CN110011323A - Distribution network series capacitance compensation device and compensation method capable of suppressing subsynchronous resonance - Google Patents

Abstract

The invention discloses a power distribution network series capacitance compensation device and a compensation method capable of suppressing subsynchronous resonance. The series capacitance compensation device is composed of a compensation unit and a subsynchronous resonance suppression unit. Compensation units include capacitors, damping circuits, voltage limiters, and bypass circuit breakers to improve voltage quality at continuous operating voltages. The subsynchronous resonance suppression unit includes an inductance coil, a thyristor and a control branch. The control branch consists of a power supply, a band-pass filter, a rectifier circuit, a voltage comparator and a trigger circuit. When the compensation unit and the power distribution system have a subsynchronous resonance, the The pass filter monitors the subsynchronous resonant frequency and voltage signal of the distribution network in real time. After filtering, the AC signal is converted into a DC signal by the rectifier circuit, which is transmitted to the voltage comparator for comparison, and then output to the trigger circuit for processing to trigger the thyristor. Reliable conduction. The power supply provides working power for the subsynchronous resonance unit.

Description

Distribution network series capacitance compensation device and compensation method capable of suppressing subsynchronous resonance

technical field

The invention belongs to the technical field of power system series compensation, and in particular relates to series capacitance compensation and power electronics technology.

Background technique

In order to meet the power demand of various loads, the power system needs to provide active power and reactive power that meet the voltage quality. It is economical to ensure the voltage quality and reactive power demand through the series capacitor compensation device. The series capacitor reactive power compensation device provides a means to improve the voltage quality and provide reactive power forward with the operating voltage. Series capacitors can directly compensate for transmission line reactance and improve voltage quality. This is the main reason for using series capacitor compensation. It improves power system stability and helps control line voltage drops. The series capacitor is passive, it functions without external control or dispatcher action.

In 1970, when a 750MVA parallel double shaft steam turbine generator set in the Mohave project in southern Nevada state was radially connected to the Lugo busbar of the 283km (176mile) transmission line with series capacitance compensation equipment in southern California in the 500kV transmission system, a crankshaft occurred. damage. Almost exactly the same event happened again in 1971. The accident report shows that the accident was caused by the subsynchronous resonance (SSR) between the series capacitor and the steam turbine generator set during the transient process of switching the generator set.

The Mohave incident made people aware of the potential dangers of subsynchronous resonance in devices using series capacitor compensation. This forces all utilities that are using or planning to use series capacitance compensation devices to consider other alternatives or containment measures. The main alternative is to reduce the inductive reactance of the transmission line, use a higher transmission voltage, or use methods such as parallel compensation, controllable voltage regulation, and DC transmission. These methods require higher capital investment and increase the impact on system reliability and environment. Therefore, from the perspective of comprehensive benefits, series capacitor compensation is an efficient and economical means to improve voltage quality and perform reactive power compensation, but first, the problem of suppressing subsynchronous resonance must be solved.

SUMMARY OF THE INVENTION

In order to solve the above problem, the present invention provides a distribution network series capacitance compensation device and compensation method capable of suppressing subsynchronous resonance, suppressing the further development of subsynchronous resonance, and improving the voltage quality in the distribution network system.

In order to achieve the above purpose, a power distribution network series capacitance compensation device capable of suppressing subsynchronous resonance of the present invention includes a set of capacitors C, an inductive coil L1, an inductive coil L2, a damping resistor R, a thyristor group V and its control branch. circuit, a set of voltage limiter F, bypass circuit breaker QF1 and circuit breaker QF2, the series capacitance compensation device is divided into two parts: compensation unit and subsynchronous resonance suppression unit. All components of this device are composed of three phases A, B and C. .

In the compensation unit, the capacitor is used to compensate the voltage drop of the distribution network line, so that the voltage of each node of the distribution network line meets the specified power quality requirements. Capacitor is the core component of series compensation, which is used to compensate the voltage drop in the distribution network line. The size of its capacitance and its connection and withdrawal directly affect the compensation effect of the voltage along the line. The size of the capacitor's capacitance, line inductance and compensation degree relevant, 500µF. The inductance coil L2 is used as a damping inductance in parallel with the damping resistance R, and then in series with a fast circuit breaker, and the whole is in parallel with the capacitor. The voltage limiter F and the bypass circuit breaker QF1 are connected in parallel at both ends of the series compensation device.

In the subsynchronous resonance suppression unit, the inductance coil L1 and the thyristor group are connected in series, and the formed series branch is connected in parallel with the capacitor C, and the control branch is used to control the on-off of the thyristor group.

The control branch is divided into six parts: power supply system, monitoring equipment, band-pass filter, rectifier circuit, voltage comparator, trigger circuit. The monitoring equipment monitors the voltage signal of the equipment in operation in real time (the voltage signal includes the voltage signal including the voltage amplitude and the voltage frequency), and transmits the distribution network voltage signal to the band-pass filter, which is used to filter out the set frequency. The AC voltage signal within the set frequency range is obtained, and the AC voltage signal within the set frequency range is transmitted to the rectifier circuit. After processing by the band-pass filter, the AC signal is converted into a DC signal by the rectifier circuit. It is transmitted to the voltage comparator for comparison, and finally output to the trigger circuit for processing to ensure the reliable conduction of the thyristor group. The power supply provides power for monitoring equipment, band-pass filters, rectifier circuits, voltage comparators, and trigger circuits.

A distribution network series compensation method for suppressing subsynchronous resonance based on the above-mentioned capacitance compensation device, when subsynchronous resonance occurs in the distribution network system, a signal is transmitted to the gate of the thyristor group V, so that the thyristor group V is turned on, so that the The inductance coil L1 is connected to the circuit and is connected in parallel with the capacitor C to suppress the further development of the subsynchronous resonance; when the subsynchronous resonance disappears, a signal is transmitted to the gate of the thyristor group V, so that the group thyristor group V is turned off, and the inductance coil is cut off. L1, makes the series capacitor compensation device appear capacitive as a whole, and continues to play the role of compensating for the voltage drop of the distribution network line.

Further, the control branch transmits the signal to the gate of the thyristor group V, and the control branch includes monitoring equipment, band-pass filter, rectifier circuit, voltage comparator and trigger circuit. The voltage is transmitted to the band-pass filter, the band-pass filter filters out the voltage signal outside the set frequency, obtains the AC voltage signal within the set frequency range, and transmits the AC voltage signal within the set frequency range to the rectifier circuit, rectifying The circuit converts the received AC voltage signal within the set frequency range into a DC voltage signal, and the voltage comparator compares the DC voltage signal with the threshold, and outputs a high-potential signal or a low-potential signal to the trigger circuit. The high-potential signal or low-potential signal controls the thyristor group V to be turned on or off.

Compared with the prior art, the present invention has at least the following beneficial technical effects: when the sub-synchronous resonance occurs in the distribution network system, a signal is transmitted to the gate of the thyristor group, so that the thyristor group is in a conducting state as a whole, and the inductance coil L1 is connected. Into the circuit, in parallel with the compensation capacitor, to suppress the further development of subsynchronous resonance. When the subsynchronous resonance disappears, the signal is transmitted to the gate of the thyristor group, so that the group of thyristor group is turned off as a whole, and the inductance coil L1 is cut off, so that the series capacitance compensation device is overall capacitive, and continues to compensate the distribution network line voltage. effect of landing. The device has three-phase integration, simple structure and light weight, and can realize voltage quality adjustment and reactive power compensation for the line according to the expected compensation degree;

Further, the compensation unit also includes a voltage limiter. The voltage limiter F is connected in parallel with both ends of the capacitor C to limit the overvoltage and current that may appear at the two ends of the series capacitor compensation device and prevent the equipment insulation from being damaged.

Further, the compensation unit also includes an inductor coil L2, a damping resistor R and a circuit breaker QF2, the inductor coil L2 and the damping resistor R are connected in parallel to form a damping circuit, and the damping circuit and the circuit breaker QF2 are connected in series to form a bypass branch, the bypass branch and the capacitor. C in parallel. Damping loops are used to dampen capacitor discharge current and oscillations when the circuit breaker is closed.

Further, the capacitor C is also connected in parallel with the bypass circuit breaker QF1, and is used when the series capacitance compensation device is overhauled, which can bypass the entire series capacitance compensation device.

Further, the thyristor group V is controlled by the control branch to be turned on or off according to the grid voltage. The control branch includes monitoring equipment, the input terminal of the monitoring equipment is connected to the grid, the output terminal of the monitoring equipment is connected to the input terminal of the band-pass filter, the output terminal of the band-pass filter is connected to the input terminal of the rectifier circuit, and the output terminal of the rectifier circuit is connected. The terminal is connected with the input terminal of the voltage comparator, the output terminal of the voltage comparator is connected with the input terminal of the trigger circuit, and the output terminal of the trigger circuit is connected with the thyristor group V;

Further, it can effectively and quickly suppress the 20Hz-40Hz synchronous resonance, and use the frequency and amplitude dual characteristic quantities to compare and identify, with high accuracy, fast control and adjustment, stable performance, and is not affected by system operating conditions;

Further, the working power source of the power electronic device is taken from solar energy, which is long-lasting, clean and environmentally friendly, and no additional cost is required in the later stage.

In addition, the number of components required for the control unit is small, and the cost is not high. The control branch exists independently of the compensation unit. If the control branch fails, it can be removed and replaced separately, and the removal of the control branch for replacement will not affect the work of the compensation unit. The control branch is easy to replace.

A compensation method for a series capacitor compensation device in a distribution network that can suppress subsynchronous resonance, monitors the voltage and frequency of the power grid in real time, and connects the inductance coil L1 to the power grid according to whether the voltage and frequency of the power grid are controlled to suppress the further development of the subsynchronous resonance. development, and play a role in compensating for the voltage drop of the distribution network line.

Description of drawings

Fig. 1 is the connection schematic diagram of the power distribution network series capacitance compensation device capable of suppressing subsynchronous resonance of the present invention;

2 is a circuit diagram of a power distribution network series capacitance compensation device capable of suppressing subsynchronous resonance according to the present invention;

3 is a system structure diagram of the control branch of the distribution network series capacitance compensation device capable of suppressing subsynchronous resonance according to the present invention;

4 is a circuit diagram of the trigger circuit of the control branch of the distribution network series capacitance compensation device capable of suppressing subsynchronous resonance according to the present invention.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

In the description of the present invention, it should be understood that the terms "installed", "connected" and "connected" should be understood in a broad sense, unless otherwise expressly specified and limited, for example, it may be a fixed connection or a detachable connection Connection, or integral connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations.

The series compensation equipment widely used in the current distribution network system is the fixed series capacitor compensation device. Although the fixed series capacitor compensation device can effectively improve the power quality of the distribution network, once the asynchronous motor occupies a certain proportion of the system load, the secondary Synchronous resonance phenomenon is inevitable. An electrical oscillation circuit is formed between the series capacitor and the load inductance, and the oscillation frequency is the sub-synchronous frequency. Under certain conditions, when the subsynchronous electrical resonant frequency and a certain mechanical torsional oscillation frequency of the generator set shafting increase each other, the shafting will be fatigued, and even more serious will lead to its damage. The invention detects the voltage amplitude and voltage frequency of the sub-synchronous resonance in the system, and mainly determines the sub-synchronous resonance signal by the frequency. Synchronous resonance phenomenon, but also has all the advantages of fixed series capacitor compensation device.

1 is a schematic diagram of the connection of a series capacitance compensation device in a distribution network capable of suppressing subsynchronous resonance according to the present invention. The series capacitance compensation device is controllable. The device is divided into two parts: a compensation unit and a subsynchronous resonance suppression unit. The two parts of the device are composed of three phases A, B, and C. All the following equipments are described with one phase.

Fig. 2 is a circuit diagram of the power distribution network series capacitance compensation device capable of suppressing subsynchronous resonance of the present invention, the series capacitance compensation device comprises a capacitor C, an inductive coil L1, an inductive coil L2, a damping resistor R, and a group of thyristors Group V, a voltage limiter F and bypass circuit breaker QF1 and circuit breaker QF2. The capacitor C is connected between the source side and the load side of the distribution network.

Capacitor C is used to compensate the voltage drop that occurs in the distribution network line, so that the voltage of each node of the distribution network line meets the specified power quality requirements.

The voltage limiter F is composed of non-linear metal oxide resistors, which are connected in parallel at both ends of the capacitor to limit the overvoltage and current that may appear at both ends of the series capacitor compensation device, and prevent the equipment from being damaged. When overvoltage occurs at both ends of the capacitor due to various reasons such as system failure, the excellent nonlinear volt-ampere characteristics, large inrush current capacity and timely response characteristics of the voltage limiter can effectively limit the overvoltage and protect the capacitor. For example, when a short circuit occurs on the load side of a series capacitor compensation device, the voltage across the capacitor increases sharply. The excellent nonlinear volt-ampere characteristics, large inrush current capability and timely response characteristics of the voltage limiter can effectively limit the overvoltage.

The inductance coil L2 is used as a damping inductance in parallel with the damping resistor R to form a damping loop, and is then connected in series with a fast circuit breaker QF2, which is connected in parallel with the capacitor C as a whole. Due to the limitation of manufacturing technology and cost, the energy absorption capacity and voltage withstand capacity of the voltage limiter F are limited, and it cannot absorb a large amount of energy for a long time. Therefore, a fast response circuit breaker is required within the tolerance time allowed by the voltage limiter F. QF2 bypasses the voltage limiter F. The damping loop is used to suppress capacitor discharge current and oscillation when circuit breaker QF2 is closed.

The bypass circuit breaker QF1 is connected in parallel at both ends of the series capacitor compensation device. It is used when the series capacitor compensation device is overhauled, and can bypass the series capacitor compensation device as a whole.

The inductance coil L1 and the thyristor group V are connected in series, and the thyristor group V includes two thyristors connected in anti-parallel. The branch formed by the inductance coil L1 and the thyristor group V in series is connected in parallel with the capacitor C. When the subsynchronous resonance occurs in the distribution network, the gate of the thyristor group V receives the control signal, the thyristor group V is in a conducting state, and the inductance coil L1 is connected in parallel with the capacitor C, which can make the series capacitance compensation device appear inductive or weak as a whole. Further development of subsynchronous resonance.

The control branch of the thyristor group V is used to receive the voltage signal of the distribution network line. When the subsynchronous resonance occurs in the distribution network system, a signal is transmitted to the gate of the thyristor group V, so that the thyristor group V is in a conducting state as a whole, and the inductance coil L1 is connected to the circuit and is connected in parallel with the compensation capacitor to suppress the further development of the subsynchronous resonance. . When the subsynchronous resonance disappears, the signal is transmitted to the gate of the thyristor V, so that the group of thyristors V is turned off as a whole, and the inductor coil L1 is cut off, so that the series capacitor compensation device is capacitive as a whole, and continues to compensate the distribution network lines. The effect of voltage drop.

The control branch includes six parts: power supply, monitoring equipment, band-pass filter, rectifier circuit, voltage comparator and trigger circuit. The control branch monitors the voltage signal of the equipment in operation in real time, and transmits the voltage signal of the distribution network to the band-pass filter. After the band-pass filter is processed, it is processed by the rectifier circuit to convert the AC signal into a DC signal and transmit it to the voltage comparator. Compare, and finally output to the trigger circuit for processing to ensure the reliable conduction of the thyristor V.

The power supply uses solar panels for energy absorption and energy storage, and then supplies power to power electronic devices (including monitoring equipment, band-pass filters, rectifier circuits, voltage comparators and trigger circuits) through boost circuits and voltage regulator circuits.

The monitoring equipment monitors the voltage signal of the distribution network, and inputs the monitored voltage signal to the band-pass filter for processing. The center frequency of the bandpass filter is 30Hz, the upper limit cutoff frequency is 40Hz, and the lower limit cutoff frequency is 20Hz. The fourth-order Chebyshev active bandpass filter is used to ensure the fast transition from the passband to the stopband. The bandpass filter is to filter out subsynchronous resonant signals in the frequency range of 20Hz to 40Hz.

The rectifier circuit converts the AC signal transmitted by the band-pass filter into a DC signal, and transmits it to the voltage comparator for comparison, so as to ensure the continuity and stability of the output signal of the voltage comparator.

The voltage comparator consists of two voltage input ports and one output port. One end of the input end is connected to the rectifier circuit to receive the DC voltage signal transmitted by it, and the other end is the comparison voltage. It should also be converted according to the transformation ratio relationship), which can not only avoid the interference of low-frequency signals in the power grid, but also accurately identify the subsynchronous resonance signal, and output a high-potential signal or a low-potential signal through the voltage comparator. When the transmitted DC voltage signal is greater than the comparison voltage , the voltage comparator outputs a high potential signal, otherwise it outputs a low potential signal, and the potential signal output by the voltage comparator is input to the trigger circuit of the thyristor group V.

The trigger circuit receives the potential signal from the voltage comparator, and when the trigger circuit receives the high potential signal, it outputs a pulse signal to the gate of the thyristor group V, which triggers the thyristor group V to conduct reliably. When the trigger circuit receives a low-level signal, it does not act.

Fig. 4 triggering circuit is the existing typical thyristor triggering circuit. It consists of two parts: the pulse amplification link composed of the triode Q1 and the triode Q2, and the pulse output link composed of the pulse transformer and the auxiliary circuit. When the triode Q1 and the triode Q2 are turned on, a trigger pulse is output between the gate and the cathode of the thyristor through the pulse transformer. The diode D1 and the resistor R3 are designed to release the energy stored by the pulse transformer when the transistor Q1 and the transistor Q2 change from on to off. The voltage of the voltage comparator is input from the gate of the transistor Q1, and the output port is the two ports of the resistor R4 and the anode of the diode D3 on the right as shown in the figure, and is connected to the cathode of the gate of the thyristor.

A distribution network series compensation method for suppressing subsynchronous resonance based on the above-mentioned capacitance compensation device, when subsynchronous resonance occurs in the distribution network system, a signal is transmitted to the gate of the thyristor group V, so that the thyristor group V is turned on, so that the The inductance coil L1 is connected to the circuit and is connected in parallel with the capacitor C to suppress the further development of the subsynchronous resonance; when the subsynchronous resonance disappears, a signal is transmitted to the gate of the thyristor group V, so that the group thyristor group V is turned off, and the inductance coil is cut off. L1, makes the series capacitor compensation device appear capacitive as a whole, and continues to play the role of compensating for the voltage drop of the distribution network line.

Further, the control branch transmits the signal to the gate of the thyristor group V, and the control branch includes monitoring equipment, band-pass filter, rectifier circuit, voltage comparator and trigger circuit. The voltage is transmitted to the band-pass filter, the band-pass filter filters out the voltage signal outside the set frequency, obtains the AC voltage signal within the set frequency range, and transmits the AC voltage signal within the set frequency range to the rectifier circuit, rectifying The circuit converts the received AC voltage signal within the set frequency range into a DC voltage signal, and the voltage comparator compares the DC voltage signal with the threshold, and outputs a high-potential signal or a low-potential signal to the trigger circuit. The high-potential signal or low-potential signal controls the thyristor group V to be turned on or off.

The invention proposes a series capacitance compensation device (hereinafter referred to as a series capacitance compensation device) of a distribution network that can suppress subsynchronous resonance. The series capacitance compensation device is composed of a compensation unit and a subsynchronous resonance suppression unit. The compensation unit is mainly composed of capacitors, damping circuits, voltage limiters and bypass circuit breakers to improve the voltage quality under continuous operating voltage. The subsynchronous resonance suppression unit is mainly composed of an inductance coil, a thyristor group and a control branch. The control branch is composed of a power supply, a band-pass filter, a rectifier circuit, a voltage comparator and a trigger circuit. Subsynchronous resonance occurs in the compensation unit and the power distribution system. The band-pass filter monitors the subsynchronous resonant frequency and voltage signal of the distribution network in real time. After filtering, the AC signal is converted into a DC signal by the rectifier circuit, which is transmitted to the voltage comparator for comparison, and then output to the trigger circuit for processing. , trigger the thyristor group to conduct reliably. The power supply provides working power for the subsynchronous resonance unit. The invention is mainly used for suppressing the sub-synchronous resonance problem caused by the asynchronous motor and the series capacitance compensation device in the power system distribution network.

The above content is only to illustrate the technical idea of the present invention, and cannot limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention all fall within the scope of the claims of the present invention. within the scope of protection.

Claims (9)

1. a kind of power distribution network compensator with series capaci tance that can inhibit subsynchronous resonance, which is characterized in that including compensating unit and Subsynchronous resonance inhibits unit, and the compensating unit includes capacitor C, and it includes concatenated electricity that the subsynchronous resonance, which inhibits unit, Feel coil L1 and thyristor groups V, the subsynchronous resonance inhibits unit in parallel with capacitor C.

2. a kind of power distribution network compensator with series capaci tance that can inhibit subsynchronous resonance according to claim 1, feature It is, the compensating unit further includes voltage limiter F, and the voltage limiter F is connected in parallel on the both ends capacitor C.

3. a kind of power distribution network compensator with series capaci tance that can inhibit subsynchronous resonance according to claim 1, feature It is, the compensating unit further includes inductance coil L2, damping resistance R and circuit breaker Q F2, the inductance coil L2 and damping Resistance R parallel connection constitutes damping circuit, and the damping circuit and circuit breaker Q F2 connect to form bypass branch, the bypass branch and Capacitor C is in parallel.

4. a kind of power distribution network compensator with series capaci tance that can inhibit subsynchronous resonance according to claim 1, feature It is, the capacitor C is also in parallel with bypass breaker QF1.

5. a kind of power distribution network compensator with series capaci tance that can inhibit subsynchronous resonance according to claim 1, feature It is, the thyristor groups V controls its on or off according to network voltage by controlling brancher.

6. a kind of power distribution network compensator with series capaci tance that can inhibit subsynchronous resonance according to claim 5, feature Be, the controlling brancher includes monitoring device, and the input terminal of the monitoring device is connected with power grid, the monitoring device it is defeated Outlet is connected with the input terminal of rectification circuit, and the output end of the rectification circuit is connected with the input terminal of voltage comparator, described The output end of voltage comparator is connected with the input terminal of trigger circuit, and the output end of the trigger circuit is connected with thyristor groups V； The monitoring device is used to monitor the voltage signal of power grid, and network voltage is transferred to rectification circuit, and the rectification circuit is used In the ac voltage signal received is converted to d. c. voltage signal, the voltage comparator is used for d. c. voltage signal It is compared with threshold value, and exports high potential signal or low-potential signal to trigger circuit, trigger circuit is used for basis and receives High potential signal or low-potential signal control thyristor groups V on or off.

7. a kind of power distribution network compensator with series capaci tance that can inhibit subsynchronous resonance according to claim 6, feature It is, bandpass filter, the bandpass filtering is provided between the output end of the monitoring device and the input terminal of rectification circuit Device is used to filter out the voltage signal outside setpoint frequency, obtains the ac voltage signal within the scope of setpoint frequency.

8. a kind of power distribution network series compensation side of the inhibition subsynchronous resonance based on Electric capacity compensation device described in claim 1 Method, which is characterized in that when subsynchronous resonance occurs for distribution network system, deliver a signal to the gate pole of thyristor groups V, make thyristor Group V conducting, and then keep inductance coil L1 in parallel with capacitor C, inhibit the development of subsynchronous resonance；When subsynchronous resonance disappears it Afterwards, the gate pole for delivering a signal to thyristor groups V makes group thyristor groups V in off state, cuts off inductance coil L1, make series electrical Hold compensation device and capacitive is integrally presented, continues to play a part of to compensate distribution network line voltage landing.

9. the power distribution network series compensation method according to claim 8 for inhibiting subsynchronous resonance, which is characterized in that pass through control For branch transmitting signal processed to the gate pole of thyristor groups V, controlling brancher includes monitoring device, bandpass filter, rectification circuit, voltage Comparator and trigger circuit, the voltage signal of the monitoring device monitoring power grid, and network voltage is transferred to bandpass filter, The bandpass filter filters out the voltage signal outside setpoint frequency, obtains the ac voltage signal within the scope of setpoint frequency, and will Ac voltage signal within the scope of setpoint frequency is transferred to rectification circuit, the setpoint frequency range that the rectification circuit will receive Interior ac voltage signal is converted to d. c. voltage signal, and the voltage comparator compares d. c. voltage signal and threshold value Compared with and exporting high potential signal or low-potential signal to trigger circuit, trigger circuit is according to the high potential signal that receives or low Electric potential signal controls thyristor groups V on or off.