JPS62225774A - Speed governor for water turbine - Google Patents

Abstract

PURPOSE:To prevent a voltage drop, by forming a regulating signal based on a difference between a sensed voltage and a set voltage of electric power generated and regulating a control signal of a governor in response to the regulating signal. CONSTITUTION:When a rush current flows at a start of an induction motor, a voltage sensing circuit 10 senses a drop in an output voltage and a signal is delivered to a second calculation circuit 12b based on a difference between the sensed voltage and the set voltage delivered from a specified voltage setting circuit 11. A gate circuit 6 controls a thyristor 7 for reducing a current flowing in a regulating load 15. With this arrangement, a voltage drop can be prevented even in a large rush current is caused as the case an induction motor starts.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention mainly relates to a speed governor for a water turbine in a water turbine power generation device using an automatic induction generator.

[Conventional technology]

In the past, induction generators were used in combination with synchronous generators, but recently, automatic induction generators using capacitors have been developed, which are cheaper than synchronous generators. This makes it suitable for use in small hydroelectric power generation.

In an induction generator using a capacitor such as a bipod, the voltage can be increased by increasing the capacitance of the capacitor, but at the same time, the voltage decreases as the load increases (see Figure 3). Therefore, in order to keep the voltage constant regardless of the increase or decrease in the load, it is necessary to change the capacitor capacity -,lli, depending on the increase or decrease in the load, or to set up an adjustment load separately from the load. Measures are taken to keep the total load and rotational speed of the generator constant by increasing or decreasing the magnitude of the regulating load. Of these, changing the capacitor capacitance lit requires complicated and expensive equipment.
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In addition to controlling the capacity of the capacitor, it requires a device to keep the rotation speed (frequency) constant, and is not suitable for small-scale hydropower generation. is commonly used. The speed governor for water jlj using such means is as follows.

Conventionally, by detecting the frequency of generated power, comparing this detected value with a specified frequency, and increasing or decreasing the flow to the adjustment load based on the difference, the total amount consisting of the load and the adjustment load has been conventionally I tried to keep the load constant. In other words, when the practical load increases and the frequency decreases, a control signal is formed that reduces the current flowing through the adjustment load, and conversely, when the practical load decreases and the frequency increases, the control signal increases the current flowing through the adjustment load. However, the adjustment load was increased or decreased based on this control signal.

[Problem that the invention seeks to solve]

However, when an induction motor is used as a load of a self-excited induction generator, the following problems have arisen with control based only on frequency as described above. In other words, when starting an induction motor, an inrush current several times the rated current flows, but this inrush current? Since most of LLE is a reactive current, the excitation current of the induction generator is consumed by this reactive current at startup, causing 1! The power voltage drops and the excitation current to the load is insufficient. For this reason, there has been a problem that the induction motor cannot be started smoothly or cannot be started at all if the voltage has significantly decreased. In order to solve this problem, it is possible to consider a device that uses a thyristor or the like to vary the capacity of the self-exciting capacitor of an induction generator, but this device is extremely expensive and complicated and is not suitable for small-scale hydropower generation.

[Means for solving problems]

The present invention has been made in view of the above circumstances, and includes forming an adjustment signal based on the difference λ between the detected voltage of the generated power and the set voltage, and adjusting the control signal using this adjustment signal. The gist is that.

[Action of the invention]

The speed governor for a water turbine according to the present invention is designed to increase or decrease the magnitude of the regulating load so that the total load remains constant, using an regulating signal formed based on the difference between the detected voltage and the set voltage of one generated power. The control signal to be controlled is adjusted, and when the voltage of one generated power decreases, such as at the time of starting when an induction motor is used as a load, the control signal is made smaller, and the magnitude of the adjustment load is made smaller than in a steady state. By doing so, the magnitude of the adjustment load can be increased or decreased depending on the detected voltage, such as temporarily reducing the total load.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

Reference numeral 1 denotes an induction generator, which is driven by a water turbine 2.

A fixed capacitor 3 is provided as a self-excitation device for the induction generator 1.

Further, 4 is a practical load such as an induction motor using the induction generator 1 as a power source. An adjustment load 5 is connected to the induction power generation @1 in parallel with this practical load 4,
A thyristor element 7 is connected to the primary side of this 31 adjustment load 5 for controlling the phase of the load current of the adjustment load 5 by a gate signal sent from a gate circuit 6. The gate circuit 6 outputs a gate signal such that the larger the control signal input from the third arithmetic circuit (described later), the longer the conduction time of the thyristor 7 becomes. That is, the current flowing through the adjustment load can be arbitrarily adjusted by controlling the gate circuit B.

Reference numeral 8 denotes a frequency detection circuit, which detects the frequency of the generated power and outputs the magnitude of the frequency as 1, for example, as a detection signal with a reference frequency determined in this frequency detection circuit as "1". In other words, if the detection frequency becomes larger than the quasi-J, 'J wave number due to a reduction in the practical load, a detection signal larger than "1" proportional to the magnitude will be output, and in practical use If the detection frequency becomes smaller than the reference frequency due to an increase in load, a detection signal smaller than "1" proportional to the degree of smallness is output.

Reference numeral 9 denotes a specified frequency setting circuit, in which the set frequency is set to a frequency when the total load consisting of the practical load 4 and the adjustment load 5 matches the output of the induction generator I, and this set frequency is set to the frequency detected by the frequency detection circuit. It is output as a setting signal converted at the same ratio as the relationship between the detection frequency and the detection signal in the circuit 8. That is, if the set frequency is the same as the reference frequency in the detection circuit 8, regulation No. 43 having a magnitude of "1" is output.

Reference numeral 10 denotes a voltage detection circuit, which detects the voltage output from the induction power generation a1 and outputs this detected voltage as a detection signal that reduces a predetermined voltage to half its value. If it is smaller than the voltage, it outputs a detection signal that has the same proportional relationship with the reference value as the proportional relationship between the specified voltage and the detected voltage.

Reference numeral 11 denotes a specified voltage setting circuit, which uses the specified voltage of the induction generator I as a set voltage, and uses this set voltage as a setting signal converted at the same ratio as the relationship between the detected voltage and the detected signal in the voltage detection circuit 10. It is outputting. That is, if the predetermined voltage used as a reference value in the voltage detection circuit 10 is the same as the specified voltage, the setting signal becomes the same as the reference value of the detection signal in the voltage detection circuit 10.

12 is an arithmetic unit, and this arithmetic unit 12 has a specified voltage 1
A first arithmetic circuit 12a that subtracts the detection signal value of the voltage detection circuit 10 from the set signal value of the predetermined circuit 11 and outputs an adjustment signal obtained as the subtraction value; A second arithmetic circuit 12b that adds the signal value and the setting signal irfi outputted by the specified frequency setting circuit 9 and outputs a correction setting signal 1+ obtained as the added value, and a detection signal value outputted by the frequency detection circuit 8. Subtract the correction setting signal value output from the second arithmetic circuit from
It consists of a third arithmetic circuit 12c that outputs a control signal obtained as this subtraction value. The control signal output from the third arithmetic circuit 12c is input to the gate circuit 6, and controls the gate signal.

In the water turbine governor of the water turbine generator configured as described above, for example, when an induction motor is used as a practical load, it operates as follows. First, when the induction IIb machine starts up, an inrush current flows, causing induction generation.
When the output voltage decreases, the voltage detection circuit 10 detects this and outputs a detection signal smaller than half the value proportional to the degree of voltage decrease. The first arithmetic circuit 12a subtracts the detection signal value output from the detection circuit IO from the setting signal value based on the setting voltage output from the specified voltage setting circuit 11.

Therefore, the larger the voltage drop of one generated power, the more
The subtraction value output by the arithmetic circuit, ie, the adjustment signal, also becomes thicker.

Next, this adjustment signal is added to the set signal value based on the set Oka wave number output from the specified frequency setting circuit 9 in the second arithmetic circuit 12b. That is, when a voltage drop occurs, the setting signal output from the frequency setting circuit 8 is corrected by the second arithmetic circuit 12b, and the third correction setting signal is outputted as a corrected setting signal that has a higher level than when the voltage has not dropped. Input to the arithmetic circuit.

Therefore, the control signal obtained as a subtraction value in the third arithmetic circuit 12c is smaller than when the voltage is not reduced, and the gate circuit 6 that receives this control signal controls the thyristor 7 so that the conduction time is shortened. Therefore, the current flowing through the adjustment load 5 is lowered. That is, if the frequency detected by the frequency detection circuit 8 does not change and the voltage of one generated power decreases, the adjustment load decreases. By reducing the adjustment load in this way, the total load also decreases, and as is clear from the graph of FIG. 3, the voltage increases. Therefore, even if a large inrush current occurs, such as when starting the induction motor, voltage drop can be prevented, and there will be no problem with the starting, etc. When the induction motor enters steady operation, the reactive current will be reduced. Since the voltage decreases significantly, the voltage drop becomes small and the current flowing through the regulating load returns to its steady state.

It should be noted that the present invention is of course not limited to the above-mentioned embodiments; for example, the signal levels of each detection signal and setting signal can be set arbitrarily. Further, in the above embodiment, the calculation unit 12 corrects the setting signal output by the frequency setting circuit 9 using the adjustment signal obtained based on the output values of the heavy pressure detection circuit 10 and the specified voltage setting circuit 11. The control signal was formed by this correction setting signal and the detection signal output by the frequency detection circuit 8, but for example, as shown in the calculation section 12° shown in FIG. The output value is subtracted in the second arithmetic circuit 12b', this subtracted value is used as a preliminary control signal, and the third arithmetic circuit 12C° performs a subtraction process similar to the embodiment formed in the preliminary control signal and the first arithmetic circuit 12a'. By adding it with the adjustment signal, a control signal to be output to the gate circuit 6 may be formed.Furthermore, in order to control the current flowing through the adjustment load, in addition to the thyristor element in the embodiment, a switch, a power transistor, etc. Various other switching elements can be used.

〔Effect of the invention〕

As is clear from the above explanation, if the water turbine governor according to the present invention is used, even when an induction motor is used as a load of a power generation device using an automatic induction generator, the inrush current at the time of startup can be reduced. This eliminates the possibility that the voltage will drop due to this, making it difficult to start such an induction motor or not being able to start it at all. By being able to cope with the voltage drop caused by the rush current caused by the load in this way, the present invention is particularly effective in significantly expanding the applications of the self-excited induction generator.

[Brief explanation of drawings]

FIG. 1 is a block diagram explaining the present invention in detail, FIG. 2 is a block diagram of main parts explaining another embodiment, and FIG. ,
It is a graph showing the relationship between the load and voltage of an electric machine. 5... Adjustment load 6... Gate circuit? ...Thyristor element 8...Frequency detection circuit 9...Specified frequency setting circuit 10...Voltage detection circuit 11...Specified voltage setting circuit 12, +2°...Calculating section

Claims (1)

[Claims] (1) A control signal is formed based on the difference between the detected frequency of the generated power and the set frequency, and this control signal increases or decreases the size of the adjustment load, which is set up separately from the practical load, so that the total load remains constant. In a speed governor for a water turbine, an adjustment signal is formed based on the difference between the detected voltage and the set voltage of the generated power,
A speed governor for a water turbine, characterized in that the control signal is adjusted using this adjustment signal.