Network construction converter fault ride-through method, system and equipment considering current limiting requirement

Abstract

The invention discloses a network construction converter fault ride-through method, system and device considering a current limiting requirement, and the method comprises the steps: obtaining the active power and reactive power outputted by a network construction converter according to the three-phase capacitor voltage of the network construction converter and the three-phase current of an inverter side; obtaining a synchronization angle of the network construction converter according to the active power, and obtaining an internal potential amplitude of the network construction converter according to the reactive power; and obtaining dq-axis components of the three-phase capacitor voltage in a synchronous rotating coordinate system according to the synchronous angle, obtaining a dq-axis instruction of the current of the grid-forming converter by combining the internal potential amplitude, performing PI control to obtain an initial modulation voltage, subtracting the initial modulation voltage from the voltage drop of the transient virtual resistor to obtain a modulation voltage meeting the current limiting requirement, and performing SVPWM control to obtain the current limiting current of the grid-forming converter. And obtaining a switch control signal of the network construction converter. According to the method, the steady-state operation of the grid-forming converter is not influenced while fault ride-through is completed under the condition that the inverter is not over-current in the transient state, and the reliability and the effectiveness are ensured under a relatively deep voltage drop fault.

Description

Technical Field

[0001] This invention belongs to the field of converter control technology, specifically relating to a fault ride-through method, system and equipment for grid-connected converters that takes current limiting requirements into account. Background Technology

[0002] With the widespread integration of wind, solar, and energy storage renewable energy sources, the power system is gradually evolving into a new type of power system dominated by converters. Grid-connected converter control schemes have received extensive research and attention due to their ability to provide frequency and voltage support for power systems with a high proportion of renewable energy. Unlike conventional grid-connected converters, grid-connected converters employ power synchronization and voltage control modes, enabling them to independently establish voltage and operate in islanded mode. Even in grid-connected mode, they can support the voltage and frequency of the grid, making them a key technology for future power system development. However, unlike traditional synchronous generator technology, the overcurrent capacity of grid-connected converters is quite limited. When grid faults occur, grid-connected converters still face transient stability issues and the challenge of overcurrent under fault conditions, which is detrimental to the stable operation of inverter equipment and the power system.

[0003] This case arose in response to the problems of overcurrent and instability that exist in existing grid-type converter technology under transient faults. Summary of the Invention

[0004] The purpose of this invention is to provide a fault ride-through method, system, and device for grid-connected converters that takes current limiting requirements into account. This ensures that the fault ride-through is completed without affecting the steady-state operation of the grid-connected converter, while ensuring reliability and effectiveness under deep voltage dip faults, without causing the inverter to experience transient current outages.

[0005] To achieve the above objectives, the solution of the present invention is:

[0006] A fault ride-through method for grid converters considering current limiting requirements includes,

[0007] Based on the components of the three-phase capacitor voltage of the grid converter and the three-phase current on the inverter side in the stationary α-β coordinate system, the active power and reactive power output by the grid converter are obtained.

[0008] The synchronization angle of the grid converter is obtained based on its active power; the internal potential amplitude of the grid converter is obtained based on its reactive power.

[0009] Based on the synchronization angle of the grid converter, the dq-axis components of the three-phase capacitor voltage in the synchronous rotating coordinate system are obtained;

[0010] Based on the internal potential amplitude of the grid converter and the dq-axis components of the three-phase capacitor voltage in the synchronous rotating coordinate system, the dq-axis command of the grid converter current is obtained.

[0011] Based on the dq axis command of the grid converter current, PI control is performed to obtain the initial modulation voltage of the grid converter. The initial modulation voltage is subtracted from the voltage drop of the transient virtual resistor to obtain the modulation voltage that meets the current limiting requirement.

[0012] SVPWM control is performed based on the modulation voltage that meets the current limiting requirements to obtain the switching control signal of the grid converter.

[0013] Specifically, based on the components of the three-phase capacitor voltage of the grid converter and the three-phase current on the inverter side in the stationary α-β coordinate system, the active power and reactive power output of the grid converter are obtained, including...

[0014] Obtain the three-phase capacitor voltage V of the grid converter ca V cb V cc and the three-phase current I on the inverter side a ,I b ,I c ;

[0015] The acquired data was subjected to Clark transformation to obtain the α-axis component V of the three-phase capacitor voltage in the stationary α-β coordinate system. cα and β-axis component V cβ And the α-axis component I of the three-phase current in the stationary α-β coordinate system. α and β-axis component I β ;

[0016] Based on the components in the stationary α-β coordinate system, the active and reactive power outputs of the grid converter are obtained using the following formula.

[0017]

[0018] Where P is the active power output of the grid-connected converter, and Q is the reactive power output of the grid-connected converter. The synchronization angle of the grid-connected converter is obtained based on its active power, including by determining the amplitude V of the grid-connected converter capacitor voltage. c(mag) The active power reference value P of the outer power loop is obtained. ref ,

[0019] P ref =P0-K fp (V n -V c(mag) )

[0020] Where P0 is the active power setpoint during steady-state operation, and K fp It is the feedback coefficient of the voltage difference, V n It is the peak value of the rated phase voltage of the grid converter;

[0021] Based on the inertia J and damping coefficient D of the grid converter, the synchronization angle of the grid converter can be calculated using the following formula.

[0022]

[0023] Where ω is the actual output angular frequency of the grid converter, ω n θ is the rated angular frequency of the grid converter, P is the active power output of the grid converter, and θ is the synchronization angle of the grid converter.

[0024] This also includes limiting the synchronization angle of the grid converter in conjunction with current limiting requirements, including...

[0025] Based on the maximum reference value of d-axis current i dref(lim) The synchronization angle limit δ is obtained. v(lim) ,

[0026]

[0027] Among them, X v This is the virtual reactance value;

[0028] Based on the output voltage angle θ of the grid converter pll ,get

[0029] θ ref =min(θ-θ) pll ,δ v(lim) )+θ pll .

[0030] Where, θ pll It is the output voltage angle obtained by the phase-locked loop, δ v(lim) It is the maximum power angle difference that satisfies the current limiting requirement, θ ref It is the synchronization angle of the grid converter.

[0031] Specifically, based on the reactive power of the grid-connected converter, the internal potential amplitude of the grid-connected converter is obtained, including...

[0032] The internal potential amplitude of the grid converter can be obtained according to the following formula.

[0033] V dref =V n +k q (Q ref -Q)

[0034] V qref =0

[0035] Among them, V dref and V qref These are the reference values ​​for the dq-axis components of the internal potential of the grid converter, V. nQ is the peak value of the rated phase voltage of the inverter. ref Given a reactive power reference value, k q This is the reactive power loop droop coefficient.

[0036] Specifically, based on the internal potential amplitude of the grid-connected converter and the dq-axis components of the three-phase capacitor voltage in the synchronous rotating coordinate system, the dq-axis command of the grid-connected converter current is obtained, including:

[0037] According to the following formula,

[0038]

[0039] Among them, V cd and V cq These are the dq-axis components of the three-phase capacitor voltage, L v For virtual inductance, R v For virtual admittance, I dref and I qref These are the dq-axis reference values ​​for the grid converter current, V. dref and V qref These are the reference values ​​for the dq-axis components of the internal potential of the grid converter, respectively.

[0040] The dq-axis reference value of the grid converter current satisfies the following constraints.

[0041]

[0042] in, This is the reference value for the d-axis current after limiting. I is the reference value for the q-axis current after limiting. max This represents the maximum current amplitude.

[0043] A grid converter fault ride-through system considering current limiting requirements includes,

[0044] The power acquisition module is configured to obtain the active power and reactive power output by the grid converter based on the components of the three-phase capacitor voltage of the grid converter and the three-phase current on the inverter side in the stationary α-β coordinate system.

[0045] The synchronization angle acquisition module is configured to obtain the synchronization angle of the grid converter based on the active power of the grid converter.

[0046] The internal potential amplitude acquisition module is configured to obtain the internal potential amplitude of the grid converter based on the reactive power of the grid converter;

[0047] The three-phase capacitor voltage dq-axis component acquisition module is configured to obtain the dq-axis components of the three-phase capacitor voltage in the synchronous rotating coordinate system based on the synchronization angle of the grid converter.

[0048] The current dq axis command acquisition module is configured to obtain the dq axis command of the grid converter current based on the internal potential amplitude of the grid converter and the dq axis components of the three-phase capacitor voltage in the synchronous rotating coordinate system.

[0049] The modulation voltage acquisition module is configured to perform PI control based on the dq-axis command of the grid converter current to obtain the initial modulation voltage of the grid converter, subtract the voltage drop of the transient virtual resistor from the initial modulation voltage to obtain the modulation voltage that meets the current limiting requirements; and,

[0050] The control signal acquisition module is configured to perform SVPWM control based on the modulation voltage that meets the current limiting requirements to obtain the switching control signal of the grid converter.

[0051] The power acquisition module obtains the active and reactive power output of the grid-connected converter based on the components of the three-phase capacitor voltage and the three-phase current on the inverter side in the stationary α-β coordinate system.

[0052] Obtain the three-phase capacitor voltage V of the grid converter ca V cb V cc and the three-phase current I on the inverter side a ,I b ,I c ;

[0053] The acquired data was subjected to Clark transformation to obtain the α-axis component V of the three-phase capacitor voltage in the stationary α-β coordinate system. cα and β-axis component V cβ And the α-axis component I of the three-phase current in the stationary α-β coordinate system. α and β-axis component I β ;

[0054] Based on the components in the stationary α-β coordinate system, the active and reactive power outputs of the grid converter are obtained using the following formula.

[0055]

[0056] Where P is the active power output of the grid converter and Q is the reactive power output of the grid converter.

[0057] The synchronization angle acquisition module obtains the synchronization angle of the grid-connected converter based on its active power, including...

[0058] Based on the voltage amplitude V of the grid converter capacitor c(mag) The active power reference value P of the outer power loop is obtained. ref ,

[0059] P ref =P0-K fp (V n -V c(mag) )

[0060] Where P0 is the active power setpoint during steady-state operation, and K fp It is the feedback coefficient of the voltage difference, V n It is the peak value of the rated phase voltage of the grid converter;

[0061] Based on the inertia J and damping coefficient D of the grid converter, the synchronization angle of the grid converter can be calculated using the following formula.

[0062]

[0063] Where ω is the actual output angular frequency of the grid converter, ω n θ is the rated angular frequency of the grid converter, P is the active power output of the grid converter, and θ is the synchronization angle of the grid converter.

[0064] The synchronization angle acquisition module further includes limiting the synchronization angle of the grid converter in accordance with current limiting requirements, including...

[0065] Based on the maximum reference value of d-axis current i dref(lim) The synchronization angle limit δ is obtained. v(lim) ,

[0066]

[0067] Among them, X v This is the virtual reactance value;

[0068] Based on the output voltage angle θ of the grid converter pll ,get

[0069] θ ref =min(θ-θ) pll ,δ v(lim) )+θ pll .

[0070] Where, θ pll It is the output voltage angle obtained by the phase-locked loop, δ v(lim) It is the maximum power angle difference that satisfies the current limiting requirement, θ ref It is the synchronization angle of the grid converter.

[0071] The internal potential amplitude acquisition module obtains the internal potential amplitude of the grid-connected converter based on the reactive power of the grid-connected converter, including:

[0072] The internal potential amplitude of the grid converter can be obtained according to the following formula.

[0073] V dref =V n +k q (Q ref -Q)

[0074] V qref =0

[0075] Among them, V dref and V qref These are the reference values ​​for the dq-axis components of the internal potential of the grid converter, V. n Q is the peak value of the rated phase voltage of the inverter. ref Given a reactive power reference value, k q This is the reactive power loop droop coefficient.

[0076] The current dq-axis command acquisition module obtains the dq-axis command of the grid-connected converter current based on the internal potential amplitude of the grid-connected converter and the dq-axis components of the three-phase capacitor voltage in the synchronous rotating coordinate system, including:

[0077] According to the following formula,

[0078]

[0079] Among them, V cd and V cq These are the dq-axis components of the three-phase capacitor voltage, L v For virtual inductance, R v For virtual admittance, I dref and I qref These are the dq-axis reference values ​​for the grid converter current, V. dref and V qref These are the reference values ​​for the dq-axis components of the internal potential of the grid converter, respectively.

[0080] The dq-axis reference value of the grid converter current satisfies the following constraints.

[0081]

[0082] in, This is the reference value for the d-axis current after limiting. I is the reference value for the q-axis current after limiting. max This represents the maximum current amplitude.

[0083] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor; when the processor executes the computer program, it implements the steps of the grid converter fault ride-through method considering current limiting requirements as described above.

[0084] A computer-readable storage medium storing a computer program; when executed by a processor, the computer program implements the steps of the grid converter fault ride-through method considering current limiting requirements as described above.

[0085] After adopting the above solution, the beneficial effects of the present invention compared with the prior art are as follows:

[0086] 1) This invention provides overcurrent protection for overcurrent at different time scales in multiple control loops, including power angle limiting and power reference adjustment in the power control loop, as well as ring current limiter and virtual resistor in the voltage and current inner loop, which ensures the reliability and comprehensiveness of current limiting. At the same time, it can ensure that the grid-type converter does not become unstable in the case of extremely low voltage ride-through faults, and can quickly recover to the stable operating state before the fault after the fault.

[0087] 2) This invention only operates when a transient overcurrent occurs in the converter system. In steady state, since the output voltage and synchronization angle reference are within a stable range, no extra feedback signals are introduced. None of the components will affect the power, voltage and current references during normal operation. It is more friendly to parameter design and system stability analysis in steady state.

[0088] 3) This invention employs a simple parameter design. In the outer loop of power control, grid-side faults are primarily reflected through the difference in output voltage. Voltage feedback adjusts the transient power reference value, deeply compensating for transient power imbalances to prevent divergence and oscillation of the converter synchronization angle. It avoids the use of fault-based control structures and parameter switching. Limiting the rise rate of the feedback voltage signal allows it to adapt to deep grid faults without complex parameter design. The active power loop output synchronization angle reference utilizes the angle comparison and limitation of a phase-locked loop, enabling rapid and reliable response during transients without affecting the converter's steady-state operation. This invention eliminates the need for grid-side fault diagnosis or reliance on other information, avoids control structure switching, and prevents adjustments to steady-state control parameters, thus avoiding instability and malfunctions caused by control switching.

[0089] 4) Under various grid connection conditions (short-circuit ratio SCR = 2 to 30), this grid-type converter strategy can play a role and is applicable to various types of grid-side faults. When a deep fault occurs on the grid side, it can ensure the reliability of current limiting and the ability to ride through the fault, while preventing transient overcurrent. It provides reliable equipment for building a new power system with new energy sources as the main body. Attached Figure Description

[0090] Figure 1 This is a block diagram of the grid converter control system with integrated current limiting mechanism of the present invention;

[0091] Figure 2It is the low voltage ride-through (V) of the grid converter. g Simulation waveform of 0.2 pu;

[0092] Figure 3 It is the zero-voltage ride-through (V) of the grid converter. g The simulation waveform of (=0). Detailed Implementation

[0093] This invention provides a fault ride-through method for grid converters considering current limiting requirements, comprising:

[0094] Based on the components of the three-phase capacitor voltage of the grid converter and the three-phase current on the inverter side in the stationary α-β coordinate system, the active power and reactive power output by the grid converter are obtained.

[0095] The synchronization angle of the grid converter is obtained based on its active power; the internal potential amplitude of the grid converter is obtained based on its reactive power.

[0096] Based on the synchronization angle of the grid converter, the dq-axis components of the three-phase capacitor voltage in the synchronous rotating coordinate system are obtained;

[0097] Based on the internal potential amplitude of the grid converter and the dq-axis components of the three-phase capacitor voltage in the synchronous rotating coordinate system, the dq-axis command of the grid converter current is obtained.

[0098] Based on the dq axis command of the grid converter current, PI control is performed to obtain the initial modulation voltage of the grid converter. The initial modulation voltage is subtracted from the voltage drop of the transient virtual resistor to obtain the modulation voltage that meets the current limiting requirement.

[0099] SVPWM control is performed based on the modulation voltage that meets the current limiting requirements to obtain the switching control signal of the grid converter.

[0100] like Figure 1 As shown in the figure, an embodiment of the present invention provides a fault ride-through method for a grid converter considering current limiting requirements, comprising the following steps:

[0101] (1) Use a voltage Hall sensor to collect the three-phase voltage V on the capacitor of the grid converter. ca ~V cc The three-phase current I on the switching side of the grid converter is collected using a current Hall sensor. a ~I c ;

[0102] Using Clark transformation to analyze the three-phase capacitor voltage V ca ~V cc and three-phase current I a ~I cPerforming the Clark transformation, we obtain the α-axis component V of the three-phase capacitor voltage in the stationary α-β coordinate system. cα and β-axis component V cβ and the α-axis component I of the three-phase current in the stationary α-β coordinate system α and β-axis component I β The Clark transform formula is as follows:

[0103]

[0104] Based on the α-β components of the three-phase voltage and three-phase current in the stationary coordinate system, the active and reactive power expressions of the grid-connected converter can be obtained as follows:

[0105]

[0106] (2) The key feature of grid-connected converters is that they can provide support for the frequency and voltage of the power grid. This support is mainly achieved through power control. A control strategy that couples active power control with grid frequency is established. The frequency of grid-connected converters is formed by active power through inertia and damping. Unlike grid-connected converters with no steady-state error control, the active power of grid-connected converters is controlled with error when the grid frequency changes. The relationship between the active power of grid-connected converters and synchronous angular frequency can be expressed as follows:

[0107]

[0108] Where: P ref ω is the active power setpoint of the outer power loop, J is the inertia of the grid converter, and D is the damping coefficient of the grid converter; n ω is the rated angular frequency of the grid converter, ω is the actual output angular frequency of the grid converter, and θ is the synchronization angle of the grid converter.

[0109] Reactive power control needs to provide some support when the grid voltage amplitude changes, so the relationship between the internal potential of the grid converter and reactive power is as follows:

[0110] V dref =V n +k q (Q ref -Q)

[0111] V qref =0

[0112] Where: V dref and V qref These are the reference values ​​for the dq-axis components of the internal potential of the grid converter, V. n Q is the peak value of the rated phase voltage of the grid converter. ref Given a reactive power reference value, kq This is the reactive power loop droop coefficient; the reason for directly setting the q-axis component of the internal potential to zero is to ensure that the control coordinate system is oriented according to the internal potential vector.

[0113] (3) When a fault occurs on the grid side, the output voltage of the grid converter will decrease, and the output power capability will decline. If the power command is not adjusted in time, the converter is prone to overcurrent or out-of-synchronization oscillation due to insufficient output power. Therefore, the power reference value P is adjusted by the per-unit value of the decrease in the amplitude of the output voltage. ref The expression is adjusted as follows:

[0114] P ref =P0-K fp (V n -V c(mag) )

[0115] Where: P0 is the active power setpoint during steady-state operation, K fp It is the feedback coefficient of the voltage difference, V n It is the rated output voltage of the grid converter; V c(mag) It is the amplitude of the output capacitor voltage of the grid converter. K fp Typically designed to be 1 p.u., meaning that a 1 p.u. drop in voltage amplitude corresponds to a 1 p.u. drop in the power reference value. During steady-state operation, since the output voltage is the same as the rated voltage, the feedback difference is 0, not affecting the accurate output of normal power. When a fault occurs, the voltage drops and the power reference value also drops, preventing the converter from outputting high power at low voltage and causing overcurrent. When the fault is recovered, since the converter first needs to restore normal voltage and power angle output, the power reference value should not quickly recover to a large value. Therefore, a rising-edge rate slew rate is added to the feedback voltage difference signal, changing the originally step-like power command recovery to a ramp-up, which helps the converter return to a stable operating state after the fault is recovered.

[0116] (4) The synchronization angle of the grid-connected converter is crucial for its normal and stable operation. During a fault, power imbalance or a sudden change in the grid-side phase angle can cause the synchronization angle to continuously increase, eventually leading to overcurrent in the converter and a large fluctuation process of losing synchronization with the grid. In order to achieve fault ride-through of the converter during a fault and prevent overcurrent, the synchronization angle generated by the active power loop mentioned in (2) is limited. Since determining synchronization requires obtaining the difference between the converter and grid-side angles, the angle of the output voltage is obtained using a phase-locked loop, and the difference between the output voltage angle and the converter angle is used for limitation. The expression is as follows:

[0117] θ ref =min(θ-θ) pll ,δ v(lim) )+θpll

[0118] Where, θ pll It is the output voltage angle obtained by the phase-locked loop, δ v(lim) It is the maximum power angle difference that satisfies the current limiting requirement, θ ref The synchronization angle of the grid converter can be calculated based on the output voltage-current vector relationship and the current limit value, using the following formula:

[0119]

[0120] Among them, X v It is the virtual reactance value, i dref(lim) This is the maximum reference value for the d-axis current under current limiting requirements.

[0121] (5) Obtain the dq axis components of the three-phase voltage, three-phase capacitor voltage and three-phase current at the common coupling point in the synchronous rotating coordinate system according to the following formula;

[0122]

[0123] Among them, V pcca V pccb V pccc These are the three-phase voltages at the common coupling point, V ca V cb V cc These are the three-phase voltages of the grid converter capacitors, I a ,I b ,I c These are the three-phase currents of the grid converter.

[0124] Having obtained the dq-axis components of the internal electromotive force (EMF) and the three-phase capacitor voltages in a synchronous rotating coordinate system, the next step is to obtain the dq-axis current command on the switching side of the grid converter. According to the standard specifications for grid converters, they exhibit the characteristics of a voltage source with series impedance. Therefore, based on the dq-axis components of the internal EMF and the capacitor voltages, the dq-axis current command on the switching side of the grid converter can be obtained as follows:

[0125]

[0126] Where: V cd and V cq These are the dq-axis components of the capacitor voltage, L v For virtual inductance, R v For virtual admittance, I dref and I qref These are the dq axis reference values ​​for the inverter current, respectively.

[0127] To prevent overcurrent in the converter, the reference value of the current is also limited in this stage. A ring current limiter is used, which limits the amplitude of the current synthesized from the dq-axis components to not exceeding the maximum current I. max The expression is:

[0128]

[0129] in, This represents the reference value of the d-axis current after limiting. This indicates the reference value of the q-axis current after limiting.

[0130] (6) After obtaining the dq-axis current command of the grid-connected converter and the dq-axis components of the actual three-phase current, the modulation voltage of the grid-connected converter is generated through a PI controller. Subsequently, the component V in the abc coordinate system is obtained through inverse Park transformation based on the dq voltage command of the synchronous rotating coordinate system. a V b V c To further limit the current, the voltage drop under the transient virtual resistance is subtracted from the obtained voltage reference component in the abc coordinate system. This step utilizes current feedback, and the expression is:

[0131]

[0132] Where: V mabc and R represents the modulation voltage before and after meeting the current limiting requirement, respectively. vfault It is a transient virtual impedance, V c(mag) and I (mag) These represent the amplitudes of the converter output voltage and current, respectively, and t is the time the virtual transient resistor is connected. This virtual resistor control complements the speed of current limiting and has a good suppression effect on short-timescale overcurrents.

[0133] Finally, a set of PWM signals is constructed using SVPWM technology to control the switching of power switching devices in the grid converter.

[0134] The following is a simulation of the grid converter controlled by this fault ride-through scheme; for example... Figure 2 As shown, SCR = 30, post-fault voltage V g When the voltage is 0.2 pu, using this integrated control scheme, under strong grid conditions, a low-voltage fault occurs and lasts for 0.5 seconds. The grid-connected converter system does not experience overcurrent, and voltage, current, and frequency do not fluctuate significantly during the fault. The waveforms demonstrate that this scheme ensures reliable current limiting and synchronous stability, and allows the grid-connected converter to quickly return to normal operation after the fault, completing fault ride-through. Furthermore, Figure 3This demonstrates zero-voltage ride-through (V) using this integrated control scheme under the same conditions. g The effect of =0) can ensure that the grid-type converter can recover to a stable state after a fault, further verifying the reliability of the current limiting scheme.

[0135] This invention also provides a grid converter fault ride-through system considering current limiting requirements, comprising:

[0136] The power acquisition module is configured to obtain the active power and reactive power output by the grid converter based on the components of the three-phase capacitor voltage of the grid converter and the three-phase current on the inverter side in the stationary α-β coordinate system.

[0137] The synchronization angle acquisition module is configured to obtain the synchronization angle of the grid converter based on the active power of the grid converter.

[0138] The internal potential amplitude acquisition module is configured to obtain the internal potential amplitude of the grid converter based on the reactive power of the grid converter;

[0139] The three-phase capacitor voltage dq-axis component acquisition module is configured to obtain the dq-axis components of the three-phase capacitor voltage in the synchronous rotating coordinate system based on the synchronization angle of the grid converter.

[0140] The current dq axis command acquisition module is configured to obtain the dq axis command of the grid converter current based on the internal potential amplitude of the grid converter and the dq axis components of the three-phase capacitor voltage in the synchronous rotating coordinate system.

[0141] The modulation voltage acquisition module is configured to perform PI control based on the dq-axis command of the grid converter current to obtain the initial modulation voltage of the grid converter, subtract the voltage drop of the transient virtual resistor from the initial modulation voltage to obtain the modulation voltage that meets the current limiting requirements; and,

[0142] The control signal acquisition module is configured to perform SVPWM control based on the modulation voltage that meets the current limiting requirements to obtain the switching control signal of the grid converter.

[0143] This invention also provides another computer device, including a processor and a memory configured to store a computer program capable of running on the processor; wherein, when the processor is configured to run the computer program, it performs the method steps described in the foregoing embodiments.

[0144] In practical applications, the aforementioned processor includes a Field-Programmable Gate Array (FPGA), and the processor can be a Central Processing Unit (CPU) or a Digital Signal Processor (DSP). It is understood that for different devices, the electronic devices used to implement the functions of the aforementioned processor can also be other types, and this embodiment of the invention does not impose specific limitations.

[0145] The aforementioned memory can be volatile memory, such as random-access memory (RAM); or non-volatile memory, such as read-only memory (ROM), flash memory, hard disk drive (HDD), or solid-state drive (SSD); or a combination of the above types of memory, and provides instructions and data to the processor.

[0146] In an exemplary embodiment, the present invention also provides a computer-readable storage medium for storing a computer program.

[0147] Optionally, the computer-readable storage medium can be applied to any of the methods in the embodiments of the present invention, and the computer program causes the computer to execute the corresponding processes implemented by the processor in the various methods of the embodiments of the present invention. For the sake of brevity, these will not be described in detail here.

[0148] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can 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. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0149] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations 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 processor, 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, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0150] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0151] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0152] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0153] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for grid-forming converter fault ride-through considering current limiting requirements, characterized in that: The method comprises the following steps: According to the components of the three-phase capacitor voltage of the grid-connected converter and the three-phase current on the inverter side in the static α-β coordinate system, the active power and the reactive power output by the grid-connected converter are obtained; According to the active power of the grid-connected converter, the synchronous angle of the grid-connected converter is obtained; according to the reactive power of the grid-connected converter, the internal potential amplitude of the grid-connected converter is obtained; According to the synchronous angle of the grid-connected converter, the dq-axis components of the three-phase capacitor voltage in the synchronous rotating coordinate system are obtained; According to the internal potential amplitude of the grid-connected converter and the dq-axis components of the three-phase capacitor voltage in the synchronous rotating coordinate system, the dq-axis instruction of the grid-connected converter current is obtained; According to the dq-axis instruction of the grid-connected converter current, PI control is performed to obtain the initial modulation voltage of the grid-connected converter, and the initial modulation voltage is subtracted by the voltage drop of the transient virtual resistance to obtain the modulation voltage meeting the current limiting requirement; According to the modulation voltage meeting the current limiting requirement, SVPWM control is performed to obtain the switching control signal of the grid-connected converter.

2. The method of claim 1, wherein: According to the components of the three-phase capacitor voltage of the grid-connected converter and the three-phase current on the inverter side in the static α-β coordinate system, the active power and the reactive power output by the grid-connected converter are obtained, comprising: Obtaining three-phase capacitor voltages V of the network-forming converter ca , cb , cc and three-phase currents I of the inverter side a , b , c ; The obtained data is subjected to Clark transformation to obtain the α-axis component V cα and the β-axis component V cβ of the three-phase capacitor voltage in the stationary α-β coordinate system, and the α-axis component I α and the β-axis component I β of the three-phase current in the stationary α-β coordinate system; According to the components in the static α-β coordinate system, the active power and the reactive power output by the grid-connected converter are obtained by using the following formula: Wherein, P is the active power output by the grid-connected converter, and Q is the reactive power output by the grid-connected converter.

3. The method of claim 1, wherein: According to the active power of the grid-connected converter, the synchronous angle of the grid-connected converter is obtained, comprising: According to the network-constructed converter capacitor voltage amplitude V c(mag) , the active power reference value P ref of the power outer loop is obtained, P ref = P0- K fp (V n - V c(mag) ) wherein P0 is the active power setpoint at steady state, K fp is the feedback coefficient of the voltage difference, V n is the rated phase voltage peak value of the grid-forming converter; According to the inertia J and the damping coefficient D of the grid-connected converter, the synchronous angle of the grid-connected converter is calculated by using the following formula: where ω is the actual output angular frequency of the grid-forming converter, ω n is the rated angular frequency of the grid-forming converter, P is the active power output by the grid-forming converter; and θ is the synchronization angle of the grid-forming converter.

4. The method of claim 3, wherein: Further comprising, the synchronous angle of the grid-connected converter is limited in combination with the current limiting requirement, comprising: According to the d-axis current maximum reference value i dref(lim) , the synchronous angle limit δ v(lim) , wherein X v is a virtual reactance value; According to the output voltage angle θ of the networked converter pll , the following is obtained θ ref = min(θ - θ pll , δ v(lim) ) + θ pll . Wherein, θ pll is the output voltage angle obtained by the phase-locked loop, δ v(lim) is the maximum power angle difference meeting the current limiting requirement, θ ref is the synchronization angle of the grid-connected converter.

5. The method of claim 1, wherein: According to the reactive power of the grid-connected converter, the internal potential amplitude of the grid-connected converter is obtained, comprising: According to the following formula, the internal potential amplitude of the grid-connected converter is obtained: V dref = V n + k q (Q ref - Q) V qref ＝0 wherein V dref and V qref are the inner potential dq-axis component reference values of the network-forming converter, V n is the rated phase voltage peak value of the inverter, Q ref is the given reactive power reference value, k q is the reactive power droop coefficient.

6. The method of claim 1, wherein: According to the internal potential amplitude of the grid-connected converter and the dq-axis components of the three-phase capacitor voltage in the synchronous rotating coordinate system, the dq-axis instruction of the grid-connected converter current is obtained, comprising: According to the following formula: wherein V cd and V cq are the dq-axis components of the three-phase capacitor voltage, L v is a virtual inductance, R v is a virtual admittance, I dref and I qref are the dq-axis reference values of the grid forming converter current, V dref and V qref are the dq-axis component reference values of the internal potential of the grid forming converter; The dq-axis reference value of the grid-connected converter current meets the following limitation: wherein, is the d-axis current reference value after clipping, is the q-axis current reference value after clipping, I max is the maximum current amplitude.

7. A grid-forming converter fault ride-through system considering current limiting requirements, characterized by: Comprising: The power acquisition module is configured to obtain the active power and the reactive power output by the grid-connected converter according to the components of the three-phase capacitor voltage of the grid-connected converter and the three-phase current on the inverter side in the static α-β coordinate system; The synchronous angle acquisition module is configured to obtain the synchronous angle of the grid-connected converter according to the active power of the grid-connected converter; The internal potential amplitude acquisition module is configured to obtain the internal potential amplitude of the grid-connected converter according to the reactive power of the grid-connected converter; The three-phase capacitor voltage dq-axis component acquisition module is configured to obtain the dq-axis components of the three-phase capacitor voltage in the synchronous rotating coordinate system according to the synchronous angle of the grid-connected converter; The current dq-axis instruction acquisition module is configured to obtain the dq-axis instruction of the grid-connected converter current according to the internal potential amplitude of the grid-connected converter and the dq-axis components of the three-phase capacitor voltage in the synchronous rotating coordinate system; The modulated voltage obtaining module is configured to perform PI control according to the dq-axis instruction of the grid-connected converter current to obtain an initial modulated voltage of the grid-connected converter, subtract the voltage drop of the transient virtual resistance from the initial modulated voltage to obtain a modulated voltage satisfying the current limiting requirement; and The control signal obtaining module is configured to perform SVPWM control according to the modulated voltage satisfying the current limiting requirement to obtain a switching control signal of the grid-connected converter.

8. The system of claim 7, wherein: The power obtaining module obtains active power and reactive power output by the grid-connected converter according to three-phase capacitor voltages of the grid-connected converter and components of three-phase currents on the static α-β coordinate system of the inverter side, and includes Obtaining three-phase capacitor voltages V of the network-forming converter ca cb cc and three-phase currents I of the inverter side a b c ;​​​​ The obtained data is subjected to Clark transformation to obtain the α-axis component V cα and the β-axis component V cβ of the three-phase capacitor voltage in the stationary α-β coordinate system, and the α-axis component I α and the β-axis component I β of the three-phase current in the stationary α-β coordinate system; The active power and the reactive power output by the grid-connected converter are obtained according to the components on the static α-β coordinate system by using the following formula, wherein P is the active power output by the grid-connected converter, and Q is the reactive power output by the grid-connected converter.

9. The method of claim 7, wherein: The synchronous angle obtaining module obtains a synchronous angle of the grid-connected converter according to the active power of the grid-connected converter, and includes According to the network-constructed converter capacitor voltage amplitude V c(mag) , the active power reference value P ref of the power outer loop is obtained, P ref = P0- K fp (V n -V c(mag) ) wherein P0 is the active power setpoint at steady state, K fp is the feedback coefficient of the voltage difference, V n is the rated phase voltage peak value of the grid-forming converter; The synchronous angle of the grid-connected converter is calculated by using the following formula according to an inertia J and a damping coefficient D of the grid-connected converter, where ω is the actual output angular frequency of the grid-forming converter, ω n is the rated angular frequency of the grid-forming converter, P is the active power output by the grid-forming converter; and θ is the synchronization angle of the grid-forming converter.

10. The system of claim 9, wherein: The synchronous angle obtaining module further includes limiting the synchronous angle of the grid-connected converter in combination with the current limiting requirement, and includes According to the d-axis current maximum reference value i dref(lim) , the synchronous angle limit δ v(lim) , wherein X v is a virtual reactance value; According to the output voltage angle θ of the network-forming converter pll , the following is obtained θ ref = min(θ - θ pll , δ v(lim) ) + θ pll . Wherein, θ pll is the output voltage angle obtained by the phase-locked loop, δ v(lim) is the maximum power angle difference meeting the current limiting requirement, θ ref is the synchronization angle of the grid-connected converter.

11. The system of claim 7, wherein: The internal potential amplitude obtaining module obtains an internal potential amplitude of the grid-connected converter according to the reactive power of the grid-connected converter, and includes The internal potential amplitude of the grid-connected converter is obtained according to the following formula, V dref = V n + k q (Q ref - Q) V qref ＝0 wherein V dref and V qref are the internal potential dq-axis component reference values of the network-forming converter, V n is the rated phase voltage peak value of the inverter, Q ref is the given reactive power reference quantity, k q is the reactive ring droop coefficient.

12. The system of claim 7, wherein: The current dq-axis instruction obtaining module obtains a dq-axis instruction of the grid-connected converter current according to the internal potential amplitude of the grid-connected converter and dq-axis components of three-phase capacitor voltages on the synchronous rotating coordinate system, and includes According to the following formula, wherein V cd and V cq are the dq-axis components of the three-phase capacitor voltage, L v is a virtual inductance, R v is a virtual admittance, I dref and I qref are the dq-axis reference values of the grid-forming converter current, V dref and V qref are the dq-axis component reference values of the internal potential of the grid-forming converter; The dq-axis reference value of the grid-connected converter current satisfies the following limitation, wherein, is the limited d-axis current reference value, is the limited q-axis current reference value, I max is the maximum current amplitude.

13. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor; characterized in that: The processor executes the computer program to realize the steps of the grid-connected converter fault ride-through method considering the current limiting requirement according to any one of claims 1 to 6. 14.A computer readable storage medium, storing a computer program; characterized in that: The computer program is executed by the processor to realize the steps of the grid-connected converter fault ride-through method considering the current limiting requirement according to any one of claims 1 to 6.

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