CN110690714A - A reactive power compensation device - Google Patents

Abstract

The invention provides a reactive power compensation device. The reactive power compensation device is a three-phase circuit, which is respectively connected with the three-phase busbar of a power distribution network; each phase circuit of the reactive power compensation device includes a high-pass filter resistor and a sequential Filter capacitors, series reactors and compensation capacitors connected in series; the filter capacitors of each phase circuit of the reactive power compensation device are respectively connected in series with the three-phase bus of the distribution network, and the compensation capacitors of each phase circuit of the reactive power compensation device are in The end of the branch where it is located is connected in a star shape; one end of the high-pass filter resistor of each phase circuit of the reactive power compensation device is respectively connected in series between the series reactor and the filter capacitor on the phase circuit, and the other end is shared at the end of the branch where it is located. star connection. Compared with the prior art, the reactive power compensation device provided by the present invention can form a C-type heterogeneous high-pass filter, filter out various high-frequency harmonics, and is less prone to overload damage.

Description

A reactive power compensation device

technical field

The invention relates to the field of electricity safety of a distribution network, in particular to a reactive power compensation device of a distribution network.

Background technique

The existing distribution network consists of a power station, a substation and a user terminal, among which, the power station, the substation and the user terminal are all connected by busbars for power transmission. In the process of power transmission, in order to improve the power factor of the distribution network, reduce the energy loss in the power transmission process, and ensure the energy transmission efficiency of the distribution network, reactive power compensation devices are usually connected to the distribution network. At the same time, in the existing distribution network, the nonlinear load connected to the distribution network leads to the generation of harmonics in the distribution network, and the existence of harmonics can easily lead to damage to the power equipment in the distribution network, such as capacitor overload damage or partial reactance. Faults such as overvoltage damage will also lead to the shutdown of the distribution network in severe cases, which will directly interfere with the normal operation of each power supply or power consumption system, resulting in huge economic losses. Therefore, the ideal reactive power compensation device should also have a good function of filtering out the harmonics of the distribution network.

Please refer to FIG. 1 , which is a schematic circuit diagram of a conventional reactive power compensation device. The existing reactive power compensation device 10 is a three-phase circuit, and the three-phase circuits are respectively connected to the bus bars of the power distribution network. Wherein, each phase circuit of the reactive power compensation device 10 includes a series-connected switching element KM, a current transformer 1TA, a series reactor L, a fuse FU, a capacitor C, and a parallel connection between the fuse FU and the capacitor C. Discharge coil TV at both ends. The three-phase circuits of the existing reactive power compensation device 10 are respectively connected to the three-phase busbar circuits through the switching elements KM. The existing reactive power compensation device 10 further includes three busbar arresters F1 respectively connected in its three-phase circuits, and one end of each busbar arrester F1 is connected to the current mutual inductance on each phase circuit of the existing reactive power compensation device 10 Between the reactor 1TA and the series reactor L, the other end is grounded.

In the reactive power compensation device, the series reactor L cooperates with the capacitor C to form a single-tuned filter, which can filter out harmonics and provide reactive power compensation to the distribution network at the same time.

During operation, the busbar current flows into the reactive power compensation device from the switching element. The series reactor L cooperates with the capacitor C to filter out the harmonics in the distribution network. The peak value of the voltage, once the voltage peak value of a certain phase circuit exceeds the conduction threshold of the arrester, the arrester will conduct grounding and discharge the voltage. When the capacitor is disconnected from the circuit, the charge in the capacitor will be discharged through the discharge coil.

However, in the face of the trend of automation and intelligence of loads connected to the distribution network, the harmonic spectrum injected into the distribution network is complex and changeable. The above-mentioned existing reactive power compensation devices have the following defects: First, the existing reactive power The tuning filter composed of the series reactor L and the capacitor C in the compensation device can only filter out the specific one or two adjacent harmonics in the distribution network, and the filtering ability is limited and the ability to absorb high-frequency harmonics is weak; Second, in the face of harmonics in the distribution network with complex spectrum, the existing reactive power compensation device itself has a greater risk of harmonic overload damage. The above-mentioned defects make the existing reactive power compensation device unable to meet the needs of users and are largely idle.

SUMMARY OF THE INVENTION

The invention provides a reactive power compensation device. The reactive power compensation device is a three-phase circuit, which is respectively connected with the three-phase busbar of a power distribution network; each phase circuit of the reactive power compensation device includes a high-pass filter resistor and a sequential Filter capacitors, series reactors and compensation capacitors connected in series; the filter capacitors of each phase circuit of the reactive power compensation device are respectively connected in series with the three-phase bus of the distribution network, and the compensation capacitors of each phase circuit of the reactive power compensation device are in The end of the branch where it is located is connected in a star shape; one end of the high-pass filter resistor of each phase circuit of the reactive power compensation device is respectively connected in series between the series reactor and the filter capacitor on the phase circuit, and the other end is shared at the end of the branch where it is located. star connection.

Compared with the prior art, the filter capacitor, the compensation capacitor, the filter resistor and the series reactor in the reactive power compensation device provided by the present invention can form a C-type heterogeneous high-pass filter, which can filter out various high-frequency harmonics. Not sensitive to harmonics, not easy to be damaged by overload. The reactive power compensation circuit of each phase can also provide a harmonic overvoltage discharge channel through the grounding resistance, so as to prevent the harmonic overvoltage from harming various power equipment. At the same time, harmonic signals can also be drawn from the star-connected filter resistors for subsequent circuits to perform harmonic analysis.

Further, the reactive power compensation device also includes a grounding resistor, one end of the high-pass filter resistor in each phase circuit of the reactive power compensation device is respectively connected in series between the series reactor and the filter capacitor on the phase circuit, and the other end is connected in series with the filter capacitor. The ends of the branch where it is located are connected to the star through the grounding resistance.

Further, the reactive power compensation device also includes a fuse and a discharge coil, and the three primary coil input ends of the discharge coil are respectively connected between the busbar and the filter capacitor in each phase circuit of the reactive power compensation device through the fuse, so The secondary coil of the discharge coil is respectively connected between the filter capacitor and the arrester on the three-phase circuit of the reactive power compensation device, and the secondary coil of the discharge coil is also connected to the star connection point of each high-pass filter resistor. The discharge coil can discharge the residual charge in the filter capacitor to ensure the safety of electricity consumption.

其中U为所述输电线线电压，I_L为串联电抗器的额定电流。依照本方案设置的滤波电容能够限制流过其的基波电流，降低所述无功补偿装置中元件的发热现象，避免各元件由于热量过高而炸裂损坏。Further, the capacitive reactance of the filter capacitor

Wherein U is the line voltage of the transmission line, and _IL is the rated current of the series reactor. The filter capacitor set according to this solution can limit the fundamental wave current flowing therethrough, reduce the heating phenomenon of the elements in the reactive power compensation device, and prevent the elements from being burst and damaged due to excessive heat.

Further, the reactance value of the compensation capacitor is equal to the reactance value of the series reactor. According to the arrangement of this solution, the fundamental wave current and harmonic current of the filter capacitor can be shunted, thereby reducing the fundamental wave loss and heat generation of the reactive power compensation device of the present invention.

Further, the harmonic loss energy recovery unit includes a rectifier, and the three input ends of the rectifier are respectively connected in series between the filter capacitor and the series reactor in the three-phase circuit of the reactive power compensation device. At the same time, the three rectifiers are connected in series. The input ends are also respectively connected with filter resistors in the three-phase circuit of the reactive power compensation device. The rectifier is not easily disturbed by harmonics, and can stably convert harmonic loss energy into DC power.

Further, the harmonic loss energy recovery unit also includes a controller, a shunt and a voltage regulator silicon chain connected in series to the positive output end of the rectifier; the controller is respectively connected with the shunt and the voltage regulator. A silicon chain is connected, and the controller receives the shunt input signal and outputs an electrical signal to the voltage regulating silicon chain. The controller can control the access length of the voltage regulating silicon chain and the voltage at both ends thereof according to the current detected by the shunt, and adjust the output voltage value of the harmonic loss energy recovery unit.

Further, the harmonic loss energy recovery unit further includes two fuses, and the fuses are respectively connected in series with the positive output terminal and the negative output terminal of the rectifier.

Further, the reactive power compensation device further includes a zero-sequence current transformer, and the zero-sequence current transformer is connected in series between the filter capacitor and the series reactor in the three-phase circuit of the reactive power compensation device. The zero-sequence current transformer can detect the zero-sequence current in the reactive power compensation device and output it to the subsequent analysis circuit, so as to realize fault monitoring of each phase circuit of the reactive power compensation device.

Description of drawings

1 is a schematic circuit diagram of an existing reactive power compensation device;

Fig. 2 is a circuit diagram of connecting the reactive power compensation device of Embodiment 1 of the present invention to the busbar of the distribution network;

3 is a schematic structural diagram of the impedance of positive and negative sequence components of harmonics when the distribution network is connected to the reactive power compensation device in Embodiment 1 of the present invention;

4 is a schematic structural diagram of the harmonic zero-sequence component impedance when the distribution network is connected to the reactive power compensation device in Embodiment 1 of the present invention;

5 is a schematic diagram of the impedance structure of harmonic positive and negative sequence components when the distribution network is connected to the existing reactive power compensation device in Embodiment 1 of the present invention;

6 is a schematic diagram of the harmonic zero-sequence component impedance structure when the distribution network is connected to the existing reactive power compensation device in Embodiment 1 of the present invention;

7 is a graph of harmonic positive and negative sequence impedance curves when the distribution network is connected to an existing reactive power compensation device in Embodiment 1 of the present invention;

8 is a positive and negative sequence impedance curve diagram of a set of reactive power compensation devices connected to the distribution network in Embodiment 1 of the present invention;

9 is a graph of positive and negative sequence impedance curves of five sets of reactive power compensation devices connected to the distribution network in Embodiment 1 of the present invention;

FIG. 10 is a comparison diagram of harmonic positive and negative sequence impedance curves connected to the existing reactive power compensation device and connected to 1-5 sets of reactive power compensation devices in the distribution network in Embodiment 1 of the present invention;

11 is a comparison diagram of the harmonic zero-sequence impedance curves of the existing reactive power compensation device connected to the existing reactive power compensation device and the access to 1-5 sets of reactive power compensation devices in the distribution network in Embodiment 1 of the present invention;

12 is a schematic circuit diagram of a reactive power compensation device in Embodiment 2 of the present invention;

FIG. 13 is a circuit schematic diagram of a harmonic loss energy recovery unit in Embodiment 2 of the present invention.

Detailed ways

The present invention aims to provide a reactive power compensation device, which can construct various filters through internal components to achieve full-pass band filtering of harmonics, and the device itself is not sensitive to harmonics and is not easily damaged by the influence of harmonics. Further, the present invention obtains the structure of the reactive power compensation device that effectively protects harmonic overcurrent by studying the scheme of setting reactance parameters to shunt the harmonic current. Structure of reactive power compensation device to protect various harmonic overvoltages.

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

Example 1

Please refer to FIG. 2 , the reactive power compensation device 20 of this embodiment is a three-phase circuit. In each phase circuit, one side of the static contact of the isolating switch QS is respectively connected to one-phase circuit of the bus bar, and one side of the moving contact of the isolating switch QS is connected in sequence. The current transformers 1TA, 2TA, the filter capacitor _CH , the series reactor L ₁ and the compensation capacitor C ₁ are connected in series, and the compensation capacitor C ₁ of each phase circuit is connected in a common star shape at the end of the branch. The current transformers 1TA and 2TA both include a primary coil and a secondary coil, the primary coil of the current transformer is connected in series between the phase circuit isolation switch QS and the filter capacitor _CH , and the secondary coil of the current transformer induces The current of the primary coil and the output signal can be used to measure the current signal current or provide the current protection signal.

The reactive power compensation device 20 also includes a zero-sequence current transformer L _H , a grounding resistance _RE2 and a discharge coil TV, and each phase circuit of the reactive power compensation device 20 includes a high-pass filter resistor _RH and a fuse. device FU. The zero-sequence current transformer L _H is connected in series between the filter capacitor _CH and the series reactor L ₁ on the three-phase circuit of the reactive power compensation device 20; the high-pass filtering of each phase circuit of the reactive power compensation device 20 One end of the resistor _RH is respectively connected in series between the zero-sequence current transformer L _H and the filter capacitor _CH on the phase circuit, and the other end is connected to the end of the branch where it is in a common star connection and is grounded through the grounding resistor _RE2 . The three terminals a, b and c of the primary coil of the discharge coil TV are respectively connected between the current transformers 1TA, 2TA and the filter capacitor _CH on the three-phase circuit of the reactive power compensation device 20 through the fuse FU. The secondary coil of the discharge coil TV is respectively connected between the filter capacitor _CH and the arrester F2 on the three-phase circuit of the reactive power compensation device 20 through the ka, kb and kc terminals, and the secondary coil also passes the voltage V _S0 The output end is connected to the star connection point of the high-pass filter resistor _RH . The discharge coil TV can discharge the residual charge in the filter capacitor _CH .

The reactive power compensation device 20 also includes a surge arrester group, and the surge arrester group includes a three-phase circuit between the current transformers 1TA, 2TA and the filter capacitor _CH on the three-phase circuit of the reactive power compensation device 20, respectively. Each phase circuit of the arrester group is connected in series with an arrester F2 with the same on-voltage value, and the ends of the arresters F2 of the three-phase circuits of the arrester group are connected in a star shape and then grounded. When a certain phase circuit of the reactive power compensation device is struck by lightning, the arrester F2 on the phase circuit will conduct grounding, discharge overvoltage, and prevent overvoltage from causing damage to other power equipment on the circuit.

The reactive power compensation device 20 also includes a first electrified display group and a second electrified display group, each group of electrified display groups includes a three-phase circuit, and each phase circuit has the same structure, including a series-connected capacitor and an electrified display, The capacitance of each phase circuit is connected to the ground at the end of the branch where it belongs. The first display group includes three identical charged displays SQ1, and the capacitance of each phase circuit is respectively connected between the isolation switch QS and the current transformers 1TA and 2TA in the three-phase circuit. The second display group includes three identical charged displays SQ2, and the capacitance of each phase circuit is respectively connected between the current transformers 1TA, 2TA and the filter capacitor _CH in the three-phase circuit. The electrification indicator lights up when there is a voltage, providing the engineer with a high-voltage electrification indication.

When the distribution network works _normally , the _capacitors and _reactors in the reactive power compensation device perform reactive power compensation on the distribution network. L ₁ , compensation capacitor C ₁ and discharge coil TV form various filters to filter the harmonics of the distribution network.

When lightning overvoltage occurs on the busbar, the impulse current flowing through the three-phase circuit of the reactive power compensation device will flow to the arrester F2, and the arrester F2 will reach the on-voltage and discharge the overvoltage.

The working principle of the reactive power compensation device 20 of this embodiment is described below:

(1) Principle of protection arrester:

1) The principle of protecting the arrester F2:

其中Z_n为系统n次谐波阻抗，Z_H为加装所述无功补偿装置后配电网母线上加装点谐波阻抗，I_n为n次谐波电流。通过限制谐波电压峰值，能够减少避雷器F2导通次数，避免避雷器F2短时间内反复导通进而发生热量上升而炸裂，造成相间电路短路。The filter circuit formed by the circuit elements of the reactive power compensation device limits the amplitude of the n-th harmonic voltage that may appear in the busbar of the distribution network, thereby realizing the protection of the arrester. Specifically, the reactive power compensation device limits the nth harmonic voltage of the bus to a value of

Wherein Z _n is the nth harmonic impedance of the system, Z _H is the added point harmonic impedance on the distribution network bus after the reactive power compensation device is installed, and I _n is the nth harmonic current. By limiting the peak value of the harmonic voltage, the conduction times of the arrester F2 can be reduced, and the arrester F2 can be prevented from being repeatedly turned on in a short period of time, thereby causing heat rise and bursting, resulting in short circuit between phases.

(2) Principle of reactive power compensation:

In the reactive power compensation device, the filter capacitor _CH , the series reactor L ₁ and the compensation capacitor C ₁ cooperate with each other to perform reactive power compensation on the power distribution network.

(3) Filtering principle:

The reactive power compensation device filter capacitor _CH , filter resistance _RH , grounding resistance _RE2 , series reactor L1 and compensation capacitor _C1 cooperate with each other to form _a variety of filters, so that the reactive power compensation device can The passband harmonics are filtered to eliminate harmonics. Wherein, the structure of the three-phase symmetrical loop of the reactive power compensation device (filter capacitor _CH , filter resistor _RH , grounding resistor _RE2 , series reactor L1 and compensation capacitor _{C1 )} constitutes a C-type high-pass filter; The ground loop in each phase circuit of the reactive power compensation device constitutes a second-order high-pass filter; the zero-sequence current loop (filter capacitor _CH , filter resistance _RH , grounding resistance _RE2 and discharge coil TV) and the external distribution network system A low-pass filter is formed when the ground impedance of the neutral point ground loop is matched.

The positive and negative sequence impedance parts of the equivalent harmonic impedance structure of the distribution network are shown in Figure 3 and Figure 4, which are the harmonic impedances of the positive and negative sequence components of the 10kV system when 1-5 sets of the reactive power compensation devices are connected to the distribution network. Structural schematic diagram and zero-sequence component harmonic impedance structural diagram.

As can be seen from Figure 3, the impedance formula of positive and negative sequence components of harmonics in the distribution network after installing one set of the reactive power compensation device in the distribution network is changed to:

Z ¹ _n =(1/Z _sn +1/Z _fzn +1/Z _cen +1/Z _Hn ) ^-1

After installing two sets of the reactive power compensation devices in the distribution network, the impedance formula of the positive and negative sequence components of the distribution network harmonics is as follows:

Z ² _n =(1/Z _sn +1/Z _fzn +1/Z _cen +1/Z _Hn +1/Z _Hn ) ^-1

After installing n sets of the reactive power compensation devices in the distribution network, the impedance formula of the positive and negative sequence components of the distribution network harmonics is as follows:

为加装1-5套所述无功补偿装置后加装点n次谐波阻抗，

为系统n次谐波阻抗。Among them, in Figure 3, X _S is the main transformer short-circuit reactance, X _ZB is the impedance of the grounding transformer, X _F1 is the equivalent impedance of the generator, C _e is the phase-to-phase capacitance of the line, X _fz is the load impedance, and I _n is the nth harmonic current. , _CH is the filter capacitor, L ₁ is the fundamental wave branch current, C ₁ is the fundamental wave branch compensation capacitor, TV is the discharge coil,

In order to add point n-th harmonic impedance after installing 1-5 sets of the reactive power compensation device,

is the nth harmonic impedance of the system.

As can be seen from Figure 4, the impedance formula of the harmonic zero-sequence component of the ground loop of the distribution network when one set of the reactive power compensation device is installed:

When two sets of reactive power compensation devices are installed, the impedance formula of the harmonic zero-sequence component of the system grounding circuit is as follows:

When n sets of reactive power compensation devices are installed, the impedance formula of the harmonic zero-sequence component of the system grounding circuit is as follows:

为接地变压器零序电抗、C_e1-C_e3为线路对地电容、I_n0为n次谐波电流零序分量、

为消弧线圈零序电抗、R_H为高通滤波电阻、U_Y0为R_H星型连接点位移电压、R_E2为对支路限流的接地电阻。Among them, R _E1 in Figure 4 is the neutral point grounding resistance,

is the zero-sequence reactance of the grounding transformer, C _e1 -C _e3 is the line-to-ground capacitance, I _n0 is the zero-sequence component of the n-th harmonic current,

is the zero-sequence reactance of the arc suppression coil, R _H is the high-pass filter resistance, U _Y0 is the displacement voltage of the R _H star connection point, and R _E2 is the grounding resistance to limit the current of the branch.

In order to compare with the impedance structure of the prior art, please refer to FIG. 5 and FIG. 6 at the same time, which are respectively a schematic diagram of the harmonic impedance structure of the positive and negative sequence components of the 10kV system when the reactive power compensation device of the prior art is connected to the distribution network and the zero sequence Schematic diagram of the component harmonic impedance structure.

It can be seen from Fig. 5 that the impedance formula of harmonic positive and negative sequence components when the reactive power compensation device of the prior art is connected to the distribution network:

In Figure 5, X _S is the main transformer short-circuit reactance, X _ZB is the impedance of the grounding transformer, X _F1 is the equivalent impedance of the generator, C _e is the line interphase capacitance, X _fz is the load impedance, and I _n is the n-th harmonic current.

It can be obtained from Fig. 6 that the prior art reactive power compensation device is connected to the distribution network, and the harmonic zero-sequence impedance formula of the distribution network when the neutral point resistance is grounded (neglecting transformer leakage reactance Z _BL ):

为接地变压器零序电抗、C_e1-C_e3为线路对地电容、I_n0为n次谐波电流零序分量。In Figure 6, R _E1 is the neutral point grounding resistance,

is the zero-sequence reactance of the grounding transformer, C _e1 -C _e3 is the line-to-ground capacitance, and I _n0 is the zero-sequence component of the n-th harmonic current.

Comparing the prior art with the harmonic impedance formula of the reactive power compensation device, it can be known that, compared with the existing reactive power compensation device, the harmonic impedance of the power distribution network of the present invention is smaller in fundamental wave impedance and generates smaller overvoltage.

Please refer to Fig. 7-10 at the same time. In order to illustrate the impedance situation of the reactive power compensation device at each harmonic order after setting the circuit according to the above formula, and to compare with the prior art, Fig. 7-10 shows the power distribution network. Positive and negative sequence impedance curves when the existing reactive power compensation device is installed in the power distribution network and when 1 to 5 sets of the reactive power compensation device are respectively installed in the distribution network. In Figure 7-10, the horizontal axis represents the harmonic order, and the vertical axis represents the positive and negative sequence components of the harmonic impedance of the distribution network. Points A and E in each figure have the same meaning, and points A and E represent in turn When the prior art reactive power compensation device and 1-5 sets of arrester protection devices in this embodiment are respectively connected to the distribution network, the impedance peak points of the positive and negative sequence impedance components of the harmonics of the distribution network.

For the positive and negative sequence impedance of the distribution network, when the reactive power compensation device of the prior art is connected to the distribution network, the positive and negative sequence impedance curves of the distribution network are steep and the impedance peak value reaches about 1074Ω, while a set of the reactive power compensation device When connected to the distribution network, the impedance curve of the positive and negative sequence components of the harmonics of the distribution network is relatively flat, and the impedance peak value drops significantly to 185Ω. Further, when 2-5 sets of the reactive power compensation devices are installed in the distribution network, the positive and negative sequence curves of the distribution network are smoother, and the impedance peak value is further reduced. Since the positive and negative sequence impedance values under the harmonic order are proportional to the overvoltage of the corresponding harmonic order, the above phenomenon proves that, compared with the existing reactive power compensation device, the reactive power compensation device can compensate for each frequency under the full passband. The harmonic overvoltage has a better suppression effect, and increasing the number of the reactive power compensation devices connected to the distribution network can enhance the suppression effect on the harmonic overvoltage.

For the same reason, please refer to FIG. 11 again. FIG. 11 is a comparison diagram of the harmonic zero-sequence impedance curves of the existing reactive power compensation device connected to the existing reactive power compensation device and the connection of 1-5 sets of arrester protection devices in the distribution network according to Embodiment 4 of the present invention. Among them, the horizontal axis represents the harmonic order, the vertical axis represents the zero-sequence component of the harmonic impedance of the distribution network, and the vertical axis value of the point R-W is the existing reactive power compensation device and 1-5 sets of arrester protection devices of this embodiment, respectively. The zero-sequence component impedance value of the harmonic impedance of the distribution network when it is connected to the distribution network. Compared with the distribution network connected to the prior art reactive power compensation device, after adding one set of the reactive power compensation device to the distribution network, the peak value of the impedance curve of the harmonic zero-sequence component of the distribution network is also relatively reduced. And as the number of the reactive power compensation devices installed increases, the peak value of the impedance curve of the distribution network decreases. The above phenomenon proves that compared with the existing reactive power compensation device, the reactive power compensation device can have a good suppression effect on the zero-sequence overvoltage, and increasing the number of the reactive power compensation devices connected to the distribution network can enhance the resistance to zero-sequence overvoltage. Restraining effect of zero sequence overvoltage

To sum up, after the reactive power compensation device is connected to the distribution network, it can effectively reduce the harmonic positive and negative sequence component impedance and zero-sequence component impedance of the distribution network, and increase the reactive power compensation connected to the distribution network. The number of devices can better suppress the harmonic overvoltage of the distribution network, which will prevent the distribution network from having significant resonance overvoltage frequency points, thereby eliminating the possibility of harmonic overvoltage in the distribution network and avoiding harmonics. Overvoltages endanger electrical equipment in the distribution network.

(4) The principle of providing multiple relief channels for overvoltages of different amplitudes in the distribution network:

As shown in Figure 2, the filter capacitor _CH , the filter resistor _RH and the grounding resistor R _E2 form the main zero-sequence channel, which discharges higher-frequency harmonic overvoltages; the discharge coil TV and the grounding resistor R _E2 form an auxiliary zero-sequence channel channel to discharge low-frequency harmonic overvoltage; arrester F2 constitutes a discharge channel for impulse overvoltage (lightning).

(5) The principle of shunting the fundamental current, harmonic current and impulse current in the distribution network:

As shown in FIG. 2 , if the series reactor reactance and the compensation capacitive reactance of the arrester protection device are set to satisfy X _L1 =X _C1 , the fundamental wave impedance of the fundamental wave current branch formed by the series reactor L ₁ and the compensation capacitor C ₁ is zero , at this time, the current flowing through the filter capacitor _CH (including the fundamental current, harmonic current and impulse current) realizes shunting:

In the harmonic current, the positive and negative sequence components of the high-frequency harmonic current are mainly absorbed by the filter resistor _RH , and the zero-sequence components are absorbed by the filter resistor _RH and the grounding resistance _RE2 ; The current is shunted to the discharge coil TV, the grounding resistance R _E2 and the neutral grounding loop of the external distribution network system; in the fundamental wave current, the fundamental wave balance current is shunted to the series reactor L ₁ and the compensation capacitor C ₁ to form the fundamental wave balance Current loop; the fundamental wave unbalanced current, the single-phase grounding capacitor current of the system and the harmonic zero-sequence component current are shunted by the above zero-sequence channel and discharged through the grounding resistance R _E2 ; the impulse current is shunted to the surge current (lightning) formed by the arrester F2. release channel.

The above-mentioned shunt method can greatly reduce the fundamental wave loss and heat generation of the device and the waveform distortion caused by the discharge of the arrester.

(6) Other parameter settings:

The rated working voltage of the filter capacitor _CH must be selected with reference to the line voltage U of the power distribution network transmission line. The fundamental wave compensation current I _CH of the filter capacitor _CH should not be greater than the rated current _IL of the reactor, that is, I _CH ≤ _IL .

At this time, each compatible resistance

In the existing distribution network, the trend of load automation and intelligence leads to a decrease in traditional reactive power demand, severe voltage fluctuations at the end of the line, and complex and changeable harmonic spectrum injected into the distribution network. The above factors can easily lead to the generation of equipment in the distribution network. (such as lightning arresters) damage, overheating of lines and malfunction of automatic protection devices. Due to the inability to solve the above problems well, a large number of reactive power compensation devices in the existing distribution network are idle. The reactive power compensation device in the reactive power compensation circuit of this embodiment can solve the above problems, and the various filters formed by the components in the circuit can perform all-pass-band filtering and harmonic elimination on the distribution network, and can eliminate the harmonics of high-frequency subharmonics. It has strong wave absorption ability, can effectively avoid the harm of harmonics in the distribution network to various power equipment, realizes effective filtering of harmonics, and has low equipment cost. Therefore, the reactive power compensation circuit of this embodiment can meet the practical application of the distribution network. to improve the current situation of a large number of idle reactive power compensation devices in the existing distribution network.

In addition, since the existing distribution network is connected to a variety of reactive power compensation devices, their mutual influence will cause the problem of over-compensation of reactive power compensation in the distribution network or unreasonable amplification of the harmonics of the distribution network. The further purpose of this embodiment is to change the above-mentioned form of connecting various reactive power compensation devices to the existing distribution network. The multiple reactive power compensation devices of this embodiment are respectively connected to the circuits at all levels of the power distribution network, such as power stations, substations, and user terminals, and the reactive power compensation devices of this embodiment can be connected in a targeted manner. Positions where reactive power compensation is required in all levels of circuits in the distribution network to ensure that the effect of balanced reactive power parameters provided by each reactive power compensation device connected to the distribution network is controllable, so as to achieve reasonable and targeted provision for the distribution network. reactive power compensation. At the same time, in this embodiment, the arrester group with the reactive power compensation function and the reactive power compensation device are integrated into one reactive power compensation device, and each standardized reactive power compensation circuit connected to the distribution network has both The functions of protecting arresters, filtering harmonic elimination and reactive power compensation.

In a variant of this embodiment, the high-pass filter resistor R _H and the grounding resistor R _E2 in each phase circuit of the reactive power compensation device are respectively provided with voltage divider taps, which can lead to good high-frequency characteristics from the tap branch. The follow-up measurement circuit after the harmonic voltage signal sources Un _~ and V _~ is convenient for high-precision measurement of harmonic frequencies.

In yet another variant of this embodiment, the three-phase circuit branches of the reactive power compensation device are respectively connected in a star shape after the filter capacitor _CH and the arrester F2 are connected in series, and are connected with the grounding resistance R at the star connection point. _E1 connection. This modification simplifies the structure in which the high-pass filter resistors R _H in the three-phase circuit of the original reactive power compensation device are connected in a star shape and then grounded through the grounding resistor R _E2 , and the number of resistors is reduced to reduce the cost of setting up the reactive power compensation circuit. cost.

Example 2

The reactive power compensation device further includes a harmonic loss energy recovery unit 30 on the basis of Embodiment 1, and the input ends of the harmonic loss energy recovery unit 30 are respectively connected to the harmonics in the three-phase circuit of the reactive power compensation device. The branch through which the current flows.

With respect to the circuit structure in Embodiment 1, please refer to FIG. 12 , the circuit structure of the reactive power compensation device 21 adopted in this Embodiment 2 is basically the same as the circuit structure of the reactive power compensation device 20 in the previous Embodiment 1, the difference is It lies in the star connection of each filter resistor R _H , and the grounding resistor R _E2 is no longer connected and grounded. The three input ends of the harmonic loss energy recovery unit 30 are respectively connected between the filter capacitor _CH and the filter resistor _RH in each phase circuit, and receive the harmonic signal transmitted from the filter capacitor _CH .

Referring to FIG. 13 , the harmonic loss energy recovery unit 30 includes a rectifier U1-, a power dissipation resistor R _o1 , an overvoltage protector F ₃ , a DC voltmeter V, a shunt _FL , a voltage regulating silicon chain GL, and a reverse check. Diode DL, fuses _{R u1} , R _u2 , controller and parallel switch K _o1 . The three-phase input terminals of the rectifier U1 are respectively connected in series between the filter capacitors _CH and the filter resistors _RH in each phase circuit, and are simultaneously connected to the filter capacitors _RH of each phase circuit by means of taps. The fuses R _u1 and R _u2 are respectively connected in series with the output terminals on both sides of the rectifier U1- to receive the DC signal output by the rectifier, and then the fuse R _u1 outputs the DC power flowing through to the DC power supply of the DC common bus. The negative pole M-, the fuse R _u2 outputs the DC power flowing through it to the positive pole M+ of the DC common bus. The energy dissipation resistor R _o1 is connected in series with the parallel switch K _o1 and then connected in parallel between the fuses R _u1 and R _u2 . The shunt _FL , the voltage regulating silicon chain GL and the non-reverse diode DL are connected in series between the fuse R _u2 and the positive electrode _M + of the common DC bus. Wherein, the rectifier is a three-phase full-wave rectifier bridge, and a high-voltage silicon stack can be selected to form the bridge. The rectifier's ability to absorb system harmonics is not easily disturbed, and the reliability is high. The non-reverse diode D prevents reverse power supply from other DC sources, and is used to ensure isolation and non-reverse in the case of parallel operation of multiple harmonic loss energy recovery units 30 .

The controller is respectively connected with the switch K _o1 , the shunt _FL and the voltage regulator silicon chain GL, receives the detection signal output by the shunt _FL and controls the length of the silicon link in the voltage regulator silicon chain GL and the parallel switch The opening and closing of K _o1 realizes the adjustment of the voltage of the DC power supply and ensures that the DC power supply voltage does not exceed the threshold value. The common PLC controller in the power system can be used as the controller in this embodiment to realize the above functions. Preferably, the controller can be a controller with serial port, network port or optical port communication, which is convenient to receive external control signals Realize integrated control after the street is connected to the distribution network.

The DC voltmeter V and the overvoltage protector F3 are respectively connected in parallel between the fuses _{R u1} and R _u2 , wherein the DC voltmeter V can detect the voltage value of the DC power supply output by the rectifier, and the overvoltage protector can be connected to the DC power supply. The voltage limit protects the harmonic loss energy recovery unit when the voltage exceeds the limit peak value.

During operation, the harmonic currents flowing through the three-phase circuit of the reactive power compensation device respectively flow into the rectifier _U1- from each filter capacitor _CH to be rectified and converted into a DC power supply. The negative output signal of the DC power supply is input to the negative pole of the common DC bus after the fuse R _u1 , and the electrical signal output by the positive pole of the DC power supply sequentially flows through the fuse R _u2 , the shunt _FL , and the voltage regulating silicon The positive pole of the common DC bus is input after the chain GL and the non-return diode _DL . At the same time, the shunt _FL detects the current flowing through, and outputs a detection signal to the controller. The controller adjusts the length of the silicon link in the voltage regulator silicon link GL and the parallel switch according to the input signal of the shunt _FL . The opening and closing of K _o1 realizes the adjustment of the voltage of the DC power supply and ensures that the DC power supply voltage does not exceed the threshold value.

Among them, assuming that the high-frequency characteristics of the rectifier silicon stack meet all harmonic rectifier output requirements, then:

After n-th harmonic rectification, the output DC voltage U _dn =1.35U _n~ , where U _n~ is the harmonic voltage at the filter capacitor _RH on each phase circuit, and n is the harmonic order.

Output DC voltage after rectification of all harmonics

output DC current (A), where I _RHn is the n-th harmonic current flowing through the filter capacitor _RH .

According to different output voltage values obtained after adjustment by the control unit, the DC power output from the harmonic loss energy recovery unit can be supplied to different power equipments. When the output voltage value is low, the DC power supply can be supplied to the low-voltage lighting circuit; when the output voltage is the national standard DC power supply voltage of 220V, it can be used as a general DC power supply to supply corresponding general electrical equipment or as a Emergency power UPS. In addition, the existing inverter technology can also be used to convert the DC power supply into 380V standard AC power, and then input it into the power distribution network again, so that the harmonic loss energy can be fed back to the power grid.

Compared with the existing reactive power compensation device, the reactive power compensation device realizes all-pass band filtering of the three-phase circuit harmonics through the combination of the filter capacitor _CH , the filter resistor _RH , the grounding resistance _RE2 and the neutral point grounding device. Waves, eliminating resonance can reduce the influence of harmonics and their wildly fluctuating voltages in the distribution network. Further, the harmonic loss energy recovery unit realizes the transfer and recovery of the harmonic loss energy in the distribution network. Further, the grounding resistance R _E2 realizes the resonance suppression of the ground loop. When the arc suppression coil is out of control, the damping arc suppression coil inductance resonates with the line-to-ground capacitance and limits the harmonic overvoltage amplitude, which is beneficial to the stability of the distribution network. Further, the reactive power compensation device alleviates the heating phenomenon of the existing reactive power compensation device by reducing the fundamental wave loss of the filter resistor.

The above-mentioned embodiment only represents an embodiment of the present invention, and its description is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention.

Claims (10)

1. A reactive power compensation device, characterized in that: the reactive power compensation device is a three-phase circuit, which is respectively connected with the three-phase bus of the power distribution network; each phase circuit of the reactive power compensation device comprises a high-pass filter resistor and filter capacitors, series reactors and compensation capacitors connected in series in sequence; the filter capacitors of each phase circuit of the reactive power compensation device are respectively connected in series with the three-phase bus of the power distribution network, and each phase circuit of the reactive power compensation device is connected in series. The compensation capacitors are connected in a common star shape at the end of the branch where they are located; one end of the high-pass filter resistor of each phase circuit of the reactive power compensation device is respectively connected in series between the series reactor and the filter capacitor on the phase circuit, and the other end is connected to the branch where it is located. The ends are star-connected. 2. The reactive power compensation device according to claim 1, characterized in that: the reactive power compensation device further comprises a grounding resistor, and one end of the high-pass filter resistor in each phase circuit of the reactive power compensation device is respectively connected in series with Between the series reactor and the filter capacitor on the phase circuit, the other end is connected in a star shape at the end of the branch where it is located, and is grounded through the grounding resistor. 3 . The reactive power compensation device according to claim 1 , wherein the reactive power compensation device further comprises a fuse and a discharge coil, and the three primary coil input ends of the discharge coil are respectively connected to the non-current through the fuse. 4 . Between the busbar and the filter capacitor in each phase circuit of the power compensation device, the secondary coil of the discharge coil is respectively connected between the filter capacitor and the arrester on the three-phase circuit of the reactive power compensation device, and the secondary coil of the discharge coil is connected between the filter capacitor and the arrester on the three-phase circuit of the reactive power compensation device. The coil is also connected to the star connection point of each high-pass filter resistor. 4. The reactive power compensation device according to claim 3, characterized in that: the capacitive reactance of the filter capacitor Wherein U is the line voltage of the transmission line, and _IL is the rated current of the series reactor. 5 . The reactive power compensation device according to claim 4 , wherein the reactance value of the compensation capacitor is equal to the reactance value of the series reactor. 6 . 6. The reactive power compensation device according to any one of claims 4 or 5, wherein the reactive power compensation device further comprises a harmonic loss energy recovery unit, and the harmonic loss energy recovery unit comprises a rectifier, so The three input ends of the rectifier are respectively connected in series between the filter capacitor and the series reactor in the three-phase circuit of the reactive power compensation device, and at the same time, the three input ends of the rectifier are also connected to the three-phase circuit of the reactive power compensation device respectively. filter resistor connection in . 7 . The reactive power compensation device according to claim 6 , wherein the harmonic loss energy recovery unit further comprises a controller, a shunt and a voltage regulating silicon chain serially connected to the positive output end of the rectifier. 8 . ; The controller is respectively connected with the shunt and the voltage regulating silicon chain, and the controller receives the input signal of the shunt and outputs an electrical signal to the voltage regulating silicon chain. 8. The arrester protection device according to claim 7, wherein the harmonic loss energy recovery unit further comprises a check diode, the shunt, the voltage regulating silicon check diode and the voltage regulating silicon chain connected in series with the positive output terminal of the rectifier. 9 . The arrester protection device according to claim 8 , wherein the harmonic loss energy recovery unit further comprises two fuses, and the fuses are respectively connected in series with the positive output terminal and the negative output of the rectifier. 10 . end. 10 . The arrester protection device according to claim 9 , wherein the reactive power compensation device further comprises a zero-sequence current transformer, and the zero-sequence current transformer is connected in series with the three-phase of the reactive power compensation device. 11 . Between the filter capacitor and the series reactor in the circuit.

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