An enhanced SVG low voltage ride through method and related devices

Abstract

The application discloses a kind of enhanced SVG low voltage crossing methods, belong to electrical automation equipment technical field, the method includes: after three-phase voltage synthesis is carried out to self-built voltage amplitude and self-built voltage phase, current reference value is obtained by electromagnetic equation;According to the self-built voltage phase and current reference value, bridge arm differential mode voltage modulation wave is obtained by inner ring current control;The actual value of main circuit commutation of enhanced SVG is acquired, and bridge arm common mode voltage modulation wave is obtained by circulating current suppression control in combination with the self-built voltage phase;The actual energy and rated energy of enhanced SVG are acquired, and energy modulation signal is obtained by energy control loop;According to the bridge arm differential mode voltage modulation wave, bridge arm common mode voltage modulation wave and energy modulation signal are modulated, and switching signal control enhanced SVG is generated, to realize low voltage crossing.The application can solve the problem that enhanced SVG fails or is off-grid under low voltage.

Description

TECHNICAL FIELD

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

[0002] With the acceleration of global energy transformation, the traditional power system is gradually transitioning to a new power system. The new power system takes clean energy as the core and emphasizes the wide access of renewable energy, which is usually connected to the grid through power electronic converters, lacking the frequency response provided by the rotating mechanical inertia of the generator. Moreover, due to the volatility and intermittency of renewable energy, the voltage and frequency stability of the grid is more easily affected, making the grid exhibit weak characteristics.

[0003] To adapt to the weak grid environment, on the basis of the existing reactive power compensation device (static var generator, SVG) in new energy stations, an energy storage system is integrated to reserve active power for grid inertia support, taking into account autonomous inertia response and active voltage support, forming an integrated high-performance power quality regulation device with simultaneous active and reactive power regulation capability, namely enhanced SVG (Enhanced SVG, ESVG), which quickly adjusts active and reactive power output, suppresses frequency and voltage fluctuations, and improves the voltage and frequency stability of the power system. At the same time, the new power system requires devices connected to the grid to have certain resistance to grid faults. When a short-time voltage sag occurs in the grid, if the enhanced SVG device fails or is disconnected under low voltage conditions, the frequency and voltage stability of the entire system will face serious threats, further triggering more serious cascading failures, and even leading to grid collapse.

[0004] Due to the limited ability of the inverter to suppress overcurrent, in order to ensure the safe operation of the enhanced SVG during grid short-circuit faults, it is necessary to study the low-voltage ride-through strategy of the enhanced SVG with weak grid adaptation conditions, so that it can effectively suppress transient overcurrent and instantaneous impact overcurrent while meeting the safe and stable operation of the grid fault condition, ensure the rapid stability of power output, and smoothly connect the low-voltage ride-through strategy after fault recovery and the steady-state grid connection strategy. SUMMARY

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

[0006] To achieve the above purpose, the present application adopts the following technical solutions:

[0007] In a first aspect, an enhanced SVG low-voltage ride-through method includes the following steps:

[0008] The steady-state reactive loop is converted into a transient reactive loop to obtain a self-built voltage amplitude, and the steady-state active loop is converted into a transient active loop to obtain a self-built voltage phase;

[0009] After three-phase voltage synthesis is performed according to the self-built voltage amplitude and the self-built voltage phase, a current reference value is obtained through an electromagnetic equation;

[0010] 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;

[0011] The actual value of the main circuit commutation of the enhanced SVG is obtained, and the bridge arm common mode voltage modulation wave is obtained through loop current suppression control in combination with the self-built voltage phase;

[0012] The actual energy and the rated energy of the enhanced SVG are obtained, and an energy modulation signal is obtained through an energy control loop;

[0013] After modulation is performed according to the bridge arm differential mode voltage modulation wave, the bridge arm common mode voltage modulation wave and the energy modulation signal, a switching signal is generated to control the enhanced SVG, so as to realize low voltage ride through.

[0014] In some embodiments, the step of converting the steady-state reactive loop into the transient reactive loop to obtain the self-built voltage amplitude specifically comprises:

[0015] A reactive power reference value during a fault of the enhanced SVG is determined, the reactive power reference value is subtracted from an actual reactive power of the converter, and then the result is added to a voltage amplitude after being processed through a proportional coefficient and integration in sequence, so as to obtain the self-built voltage amplitude;

[0016] When the grid voltage drop depth is greater than or equal to 0.9, the voltage amplitude is a rated voltage; and when the grid voltage drop depth is less than 0.9, the voltage amplitude is a grid-connected voltage amplitude in a fault condition.

[0017] In some embodiments, the step of converting the steady-state active loop into the transient active loop to obtain the self-built voltage phase specifically comprises:

[0018] A steady-state self-built voltage angle output by the steady-state active loop is determined, and an active power reference value during a fault of the enhanced SVG is corrected to obtain a phase correction angle;

[0019] The steady-state self-built voltage angle and the phase correction angle are added to obtain the self-built voltage phase.

[0020] In some embodiments, the electromagnetic equation is as follows:

[0021]

[0022] wherein, This represents the self-built voltage amplitude after the three-phase voltage is synthesized. This represents the grid-connected voltage amplitude under fault conditions after the three-phase voltage is synthesized. For virtual resistance, For virtual reactance, This is the reference value for the current.

[0023] In some implementations, the step of obtaining the bridge arm differential mode voltage modulation wave through inner loop current control based on the built-in voltage phase and current reference values ​​specifically includes:

[0024] The current reference value is subjected to dq transformation to obtain the d-axis current reference value and the q-axis current reference value, and the rotation angle of the dq transformation is the self-built voltage phase.

[0025] The difference between the d-axis current reference value and the measured d-axis actual current value is calculated, and the difference between the q-axis current value and the measured q-axis actual current value is also calculated. After passing through a PI regulator and undergoing cross-decoupling, the bridge arm differential mode voltage modulation wave is obtained by inverse Park transformation based on the self-built voltage phase.

[0026] In some implementations, the step of obtaining the actual commutation value of the enhanced SVG main circuit and combining it with the built-in voltage phase to obtain the bridge arm common-mode voltage modulation wave through circulating current suppression control specifically includes:

[0027] Setting the circulating current reference value of the circulating current suppression ring to 0, the actual commutation value of the main circuit of the enhanced SVG is rotated by an angle of -2. θ d -2 q -2 After transformation, the difference from the circulating reference value is calculated, and then the result is passed through a PI controller and cross-decoupled before being processed by d. -2 q -2 After inverse transformation, the common-mode voltage modulation wave of the bridge arm is obtained. θ This is a self-built voltage phase.

[0028] 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:

[0029] The difference between the actual energy and the rated energy is used to obtain a DC current reference value through a PI regulator. The difference between the DC current reference value and the measured actual DC current value is then used to obtain an energy modulation signal after passing through the PI regulator again.

[0030] Secondly, an enhanced SVG low-voltage ride-through system includes:

[0031] A self-built voltage construction module is configured to convert a steady-state reactive loop into a transient-state reactive loop to obtain a self-built voltage amplitude and convert a steady-state active loop into a transient-state active loop to obtain a self-built voltage phase;

[0032] A current reference value calculation module is configured to obtain a current reference value through an electromagnetic equation after three-phase voltage synthesis according to the self-built voltage amplitude and the self-built voltage phase;

[0033] A bridge arm differential mode voltage modulation wave construction module is configured to obtain a bridge arm differential mode voltage modulation wave through inner loop current control according to the self-built voltage phase and the current reference value;

[0034] A bridge arm common mode voltage modulation wave construction module is configured to obtain a main circuit commutation actual value of the enhanced SVG and obtain a bridge arm common mode voltage modulation wave through loop current suppression control in combination with the self-built voltage phase;

[0035] An energy modulation signal construction module is configured to obtain an actual energy and a rated energy of the enhanced SVG and obtain an energy modulation signal through an energy control loop;

[0036] A switch control module is configured to generate a switch signal to control the enhanced SVG 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, so as to realize low voltage ride through.

[0037] In a third aspect, a computer device includes a memory, a processor and a computer program stored in the memory and executable in the processor, and the processor implements the steps of the enhanced SVG low voltage ride through method when executing the computer program.

[0038] In a fourth aspect, a computer readable storage medium stores a computer program, and the computer program implements the steps of the enhanced SVG low voltage ride through method when executed by a processor.

[0039] Compared with the prior art, the application has the following beneficial effects:

[0040] The application provides an enhanced SVG low-voltage ride-through method, which converts a steady-state reactive loop into a transient-state reactive loop to obtain a self-built voltage amplitude, converts a steady-state active loop into a transient-state active loop to obtain a self-built voltage phase, and the enhanced SVG can quickly respond to phase jump at a fault moment and adapt to amplitude drop during the fault; finally, after modulation according to a bridge arm differential mode voltage modulation wave, a bridge arm common mode voltage modulation wave and an energy modulation signal, a switching signal is generated to control the enhanced SVG, which can realize overcurrent suppression while greatly shortening the phase adjustment time, ensuring stable power output, and improving the inertial support capability of the enhanced SVG device to the power grid during the fault. The application can provide double active support of power grid voltage and frequency, overcome the adverse effects of power grid faults and smoothly transition to power grid fault recovery, and solve the problem of failure or disconnection of the enhanced SVG under low voltage. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 A whole control block diagram of an enhanced SVG low-voltage ride-through method provided by the embodiment of the application;

[0042] Figure 2 A transient-state active-frequency control loop block diagram adopted by the enhanced SVG low-voltage ride-through method provided by the embodiment of the application;

[0043] Figure 3 A transient-state reactive-voltage control loop block diagram adopted by the enhanced SVG low-voltage ride-through method provided by the embodiment of the application;

[0044] Figure 4 A three-phase voltage synthesis and electromagnetic equation block diagram adopted by the enhanced SVG low-voltage ride-through method provided by the embodiment of the application;

[0045] Figure 5 A current inner loop control loop block diagram adopted by the enhanced SVG low-voltage ride-through method provided by the embodiment of the application;

[0046] Figure 6 A circulating current suppression control loop block diagram adopted by the enhanced SVG low-voltage ride-through method provided by the embodiment of the application;

[0047] Figure 7 An energy control loop block diagram adopted by the enhanced SVG low-voltage ride-through method provided by the embodiment of the application;

[0048] Figure 8 A control action flowchart of the enhanced SVG low-voltage ride-through method provided by the embodiment of the application;

[0049] Figure 9A flowchart of an enhanced SVG low voltage ride-through method provided in an embodiment of the present invention;

[0050] Figure 10 This is a schematic diagram of an enhanced SVG low voltage ride-through system provided in an embodiment of the present invention. Detailed Implementation

[0051] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings. The content described herein is for explanation rather than limitation of the present invention.

[0052] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification and claims of this invention are intended to cover a non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, systems, products, or devices.

[0053] This embodiment provides an enhanced SVG low-voltage ride-through method to address enhanced SVGs with different topologies. It adds a response to grid fault ride-through based on a stable grid-connected control strategy; it also performs amplitude adjustment and phase angle correction, as well as corresponding circuit reference value changes; while ensuring the basic function of enhanced SVG's dual active support for voltage and frequency under weak grid fault conditions, it resists excessive current surges, enabling the enhanced SVG device to operate stably under transient conditions.

[0054] like Figure 1 The diagram shows the overall control block diagram of this method. It adds a correction strategy to the original steady-state grid-connected control strategy of the enhanced SVG to adapt to the short-circuit fault condition of the power grid. Specifically, the steady-state reactive power loop is transformed into a transient reactive power loop after the reactive power reference value is changed and the amplitude is adjusted. The steady-state active power loop is transformed into a transient active power loop after the active power reference value is changed and the phase is corrected. In addition, there are electromagnetic equation loops, current inner loops, circulating current suppression loops and energy control loops that cooperate with the active power loops and reactive power loops to control the energy storage system.

[0055] like Figure 9 As shown, the enhanced SVG low-voltage ride-through method with inertial response that is adaptable to weak networks specifically includes the following steps:

[0056] S1 converts the steady-state reactive loop into a transient reactive loop to obtain the self-built voltage amplitude, and converts the steady-state active loop into a transient active loop to obtain the self-built voltage phase.

[0057] Preferred, such as Figure 3As shown, the steady-state reactive power loop is converted into a transient reactive power loop through the transformation of the reactive power reference value and the amplitude adjustment, which is specifically as follows:

[0058] On the basis of the reactive power-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 is determined as follows: Q' ref According to the amplitude of the grid-connected point voltage U and the reactive current reference value during the fault I Qref , the determination is as follows:

[0059]

[0060] wherein the reactive current reference value during the fault I Qref is modified according to the grid voltage drop depth at this time, and the grid voltage drop depth is defined as the ratio of the amplitude of the grid-connected voltage during the fault U to the rated voltage U N , and the setting of the reactive current reference value during the fault I Qref is as follows:

[0061]

[0062] wherein U N and I N are the rated voltage and the rated current, respectively, U U N represents the depth of voltage drop, which is defined to be in the range of 0.1 to 0.9. U U N Less than 0.1 is voltage interruption; U U N Greater than 0.9 is the normal range of voltage change, and the loop correction strategy during the fault does not need to be enabled, and the steady-state reactive power loop can provide the required voltage support. K i is the current coefficient, which is generally taken as 1.5.

[0063] The reactive power reference value during the fault is determined as follows: Q' ref After that, the actual reactive power of the converter Q is subtracted from it, and then it is processed through a proportional coefficient K E , and then it is processed through an integral element, and the amplitude of the voltage E ​​​0 to obtain the final self-built voltage amplitude E During the fault, the self-built voltage amplitude needs to be quickly reduced to achieve the purpose of quickly and timely reducing the enhanced SVG grid-connected voltage amplitude. The overall control of the transient reactive loop during the fault and the amplitude adjustment are as follows:

[0064]

[0065] Preferably, as shown in Figure 2 , the steady-state active loop is converted into a transient active loop by conversion of the active reference value and phase correction, which is specifically:

[0066] On the basis of the active frequency loop of the steady-state grid-connected control of the enhanced SVG, the active reference P' ref is set according to different operating conditions of the device:

[0067]

[0068] After the active reference value is corrected, the phase needs to be compensated to adapt to the phase jump under the fault condition of the grid voltage. Since the active frequency loop of the enhanced SVG device itself has a certain virtual inertia, a direct compensation method is adopted, and the phase compensation is divided into reference correction and power angle correction.

[0069] The reference correction compensation angle α is the angle between the grid-connected voltage phase and the reference phase under the fault condition, and the specific calculation method is as follows:

[0070]

[0071] wherein, U d and U q are the d-axis and q-axis components of the grid-connected voltage of the enhanced SVG in the synchronous rotating coordinate system during the fault.

[0072] The power angle correction compensation angle β is obtained according to the relationship between the active power output and the power angle, as follows:

[0073]

[0074] wherein, X v is the virtual reactance in the electromagnetic equation, that is, the equivalent reactance between the self-built voltage and the grid-connected voltage.

[0075] According to the voltage vector derivation under the fault condition, the expression of the phase correction angle θ' is:

[0076]

[0077] The steady-state active loop of the enhanced SVG realizes the adjustment of the system frequency according to the unbalance of torque or power, so that the system has inertia and damping characteristics, and the final output of the active loop is the phase angle of the self-built voltage of the enhanced SVG, and the specific expression of the loop is as follows:

[0078]

[0079] wherein, P is the actual output active power, ω 0 is the rated angular velocity, ω is the actual angular velocity, θ is the angle of the self-built voltage, J is the moment of inertia, D is the damping coefficient.

[0080] According to the modified active reference value and the phase compensation, the steady-state active loop is corrected, and the expression of the transient active loop after correction is as follows:

[0081]

[0082] At this time θ is the sum of the steady-state self-built voltage angle and the phase correction angle.

[0083] S2, according to the self-built voltage amplitude and the self-built voltage phase, the three-phase voltage synthesis is carried out, and the current reference value is obtained through the electromagnetic equation;

[0084] Preferably, as shown in Figure 4 , the current reference value obtained through the electromagnetic equation is specifically:

[0085] The self-built voltage amplitude and the self-built voltage phase of the enhanced SVG in the fault state are obtained from the transient reactive loop and the transient active loop, and the final current reference value is obtained through the electromagnetic equation as shown below, that is, the virtual resistance R v and the virtual reactance L v i ref

[0086]

[0087] wherein, is the self-built voltage amplitude after three-phase voltage synthesis, is the grid-connected voltage amplitude under the fault condition after three-phase voltage synthesis.

[0088] S3, according to the self-built voltage phase and the current reference value, the bridge arm differential mode voltage modulation wave is obtained through the inner loop current control.​​

[0089] Preferably, as shown in FIG. 2, the bridge arm differential mode voltage modulation wave obtained by the inner ring current control is specifically: Figure 5

[0090] The current reference value is rotated by an angle of i ref The dq transformation is performed to obtain the d-axis and q-axis current reference values θ i dref , i qref The current reference value is taken as the reference of the current inner loop, and is subtracted from the measured and transformed i d , i q After PI regulator and cross decoupling, the differential mode voltage modulation wave is obtained after inverse Park transformation according to the self-built voltage phase angle v diff .

[0091] S4, the actual value of the main circuit commutation of the enhanced SVG is obtained, and the bridge arm common mode voltage modulation wave is obtained by the circulating current suppression control combined with the self-built voltage phase;

[0092] Preferably, as shown in FIG. 2, the bridge arm differential mode voltage modulation wave obtained by the inner ring current control is specifically: Figure 6

[0093] The circulating current suppression loop reference value is 0, and the actual value of the main circuit circulating current of the enhanced SVG is collected i cir The dq transformation is performed to obtain the d-axis and q-axis current reference values θ -2 , -2 After PI regulator and cross decoupling, the differential mode voltage modulation wave is obtained after inverse Park transformation according to the self-built voltage phase angle -2 -2 v com .

[0094] S5, the actual energy and rated energy of the enhanced SVG are obtained, and the energy modulation signal is obtained by the energy control loop;

[0095] Preferably, as shown in FIG. 2, the bridge arm differential mode voltage modulation wave obtained by the inner ring current control is specifically: Figure 7

[0096] The actual energy and rated energy in the enhanced SVG module are subtracted, and the DC current reference value is obtained after PI regulator. Then, the actual DC current value is subtracted, and the energy modulation signal is finally obtained after PI regulator.

[0097] ​​​​​​​S6, the difference mode voltage modulation wave obtained according to the enhanced SVG transient state control v diff , the common mode voltage modulation wave obtained according to the circulating current suppression control v com , and the corresponding energy modulation signal are modulated, and finally a switching signal is generated to act on the enhanced SVG device, so that the low voltage ride through of the enhanced SVG is realized.

[0098] As shown in Figure 8 , it is a control action flow chart of the low voltage ride through method provided by the embodiment:

[0099] It is judged whether the grid voltage drop depth is less than 0.9, if not less than 0.9, it is a non-fault period, which is a normal range of voltage change, and the low voltage ride through method of the embodiment does not need to be implemented, if less than 0.9, the next step is performed;

[0100] S1, S2 and S4 in Figure 1 are switched to position 1, S3 is closed, it is judged whether the grid voltage drop depth is greater than 0.9, if not greater than 0.9, the fault is not recovered and the judgment is continued, if greater than 0.9, S4 is switched to position 0, and the next step is performed;

[0101] It is judged whether the absolute value of the self-built voltage phase is less than ε , ε which is a small positive number to prevent current shock, and can usually be taken as 1% of the rated value, if not less than ε , the waiting is continued, if less than ε , S1 and S2 are switched to position 0, and S3 is disconnected, and the control is completed.

[0102] The enhanced SVG low voltage ride through method provided by the embodiment can cope with enhanced SVGs of different topologies, increase the response to grid fault ride through on the basis of stable grid connection control strategy, simultaneously perform amplitude adjustment and phase angle correction, and change the reference value of the corresponding loop, on the basis of realizing the basic functions of voltage and frequency double active support of the enhanced SVG under the condition of guaranteeing weak grid fault, resist excessive current shock, and make the enhanced SVG device stably run under transient state.

[0103] As shown in Figure 10 , the embodiment provides an enhanced SVG low voltage ride through system, which comprises:

[0104] A self-built voltage construction module is used for converting a steady-state reactive loop into a transient-state reactive loop to obtain a self-built voltage amplitude, and converting a steady-state active loop into a transient-state active loop to obtain a self-built voltage phase;

[0105] A current reference value calculation module is configured to obtain a current reference value through an electromagnetic equation after three-phase voltage synthesis according to the self-built voltage amplitude and the self-built voltage phase;

[0106] A bridge arm differential mode voltage modulation wave construction module is configured to obtain a bridge arm differential mode voltage modulation wave through inner loop current control according to the self-built voltage phase and the current reference value;

[0107] A bridge arm common mode voltage modulation wave construction module is configured to obtain a bridge arm common mode voltage modulation wave through loop current suppression control in combination with the self-built voltage phase by acquiring an actual value of a main circuit commutation of the enhanced SVG;

[0108] An energy modulation signal construction module is configured to obtain an energy modulation signal through energy control loop by acquiring an actual energy and a rated energy of the enhanced SVG;

[0109] A switch control module is configured to generate a switch signal to control the enhanced SVG 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, so as to realize low voltage ride through.

[0110] The division of the modules in the embodiments of the present application is illustrative, and is only a logical function division; another division mode can be used in actual implementation; in addition, the function modules in each embodiment of the present application can be integrated in one processor, or can be physically separated, or two or more modules can be integrated in one module; the integrated module can be realized in the form of hardware or in the form of a software function module.

[0111] The embodiment also provides a computer device, which comprises a processor and a memory for storing a computer program (the computer program in the embodiment comprises a computing component and an iteration component, and can perform model computing and model updating), the computer program comprises program instructions, and the processor is used for executing the program instructions stored in the computer storage medium. The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc., which are the computing core and control core of the terminal, and are suitable for implementing one or more instructions, and are specifically suitable for loading and executing one or more instructions in the computer storage medium to implement a corresponding method flow or a corresponding function; the processor in the embodiment can be used for the operation of the enhanced SVG low-voltage ride-through method.

[0112] The embodiment also provides a storage medium, specifically a computer readable storage medium (Memory), which is a memory device in the computer device, and is used for storing programs and data. It can be understood that the computer readable storage medium herein can include an internal storage medium in the computer device, and of course can also include an expansion storage medium supported by the computer device. The computer readable storage medium provides a storage space, and the storage space stores an 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 the instructions can be one or more computer programs (including program codes). It should be noted that the computer readable storage medium herein can be a high-speed RAM memory, or a non-volatile memory such as at least one disk memory. One or more instructions stored in the computer readable storage medium can be loaded and executed by the processor to implement the corresponding steps of the enhanced SVG low-voltage ride-through method in the above embodiment.

[0113] Those skilled in the art will appreciate that embodiments of the application can be devised for a method, a system, or a computer program product. Accordingly, the present application can be embodied in the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code.

[0114] The present application is described in reference to the flowchart and / or block diagrams of the method, apparatus (system) and computer program product according to embodiments of the application. It will be understood that each block of the flowchart and / or block diagrams, and combinations of blocks in the flowchart and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processing device or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks.

[0115] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the function specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks.

[0116] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks.

[0117] Finally, it should be noted that the above-mentioned embodiments are merely intended for describing the technical solutions of the present application, but not for limiting it. Although the present application is described in detail with reference to the above embodiments, those skilled in the field should understand that the specific embodiments of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, and any modification or equivalent replacement without departing from the spirit and scope of the present application should be covered in the protection scope of the claims of the present application.

Claims

1. An enhanced SVG low voltage ride through method, characterized by, The method comprises the following steps: The steady-state reactive loop is converted into a transient reactive loop to obtain a self-built voltage amplitude, and the steady-state active loop is converted into a transient active loop to obtain a self-built voltage phase; After three-phase voltage synthesis is performed according to the self-built voltage amplitude and the self-built voltage phase, a current reference value is obtained through an electromagnetic equation; 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; An actual value of main circuit commutation of the enhanced SVG is obtained, and a bridge arm common mode voltage modulation wave is obtained through circulation 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 loop; After modulation is performed according to the bridge arm differential mode voltage modulation wave, the bridge arm common mode voltage modulation wave and the energy modulation signal, a switching signal is generated to control the enhanced SVG, and low voltage ride through is realized. The step of converting the steady-state reactive loop into the transient reactive loop to obtain the self-built voltage amplitude specifically comprises: A reactive power reference value during a fault of the enhanced SVG is determined, the reactive power reference value is subtracted from an actual reactive power of the converter, and then the result is sequentially processed through a proportional coefficient and integration, and then added to a voltage amplitude to obtain the self-built voltage amplitude; When a grid voltage drop depth is greater than or equal to 0.9, the voltage amplitude is a rated voltage; and when the grid voltage drop depth is less than 0.9, the voltage amplitude is a grid-connected voltage amplitude under a fault condition; The step of converting the steady-state active loop into the transient active loop to obtain the self-built voltage phase specifically comprises: A steady-state self-built voltage angle output by the steady-state active loop is determined, and an active power reference value during a fault of the enhanced SVG is corrected to obtain a phase correction angle; The steady-state self-built voltage angle and the phase correction angle are added to obtain the self-built voltage phase. The electromagnetic equation is as follows: wherein, is the self-built voltage amplitude after three-phase voltage synthesis, is the grid-connected voltage amplitude under fault conditions after three-phase voltage synthesis, is the virtual resistance, is the virtual reactance, is the current reference value.

2. The enhanced SVG low voltage ride through method of claim 1, wherein, The step of obtaining the bridge arm differential mode voltage modulation wave through the inner loop current control according to the self-built voltage phase and the current reference value specifically comprises: The current reference value is subjected to dq transformation to obtain a d-axis current reference value and a q-axis current reference value, and a rotation angle of the dq transformation is the self-built voltage phase; The d-axis current reference value is subtracted from a d-axis actual current value obtained through measurement transformation, and the q-axis current reference value is subtracted from a q-axis actual current value obtained through measurement transformation, and then the results are respectively subjected to PI regulators and cross decoupling, and then subjected to inverse Park transformation according to the self-built voltage phase to obtain the bridge arm differential mode voltage modulation wave.

3. The enhanced SVG low voltage ride through method of claim 1, wherein, The step of obtaining the bridge arm common mode voltage modulation wave through the circulation suppression control in combination with the self-built voltage phase and the actual value of main circuit commutation of the enhanced SVG specifically comprises: Let the circulating current reference value of the circulating current suppression ring be 0, and the rotating angle of the main circuit commutation actual value of the enhanced SVG be -2 θ of d -2 of q -2 After transformation, difference with the circulating current reference value, PI regulator, cross decoupling, and d -2 of q -2 After inverse transformation, the bridge arm common mode voltage modulation wave is obtained, and the θ is a self-built voltage phase.

4. The enhanced SVG low voltage ride through method of claim 1, wherein, The step of obtaining the energy modulation signal through the energy control loop after the actual energy and the rated energy of the enhanced SVG are obtained specifically comprises: The actual energy and the rated energy are subtracted from each other, and then a direct current reference value is obtained through a PI regulator, the direct current reference value is subtracted from a measured actual direct current value, and then the result is subjected to a PI regulator again to obtain the energy modulation signal.

5. An enhanced SVG low voltage ride through system characterized by, The enhanced SVG low-voltage ride-through method according to any one of claims 1-4, comprising: a self-built voltage construction module, configured to convert a steady-state reactive loop into a transient-state reactive loop to obtain a self-built voltage amplitude, and convert a steady-state active loop into a transient-state active loop to obtain a self-built voltage phase; a current reference value calculation module, configured to obtain a current reference value through an electromagnetic equation after three-phase voltage synthesis according to the self-built voltage amplitude and the self-built voltage phase; a bridge arm differential mode voltage modulation wave construction module, configured to obtain a bridge arm differential mode voltage modulation wave through inner loop current control according to the self-built voltage phase and the current reference value; a bridge arm common mode voltage modulation wave construction module, configured to obtain a main circuit commutation actual value of the enhanced SVG, and obtain a bridge arm common mode voltage modulation wave through circulation suppression control in combination with the self-built voltage phase; an energy modulation signal construction module, configured to obtain an actual energy and a rated energy of the enhanced SVG, and obtain an energy modulation signal through an energy control loop; a switch control module, configured to generate a switch signal to control the enhanced SVG 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, so as to realize low-voltage ride-through.

6. A computer device, comprising: A computer readable storage medium stores a computer program, and the computer program is executed by a processor to realize the steps of the enhanced SVG low-voltage ride-through method according to any one of claims 1-4.

7. A computer-readable storage medium, characterized in that, The computer readable storage medium stores a computer program, and the computer program is executed by a processor to realize the steps of the enhanced SVG low-voltage ride-through method according to any one of claims 1-4.

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