JPH0265698A - Ac excited synchronous machine controller - Google Patents

Abstract

PURPOSE:To stably control an operation by providing series and parallel electronic switches with a current limiting resistor, closing the series and parallel switches substantially simultaneously at the time of generation of an abnormal voltage, and previously opening the parallel switch. CONSTITUTION:The phases of an AC system 1 are connected to a thyristor power converter 27 through a transformer 8. The converter 27 supplies a current to the secondary side phase of an AC-excited synchronous machine 2 in response to the command value from a current command calculator 6. The converter 27 has a second electronic switch 22 made of a cycloconverter in parallel with a current limiting resistor 20, and a first electronic switch 19 made of a cycloconverter in series with the resistor 20. When a power source malfunction is detected or at the time of emergency stop, the switches 19, 22 are closed substantially simultaneously, but when they are opened, the switch 22 is previously opened. Thus, the current of the converter 27 is effectively shut OFF, it becomes a short-circuited state in which a current limiting resistor is inserted after a predetermined period of time to thereby prevent a disturbance to be applied to an AC system 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control device for an AC-excited synchronous machine having a winding structure similar to a wire-wound induction machine, the primary side of which is connected to an AC power system. In particular, the present invention relates to a control device for an AC-excited synchronous generator motor suitable for a variable speed pumped storage power generation system.

[Prior Art] In a pumped storage power generation system, it is desirable to use a variable-speed generator-motor in order to flexibly respond to fluctuations in pumping head and load and achieve efficient operation.

Therefore, systems have been known that perform variable speed operation using an AC-excited synchronous machine with a winding structure similar to a single-winding induction machine. As a control method, for example, as disclosed in Japanese Patent Publication No. 53-7628 and Japanese Patent Publication No. 57-60645, by controlling the secondary excitation current of a synchronous machine, the active power and reactive power can be reduced. A system for controlling the electric power and electric power respectively is known, and has been effective as a force 1 adjustment device and a power adjustment device that can respond quickly while preventing disturbances and tax adjustments.

Incidentally, in recent years, systems using cycloconverters have been widely adopted as power conversion devices for obtaining AC excitation power for exciting the secondary side of AC excitation synchronous machines. However, in such cases, it is preferable to use a non-circulating current type cycloconverter in order to keep the required element capacitance of the thyristor to a minimum.

FIG. 9 shows a conventional configuration example of an AC excitation generator-motor device using such a cycloconverter.

In FIG. 9, 1 is an AC system, 2 is an AC excitation synchronous machine connected to the AC system 1, and 30 is a breaker provided between the AC system 1 and the AC excitation synchronous machine 2.

A phase detector 3 serves to detect a slip phase equal to the difference between the voltage phase of the AC system M1 and the rotation angle expressed in electrical angle of the AC excitation synchronizer 2. 4 is a g-axis component current command generator that generates a command value for a component (hereinafter abbreviated as g-axis component) of the secondary current of the AC excitation synchronizer 2 that is equal to the voltage phase of the AC system 1 when viewed from the primary side. The generator 4 functions to generate a command value in accordance with, for example, the active power of the AC excitation synchronizer 2, the rotational speed, or the deviation between the frequency setting value of the AC system 1 and the detected value. 5 generates a command value for a component of the secondary current of the AC excitation synchronizer 2 whose phase differs by /2 in electrical angle from the voltage phase of the AC system 1 when viewed from the primary side (hereinafter abbreviated as the d-axis component). This generator 5 functions to generate a command value in accordance with, for example, the reactive power of the AC excitation synchronizer 2 or the deviation between the voltage setting value of the AC system 1 and the detected value. 6 is a current command calculator which calculates the secondary side each phase current command Ia of the AC excitation synchronous machine 2 from the output signal Id of the 1st phase detector.
, Ib", Ic".

Reference numeral 7 in FIG. 9 denotes a thyristor power converter, which functions to supply current to each phase of the secondary side of the AC excitation synchronous machine 2 according to the command value of the current command calculator 6. Reference numeral 8 denotes a power receiving transformer that connects the AC system 1 and the thyristor power conversion device 7.

FIG. 10 shows a detailed circuit configuration of the thyristor power conversion device 7.

Reference numeral 11 designates a secondary current detector of the AC excitation synchronous machine 2, and reference numeral 12 represents a current control device that compares the current command value controller 8 with the detected value IN and commands the phase shifter 13 to set the thyristor firing phase. 141 and 142 are gate pulse amplifiers that energize the thyristor gates of the positive connection side thyristor converter 151 and the reverse connection side thyristor converter 152, respectively, 16 is a secondary current polarity switching command generator, and 17 is a forward/reverse switching logic circuit. Then, the forward/reverse switching command PN (the signal level is set to 1 when the energization command is given to the normal connection side) and the output signal ZD of the current zero detector 18 (the output level is set to 0 when the current is assumed to be O, and the current is set to 1). The output level when the current is considered to be 1) is used as input to generate output signals GP and GN. Reference numeral 19 denotes an electric valve (electronic switch) consisting of an anti-parallel thyristor for short-circuiting the secondary circuit of the AC excited synchronous machine 2, and 20 is connected in series to the electric valve 19. This is a current limiting resistor for suppressing short circuit current when an electric valve short circuits. 21 applies an ignition signal GBI to the electric valve 19 when the primary current and secondary current of the AC excitation synchronous machine 2 reach values within a preset range, or in the case of an emergency stop. , is an arithmetic circuit that outputs the input signal GB to the AND circuits 211 and 212 (the output signal is 1 when the above conditions are satisfied, and 0 in the normal state where the above conditions are not satisfied). 211 and 212 are AND circuits whose input signals are the outputs GP and GN of the forward/reverse switching logic circuit 17 and the output GB of the arithmetic circuit 21, respectively; It functions to generate start/stop signals GP'' and GN''' (signal level at start is 1 and signal level at stop is 0).

FIG. 11 shows the operating waveforms of each part when the AC excitation synchronous machine 2 is operating in the conventional example described above.

Figure 11 shows the waveform when the voltage of AC system 1 is normal and in a steady state. When the polarity of current command value ■1 changes from negative to positive at point ■, a forward/reverse switching command is generated. The output signal PN of the device 16 changes from level 0 to level 1, and the forward/reverse switching logic circuit 17 starts a forward/reverse switching operation. Then, at the point in time (2) when the secondary current IM becomes O, the level of the GN signal that was giving the activation command to the reverse side gate pulse amplifier 142 changes from 1 to O, and the thyristor gate pulse on the reverse connection side disappears. After that, after a time corresponding to the turn-off time of the thyristor has passed, at point (3), the signal level of the activation command GP to the positive side pulse amplifier 141 changes from O to 1, and the gate of the positive connection side thyristor converter is energized. Secondary current begins to flow in the positive direction.

Here, when the secondary current enters the rest period, AC excitation synchronization v&2. Since the relevant windings of the primary and secondary windings are released,
An induced voltage is generated due to mutual induction with the next-side other phase windings.

However, since the magnetic unbalance of the AC-excited synchronous machine 2 in this rest section is small, the value of the induced voltage is small and does not pose a problem.However, in such a system, on the AC system side The effects of short-circuit accidents, etc. are unavoidable.

Therefore, when such an accident occurs, the AC excited synchronous machine 2
When a DC current flows through the primary side of the AC-excited synchronous machine 2, a transient current having a rotational frequency (1-S)Xf as a component tends to flow through the secondary side of the AC-excited synchronous machine 2 due to induction. Here, f is the system frequency and S is the slip. Further, this secondary side transient current component appears superimposed on the slip frequency component Sf.

Therefore, when the current polarity of this slip frequency component SF changes, it is superimposed.

The rotational frequency component (1-8) Xf causes a period in which the current always flows in the direction opposite to the polarity of the command value from the current command generators 4 and 5. In addition, in the event of an asymmetrical accident, a secondary current with a frequency component (2-S) occurs.

On the other hand, at this time, if a non-circulating current type cycloconverter is used as the power converter for supplying the secondary side AC excitation current, this cycloconverter may be in the opposite direction to the polarity switching signal. As a result, during the above period, the electrical path of this cycloconverter is open, and the above reverse current cannot flow. During this period, a voltage is induced in the corresponding secondary winding of the AC-excited synchronous machine 2 due to mutual induction.

However, due to the characteristics of such AC-excited synchronous machines, this induced voltage typically far exceeds the cycloconverter's output rated voltage determined from the set operating speed range. As a result, if left as is, there is a risk that the thyristor elements constituting the cycloconverter may be destroyed.

Therefore, in order to deal with such problems, the above-mentioned conventional technology connects an electric valve consisting of a nonlinear resistance element and an antiparallel thyristor, and a mechanical circuit short circuit in parallel with the thyristor element to provide transient voltage protection. This point will be explained below.

FIG. 12 shows voltage waveforms at various parts when a short-circuit accident occurs on the AC system side. First, time points to (2) are as explained in FIG. 11.

Next, an accident occurred at point ■, and the AC excited synchronous machine 2
Suppose that a voltage that causes a transient current is induced on the secondary side of the circuit, and a transient current begins to flow.

When this current reaches a predetermined value V, the gate pulse signal GBI of the electric valve 19 is applied to fire the anti-parallel thyristor. Also, at this time, the output GB of the arithmetic circuit 21 is set to 1, thereby gate-blocking the main thyristor elements 151 and 152 of the thyristor power converter. As a result, the output side of the thyristor power conversion device is short-circuited by the current-limiting resistor 20 via the electric valve 19, and a current 1 eve of a predetermined value determined by the resistance value of this resistor 20 flows. , this electrician. As , crosses zero, this current T cyc becomes zero, and as a result, the thyristor elements 151 and 152 are turned off, and overvoltage is suppressed.

Therefore, according to this conventional example, even in the event of an accident, by controlling the closing of the electric valve 19 consisting of an anti-parallel thyristor, the secondary side circuit of the AC excited synchronous machine 2 is short-circuited to suppress overvoltage, and the In addition to being able to exhibit the protection function, the thyristor power conversion device can be stopped at this point.

Further, according to this prior art, even in the event of an emergency stop, the electric valve 19 is controlled in the same manner as shown in FIG. The elements 151 and 152 can be protected from overvoltage.

[Problem to be solved by the invention] In the above-mentioned conventional technology, an electric valve (
The main focus has been on protecting the secondary circuit from overvoltage by short-circuiting the secondary side of the AC-excited synchronous machine using an electronic switch (electronic switch). The problem was that it was difficult to maintain a balance between overvoltage protection in the event of an accident and disturbances to the system and equipment. That is, in such a system, from the viewpoint of transient voltage suppression, it is desirable that the resistance value of the current limiting resistor is low, but on the other hand, this causes a large change in the active power output when the secondary side is short-circuited.

Therefore, the application of such systems, especially to AC-excited synchronous machines such as large-capacity pumped storage power generation systems, is unlikely to continue as it is, as it may have a significant impact on the stability of the AC system. Not applicable.

In addition, in such a large-capacity system, the time constant of the secondary circuit is large, which increases the duration of the fault current in the event of an AC system fault, and as a result, a major fault occurs in the AC excited synchronous machine. The addition of current and large torque produces severe disturbances.

Therefore, in such a system, it is difficult to reduce the resistance value of the current limiting resistor, and it is necessary to set the resistance value to a considerably large value.

However, on the other hand, since the current in the thyristor elements 151, 152 when the electric valve 19 is short-circuited is controlled by the resistance value of this current limiting resistor, increasing this resistance value is not enough. As shown in FIG. 2, the value of the transient current component becomes small, and the output current of the thyristor power converter is not cut off for a long period of time, creating the risk that the thyristor current converter may be damaged.

Another problem is that during an emergency stop, the current in the thyristor current converter is slow to turn off, making it impossible to shift to a predetermined stop operation.

Therefore, in this prior art, as described above.

There was a problem in that no consideration was given to both protection and operability of AC-excited synchronous machines, making it difficult to apply them to AC-excited synchronous machines, especially in large-capacity pumped storage power generation systems.

The purpose of the present invention is to sufficiently suppress overvoltage and prevent disturbance to AC systems and equipment in such cases.
Even during high-speed restart/closing control in the event of an AC system accident or during an emergency stop, even a large-capacity AC-excited synchronous machine using a thyristor power conversion device can be maintained stably without causing any major disturbance to the AC system. An object of the present invention is to provide an AC excitation synchronous machine control device that can control operation and provide sufficient protection.

[Means for Solving the Problems] The above objective is to provide a protection function using a current limiting resistor connected in series and parallel to an electric valve on the secondary side of an AC excited synchronous machine. For this current limiting resistance,
This is achieved by directly connecting another electric valve in parallel, and controlling the closing of the additional electric valve at a predetermined timing when the original electric valve is closed.

[Operation] When the original electric valve is closed, the newly added electric valve can be controlled to close almost at the same time.

At this time, the current limiting resistor is short-circuited, and as a result, the output of the thyristor power converter is directly short-circuited by the separately added electric valve, and a large transient current is superimposed on the output current, which quickly attenuates and ensures reliable As a result, the circuit can be completely cut off regardless of the resistance value of the current limiting resistor.

After this, if you control the newly added electric valve to open, it means that a current limiting resistor has been inserted into the short circuit. If you make it a sufficiently large value compared to the resistance value of the machine's secondary circuit.

The time constant of the secondary circuit with respect to transient current becomes large, and the attenuation of the transient component of the short-circuit current at the time of an accident can be sufficiently accelerated with almost no disturbance occurring.

[Example] Hereinafter, 1 about the AC excitation synchronous machine control device according to the present invention.
This will be explained in detail with reference to the illustrated embodiment.

FIG. 2 shows an embodiment of the present invention, in which the same parts as in the conventional example explained in FIG. 9 are denoted by the same reference numerals. AC excited synchronous machine 2. Breaker 301
Since the phase detector 3, current command calculator 6, and power receiving transformer 8 have been explained in the conventional example section, a description of their functions will be omitted. 25 is a q-axis component current command generator, which generates a q-axis component current command Iq'' from the deviation between the output detection value detected by the active power detector 24 and the set value. 26 is a d-axis component current command generator, A d-axis component current command Id' is generated from the deviation between the detected value and the set value of the voltage effective value of the AC system 1. 27 is a thyristor power converter, the detailed circuit configuration of which is shown in Fig. 1. The same reference numerals as in FIG. 10, which shows the configuration of an example, indicate the same parts. In this figure, 22 is a second electric valve connected in parallel with the current limiting resistor 20, which is composed of a thyristor connected in anti-parallel. This second electric valve 22 is controlled to close when the gate pulse signal GB2 is applied,
It functions to short-circuit the current limiting resistor 20. Note that the electric valve 19 that is common to the prior art described above is hereinafter referred to as a first electric valve.

FIG. 3 shows the gate pulse signal GBI for controlling the first electric valve 19, the gate pulse signal GB2 for controlling the second electric valve 22, and the main thyristor element 151 of the thyristor power converter 2. .152 is an example of the calculation unit 23 that calculates the gate block signal GB, and 231 is the current detection value of the current detector 11 installed in each phase of the secondary side circuit of the AC excitation synchronous machine 2, This is a comparator that compares the current level with a predetermined current level, and functions to generate an output that becomes level O1 when the current is lower than the set value and level 1 when it is higher.

The outputs of these three comparators 231 are connected to the OR circuit 2.
32, and further combined with the emergency stop signal ES in the next OR circuit 233.

Next, a signal 234 inputs the output signal 23b of the OR circuit 233, is triggered when this signal 23b changes from level 0 to 1, and maintains the level 1 for a predetermined time T aWl from this time. 235 is a holding circuit that outputs this signal 23c and an OR circuit 233.
This is a holding circuit that outputs a signal 23d that becomes level 1 for a predetermined period T11° when both output signals 23b of 1 and 2 change to level 1. These holding circuits 234, 23
5, the output signal 23C of the holding circuit 234 is further combined with the emergency stop signal ES in an OR circuit 236, and input to two pulse amplifiers 237, respectively, to output each signal GBI.
, GB2, and get CB.

Next, the operation of this embodiment will be explained with reference to FIG.

FIG. 4 shows the state of each part in the calculation unit 23 during high-speed reclosing operation when an accident occurs. Now, suppose that the signal 23a changes from level O to level 1 at time t. , signal 23b changes similarly, and as a result, signals 23c and 23d also change from level 0 to level 1, respectively.

As a result, the firing signal GBI to the thyristor,
GB2 is supplied to the electric valve 19.22, and the secondary circuit of the AC-excited synchronous machine 2 is short-circuited.

Next, at time t2, when the level of the signal 23a returns to 0, the signal 23c returns to level O at time t4, which is delayed by a predetermined period t#w1.

If the emergency stop signal ES is maintained at level 0 at this time, then the thyristor firing signal GBI
also returns to level 0, and the electric valve 19 is opened.

On the other hand, before time t4, a predetermined period tgl from time ti
At time t when +1□ has elapsed, the signal 23d changes to level O, and here the firing signal GB2 to the thyristor reaches level O.
Returning to , the electric valve 22 is opened.

Next, time tsl t! So, time t work.

However, this time, the signal 23a rises to level 1 at a time point t earlier than the time point t, which is delayed by a predetermined period of time from the time point t6, and therefore the signal 23c remains at level 1, and as a result, the signal 23d returns to level 1 again at a point in time.

Figure 5 shows the operation when an accident occurs in AC system 1. If an accident occurs at point ■, the operation up to point ■ will be the same as in the conventional example shown in Figure 12. It's the same.

As mentioned above, if an accident occurs at one time point (3), a transient current having a rotational frequency component occurs on the secondary side.

Then, due to the rotational frequency component superimposed on the secondary side, the current on the secondary side exceeds the set value at time point 2, and as a result, the calculation unit 23 generates ignition signals GBI and QB2 for the electric valve 19°22. , and a thyristor power conversion device 15
1,152 gate block signals GB are output. For this reason, the activation of the thyristor power conversion device 151, 152,
The stop signals OP' and ON'' become level 0, and as a result, the output current 11V of the thyristor power converter becomes zero at time point ■, and then for a predetermined period T, , 2 from time point ■.
The ignition signal GB2 of the electric valve 22 is extinguished at time ■ after the elapse of time, and on the other hand, the ignition signal GBI of the electric valve 19 is activated at the time ■ when the output current of the thyristor power converter becomes equal to or less than the set value v.
It is erased at the time (3) when a predetermined period T aWl has elapsed since '.

Therefore, according to this embodiment, when an accident occurs, the secondary circuit of the AC-excited synchronous machine 2 is short-circuited in the order of: direct short-circuit without current-limiting resistor; 2 of the AC excited synchronous machine will be controlled.
Without being affected by the time constant on the next side, stop control can always be performed reliably in a short time without the risk of disturbance in the event of an abnormality such as an accident occurring.

In this embodiment, in order to reliably obtain the above-mentioned operation, the timing of the control operation of the two sets of electric valves 19 and 22 is important.
Appropriate settings for I T T mwz are important.

especially, T,, > T,,.

conditions are essential.

Further, this period T aWl needs to be set to a time sufficient to cut off the output current of the thyristor power converter after the secondary side circuit of the AC excited synchronous machine is short-circuited.

By the way, in this embodiment, in order to continue the closed state of the electric valve 19 during an emergency stop, as is clear from FIG.
The emergency stop signal ES is inputted via the circuit 236, and as a result, according to this embodiment, it is possible to respond to both grid-side accidents and emergency stops without any disturbance. Stop control can always be performed reliably in a short time.

Next, FIG. 6 shows another embodiment of the present invention. This embodiment differs from the embodiment of FIG. 1 in that an input current detector 28 of the thyristor power converter is provided, which allows the G
The point is that BI, QB2, and GB are each generated by the arithmetic unit 29 shown in FIG. In the embodiment shown in FIG. 7, the same parts as in the embodiment shown in FIG. 1 are given the same reference numerals.

In FIG. 7, 291 is a zero detector that takes in the detected value of the input current of the thyristor power conversion device detected by the current detector 27 and detects its zero value. This signal is supplied to the OR circuit 292, which has a level of 0 when the signal is zero, and a level 1 when the signal is other than zero.

293 is triggered by the level of the input signal 29a falling from 1 to O for a predetermined period T 11114
This is a holding circuit that holds the output signal 29a at level 1 during this period.

Similarly, 295 is the output signal 29c of the AND circuit 294.
This is a holding circuit that maintains the output signal 29e at level 1 for a predetermined period T8, 3 after the level changes from 1 to O.

Furthermore, 296 is an integrator that functions to measure the time during which the signal 29c is at level 1, that is, the time from when the electric valve 22 is opened until the current of the thyristor power conversion device becomes zero, and 297 is a comparator that outputs a trip signal ST when the output signal 29d of the integral m296 becomes larger than the signal 29g output from the time setting circuit 298.

Next, the operation of this embodiment will be explained with reference to the waveform diagram of FIG.

Now, at time point ■, the zero detector 291 detects that all three-phase currents of the thyristor power conversion device have become zero.
Assuming that the signal 29a changes to level O, the signal GB2 disappears after a predetermined period of time TxW4 has elapsed from this point, and similarly, the signals GBI and GB disappear when a predetermined period of TxW4 has elapsed from this point. disappears.

Therefore, according to this embodiment, the opening control of the electric valve 22 is performed only after it is reliably detected that all the currents in the thyristor power conversion device have become zero, and highly reliable control is obtained. be able to.

Further, according to this embodiment, if the current of the thyristor power conversion device does not become zero even after a predetermined period has passed after the electric valve 22 is controlled to open, the trip signal ST is set to Since the power is generated from the power converter 297, the Cyrisk power converter can be sufficiently protected.

[Effect of the invention] According to the present invention, at the time of AC system failure, or.

First, when protecting the secondary circuit of an AC-excited synchronous machine by short-circuiting it with an electric valve during an emergency stop, etc.

Since the current limiting resistor is short-circuited directly by the electric valve, the current of the thyristor power converter can be reliably interrupted.

In addition, after a predetermined period of time, the short circuit occurs with the current limiting resistor inserted, so there is no risk of causing large fluctuations in the AC system, and operation can be controlled in a stable state to provide sufficient protection. can.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a thyristor power conversion device in an embodiment of the AC excitation synchronous machine control device according to the present invention;
Fig. 2 is a block diagram of an AC excitation synchronous machine control device to which the present invention is applied, Fig. 3 is a block diagram showing one embodiment of the calculation section, and Figs. 4 and 5 are waveform diagrams for explaining the operation. , FIG. 6 is a block diagram showing a thyristor power conversion device in another embodiment of the present invention, FIG. 7 is a block diagram showing another embodiment of the calculation section, and FIG. 8 is a waveform for explaining the operation. 9 is a block diagram showing a conventional example of an AC excitation synchronous machine control device, and FIG. 10 is a block diagram showing a conventional example of a thyristor power conversion device. FIG. FIG. 12 and FIG. 13 are waveform diagrams for explaining the operation. 1... AC system, 2... AC excitation synchronous machine, 3... Phase detector, 6... Current command calculator, 11... ...Current detector, 12...
...Current control device, 13... Phase shifter, 16...
... Polarity switching command generator, 17... Forward/reverse switching logic circuit, 18... Current zero detector, 19...
...First electric valve, 20...Current limiting resistor, 21
... Arithmetic circuit, 22 ... Second electric valve,
24... Effective current detector, 25...q
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Claims (1)

[Claims] 1. AC excitation power for excitation of the secondary winding is obtained by a non-circulating current type cycloconverter, and the generation of abnormal voltage on the secondary winding side by the cycloconverter is suppressed by the first electron In an AC-excited synchronous machine that uses a switch to connect current-limiting resistors in parallel, a second electronic switch connected in parallel to the current-limiting resistor is provided to close the first electronic switch when an abnormal voltage occurs. After the second electronic switch is controlled to close substantially in synchronization with the opening control, the second electronic switch is controlled to open prior to the opening control of the first electronic switch. AC excitation synchronous machine control device. 2. In claim 1, the above-mentioned first and second
An AC excitation synchronous machine control device characterized in that the electronic switch is composed of two thyristors connected in antiparallel.