Voltage support method and system of reality test platform PCS under asymmetric fault

Abstract

The invention discloses a voltage support method and system for a PCS (Personal Computer System) under an asymmetric fault. The method comprises the following steps: acquiring circuit parameter information of the PCS under the asymmetric fault, and carrying out first preprocessing on the circuit parameter information; presetting a first voltage support strategy, calculating the maximum value and the minimum value of the voltage amplitude of the grid-connected point of the reality test platform and the negative sequence voltage amplitude of the power grid according to the first voltage support strategy, and obtaining positive and negative sequence active current reference values and reactive current reference values; and combining the positive and negative sequence active current reference values and the reactive current reference values into a current reference value under an alpha-beta coordinate system, subtracting the current reference value from the output current of a real test platform PCS, obtaining a modulation signal through a proportional resonance controller, and generating a switching signal through SVPWM (Space Vector Pulse Width Modulation) to act on the energy storage converter PCS. By accurately controlling the positive and negative sequence components of the PCS output current, the negative sequence voltage in the power grid can be effectively suppressed, so that the influence of asymmetric faults on the power grid is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of voltage support for a real-life test platform PCS, and in particular to a voltage support method and system for a real-life test platform PCS under an asymmetric fault. Background Art

[0002] With the growing demand for the construction of new power systems and pilot service bases, the large-scale grid connection of distributed new energy and the widespread application of power electronic equipment, new distribution networks are facing new challenges in power quality management. In order to achieve the goal of high-quality power supply for new distribution networks, experimental verification of advanced power quality management technologies and equipment is urgently needed. The advanced distribution network real-life test platform built by Guangxi Power Grid Company can provide a testing and experimental environment for the promotion and application of new technologies, new equipment and new methods in distribution networks. With the construction of the second phase of the real-life test platform, distributed photovoltaics, energy storage equipment, electric vehicle charging piles and other clusters are connected, and it has the ability to reproduce the distribution network operating environment with typical new power system characteristics. The real-life test platform needs to simulate common faults of the distribution network at the test station, and asymmetric faults are the most common faults in the power grid, which will cause adverse effects such as voltage drop at the grid connection point and power fluctuation on the AC and DC sides, thereby affecting the testing of other test stations.

[0003] Therefore, a voltage support strategy for the PCS of the real test platform under asymmetric faults is proposed, which fills the gap in the real test platform for energy storage converter testing and is conducive to improving the distribution network fault simulation capability of the real test platform. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above existing problems, the present invention is proposed.

[0006] Therefore, the present invention provides a voltage support method and system for a real-life test platform PCS under an asymmetric fault, which can solve the problems mentioned in the background technology.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] In a first aspect, the present invention provides a voltage support method for a real-life test platform PCS under an asymmetric fault, comprising:

[0009] Acquire circuit parameter information of a real-life test platform PCS asymmetric fault, and perform a first preprocessing on the circuit parameter information;

[0010] Wherein, the circuit parameter information includes grid voltage, output current, line inductance and line resistance;

[0011] The first preprocessing includes obtaining the grid voltage and output current in the αβ coordinate system through Clark transformation, and then performing positive and negative sequence separation on the grid voltage in the αβ coordinate system to obtain the grid positive sequence voltage amplitude, grid negative sequence voltage amplitude and grid positive and negative sequence voltage phase angle difference, and obtaining the positive sequence component amplitude and negative sequence component amplitude of the output current of the PCS of the real test platform, as well as the maximum and minimum values ​​of the voltage amplitude of the grid connection point of the real test platform;

[0012] A first voltage support strategy is preset, and the maximum and minimum voltage amplitudes of the grid connection points of the actual test platform and the negative sequence voltage amplitude of the power grid are calculated according to the first voltage support strategy to obtain positive and negative sequence active current reference values ​​and reactive current reference values;

[0013] The positive and negative sequence active current reference values ​​and reactive current reference values ​​are combined into a current reference value in the αβ coordinate system, and the value is subtracted from the output current of the actual test platform PCS. A modulation signal is obtained through a proportional resonant controller, and then a switching signal is generated through SVPWM to act on the energy storage converter PCS.

[0014] As a preferred solution of the voltage support method of the real-life test platform PCS under asymmetric faults described in the present invention, the first preprocessing further includes:

[0015] The grid voltage in the αβ coordinate system is separated into positive and negative sequences to obtain the grid positive sequence voltage amplitude, grid negative sequence voltage amplitude and grid positive and negative sequence voltage phase angle difference, and the positive sequence component amplitude and negative sequence component amplitude of the output current of the real test platform PCS are obtained;

[0016] Among them, the positive sequence component amplitude and negative sequence component amplitude of the PCS output current of the real test platform are expressed as:

[0017]

[0018] Among them, I max Indicates the maximum value among the three-phase current amplitudes; I + and I - They represent the amplitudes of the positive-sequence and negative-sequence components of the PCS output current of the real-world test platform respectively; and They respectively represent the amplitudes of the positive sequence active component and reactive component of the PCS output current of the real test platform; and They represent the amplitudes of the negative sequence active component and reactive component of the PCS output current of the real test platform respectively; atan2(*,*) is the four-quadrant inverse tangent function, θ+ and θ - They represent the initial phases of the positive-sequence component and the negative-sequence component of the grid-connected point voltage of the actual test platform respectively, and φ represents the phase angle difference between the positive-sequence and negative-sequence currents of the power grid.

[0019] As a preferred solution of the voltage support method of the real-life test platform PCS under asymmetric faults described in the present invention, the first preprocessing further includes:

[0020] The grid voltage in the αβ coordinate system is separated into positive and negative sequences to obtain the grid positive sequence voltage amplitude, grid negative sequence voltage amplitude and grid positive and negative sequence voltage phase angle difference;

[0021] Among them, the expression of the positive and negative sequence voltage amplitude of the grid connection point of the real test platform is:

[0022]

[0023] Among them, U + and U-represent the amplitudes of the positive-sequence component and negative-sequence component of the grid-connected point voltage of the actual test platform, respectively; ω represents the angular frequency of the fundamental wave component of the grid of the actual test platform, Indicates the positive sequence voltage amplitude of the power grid, Represents the negative sequence voltage amplitude of the power grid, R g Indicates line resistance. L g Indicates line inductance.

[0024] As a preferred solution of the voltage support method of the real-life test platform PCS under asymmetric faults described in the present invention, the first preprocessing further includes:

[0025] The grid voltage and output current are transformed by Clark to obtain the grid voltage and the output current of the PCS in the αβ coordinate system, and then the grid voltage in the αβ coordinate system is separated into positive and negative sequences to obtain the grid positive sequence voltage amplitude, grid negative sequence voltage amplitude and grid positive and negative sequence voltage phase angle difference, and the positive sequence component amplitude and negative sequence component amplitude of the output current of the PCS in the real test platform, as well as the maximum and minimum values ​​of the voltage amplitude at the grid connection point of the real test platform;

[0026] Among them, the expression of the voltage amplitude of the grid connection point of the actual test platform is as follows:

[0027]

[0028] Among them, U max and U min Respectively represent the maximum and minimum values ​​of the three-phase voltage amplitude; θ + and θ - They respectively represent the initial phases of the positive-sequence component and the negative-sequence component of the grid-connected point voltage on the actual test platform.

[0029] As a preferred solution of the voltage support method of the real test platform PCS under asymmetric faults described in the present invention, the preset first voltage support strategy includes: if and only if the grid connection point voltage of the real test platform meets 0.9U N ~1.1U N When PCS can run continuously, U N is the rated voltage of the power grid of the actual test platform.

[0030] As a preferred solution of the voltage support method of the real-life test platform PCS under asymmetric faults described in the present invention, the preset first voltage support strategy also includes: assuming that the positive sequence current amplitude allowed to be output is The goal is to maximize the positive sequence voltage support. As the constraint condition, the first Lagrangian function is constructed, assuming that the allowed output negative sequence current is The goal is to maximize the suppression of negative sequence voltage. As the constraint condition, the second Lagrangian function is constructed.

[0031] As a preferred solution of the voltage support method of the real-life test platform PCS under asymmetric faults described in the present invention, the preset first voltage support strategy also includes:

[0032] According to the first Lagrangian function and the second Lagrangian function, an optimal ratio 1 of the amplitude of the positive-sequence active component and the reactive component of the output current of the real-life test platform PCS, and an optimal ratio 2 of the amplitude of the negative-sequence active component and the reactive component of the output current of the real-life test platform PCS are obtained;

[0033] Obtaining positive and negative sequence voltage values ​​of the grid connection point of the actual test platform according to the optimal ratio one and the optimal ratio two;

[0034] According to the positive and negative sequence voltage values ​​of the grid connection point of the actual test platform, the grid connection point voltage of 0.9U is calculated to meet the actual test platform. N ~1.1U N The positive and negative sequence active current reference value and reactive current reference value under the constraint of .

[0035] In a second aspect, the present invention provides a voltage support system for a real-life test platform PCS under an asymmetric fault, comprising:

[0036] A data acquisition module, used to acquire circuit parameter information under a PCS asymmetric fault of a real-life test platform, and perform a first preprocessing on the circuit parameter information;

[0037] Wherein, the circuit parameter information includes grid voltage, output current, line inductance and line resistance;

[0038] The first preprocessing includes obtaining the grid voltage and output current in the αβ coordinate system through Clark transformation, and obtaining the grid voltage and output current of the real test platform PCS in the αβ coordinate system, and then performing positive and negative sequence separation on the grid voltage in the αβ coordinate system to obtain the grid positive sequence voltage amplitude, grid negative sequence voltage amplitude and grid positive and negative sequence voltage phase angle difference, and obtaining the positive sequence component amplitude and negative sequence component amplitude of the output current of the real test platform PCS, as well as the maximum and minimum values ​​of the voltage amplitude of the grid connection point of the real test platform;

[0039] A support strategy calculation module is used to preset a first voltage support strategy, calculate the maximum and minimum voltage amplitudes of the grid connection point of the actual test platform and the negative sequence voltage amplitude of the power grid according to the first voltage support strategy, and obtain positive and negative sequence active current reference values ​​and reactive current reference values;

[0040] The modulation module is used to combine the positive and negative sequence active current reference values ​​and reactive current reference values ​​into a current reference value in the αβ coordinate system, and to make a difference with the output current of the actual test platform PCS, to obtain a modulation signal through a proportional resonant controller, and then to generate a switching signal through SVPWM to act on the energy storage converter PCS.

[0041] In a third aspect, the present invention provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above-mentioned method when executing the computer program.

[0042] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program implements the steps of the method described above when executed by a processor.

[0043] Compared with the prior art, the present invention has the following beneficial effects: the present invention proposes a voltage support method and system for a real-life test platform PCS under an asymmetric fault, obtains circuit parameter information under an asymmetric fault of the real-life test platform PCS, and performs a first preprocessing on the circuit parameter information; a first voltage support strategy is preset, and the maximum and minimum voltage amplitudes of the real-life test platform grid-connected points and the negative-sequence voltage amplitude of the power grid are calculated according to the first voltage support strategy to obtain positive and negative sequence active current reference values ​​and reactive current reference values; the positive and negative sequence active current reference values ​​and reactive current reference values ​​are combined into current reference values ​​in the αβ coordinate system, and the difference is made with the output current of the real-life test platform PCS, a modulation signal is obtained through a proportional resonant controller, and then a switching signal is generated through SVPWM to act on the energy storage converter PCS. The voltage support method and system for the real-life test platform PCS under an asymmetric fault of the present invention can effectively improve the stability and reliability of the power grid. By accurately controlling the positive and negative sequence components of the PCS output current, the present invention can effectively suppress the negative sequence voltage in the power grid, thereby reducing the impact of asymmetric faults on the power grid. In addition, the present invention can also dynamically adjust the output current of the PCS according to the actual operation of the power grid to adapt to the real-time needs of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0045] Figure 1 A method flow chart of a voltage support method and system for a real-life test platform PCS under an asymmetric fault provided by an embodiment of the present invention;

[0046] Figure 2 A voltage support method and system of a real-life test platform PCS under asymmetric faults provided by an embodiment of the present invention is a real-life test platform system control strategy structure diagram;

[0047] Figure 3 A voltage diagram of a grid connection point of a real-life test platform of a voltage support method and system for a real-life test platform PCS under an asymmetric fault provided by an embodiment of the present invention;

[0048] Figure 4 A diagram of the output current of a PCS of a real test platform under an asymmetric fault according to a voltage support method and system of the PCS of a real test platform provided by an embodiment of the present invention;

[0049] Figure 5An internal structural diagram of a computer device of a voltage support method and system for a real-life test platform PCS under asymmetric faults provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0050] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0051] Example 1

[0052] Reference Figure 1-Figure 5 , which is the first embodiment of the present invention, and provides a voltage support method and system for a real-life test platform PCS under an asymmetric fault, including:

[0053] Before describing the embodiments of the present application in detail, some related concepts are first explained for the sake of clarity.

[0054] PCS: PCS (Power Conversion System) usually refers to a power conversion system, which is a device or a group of devices used to convert one form of energy into another form of energy. In the field of renewable energy, PCS usually refers to the bidirectional converter in the energy storage system, which can convert direct current (DC) to alternating current (AC), or convert AC to DC, in order to store energy or supply power to the grid. In this context, PCS specifically refers to the energy storage converter used in the real test platform.

[0055] Voltage support strategy: Voltage support strategy refers to a series of measures taken in the power system to maintain the grid voltage within a safe range. This strategy is particularly important because in the event of a grid failure or other abnormal conditions, the voltage may drop or fluctuate, thus affecting the stability and reliability of the system. The voltage support strategy can be implemented by adjusting the reactive power output of the generator set, using static VAR compensators (SVCs), static synchronous compensators (STATCOMs) and other devices. In the above context, the voltage support strategy involves how to maintain the stability of the grid connection point voltage by controlling the output current of the PCS.

[0056] Real-world testbed: A real-world testbed is a test facility used to simulate the actual operating environment, where equipment or technology can be tested and verified without interfering with the actual production environment or power grid. Real-world testbeds are usually equipped with various sensors and measuring instruments to accurately collect data and analyze equipment performance. For power electronic equipment, real-world testbeds provide a safe and controllable environment to conduct tests under various operating conditions, such as normal operation, performance of equipment under fault conditions, etc.

[0057] Asymmetric fault: Asymmetric fault refers to one of the types of faults that occur in the power system, which causes the three phases of the system to no longer be balanced. Common asymmetric faults include single-phase ground short circuit, two-phase short circuit, two-phase ground short circuit, etc. During these faults, positive sequence components, negative sequence components, and zero sequence components (if any) in the power grid will appear, while a normal power system only has positive sequence components. Asymmetric faults can affect the stability and power supply quality of the power system, so appropriate protection measures and technical means are needed to mitigate their impact.

[0058] There are some limitations and deficiencies in the related technologies. For example, under asymmetric fault conditions, the traditional voltage support method may not be able to effectively handle the negative sequence voltage problem, resulting in reduced grid stability. In addition, due to the lack of real-time adjustment capabilities, the traditional method may not be able to respond in time when the grid operating conditions change, thus affecting the performance of the entire system.

[0059] The present application provides a method that can effectively solve the above-mentioned problems. Next, a voltage support method for the real-life test platform PCS under asymmetric faults will be described in detail in combination with multiple embodiments.

[0060] Figure 1 A method flow chart of a voltage support method and system of a real-life test platform PCS under an asymmetric fault is shown, including:

[0061] S101, obtaining circuit parameter information of a real-life test platform PCS asymmetric fault, and performing a first preprocessing on the circuit parameter information;

[0062] Among them, the circuit parameter information includes grid voltage, output current, line inductance and line resistance;

[0063] In the embodiment of the present application, the first preprocessing includes obtaining the grid voltage and the output current in the αβ coordinate system through Clark transformation, and then performing positive and negative sequence separation on the grid voltage in the αβ coordinate system to obtain the grid positive sequence voltage amplitude, the grid negative sequence voltage amplitude and the grid positive and negative sequence voltage phase angle difference, and obtaining the positive sequence component amplitude and negative sequence component amplitude of the output current of the PCS of the real test platform, as well as the maximum and minimum values ​​of the voltage amplitude of the grid connection point of the real test platform;

[0064] In the embodiment of the present application, the first preprocessing further includes:

[0065] The grid voltage in the αβ coordinate system is separated into positive and negative sequences to obtain the grid positive sequence voltage amplitude, grid negative sequence voltage amplitude and grid positive and negative sequence voltage phase angle difference, and the positive sequence component amplitude and negative sequence component amplitude of the output current of the real test platform PCS are obtained;

[0066] In the embodiment of the present application, it is determined to obtain the grid voltage u under the asymmetric fault of the actual test platform gabc , output current i abc and line inductance L g and line resistance R g , will u gabc 、i abc The grid voltage u in the αβ coordinate system is obtained by Clark transformation gαβ 、Real-world test platform PCS output current i αβ , and then u gαβ Separate the positive and negative sequences to obtain the positive sequence voltage amplitude of the power grid Negative sequence voltage amplitude of power grid The phase angle difference between the positive and negative sequence voltages of the power grid And the positive sequence component amplitude I of the PCS output current of the actual test platform is obtained + and the negative sequence component amplitude I - , and the maximum voltage amplitude U of the grid connection point of the actual test platform max and the minimum value U min .

[0067] Among them, the positive sequence component amplitude and negative sequence component amplitude of the PCS output current of the real test platform are expressed as:

[0068]

[0069] Among them, I max Indicates the maximum value among the three-phase current amplitudes; I + and I - They represent the amplitudes of the positive-sequence and negative-sequence components of the PCS output current of the real-world test platform respectively; and They respectively represent the amplitudes of the positive sequence active component and reactive component of the PCS output current of the real test platform; and They represent the amplitudes of the negative sequence active component and reactive component of the PCS output current of the real test platform respectively; atan2(*,*) is the four-quadrant inverse tangent function, θ + and θ - They represent the initial phases of the positive-sequence component and the negative-sequence component of the grid-connected point voltage of the actual test platform respectively, and φ represents the phase angle difference between the positive-sequence and negative-sequence currents of the power grid.

[0070] In the embodiment of the present application, the first preprocessing further includes:

[0071] The grid voltage in the αβ coordinate system is separated into positive and negative sequences to obtain the grid positive sequence voltage amplitude, grid negative sequence voltage amplitude and grid positive and negative sequence voltage phase angle difference;

[0072] Among them, the expression of the positive and negative sequence voltage amplitude of the grid connection point of the real test platform is:

[0073]

[0074] Among them, U + and U - They represent the amplitudes of the positive-sequence component and the negative-sequence component of the grid-connected point voltage of the actual test platform respectively; ω represents the angular frequency of the fundamental wave component of the grid of the actual test platform, Indicates the positive sequence voltage amplitude of the power grid, Represents the negative sequence voltage amplitude of the power grid, R g Indicates line resistance. L g Indicates line inductance.

[0075] In the embodiment of the present application, the first preprocessing further includes:

[0076] The grid voltage and output current are transformed by Clark to obtain the grid voltage and the output current of the PCS in the αβ coordinate system, and then the grid voltage in the αβ coordinate system is separated into positive and negative sequences to obtain the grid positive sequence voltage amplitude, grid negative sequence voltage amplitude and grid positive and negative sequence voltage phase angle difference, and the positive sequence component amplitude and negative sequence component amplitude of the output current of the PCS in the real test platform, as well as the maximum and minimum values ​​of the voltage amplitude at the grid connection point of the real test platform;

[0077] Among them, the expression of the voltage amplitude of the grid connection point of the actual test platform is as follows:

[0078]

[0079] Among them, U max and U min Respectively represent the maximum and minimum values ​​of the three-phase voltage amplitude; θ + and θ - They respectively represent the initial phases of the positive-sequence component and the negative-sequence component of the grid-connected point voltage on the actual test platform.

[0080] It should be noted that the benefit of the above step S101 is that it can accurately obtain and analyze the grid voltage and current characteristics of the real test platform under asymmetric fault conditions. By performing Clark transformation on the grid voltage and output current and separating the positive and negative sequence components, asymmetric faults in the grid can be more accurately identified and evaluated, thereby providing strong technical support for the stable operation of the grid.

[0081] S102, presetting a first voltage support strategy, calculating the maximum and minimum voltage amplitudes of the grid connection point of the actual test platform and the negative sequence voltage amplitude of the power grid according to the first voltage support strategy, and obtaining positive and negative sequence active current reference values ​​and reactive current reference values;

[0082] In the embodiment of the present application, the preset first voltage support strategy includes: if and only if the grid voltage of the actual test platform meets 0.9U N ~1.1U N When PCS can run continuously, U N is the rated voltage of the power grid of the actual test platform.

[0083] In the embodiment of the present application, the preset first voltage support strategy also includes: assuming that the positive sequence current amplitude allowed to be output is The goal is to maximize the positive sequence voltage support. As the constraint condition, the first Lagrangian function is constructed, assuming that the allowed output negative sequence current is The goal is to maximize the suppression of negative sequence voltage. As the constraint condition, the second Lagrangian function is constructed.

[0084] In the embodiment of the present application, the preset first voltage support strategy also includes:

[0085] According to the first Lagrangian function and the second Lagrangian function, an optimal ratio 1 of the amplitude of the positive-sequence active component and the reactive component of the output current of the real-life test platform PCS, and an optimal ratio 2 of the amplitude of the negative-sequence active component and the reactive component of the output current of the real-life test platform PCS are obtained;

[0086] According to the optimal ratio 1 and the optimal ratio 2, the positive and negative sequence voltage values ​​of the grid connection point of the actual test platform are obtained;

[0087] According to the positive and negative sequence voltage values ​​of the grid connection point of the actual test platform, the grid connection point voltage of 0.9U is calculated to meet the actual test platform. N ~1.1U N The positive and negative sequence active current reference value and reactive current reference value under the constraint of .

[0088] In the embodiment of the present application, the grid connection voltage of the actual test platform meets 0.9U N ~1.1U NWhen the PCS is running continuously. max =1.1U N and Substituting into the grid connection point voltage amplitude expression, the positive sequence voltage reference value can be obtained and negative sequence voltage reference for:

[0089]

[0090] Among them, UN is the rated voltage of the actual test platform power grid.

[0091] Will get Substituting the grid connection point voltage amplitude expression into the same way, we can get:

[0092]

[0093] Among them, U min1 express and The corresponding U min .

[0094] When U min1 <0.9U N When U max =1.1U N and U min =0.9U N Substituting the voltage amplitude expression of the grid connection point of the actual test platform into the calculation, the positive sequence voltage reference value can be obtained and negative sequence voltage reference for:

[0095]

[0096] Reasonable distribution of active current and reactive current ratio can better support the PCC voltage of the real test platform. Assuming that the output positive sequence current amplitude is allowed to be The goal is to maximize the positive sequence voltage support. As the constraint condition, the first Lagrangian function L1 is constructed as:

[0097]

[0098] Among them, λ1 is the multiplication factor of L1.

[0099] right Ask about And the first-order partial derivative of λ1, and set its first-order partial derivative equal to 0, we can get:

[0100]

[0101] The equation with the first-order partial derivative equal to zero can be solved to obtain and The optimal ratio is:

[0102]

[0103] Similarly, assuming that the allowed output negative sequence current is The goal is to maximize the suppression of negative sequence voltage. As the constraint condition, the second Lagrangian function L2 is constructed as:

[0104]

[0105] Formula: λ2 is the multiplication factor of L2.

[0106] Similarly, we can get and The optimal ratio of is:

[0107]

[0108] Will and The optimal ratio and and Substituting the optimal ratio into the expression of the positive and negative sequence voltage amplitude of the grid connection point of the actual test platform, the solution of the positive and negative sequence voltage of the grid connection point can be obtained as follows:

[0109]

[0110] Will Substituting into the expression of the positive and negative sequence voltage solution of the grid connection point of the actual test platform, we can get U min1 ≥0.9U N Supports grid voltage up to 0.9U N ~1.1U N The current reference value is:

[0111]

[0112] in, Indicates the positive sequence active current reference value; Indicates the positive sequence reactive current reference value; Indicates the negative sequence active current reference value; Indicates the negative sequence reactive current reference value.

[0113] Will Substituting into the expression of the positive and negative sequence voltage solution of the grid connection point, we can get U min1 <0.9U N Supports grid voltage up to 0.9U N ~1.1U NThe current reference value is:

[0114]

[0115] It should be noted that in practical applications, in order to ensure the stability of the grid-connected point voltage, other factors that may exist in the system need to be considered, such as voltage fluctuations, frequency changes, and dynamic characteristics of the load. Therefore, in addition to the calculated current reference value, a dynamic adjustment mechanism needs to be introduced to cope with the influence of these uncertain factors.

[0116] It should be noted that the benefit of the above step S102 is that it can provide a flexible and effective current control strategy to ensure that the voltage at the grid connection point fluctuates within a specified range. By reasonably allocating the ratio of active current to reactive current, the positive sequence voltage can be effectively supported and the negative sequence voltage can be suppressed, thereby improving the power quality of the entire real-world test platform.

[0117] In addition, the Lagrangian function constructed using the Lagrangian multiplier method can transform the optimization problem into an equation for solving the first-order partial derivative equal to zero, thereby obtaining the optimal ratio. This method is not only applicable to current distribution under static conditions, but can also be extended to dynamically changing systems to adapt to various changes in actual operation.

[0118] In an optional embodiment, the introduction of a dynamic adjustment mechanism can further improve the robustness of the system. For example, a PID controller can be used to adjust the current reference value in real time to cope with the impact of voltage fluctuations, frequency changes and load dynamic characteristics. By monitoring the real-time values ​​of the voltage and current at the grid connection point in real time, the PID controller can dynamically adjust the output of active and reactive currents to ensure that the voltage always fluctuates within the specified range.

[0119] In an optional embodiment, a predictive control strategy can also be introduced to predict possible fluctuations in the system in advance and adjust the current reference value in advance to avoid voltage fluctuations. The predictive control strategy can be implemented through a machine learning algorithm based on historical data and system models, thereby improving the prediction accuracy and control effect of the system.

[0120] In short, by reasonably allocating the ratio of active current to reactive current and introducing dynamic adjustment mechanism and predictive control strategy, the stability of the grid connection point voltage can be effectively supported and the power quality of the entire real-world test platform can be improved. This not only helps to improve the operating efficiency of the system, but also brings users a more stable and reliable power supply.

[0121] S103, the positive and negative sequence active current reference values ​​and reactive current reference values ​​are combined into a current reference value in the αβ coordinate system, and the difference is made with the output current of the actual test platform PCS, a modulation signal is obtained through a proportional resonant controller, and then a switching signal is generated through SVPWM to act on the energy storage converter PCS.

[0122] In the embodiment of the present application, the current reference value and Current reference value i in the synthetic αβ coordinate system αβref , and with i αβ The difference is passed through the proportional resonant controller to obtain the modulation signal, and then the switching signal is generated through SVPWM to act on the energy storage converter.

[0123] It should be noted that the current reference value obtained from the positive and negative sequence decomposition needs to be converted into a suitable coordinate system (such as dq or αβ coordinate system) first. This transformation is usually completed using Clarke transformation or Park transformation, the purpose is to simplify the design of the control algorithm, because in the rotating coordinate system, the quantity that originally changes with time can be converted into a DC quantity or a low-frequency quantity, which is easy to control. Error calculation: The transformed current reference value is subtracted from the actual detected current value to obtain an error signal. This step is to determine the deviation between the actual current and the expected current. Proportional resonant (PR) controller: The obtained error signal is input into the proportional resonant controller. The PR controller is a controller that can simultaneously achieve zero static error (i.e., no static error) and good dynamic performance, and is particularly suitable for processing periodic signals such as grid frequency signals. It consists of a proportional term P and a resonant term R, which can effectively track the changes of the sinusoidal waveform. Generate a modulation signal: The signal output by the PR controller is used as a reference signal for pulse width modulation (PWM) or a specific modulation method (such as SVPWM). SVPWM (space vector pulse width modulation) is an efficient modulation technology that uses two adjacent voltage vectors and a zero vector to synthesize the required reference voltage vector, and then generates the corresponding switching signal. Acting on PCS: Finally, these switching signals are used to directly drive the power switching devices (such as IGBT) in the PCS, thereby controlling the output of the PCS to achieve the purpose of adjusting the current. Through the precise control of the power switching devices, the output current of the energy storage converter PCS can accurately track the reference value, ensuring the stability and efficiency of the system. In addition, the application of SVPWM technology further improves the voltage utilization rate and reduces the harmonic content, optimizing the power quality. In the subsequent actual operation, the control strategy showed good dynamic response characteristics and anti-interference ability, providing a strong guarantee for the application of energy storage systems in power systems.

[0124] In summary, the present invention proposes a voltage support method and system for a real-life test platform PCS under an asymmetric fault, obtains circuit parameter information under an asymmetric fault of the real-life test platform PCS, and performs a first preprocessing on the circuit parameter information; presets a first voltage support strategy, calculates the maximum and minimum voltage amplitudes of the real-life test platform grid connection point and the negative-sequence voltage amplitude of the power grid according to the first voltage support strategy, and obtains positive and negative sequence active current reference values ​​and reactive current reference values; combines the positive and negative sequence active current reference values ​​and reactive current reference values ​​into current reference values ​​in the αβ coordinate system, and subtracts them from the output current of the real-life test platform PCS, obtains a modulation signal through a proportional resonant controller, and then generates a switching signal through SVPWM to act on the energy storage converter PCS. The voltage support method and system for the real-life test platform PCS under an asymmetric fault of the present invention can effectively improve the stability and reliability of the power grid. By accurately controlling the positive and negative sequence components of the PCS output current, the present invention can effectively suppress the negative sequence voltage in the power grid, thereby reducing the impact of asymmetric faults on the power grid. In addition, the present invention can also dynamically adjust the output current of the PCS according to the actual operation of the power grid to adapt to the real-time needs of the power grid.

[0125] This embodiment also provides a voltage support system for a real-life test platform PCS under an asymmetric fault, including:

[0126] A data acquisition module, used to acquire circuit parameter information under a PCS asymmetric fault of a real-life test platform, and perform a first preprocessing on the circuit parameter information;

[0127] Among them, the circuit parameter information includes grid voltage, output current, line inductance and line resistance;

[0128] The first preprocessing includes obtaining the grid voltage and output current in the αβ coordinate system through Clark transformation, and then performing positive and negative sequence separation on the grid voltage in the αβ coordinate system to obtain the grid positive sequence voltage amplitude, grid negative sequence voltage amplitude and grid positive and negative sequence voltage phase angle difference, and obtaining the positive sequence component amplitude and negative sequence component amplitude of the output current of the PCS of the real test platform, as well as the maximum and minimum values ​​of the voltage amplitude of the grid connection point of the real test platform;

[0129] A support strategy calculation module is used to preset a first voltage support strategy, calculate the maximum and minimum voltage amplitudes of the grid connection point of the actual test platform and the negative sequence voltage amplitude of the power grid according to the first voltage support strategy, and obtain positive and negative sequence active current reference values ​​and reactive current reference values;

[0130] The modulation module is used to combine the positive and negative sequence active current reference values ​​and reactive current reference values ​​into a current reference value in the αβ coordinate system, and to make a difference with the output current of the actual test platform PCS, to obtain a modulation signal through a proportional resonant controller, and then to generate a switching signal through SVPWM to act on the energy storage converter PCS.

[0131] The above-mentioned unit modules may be embedded in or independent of a processor in a computer device in the form of hardware, or may be stored in a memory in a computer device in the form of software, so that the processor can call and execute operations corresponding to the above-mentioned modules.

[0132] This embodiment also provides a computer device, which may be a terminal, and its internal structure diagram may be as shown in FIG. Figure 5 As shown. The computer device includes a processor, a memory, a communication interface, a display screen and an input device connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. When the computer program is executed by the processor, a voltage support method for a real-life test platform PCS under an asymmetric fault is implemented. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covered on the display screen, or a key, trackball or touchpad set on the computer device housing, or an external keyboard, touchpad or mouse, etc.

[0133] This embodiment further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the following steps are implemented:

[0134] Acquire circuit parameter information under a PCS asymmetric fault of a real-life test platform, and perform a first preprocessing on the circuit parameter information;

[0135] Among them, the circuit parameter information includes grid voltage, output current, line inductance and line resistance;

[0136] The first preprocessing includes obtaining the grid voltage and output current in the αβ coordinate system through Clark transformation, and then performing positive and negative sequence separation on the grid voltage in the αβ coordinate system to obtain the grid positive sequence voltage amplitude, grid negative sequence voltage amplitude and grid positive and negative sequence voltage phase angle difference, and obtaining the positive sequence component amplitude and negative sequence component amplitude of the output current of the PCS of the real test platform, as well as the maximum and minimum values ​​of the voltage amplitude of the grid connection point of the real test platform;

[0137] A first voltage support strategy is preset, and the maximum and minimum voltage amplitudes of the grid connection point of the actual test platform and the negative sequence voltage amplitude of the power grid are calculated according to the first voltage support strategy to obtain positive and negative sequence active current reference values ​​and reactive current reference values;

[0138] The positive and negative sequence active current reference values ​​and reactive current reference values ​​are combined into a current reference value in the αβ coordinate system, and the value is subtracted from the output current of the actual test platform PCS. The modulation signal is obtained through the proportional resonant controller, and then the switching signal is generated through SVPWM to act on the energy storage converter PCS.

[0139] Example 2

[0140] Reference Figure 2-Figure 3 , which is an embodiment of the present invention, provides a voltage support method and system for a real-life test platform PCS under an asymmetric fault. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through experiments.

[0141] The attached Figure 2 The control strategy structure diagram of the real-life test platform system under asymmetric faults is shown in the figure. According to the physical structure and parameter settings of the test platform, the simulation parameters are as follows: the DC side voltage is 700V; the DC side capacitance is 2000μF; the PCS rated power is 20kW; the PCS rated current is 32.15A; the rooftop photovoltaic is 50kW; the AC measurement filter inductance is 2mH; the grid rated voltage is 311V; the line inductance is 4mH; and the line resistance is 2Ω.

[0142] In order to verify the feasibility and advantages of this patent, an existing voltage support strategy under asymmetric faults is used as a comparison method. The simulation is set to have an asymmetric voltage sag in the power grid at 0.3s. The vector expressions of the three-phase voltages of the real test platform abc are 124.4∠0°, 311∠-120° and 311∠120°, respectively. The voltage returns to normal at 0.7s. The positive and negative sequence active current reference values ​​and the positive and negative sequence reactive current reference values ​​set by the comparison strategy are 20.77A, -13.07A, 13.05A and 8.21A, respectively. The voltage support strategy of the real test platform PCS under asymmetric faults proposed in the present invention sets the positive and negative sequence active current reference values ​​and the positive and negative sequence reactive current reference values ​​to 26.64A, -9.66A, 16.73A and 6.07A, respectively. During the fault period, the current reference value is set by the comparison strategy within 0.3s to 0.5s, and the current reference value is set by the voltage support strategy of the proposed real-life test platform PCS under asymmetric fault within 0.5s to 0.7s. The simulation results are as follows: Figure 3 and Figure 4 As shown. Analysis shows that: the comparison strategy can min Support to 279.8V, and the voltage support strategy proposed by the present invention can min It supports up to 286.8V. This shows that when an asymmetric fault occurs in the actual test platform, the PCS control strategy designed according to the real scenario of the actual test platform has a better voltage support effect, which is beneficial to improving the distribution network fault simulation capability of the actual test platform.

[0143] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0144] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0145] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0146] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0147] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0148] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0149] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A voltage support method for a real-world test platform PCS under asymmetric faults, characterized in that: include: Acquire circuit parameter information of a real-life test platform PCS asymmetric fault, and perform a first preprocessing on the circuit parameter information; Wherein, the circuit parameter information includes grid voltage, output current, line inductance and line resistance; The first preprocessing includes obtaining the grid voltage and output current in the αβ coordinate system through Clark transformation, and then performing positive and negative sequence separation on the grid voltage in the αβ coordinate system to obtain the grid positive sequence voltage amplitude, grid negative sequence voltage amplitude and grid positive and negative sequence voltage phase angle difference, and obtaining the positive sequence component amplitude and negative sequence component amplitude of the output current of the PCS of the real test platform, as well as the maximum and minimum values ​​of the voltage amplitude of the grid connection point of the real test platform; A first voltage support strategy is preset, and the maximum and minimum voltage amplitudes of the grid connection points of the actual test platform and the negative sequence voltage amplitude of the power grid are calculated according to the first voltage support strategy to obtain positive and negative sequence active current reference values ​​and reactive current reference values; The positive and negative sequence active current reference values ​​and reactive current reference values ​​are combined into a current reference value in the αβ coordinate system, and the value is subtracted from the output current of the actual test platform PCS. A modulation signal is obtained through a proportional resonant controller, and then a switching signal is generated through SVPWM to act on the energy storage converter PCS.

2. The voltage support method of the PCS in a real-life test platform under asymmetric faults according to claim 1, characterized in that: The first preprocessing further comprises: The grid voltage in the αβ coordinate system is separated into positive and negative sequences to obtain the grid positive sequence voltage amplitude, grid negative sequence voltage amplitude and grid positive and negative sequence voltage phase angle difference, and the positive sequence component amplitude and negative sequence component amplitude of the output current of the real test platform PCS are obtained; Among them, the positive sequence component amplitude and negative sequence component amplitude of the PCS output current of the real test platform are expressed as: Among them, I max Indicates the maximum value among the three-phase current amplitudes; I + and I - They represent the amplitudes of the positive-sequence and negative-sequence components of the PCS output current of the real-world test platform respectively; and They respectively represent the amplitudes of the positive sequence active component and reactive component of the PCS output current of the real test platform; and They represent the amplitudes of the negative sequence active component and reactive component of the PCS output current of the real test platform respectively; atan2(*,*) is the four-quadrant inverse tangent function, θ + and θ - They represent the initial phases of the positive-sequence component and the negative-sequence component of the grid-connected point voltage of the actual test platform respectively, and φ represents the phase angle difference between the positive-sequence and negative-sequence currents of the power grid.

3. The voltage support method of the PCS in a real-life test platform under asymmetric faults according to claim 2, characterized in that: The first preprocessing further comprises: The grid voltage in the αβ coordinate system is separated into positive and negative sequences to obtain the grid positive sequence voltage amplitude, grid negative sequence voltage amplitude and grid positive and negative sequence voltage phase angle difference; Among them, the expression of the positive and negative sequence voltage amplitude of the grid connection point of the real test platform is: Among them, U + and U - They represent the amplitudes of the positive-sequence component and the negative-sequence component of the grid-connected point voltage of the actual test platform respectively; ω represents the angular frequency of the fundamental wave component of the grid of the actual test platform, Indicates the positive sequence voltage amplitude of the power grid, Represents the negative sequence voltage amplitude of the power grid, R g Indicates line resistance. L g Indicates line inductance.

4. The voltage support method of the PCS in a real-life test platform under asymmetric faults according to claim 3, characterized in that: The first preprocessing further comprises: The grid voltage and output current are transformed by Clark to obtain the grid voltage and the output current of the PCS in the αβ coordinate system, and then the grid voltage in the αβ coordinate system is separated into positive and negative sequences to obtain the grid positive sequence voltage amplitude, grid negative sequence voltage amplitude and grid positive and negative sequence voltage phase angle difference, and the positive sequence component amplitude and negative sequence component amplitude of the output current of the PCS in the real test platform, as well as the maximum and minimum values ​​of the voltage amplitude at the grid connection point of the real test platform; Among them, the expression of the voltage amplitude of the grid connection point of the actual test platform is as follows: Among them, U max and U min Respectively represent the maximum and minimum values ​​of the three-phase voltage amplitude; θ + and θ - They respectively represent the initial phases of the positive-sequence component and the negative-sequence component of the grid-connected point voltage on the actual test platform.

5. The voltage support method of the PCS in a real-life test platform under asymmetric faults according to claim 4, characterized in that: The preset first voltage support strategy includes: if and only if the grid connection point voltage of the actual test platform meets 0.9U N ~1.1U N When PCS can run continuously, U N is the rated voltage of the power grid of the actual test platform.

6. The voltage support method of the PCS in a real-life test platform under asymmetric faults according to claim 5, characterized in that: The preset first voltage support strategy also includes: assuming that the positive sequence current amplitude allowed to be output is The goal is to maximize the positive sequence voltage support. As the constraint condition, the first Lagrangian function is constructed, assuming that the allowed output negative sequence current is The goal is to maximize the suppression of negative sequence voltage. As the constraint condition, the second Lagrangian function is constructed.

7. The voltage support method of the PCS in a real-life test platform under asymmetric faults according to claim 6, characterized in that: The preset first voltage support strategy also includes: According to the first Lagrangian function and the second Lagrangian function, an optimal ratio 1 of the amplitude of the positive-sequence active component and the reactive component of the output current of the real-life test platform PCS, and an optimal ratio 2 of the amplitude of the negative-sequence active component and the reactive component of the output current of the real-life test platform PCS are obtained; Obtaining positive and negative sequence voltage values ​​of the grid connection point of the actual test platform according to the optimal ratio one and the optimal ratio two; According to the positive and negative sequence voltage values ​​of the grid connection point of the actual test platform, the grid connection point voltage of 0.9U is calculated to meet the actual test platform. N ~1.1U N The positive and negative sequence active current reference value and reactive current reference value under the constraint of .

8. A voltage support system for a real-life test platform PCS under asymmetric faults, characterized in that: include: A data acquisition module, used to acquire circuit parameter information under a PCS asymmetric fault of a real-life test platform, and perform a first preprocessing on the circuit parameter information; Wherein, the circuit parameter information includes grid voltage, output current, line inductance and line resistance; The first preprocessing includes obtaining the grid voltage and output current in the αβ coordinate system through Clark transformation, and then performing positive and negative sequence separation on the grid voltage in the αβ coordinate system to obtain the grid positive sequence voltage amplitude, grid negative sequence voltage amplitude and grid positive and negative sequence voltage phase angle difference, and obtaining the positive sequence component amplitude and negative sequence component amplitude of the output current of the PCS of the real test platform, as well as the maximum and minimum values ​​of the voltage amplitude of the grid connection point of the real test platform; A support strategy calculation module is used to preset a first voltage support strategy, calculate the maximum and minimum voltage amplitudes of the grid connection point of the actual test platform and the negative sequence voltage amplitude of the power grid according to the first voltage support strategy, and obtain positive and negative sequence active current reference values ​​and reactive current reference values; The modulation module is used to combine the positive and negative sequence active current reference values ​​and reactive current reference values ​​into a current reference value in the αβ coordinate system, and to make a difference with the output current of the actual test platform PCS, to obtain a modulation signal through a proportional resonant controller, and then to generate a switching signal through SVPWM to act on the energy storage converter PCS.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

Images