JPH01160362A - Noncirculation type cycloconverter controller - Google Patents

Abstract

PURPOSE:To switch the operation group of a cycloconverter and to reduce an output pulsation, a high frequency by providing arithmetic means for predicted exciting current value and comparing means for comparing it with zero. CONSTITUTION:When a current command ip is zero, a gate shift start signal 111 is output from a comparator for detecting it to a signal converter 105, it is input to an automatic pulse phase shifter 10, and a gate block signal 113 is output to the operating group of the cycloconverter. In order to output the start signal 111, a predicted exciting current value arithmetic circuit 101, a phase delay angle arithmetic circuit 102, and a comparator 106 are newly provided. The phase delay angle is calculated by the arithmetic circuit 102, but a circuit for compensating it is added as a circuit similar to the arithmetic circuit 102, the output is added to be extended. Thus, when the predicted exciting current value is zero, the signal 111 is output to the converter 105.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a non-circulating cycloconverter control device used for secondary excitation of a generator motor in a variable speed pumped storage power generation system.

[Conventional technology]

When the load on the power system is light and there is surplus power at other power plants, this can be used to store water by pumping it to a reservoir at a high altitude, and storing water during times of river drought or when the power demand of the load is large. Pumped storage power generation is known as a system that uses stored water to generate electricity when needed, such as when pumping water Also, the load cannot be adjusted. During power generation operation and pumping operation, there is a drawback that the efficiency of the power generation system changes due to fluctuations in the generated power required by the grid, changes in pumping height, etc. Therefore, in order to operate the above system at maximum efficiency regardless of the generated power or head, a secondary excitation type generator motor was used instead of the conventional synchronous machine. Research into the practical application of so-called variable speed pumped storage power generation systems is underway. In this variable speed pumped storage power generation system, a cycloconverter is used as a source of three-phase low frequency alternating current for secondary excitation of the generator motor, and in particular when a non-circulating cycloconverter is adopted in consideration of economy and compactness. There are many. Literature regarding these variable speed pumped storage power generation systems is as follows:
Paper NQ553 of the 1981 National Conference of the Institute of Electrical Engineers of Japan, ``Variable Speed Operating Characteristics of Large Capacity Synchronous Motors.'' This document does not disclose a specific excitation control method. [Problems to be solved by the invention] As is well known, in a non-circulating cycloconverter, it is necessary to switch the operating groups at an appropriate time, and if the positive group and negative group are operated at the same time, To prevent this from forming a short circuit when switching between the positive and negative groups, there is usually a period in which no current is flowing in either group, and after checking that the current is zero, the current after polarity reversal is determined. The operation command is issued to the group with the same polarity as the . However, during the period when current is not flowing in both groups, the corresponding phase of the rotor winding of the generator motor is in an open circuit state. An induced voltage is generated in this phase due to mutual induction with other windings (three stator windings and two rotor windings). This induced voltage becomes output pulsation of the generator motor and flows out or flows into the power system. Furthermore, when the period during which current is not flowing in both groups becomes longer, the output waveform distortion of the cycloconverter increases, causing harmonic generation. Next, using Fig. 3, we will explain the conventional method of switching operating groups of a non-circulating cycloconverter and its problems.Normally, in a variable speed pumped storage power generation system, the standard for controlling the output current of a cycloconverter is naru current command ip
is given as a sine wave with a target slip frequency, where the vertical axis is the current value and the horizontal axis is time t. At this time, the actual cycloconverter output current (excitation current) i
Although it depends on the load, zx has a certain phase lag with respect to the current command ip. To switch the operating group, for example from the positive group to the negative group, detect that the current command ip has become zero, set the firing phase of the positive group thyristor to the gate shift phase, rapidly narrow down the output current, and then , detects that the output current has become zero and outputs the positive group thyristor gate signal P.
Let G be in a gate block state. Then, after the thyristor turn-off time, the negative group thyristor gate signal NG is turned on. However, when operating group switching is performed in this way, the phase delay of the output current i□2 is large during operation with a high slip frequency, so the current command i p
Even if becomes zero, the current itZ is still not close to zero,
From there, the current is rapidly narrowed down. As a result, not only the output waveform is distorted, but also the positive group thyristor gate signal P
The time when G is gate-blocked is delayed, and furthermore, even when the negative group thyristor gate signal NG is gated on, the rise of the current ilx is delayed, so the time during which no current is flowing in both groups is equivalently extended, and as a result, power generation is delayed. There was a problem in that the motor's output pulsation and waveform distortion became large. The purpose of the present invention is to safely and reliably switch the operating groups of a non-circulating cycloconverter that secondarily excites a generator motor without the risk of short-circuiting one group and in the minimum amount of time, thereby reducing output pulsation and harmonic generation. It's about doing. [Means for solving the problem] The above purpose is to provide a current instruction, which serves as a reference for output current control of the cycloconverter, to a control device of a non-circulating cycloconverter that secondary excites the generator motor of a variable speed pumped storage power generation device. A calculation means for calculating a predicted excitation current value ipz obtained by delaying the current ip by a predetermined phase delay angle α, and a comparison means for detecting that the predicted excitation current value ipz obtained by the calculation means has become zero, This is achieved by using the output of the comparison means as a signal for instructing narrowing down of the cycloconverter output current to switch the operation group of the non-circulating cycloconverter. [Operation] In the present invention, current control is executed based on the current command ip as in the prior art except when switching the operation group of the cycloconverter, but only when switching the operation group the excitation current predicted value ip is used.
2 becomes zero, and the cycloconverter output current is narrowed down. The i-th predicted excitation current value has a waveform substantially the same as the actual cycloconverter output current by delaying the current command ip by a predetermined phase delay angle α. Therefore, when ipz becomes zero, the actual cycloconverter output current is also approaching zero, so by narrowing down the output current from this point on, it is possible to quickly switch the operation group, which reduces the output waveform distortion of the cycloconverter. as a minimum. It is possible to reduce output pulsation and harmonic generation of the generator motor. Furthermore, by changing the phase delay angle α in relation to factors that affect α, such as the overflow frequency of the generator motor, it becomes possible to perform good operation group switching control over a wide operating range. [Example] An example of the present invention will be described below with reference to the drawings. FIG. 2 shows the configuration of a variable speed pumped storage power generation system to which the present invention is applied. One end of the main transformer 2 is connected to the power grid 1,
The excitation current for alternating current excitation of the rotor (secondary) side of the generator motor 3, which is connected to the stator (-) side of the generator W1 motor 3 via the parallel closing circuit breaker 5, is , is obtained from between the main transformer 2 and the parallel closing circuit breaker 5 via the excitation circuit breaker 6, and the output of the power system 1 during pumping operation and the generator motor 3 during power generation serves as the excitation power source. The input from the excitation power source has the same frequency as the power system frequency, but it is converted into an AC excitation current with a three-phase slip frequency by the non-circulating cycloconverter 7 via the excitation transformer 9, and the generator motor Excite the rotor side of No.3. In order to create an excitation current with the above-mentioned slip frequency, it is necessary to detect the slip frequency phase during current operation. Therefore, in this embodiment, the stator side of the phase detector 4 is excited from the system side of the parallel closing circuit breaker 5 via the voltage transformer 14. This phase detector 4 is a type of induction generator, and its rotor is coaxial with the rotor of the generator motor 3, so if the stator side is excited at the system frequency, the output from the rotor side is perfectly frequency This means that the waveform is detected. The slip frequency phase information detected in this way is taken into the cycloconverter control device 8 together with the output current feedback value of the cycloconverter 7 detected by the current transformer 13. The cycloconverter control device 8 performs various calculations based on the frequency phase information from the phase detector 4 and the output current feedback value from the current transformer 13, and as a result of those calculations, the thyristor for controlling the output current. Control signals 11 such as an ignition phase signal, a gate shift signal output command for switching operation groups, a gate block signal, and a gate deblock signal are output to the automatic pulse phase shifter 10. The automatic pulse phase shifter 10 generates a thyristor firing pulse signal 12 to the cycloconverter 7 in response to the control signal.
output and operation group switching. FIG. 1 shows the configuration of a cycloconverter control device 8 according to the present invention that solves the problems of the prior art. This device includes a current command calculation circuit 100 and a current control circuit 1 for controlling the output current of the cyclocomputer.
03 is provided. The current command calculation circuit 100 calculates a current command ip, which serves as a reference for output current control, using the following equation. ip= Idsins (1) t + Iqcoss
(1) t Here, It indicates the d-axis current command, and 9 indicates the q-axis current command. sin sωt and cossωt each indicate the phase of the Veri frequency, and are given as the output of the phase detector 4 shown in FIG. The current control circuit 103 is
The deviation between the current command ip calculated by the current command calculation circuit 100 and the actual excitation current il detected by the current transformer 13 in FIG. 2 (this is equivalent to the cycloconverter output current) is calculated to determine the actual excitation current. 1ttI - Thyristor firing phase signal 11 for controlling to match current command ip
This circuit outputs 0 to the signal switch 105, and when controlling the output current, this thyristor firing phase signal 110
is input to the automatic pulse phase shifter 10 as the output signal 112 of the signal switch 105. In the conventional technology, when the current command ip becomes zero. A gate shift start signal 111 is sent from a comparator that detects this.
is outputted to the signal switch 105, inputted to the automatic pulse phase shifter 10 as a gate shift signal output command, and then sent to the currently working group of cycloconverters from the comparator 104 shown in FIG. On the other hand, gate block signal 113
was outputting. The comparator 104 is a circuit that detects when the actual excitation current i becomes zero. Furthermore, after the thyristor turn-off time counter 107, which is started by this gate block signal 113, finishes counting, the counter 107 outputs a gate deblock signal 114 to the operation group on the opposite side, thereby switching the operation of the cycloconverter. Ta. In the embodiment of the present invention shown in FIG. 1, in order to output the gate shift start signal 111, the excitation current predicted value calculation circuit 1012, the phase delay angle calculation circuit 102. Comparator 10
6 is provided. The excitation current predicted value calculation circuit 101 is a circuit that delays the current command ip by a predetermined phase delay angle α to generate a signal having substantially the same waveform as the actual excitation current ix, and performs the calculation of the following equation. i P2= I asin(sωt-α) + I q
cos (sω is one α) The excitation current predicted value ip2 calculated in this way is input to the comparator 106. Comparator 10
6 is a circuit that detects that the excitation current predicted value ip2 has become zero. The phase delay angle α is determined by the phase delay angle calculation circuit 1.
02, but here we focus on the fact that the value of α is largely influenced by the slip frequency sf, and use it as a function of the slip frequency sf. In reality, the factor that has the greatest influence on the phase delay angle α is the slip frequency sf, but if there are other factors, a circuit to compensate for this may be added as a circuit similar to the phase delay angle calculation circuit 102 described above. , the excitation current predicted value calculated by the excitation current predicted value calculation circuit 101, which can be easily expanded by adding its output to the phase delay angle α shown in FIG. 1, and whose basic configuration is the same as that shown in FIG. Comparator 1 that detects when ipz becomes zero
06, the gate shift start signal 111 is sent to the signal switch 10.
5 and is input to the automatic pulse phase shifter 10 as a gate shift signal output command. Next, the state of operation group switching control by the five apparatuses will be explained using FIG. 4. FIG. 4 shows that the present device improves the cycloconverter operation group switching control according to the prior art shown in FIG. 3. First, FIG. 4(a) shows the case where the motor is operated in a small slip region. in this case. α1 is output as the phase delay angle α to the phase delay angle calculation circuit 102 shown in FIG.
The waveform is almost the same as 1. Therefore, when the actual excitation current 10 becomes almost zero from the comparator 106 shown in FIG.
, 11 are output, the actual excitation current izt reaches zero without much distortion from the sine waveform. At this time,
Immediately, the gate block signal 113 is output from the comparator 104 shown in FIG. 1 to the currently operating positive group thyristor, and both groups of thyristors are turned off. After that, the gate deblock signal 114 is sent to the negative group thyristor on the opposite side from the thyristor turn-off time counter 107.
This makes it possible to perform safe, reliable, and rapid cycloconverter operation group switching control. The above operation is the same when operating in a region with large slippage, as shown in FIG. 4(b), and as shown in FIG. 4(a).
Safe, reliable, and rapid operation group switching control of a cycloconverter similar to the above is realized. The difference from Fig. 4(a) is that
The only difference is that the phase delay angle α calculated by the phase delay angle calculation circuit 102 is α2. According to this embodiment, since the phase/phase delay angle α is given as a function of the slip frequency, it is possible to realize good operation group switching control over a wide operating range. [Effects of the Invention] According to the present invention, it is possible to realize safe, reliable and rapid switching of operation groups of a non-ring type cycloconverter that secondarily excites one generator motor, thereby suppressing cycloconverter output waveform distortion and improving operation. By shortening the gate block time during group switching, the output pulsation and harmonic generation that are inevitable in variable speed pumped storage power generation systems using non-circulating cycloconverters can be significantly reduced compared to conventional technology.

[Brief explanation of the drawing]

Figure 1 is a circuit configuration diagram of an embodiment of the present invention, Figure 2 is a configuration diagram of a variable speed pumped storage power generation system to which the present invention is applied, and Figure 3 is operational group switching control of a non-circulating cycloconverter according to the prior art. FIG. 4 is an explanatory diagram of operation group switching control of a non-circulating cycloconverter using the circuit of FIG. 1, in which (a) shows a case where the slip is small, and (b) shows a case where the slip is large. DESCRIPTION OF SYMBOLS 1... Power system, 3... Generator motor, 4... Phase detector, 7... Non-circulating cycloconverter, 8...
・Cycloconverter control device, 10... automatic pulse phase shifter, 100... current command calculation circuit, 101...
Excitation a current predicted value calculation circuit, 102... Phase delay angle calculation circuit, 103... Current control circuit, 104, 106...
- Comparator, 105... Signal switch, 107... Thyristor turn-off time counter. 13-4'澗su'ha4te

Claims (1)

[Scope of Claims] 1. A control device for a non-circulating cycloconverter that supplies excitation current at a slip frequency to a secondary excitation circuit of a generator motor of a variable speed pumped storage power generation device, which controls the output current of the non-circulating cycloconverter. A calculation means for calculating a predicted excitation current value obtained by delaying a current command as a reference by a predetermined phase delay angle, and a comparison means for detecting that the predicted excitation current value calculated by the calculation means has become zero. A non-circulating cyclo-converter control device, characterized in that the output of the comparing means is used as a signal for instructing narrowing down of the cyclo-converter output current to switch operation groups of the non-circulating cyclo-converter. 2. The non-circulating cycloconverter control device according to claim 1, wherein the phase delay angle is a variable determined in relation to at least the slip frequency.