Flexible loop closing device based on series-parallel cooperative adjustment

Abstract

The invention belongs to the technical field of flexible networking of a power distribution network, and discloses a flexible loop closing device based on series-parallel cooperative adjustment, so as to solve the defects in the prior art. The device comprises a main loop, a bypass loop, data acquisition equipment and a control and protection system, wherein the main loop comprises a parallel transformer, a parallel power valve group, a series power valve group and a series transformer; the input end of the primary winding of the shunt transformer is connected with an inlet wire 1, and the output end forms a neutral point after star connection; the input of the series transformer power valve group is respectively connected with the taps of the secondary winding of the series transformer, and the output terminal is connected with the output of the three power valves in the parallel power valve group after being connected in series; a primary winding of the series transformer is connected in series between the inlet wire 1 and the inlet wire 2; the bypass loop is connected in parallel between the inlet wire 1 and the inlet wire 2; the data acquisition equipment is used for monitoring voltage and current parameters of the incoming line 1 and the incoming line 2; the control and protection system is used for collecting voltage, current and device state signals and controlling the working state of the power valve.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible networking of distribution networks, and particularly relates to a flexible loop closing device based on series-parallel collaborative regulation. Background Art

[0002] As the core of the construction of a new power system, the distribution network is facing challenges brought about by the high proportion of distributed resources access. The traditional "closed-loop design, open-loop operation" mode can no longer meet the requirements, and there are mainly five major problems: First, the power flow mutual assistance ability between lines is insufficient, resulting in low asset utilization rate, and the access of new energy power generation and electric vehicles causes local heavy overload; Second, the new energy connection point does not match the load area, and the electric power needs to be transmitted over a long distance, resulting in increased line losses; Third, the partition power supply and the power fluctuations of new sources and loads lead to too large voltage amplitude difference and phase difference at the connection points, making it difficult to transfer power in loop closing, and affecting power supply reliability; Fourth, the multi-branch and multi-connection structure is complex, the voltage difference between lines is large, and the operation and management difficulty increases; Fifth, there are obvious defects in the existing flexible interconnection technologies. For example, the all-power electronic scheme has high cost, large loss and low reliability, and new devices such as phase-shifting transformers and SEN transformers face problems such as insufficient regulation accuracy.

[0003] In summary, there are still many problems in the existing distribution network, such as low equipment utilization rate, limited power flow mutual assistance, difficult new energy consumption, low power supply reliability, complex multi-branch and multi-connection, and technical cost and performance bottlenecks. These problems seriously restrict the flexibility of the distribution network and the ability of resource optimization allocation, and it is urgent to break through the technical bottleneck. Summary of the Invention

[0004] Based on the above-mentioned disadvantages and deficiencies in the prior art, one of the objectives of the present invention is to at least solve one or more of the above-mentioned problems in the prior art. In other words, one of the objectives of the present invention is to provide a flexible loop closing device based on series-parallel collaborative regulation that meets one or more of the foregoing requirements, so as to achieve the purpose of expanding the regulation range, improving the regulation accuracy, and reducing the construction cost.

[0005] In order to achieve the above-mentioned invention objective, the present invention adopts the following technical solutions: The present invention provides a flexible loop closing device based on series - parallel collaborative regulation. The main circuit is used to extract energy from the parallel transformers, select the parallel secondary windings participating in the synthesis of the compensation voltage, recombine the obtained secondary winding voltages, and then inject a compensation voltage into the line through the series transformer to achieve flexible loop closing and power flow regulation. The bypass circuit is connected in parallel between the incoming line 1 and the incoming line 2 and is used to bypass the main circuit to achieve load transfer in the case of planned power outage transfer or load transfer caused by a fault resulting in the loss of power on one side of the power supply. The data acquisition device is used to monitor the voltage parameters and current parameters of the bypass circuit to obtain voltage signals and current signals. The control and protection system is used to calculate the real - time power of the voltage difference of the bypass circuit according to the received voltage signals and current signals, and adjust the working states of the parallel transformer power valve group and the series transformer power valve group in the main circuit in real time, as well as control the protection algorithm.

[0006] As a preferred solution, the main circuit includes a parallel transformer T1, a parallel transformer power valve group, a series transformer power valve group, and a series transformer T2 connected in sequence. The input end of the primary winding of the parallel transformer T1 is connected to the incoming line 1, and the output ends of the primary windings are star - connected to form a neutral point. The parallel transformer T1 is a multi - winding and multi - asymmetric tap transformer, and its primary winding is connected in parallel to the primary circuit. The multiple taps of each secondary winding are respectively connected to different input ends of the parallel transformer power valve group. The series transformer T2 is a multi - asymmetric tap transformer, its primary side is connected in series to the main circuit, and its secondary side is connected to different input ends of the series transformer power valve group. The parallel transformer power valve group is used to select different taps of different secondary windings and combine them to generate an adjustable synthetic voltage vector. The series transformer power valve group is used to select different taps of the series transformer T2 and couple the synthetic voltage vector to the main circuit.

[0007] As a preferred solution, each phase of the parallel transformer T1 is provided with three asymmetric secondary windings, and there are a total of nine windings in three phases. The voltage ratio of the asymmetric secondary windings is 1:2.

[0008] As a preferred solution, the series transformer T2 is provided with five taps, and the turns ratios of the five taps are 2:1, 1.9:1, 1.75:1, 1.5:1, and 1:1 respectively.

[0009] As a preferred solution, the parallel transformer power valve group includes multiple bridge arms. Each bridge arm includes a set of thyristor valves. The three inputs of each thyristor valve are correspondingly connected to the three taps of a secondary winding of the parallel transformer T1, and the combination of the two windings is selected by controlling the on - off of the thyristors.

[0010] As a preferred solution, the inputs of the series-variable power valve group are respectively connected to the taps of the secondary winding of the series transformer T2, and the output terminals of the series-variable power valve group are connected to the output after three power valves in the parallel power valve group are connected in series; the series-variable power valve group includes multiple bridge arms, each bridge arm includes a set of thyristor valves, and the five inputs of each power valve group are correspondingly connected to the five taps of the series transformer T2, and the turns ratio of the series transformer T2 is selected by controlling the on-off of the thyristors.

[0011] As a preferred solution, each bridge arm of the thyristor power valve group includes a pair of thyristors connected in anti-parallel and their attached absorption resistance and capacitance.

[0012] As a preferred solution, switches QF1 and QF2 are respectively arranged on the incoming line 1 and the incoming line 2; a bypass switch QF0 is arranged in the bypass circuit; the data acquisition device includes a voltage transformer PT1 and a current transformer CT1 arranged on the incoming line 1, and a voltage transformer PT2 and a current transformer CT2 arranged on the incoming line 2.

[0013] As a preferred solution, the control and protection algorithm adjusted in real time by the control and protection system includes a flexible loop closing algorithm, and the steps of the control and protection system adjusting the flexible loop closing algorithm in real time include: Close the switch QF1, start the data acquisition device to collect data and calculate the voltage difference between the two sides of the incoming line 1 and the incoming line 2; Based on the voltage difference, determine the corresponding parallel power valve gear and series power valve gear; Unlock the variable power valve and generate a synthetic voltage vector; Unlock the series-variable power valve, adjust the accuracy, and couple the synthetic voltage vector to the main circuit; Close the outgoing switch QF2 to complete the flexible loop closing and enter the loop closing operation mode.

[0014] As a preferred solution, the control and protection algorithm adjusted in real time by the control and protection system further includes a power flow transfer algorithm, and the steps of the control and protection system adjusting the power flow transfer algorithm in real time include: Based on the received power flow transfer instruction, determine the power flow direction and the power flow target value; Adjust the parallel power valve group to select the corresponding winding combination; Adjust the turns ratio and accuracy of the series power valve group; Judge whether the power flow error is within the allowable range. If not, repeat the above steps to gradually approach the power flow target value until the power flow error is within the allowable range.

[0015] As a preferred solution, the control and protection algorithm adjusted in real time by the control and protection system further includes a load transfer control algorithm. The steps for the control and protection system to adjust the load transfer control algorithm in real time are as follows: Lock the parallel power valve group and adjust the series power valve group to gear 0; Close the bypass switch QF0, disconnect the switch QF1 and the switch QF2, and complete the load transfer.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention adopts a unique combined architecture of a transformer T1 with multi-winding and multi-asymmetric tap design, a multi-tap transformer T2, and multi-bridge-arm thyristor power valve groups on the parallel side and the series side. By intelligently selecting specific windings from the three-phase secondary windings of the transformer T1, a controllable voltage vector is synthesized through the parallel power valve string, and then through the dynamic turns ratio adjustment of the power valve of the transformer T2, the compensation voltage is coupled to the line to achieve power flow regulation. This innovative design of the coordinated adjustment of the two transformers and two power valve groups enables the number of synthesized vectors to reach four times that of the single parallel adjustment, forming a denser adjustment gear distribution. This innovative series-parallel coordinated adjustment mode of the present invention not only breaks through the problems of high equipment cost, large loss, and low reliability in the existing distribution network, and the new equipment such as phase-shifting transformers and SEN transformers face the problem of insufficient adjustment accuracy, but also has excellent compatibility and adaptability.

[0017] Further or more detailed beneficial effects will be described in combination with specific embodiments in the specific implementation manners. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts; Figure 1 is a schematic structural diagram of the flexible loop closing device according to the embodiment of the present invention; Figure 2 is a schematic diagram of the control and protection system of the flexible loop closing device according to the embodiment of the present invention; Figure 3 is a schematic structural diagram of a single parallel-transformer power valve in the parallel-transformer power valve group according to the embodiment of the present invention; Figure 4 is a schematic structural diagram of a single series-transformer power valve in the series-transformer power valve group according to the embodiment of the present invention; Figure 5 is a schematic diagram of the synthesized vector of the flexible loop closing device according to the embodiment of the present invention. Detailed implementation manners

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0020] In the following description, multiple embodiments of the present invention are provided. Replacements or combinations can be made between different embodiments. Therefore, the present invention can also be considered to include all possible combinations of the same and / or different embodiments described. Thus, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then the present invention should also be considered to include embodiments including one or more all other possible combinations of A, B, C, and D, although such embodiments may not be explicitly described in the following content.

[0021] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes can be made to the functions and arrangements of the described elements without departing from the scope of the content of the present invention. Each example can appropriately omit, substitute, or add various processes or components. For example, the described method can be executed in a different order from the described order, and various steps can be added, omitted, or combined. In addition, the features described in some examples can be combined into other examples.

[0022] To facilitate a better understanding of the embodiments of the present invention, before explaining the specific implementation manners of the present invention in detail, its application scenarios will be described first.

[0023] The flexible loop closing device described in the embodiments of this specification is applied to the process of flexible networking of the distribution network and new energy consumption. In these scenarios, the application of the flexible loop closing device aims to reduce the system operation risk, improve the new energy consumption capacity, improve the equipment utilization rate, improve the power flow mutual aid ability between lines, enhance the power supply reliability, and optimize the economic operation of the power grid.

[0024] Embodiment 1: As Figure 1As shown in the figure, this embodiment provides a flexible loop closing device based on series-parallel collaborative regulation. The flexible loop closing device is provided with a main circuit for obtaining energy from a parallel transformer, selecting a parallel secondary winding participating in synthesizing a compensation voltage, recombining the obtained secondary winding voltages, and then inserting a compensation voltage into the line through a series transformer to achieve flexible loop closing and power flow regulation. It consists of a parallel transformer T1, a series transformer T2, a parallel transformer power valve group, a series transformer power valve group, an incoming line 1 switch QF1, an incoming line 2 switch QF2, a bypass switch QF0, an incoming line 1 voltage collector PT1, an incoming line 2 voltage collector PT2, an incoming line 1 current collector CT1, and an incoming line 2 current collector CT2. The incoming line 1 voltage collector PT1, the incoming line 2 voltage collector PT2, the incoming line 1 current collector CT1, and the incoming line 2 current collector CT2 are used to calculate the voltage difference and real-time power on both sides of the device.

[0025] More specifically, the energy acquisition method of the flexible loop closing device is one main and one standby, that is, the main power source is the energy acquisition winding of the parallel transformer, and the standby power source is the 380V mains power. A dual-power switching switch ATS is used for main and standby power source switching. The main power source is the default power source. When the main power source is powered, the main power source supplies power to the secondary equipment. When the main power source has no power, it switches to the standby power source to supply power to the secondary equipment. In addition, the energy acquisition windings of the two incoming line PTs are mutually standby to supply power to the switch cabinet. When incoming line 1 is powered, the PT of incoming line 1 is used for power supply. When incoming line 1 has no power, the PT of incoming line 2 is used for power supply.

[0026] The flexible loop closing device further includes a main circuit, which is connected in parallel between incoming line 1 and incoming line 2 and is used to bypass the main circuit to achieve load transfer in the case of planned power outage transfer or when one side power source loses power due to a fault.

[0027] The flexible loop closing device further includes data acquisition equipment for monitoring the voltage parameters and current parameters of the bypass circuit to obtain voltage signals and current signals.

[0028] As Figure 2 shown, the flexible loop closing device further includes a control and protection system for real-time monitoring of the working states and switch positions of the parallel transformer T1, the series transformer T2, the parallel transformer power valve group, and the series transformer power valve group, receiving the voltage signals and current signals from the data acquisition equipment, calculating the voltage difference between incoming line 1 and incoming line 2 and the real-time power of incoming line 1 and incoming line 2, and according to the regulation commands of the monitoring background or dispatching, adjusting the working states of the power valves in the parallel transformer power valve group and the series transformer power valve group in real time through control protection algorithms to achieve the control and protection functions of the device. More specifically, the control protection algorithms can at least include control algorithms such as flexible loop closing algorithms, power flow transfer algorithms, and load transfer algorithms.

[0029] The parallel transformer T1 is a multi-winding and multi-asymmetric tap transformer. Each phase has three asymmetric secondary windings, and there are a total of 9 asymmetric windings in three phases. The voltage ratio of the asymmetric windings is 1:2. There are 9 independent power valves in the parallel power valve group, which correspond one-to-one to the secondary asymmetric windings of the parallel transformer. The structure of each independent power valve is as Figure 3 shown. The three taps of the asymmetric winding are connected to the three inputs of the independent power valve. By controlling the on / off of the thyristors in the independent power valve, different windings in the secondary asymmetric winding of the parallel transformer can be selected. One independent power valve corresponding to the secondary winding of the parallel transformer is taken from each of the A / B / C phases and connected in series to synthesize a voltage vector.

[0030] The series transformer is a multi-asymmetric tap transformer with a total of 5 taps, corresponding to 5 turns ratios of 2:1, 1.9:1, 1.75:1, 1.5:1, and 1:1 respectively. The structure of each series transformer power valve is as Figure 4 shown. There are a total of 5 bridge arms. The five input terminals are respectively connected to the five taps on the secondary side of the series transformer, and the two output terminals are respectively connected to the two output terminals after three independent power valves are connected in series. By controlling the different on / off of the thyristors in the series transformer power valve and selecting different turns ratios of the series transformer, the synthesized voltage vector output by the parallel power valve group can be coupled into the line according to a certain turns ratio relationship to compensate a voltage on the primary line, realizing flexible loop closing and power transfer between the two incoming lines. Through the coordinated regulation of the parallel transformer and the series transformer, the number of synthesized vectors is 4 times that of the synthesized vectors regulated by the power valves on the parallel side alone. The synthesized vectors are as Figure 5 shown, and the gear positions are denser, so the adjustment range of the device is larger and the adjustment accuracy is higher.

[0031] The real-time regulation of the flexible loop closing algorithm by the control and protection system includes the following steps: First step, the control and protection system closes QF1; Second step, collect data and calculate the voltage difference between PT1 voltage of incoming line 1 and PT2 voltage of incoming line 2; Third step, calculate the gear positions of the parallel power valve and the series power valve corresponding to the voltage to be compensated based on the voltage difference obtained in the second step; Fourth step, unlock the parallel power valve to synthesize the voltage vector; Fifth step, unlock the series power valve, and the synthesized voltage vector is coupled into the line according to a certain turns ratio; Sixth step, close switch QF2 to complete flexible loop closing and enter the loop closing operation mode.

[0032] The real-time adjustment of the power flow transfer algorithm by the control and protection system includes the following steps: when a power flow transfer instruction is received, in the first step, determine the direction of power flow transfer (including active and reactive power); in the second step, determine the next vector point according to the direction of power flow transfer from the current vector point, and change the on / off sequence of thyristors in the shunt power valve to complete the gear adjustment on the shunt side; in the third step, determine the adjustment gear of the series power valve according to the magnitude of power flow transfer, and change the on / off sequence of thyristors in the series power valve to move the operating point to the next vector point; in the fourth step, then judge the power flow difference and direction between the current power flow value and the instruction value. If the power flow instruction value is not reached, repeat the first to the third steps until the error between the current power flow value and the instruction value is within the allowable range. In addition, it should be noted that since the flexible loop closing device in this embodiment contains two transformers, during power flow adjustment, each time the gear is changed, due to the zero-crossing turn-off characteristic of the thyristors, in order to avoid causing circulating current, it is necessary to wait for the thyristors that were turned on last time to be completely turned off before new thyristors can be turned on. Then, during this process, it is equivalent to the transformer being re-energized, and inrush current will be generated. For this problem, the control strategy adopted in this embodiment is to lengthen the time interval between two gear adjustments, and wait until the inrush current generated during the previous gear adjustment has completely recovered before re-energizing the new gear.

[0033] The real-time adjustment of the load transfer control algorithm by the control and protection system includes the following steps: when the device is operating in the loop closing mode and needs to switch to the load transfer mode, in the first step, lock the shunt power valve; in the second step, adjust the series transformer power valve to the 0 gear; in the third step, close the switch QF0; in the fourth step, open the switches QF1 and QF2 to achieve load transfer.

[0034] It should be noted that for the foregoing method embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0035] In the above embodiments, the descriptions of each embodiment have their own emphases. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0036] The above are only exemplary embodiments of the present invention and should not be used to limit the scope of the present invention. That is, any equivalent changes and modifications made in accordance with the teachings of the present invention still fall within the scope covered by the present invention. Those skilled in the art will readily think of other embodiments of the present invention after considering the specification and practicing the disclosure herein. The present invention is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the present invention and include common general knowledge or conventional technical means in the technical field not recorded in the present invention. The specification and embodiments are only regarded as exemplary, and the scope and spirit of the present invention are defined by the claims.

Claims

1. A flexible loop closing device based on series-parallel collaborative regulation, characterized in that, It includes a main circuit, a bypass circuit, a data acquisition device, and a control and protection system: The main circuit is used to obtain energy from parallel transformers, select the parallel secondary windings participating in the synthesis of the compensation voltage, recombine the obtained secondary winding voltages, and inject a compensation voltage into the line through a series transformer to achieve flexible loop closing and power flow regulation; The bypass circuit is connected in parallel between incoming line 1 and incoming line 2 and is used to bypass the main circuit in the case of planned power-off transfer or when one power source loses power due to a fault to achieve load transfer; The data acquisition device is used to monitor the voltage parameters and current parameters of the bypass circuit to obtain voltage signals and current signals; The control and protection system is used to calculate the real-time power of the voltage difference of the bypass circuit according to the received voltage signals and current signals, and adjust the working states of the parallel transformer power valve group and the series transformer power valve group in the main circuit in real time, as well as control the protection algorithm.

2. The flexible loop closing device based on series-parallel coordinated regulation according to claim 1, characterized in that: The main circuit includes a parallel transformer T1, a parallel transformer power valve group, a series transformer power valve group, and a series transformer T2 connected in sequence; The input end of the primary winding of the parallel transformer T1 is connected to incoming line 1, and the output ends of the primary windings are star-connected to form a neutral point; The parallel transformer T1 is a multi-winding and multi-asymmetric tap transformer, its primary winding is connected in parallel to the primary circuit, and multiple taps of each secondary winding are respectively connected to different input ends of the parallel transformer power valve group; The series transformer T2 is a multi-asymmetric tap transformer, its primary side is connected in series to the main circuit, and its secondary side is connected to different input ends of the series transformer power valve group; The parallel transformer power valve group is used to select different taps of different secondary windings and combine them to generate an adjustable synthetic voltage vector; The series transformer power valve group is used to select different taps of the series transformer T2 and couple the synthetic voltage vector to the main circuit.

3. The flexible loop closing device based on series-parallel coordinated regulation according to claim 2, characterized in that: Each phase of the parallel transformer T1 is provided with three asymmetric secondary windings, with a total of nine windings in three phases, and the voltage ratio of the asymmetric secondary windings is 1:

2.

4. The flexible loop closing device based on series-parallel coordinated regulation according to claim 3, characterized in that: The series transformer T2 is provided with five taps, and the turns ratios of the five taps are 2:1, 1.9:1, 1.75:1, 1.5:1, and 1:1 respectively.

5. The flexible loop closing device based on series-parallel coordinated regulation according to claim 4, characterized in that: The parallel transformer power valve group includes multiple bridge arms, each bridge arm includes a group of thyristor valves, and the three inputs of each thyristor valve are respectively connected to the three taps of a secondary winding of the parallel transformer T1, and the winding combination is selected by controlling the on-off of the thyristors.

6. The flexible loop closing device based on series-parallel coordinated regulation according to claim 5, characterized in that: The inputs of the series variable power valve group are respectively connected to the taps of the secondary winding of the series transformer T2, and the output terminals of the series variable power valve group are connected to the output after three power valves in the parallel power valve group are connected in series; The series variable power valve group includes multiple bridge arms, each bridge arm includes a group of thyristor valves, and the five inputs of each power valve group are correspondingly connected to the five taps of the series transformer T2. The turns ratio of the series transformer T2 is selected by controlling the on / off of the thyristors in the bridge arm.

7. The flexible closed-loop device based on series-parallel collaborative regulation according to claim 6, wherein: Switch QF1 and switch QF2 are respectively arranged on the incoming line 1 and the incoming line 2; Bypass switch QF0 is arranged in the bypass circuit; The data acquisition device includes a voltage transformer PT1 and a current transformer CT1 arranged on the incoming line 1, and a voltage transformer PT2 and a current transformer CT2 arranged on the incoming line 2.

8. A flexible loop closing device based on series-parallel collaborative regulation according to claim 7, characterized in that, The control and protection algorithm for real-time adjustment by the control and protection system includes a flexible closed-loop algorithm. The steps of the control and protection system for real-time adjustment of the flexible closed-loop algorithm are as follows: Close switch QF1, start the data acquisition device to collect data and calculate the voltage difference between the two sides of the incoming line 1 and the incoming line 2; Based on the voltage difference, determine the corresponding parallel power valve gear and series power valve gear; Unlock the variable power valve and generate a synthetic voltage vector; Unlock the series variable power valve, adjust the accuracy, and couple the synthetic voltage vector to the main circuit; Close switch QF2 to complete the flexible closed loop and enter the closed-loop operation mode.

9. A flexible loop closing device based on series-parallel collaborative regulation according to claim 7, characterized in that The control and protection algorithm for real-time adjustment by the control and protection system further includes a power flow transfer algorithm. The steps of the control and protection system for real-time adjustment of the power flow transfer algorithm are as follows: Based on the received power flow transfer instruction, determine the power flow direction and the power flow target value; Adjust the parallel power valve group to select the corresponding winding combination; Adjust the turns ratio and accuracy of the series variable power valve group; Judge whether the power flow error is within the allowable range. If not, repeat the above steps to gradually approach the power flow target value until the power flow error is within the allowable range.

10. A flexible loop closing device based on series-parallel collaborative regulation according to claim 7, characterized in that, The control and protection algorithm for real-time adjustment by the control and protection system further includes a load transfer control algorithm. The steps of the control and protection system for real-time adjustment of the load transfer control algorithm are as follows: Lock the parallel power valve group and adjust the series variable power valve group to the 0th gear; Close the bypass switch QF0, disconnect switch QF1 and switch QF2 to complete the load transfer.

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