excitation and the guide vane opening.
25 、 Automatic frequency control operation 26
I do.

As described above, when the load is increased from point P _{0 in} FIG. 5, the load is changed by increasing the excitation amount, and the rotational speed of the water turbine is sequentially changed from No to N _{1 according} to the load. This point
The guide vane opening correction amount + a ₁ may be controlled to open after N ₁ is detected, or the guide vane correction amount is gradually corrected at the same time as the rotation speed changes, and control is performed as indicated by the broken line in the figure. You may.

〔The invention's effect〕

As described above, according to the automatic frequency control operation method of the present invention, since the amount of excitation can be changed very quickly, a high-speed automatic frequency control operation is possible, and a drastic opening and closing of the guide vanes significantly Since the flow rate is not fluctuated, the stability of the water channel system is improved, and civil works such as a large capacity surge tank can be reduced.

Therefore, the construction cost of the hydroelectric power plant can be reduced, and the power transmission system can be stabilized.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an apparatus applied to the method of the present invention, FIG. 2 is a sequence diagram showing an embodiment of the method of the present invention, and FIG. 3 is a performance of a water turbine for explaining the operation of the present invention. FIG. 4 is a curve diagram, FIG. 4 is a sequence diagram showing another embodiment of the present invention,
FIG. 5 is a performance curve diagram for explaining the operation, and FIG. 6 is a chart showing changes over time in load, guide vane opening, iron pipe water pressure and rotation speed in the conventional automatic frequency control operation. 1 ... water pressure pipe, 2 ... water turbine, 3 ... AC excitation induction generator, 4 ... AC excitation device, 5 ... cycloconverter,
6 ... Power generation output / rotation speed guide vane opening detector, 7
...... Excitation amount detector, 8 ...... Automatic frequency control device.

Claims (2)

[Claims] Claim: What is claimed is: 1. A control of a variable speed generator comprising an AC excitation induction generator and a cycloconverter which is electrically coupled to the induction generator and converts an electric frequency generated by the generator into a system power supply frequency. In the method, a detector that detects the current power generation output, a detector that detects the current excitation amount, and a calculation device that calculates the required excitation amount are installed in parallel, and the AC excitation amount of the induction generator, A control method for a variable-speed power generator, characterized in that the load is increased / decreased to correspond to a predetermined cycle and fluctuation amount required for the system to perform load increase / decrease control, and automatic frequency control operation is performed. 2. The frequency conversion capability of the cycloconverter is set as a limit value, and the rotation speed of the induction generator is detected by a separately arranged rotation speed detector. Only when this rotation speed exceeds the limit value, The method for controlling a variable speed power generator according to claim 1, wherein the guide vane is opened or closed.