Enhanced SVG (static var generator) low-voltage ride-through method and related equipment

Abstract

The invention discloses an enhanced SVG low voltage ride through method, and belongs to the technical field of electrical automation equipment, and the method comprises the steps: carrying out the three-phase voltage synthesis of a self-built voltage amplitude and a self-built voltage phase, and obtaining a current reference value through an electromagnetic square; according to the self-built voltage phase and the current reference value, a bridge arm differential mode voltage modulation wave is obtained through inner loop current control; obtaining a main circuit commutation actual value of the enhanced SVG, and obtaining a bridge arm common-mode voltage modulation wave through circulating current suppression control in combination with the self-built voltage phase; actual energy and rated energy of the enhanced SVG are obtained, and an energy modulation signal is obtained through an energy control ring; and after modulation is carried out according to the bridge arm differential mode voltage modulation wave, the bridge arm common mode voltage modulation wave and an energy modulation signal, a switching signal is generated to control the enhanced SVG, and low voltage ride through is realized. According to the invention, the problem that the enhanced SVG fails or is off-network under the condition of low voltage can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical automation equipment, and in particular to an enhanced SVG low voltage ride-through method and related equipment. Background Art

[0002] With the acceleration of global energy transformation, the traditional power system is gradually transitioning to a new power system. The new power system is centered on clean energy and emphasizes the wide access of renewable energy. It is usually connected to the power grid through power electronic converters and lacks the frequency response provided by generators through rotating mechanical inertia. In addition, due to the volatility and intermittency of renewable energy, the voltage and frequency stability of the power grid are more easily affected, making the power grid show weaker characteristics.

[0003] In order to adapt to the weak power grid environment, the energy storage system is integrated on the basis of the existing reactive power compensation device (static var generator, SVG) of the new energy station to reserve active power for the grid inertia support, taking into account the autonomous inertia response and active voltage support, forming an integrated high-performance power quality control device with the ability to simultaneously adjust active and reactive power, namely Enhanced SVG (Enhanced SVG, ESVG), which can quickly adjust the active and reactive output, smooth the frequency and voltage fluctuations, and improve the voltage and frequency stability of the power system. At the same time, the new power system requires that the equipment connected to the power grid has a certain ability to resist power grid failures. When the power grid experiences a short-term voltage drop, if the enhanced SVG device fails or disconnects from the grid under low voltage conditions, the frequency and voltage stability of the entire system will face serious threats, further triggering more serious chain failures and even leading to power grid collapse.

[0004] Since the inverter has limited ability to suppress overcurrent, in order to ensure the safe operation of enhanced SVG during grid short-circuit faults, it is necessary to study the low voltage ride-through strategy of enhanced SVG with weak grid adaptability conditions, so that it can effectively suppress transient overcurrent and instantaneous impact overcurrent while meeting its own safe and stable operation under grid fault conditions, ensuring rapid and stable power output, and smooth connection between the low voltage ride-through strategy and the steady-state grid-connected strategy after fault recovery. Summary of the invention

[0005] The object of the present invention is to provide an enhanced SVG low voltage ride through method and related equipment to solve the problem of enhanced SVG failure or disconnection from the grid under low voltage conditions.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, an enhanced SVG low voltage ride-through method comprises the following steps: The steady-state reactive loop is converted into a transient reactive loop to obtain the self-built voltage amplitude, and the steady-state active loop is converted into a transient active loop to obtain the self-built voltage phase; After synthesizing the three-phase voltage according to the self-built voltage amplitude and the self-built voltage phase, a current reference value is obtained through an electromagnetic square; According to the self-built voltage phase and current reference value, a bridge arm differential mode voltage modulation wave is obtained through inner loop current control; The actual commutation value of the main circuit of the enhanced SVG is obtained, and combined with the self-built voltage phase, a bridge arm common mode voltage modulation wave is obtained through circulating current suppression control; Obtain the actual energy and rated energy of the enhanced SVG, and obtain the energy modulation signal through the energy control loop; After modulation according to the bridge arm differential mode voltage modulation wave, the bridge arm common mode voltage modulation wave and the energy modulation signal, a switch signal is generated to control the enhanced SVG to achieve low voltage ride through.

[0007] In some implementations, the step of converting a steady-state reactive loop into a transient reactive loop to obtain a self-built voltage amplitude specifically includes: Determine a reactive power reference value during an enhanced SVG fault, subtract the reactive power reference value from the actual reactive power of the converter, and add the difference to the voltage amplitude after processing and integrating through a proportional coefficient in sequence to obtain a self-built voltage amplitude; When the grid voltage drop depth is ≥0.9, the voltage amplitude is the rated voltage; when the grid voltage drop depth is <0.9, the voltage amplitude is the grid-connected voltage amplitude under fault conditions.

[0008] In some implementations, the step of converting a steady-state active power loop into a transient active power loop to obtain a self-built voltage phase specifically includes: Determine the steady-state self-built voltage angle of the steady-state active loop output, and perform phase compensation to obtain the phase correction angle after correcting the active power reference value during the enhanced SVG fault period; The steady-state self-generated voltage angle and the phase correction angle are added to obtain the self-generated voltage phase.

[0009] In some embodiments, the electromagnetic equation is as follows:

[0010] in, is the self-built voltage amplitude after the three-phase voltage is synthesized, is the grid voltage amplitude in the fault condition after the three-phase voltage is synthesized, is a virtual resistor, is the virtual reactance, is the current reference value.

[0011] In some implementations, the step of obtaining a bridge arm differential mode voltage modulation wave through inner loop current control according to the self-built voltage phase and current reference value specifically includes: Performing a dq transformation on the current reference value to obtain a d-axis current reference value and a q-axis current reference value, wherein the rotation angle of the dq transformation is the self-built voltage phase; The d-axis current reference value is subtracted from the measured d-axis actual current value, and the q-axis current value is subtracted from the measured q-axis actual current value. After passing through the PI regulator and cross-decoupling, an inverse Park transformation is performed according to the self-built voltage phase to obtain a bridge arm differential mode voltage modulation wave.

[0012] In some implementations, the step of obtaining the actual commutation value of the main circuit of the enhanced SVG and obtaining the bridge arm common mode voltage modulation wave by circulating current suppression control in combination with the self-built voltage phase specifically includes: The circulating current reference value of the circulating current suppression ring is set to 0, and the actual value of the main circuit commutation of the enhanced SVG is rotated by an angle of -2 θ D -2 q -2 After the conversion, the difference is made with the circulating current reference value, and then it passes through the PI regulator and cross-decoupled, and then passes through d -2 q -2 After the inverse transformation, the bridge arm common mode voltage modulation wave is obtained. θ It is the self-built voltage phase.

[0013] In some implementations, the step of obtaining the actual energy and rated energy of the enhanced SVG and obtaining the energy modulation signal through the energy control loop specifically includes: After subtracting the actual energy from the rated energy, a DC current reference value is obtained through a PI regulator, and the DC current reference value is subtracted from the measured actual DC current value, and the energy modulation signal is obtained after passing through the PI regulator again.

[0014] In a second aspect, an enhanced SVG low voltage ride-through system includes: A self-built voltage construction module is used to convert a steady-state reactive loop into a transient reactive loop to obtain a self-built voltage amplitude, and to convert a steady-state active loop into a transient active loop to obtain a self-built voltage phase; A current reference value calculation module, used to obtain a current reference value through an electromagnetic square after synthesizing the three-phase voltage according to the self-built voltage amplitude and the self-built voltage phase; A bridge arm differential mode voltage modulation wave construction module, used to obtain a bridge arm differential mode voltage modulation wave through inner loop current control according to the self-built voltage phase and current reference value; A bridge arm common mode voltage modulation wave construction module is used to obtain the actual value of the main circuit commutation of the enhanced SVG, and obtain the bridge arm common mode voltage modulation wave through circulating current suppression control in combination with the self-built voltage phase; An energy modulation signal building module is used to obtain the actual energy and rated energy of the enhanced SVG and obtain the energy modulation signal through the energy control loop; The switch control module is used to generate a switch signal to control the enhanced SVG to achieve low voltage ride through after modulating the bridge arm differential mode voltage modulation wave, the bridge arm common mode voltage modulation wave and the energy modulation signal.

[0015] In a third aspect, a computer device comprises a memory, a processor, and a computer program stored in the memory and executable in the processor, wherein the processor implements the steps of the enhanced SVG low voltage ride-through method when executing the computer program.

[0016] In a fourth aspect, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the enhanced SVG low voltage ride-through method are implemented.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides an enhanced SVG low voltage ride-through method, which converts a steady-state reactive loop into a transient reactive loop to obtain a self-built voltage amplitude, and converts a steady-state active loop into a transient active loop to obtain a self-built voltage phase. The enhanced SVG can quickly respond to the phase jump at the moment of the fault and adapt to the amplitude drop during the fault period; finally, after modulation according to the bridge arm differential mode voltage modulation wave, the bridge arm common mode voltage modulation wave and the energy modulation signal, a switch signal is generated to control the enhanced SVG, which can greatly shorten the phase adjustment time while achieving overcurrent suppression, ensure stable power output, and improve the inertial support capacity of the enhanced SVG device for the power grid during the fault period. The present invention can provide dual active support for power grid voltage and frequency, overcome the adverse effects of power grid faults, and smoothly transition to power grid fault recovery, solving the problem of enhanced SVG failure or disconnection under low voltage conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 An overall control block diagram of an enhanced SVG low voltage ride-through method provided by an embodiment of the present invention; Figure 2 A block diagram of a transient active power-frequency control loop used in an enhanced SVG low voltage ride-through method provided in an embodiment of the present invention; Figure 3 A block diagram of a transient reactive power-voltage control loop used in an enhanced SVG low voltage ride-through method provided in an embodiment of the present invention; Figure 4 A block diagram of three-phase voltage synthesis and electromagnetic equations used in an enhanced SVG low voltage ride-through method provided in an embodiment of the present invention; Figure 5 A block diagram of a current inner loop control circuit adopted by an enhanced SVG low voltage ride-through method provided in an embodiment of the present invention; Figure 6 A block diagram of a circulating current suppression control loop adopted by an enhanced SVG low voltage ride-through method provided in an embodiment of the present invention; Figure 7 A block diagram of an energy control loop used in an enhanced SVG low voltage ride-through method provided in an embodiment of the present invention; Figure 8 A control action flow chart of an enhanced SVG low voltage ride-through method provided by an embodiment of the present invention; Fig. 9 A flowchart of an enhanced SVG low voltage ride-through method provided by an embodiment of the present invention; Fig.10 A schematic diagram of the structure of an enhanced SVG low voltage ride-through system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings, and the described content is intended to explain the present invention rather than to limit it.

[0020] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or are inherent to these processes, methods, systems, products or apparatus.

[0021] This embodiment provides an enhanced SVG low voltage ride-through method, which can cope with enhanced SVGs of different topologies, increase the response to grid fault ride-through on the basis of a stable grid-connected control strategy; simultaneously perform amplitude adjustment and phase angle correction, as well as reference value changes of corresponding loops; on the basis of ensuring the realization of the basic functions of enhanced SVG voltage and frequency dual active support under weak grid fault conditions, resist excessive current shocks, and enable the enhanced SVG device to operate stably under transient conditions.

[0022] like Figure 1As shown in FIG. 1 , it is the overall control block diagram of the method, which adds a correction strategy to adapt to the grid short-circuit fault condition on the original steady-state grid-connected control strategy of the enhanced SVG, which is specifically embodied in: the steady-state reactive loop is converted into a transient reactive loop after the reactive reference value is changed and the amplitude is adjusted, the steady-state active loop is converted into a transient active loop after the active reference value is changed and the phase is corrected, and the electromagnetic equation loop, the current inner loop, and the circulating current suppression loop coordinated with the active loop and the reactive loop control the energy control loop of the energy storage system.

[0023] like Fig. 9 As shown, the enhanced SVG low voltage ride-through method with inertial response and weak grid adaptability specifically includes the following steps: S1, converting the steady-state reactive loop into a transient reactive loop to obtain the self-built voltage amplitude, and converting the steady-state active loop into a transient active loop to obtain the self-built voltage phase; Preferably, Figure 3 As shown in the figure, the steady-state reactive loop is transformed into a transient reactive loop by changing the reactive reference value and adjusting the amplitude: Based on the reactive voltage loop of the enhanced SVG steady-state grid-connected control, in order to meet the voltage support during the fault, the reactive power reference value during the fault Q' ref According to the voltage amplitude at the grid connection point | U | and reference value in case of reactive current fault I Qref The decision is as follows:

[0024] The reference value of reactive current fault condition I Qref According to the grid voltage drop depth at this time, the corresponding correction changes are made. The grid voltage drop depth is defined as the grid voltage amplitude under fault conditions| U |With rated voltage U N ratio, reference value in case of reactive current fault I Qref The settings are as follows:

[0025] in U N and I N are rated voltage and rated current respectively, | U | / U N Indicates the depth of the voltage drop, defined in the range of 0.1 to 0.9. | U | / UN Less than 0.1 means voltage interruption; | U | / U N A voltage greater than 0.9 is within the normal range of voltage variation. There is no need to enable the loop correction strategy during the fault period, and the steady-state reactive loop can provide the required voltage support. K i is the current coefficient, generally taken as 1.5.

[0026] Determine reactive power reference value during fault Q' ref Then compare it with the actual reactive power of the converter Q Make a difference, after the proportional coefficient K E Processing, and then through the integration link, and the voltage amplitude E 0 and add to get the final self-built voltage amplitude E During the fault period, the self-built voltage amplitude needs to be reduced quickly to achieve the purpose of quickly and timely reducing the enhanced SVG grid-connected voltage amplitude. The overall control and amplitude adjustment of the transient reactive loop during the fault period are shown in the following formula:

[0027] Preferably, Figure 2 As shown in the figure, the steady-state active loop is transformed into a transient active loop by changing the active reference value and correcting the phase: Based on the active frequency loop of the enhanced SVG steady-state grid-connected control, the active reference frequency is adjusted according to the different operating conditions of the device. P' ref To set up:

[0028] After correcting the active reference value, the phase needs to be compensated to adapt to the phase jump in the case of grid voltage failure. Since the active frequency loop of the enhanced SVG device itself has a certain virtual inertia, a direct compensation method is adopted, which is divided into reference correction and power angle correction for phase compensation.

[0029] Reference correction compensation angle α It is the angle between the grid voltage phase and the reference phase under fault condition. The specific calculation method is as follows:

[0030] in, U d and U q They are the d-axis and q-axis components of the grid-connected voltage of the enhanced SVG during a fault in the synchronous rotating coordinate system.

[0031] Power angle correction compensation angle β It is obtained based on the relationship between active power output and power angle, as shown in the following formula:

[0032] in, X v It is the virtual reactance in the electromagnetic equation, that is, the equivalent reactance between the self-built voltage and the grid-connected voltage.

[0033] According to the vector diagram, the voltage vector under fault condition is derived, and the phase correction angle θ' The expression is:

[0034] The steady-state active loop of the enhanced SVG adjusts the system frequency according to the unbalanced torque or power, so that the system has inertia and damping characteristics. The final output of the active loop is the phase angle of the self-built voltage of the enhanced SVG. The specific expression of the loop is as follows:

[0035] in, P is the actual output active power, ω 0 is the rated angular velocity, ω is the actual angular velocity, θ is the self-built voltage angle, J is the moment of inertia, D is the damping coefficient.

[0036] The steady-state active power loop is corrected according to the above-mentioned changed active power reference value and phase compensation. The expression of the corrected transient active power loop is as follows:

[0037] at this time θ It is the sum of the steady-state self-built voltage angle and the phase correction angle.

[0038] S2, after synthesizing the three-phase voltage according to the self-built voltage amplitude and the self-built voltage phase, obtain a current reference value through an electromagnetic square; Preferably, Figure 4 As shown in the figure, the current reference value obtained by the electromagnetic equation is: The self-built voltage amplitude and self-built voltage phase of the enhanced SVG under fault conditions are obtained from the transient reactive loop and the transient active loop respectively. Through the electromagnetic equation shown below, the virtual resistance R v and virtual reactance L v , get the reference value of the final current i ref .

[0039]

[0040] in, is the self-built voltage amplitude after the three-phase voltage is synthesized, It is the grid voltage amplitude in the fault condition after the three-phase voltage is synthesized.

[0041] S3, obtaining a bridge arm differential mode voltage modulation wave through inner loop current control according to the self-built voltage phase and current reference value; Preferably, Figure 5 As shown in the figure, the bridge arm differential mode voltage modulation wave obtained by inner loop current control is: Current reference value i ref The rotation angle is θ The dq transformation is used to obtain the current reference values ​​of the d-axis and q-axis. i dref , i qref , as the reference of the current inner loop, and compare it with the measured transformed i d , i q After the PI regulator is used for cross decoupling, the differential mode voltage modulation wave is obtained by performing inverse Park transformation according to the self-built voltage phase angle. v diff .

[0042] S4, obtaining the actual commutation value of the main circuit of the enhanced SVG, and combining it with the self-built voltage phase, obtaining a bridge arm common mode voltage modulation wave through circulating current suppression control; Preferably, Figure 6 As shown in the figure, the common mode voltage modulation wave obtained through the circulating current suppression loop is specifically: Set the reference value of the circulating current suppression loop to 0 and collect the actual value of the circulating current of the enhanced SVG main circuit i cir And rotate it by an angle of -2 θ D -2 q -2 Transformation, subtraction with circulating current reference value, cross decoupling after PI adjustment, and then through d -2 q -2 After inverse transformation, the bridge arm common mode voltage modulation wave is obtained v com .

[0043] S5, obtaining the actual energy and rated energy of the enhanced SVG, and obtaining an energy modulation signal through an energy control loop; Preferably, Figure 7 As shown, the energy control signal obtained through the energy control loop is specifically: The actual energy in the enhanced SVG module is subtracted from the rated energy, and the DC current reference value is obtained through a PI regulator. The DC current reference value is then subtracted from the actual DC current value, and the energy modulation signal is finally obtained through a PI regulator.

[0044] S6, differential mode voltage modulation wave obtained according to enhanced SVG transient control v diff , the common mode voltage modulation wave obtained by circulating current suppression control v com And the corresponding energy modulation signal is modulated, and finally a switching signal is generated to act on the enhanced SVG device to achieve low voltage ride-through of the enhanced SVG.

[0045] like Figure 8 As shown, it is a control action flow chart of the low voltage ride-through method provided in this embodiment: Determine whether the grid voltage drop depth is less than 0.9. If it is not less than 0.9, it is a non-fault period and the voltage change is within the normal range. There is no need to implement the low voltage ride-through method of this embodiment. If it is less than 0.9, proceed to the next step. Will Figure 1 Switch S1, S2, and S4 to position 1. After S3 is closed, determine whether the grid voltage drop depth is greater than 0.9. If not, the fault has not been restored and continue to wait and make a judgment. If greater than 0.9, switch S4 to position 0 and proceed to the next step. Determine whether the absolute value of the self-built voltage phase is less than ε , ε A small positive number is used to prevent current shock. Usually, it can be set to 1% of the rated value. ε Then continue to wait. If it is less than ε Then switch S1 and S2 to position 0, and disconnect S3 to complete the control.

[0046] The enhanced SVG low voltage ride-through method provided in this embodiment can cope with enhanced SVGs of different topologies, increase the response to grid fault ride-through on the basis of a stable grid-connected control strategy, and simultaneously perform amplitude adjustment and phase angle correction, as well as reference value changes of corresponding loops. On the basis of ensuring the realization of the basic functions of enhanced SVG voltage and frequency dual active support under weak grid fault conditions, it resists excessive current shocks and enables the enhanced SVG device to operate stably under transient conditions.

[0047] like Fig.10 As shown, this embodiment provides an enhanced SVG low voltage ride-through system, including: A self-built voltage construction module is used to convert a steady-state reactive loop into a transient reactive loop to obtain a self-built voltage amplitude, and to convert a steady-state active loop into a transient active loop to obtain a self-built voltage phase; A current reference value calculation module, used to obtain a current reference value through an electromagnetic square after synthesizing the three-phase voltage according to the self-built voltage amplitude and the self-built voltage phase; A bridge arm differential mode voltage modulation wave construction module, used to obtain a bridge arm differential mode voltage modulation wave through inner loop current control according to the self-built voltage phase and current reference value; A bridge arm common mode voltage modulation wave construction module is used to obtain the actual value of the main circuit commutation of the enhanced SVG, and obtain the bridge arm common mode voltage modulation wave through circulating current suppression control in combination with the self-built voltage phase; An energy modulation signal building module is used to obtain the actual energy and rated energy of the enhanced SVG and obtain the energy modulation signal through the energy control loop; The switch control module is used to generate a switch signal to control the enhanced SVG to achieve low voltage ride through after modulating the bridge arm differential mode voltage modulation wave, the bridge arm common mode voltage modulation wave and the energy modulation signal.

[0048] The division of modules in the embodiments of the present invention is schematic and is only a logical function division. There may be other division methods in actual implementation. In addition, each functional module in each embodiment of the present invention may be integrated into one processor, or may exist physically separately, or two or more modules may be integrated into one module. The above-mentioned integrated modules may be implemented in the form of hardware or in the form of software functional modules.

[0049] In this embodiment, a computer device is also provided, which includes a processor and a memory, wherein the memory is used to store a computer program (in this embodiment, the computer program includes a computing component and an iterative component, and can perform model calculation and model update), the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in a computer storage medium to implement a corresponding method flow or a corresponding function; the processor described in the embodiment of the present invention can be used for the operation of an enhanced SVG low voltage ride-through method.

[0050] This embodiment also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It can be understood that the computer-readable storage medium here can include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of an enhanced SVG low voltage ride-through method in the above embodiment.

[0051] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take 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.) containing computer-usable program code.

[0052] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks 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 produce 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.

[0053] 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.

[0054] 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 A step that specifies a function in one or more boxes.

[0055] Finally, 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 above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An enhanced SVG low voltage ride-through method, characterized in that: The following steps are involved: The steady-state reactive loop is converted into a transient reactive loop to obtain the self-built voltage amplitude, and the steady-state active loop is converted into a transient active loop to obtain the self-built voltage phase; After synthesizing the three-phase voltage according to the self-built voltage amplitude and the self-built voltage phase, a current reference value is obtained through an electromagnetic square; According to the self-built voltage phase and current reference value, a bridge arm differential mode voltage modulation wave is obtained through inner loop current control; The actual commutation value of the main circuit of the enhanced SVG is obtained, and combined with the self-built voltage phase, a bridge arm common mode voltage modulation wave is obtained through circulating current suppression control; Obtain the actual energy and rated energy of the enhanced SVG, and obtain the energy modulation signal through the energy control loop; After modulation according to the bridge arm differential mode voltage modulation wave, the bridge arm common mode voltage modulation wave and the energy modulation signal, a switch signal is generated to control the enhanced SVG to achieve low voltage ride through.

2. The enhanced SVG low voltage ride-through method according to claim 1, characterized in that: The step of converting the steady-state reactive loop into a transient reactive loop to obtain the self-built voltage amplitude specifically includes: Determine a reactive power reference value during an enhanced SVG fault, subtract the reactive power reference value from the actual reactive power of the converter, and add the difference to the voltage amplitude after processing and integrating through a proportional coefficient in sequence to obtain a self-built voltage amplitude; When the grid voltage drop depth is ≥0.9, the voltage amplitude is the rated voltage; when the grid voltage drop depth is <0.9, the voltage amplitude is the grid-connected voltage amplitude under fault conditions.

3. The enhanced SVG low voltage ride-through method according to claim 1, characterized in that: The step of converting the steady-state active power loop into a transient active power loop to obtain a self-built voltage phase specifically includes: Determine the steady-state self-built voltage angle of the steady-state active loop output, and perform phase compensation to obtain the phase correction angle after correcting the active power reference value during the enhanced SVG fault period; The steady-state self-generated voltage angle and the phase correction angle are added to obtain the self-generated voltage phase.

4. The enhanced SVG low voltage ride-through method according to claim 1, characterized in that: The electromagnetic equation is as follows: in, is the self-built voltage amplitude after the three-phase voltage is synthesized, is the grid voltage amplitude in the fault condition after the three-phase voltage is synthesized, is a virtual resistor, is the virtual reactance, is the current reference value.

5. The enhanced SVG low voltage ride through method according to claim 1, characterized in that: The step of obtaining a bridge arm differential mode voltage modulation wave through inner loop current control according to the self-built voltage phase and current reference value specifically includes: Performing a dq transformation on the current reference value to obtain a d-axis current reference value and a q-axis current reference value, wherein the rotation angle of the dq transformation is the self-built voltage phase; The d-axis current reference value is subtracted from the measured d-axis actual current value, and the q-axis current value is subtracted from the measured q-axis actual current value. After passing through the PI regulator and cross-decoupling, an inverse Park transformation is performed according to the self-built voltage phase to obtain a bridge arm differential mode voltage modulation wave.

6. The enhanced SVG low voltage ride-through method according to claim 1, characterized in that: The step of obtaining the actual commutation value of the main circuit of the enhanced SVG and obtaining the bridge arm common mode voltage modulation wave by circulating current suppression control in combination with the self-built voltage phase specifically includes: The circulating current reference value of the circulating current suppression ring is set to 0, and the actual value of the main circuit commutation of the enhanced SVG is rotated by an angle of -2 θ D -2 q -2 After the conversion, the difference is made with the circulating current reference value, and then it passes through the PI regulator and cross-decoupled, and then passes through d -2 q -2 After the inverse transformation, the bridge arm common mode voltage modulation wave is obtained. θ It is the self-built voltage phase.

7. The enhanced SVG low voltage ride-through method according to claim 1, characterized in that: The step of obtaining the actual energy and rated energy of the enhanced SVG and obtaining the energy modulation signal through the energy control loop specifically includes: After subtracting the actual energy from the rated energy, a DC current reference value is obtained through a PI regulator, and the DC current reference value is subtracted from the measured actual DC current value, and the energy modulation signal is obtained after passing through the PI regulator again.

8. An enhanced SVG low voltage ride through system, characterized in that: include: A self-built voltage construction module is used to convert a steady-state reactive loop into a transient reactive loop to obtain a self-built voltage amplitude, and to convert a steady-state active loop into a transient active loop to obtain a self-built voltage phase; A current reference value calculation module, used to obtain a current reference value through an electromagnetic square after synthesizing the three-phase voltage according to the self-built voltage amplitude and the self-built voltage phase; A bridge arm differential mode voltage modulation wave construction module, used to obtain a bridge arm differential mode voltage modulation wave through inner loop current control according to the self-built voltage phase and current reference value; A bridge arm common mode voltage modulation wave construction module is used to obtain the actual value of the main circuit commutation of the enhanced SVG, and obtain the bridge arm common mode voltage modulation wave through circulating current suppression control in combination with the self-built voltage phase; An energy modulation signal building module is used to obtain the actual energy and rated energy of the enhanced SVG and obtain the energy modulation signal through the energy control loop; The switch control module is used to generate a switch signal to control the enhanced SVG to achieve low voltage ride through after modulating the bridge arm differential mode voltage modulation wave, the bridge arm common mode voltage modulation wave and the energy modulation signal.

9. A computer device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable in the processor, wherein the processor implements the steps of an enhanced SVG low voltage ride-through method as claimed in any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the enhanced SVG low voltage ride-through method according to any one of claims 1 to 7 are implemented.

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