WO2010083639A1

WO2010083639A1 - Two-control-three precharging phase-controlled switch circuit for switching capacitor bank

Info

Publication number: WO2010083639A1
Application number: PCT/CN2009/001565
Authority: WO
Inventors: 杨建宁
Original assignee: 北京馨容纵横科技发展有限公司
Priority date: 2009-01-21
Filing date: 2009-12-28
Publication date: 2010-07-29

Abstract

A two-control-three precharging phase-controlled switch circuit for switching a capacitor bank includes two phase-controlled switches (K1, K2) for precharging the capacitor bank which constitute a three-phase zero-point switch. The input terminals of the two phase-controlled switches (K1, K2) are connected respectively to LC series filter circuits (L1, C1, L2, C2) of two phases, and the output terminals are connected together to an LC series filter circuit (L3, C3) of a third phase. The LC series filter circuits (L1, C1, L2, C2, L3, C3) with a star connection are connected to a three-phase electric network power supply via high-voltage fuses (F1, F2, F3). A phase control device controls independently the two phase-controlled switches (K1, K2) to be switched on/off at peak points of voltage according to a time sequence. Each of the phase-controlled switches (K1, K2) is connected in parallel with a series circuit of a high-voltage silicon stack diode (D1, D2) and a high-voltage current limiting resistor (R1, R3) for realizing the function of precharging the capacitor bank, and is connected in parallel with an RC series absorbing circuit (R2, C4, R4, C5). The two-control-three precharging phase-controlled switch circuit can perform one non-impact switching operation within one second with reduced cost.

Description

2 control 3 precharge phase control switch circuit for switching capacitor bank

The invention relates to a 2-control 3 pre-charging phase-controlled switch circuit for a switching capacitor bank, which is used in a power quality control project of a power grid, and can realize a fast non-inrush current input of a capacitor bank and a current zero-crossing cutting, belonging to a power system Field of reactive power compensation and harmonic filtering technology.

Background technique

The conventional circuit of the switching capacitor bank is: mechanical contact switching switch, thyristor switching capacitor (TSC), synchronous vacuum switch.

The mechanical contact switch switch, the three-phase switch cuts the capacitor at a randomly uncertain grid voltage point, the current impact is large, and the rated current is the least, which causes the grid voltage distortion. There is also a risk that the closing mechanical contact bounces and the re-ignition of the contact is opened. The re-ignition of the bounce makes the capacitor bank overvoltage and damages the capacitor, which is likely to cause an accident.

The Thyristor Switching Capacitor (TSC) circuit can be accurately placed into the capacitor without current surge. There is no problem of bounce and re-ignition. However, in the medium voltage TSC circuit, the thyristor has to withstand about three times the grid effect voltage. The thyristor has a withstand voltage of only a few KV. It requires multiple thyristors in series. The thyristor conducts a tube voltage drop of about 2V, and a current flow of several hundred amperes. Through the thyristor, the loss heat is large, and a set of medium voltage TSC circuit generates several KW of heat when it is turned on, which consumes a large amount of energy. Such a large amount of heat needs to be cooled by air cooling, water cooling, heat pipes, and the like. TSC technology is difficult and costly.

The phase-controlled switch currently applied in engineering is also called synchronous vacuum switch or synchronous switch, such as the patent document "synchronous switch", patent number: ZL98808789. 8, patent document "phase control switch device", patent number: ZL99118416. 5, patent File: "Phase control switchgear", application number: 00137229. 7 also has 3 points: There are many synchronous switching elements, only the closing impulse current is reduced, and the operating time is the same as the normal mechanical contact switching switch. The phase-control switch of the switching capacitor group or the synchronous vacuum switch has three switches, and the switching elements are more; the phase-switching switching capacitor group works, and the switches are closed at the zero-crossing point of the sine wave voltage. When there is no voltage on the capacitor, only the effect of switching the capacitor is good. At the zero crossing of the sine wave, the voltage change rate is the highest, which requires the accuracy of the synchronous switch to be high. On page 15/19 of the patent document "Synchronous Switch", the accuracy of the switch is ± lms of the zero-crossing point, and the impact level is half that of a normal mechanical contact switch, which is equivalent to the level of the series-resistance switching capacitor. The higher the impact, the smaller the impact. It can be seen that there is still no small impact; after the switch is turned on, it needs to wait for the charging voltage on the capacitor to drop to zero before it can be closed again. The waiting time is a few minutes, and the switching action of the switch is minute level. It is not possible to switch the capacitor bank quickly and without inrush current.

The emergence of thyristor switching capacitor banks and phase-controlled switching technology has a history of nearly 30 years. There are applications in engineering, but the application is not large.

In the field of medium voltage dynamic reactive power compensation and harmonic filtering technology, a widely used scheme at home and abroad is a filter circuit (FC) composed of a thyristor control reactor (TCR) + a capacitor and a reactor. However, TCR has disadvantages: TCR+FC completes the grid compensation, and needs to do another reactive power of the same size as the reactive power that needs to be filtered. The thyristor is used to control the reactive power. In this way, the user's investment is large, and the TCR itself needs about 120 yuan / KV R., which covers a large area and consumes a large amount of energy, which is considered to be 3%. The 100MVAR TCR has 3MAW energy consumption, which is really a lot. Harmonic current is generated during TCR operation and filtered by FC. Although TCR has shortcomings, there is currently no better solution or means to replace TCR. Summary of the invention

The invention creates a new type of switching circuit, and its positioning: TCR+FC in the field of torsional medium voltage dynamic compensation; overcomes the shortcomings of high cost and large energy consumption of the thyristor switching capacitor bank (TSC); The speed limit of the phase control switch is shortened, the action time is shortened, and one action is completed from opening to closing. The time is within 1 second. The closing does not generate current shock, and the opening current is zero. The conventional three-phase phase control switch is reduced by three. The structure of an independent switch, using only two independent switches to complete the three-phase opening and closing action, called 2 control 3; pre-charging the capacitor bank, switching the switch at the peak of the voltage, the switching accuracy is better than the traditional phase-controlled switch Low, the effect is better than the traditional phase-controlled switch, which means low cost, high quality, and acceptable for users. Energy saving and environmental protection, no energy consumption, in line with the requirements of the times.

The invention is realized by the following scheme: Two phase-control switches for pre-charging the capacitor bank form a 3-phase zero-point switch, a series filter circuit of the input terminals of the two phase-controlled switches and the two-phase star-connected reactor L and capacitor C Connected, the output terminals of the two phase-controlled switches are connected together with the LC filter circuit of the third phase, and the star-connected LC filter circuit is connected to the three-phase grid power supply through the high-voltage fuse, and the phase control device independently controls the two according to the timing. Only the phase control switch is turned on and off at the peak point of the voltage. When the zero switch is closed, the potential is zero, and the circuit works safely; the short-circuit current of the zero-point switch is small and safe when the phase-to-phase short circuit occurs in the device.

The phase-control switch for pre-charging the capacitor bank is connected in parallel with a series circuit of a high-voltage silicon stack diode and a high-voltage current limiting resistor in parallel with each phase-controlled switch to achieve pre-charging of the capacitor bank; A series absorption circuit of capacitor C and resistor R absorbs the rapidly changing voltage across the switch.

The cathodes of the two high voltage silicon stack diodes of the phase control switch pre-charging the capacitor bank are connected to the power supply side of the switch, or the anodes of the two high voltage silicon stack diodes are connected to the power supply side of the switch.

The phase control switch is usually a permanent magnet vacuum contactor or a permanent magnet vacuum switch, or an electromagnetic vacuum contactor or an electromagnetic vacuum switch.

The phase control device independently controls the two phase-controlled switches to turn on and off at the peak of the voltage according to the timing. When the grid voltage is connected in the positive sequence, that is, the V phase of the grid voltage lags behind the U phase by 120°, and the W phase leads In the U phase 120°, the switch K1 is installed in the U phase, the switch K2 is installed in the V phase, and the cathodes of the two rolled silicon stack diodes are connected to the power supply side of the switch, and when the switch S1 is put into command operation, the switch is K0's zero-crossing point, that is, the negative peak point of the line voltage VW, closes the switch K2, delays 15ms, at the negative peak point of the phase voltage U phase, closes the switch Kl, realizes no current impact and puts into operation; receives the changeover switch S1 to stop the command At the time of stop, at the negative peak point of the phase voltage U phase, the current is zero to open the switch K1, then, at the negative peak point of the line voltage VW, the current is zero to open the switch Κ2. There is no inrush current when the switch is closed, and the effect of opening the switch when the current is zero.

The phase control device independently controls two phase-controlled switches to turn on and off at a peak point of the voltage according to timing. When the grid voltage is connected in a positive sequence, the cathodes of the two high-voltage silicon stack diodes are connected to the power supply side of the switch. No change, two phase-controlled switches can be connected to any two phases of the 3-phase circuit. The switch Kl and switch Κ2 are connected to different phases. As long as the synchronous voltage signal is adjusted accordingly, the control program is unchanged, and the switch is closed and opened. Kl, switch Κ2, also has no inrush current when the switch is closed, and the effect of opening the switch when the current is zero.

The phase control device is composed of a grid voltage synchronous detector, a single chip phase selection controller, and a permanent magnet coil driver. The coil power supply is powered by a DC 220V regulated power supply. The circuit of the phase control device is similar to the control circuit of the conventional phase-controlled switch published in the magazine. It is known to the skilled person, so it is not exhaustive. The following describes the requirements of phase sequence control, monolithic After the switch selects the SI switch input command, the machine selects the voltage synchronization signal from the grid voltage synchronous detector, and issues a closed command to the permanent magnet coil driver according to the requirements of the sequence program. The permanent magnet coil driver outputs the drive current. , the switch K1 and the switch Κ2 are closed at their respective predetermined points, the switch K1 and the switch Κ2 are kept closed by the permanent magnet suction, and the coil has no current; the single-chip phase selection controller obtains the switch S1 switch cut command after the switch, and according to the grid voltage synchronous detection The voltage synchronizing signal from the device sends an open command to the permanent magnet coil driver according to the requirements of the timing program, and the permanent magnet coil driver outputs an inverting driving current, so that the switch K1 and the switch Κ2 are turned on at their respective predetermined points. If the switch K1 and the switch Κ2 are driven by the electromagnetic coil, the switch is closed, the coil is always powered, the switch is turned on, and the coil is de-energized.

The position of the switching elements in the series circuit can be changed. The principle is unchanged. Two phase-controlled switches pre-charging the capacitor bank form a 3-phase switch, and the input terminals are connected to the two phases of the three-phase power supply through a high-voltage fuse. The output end is connected to the series filter circuit of the two-phase reactor L and the capacitor C, and the series filter circuit of the other phase reactor L and the capacitor C is directly connected to the third phase of the three-phase grid power supply through the high voltage fuse; The series filter circuit of the reactor L of the three-phase circuit and the capacitor C may be wired in a star shape or a triangle shape.

The 2 control 3 circuit is operated in a three-phase circuit. There are only two circuit switches, one less. As mentioned above, the timing control of the circuit operation is very complicated. There are many circuit types of switch-switching capacitors. For example, capacitors and reactors are connected in series to form a triangle. The switch is placed in a triangular arm. The capacitor is switched by three switches. The operation of the switch is a single-phase operation mode, which is simpler than the 2-control type 3. The phase-controlled switch of the present invention for precharging a capacitor bank is equally applicable to a circuit in which a switch is mounted in a triangle and a single-phase switching circuit.

The 2-control 3-precharge phase-controlled switching circuit of the switching capacitor bank is applied to the pre-charging technology of the capacitor bank, and the capacitor is switched at the peak point of the grid voltage, which is an ideal state without an inrush current, and the accuracy of the switch is required to be low. The use of an ordinary switch can achieve the function of a high-precision phase-controlled switch. With an ordinary switch, the cost is reduced and the user can accept it. The circuit assembled according to the above requirements is switched to the capacitor bank. The test data shows that the expected result is achieved: Closed without operating overvoltage and no inrush current, the switch is turned on when the current crosses zero; at the same time, the effect of the approximate thyristor switching capacitor bank is achieved. The quick action, from the opening to the closing, completes the action once in one second; the switch is opened, and the action is stopped for a long time in ten days. When the action is performed again, the action value of the test current voltage does not change, and the safe and reliable requirement is achieved. The newly invented switch can be used in low voltage (1KV or less), medium voltage (1KV < medium voltage <=35KV), high voltage (>35KV) wide voltage range, TCR is not used in 110KV power grid, in the power distribution grid System, TC series, metallurgical industry, mining, electrified railway and other fields of application, to reverse the medium pressure dynamic compensation TCR + FC - the expected goal of the world has seen the dawn.

DRAWINGS

Figure 1: Switching capacitor bank 2 control 3 zero pre-charge phase control switch circuit circuit diagram

Figure 2: Open and close once in 1 second, switch K1 current, switch K2 voltage working waveform

Figure 3: Waveform expansion: Switch K1 current, switch K2 voltage working waveform when closed

Figure 4: Waveform expansion: When opening K1 current, switch K2 voltage operation waveform

Figure 5: Open and close once in 1 second, switch K2 current, switch K1 voltage working waveform

Figure 6: Waveform expansion: Switching K2 current, switch K1 voltage working waveform when closed

Figure 7: Waveform expansion: Switch K2 current, switch K1 voltage operation waveform when open Figure 8: Circuit diagram of 2-control 3 precharge phase-controlled switch for switching star-connected capacitor bank

Figure 9: Switching the delta connection capacitor bank 2 control 3 precharge phase control switch circuit diagram

Figure 10: Circuit diagram of the capacitor bank connected in a triangle, pre-charged phase-controlled switch mounted in a triangular arm'

Detailed ways

See Figure 1-10 for details.

Please refer to Figure 1 and Figure 7: Two phase-control switches K1 and K2 for pre-charging the capacitor bank form a 3-phase zero-point switch. The switch K1 is connected in parallel with the series circuit of the high-voltage silicon stack diode D1 and the high-voltage current limiting resistor R1. The effect of precharging the capacitor bank is achieved; at the same time, the series absorption circuit of the capacitor C4 and the resistor R2 is connected in parallel to absorb the rapidly changing voltage on the switch K1. The series circuit of the high voltage silicon stack diode D2 and the high voltage current limiting resistor R3 is connected in parallel to the switch K2 to achieve the function of precharging the capacitor bank; at the same time, the series absorption circuit of the capacitor C5 and the resistor R4 is connected in parallel, and the absorption switch K2 is fast. Varying voltage. The input end of the switch K1 is connected with the series filter circuit of the reactor L1 and the capacitor C1, and the L1, C1 filter circuit is connected with the three-phase grid power source U through the high voltage fuse F1, the input end of the switch K2 and the reactor L2 and the capacitor C2 The series filter circuit is connected, the L2 and C2 filter circuits are connected to the three-phase grid power supply V through the high voltage fuse F2, and the output ends of the switch K1 and the switch Κ2 are connected together, and are connected with the series filter circuit of the reactor L3 and the capacitor C3, L3, The C3 filter circuit is connected to the three-phase grid power supply V via a high voltage fuse F3. The cathode of the high voltage silicon stack diode D1 is connected to the capacitor C1, the anode of the high voltage silicon stack diode D1 is connected to the high voltage resistor R1; the cathode of the high voltage silicon stack diode D2 is connected to the capacitor C2, and the anode of the high voltage silicon stack diode D2 is connected to the high voltage resistor R2. There are many advantages to connecting the phase-locked switch that pre-charges the capacitor bank to the zero point of the star-connected capacitor bank: When the zero-point switch is closed, the potential is zero, the circuit works safely; the short-circuit current of the zero-point switch occurs when the device is short-circuited between phases Small, safe.

The phase control device is composed of a grid voltage synchronous detector 1, a single chip phase selection controller 2, and a permanent magnet coil driver 5. The coil power supply is powered by a DC 220V regulated power supply 4. The circuit of the phase control device is similar to the control circuit of the conventional phase-controlled switch published in the journal of Science and Technology, and is not known to those skilled in the art. The following describes the requirements of phase sequence control. When the grid voltage is wired in the positive sequence, that is, the V phase of the grid voltage lags behind the U phase by 120°, and the W phase leads the U phase by 120°. The MCU phase selection controller 2 obtains the changeover switch S1. After the input command 3 is input, the switch K2 is closed at the zero-crossing point of the switch K2, that is, the negative peak point of the line voltage VW, and the delay is 15 ms. At the negative peak point of the phase voltage U phase, the switch K1 is closed to achieve no current surge. Putting into operation; After receiving the stop command S1 switching command 3 stop command, at the negative peak point of the phase voltage U phase, the current turns to the switch K1 at zero point, then, at the negative peak point of the line voltage VW, the current turns to the switch Κ2 at zero point.

The voltage and current waveforms of test switch Kl and switch Κ2 are shown in Figure 2-7. Figure 2 and Figure 5 have an abscissa of 200ms. Figure 2 and Figure 5 show the waveforms of one open and one closed for one second. The abscissa of Figure 3, Figure 4, Figure 6, and Figure 7 is 20ms. Amplification, observation switch Kl, switch Κ2 input and cutoff voltage, current waveform, it can be seen that the switch is at the peak point of the grid voltage, the switch voltage is zero when closed, no inrush current, when the current is zero, the switch is turned on, the phase switch It is connected in series with the reactor and capacitor filter circuit, the current is the same, the current of each phase control switch has no impact, and the reactor and capacitor filter circuit in series with the phase control switch have no current impact. Switching capacitor bank 2 control 3 pre-charging phase-controlled switching circuit switching effect is similar to thyristor switching capacitor group, better than the conventional phase-controlled switch or phase selection switch.

The main component selection of a specific embodiment: 2 of the switching capacitor bank applied to the grid voltage 10KV current 200Α Control 3 zero pre-charge phase control switch circuit, phase control switch Kl, phase control switch Κ 2 adopt ordinary single-phase permanent magnet contactor, type CKG4-250/12-DY, high voltage silicon stack diode voltage is 60KV, current 1Α, and high voltage The high-voltage current limiting resistor of the silicon stack diode is 12KV, 10K ohm, 500W high-voltage resistor. The series circuit of the capacitor C and the resistor R connected in parallel with the phase-controlled switch is an RC absorber connected to the power grid power line. The high voltage fuse has a voltage of 12KV and a current of 300A.

The phase control device independently controls two phase-controlled switches to turn on and off at a peak point of the voltage according to timing. When the grid voltage is connected in a positive sequence, the cathodes of the two high-voltage silicon stack diodes are connected to the power supply side of the switch. Unchanged, two phase-controlled switches can be connected to any two phases of the 3-phase circuit. Switch K1 and switch Κ2 are connected to different phases. As long as the synchronous voltage signal is adjusted accordingly, the control program is unchanged, and the switch is closed and opened. Kl, switch Κ2, also has no inrush current when the switch is closed, and the effect of opening the switch when the current is zero.

See Figure 8: The position of the switching elements in the series circuit can be changed. The principle is unchanged. Two phase-control switches K1 and phase-control switch Κ2 for pre-charging the capacitor bank form a 3-phase switch. The input terminals are connected to the U and V phases of the three-phase power supply through high-voltage fuses F1 and F2. The two-phase reactor L and the series filter circuit of the capacitor C are connected, and the series filter circuit of the other phase reactor L3 and the capacitor C3 is directly connected to the W phase of the three-phase grid power supply through the high-voltage fuse F3; The series filter circuit of reactor L and capacitor C is wired in a star shape. The series filter circuit of the reactor L of the three-phase circuit and the capacitor C can also be connected in a delta connection, as shown in Fig. 9.

The 2 control 3 circuit is operated in a three-phase circuit. There are only two circuit switches, one less. As mentioned above, the phase operation control of the circuit operation is very complicated. There are many circuit types of switching capacitors. For example, capacitors and reactors are connected in series to form a triangle. The switch is placed in a triangular arm. As shown in Fig. 10, the capacitor is switched by three switches. The operation of the switch is a single-phase operation mode. The type 3 is simple, and the phase-control switch for precharging the capacitor bank of the present invention is also applicable to the circuit in which the switch of FIG. 10 is mounted in a triangle and the single-phase switching circuit.

The present invention has been described in detail with reference to the preferred embodiments of the present invention, and any obvious modifications made thereto without departing from the spirit of the invention The violation will bear the corresponding legal responsibility.

Claims

Claim

1. A 2-control 3-precharge phase-controlled switch circuit for switching capacitor banks, characterized in that: two phase-controlled switches for pre-charging the capacitor bank form a 3-phase zero-point switch, and two phase-control switch inputs and two The star-connected reactor L and the capacitor C are connected in series, the output terminals of the two R-phase switches are connected together with the LC filter circuit of the third phase, and the star-connected LC filter circuit is blown through the high voltage. The device is connected to the three-phase grid power supply, and the phase control device independently controls the two phase-controlled switches to turn on and off at the peak of the voltage according to the timing.

2. The 2-control 3-precharge phase-controlled switch circuit of a switching capacitor bank according to claim 1, wherein: in parallel with each phase-controlled switch, a series connection of a high-voltage silicon stack diode and a high-voltage current limiting resistor is connected in parallel The circuit achieves the effect of precharging the capacitor bank; at the same time, the series absorption circuit of the capacitor C and the resistor R is connected in parallel to absorb the rapidly changing voltage on the switch.

3. The 2-control 3-precharge phase-controlled switch circuit of a switching capacitor bank according to claim 1, wherein: the cathodes of the two high-voltage silicon stack diodes adjacent to the phase-controlled switch are connected to the power supply side of the switch, or The anodes of the two high voltage silicon stack diodes are connected to the power supply side of the switch.

4. The 2-control 3-precharge phase-controlled switch circuit of a switching capacitor bank according to claim 1, wherein: the phase-controlled switch is usually a permanent magnet vacuum contactor or a permanent magnet vacuum switch, or Electromagnetic vacuum contactor or electromagnetic vacuum switch.

5. The 2-control 3 precharge phase-controlled switch circuit of a switching capacitor bank according to claim 1, wherein: said phase control device independently controls two phase-controlled switches at a peak point of voltage according to timing On-off, when the grid voltage is wired in the positive sequence, that is, the V phase of the grid voltage lags behind the U phase 120 ^Q , and the W phase leads the U phase by 120°. The gate K1 is installed in the U phase, and the switch K2 is installed in the V phase. The cathodes of the two high-voltage silicon stack diodes are connected to the power supply side of the switch. When the switch S1 is put into command operation, the zero-crossing point of the switch K2, that is, the negative peak point of the line voltage VW, closes the switch K2, and the delay is 15ms. At the negative peak point of the phase voltage U phase, the switch K1 is closed to achieve the no-current impact input operation; when the transfer switch S1 stops the command to stop, at the negative peak point of the phase voltage U phase, the current turns to the switch K1, and then, At the negative peak point of the line voltage VW, the current is zero to turn on the switch Κ2.

6. The 2-control 3 precharge phase-controlled switch circuit of a switching capacitor bank according to claim 1, wherein: said phase control device independently controls two phase-controlled switches at a peak point of voltage according to timing On-off, when the grid voltage is wired in the positive sequence, the cathodes of the two high-voltage silicon stack diodes are connected to the power supply side of the switch, and the two phase-control switches that pre-charge the capacitor bank can be connected to any of the 3-phase circuits. On two phases, the switch Kl and the switch Κ2 are connected to different phases. As long as the synchronous voltage signal is adjusted accordingly, the control program is unchanged, and the switch K1 and the switch Κ2 are closed and opened, and the inrush current is also obtained when the switch is closed. The effect of opening the switch at zero hour.

7. The 2-control 3 precharge phase-controlled switch circuit of a switching capacitor bank according to claim 1, wherein: the front and rear positions of the switching elements of the series circuit can be changed, the principle is unchanged, and two capacitor banks are provided. The pre-charged phase-control switch constitutes a 3-phase switch, the input end of which is connected to the two phases of the three-phase grid power supply through a high-voltage fuse, and the output end thereof is connected with the series filter circuit of the two-phase reactor L and the capacitor C, and the other phase The series filter circuit of reactor L and capacitor C is directly connected to the third phase of the three-phase grid power supply through the high voltage fuse; at this time, the wiring of the series filter circuit of the reactor L of the three-phase circuit and the capacitor C can be star-shaped. It can also be a triangle.

8. The 2-control 3-precharge phase-controlled switch circuit of a switching capacitor bank according to claim 1, wherein: The circuit is operated in a three-phase circuit. There are only two switches and one less. As mentioned above, the circuit operation requires a very complicated timing system. There are many circuit types for switching capacitors. For example, capacitors and reactors are connected in series to form a triangle. The switch is placed in a triangular arm. The capacitor is switched by three switches. The operation of the switch is a single-phase operation, which is simpler than the 2-control type 3. The phase-locked switch of the capacitor bank pre-charging of the present invention is also applicable to a circuit in which a switch is mounted in a triangle and a single-phase switching circuit.