Inverter Fault Ride-Through Method, Device, Control Equipment, Storage Medium and Product

Abstract

The present application discloses an inverter fault ride-through method, device, control equipment, storage medium and product. The inverter fault ride-through method includes: in the normal state, the inverter operates in the grid-forming mode, adopts VSG control, records the reactive power loop integrator value, runs the phase-locked loop control, and records the angle difference; in the fault state, the inverter operates in the grid-following mode, adopts current loop control and phase-locked loop control; in the case of fault recovery, the inverter operates in the grid-following mode, adopts current loop control and phase-locked loop control, and assigns values to the integrator in the VSG control according to the recorded angle difference, reactive power loop integrator value and the values of each loop in the grid-following mode; after the power grid recovers for a period of time, the inverter switches to the working state when the power grid is normal. By adopting different loop controls and using the recorded values of the phase-locked loop control to assign values to the integrator in the VSG control during the fault recovery stage, the inverter fault ride-through control process is simplified and the switching efficiency is improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of electrical control, and in particular, to an inverter fault ride-through method, device, control device, storage medium and product. Background Art

[0002] With the proposal of the goal of building a new power system, the proportion of new energy power generation will be further increased. New energy power generation equipment usually operates in a grid-connected control mode to pursue maximum power tracking. However, too high a proportion of new energy power generation will weaken the grid strength and lack voltage, frequency, inertia support, etc. In recent years, inverters (which can also be called power conversion systems (PCS) or grid-forming converters) based on virtual synchronous generator (VSG) control can improve the voltage, frequency, and inertia support capabilities of the power system and have been widely studied and applied. Compared with the grid-connected working mode, when the inverter operates in the grid-forming mode, although the stability is improved, the dynamic characteristics decline. When high or low voltage faults occur in the grid, current various standard requirements for the inverter fault ride-through characteristics often refer to grid-connected converters, making it much more difficult to meet the standard requirements.

[0003] To solve the above problems, a mode switching method can be adopted to complete fault ride-through. The grid-forming mode control is adopted when the grid is normal, the grid-connected mode control is adopted when the grid fails, and when the grid returns to normal, the grid-forming control mode is switched back. However, the current fault ride-through methods all adopt the method of sharing a common current loop in different stages. The current loop reference value switches frequently, which is relatively complex. Either ramp switching is required, affecting the switching speed; or additional state following control is required, and the control implementation is complex. Summary of the Invention

[0004] The present application provides an inverter fault ride-through method, device, control device, storage medium and product to simplify the inverter fault ride-through control and improve the switching efficiency of the inverter.

[0005] In a first aspect, an embodiment of the present application provides an inverter fault ride-through method, including:

[0006] When the grid is in a normal state, the inverter operates in the grid-forming mode, adopts virtual synchronous generator (VSG) control, records the value of the reactive power loop integrator, and runs a phase-locked loop control to record the angle difference between the VSG self-synchronization angle and the phase-locked angle of the phase-locked loop;

[0007] When the grid is in a fault state, the inverter operates in the grid-connected mode and adopts current loop control and phase-locked loop control;

[0008] In the case of power grid fault recovery, the inverter operates in the grid-following mode, adopts current loop control and phase-locked loop control, and assigns values to the integrators in the VSG control according to the recorded angle difference, the value of the reactive power loop integrator, and the values of each loop in the grid-following mode control;

[0009] After the power grid has been restored for a period of time, the inverter switches to the operating state when the power grid is normal.

[0010] In a second aspect, an embodiment of the present application further provides an inverter fault ride-through device, including:

[0011] A first control module, configured to, when the power grid is in a normal state, the inverter operates in the grid-forming mode, adopts virtual synchronous generator (VSG) control, records the value of the reactive power loop integrator, and operates the phase-locked loop control to record the angle difference between the VSG self-synchronization angle and the phase-locked angle of the phase-locked loop;

[0012] A second control module, configured to, when the power grid is in a fault state, the inverter operates in the grid-following mode, and adopts current loop control and phase-locked loop control;

[0013] A third control module, configured to, in the case of power grid fault recovery, the inverter operates in the grid-following mode, adopts current loop control and phase-locked loop control, and assigns values to the integrators in the VSG control according to the recorded angle difference, the value of the reactive power loop integrator, and the values of each loop in the grid-following mode control;

[0014] A switching module, configured to, after the power grid has been restored for a period of time, switch the inverter to the operating state when the power grid is normal.

[0015] In a third aspect, an embodiment of the present application provides a control device, including:

[0016] One or more processors;

[0017] A storage device, configured to store one or more programs;

[0018] When the one or more programs are executed by the one or more processors, the one or more processors implement the inverter fault ride-through method as described in the first aspect.

[0019] In a fourth aspect, an embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, it implements the inverter fault ride-through method as described in the first aspect.

[0020] In a fifth aspect, an embodiment of the present application further provides a computer program product, including a computer program and / or instructions, and when the computer program and / or instructions are executed by a processor, they implement the inverter fault ride-through method as described in any of the above embodiments.

[0021] The embodiments of the present application provide an inverter fault ride-through method, apparatus, control device, storage medium and product. The inverter fault ride-through method includes: in the normal state of the power grid, the inverter operates in the grid-forming mode, adopts virtual synchronous generator (VSG) control, records the value of the reactive loop integrator, and runs the phase-locked loop (PLL) control to record the angle difference between the VSG self-synchronization angle and the phase-locked angle of the PLL; in the fault state of the power grid, the inverter operates in the grid-following mode, adopting current loop control and PLL control; in the case of power grid fault recovery, the inverter operates in the grid-following mode, adopting current loop control and PLL control, and assigns values to the integrator in the VSG control according to the recorded angle difference, the value of the reactive loop integrator, and the values of each loop controlled in the grid-following mode; after the power grid recovers for a period of time, the inverter switches to the working state when the power grid is normal. The above technical solution simplifies the inverter fault ride-through control process and improves the switching efficiency by adopting different loop controls and using the recorded values of the PLL control to assign values to the integrator in the VSG control during the fault recovery stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In combination with the accompanying drawings and with reference to the following specific embodiments, the above and other features, advantages and aspects of the various embodiments of the present disclosure will become more apparent. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic and the original components and elements are not necessarily drawn to scale.

[0023] Figure 1 It is a schematic diagram of the hardware topology of a three-phase photovoltaic inverter provided by the embodiments of the present application;

[0024] Figure 2 It is a schematic diagram of the operating state of the inverter when a voltage fault occurs provided by the embodiments of the present application;

[0025] Figure 3 It is a flowchart of an inverter fault ride-through method provided by the embodiments of the present application;

[0026] Figure 4 It is a schematic diagram of the active power outer loop and the reactive power outer loop of the VSG control provided by the embodiments of the present application;

[0027] Figure 5 It is a schematic diagram of the virtual impedance link and the voltage-current inner loop of the VSG control provided by the embodiments of the present application;

[0028] Figure 6 It is a schematic diagram of the PLL control provided by the embodiments of the present application;

[0029] Figure 7 It is a schematic diagram of the current loop control provided by the embodiments of the present application;

[0030] Figure 8 Schematic diagram of an inverter fault ride-through process provided by an embodiment of the present application;

[0031] Figure 9 Schematic diagram of fault ride-through waveforms when the grid voltage suddenly drops to 0.2 p.u. provided by an embodiment of the present application;

[0032] Figure 10 Schematic diagram of fault ride-through waveforms when the grid voltage suddenly rises to 1.2 p.u. provided by an embodiment of the present application;

[0033] Figure 11 Schematic diagram of the structure of an inverter fault ride-through device provided by an embodiment of the present application;

[0034] Figure 12 Schematic diagram of the structure of a control device provided by an embodiment of the present application. Detailed implementation manners

[0035] The present application will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present application, rather than limiting the present application. Additionally, it should be noted that for the sake of description, only parts related to the present application rather than all structures are shown in the drawings.

[0036] Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the steps as sequential processes, many of the steps can be implemented in parallel, concurrently, or simultaneously. In addition, the order of the steps can be rearranged. The process can be terminated when its operation is completed, but there can also be additional steps not included in the drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0037] It should be noted that the concepts such as "first" and "second" mentioned in the embodiments of the present application are only used to distinguish different devices, modules, units, or other objects, and are not used to limit the order of functions performed by these devices, modules, units, or other objects or their interdependent relationships.

[0038] In addition, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0039] Exemplarily, the hardware topology structure of a typical three-phase inverter grid connection is as Figure 1As shown in the figure, taking a voltage source inverter (VSI) as an example, this inverter uses an LC filter, where L is the filtering inductor and C is the filtering capacitor, and is connected to the power grid through the point of common coupling (PCC). Among them, is the port voltage of the inverter or converter, is the power grid voltage, are respectively the equivalent resistance and inductive reactance of the power grid line impedance. When the power grid is normal, the inverter or converter operates in the grid-forming operation mode, mainly with VSG control.

[0040] When a voltage fault occurs in the power grid, the operating state of the inverter is as Figure 2 shown (taking low voltage ride-through as an example), which can be divided into three stages: In the first stage, the inverter normally operates in the VSG control mode. When the port voltage of the inverter is lower than the low voltage ride-through threshold or higher than the high voltage ride-through threshold , it is considered that a power grid fault has occurred and enters the second stage; in the second stage, the inverter switches to the grid-following operation mode. When the port voltage of the inverter is higher than the low voltage ride-through threshold and lower than the high voltage ride-through threshold , it is considered that the power grid has recovered and enters the third stage; in the third stage, the inverter continues to operate in the grid-following mode. After a delay of a period of time , it switches back to the VSG control mode of the first stage.

[0041] Figure 3 FIG.

[0042] is a flowchart of a method for an inverter fault ride-through provided by an embodiment of the present application. This embodiment is applicable to the situation of controlling the fault ride-through process of an inverter (which can also be called a converter), and can be applied to products such as PCS and photovoltaic inverters. Specifically, this inverter fault ride-through method can be executed by an inverter fault ride-through device, and this inverter fault ride-through device can be implemented in a software and / or hardware manner and integrated in a control device. The control device can be understood as a controller in the power grid, mainly used to control the inverter.

[0042] As Figure 3 shown, the method specifically includes the following steps:

[0043] S110. In the normal state of the power grid, the inverter operates in the grid-forming mode, adopts virtual synchronous generator VSG control, records the value of the reactive power loop integrator, and runs the phase-locked loop control, and records the angle difference between the VSG self-synchronization angle and the phase-locked angle of the phase-locked loop.

[0044] In this embodiment, the normal state of the power grid can be understood as the state where no fault occurs in the power grid, corresponding to the first stage of the above-mentioned operating state of the inverter. In the first stage, the inverter uses VSG control to obtain a modulation wave of Pulse Width Modulation (PWM). VSG control can be understood as simulating the operating characteristics (such as damping and moment of inertia) of a synchronous generator by controlling the output current and voltage of the inverter. For the angular frequency of VSG control Integrating gives the self-synchronization angle of VSG , and the simplified expression is: ; where is the reference active power, is the actual value of the active power, is the rated angular frequency, is the virtual inertia, is the damping coefficient, is the active-power - frequency droop coefficient, is the differential operator.

[0045] In this embodiment, in the first stage, the current-loop control of the grid-following mode is frozen, but the phase-locked loop (PLL) control can be operated. The phase-locked loop (PLL) control is mainly used to achieve the synchronous control of the inverter for synchronous operation. By monitoring and adjusting the frequency and phase of the power system, the PLL makes the current and voltage of the inverter in phase with the power system, thereby improving the operating stability and efficiency of the inverter.

[0046] In the first stage, on the one hand, the value of the VSG reactive-loop integrator can be recorded regularly, denoted as , and it will not be updated when entering the second stage. Among them, as shown in Figure 4 , is the difference between the no-load electromotive force and the rated no-load electromotive force, that is ; on the other hand, the difference between the VSG self-synchronization angle ( ) and the PLL phase-locked angle ( ), that is, the angle difference, can be recorded regularly, denoted as ; the recorded angle difference will not be updated after entering the second stage.

[0047] S120. In the case of a power grid fault, the inverter operates in the grid-following mode and uses current-loop control and phase-locked loop control.

[0048] In this embodiment, when a power grid fault occurs, it enters the second stage, and the phase-locked loop control and current-loop control can be operated for fault ride-through; in addition, in the second stage, the VSG control is frozen, that is, no processing is done to the VSG control loop.

[0049] S130. In the case of power grid fault recovery, the inverter operates in the grid - following mode, adopting current - loop control and phase - locked loop control, and assigning values to the integrators in the VSG control according to the recorded angle difference, the value of the reactive - loop integrator, and the values of each loop in the grid - following mode control.

[0050] In this embodiment, after the power grid fault is recovered, the inverter enters the third stage, adopting the grid - following control mode, running the phase - locked loop control and the current - loop control, and performing PWM modulation on the modulation voltage obtained according to the current reference value and the current - loop control. In addition, the values of each integrator in the VSG control can be assigned according to the following loop values: the change amount of the VSG angular frequency, the VSG self - synchronization angle, the value of the reactive - loop integrator, the integrators of the integral control in the direct - axis and quadrature - axis voltage loops, and the integrators of the integral control in the direct - axis and quadrature - axis current loops.

[0051] It can be understood that in the third stage, the control of the inverter is realized by the current - loop control and the phase - locked loop control. At this time, the purpose of simultaneously executing the VSG control is mainly to perform the integrator assignment process, but the VSG control is not used as the control of the inverter.

[0052] S140. After the power grid is restored for a period of time, the inverter switches to the working state when the power grid is normal. In this embodiment, the duration of the third stage can be timed. When the duration exceeds the set threshold ( ), it can be switched back to the first stage to achieve smooth switching. Among them, It can be set according to specific circumstances, and this value is related to the selection of control parameters.

[0053] A method for an inverter to ride through faults provided by an embodiment of the present application simplifies the control process of the inverter to ride through faults and improves the switching efficiency by adopting different loop controls in different stages and using the recorded values of the phase - locked loop control to assign values to the integrators in the VSG control during the fault - recovery stage.

[0054] In one embodiment, the method further includes:

[0055] Determine the VSG control parameters in the normal state of the power grid.

[0056] In this embodiment, for the first stage, VSG control is adopted. The VSG control parameters include: power outer - loop control parameters, virtual - impedance control parameters, and voltage - current inner - loop control parameters; among them, the power outer - loop control parameters include the VSG self - synchronization angle corresponding to the active - power outer loop ( , which can be obtained by integrating the angular frequency of the VSG control), and the no - load electromotive force corresponding to the reactive - power outer loop ( ); the virtual - impedance control parameters include the port - voltage reference value (including the d - axis and q - axis port - voltage reference values ); The inner voltage and current loop control parameters include the current inner loop reference values (including the d-axis and q-axis current inner loop reference values ) and the current inner loop modulation voltages (including the d-axis and q-axis current inner loop reference values ).

[0057] Figure 4 It is a schematic diagram of the outer active power loop and the outer reactive power loop for VSG control. As Figure 4 shown, the outer active power loop includes an active-frequency droop link, a virtual inertia (J) link, and a damping (D) link; the outer reactive power loop includes a reactive-voltage droop link and an integral link. The simplified expression of the corresponding no-load electromotive force is: ; where is the reactive power reference, is the actual reactive power value, is the reactive-voltage droop coefficient, is the integral coefficient, is the rated no-load electromotive force of VSG, is the rated grid connection point voltage.

[0058] Figure 5 It is a schematic diagram of the virtual impedance link and the inner voltage and current loops for VSG control. As Figure 5 shown, using the VSG self-synchronization angle to perform Park transformation on the inverter terminal voltage , the inverter current , to obtain the d-axis and q-axis voltages in the grid-forming mode, and the d-axis and q-axis currents . After the VSG no-load electromotive force passes through the virtual impedance, the d-axis and q-axis port voltage reference values are obtained, and the expression is:

[0059] ;

[0060] where is the VSG virtual resistance, is the VSG virtual inductive reactance. After passing through the voltage inner loop, the d-axis and q-axis current inner loop reference values are obtained, and the expression is:

[0061] ;

[0062] where is the proportional coefficient of the voltage loop PI controller, is the integral coefficient of the voltage-current loop PI controller. After passing through the current inner loop, the d-axis and q-axis modulation voltages are obtained, and the expression is:

[0063] ；

[0064] Among them, is the proportional coefficient of the current loop PI controller, is the integral coefficient of the current loop PI controller. The obtained modulation voltage is sent to the PWM link for modulation.

[0065] In one embodiment, the method further includes:

[0066] Determining the phase-locked loop control parameters under normal grid conditions.

[0067] In this embodiment, for the second stage, phase-locked loop control is adopted, and the phase-locked loop control parameters include the phase-locked angle ( ).

[0068] Determining the phase-locked loop control parameters under normal grid conditions includes:

[0069] Performing a Clarke transformation on the port voltage ( ) in the three-phase stationary coordinate system to obtain the port voltage ( ) in the two-phase stationary coordinate system;

[0070] Performing a Park transformation on the port voltage in the two-phase stationary coordinate system to obtain the direct-axis and quadrature-axis voltages ( ) in the grid-following mode;

[0071] Determining the phase-locked angle ( ) according to the direct-axis and quadrature-axis voltages in the grid-following mode.

[0072] Figure 6 is a schematic diagram of the phase-locked loop control. As Figure 6 shown, first perform a Clarke transformation on the port voltage in the ABC three-phase stationary coordinate system to obtain coordinate system voltage (i.e., the port voltage in the two-phase stationary coordinate system) ; then use the phase-locked angle to perform a Park transformation on to obtain the d, q-axis voltages ; after phase-locked loop control, obtain the PLL output, i.e., the phase-locked angle , and the expression is:

[0073] ;

[0074] Among them, is the output of the phase-locked loop PI controller, is the proportional coefficient of the phase-locked loop PI controller, is the integral coefficient of the phase-locked loop PI controller.

[0075] In one embodiment, the method further includes:

[0076] Determine the current loop control parameters under the power grid fault condition.

[0077] In this embodiment, for the second stage, current loop control is adopted. The current loop control parameters include the modulation voltages of the direct axis and the quadrature axis in the grid-following mode ( ).

[0078] Determining the current loop control parameters under the power grid fault condition includes: performing Park transformation on the terminal voltage ( ) and the inverter current ( ) in the three-phase stationary coordinate system to obtain the voltages ( ) and currents ( ) of the direct axis and the quadrature axis in the grid-following mode; determining the modulation voltages of the direct axis and the quadrature axis in the grid-following mode according to the current reference values of the direct axis and the quadrature axis ( ) and the voltages and currents of the direct axis and the quadrature axis in the grid-following mode ( ); wherein, the current reference values of the direct axis and the quadrature axis can be set according to the standard requirements during the actual fault.

[0079] Figure 7 FIG. is a schematic diagram of the current loop control. As Figure 7 shown, using the phase-locked angle to perform Park transformation on the three-phase inverter terminal voltage , the inverter current I L to obtain the d-axis and q-axis voltages , and the d-axis and q-axis currents . The d-axis and q-axis current reference values can be set according to the standard requirements during the actual fault. For example, adopting the national standard, the amplitude of can be set as:

[0080] ;

[0081] wherein, is the per-unit value of the inverter terminal voltage.

[0082] Through the current inner loop, the modulation voltages of the d-axis and q-axis are obtained, and the expression is:

[0083] ;

[0084] The obtained modulation voltage is sent to the PWM link for modulation.

[0085] In one embodiment, the method further includes:

[0086] According to the reference value of the inner current loop ( ), the integrator values of the PI control of the direct-axis and quadrature-axis current loops ( ), and the direct-axis and quadrature-axis currents ( ), determine the current loop control parameters in the case of grid fault recovery; the current loop control parameters include the modulation voltages of the direct-axis and quadrature-axis of the inner current loop.

[0087] In this embodiment, for the third stage, the grid-following control mode is adopted, and the phase-locked loop and the current loop are operated.

[0088] According to the reference value of the inner current loop ( ), the integrator values of the PI control of the d-axis and q-axis current loops ( ), and the d-axis and q-axis currents ( ), the d-axis and q-axis modulation voltages ( ) of the VSG can be obtained and PWM modulation is performed. The calculation expressions of the d-axis and q-axis modulation voltages ( ) are:

[0089] .

[0090] In one embodiment, the assignment of the integrator in the VSG control according to the recorded angle difference, the integrator value of the reactive power loop, and the values of each loop controlled by the grid-following mode includes:

[0091] Assign the active power loop inertia integrator to the change in the VSG angular frequency ( );

[0092] Assign the angle integrator to the sum of the recorded angle difference ( ) and the phase-locked angle ( );

[0093] Assign the reactive power loop integrator to the recorded integrator value of the reactive power loop ( );

[0094] According to the self-synchronization angle ( ), the phase-locked angle ( ), and the current reference values of the direct-axis and quadrature-axis ( ), assign values to the integrators of the PI control of the voltage loops of the direct-axis and quadrature-axis respectively;

[0095] According to the self-synchronization angle, the phase-locked angle, and the modulation voltages of the direct-axis and quadrature-axis ( ), assign values to the integrators of the PI control of the current loops of the direct-axis and quadrature-axis respectively;

[0096] Among them, the current reference values of the direct-axis and quadrature-axis ( ) are determined according to the active power reference and the reactive power reference in the VSG control under normal grid conditions.

[0097] like Figure 4 and Figure 5 As shown in the dotted box of the winning bid ③. Assign the value of the active loop inertia integrator, that is, ; Assign the angle integrator, that is ; Assign value to the reactive loop integrator, that is ;in, 、 is the timed recording value in the first stage.

[0098] The integrators of the PI control of the d and q axis voltage loops are assigned values of , which is calculated as follows:

[0099] ;

[0100] Among them, the d and q axis current reference values ( ) can be controlled by the active power reference in the first stage VSG , reactive power reference The calculation expression is:

[0101] .

[0102] After the above processing, the VSG current loop current reference value The expression is:

[0103] ;

[0104] The integrators of the PI control of the d and q axis current loops are assigned values 、 , which is calculated as follows:

[0105] .

[0106] As an example, the inverter high and low voltage fault ride-through process based on mode switching is as follows: Figure 8 As shown in the figure, the inverter works in the grid-building mode when it is working normally, and works in the grid-following mode when the grid fails. After the grid fails, it switches from the grid-following mode to the grid-building mode. The details are as follows:

[0107] In the first stage, the inverter operates normally, adopts VSG control, runs PLL, and backs up the VSG reactive loop integrator value. , and the difference between the backup VSG self-synchronization angle and the PLL phase-locking angle ;

[0108] like ,or , the inverter fails and enters the second stage;

[0109] In the second stage, grid-following control is adopted, and each control loop of the VSG freezes. The current reference values of the direct axis and the quadrature axis ( ) can be set according to the standard requirements during the actual fault;

[0110] If , the inverter resumes and enters the third stage;

[0111] In the third stage, grid-following control is adopted, and the current reference values of the direct axis and the quadrature axis ( ) can be set according to the operating state before the fault (the active power reference and the reactive power reference in the VSG control under the normal grid state), and each integrator in the VSG control is continuously assigned values;

[0112] After the third stage lasts for a period of time (exceeding ), it switches to the normal state (the first stage).

[0113] On this basis, the fault ride-through control process of the inverter can be simplified, the switching efficiency can be improved, and smooth switching can be achieved.

[0114] Taking the high and low voltage fault ride-through of a grid-forming energy storage converter (PCS) as an example, the fault ride-through performance is verified. Keeping the active power P = 1 p.u. and the reactive power Q = 0 p.u. unchanged, when the grid voltage suddenly drops from the rated voltage (1 p.u.) to 0.2 p.u. and suddenly rises to 1.2 p.u., the waveforms of the fault ride-through are as shown in Figure 9 and Figure 10 . Selecting the duration of the third stage to be 500 ms. After the grid fails, the converter completes the ride-through in the grid-following mode; after the grid recovers, after 500 ms, the converter switches back to the grid-forming VSG control, and the power and current fluctuations during the switching process are very small.

[0115] Figure 11 is a schematic structural diagram of an inverter fault ride-through device provided by an embodiment of the present application. The inverter fault ride-through device provided by this embodiment includes: [[ID=3�]]

[0116] The first control module 210 is used to, when the grid is in the normal state, the inverter operates in the grid-forming mode, adopt the virtual synchronous generator (VSG) control, record the value of the reactive power loop integrator, and run the phase-locked loop control to record the angle difference between the VSG self-synchronization angle and the phase-locked angle of the phase-locked loop;

[0117] The second control module 220 is used to, when the grid is in the fault state, the inverter operates in the grid-following mode, and adopt the current loop control and the phase-locked loop control;

[0118] The third control module 230 is used to make the inverter operate in the grid - following mode in the case of grid fault recovery, adopt current - loop control and phase - locked loop control, and assign values to the integrator in the VSG control according to the recorded angle difference, the value of the reactive - power loop integrator, and the values of each loop in the grid - following mode control;

[0119] The switching module 240 is used to make the inverter switch to the working state when the grid is normal after a period of grid recovery.

[0120] By adopting different loop controls and using the recorded values of the phase - locked loop control to assign values to the integrator in the VSG control during the fault - recovery stage, the device simplifies the inverter fault - ride - through control process and improves the switching efficiency.

[0121] Based on the above - mentioned embodiment, the device further includes:

[0122] The first determination module is used to determine the VSG control parameters in the normal grid state;

[0123] The VSG control parameters include: power outer - loop control parameters, virtual - impedance control parameters, and voltage - current inner - loop control parameters;

[0124] The power outer - loop control parameters include the VSG self - synchronization angle corresponding to the active - power outer - loop and the no - load electromotive force corresponding to the reactive - power outer - loop;

[0125] The virtual - impedance control parameters include the port - voltage reference value;

[0126] The voltage - current inner - loop control parameters include the current - loop reference value and the current - loop modulation voltage.

[0127] Based on the above - mentioned embodiment, the device further includes:

[0128] The second determination module is used to determine the phase - locked loop control parameters in the normal grid state, and the phase - locked loop control parameters include the phase - locked angle;

[0129] Determining the phase - locked loop control parameters in the normal grid state includes:

[0130] Performing a Clarke transformation on the port voltage in the three - phase stationary coordinate system to obtain the port voltage in the two - phase stationary coordinate system;

[0131] Performing a Park transformation on the port voltage in the two - phase stationary coordinate system to obtain the direct - axis and quadrature - axis voltages in the grid - following mode;

[0132] Determining the phase - locked angle according to the direct - axis and quadrature - axis voltages in the grid - following mode.

[0133] Based on the above - mentioned embodiment, the device further includes:

[0134] A third determination module, configured to determine current loop control parameters under a power grid fault condition; the current loop control parameters include modulation voltages of the direct axis and the quadrature axis in the grid-following mode;

[0135] The determination of the current loop control parameters under the power grid fault condition includes:

[0136] Performing Park transformation on the port voltage and the inverter current in the three-phase stationary coordinate system to obtain the voltages and currents of the direct axis and the quadrature axis in the grid-following mode;

[0137] Determining the modulation voltages of the direct axis and the quadrature axis in the grid-following mode according to the current reference values of the direct axis and the quadrature axis and the voltages and currents of the direct axis and the quadrature axis in the grid-following mode;

[0138] Wherein, the current reference values of the direct axis and the quadrature axis are set according to the standard requirements during the actual fault.

[0139] Based on the above embodiments, the device further includes:

[0140] A fourth determination module, configured to determine current loop control parameters in the case of power grid fault recovery according to the current inner loop reference value, the integrator values of the PI control of the direct axis and the quadrature axis current loops, and the direct axis and the quadrature axis currents; the current loop control parameters include modulation voltages of the direct axis and the quadrature axis of the current inner loop;

[0141] Wherein, the current reference values of the direct axis and the quadrature axis are determined according to the active power reference and the reactive power reference in the VSG control under the normal state of the power grid.

[0142] In an embodiment, the assignment of the integrator in the VSG control according to the recorded angle difference, the reactive power loop integrator value, and the respective loop values of the grid-following mode control includes:

[0143] Assigning the inertia integrator of the active power loop to the change amount of the VSG angular frequency;

[0144] Assigning the angle integrator to the sum of the recorded angle difference and the phase-locked angle;

[0145] Assigning the reactive power loop integrator to the recorded reactive power loop integrator value;

[0146] Assigning values to the integrators of the PI control of the voltage loops of the direct axis and the quadrature axis respectively according to the self-synchronization angle, the phase-locked angle, and the current reference values of the direct axis and the quadrature axis;

[0147] Assigning values to the integrators of the PI control of the current loops of the direct axis and the quadrature axis respectively according to the self-synchronization angle, the phase-locked angle, and the modulation voltages of the direct axis and the quadrature axis;

[0148] Wherein, the current reference values of the direct axis and the quadrature axis ( ) are determined according to the active power reference and the reactive power reference in the VSG control under the normal state of the power grid.

[0149] The inverter fault ride-through device provided by the embodiment of the present application can be used to execute the inverter fault ride-through method provided by any of the above embodiments, and has corresponding functions and beneficial effects.

[0150] Figure 12 FIG. shows a schematic structural diagram of a control device 10 that can be used to implement the embodiments of the present application. As Figure 12 shown, the control device 10 includes at least one processor 11, and a memory communicatively connected to the at least one processor 11, such as a read-only memory (ROM) 12, a random access memory (RAM) 13, etc. Among them, the memory stores a computer program executable by the at least one processor. The processor 11 can execute various appropriate actions and processes according to the computer program stored in the read-only memory (ROM) 12 or the computer program loaded from the storage unit 18 into the random access memory (RAM) 13. In the RAM 13, various programs and data required for the operation of the control device 10 can also be stored. The processor 11, the ROM 12, and the RAM 13 are connected to each other through a bus 14. The input / output (I / O) interface 15 is also connected to the bus 14.

[0151] Multiple components in the control device 10 are connected to the I / O interface 15, including: an input unit 16, such as a keyboard, a mouse, etc.; an output unit 17, such as various types of displays, speakers, etc.; a storage unit 18, such as a magnetic disk, an optical disc, etc.; and a communication unit 19, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 19 allows the control device 10 to exchange information / data with other devices through a computer network such as the Internet and / or various telecommunication networks and wireless networks.

[0152] The processor 11 can be various general and / or special processing components with processing and computing capabilities. Some examples of the processor 11 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, a digital signal processor (DSP), and any appropriate processor, controller, microcontroller, etc. The processor 11 executes the various methods and processes described above.

[0153] In some embodiments, the method of the above embodiments may be implemented as a computer program tangibly embodied in a computer-readable storage medium, such as storage unit 18. In some embodiments, part or all of the computer program may be loaded and / or installed onto the control device 10 via the ROM 12 and / or the communication unit 19. When the computer program is loaded into the RAM 13 and executed by the processor 11, one or more steps of the methods described above may be performed. Alternatively, in other embodiments, the processor 11 may be configured to execute the methods of any of the above embodiments by any other suitable means (e.g., by means of firmware).

[0154] The various embodiments of the systems and techniques described above in this document may be implemented in digital electronic circuitry, integrated circuit systems, field programmable gate arrays (FPGA), application specific integrated circuits (ASIC), application specific standard products (ASSP), systems on a chip (SOC), complex programmable logic devices (CPLD), computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include: being implemented in one or more computer programs that may be executed and / or interpreted on a programmable system including at least one programmable processor, which may be a special-purpose or general-purpose programmable processor that receives data and instructions from a storage system, at least one input device, and at least one output device, and transmits the data and instructions to the storage system, the at least one input device, and the at least one output device.

[0155] The computer programs for implementing the methods of this application may be written in any combination of one or more programming languages. These computer programs may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus, such that the computer programs, when executed by the processor, cause the functions / operations specified in the flowchart and / or block diagram to be implemented. The computer programs may be executed entirely on the machine, partly on the machine, as a stand-alone software package partly on the machine and partly on a remote machine, or entirely on the remote machine or server.

[0156] In the context of the present application, a computer-readable storage medium can be a tangible medium that can contain or store a computer program for use by or in connection with an instruction execution system, apparatus, or device. The computer-readable storage medium can include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. Alternatively, the computer-readable storage medium can be a machine-readable signal medium. More specific examples of the machine-readable storage medium would include an electrical connection based on one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0157] To provide for interaction with a user, the systems and techniques described herein can be implemented on a control device 10 having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and a pointing device (e.g., a mouse or a trackball) by which the user can provide input to the control device 10. Other kinds of devices can also be used to provide for interaction with the user; for example, the feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including acoustic input, voice input, or tactile input).

[0158] The systems and techniques described herein can be implemented in a computing system that includes back-end components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes front-end components (e.g., a user computer having a graphical user interface or a web browser through which the user can interact with an implementation of the systems and techniques described herein), or a computing system that includes any combination of such back-end components, middleware components, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of the communication network include: a local area network (LAN), a wide area network (WAN), a blockchain network, and the Internet.

[0159] A computing system may include a client and a server. The client and the server are generally far from each other and usually interact via a communication network. The relationship between the client and the server is generated by computer programs running on respective computers and having a client-server relationship with each other. The server may be a cloud server, also known as a cloud computing server or a cloud host, which is a host product in the cloud computing service system, and solves the defects of large management difficulty and weak business scalability existing in traditional physical hosts and VPS services.

[0160] An embodiment of the present application also provides a computer program product, including a computer program and / or instructions, which, when executed by a processor, implement the inverter fault ride-through method as described in any of the above embodiments.

[0161] It should be understood that various forms of the processes shown above can be used, steps can be reordered, added or deleted. For example, the steps described in the present application can be executed in parallel, sequentially or in a different order, as long as the desired results of the technical solution of the present application can be achieved, and no limitation is made herein.

[0162] The above specific embodiments do not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for a converter to ride through faults, characterized in that, Including: Under normal grid conditions, the inverter operates in the grid-forming mode, adopts virtual synchronous generator (VSG) control, records the value of the reactive loop integrator, and runs the phase-locked loop (PLL) control to record the angle difference between the VSG self-synchronization angle and the phase-locked angle of the PLL. Under grid fault conditions, the inverter operates in the grid-following mode, adopting current loop control and PLL control. In the case of grid fault recovery, the inverter operates in the grid-following mode, adopting current loop control and PLL control, and assigns values to the integrator in the VSG control according to the recorded angle difference, the value of the reactive loop integrator, and the values of each loop in the grid-following mode control. After the grid has recovered for a period of time, the inverter switches to the operating state when the grid is normal. The assigning values to the integrator in the VSG control according to the recorded angle difference, the value of the reactive loop integrator, and the values of each loop in the grid-following mode control includes: Assigning the active loop inertia integrator with the change in VSG angular frequency. Assigning the angle integrator with the sum of the recorded angle difference and the phase-locked angle. Assigning the reactive loop integrator with the recorded value of the reactive loop integrator. Assigning values to the integrators of the PI control for the direct-axis and quadrature-axis voltage loops according to the self-synchronization angle, the phase-locked angle, and the current reference values of the direct axis and the quadrature axis. Assigning values to the integrators of the PI control for the direct-axis and quadrature-axis current loops according to the self-synchronization angle, the phase-locked angle, and the modulation voltages of the direct axis and the quadrature axis. Wherein, the current reference values of the direct axis and the quadrature axis are determined according to the active power reference and the reactive power reference in the VSG control under normal grid conditions.

2. The method according to claim 1, wherein Also including: Determining the VSG control parameters under normal grid conditions. The VSG control parameters include: power outer loop control parameters, virtual impedance control parameters, and voltage-current inner loop control parameters. The power outer loop control parameters include the VSG self-synchronization angle corresponding to the active outer loop and the no-load electromotive force corresponding to the reactive outer loop. The virtual impedance control parameters include the port voltage reference value. The voltage-current inner loop control parameters include the current inner loop reference value and the current inner loop modulation voltage.

3. The method according to claim 1, wherein Also including: Determining the PLL control parameters under normal grid conditions, and the PLL control parameters include the phase-locked angle. The determining the PLL control parameters under normal grid conditions includes: Performing a Clarke transform on the port voltage in the three-phase stationary coordinate system to obtain the port voltage in the two-phase stationary coordinate system. Performing a Park transform on the port voltage in the two-phase stationary coordinate system to obtain the direct-axis and quadrature-axis voltages in the grid-following mode. Determining the phase-locked angle according to the direct-axis and quadrature-axis voltages in the grid-following mode.

4. The method according to claim 1, wherein Also including: Determining the current loop control parameters under grid fault conditions. The current loop control parameters include the modulation voltages of the direct axis and the quadrature axis in the grid-following mode. The determining the current loop control parameters under grid fault conditions includes: Performing a Park transform on the port voltage and the inverter current in the three-phase stationary coordinate system to obtain the direct-axis and quadrature-axis voltages and currents in the grid-following mode. Determining the modulation voltages of the direct axis and the quadrature axis in the grid-following mode according to the current reference values of the direct axis and the quadrature axis and the direct-axis and quadrature-axis voltages and currents in the grid-following mode. Wherein, the current reference values of the direct axis and the quadrature axis are set according to the standard requirements during the actual fault period.

5. The method according to claim 1, characterized in that It further includes: Determine the current loop control parameters in the case of grid fault recovery according to the current inner loop reference value, the integrator values of the direct-axis and quadrature-axis current loops under PI control, and the direct-axis and quadrature-axis currents; the current loop control parameters include the modulation voltages of the direct-axis and quadrature-axis of the current inner loop. Among them, the current reference values of the direct axis and the quadrature axis are determined according to the active power reference and the reactive power reference in the VSG control under normal grid conditions.

6. An inverter fault ride-through device, characterized in that, It includes: A first control module, which is used to operate the inverter in the grid-forming mode under normal grid conditions, adopt virtual synchronous generator (VSG) control, record the integrator value of the reactive power loop, and run the phase-locked loop control to record the angle difference between the VSG self-synchronization angle and the phase-locked angle of the phase-locked loop. A second control module, which is used to operate the inverter in the grid-following mode under grid fault conditions, and adopt current loop control and phase-locked loop control. A third control module, which is used to operate the inverter in the grid-following mode in the case of grid fault recovery, adopt current loop control and phase-locked loop control, and assign values to the integrators in the VSG control according to the recorded angle difference, the integrator value of the reactive power loop, and the respective loop values of the grid-following mode control. A switching module, which is used to switch the inverter to the working state when the grid is normal after a period of grid recovery. The assigning values to the integrators in the VSG control according to the recorded angle difference, the integrator value of the reactive power loop, and the respective loop values of the grid-following mode control includes: Assign the active power loop inertia integrator to the change in VSG angular frequency. Assign the angle integrator to the sum of the recorded angle difference and the phase-locked angle. Assign the reactive power loop integrator to the recorded integrator value of the reactive power loop. Assign values to the integrators of the PI control of the direct-axis and quadrature-axis voltage loops respectively according to the self-synchronization angle, the phase-locked angle, and the current reference values of the direct axis and the quadrature axis. Assign values to the integrators of the PI control of the direct-axis and quadrature-axis current loops respectively according to the self-synchronization angle, the phase-locked angle, and the modulation voltages of the direct axis and the quadrature axis. Among them, the current reference values of the direct axis and the quadrature axis are determined according to the active power reference and the reactive power reference in the VSG control under normal grid conditions.

7. A control device, characterized in that, It includes: At least one processor; A memory communicatively connected to the at least one processor; wherein, The memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can execute the inverter fault ride-through method according to any one of claims 1-5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the inverter fault ride-through method according to any one of claims 1-5.

9. A computer program product, comprising a computer program and / or instructions, characterized in that, When the computer program and / or instructions are executed by the processor, they implement the inverter fault ride-through method according to any one of claims 1-5.

Images