CN112736920A - Method and system for adjusting transmission power quality of power grid system - Google Patents

Abstract

The invention discloses a method for adjusting the transmission power quality of a power grid system, which comprises the following steps: collecting the power grid voltage and current output by a power grid system in real time, and determining the harmonic current before compensation on the basis of the power grid voltage and current; when network voltage drops, whether harmonic current exists in a transmission line of a system is detected, whether a first capacitor bank and/or a second capacitor bank in a series compensation branch circuit needs to be put into the line at present is judged according to a detection result, and electric energy transmitted in the line is primarily compensated; and calculating the reactive power factor of the system after primary compensation and the corresponding power grid voltage, and based on the calculation, when the current system running state meets the normal running condition, putting the parallel compensation branch into the line to perform secondary compensation on the system, thereby providing the power energy subjected to harmonic wave, grid voltage and reactive power compensation for the power grid load. The invention meets the treatment requirements of fast changing reactive power, voltage and harmonic wave, is not influenced by the parameters of a power grid and the change of load current, and has good compensation effect.

Description

Method and system for adjusting transmission power quality of power grid system

Technical Field

The invention relates to the technical field of power grid power, in particular to a method and a system for adjusting the transmission power quality of a power grid system.

Background

In recent years, with the acceleration of power grid construction and the deepening of energy-saving and consumption-reducing policies in China, the improvement of the power quality of a distribution line becomes the key point of attention and work in a power grid system. At present, rural and urban distribution lines have the problems of high line loss, low power factor, low tail end voltage, serious harmonic pollution and the like.

The conventional parallel compensation device is independently adopted for reactive compensation, the reactive compensation effect is good, but the voltage regulation capability is limited, and the user requirements are difficult to meet; the series compensation device is independently adopted, so that the line impedance can be reduced, namely the power supply radius is reduced, but the compensation degree is limited due to the restriction of the short circuit level of the system, the harmonic wave of the system cannot be absorbed, the electric influence under load is large, and the compensation effect is not ideal.

Because the low voltage of present distribution network is administered and energy-conserving to reduce and lose, there is limitation in the measure that can take, especially when there is the impact load of high energy consumption (mostly the circuit of the non-linear load) of changing rapidly on the circuit, can lead to the harmonic to pollute seriously, the circuit power factor is low, the terminal voltage is low, the voltage drops seriously. The conventional parallel compensation device (SVG) performs reactive compensation, harmonic suppression and voltage regulation, needs large installed capacity, and brings the problems of power factor reduction and network loss increase while regulating voltage. The series compensation device can only passively regulate voltage according to load current, when the load current is small, the voltage lifting effect is poor, and when the load current is large, the problem of overvoltage is easily generated, and when the compensation device is put into operation, system resonance is easily generated.

Disclosure of Invention

In order to solve the technical problem, the invention provides a method for adjusting the transmission power quality of a power grid system, which comprises the following steps: acquiring power grid voltage and current output by a power grid system in real time, and determining harmonic current before compensation on the basis of the power grid voltage and current; step two, when the grid voltage drop occurs in the power grid system, detecting whether the harmonic current exists in a system transmission line, judging whether a first capacitor bank and/or a second capacitor bank in a series compensation branch circuit need to be put into the line at present according to a detection result, and performing primary compensation aiming at the grid voltage drop and the harmonic current on electric energy transmitted in the line; and thirdly, calculating the reactive power factor of the system after primary compensation and the corresponding power grid voltage, and based on the calculation, when the current system operation state meets the normal operation condition, putting the parallel compensation branch circuit positioned at the rear end of the series compensation branch circuit into the circuit, and performing secondary compensation aiming at harmonic current and/or voltage regulation on the system, thereby providing power energy after harmonic, power grid voltage and reactive power compensation for the power grid load.

Preferably, in the second step, the method comprises the following steps: diagnosing the grid voltage drop phenomenon of the power grid by utilizing a preset terminal voltage safety threshold range according to the power grid voltage, and putting the first capacitor bank into the line after the drop phenomenon occurs; and detecting whether resonant current exists in a rear-end transmission line of the series compensation branch for multiple times, and sequentially judging whether the second capacitor bank needs to be put in, the first capacitor bank needs to be withdrawn and the second capacitor bank needs to be withdrawn so as to finish primary compensation control.

Preferably, in the step of detecting whether there is a resonant current in the rear-end transmission line located in the series compensation branch for multiple times, and sequentially determining whether the second capacitor bank needs to be put in, the first capacitor bank needs to be withdrawn, and the second capacitor bank needs to be withdrawn, so as to complete the primary compensation control, the method further includes: detecting whether resonance current exists in a rear-end transmission line of the series compensation branch circuit or not to detect the first harmonic current compensation effect, and if the resonance current does not exist in the rear-end transmission line, putting the second capacitor bank into the transmission line and entering a first exit mode for indicating that the capacitor bank exits from compensating the harmonic current; in the first type exit mode, second harmonic current compensation effect detection is firstly carried out, whether the first capacitor bank needs to exit is judged according to the detection result, then third harmonic current compensation effect detection is carried out, whether the second capacitor bank needs to exit is judged according to the detection result, and the series compensation branch circuit is controlled to form a series harmonic compensation structure in which the capacitor banks are all put into use, or the capacitor banks are all exited, or the first capacitor bank exits and the second capacitor bank is put into use.

Preferably, if the first harmonic current compensation effect detection result is qualified, after a preset second capacitor bank input time threshold value, inputting the second capacitor bank into the line, and entering a second exit mode; in the second exit mode, detecting the harmonic current compensation effect again, and if the harmonic current compensation effect is not qualified, restoring the second capacitor bank to an exit state to control the series compensation branch circuit to form a series harmonic compensation structure in which the first capacitor bank is put into and the second capacitor bank exits; otherwise, continuing to control the capacitor bank to be fully put into use.

Preferably, in the third step, the method comprises: and judging whether the power grid voltage after the initial compensation meets the terminal voltage optimization threshold range or not by utilizing a preset terminal voltage optimization threshold range according to the power grid voltage after the initial compensation, and if so, sending a harmonic compensation instruction for controlling the on-off state of each power device in the parallel compensation branch circuit to a power output module in the module.

Preferably, in the third step, the method further comprises: and if the power grid voltage after the initial compensation does not meet the terminal voltage optimization threshold range, sending a reactive power compensation instruction for controlling the on-off state of each power device in the power output module to the power output module, and controlling the parallel compensation branch to provide capacitive/inductive reactive power for the power grid system so as to perform secondary compensation.

Preferably, further, a serial branch tripping command is used for controlling the closed or open state of a serial bypass switch unit in the serial compensation branch for connecting the branch in the line in series so as to enable the serial compensation branch to be tripped out of or thrown into the line; controlling the closing or opening state of a series first/second bypass switch connected in series with the first capacitor bank by using a first/second capacitor bank switching-in/switching-out instruction, so that the first/second capacitor bank is switched in or switched out to the line; and controlling the on-off state of a parallel bypass switch unit in the parallel compensation branch circuit, which is used for connecting the branch circuit in parallel with the circuit, by using a parallel branch circuit switching-on/off instruction, so that the parallel compensation branch circuit is switched on or switched off to the circuit.

Preferably, the method further comprises: when the series compensation branch circuit has a fault, a series protection input instruction is utilized to withdraw the series compensation branch circuit from the circuit, and the capacitor bank is protected by a capacitor bank protection device in the series compensation branch circuit, wherein a capacitor bank protection instruction is generated at the same time, and the capacitor bank protection instruction is sent to an SCR module in the capacitor bank protection device, so that the SCR module drives a thyristor valve group unit to be conducted through a photoelectric trigger unit or a BOD trigger protection unit in the module under the control of the capacitor bank protection instruction, and the capacitor bank is protected.

Preferably, the method further comprises: when the series compensation branch circuit has a fault and exits from the circuit, the parallel compensation branch circuit is put into the circuit, and further generates a corresponding reactive power compensation instruction by combining the current system power grid voltage, and controls the parallel compensation branch circuit to provide capacitive reactive power for the power grid system.

The invention also provides a system for regulating the quality of the electric energy transmitted by a power grid system, which is used for executing the method, and the system is provided with: the series compensation branch circuit is connected in a power grid system transmission line in series, and comprises a first capacitor bank and a second capacitor bank which are connected in parallel; the parallel compensation branch is connected in parallel with the circuit and is positioned at the rear end of the series compensation branch; the comprehensive controller is connected with the series compensation branch and the parallel compensation branch and is used for acquiring the power grid voltage and current output by a power grid system in real time, determining harmonic current before compensation based on the harmonic current, detecting whether the harmonic current exists in a system transmission line when the power grid system drops, judging whether the first capacitor bank and/or the second capacitor bank in the series compensation branch needs to be put into the line currently according to a detection result, carrying out primary compensation aiming at the power grid voltage drop and the harmonic current on the electric energy transmitted in the line, calculating a system reactive power factor after the primary compensation and corresponding power grid voltage, putting the parallel compensation branch into the line based on the situation and carrying out secondary compensation aiming at the harmonic current and/or voltage regulation on the system when the current system operation state meets the normal operation condition, thereby providing the power energy compensated by harmonic wave, network voltage and reactive power to the load of the power grid.

Preferably, the series compensation branch comprises: a series bypass switch unit connected in series to the line, for controlling a self-closing or self-opening state by a series branch trip instruction so that the series compensation branch is tripped out of or thrown into the line; and the first/second bypass switch is connected with the first/second capacitor bank in series and used for controlling the self-closed or self-open state by utilizing a first/second capacitor bank switching-in/out command so as to switch in or switch out the first/second capacitor bank to the line.

Preferably, the series compensation branch further includes: the series protection device switching switch is connected in the line in series and used for receiving a series protection input instruction when the series compensation branch circuit fails and withdrawing the series compensation branch circuit from the line by using the instruction so as to protect the capacitor bank by using a capacitor bank protection device in the series compensation branch circuit; the capacitor bank protection device is connected with the switching switch unit of the series protection device, is provided with an SCR module and a current-limiting protection module, and is used for receiving a capacitor bank protection instruction when the series compensation branch circuit fails and sending the capacitor bank protection instruction to the SCR module, so that the SCR module drives the thyristor valve bank unit to be conducted through a photoelectric trigger unit or a BOD trigger protection unit in the module under the control of the capacitor bank protection instruction, and the capacitor bank is protected under the cooperation of the current-limiting protection module.

Preferably, the parallel compensation branch comprises: a parallel bypass switch unit connected in parallel to the line, for controlling a self-closing or self-opening state by using a parallel branch switching-on/off command, so that the series compensation branch is switched on or switched off to the line; a parallel branch reactor connected in series with the parallel bypass switch unit; and the power output module is connected with the parallel branch reactor in series and used for receiving a reactive power compensation command for controlling the on-off state of each power device in the module, providing capacitive/inductive reactive power for the power grid system by utilizing the command and under the coordination of the parallel branch reactor, receiving a harmonic compensation command for controlling the on-off state of each power device in the module, and providing harmonic compensation for the power grid system by utilizing the command and under the coordination of the parallel branch reactor.

Preferably, the system further comprises: and the protection module is connected with the integrated controller and is used for respectively executing protection control of the integrated controller between the series compensation branch and the power grid system transmission line and between the parallel compensation branch and the power grid system transmission line.

Compared with the prior art, one or more embodiments in the above scheme can have the following advantages or beneficial effects:

the invention provides a method and a system for adjusting the transmission power quality of a power grid system, which meet the fast changing reactive power, voltage and harmonic wave treatment requirements of the system by adopting a series and parallel cooperative compensation control mode, are not influenced by system parameters and load current change, and have good compensation effect. Furthermore, after the series compensation equipment is put into operation, the resonance problem possibly encountered in the operation of the power distribution network is solved, and the series compensation equipment adopts a multi-group grading switching intelligent control mode, so that the system resonance protection function is increased. In addition, the series compensation capacitor bank is quickly protected in the series compensation equipment by using advanced power electronic technology. Therefore, the invention overcomes the defects of low parallel efficiency when the parallel compensation equipment is used independently and large influence of the load of the power grid when the series compensation equipment is used independently, absorbs the advantages of the parallel compensation equipment and the series compensation equipment, and realizes a comprehensive compensation method with good compensation effect, low cost and system resonance protection function.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

fig. 1 is a step diagram of a method for adjusting transmission power quality of a power grid system according to an embodiment of the present application.

Fig. 2 is a specific flowchart of a method for adjusting transmission power quality of a power grid system according to an embodiment of the present application.

Fig. 3 is a circuit topology diagram of a system for adjusting transmission power quality of a power grid system according to an embodiment of the present application.

Fig. 4 is a schematic circuit topology diagram of a power output module in a system for adjusting transmission power quality of a power grid system according to an embodiment of the present application.

Fig. 5 is a schematic circuit topology diagram of an SCR module in a system for adjusting transmission power quality of a power grid system according to an embodiment of the present application.

Detailed Description

The following detailed description of the embodiments of the present invention will be provided with reference to the drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, the embodiments and the features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.

In recent years, with the acceleration of power grid construction and the deepening of energy-saving and consumption-reducing policies in China, the improvement of the power quality of a distribution line becomes the key point of attention and work in a power grid system. At present, rural and urban distribution lines have the problems of high line loss, low power factor, low tail end voltage, serious harmonic pollution and the like. The conventional parallel compensation device is independently adopted for reactive compensation, the reactive compensation effect is good, but the voltage regulation capability is limited, and the user requirements are difficult to meet; the series compensation device is independently adopted, so that the line impedance can be reduced, namely the power supply radius is reduced, but the compensation degree is limited due to the restriction of the short circuit level of the system, the system harmonic waves cannot be absorbed, the influence of the load current is large, and the compensation effect is not ideal.

Because the low voltage of present distribution network is administered and energy-conserving to reduce and lose, there is limitation in the measure that can take, especially when there is the impact load of high energy consumption (mostly the circuit of the non-linear load) of changing rapidly on the circuit, can lead to the harmonic to pollute seriously, the circuit power factor is low, the terminal voltage is low, the voltage drops seriously. The conventional parallel compensation device (SVG) performs reactive compensation, harmonic suppression and voltage adjustment, needs large installed capacity, and brings the problems of power factor reduction and network loss increase while adjusting voltage; the series compensation device can only passively regulate voltage according to load current, when the load current is small, the voltage lifting effect is poor, and when the load current is large, the problem of overvoltage is easily generated, and when the compensation device is put into operation, system resonance is easily generated.

In order to solve the above problem, embodiments of the present invention provide a method (hereinafter referred to as "transmission power quality adjusting method") and a system for adjusting transmission power quality of a power grid system. According to the method and the system, according to the conditions of reactive power, harmonic current and output voltage of an electric energy output circuit of a power grid system, firstly, aiming at grid voltage drop and harmonic current, precise primary compensation aiming at a series compensation device is carried out by adopting a multi-group graded switching mode, and specifically, the multi-stage compensation comprising first capacitor group input, second capacitor group exit and first capacitor group exit is carried out to form a corresponding series compensation structure; further, on the basis of the primary compensation process, secondary compensation is performed on the system power grid output according to the primary compensation effect (the power grid voltage, the reactive power factor, the branch circuit running state and the harmonic current condition after the primary compensation), wherein the secondary compensation is performed on whether the parallel compensation device is put into the system power grid output or not, so that the parallel compensation device further provides harmonic compensation or inductive reactive power compensation or capacitive reactive power compensation for the power grid system. Therefore, after series compensation equipment is put into use, the intelligent control mode of series compensation multi-group grading switching can increase the system resonance protection function aiming at the resonance problem possibly encountered in the operation of the power distribution network. In addition, the invention can track the reactive power, harmonic wave and voltage change of the power grid more quickly, carry out accurate compensation, is not influenced by system parameters and load current change, and has small capacity, low loss and good compensation effect. In addition, the invention uses the electronic switch adopting the advanced power electronic technology, and when the compensation device has a fault, the quick protection of the capacitor bank is realized by utilizing the principle that the response speed of the electronic switch is higher than that of the mechanical protection switch.

Fig. 1 is a step diagram of a method for adjusting transmission power quality of a power grid system according to an embodiment of the present application. As shown in fig. 1, the method comprises the steps of: step S110, the integrated controller 300 collects the power grid voltage and the power grid current which are output by the current power grid system in real time, and determines the harmonic current before compensation based on the real-time power grid voltage and the real-time power grid current; step S120, when the grid voltage drop occurs in the power grid system, the integrated controller 300 detects whether harmonic current exists in the current power grid system transmission line, judges whether the first capacitor bank C1 and/or the second capacitor bank C2 in the series compensation branch circuit 100 needs to be put into the current power grid system transmission line according to the detection result, and performs primary compensation aiming at the power grid voltage drop and the harmonic current on the electric energy transmitted by the line; step S130, the integrated controller 300 calculates the system reactive power factor after the initial compensation and the corresponding grid voltage (at this time, the grid voltage is the grid voltage compensated by the series compensation branch 100 and is the sum of the grid voltage before compensation and the compensation voltage provided by the series compensation branch 100), then, the integrated controller 300 puts the parallel compensation branch 200 located at the rear end of the series compensation branch 100 into the grid system transmission line according to the compensated grid line voltage, the compensated grid line current, the compensated system no-power factor and the harmonic content in the compensated circuit current when the current system operation state meets the grid load normal operation condition, and further carries out the secondary compensation based on the harmonic current and/or voltage adjustment of the initial compensation of step S120 on the current grid system, thereby providing the load connected to the grid system with the harmonic current compensation, And the network voltage after reactive power compensation.

Further, when determining whether the current system operating state meets the normal operating condition of the grid load, the integrated controller 300 needs to complete the following normal operation detection sub-steps according to the non-power factor of the system after the initial compensation, the voltage of the grid line after the initial compensation, the current of the grid line after the initial compensation and the harmonic content in the current of the line after the initial compensation, and after each normal operation detection sub-step is qualified, determines that the current system operating state meets the normal operating condition of the grid load. Wherein the normal operation detection substep comprises at least: whether the grid voltage after primary compensation has overvoltage or undervoltage faults, whether the grid current after primary compensation has overcurrent or undercurrent faults, whether the system no-power factor after primary compensation reaches the power required by the grid load, whether the harmonic content in the circuit current after primary compensation is reduced to the lowest harmonic content threshold value capable of bearing when the grid load normally operates, and the like. Further, firstly, the compensated power grid line voltage is compared with a preset power grid safe operation voltage threshold range, and if the current voltage is within the power grid safe operation voltage threshold range, the compensated power grid voltage is not subjected to overvoltage or undervoltage faults (qualified); otherwise, if the current voltage is higher than the upper limit value of the grid safe operation voltage threshold range, overvoltage faults (disqualification) occur, and if the current voltage is lower than the lower limit value of the grid safe operation voltage threshold range, undervoltage faults (disqualification) occur. Then, comparing the compensated power grid line current with a preset power grid safe operation current threshold range, and if the current is within the power grid safe operation current threshold range, judging that the compensated power grid voltage has no over-current or under-current fault (is qualified); otherwise, if the current is higher than the upper limit value of the grid safe operation current threshold range, overcurrent faults (disqualification) occur, and if the current is lower than the lower limit value of the grid safe operation current threshold range, undercurrent faults (disqualification) occur. Then, comparing the current compensated system no-power factor with the required input power when the load of the power grid is in safe operation, and judging that the compensated system no-power factor is qualified when the current compensated system no-power factor reaches or is higher than a preset safe operation power factor threshold; otherwise, the product is not qualified. Finally, comparing the harmonic content in the compensated circuit current calculated currently with the lowest harmonic content threshold value which can be borne by the power grid during safe operation, and judging that the harmonic content of the compensated system is qualified when the current harmonic content is lower than the preset lowest harmonic content threshold value for safe operation; otherwise, the product is not qualified.

It should be noted that, generally, if a conventional parallel compensation device is separately used for reactive compensation, the reactive compensation effect is good, but the voltage regulation capability is limited, and the user requirements are difficult to meet; the series compensation device is independently adopted, so that the impedance of the power transmission line can be reduced, namely the power supply radius is reduced, but the compensation degree is limited due to the restriction of the short circuit level of a power grid system, the harmonic generated by the power grid system cannot be absorbed, the electric shock caused by load is large, and the compensation effect is not ideal. However, the invention adopts a series-parallel cooperative compensation control mode, utilizes the series compensation device to adjust the voltage output capacity of the power grid system by detecting harmonic current so as to make up for the defect of limited voltage adjustment capacity when the parallel compensation device is used alone, and utilizes the parallel compensation device to make up for the defect of unsatisfactory compensation effect when the series compensation device is used alone, thus fully meeting the requirements of the power grid system for fast changing reactive power, fast changing voltage and harmonic treatment, being not influenced by system parameters and load current change and having good compensation effect.

Further, after the series compensation branch 100 is input to the power grid system transmission line in step S120, it needs to be further determined whether the current power grid system can reach a stable operation state, that is, whether information such as voltage, current, harmonic, and power input to the power grid load device satisfies a condition that the power grid load can stably operate, and when the information is reached, it indicates that the input of the series compensation branch 100 can effectively compensate the electric energy transmitted by the power grid system, and at this time, the parallel compensation branch 200 needs to be further used for compensation optimization of the electric energy transmitted by the power grid system; when the current information such as voltage, current, harmonic wave and power input to the power grid load equipment cannot meet the condition that the power grid load can stably operate, the compensation control of the series compensation branch circuit 100 on the electric energy transmitted by the power grid system needs to be immediately quitted, so that the compensation in various aspects such as harmonic wave compensation, grid voltage compensation and reactive power compensation is completed, and high-quality power grid electric energy is accurately and efficiently provided for the power grid load.

Before describing the transmission power quality adjusting method in detail, a system (transmission power quality adjusting system) for implementing the current transmission power quality adjusting method is described, wherein based on the method (method for adjusting transmission power quality of a power grid system) of the present invention, the present invention further provides a system for adjusting transmission power quality. Fig. 3 is a circuit topology diagram of a system for adjusting transmission power quality of a power grid system according to an embodiment of the present application. As shown in fig. 3, the transmission power quality adjusting system according to the present invention includes: a series compensation branch 100, a parallel compensation branch 200 and an integrated controller 300. The series compensation branch 100 is connected in series in the transmission line of the power grid system, the parallel compensation branch 200 is connected in parallel in the transmission line of the power grid system, and the integrated controller 300 is connected with the series compensation branch 100 and the parallel compensation branch 200 respectively. The integrated controller 300 is used for collecting the power grid voltage and current output by the power grid system in real time, determining the harmonic current before compensation based on the power grid voltage and current, then detecting whether the harmonic current exists in the transmission line of the power grid system, judging whether the first capacitor bank C1 and/or the second capacitor bank C2 in the series compensation branch circuit needs to be put into the current circuit at present according to the detection result, the primary compensation is carried out on the grid voltage drop and the harmonic current in the current line, and the system reactive power factor after the primary compensation and the corresponding grid voltage are calculated, when the current system running state meets the normal running condition, the compensation branch circuit in parallel connection is thrown into the current circuit, and performing secondary compensation on the system aiming at harmonic current and/or voltage regulation, thereby providing the power energy compensated by the harmonic, the network voltage and the reactive power to the load of the power grid. Further, the series compensation branch 100 includes a first capacitor bank C1 and a second capacitor bank C2 connected in parallel to each other, and is used for performing compensation control on the power energy output by the power grid system with respect to grid voltage drop and/or harmonic current.

Further, the series compensation branch 100 further includes: a series bypass switch unit QF1, a series first bypass switch KM1 and a series second bypass switch KM 2. The series bypass switch unit QF1 is integrated in the circuit breaker, and the series bypass switch unit QF1 is connected in series with the current power grid system power transmission line and used for controlling the series compensation branch 100 to be in a closing or opening state by using a series branch switching-off instruction (including a series branch quitting instruction and a series branch switching-on instruction), so that the series compensation branch 100 is quitted or switched into the current power grid system power transmission line. A series first bypass switch KM1 is integrated in the contactor. The series first bypass switch KM1 is connected in series with the first capacitor group C1, and the series first bypass switch KM1 and the first capacitor group C1 are formed as a first compensation unit, which is connected in parallel with the above-described series bypass switch unit QF 1. The series first bypass switch KM1 is used for controlling the first capacitor bank to be in a closing or opening state by using a first capacitor bank switching-on/off instruction (comprising a first capacitor bank switching-on instruction and a first capacitor bank exiting instruction), so that the first capacitor bank C1 is switched on or exits to the current power grid system power transmission line. A series second bypass switch KM2 is integrated in the contactor. The series second bypass switch KM2 is connected in series with the second capacitor bank C2, and the series second bypass switch KM2 and the second capacitor bank C2 are formed as a second compensation unit, wherein the second compensation unit is connected in parallel with the above-mentioned series bypass switch unit QF 1. The series second bypass switch KM2 is used for controlling the second capacitor bank to be in a closing or opening state by using a second capacitor bank switching-on/off instruction (comprising a second capacitor bank switching-on instruction and a second capacitor bank exiting instruction), so that the second capacitor bank C2 is switched on or exits to the current power grid system power transmission line.

Further, the series compensation branch further includes: a series protection device switching switch KM3 and a capacitor bank protection device. As shown in fig. 3, a series protection switching switch KM3 is integrated in the contactor. The series protection device switching switch KM3 is connected in series in a power transmission line of a power grid system, is connected in parallel with the first compensation unit or the second compensation unit, and is used for controlling the capacitor bank protection device to be in a switching-on state or a switching-off state by using a series protection switching-off instruction (comprising a series protection switching-in instruction and a series protection switching-out instruction), so that the capacitor bank protection device protects the capacitor bank or restores the state to be protected. The series protection device switching switch KM3 is used for receiving a series protection input instruction when the series compensation branch circuit has a fault, controlling the series protection device switching switch KM3 to be switched on by using the instruction, and quitting the series compensation branch circuit 100 from a power transmission line of a power grid system, so that a capacitor bank protection device in the series compensation branch circuit 100 protects a capacitor bank.

The capacitor bank protection device is connected in parallel with the series protection device switching switch KM3 and comprises an SCR module and a current-limiting protection module. And the capacitor bank protection device is used for receiving a capacitor bank protection instruction and sending the capacitor bank protection instruction to the SCR module when the series compensation branch circuit has a fault, so that the SCR module drives the thyristor valve bank unit to be conducted through a photoelectric trigger unit or a BOD trigger protection unit in the SCR module under the control of the capacitor bank protection instruction, and a capacitor bank device is protected under the cooperation of the current-limiting protection module. In the embodiment of the invention, the SCR module is a thyristor protection device with a BOD forced protection function. The current limiting protection module has a damped reactance characteristic for limiting current when the SCR module performs thyristor protection control, and includes at least a series-branch reactor L1 and a resistor R1 connected in parallel with each other.

Fig. 5 is a schematic circuit topology diagram of an SCR module in a system for adjusting transmission power quality of a power grid system according to an embodiment of the present application. As shown in fig. 5, the SCR module includes: the device comprises a photoelectric trigger unit, a thyristor valve group unit, an RC resistance-capacitance absorption unit, a BOD trigger protection unit, an output power gear selection unit and the like. After receiving a capacitor bank protection instruction, the SCR module immediately sends a trigger signal through the photoelectric trigger unit to conduct the thyristor, and quickly isolates a fault current bypass (a fault capacitor bank) from a power transmission line of a power grid system. In addition, in order to increase the reliability of the protection control of the SCR module, the triggering part of the thyristor valve group unit is also provided with a BOD triggering protection unit with an overvoltage automatic triggering function as a backup protection. Specifically, if a controller of the photoelectric trigger unit fails or a channel (optical fiber) is damaged, the thyristor valve group unit is forced to be conducted by the BOD trigger protection unit due to the fact that the voltage at two ends of the thyristor valve group unit rapidly rises to a protection set value of the thyristor valve group unit, so that a fault current bypass (fault capacitor group) is isolated from a power transmission line of a power grid system. Meanwhile, the output power gear selection unit can be preset according to different voltage protection levels.

Further, the series compensation branch 100 in the embodiment of the present invention employs a "power electronic switching type multi-stage series capacitor compensation device", which has the following improvement points compared with the conventional series capacitor compensation device: the switch for protecting the capacitor bank is characterized in that a traditional slow switch is replaced by a fast power electronic switch (SCR module) with the action time of 10us level, and the switch is switched fast to protect the capacitor bank; and secondly, the capacitor bank is switched in a grading manner, the compensation degree is increased, the compensation precision is improved, and the resonance protection function is also realized.

Further, the parallel compensation branch 200 at least includes: the power output system comprises a parallel bypass switch unit QF, a parallel branch reactor L and a power output module SVG. The parallel bypass switch unit QF is integrated in the circuit breaker. The parallel bypass switch unit QF is connected in parallel with the current power transmission line of the power grid system and used for controlling the parallel compensation branch 200 to be in a closing or opening state by using a parallel branch switching-on/off instruction (comprising a parallel branch switching-in instruction and a parallel branch exiting instruction), so that the parallel compensation branch is switched into or exited from the current power transmission line of the power grid system. The parallel branch reactor L is connected in series with the parallel bypass switching unit QF. The power output module SVG is connected with the parallel branch reactor L in series and used for receiving a reactive power compensation instruction for controlling the on-off state of each power device in the module and providing capacitive reactive power or inductive reactive power to a power grid system by utilizing the instruction and under the coordination of the parallel branch reactor L. In addition, the power output module SVG is also used for receiving a harmonic compensation instruction for controlling the on-off state of each power device in the module, and the harmonic compensation is provided for a power grid system by utilizing the instruction under the coordination of the parallel branch reactor L.

In addition, the parallel compensation branch 200 further includes: and starting the module. As shown in fig. 3, the starting module is configured to implement a soft charging function for the power output module SVG before the power output module SVG is started, and specifically includes a charging resistor R and a charging bypass contactor KM. The charging bypass contactor KM is integrated in the contactor. The charging bypass contactor KM can also respond to the parallel branch switching-on/off instruction and keeps consistent with the switching state of the parallel bypass switch unit QF. In addition, referring to fig. 3, the parallel compensation branch 200 further includes: and a current transformer TA. The current transformer TA is used to collect the current in the parallel compensation branch 200 in real time.

Furthermore, in the embodiment of the invention, the power output module SVG adopts a 10kV direct-hanging static dynamic reactive power generation device SVG, has the characteristics of high efficiency, inductive and capacitive stepless regulation and high compensation precision, and also has the function of harmonic compensation. Fig. 4 is a schematic circuit topology diagram of a power output module in a system for adjusting transmission power quality of a power grid system according to an embodiment of the present application. As shown in fig. 4, the power output module of the present invention includes: reactor L for connection to each phase of a power network line_A、L_B、L_CAnd the rear end of each phase reactor is connected with a converter valve group (a converter A, a converter B and a converter C). The converter valve group adopts a high-voltage cascade structure, each phase converter valve group is cascaded by 12H-bridge type converter modules, is connected in a three-phase Y shape and is positioned in a single-phase reactor L_A、L_B、L_CA back end.

In addition, the power transmission power quality adjusting system of the invention further comprises: and a protection module (not shown) connected to the integrated controller 300, wherein the protection module is configured to perform protection control of the integrated controller 300 between the series compensation branch 100 and the grid system transmission line and between the parallel compensation branch 200 and the grid system transmission line, respectively. With continued reference to fig. 3, the protection module includes: a first disconnector QS1, a second disconnector QS2 and a third disconnector QS. The first isolating switch QS1 is arranged on a connecting line between the first end of the first compensation branch and a power grid system power transmission line; the second isolating switch QS2 is arranged at a connecting line between the second end of the first compensation branch and the power grid system transmission line; and the third isolating switch QS is arranged on a connecting line between the parallel bypass switch unit QF and the power grid system transmission line. Generally, each switch inside the protection module is in a closed state under the control of the integrated controller 300 at the following parameter initialization setting stage; and in the stages of power grid maintenance and/or transmission power quality regulation system maintenance, the system is in a switching-off state.

Fig. 2 is a specific flowchart of a method for adjusting transmission power quality of a power grid system according to an embodiment of the present application. The method for adjusting the transmission power quality according to the present invention is described in detail below with reference to fig. 1 and 2.

First, in step S201 of step S110, the integrated controller 300 configures various preset parameters required by the transmission power quality adjustment system in the working process to perform parameter initialization setting of the transmission power quality adjustment system, and then, in step S202 of step S110, the integrated controller is configured. In addition, in step S201, the integrated controller 300 is further required to immediately generate a series branch input instruction and a parallel branch exit instruction, send the series branch input instruction to the series bypass switch unit QF1 for connecting the series compensation branch 100 in series in the power transmission line of the power grid system, so that the series bypass switch unit QF1 controls itself to be in the open-brake state under the control of the instruction, so that the series compensation branch 100 is input into the current power transmission line of the power grid system, and send the parallel branch exit instruction to the parallel bypass switch unit QF for connecting the parallel compensation branch 200 in parallel in the power transmission line of the power grid system, so that the parallel bypass switch unit QF controls itself to be in the open-brake state under the control of the instruction, so that the parallel compensation branch 200 exits from the current power transmission line of the power grid system.

Step S202, the integrated controller 300 collects the power grid (output) voltage and the power grid (output) current output by the power grid (distribution) system in real time, and calculates harmonic current information before the compensation control is executed by the transmission power quality adjusting system according to the current power grid output voltage and the current power grid output current (wherein the harmonic current information includes the magnitude and direction of the harmonic current and the harmonic current content). In addition, step S202 further needs to calculate the reactive power output by the current grid system by using the grid current and voltage information collected in real time. It should be noted that the system reactive power and harmonic current information calculated at this time are information directly output by the grid power distribution system, and are information before compensation control according to the present invention.

In this way, the initialization processing procedure of the compensation control in step S110 is completed through the above steps S201 to S202, and then the process proceeds to step S120 to complete the primary compensation control for the grid voltage drop and the line harmonic current through steps S203 to S217.

Firstly, in step S203 in step S120, the integrated controller 300 diagnoses a grid voltage drop phenomenon by using a lower limit value of a preset terminal voltage safety threshold range according to the grid voltage before current compensation, generates a first capacitor bank input instruction when the drop phenomenon occurs, sends the first capacitor bank input instruction to the series first bypass switch KM1 in the series compensation branch 100, and then enters step S204, so that the first capacitor bank C1 is input into a grid system transmission line under the control of the series first bypass switch KM 1. If the drop phenomenon does not occur, the process proceeds to step S202, and the initialization process of the compensation control is continued. When the grid voltage drop phenomenon of the power grid is judged, if the grid voltage before current compensation is lower than the lower limit value of the terminal voltage safety threshold range, the drop phenomenon is judged to occur; and if the current power grid voltage reaches or is higher than the lower limit value of the terminal voltage safety threshold range, judging that the drop phenomenon does not occur.

Further, in step S204, the series first bypass switch KM1 receives a first capacitor bank input instruction from the integrated controller 300, and under the control of the instruction, the switching state of the series first bypass switch KM1 connected in series with the first capacitor bank C1 is controlled to be a switching-on state, so that the first capacitor bank C1 connected in series with the series first bypass switch KM1 is input to the current transmission line of the grid system, and the first capacitor bank C1 is used to perform compensation control on the grid voltage drop of the grid system. In this way, the grid voltage drop compensation control in the primary compensation is completed by the above steps S203 and S204.

Then, whether a second capacitor bank C2 needs to be put in, the first capacitor bank C1 needs to be withdrawn, and the second capacitor bank C2 needs to be withdrawn in sequence through multiple detection and whether a resonant current exists in a power grid system transmission line where the series compensation branch 100 (rear end) is located, so that a corresponding series harmonic compensation structure is formed, so that the resonance current compensation control in the primary compensation is completed by using the currently-formed series harmonic compensation structure, and the steps S205 to S217 are performed. Specifically, multiple times of detection of the harmonic current compensation effect are required, and whether the first capacitor bank C1 and/or the second capacitor bank C2 needs to be further controlled to be put into or taken out of operation is determined according to the detection result of each time of the harmonic current compensation effect. The first harmonic current compensation effect detection in the embodiment of the present invention is to determine whether the harmonic content in the current line power grid current (i.e., the line power grid current after the line voltage drop compensation) based on the first capacitor bank C1 is lower than the minimum harmonic content threshold for safe operation, and if so, it indicates that the harmonic content in the current system line reaches the standard capable of enabling the power grid load to perform safe operation, and it is determined that the current system line does not contain harmonic current; if the harmonic content is equal to or higher than the harmonic content, the harmonic content in the current system line cannot reach the standard of enabling the power grid load to operate safely, and at the moment, the harmonic current in the current system line is judged.

Step S205 is that the integrated controller 300 performs first harmonic current compensation effect detection by detecting whether a resonant current exists in a power grid system transmission line located at the rear end of the series compensation branch 100, and if a harmonic current exists, it indicates that the first harmonic current compensation effect detection is not qualified, at this time, a second capacitor bank input instruction needs to be immediately generated, and the second capacitor bank input instruction is sent to the series second bypass switch KM2 in the series compensation branch 100 and then enters step S206, so that the second capacitor bank C2 is input into the power grid system transmission line under the control of the series second bypass switch KM2, and then enters a first exit mode for indicating that the capacitor bank exits the compensation harmonic current.

Then, in the first exit mode, the integrated controller 300 first performs second harmonic current compensation effect detection, determines whether the first capacitor bank needs to be exited according to the detection result, then performs third harmonic current compensation effect detection, and determines whether the second capacitor bank needs to be exited according to the detection result, so as to control the series compensation branch 100 to form a series harmonic compensation structure in which all the capacitor banks (C1, C2) are put in, all the capacitor banks (C1, C2) are exited, or the first capacitor bank C1 is exited and the second capacitor bank C2 is put in, so as to perform the first exit (control) mode in the resonance current compensation control on the grid system by using the series harmonic compensation structures formed under different conditions, and complete the first exit (control) mode through the following steps S206 to S213.

Further, the second bypass switch KM2 connected in series in step S206 (in the first exit control mode) receives a second capacitor bank input command from the integrated controller 300, and under the control of the command, the switching state of the second bypass switch KM2 connected in series with the second capacitor bank C2 is controlled to be in the on state, so that the second capacitor bank C2 connected in series with the second bypass switch KM2 is input to the current grid system transmission line, and at this time, the resonant current in the grid system is compensated and controlled (first harmonic current compensation) under the combined action of the first capacitor bank C1 and the second capacitor bank C2, and then the process proceeds to step S207.

Further, the step S207 (in the first exit control mode) of the integrated controller 300 performs the second harmonic current compensation effect detection, and determines whether to exit the first capacitor bank C1 according to the detection result. Specifically, in the embodiment of the present invention, since step S207 is a subsequent step to step S206 described above, the second harmonic current compensation effect described in step S207 is to detect whether the harmonic content in the system line grid current (i.e., the line grid current compensated by the common resonant current fed to the first capacitor bank C1 and the second capacitor bank C2 via the circuit) currently compensated by the first capacitor bank C1 and the second capacitor bank C2 is lower than the above-mentioned minimum harmonic content threshold for safe operation, if the harmonic content is equal to or higher than the preset harmonic content, the harmonic content in the current (after the first harmonic current compensation) system line cannot reach the standard capable of enabling the power grid load to safely operate, the harmonic current is still contained in the current system line, a first capacitor bank quitting instruction is generated, and sends the instruction to the series first bypass switch KM1 in the series compensation branch 100, and then proceeds to step S208.

Step S208, the series first bypass switch KM1 receives a first capacitor bank exit instruction from the integrated controller 300, and under the control of the instruction, the switching state of the series first bypass switch KM1 connected in series with the first capacitor bank C1 is controlled to be a switching-off state, so that the first capacitor bank C1 connected in series with the series first bypass switch KM1 exits from the current power grid system transmission line, at this time, only the second capacitor bank C2 is used to perform compensation control (second harmonic current compensation) on the resonant current of the power grid system, which indicates that after the second capacitor bank C2 is switched in step S206, the first harmonic current compensation control cannot effectively eliminate the harmonic influence in the power grid current of the power grid system, and thus the step S209 is performed.

Further, if it is detected that the harmonic content in the grid current of the system line currently based on the joint compensation action of the first capacitor bank C1 and the second capacitor bank C2 is lower than the minimum harmonic content threshold for safe operation in the second harmonic current compensation effect detection process, it indicates that the harmonic content in the system line currently (compensated by the first harmonic current) can reach the standard for safe operation of the grid load, and at this time, it is determined that the current system line does not contain the harmonic current, which indicates that the first harmonic current compensation control can effectively eliminate the harmonic influence in the grid current of the grid system after the second capacitor bank C2 is put into step S206, so that the operation goes to step S213. Step S213 keeps the operation state of the two types of capacitor banks currently put into operation.

Further, the step S209 of the integrated controller 300 (in the first exit control mode) performs the third detection of the harmonic current compensation effect, and determines whether to exit the second capacitor bank C2 according to the detection result. Specifically, in the embodiment of the present invention, since step S209 is a subsequent step to step S208, the third harmonic current compensation effect in step S209 is to detect whether the harmonic content in the system back-end line grid current (i.e. the line grid current compensated by the resonance current input into the second capacitor bank C2) currently based on the compensation action of only the second capacitor bank C2 is lower than the above-mentioned minimum harmonic content threshold for safe operation, if the harmonic content is equal to or higher than the second harmonic current, the harmonic content in the current system line (after the second harmonic current) cannot reach the standard capable of enabling the power grid load to safely operate, the harmonic current is still contained in the current system line, a second capacitor bank quitting instruction is generated, and sends the instruction to the second bypass switch KM2 in series in the series compensation branch 100, and then the process proceeds to step S210.

Step S210, the series second bypass switch KM2 receives a second capacitor bank exit instruction from the integrated controller 300, and under the control of the instruction, the switching state of the series second bypass switch KM2 connected in series with the second capacitor bank C2 is controlled to be the open state, so that the second capacitor bank C2 connected in series with the series second bypass switch KM2 exits from the current power grid system transmission line, at this time, the second harmonic current compensation control cannot effectively eliminate the harmonic influence in the power grid current of the power grid system, and then the step S211 is performed. Step S211 is to keep the power transmission quality adjusting system in the current operating state of exiting the two capacitor banks from the power transmission line of the grid system.

Further, in the step S209, if it is detected that the harmonic content in the grid current of the system line currently based on the compensation action of only the second capacitor bank C2 is lower than the above-mentioned minimum harmonic content threshold for safe operation in the third harmonic current compensation process, it indicates that the harmonic content in the system line currently (compensated by the second harmonic current) can reach the standard for safe operation of the grid load, and at this time, it is determined that the current system line does not contain the harmonic current, which indicates that the harmonic influence in the grid current of the grid system can be effectively eliminated by the second harmonic current compensation control after the first capacitor bank C1 exits in the step S208, so that the step S212 is skipped. Step S212 the transmission power quality regulation system maintains the operating state of currently being put into only the second capacitor bank C2.

Referring to fig. 2 again, in the step S205, the integrated controller 300 further detects whether a resonant current exists in a transmission line at the rear end of the power grid system where the series compensation branch 100 is located, so as to perform a first harmonic current compensation effect detection, and if no harmonic current is detected, then the current first harmonic current compensation effect is detected to be qualified, at this time, a second capacitor bank input instruction needs to be generated immediately after a preset second capacitor bank input time threshold value, and sends a second capacitance group throw command to the second bypass switch KM2 in series in the series compensation branch 100 and then to step S214, so that the second capacitor bank C2 is switched into the transmission line of the power grid system after the second capacitor bank is switched into the time threshold under the control of the series second bypass switch KM2, then, a second type exit control mode is entered for indicating that the capacitor bank exits the compensation harmonic current.

It should be noted that, in the embodiment of the present invention, since the capacitor bank connected in series is put into the power grid system, the impedance of the power grid system may be changed, and therefore, after stable operation is required for a period of time, it is continuously determined whether there is harmonic current under the condition, and in the case that no harmonic current is included in step S205, the present invention needs to control to put into the second capacitor bank C2 after the second capacitor bank is put into the time threshold. The size of the second capacitor bank throw-in time threshold is not limited in particular, and can be set by a person skilled in the art according to actual conditions, and preferably, the threshold can be 3 seconds.

Then, in the second exit mode, the integrated controller 300 performs (fourth) detection of the harmonic current compensation effect again, and if the harmonic current compensation effect is not qualified, the second capacitor bank C2 is restored to the exit state to control the series compensation branch 100 to form a series harmonic compensation structure in which the first capacitor bank C1 is put in and the second capacitor bank C2 exits; otherwise, the capacitor bank is continuously controlled to be fully put into use, so that the second exit (control) mode in the resonance current compensation control of the power grid system is performed by using the series harmonic compensation structure formed under different conditions, and the operation is completed through the following steps S214 to S217.

Specifically, further, step S214 (in the second exit control mode) receives a second capacitor bank input command from the integrated controller 300, and under the control of the command, controls the switching state of the second bypass switch KM2 connected in series with the second capacitor bank C2 to be a closed state, so that the second capacitor bank C2 connected in series with the second bypass switch KM2 is input into the current grid system transmission line, at this time, the resonant current in the grid system is compensated and controlled (third harmonic current compensation) under the combined action of the first capacitor bank C1 and the second capacitor bank C2, and then the process proceeds to step S215.

Further, the step S215 of the integrated controller 300 (in the second exit control mode) performs (fourth) detection of the harmonic current compensation effect again, and determines whether to exit the second capacitor bank C2 according to the detection result. Specifically, in the embodiment of the present invention, since step S215 is a subsequent step to step S214 described above, the fourth harmonic current compensation effect described in step S215 is to detect whether the harmonic content in the system line grid current (i.e., the line grid current compensated by the resonant current fed into the first capacitor bank C1 and fed into the second capacitor bank C2 via the circuit) currently based on the common compensation action of the first capacitor bank C1 and the second capacitor bank C2 is lower than the above-mentioned minimum harmonic content threshold for safe operation, and if the harmonic content is equal to or higher than the threshold, it indicates that the harmonic content in the system line (compensated by the third harmonic current) currently cannot reach the standard capable of enabling the safe operation of the grid load, that is, after the feeding of the second capacitor bank C2 in step S214, the third harmonic current compensation control cannot effectively eliminate the harmonic influence in the grid current of the grid system, at this time, it is determined that the current system line still contains harmonic current, a second capacitor bank exit instruction is generated, and the instruction is sent to the second bypass switch KM2 connected in series in the series compensation branch 100, and then the process proceeds to step S216.

At this time, the second bypass switch KM2 connected in series in step S216 receives a second capacitor bank exit instruction from the integrated controller 300, and under the control of the instruction, the switching state of the second bypass switch KM2 connected in series with the second capacitor bank C2 is controlled to be the open state, so that the second capacitor bank C2 connected in series with the second bypass switch KM2 is exited from the current power grid system transmission line, at this time, the third harmonic current compensation control cannot effectively eliminate the harmonic influence in the power grid current of the power grid system, and the process proceeds to step S217. Step S217 the transmission power quality regulation system maintains the operation state of currently being put into only the first capacitor bank C1.

Further, in the step S215, if it is detected that the harmonic content in the grid current of the system line, which is currently based on the joint compensation action of the first capacitor bank C1 and the second capacitor bank C2, is lower than the minimum harmonic content threshold for safe operation in the fourth harmonic current compensation process, it indicates that the harmonic content in the system line (which is currently compensated by the third harmonic current) can reach the standard for safe operation of the grid load, and at this time, it is determined that the current system line does not contain the harmonic current, that is, after the second capacitor bank C2 is put into the step S214, the third harmonic current compensation control can effectively eliminate the harmonic influence in the grid current of the grid system, so as to skip to the step S213.

In this way, the steps S205 to S217 complete the compensation control process of the resonant current of the output power electric energy of the power grid system by using the series compensation branch 100 in the embodiment of the present invention, so as to complete the primary compensation control process of the grid voltage drop and the resonant current compensation of the power grid system by using the series compensation branch 100 in the step S120.

Next, step S130 is performed to determine whether the compensation effect of the current series compensation branch 100 can enable a grid load device of the grid system to stably operate according to the current grid voltage and the current grid current after the primary compensation control, when the compensation effect of the current series compensation branch 100 can stably operate, it indicates that the compensation effect of the current series compensation branch 100 is better, the compensation control process can be further optimized by inputting the parallel compensation branch 200, if the compensation effect of the current series compensation branch 100 cannot solve the grid voltage drop and/or harmonic current problem in the power transmission energy of the grid system, the entire series compensation branch 100 needs to be completely withdrawn from the power transmission line of the grid system, and this process is completed through the following steps S218 to S225.

Specifically, with reference to fig. 2, in step S218, the integrated controller 300 needs to collect the grid voltage and the grid current after the initial compensation at the position located at the rear end of the series compensation branch 100 in the transmission line of the grid system, calculate the system reactive power factor after the initial compensation and the harmonic content after the initial compensation, and based on this, determine whether the current electric energy output to the grid system can satisfy the grid load stable (normal) operation state according to the above-mentioned method, that is, determine whether the current grid load operation state satisfies the normal operation state. Further, when the step S218 detects that the current load operation state of the power grid system meets the normal operation condition, the integrated controller 300 immediately generates a parallel branch input instruction, and sends the instruction to the parallel bypass switch unit QF, and then the process proceeds to step S220. In addition, when the integrated controller 300 in step S218 detects that the current load operation state of the power grid system does not satisfy the normal operation condition, it immediately generates a serial branch exit instruction, and sends the instruction to the serial bypass switch unit QF1, and then the process proceeds to step S219.

After receiving the serial branch exit instruction, the serial bypass switching unit QF1 in step S219 controls itself to be in a closing state under the control of the instruction, so that the entire serial compensation branch 100 exits from the current power grid system transmission line, and then the process proceeds to step S220.

After receiving the parallel branch input command, the parallel bypass switch unit QF in step S220 controls itself to be in a closing state under the control of the command, so that the parallel compensation branch 200 is integrally input into the current transmission line of the power grid system, and then the process proceeds to step S221 to perform secondary compensation control including harmonic current and reactive power compensation (voltage regulation).

Step S221, the integrated controller 300 determines, according to the primarily compensated power grid voltage, whether the current primarily compensated power grid voltage meets the terminal voltage optimization threshold range by using the preset terminal voltage optimization threshold range, and if so, sends a harmonic compensation instruction for controlling the on-off state of each power device in the parallel compensation branch 200 to the power output module SVG in the module, so that the parallel compensation branch 200 performs harmonic compensation in secondary compensation on the current power grid voltage only by using the power output module SVG. It should be noted that, in the embodiment of the present invention, in order to achieve the effect of optimizing the primary compensation control, the terminal voltage optimization threshold range is within the terminal voltage safety threshold range, and the voltage range involved in the terminal voltage optimization threshold range is included (smaller) than the terminal voltage safety threshold range.

At this time, the power output module SVG in the parallel compensation branch 200 in step S222 receives and detects the current harmonic compensation command, and controls the on-off state and the corresponding on-off timing of each power device in the parallel compensation branch to provide the compensation harmonic only to the current power grid system under the control of the current harmonic compensation command.

Further, in step S221, if the integrated controller 300 determines that the grid voltage after the current initial compensation does not satisfy the terminal voltage optimization threshold range and satisfies the terminal voltage safety threshold range (indicating that the grid voltage after the current initial compensation may belong to a range between a lower limit value of the terminal voltage optimization threshold range and a lower limit value of the terminal voltage safety threshold range, or may belong to a range between an upper limit value of the terminal voltage optimization threshold range and an upper limit value of the terminal voltage safety threshold range), it needs to enter step S223, and according to the grid voltage after the current initial compensation, a reactive power compensation instruction for controlling the on-off state of each power device in the parallel compensation branch 200 is sent to the power output module SVG in the parallel compensation branch 200, so as to control the parallel compensation branch 200 to provide the capacitive reactive power or the inductive reactive power to the current grid system by using the power output module SVG, thereby performing voltage regulation compensation in the secondary compensation.

Specifically, step S223 the integrated controller 300 determines whether the grid voltage after the current initial compensation is between the lower limit value of the terminal voltage safety threshold range and the lower limit value of the terminal voltage optimization threshold range, if so, it indicates that the grid voltage after the current initial compensation is low, and immediately combines the grid voltage after the initial compensation and the terminal voltage safety threshold range, calculates the compensation regulation voltage that the parallel compensation branch 200 needs to provide to the grid transmission line currently, generates a corresponding reactive power compensation instruction, and sends the instruction to the power output module SVG, so that the power output module SVG outputs the capacitive reactive power meeting the current compensation regulation voltage level to the grid system in cooperation with the parallel branch reactor L connected to the power output module SVG, so as to perform voltage regulation, thereby entering step S224.

At this time, the power output module SVG in step S224 receives and detects the current reactive power compensation command, and controls the on-off state and the corresponding on-off timing of each power device in its own under the control of the current harmonic compensation command, so as to provide capacitive reactive power meeting the current compensation regulation voltage level to the current power grid system under the cooperation of the parallel branch reactor L, thereby completing the current voltage regulation process.

In addition, step S223, the integrated controller 300 determines that if the grid voltage after the current initial compensation is between the upper limit value of the terminal voltage optimization threshold range and the upper limit value of the terminal voltage safety threshold range, it indicates that the grid voltage after the current initial compensation is higher, and immediately combines the grid voltage after the initial compensation and the terminal voltage safety threshold range, calculates the compensation regulation voltage that the parallel compensation branch circuit 200 currently needs to provide to the grid transmission line, generates a corresponding reactive power compensation instruction, and sends the instruction to the power output module SVG, so that the power output module SVG outputs the inductive reactive power meeting the current compensation regulation voltage level to the grid system in cooperation with the parallel branch circuit reactor L connected to the power output module SVG, so as to perform voltage regulation, thereby entering step S225.

At this time, the power output module SVG in step S225 receives and detects the current reactive power compensation command, and under the control of the current harmonic compensation command, controls the on-off state and the corresponding on-off timing of each power device in the power output module SVG to provide inductive reactive power meeting the current compensation regulation voltage level to the current power grid system in cooperation with the parallel branch reactor L, thereby completing the current voltage regulation process.

In this way, the secondary compensation control process in step S130 is completed through step S218 to step S225, so that the harmonic, voltage regulation and reactive power compensation control is currently completed by the transmission power quality regulating system to provide the high-quality grid power energy compensated by the harmonic, grid voltage and reactive power to the grid load.

In addition, the method of the present invention further comprises the steps of collecting and detecting the grid voltage and the grid current before compensation directly output by the grid system in real time by the integrated controller 300, detecting the overcurrent and/or overvoltage phenomena at the level of the grid system, when overcurrent and/or overvoltage phenomena of a power grid system (before compensation) occur, a serial branch exit instruction for protecting the serial compensation branch 100 and a parallel branch exit instruction for protecting the parallel compensation branch 200 are immediately generated, the currently generated instructions are respectively sent to corresponding compensation branches, so as to control the serial bypass switch unit QF1 to be in a closing state and the parallel bypass switch unit QF to be in an opening state, therefore, the series compensation branch circuit 100 and the parallel compensation branch circuit 200 are timely withdrawn from the power transmission line of the power grid system to protect the internal capacitor bank and the power device.

In addition, in the method of the present invention, the integrated controller 300 can also detect the operation state in the series compensation branch 100 in real time, when the branch fails, a serial branch exit instruction and a serial protection input instruction in the serial protection input/output instruction are immediately generated, and respectively sends the instruction to a series bypass switch unit QF1 and a series protection device switching switch KM3 which is connected with the series bypass switch unit QF1 in parallel, so that the series bypass switching unit QF1 is in a closing state under the control of the series branch exit command, and the series protection switching switch KM3 is in a closing state under the control of the series protection switching command, therefore, the series compensation branch 100 is withdrawn from the current power grid system transmission line, so as to further perform protection control on the first capacitor bank C1 and the second capacitor bank C2 through a capacitor bank protection device in the series compensation branch 100.

Specifically, the integrated controller 300 detects the input current and terminal voltage of the first capacitor bank C1 and the input current and terminal voltage of the second capacitor bank C2 in real time, so as to determine whether the series compensation branch 100 is in a normal operating state, that is, whether the series compensation branch 100 is in a fault state, by determining whether the current and voltage flowing through the first capacitor bank C1 are in an overcurrent and/or overvoltage phenomenon or not, and determining whether the current and voltage flowing through the second capacitor bank C2 are in an overcurrent and/or overvoltage phenomenon or not. When judging that the current series compensation branch 100 has a fault, the integrated controller 300 needs to generate a capacitor bank protection instruction at the same time in addition to the series protection input instruction, and send the capacitor bank protection instruction to the SCR module, so that the SCR module drives the thyristor valve bank unit to be turned on through a photoelectric trigger unit or a BOD trigger protection unit in the module (SCR module) under the control of the capacitor bank protection instruction, thereby completing the protection for the first capacitor bank C1 and the second capacitor bank C2. In this way, since the SCR module belongs to the electronic power switch, when the protection control of the series compensation branch is performed, the action response time of the electronic power switch is faster than that of the mechanical switches such as QF and KM3, so that the protection operation of driving the thyristor valve group unit to be turned on can be performed first when the mechanical switches do not complete the exit protection of the capacitor group under the rapid exit operation of the electronic switch, so that the series compensation branch 100 can exit from the system line quickly and protect the capacitor group in time.

In addition, after the integrated controller 300 determines that the series compensation branch 100 has a fault and withdraws the series compensation branch from the current transmission line, the parallel compensation branch needs to be further input into the current line for voltage regulation and compensation because the voltage of the line grid at this time is low. Specifically, after judging that the series compensation branch 100 has a fault and withdrawing the series compensation branch from the current power transmission line, the integrated controller 300 needs to immediately generate a parallel branch input instruction in a parallel branch input/output instruction and send the instruction to the parallel bypass switch unit QF, so that the parallel bypass switch unit QF is switched on under the control of the instruction, and inputs the parallel compensation branch 200 into the current power transmission line, and then generates a corresponding reactive power compensation instruction by combining with the current system power grid voltage, and sends the instruction to the power output module SVG, so that the power output module SVG outputs capacitive reactive power meeting the current compensation voltage under the control of the current reactive power compensation instruction, and provides the capacitive reactive power for the power transmission line of the power grid system under the cooperation of the parallel branch reactor L.

The invention provides a method and a system for adjusting the transmission power quality of a power grid system, which meet the fast changing reactive power, voltage and harmonic wave treatment requirements of the system by adopting a series and parallel cooperative compensation control mode, are not influenced by system parameters and load current change, and have good compensation effect. Furthermore, after the series compensation equipment is put into use, the series compensation equipment adopts a multi-group grading switching intelligent control mode to increase the system resonance protection function aiming at the resonance problem possibly encountered in the operation of the power distribution network. In addition, the series compensation capacitor bank is quickly protected in the series compensation equipment by using advanced power electronic technology. Therefore, the invention overcomes the defects of low parallel efficiency when the parallel compensation equipment is used independently and large influence of the load of the power grid when the series compensation equipment is used independently, absorbs the advantages of the parallel compensation equipment and the series compensation equipment, and realizes a comprehensive compensation method with good compensation effect, low cost and system resonance protection function.

The above description is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (14)

1. A method for adjusting the quality of power transmitted by a power grid system, comprising:

acquiring power grid voltage and current output by a power grid system in real time, and determining harmonic current before compensation on the basis of the power grid voltage and current;

step two, when the grid voltage drop occurs in the power grid system, detecting whether the harmonic current exists in a system transmission line, judging whether a first capacitor bank and/or a second capacitor bank in a series compensation branch circuit need to be put into the line at present according to a detection result, and performing primary compensation aiming at the grid voltage drop and the harmonic current on electric energy transmitted in the line;

and thirdly, calculating the reactive power factor of the system after primary compensation and the corresponding power grid voltage, and based on the calculation, when the current system operation state meets the normal operation condition, putting the parallel compensation branch circuit positioned at the rear end of the series compensation branch circuit into the circuit, and performing secondary compensation aiming at harmonic current and/or voltage regulation on the system, thereby providing power energy after harmonic, power grid voltage and reactive power compensation for the power grid load.

2. The method according to claim 1, wherein in the step two, the method comprises:

diagnosing the grid voltage drop phenomenon of the power grid by utilizing a preset terminal voltage safety threshold range according to the power grid voltage, and putting the first capacitor bank into the line after the drop phenomenon occurs;

and detecting whether resonant current exists in a rear-end transmission line of the series compensation branch for multiple times, and sequentially judging whether the second capacitor bank needs to be put in, the first capacitor bank needs to be withdrawn and the second capacitor bank needs to be withdrawn so as to finish primary compensation control.

3. The method according to claim 2, wherein in the step of detecting whether there is a resonant current in the back-end transmission line of the series compensation branch for multiple times, and sequentially determining whether the second capacitor bank needs to be switched in, the first capacitor bank needs to be switched out, and the second capacitor bank needs to be switched out, so as to complete the primary compensation control, the method further comprises:

detecting whether resonance current exists in a rear-end transmission line of the series compensation branch circuit or not to detect the first harmonic current compensation effect, and if the resonance current does not exist in the rear-end transmission line, putting the second capacitor bank into the transmission line and entering a first exit mode for indicating that the capacitor bank exits from compensating the harmonic current;

in the first type exit mode, second harmonic current compensation effect detection is firstly carried out, whether the first capacitor bank needs to exit is judged according to the detection result, then third harmonic current compensation effect detection is carried out, whether the second capacitor bank needs to exit is judged according to the detection result, and the series compensation branch circuit is controlled to form a series harmonic compensation structure in which the capacitor banks are all put into use, or the capacitor banks are all exited, or the first capacitor bank exits and the second capacitor bank is put into use.

4. The method of claim 3,

if the first harmonic current compensation effect detection result is qualified, after a preset second capacitor bank input time threshold value, inputting the second capacitor bank into the circuit, and entering a second exit mode;

in the second exit mode, detecting the harmonic current compensation effect again, and if the harmonic current compensation effect is not qualified, restoring the second capacitor bank to an exit state to control the series compensation branch circuit to form a series harmonic compensation structure in which the first capacitor bank is put into and the second capacitor bank exits; otherwise, continuing to control the capacitor bank to be fully put into use.

5. The method according to any one of claims 1 to 4, characterized in that in the third step, the method comprises:

and judging whether the power grid voltage after the initial compensation meets the terminal voltage optimization threshold range or not by utilizing a preset terminal voltage optimization threshold range according to the power grid voltage after the initial compensation, and if so, sending a harmonic compensation instruction for controlling the on-off state of each power device in the parallel compensation branch circuit to a power output module in the module.

6. The method according to claim 5, wherein in step three, further comprising:

and if the power grid voltage after the initial compensation does not meet the terminal voltage optimization threshold range, sending a reactive power compensation instruction for controlling the on-off state of each power device in the power output module to the power output module, and controlling the parallel compensation branch to provide capacitive/inductive reactive power for the power grid system so as to perform secondary compensation.

7. The method according to any one of claims 1 to 6, further comprising,

controlling a closed or open state of a series bypass switch unit in the series compensation branch for connecting the branch in series with the line by using a series branch switching-on/off instruction, so that the series compensation branch is switched out or switched into the line;

controlling the closing or opening state of a series first/second bypass switch connected in series with the first capacitor bank by using a first/second capacitor bank switching-in/switching-out instruction, so that the first/second capacitor bank is switched in or switched out to the line;

and controlling the on-off state of a parallel bypass switch unit in the parallel compensation branch circuit, which is used for connecting the branch circuit in parallel with the circuit, by using a parallel branch circuit switching-on/off instruction, so that the parallel compensation branch circuit is switched on or switched off to the circuit.

8. The method according to any one of claims 1 to 7, further comprising:

when the series compensation branch circuit has a fault, the series compensation branch circuit is withdrawn from the circuit by using a series protection input instruction, and the capacitor bank is protected by a capacitor bank protection device in the series compensation branch circuit,

and simultaneously generating a capacitor bank protection instruction, and sending the capacitor bank protection instruction to an SCR module in the capacitor bank protection device, so that the SCR module drives a thyristor valve bank unit to be conducted through a photoelectric trigger unit or a BOD trigger protection unit in the module under the control of the capacitor bank protection instruction, thereby protecting the capacitor bank.

9. The method of claim 8, further comprising:

when the series compensation branch circuit has a fault and exits from the circuit, the parallel compensation branch circuit is put into the circuit, and further generates a corresponding reactive power compensation instruction by combining the current system power grid voltage, and controls the parallel compensation branch circuit to provide capacitive reactive power for the power grid system.

10. A system for regulating the quality of transmitted electric energy of a power grid system, the system being adapted to perform the method according to any of claims 1-9, the system comprising:

the series compensation branch circuit is connected in a power grid system transmission line in series, and comprises a first capacitor bank and a second capacitor bank which are connected in parallel;

the parallel compensation branch is connected in parallel with the circuit and is positioned at the rear end of the series compensation branch;

the comprehensive controller is connected with the series compensation branch and the parallel compensation branch and is used for acquiring the power grid voltage and current output by a power grid system in real time, determining harmonic current before compensation based on the harmonic current, detecting whether the harmonic current exists in a system transmission line when the power grid system drops, judging whether the first capacitor bank and/or the second capacitor bank in the series compensation branch needs to be put into the line currently according to a detection result, carrying out primary compensation aiming at the power grid voltage drop and the harmonic current on the electric energy transmitted in the line, calculating a system reactive power factor after the primary compensation and corresponding power grid voltage, putting the parallel compensation branch into the line based on the situation and carrying out secondary compensation aiming at the harmonic current and/or voltage regulation on the system when the current system operation state meets the normal operation condition, thereby providing the power energy compensated by harmonic wave, network voltage and reactive power to the load of the power grid.

11. The system of claim 10, wherein the series compensation branch comprises:

a series bypass switch unit connected in series to the line, for controlling a self-closing or self-opening state by a series branch trip instruction so that the series compensation branch is tripped out of or thrown into the line;

and the first/second bypass switch is connected with the first/second capacitor bank in series and used for controlling the self-closing or self-opening state by utilizing a first/second capacitor bank switching-in/switching-out command so as to switch in or switch out the first/second capacitor bank to the line.

12. The system of claim 10 or 11, wherein the series compensation branch further comprises:

the series protection device switching switch is connected in the line in series and used for receiving a series protection input instruction when the series compensation branch circuit fails and withdrawing the series compensation branch circuit from the line by using the instruction so as to protect the capacitor bank by using a capacitor bank protection device in the series compensation branch circuit;

the capacitor bank protection device is connected with the switching switch unit of the series protection device, is provided with an SCR module and a current-limiting protection module, and is used for receiving a capacitor bank protection instruction when the series compensation branch circuit fails and sending the capacitor bank protection instruction to the SCR module, so that the SCR module drives the thyristor valve bank unit to be conducted through a photoelectric trigger unit or a BOD trigger protection unit in the module under the control of the capacitor bank protection instruction, and the capacitor bank is protected under the cooperation of the current-limiting protection module.

13. The system according to any one of claims 10 to 12, wherein the parallel compensation branch comprises:

a parallel bypass switch unit connected in parallel to the line, for controlling a self-closing or self-opening state by using a parallel branch switching-on/off command, so that the series compensation branch is switched on or switched off to the line;

a parallel branch reactor connected in series with the parallel bypass switch unit; and

and the power output module is connected with the parallel branch reactor in series and used for receiving a reactive power compensation command for controlling the on-off state of each power device in the module, providing capacitive/inductive reactive power for the power grid system by using the command and under the coordination of the parallel branch reactor, receiving a harmonic compensation command for controlling the on-off state of each power device in the module, and providing harmonic compensation for the power grid system by using the command and under the coordination of the parallel branch reactor.

14. The system of claim 13, further comprising: and the protection module is connected with the integrated controller and is used for respectively executing protection control of the integrated controller between the series compensation branch and the power grid system transmission line and between the parallel compensation branch and the power grid system transmission line.

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