Stable Control Method and Related Device of Phase-Locked Loop for Grid-Connected Inverter Based on Phase-Locked Offset Compensation

Abstract

An embodiment of the present application discloses a stable control method and related device for a phase-locked loop of a grid-connected inverter based on phase-locked offset compensation. In the present application, a voltage control signal of the inverter in a two-phase synchronous rotating coordinate system is determined according to a first formula, and then the turning on and off of a power device are controlled according to the voltage control signal to achieve stable control of the phase-locked loop of the grid-connected inverter. When determining the voltage control signal, the first formula takes into account phase-locked frequency offset compensation, and this phase-locked frequency offset compensation is determined according to a compensation matrix transfer function and an offset frequency output by a phase-locked loop PI regulator, providing a stable control method for the phase-locked loop of a grid-connected inverter based on phase-locked offset compensation, which is beneficial to canceling the disturbance signal in the disturbance path of the phase-locked loop in the output impedance model and completing the closed-loop decoupling control of the grid-connected AC device, thereby significantly improving the operation stability of the grid-connected inverter.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic systems, and in particular to a stable control method and related device for a phase-locked loop of a grid-connected inverter based on phase-locked offset compensation. Background Art

[0002] With the increasing proportion of new energy generating units in the power system, the power system dominated by traditional synchronous machines has gradually evolved into a new power system dominated by power electronic converters. However, new energy power generation systems are usually located in the "Three-North" regions far from the load centers. Large-capacity, long-distance power transmission and transformer leakage inductance result in non-negligible grid impedance. Moreover, with the continuous access of new energy power stations, the grid-connected capacity of new energy power stations is also increasing continuously, making the power grid exhibit the characteristics of a weak grid with a low short-circuit ratio (SCR). Under a weak grid, the interaction and coupling between the internal control loops of the grid-connected inverter, such as the phase-locked loop (PLL) and the alternating-current control (ACC), are intensified, resulting in a decrease in the system stability margin and seriously threatening the safe and stable operation of the power system. Summary of the Invention

[0003] The embodiments of the present application provide a stable control method and related device for a phase-locked loop of a grid-connected inverter based on phase-locked offset compensation, which are beneficial to canceling the disturbance signals in the disturbance path of the phase-locked loop in the output impedance model and completing the closed-loop decoupling control of the grid-connected inverter, thereby significantly improving the operation stability of the grid-connected inverter.

[0004] The first aspect of the embodiments of the present application provides a stable control method for a phase-locked loop of a grid-connected inverter based on phase-locked offset compensation. The method includes:

[0005] Determining the voltage control signal of the inverter in the two-phase synchronous rotating coordinate system according to the first formula, where the first formula is:

[0006]

[0007] where and are the voltage control signals of the d-axis and q-axis respectively, and are the preset d-axis and q-axis grid current command signals, and are the current variables of the d-axis and q-axis respectively, and are the voltage variables of the d-axis and q-axis respectively, is the Laplace operator, is the rated angular frequency of the grid voltage is the current loop PI regulator, is the transfer function based on the grid-side capacitor voltage feedforward link, is the compensation matrix transfer function based on the phase-locked frequency offset, is the output filter inductor of the inverter, is the offset frequency output by the phase-locked loop PI regulator;

[0008] Control the turning on and off of the power device according to the voltage control signal to achieve the stable control of the phase-locked loop of the grid-connected inverter.

[0009] Optionally, , where, is the phase-locked loop bandwidth, 、 are respectively the proportional regulation coefficient and the low-pass filter regulation coefficient of the qq channel of; The method further includes:

[0010] Determine 、 according to the second formula, and the second formula is:

[0011]

[0012] Where, is the output-side inductor current during the steady-state operation of the grid-connected AC, is the grid-side capacitor voltage during the steady-state operation of the grid-connected AC, is the current loop proportional regulation coefficient, is the current loop integral regulation coefficient, is the feedforward regulation coefficient of the grid-side capacitor voltage.

[0013] Optionally, before determining 、 according to the second formula, the method further includes: determining according to the third formula, and determining according to the fourth formula;

[0014] The third formula is:

[0015] ;

[0016] The fourth formula is:

[0017] ;

[0018] Where, is the rated capacity of the inverter, is the amplitude of the grid voltage.

[0019] Optionally, before determining the voltage control signal of the inverter in the two-phase synchronous rotating coordinate system according to the first formula, the method further includes:

[0020] Collect the three-phase voltages of the grid-side capacitor in the three-phase stationary coordinate system , , ;

[0021] Perform Clark and Park transformations on the three-phase voltages , , to obtain the d-axis and q-axis voltage variables in the two-phase synchronous rotating coordinate system , .

[0022] Optionally, before determining the voltage control signal of the inverter in the two-phase synchronous rotating coordinate system according to the first formula, the method further includes:

[0023] Collect the three-phase currents of the output filter inductor of the inverter in the three-phase stationary coordinate system , , ;

[0024] Perform Clark and Park transformations on the three-phase currents , , according to the phase angle of the grid-side capacitor voltage to obtain the d-axis and q-axis current variables in the synchronous rotating coordinate system , , where the phase angle of the grid-side capacitor voltage is obtained after passing the q-axis voltage variable through a phase-locked loop.

[0025] Optionally, the phase angle of the grid-side capacitor voltage is determined based on the fifth formula, and the fifth formula is:

[0026]

[0027] where is the phase-locked loop PI regulator, is the proportional regulation coefficient of the phase-locked loop, is the integral regulation coefficient of the phase-locked loop.

[0028] Optionally, controlling the turning on and off of the power device according to the voltage control signal includes:

[0029] Perform Clark and Park inverse transformations on the voltage control signal according to the phase angle of the grid-side capacitor voltage to obtain the modulation signal in the three-phase stationary coordinate system;

[0030] Perform pulse width modulation on the modulation signal to generate a PWM switching signal for the power device in the inverter;

[0031] Process the PWM switching signal through a drive circuit to control the turning on and off of the power device.

[0032] The second aspect of the embodiments of the present application provides a grid-connected inverter phase-locked loop stability control device based on phase-locked offset compensation, and the device includes:

[0033] A control signal determination unit, configured to determine a voltage control signal of the inverter in a two-phase synchronous rotating coordinate system according to a first formula, and the first formula is:

[0034]

[0035] Wherein, and are the d-axis and q-axis voltage control signals respectively, and are the preset d-axis and q-axis grid current command signals, and are the d-axis and q-axis current variables respectively, and are the d-axis and q-axis voltage variables respectively, is the Laplace operator, is the rated angular frequency of the grid voltage, is the current loop PI regulator, is the transfer function based on the grid-side capacitor voltage feed-forward link, is the compensation matrix transfer function based on the phase-locked frequency offset, is the output filter inductor of the inverter, is the offset frequency output by the phase-locked loop PI regulator;

[0036] A switch control unit, configured to control the turning on and off of the power device according to the voltage control signal to achieve stable control of the phase-locked loop of the grid-connected inverter.

[0037] The third aspect of the embodiments of the present application provides an electronic device, including: a processor and a memory;

[0038] The processor is connected to the memory, wherein the memory is used to store a computer program, and the processor is used to call the computer program to execute the method in the first aspect of the embodiments of the present application.

[0039] The fourth aspect of the embodiments of the present application provides a computer-readable storage medium, and the computer-readable storage medium stores a computer program, and the computer program includes program instructions, and when the program instructions are executed by a processor, the method in the first aspect of the embodiments of the present application is executed.

[0040] This application determines the voltage control signal of the inverter in two synchronous rotating coordinate systems according to the first formula, and then controls the turning on and off of the power device according to the voltage control signal to achieve stable control of the grid-connected inverter phase-locked loop. The first formula is:

[0041]

[0042] Wherein, and are the voltage control signals of the d-axis and q-axis respectively, and are the preset d-axis and q-axis grid current command signals, and are the current variables of the d-axis and q-axis respectively, and are the voltage variables of the d-axis and q-axis respectively, is the Laplace operator, is the rated angular frequency of the grid voltage, is the current loop PI regulator, is the transfer function based on the grid-side capacitor voltage feed-forward link, is the compensation matrix transfer function based on the phase-locked frequency offset, is the output filter inductor of the inverter, is the offset frequency output by the phase-locked loop PI regulator.

[0043] It can be seen that when determining the voltage control signal, the first formula takes into account the phase-locked frequency offset compensation, and this phase-locked frequency offset compensation is determined according to the compensation matrix transfer function and the offset frequency output by the phase-locked loop PI regulator, providing a stable control method for the phase-locked loop of the grid-connected inverter based on phase-locked offset compensation, which is beneficial to canceling the disturbance signal in the phase-locked loop disturbance path of the output impedance model and completing the closed-loop decoupling control of the grid-connected inverter, thereby significantly improving the operation stability of the grid-connected inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0045] Figure 1 Fig. shows the structural schematic diagram of a new energy grid-connected inverter system provided by an embodiment of the present application.

[0046] Figure 2It shows a schematic flowchart of a grid-connected inverter phase-locked loop stability control method based on phase-locked offset compensation provided by an embodiment of the present application;

[0047] Figure 3 It shows a schematic flowchart of a grid-connected inverter phase-locked loop stability control method based on phase-locked offset compensation provided by another embodiment of the present application;

[0048] Figure 4 It shows a waveform diagram of the grid-connected inverter output current before and after adopting the control strategy provided by an embodiment of the present application;

[0049] Figure 5 It shows a schematic structural diagram of a grid-connected inverter phase-locked loop stability control device based on phase-locked offset compensation provided by an embodiment of the present application;

[0050] Figure 6 It shows a schematic structural diagram of a computer device provided by an embodiment of the present application. Detailed implementation manners

[0051] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0052] Please refer to Figure 1 , which shows a schematic structural diagram of a new energy grid-connected inverter system provided by an embodiment of the present application. Among them, the structure of the new energy grid-connected inverter system is divided into two parts: the main circuit and the controller. The topological structure diagram of the main circuit is as shown in the upper half of Figure 1 . The main circuit includes an AC weak grid, a filter, and an inverter connected in sequence. Among them, the filter includes an output filter inductor and a grid-side capacitor C, which is used to attenuate high-frequency switching harmonics. , are the three-phase currents in the abc three-phase stationary coordinate system flowing through respectively. The impedance of the AC weak grid is . Ignoring the DC-side voltage fluctuation of the inverter, an ideal DC source is used to replace the inverter power supply.

[0053] The topological structure diagram of the controller is as shown in the lower half of Figure 1 . The controller includes a phase-locked loop PLL, a current loop ACC, and a pulse width modulation (PWM) signal generator connected in sequence.

[0054] The point of common coupling (PCC) of the main circuit and the controller is located , C and as shown by the dashed box in the figure.

[0055] The specific control process is as follows: The three-phase voltage of C , is transformed into two-phase voltage through Clark and Park transformations. Then is input into the PLL, and the PLL loop can obtain the phase information of in real time and output the phase angle . According to , , the three-phase current of , can be transformed into two-phase . Among them, the three phases are the three axes abc of the stationary coordinate system, and the two phases are the two coordinate axes dq of the rotating coordinate system.

[0056] Then , , and the preset d-axis and q-axis grid current command signals are used as the inputs of the following formula:

[0057]

[0058] where is the Laplace operator, is the rated angular frequency of the grid voltage, is the current loop PI regulator, is the transfer function based on the grid-side capacitor voltage feedforward link, is the compensation matrix transfer function based on the phase-locked frequency offset, is the output filter inductor of the inverter, is the offset frequency output by the phase-locked loop PI regulator;

[0059] The d-axis and q-axis voltage control signals , can be obtained.

[0060] Then, according to the phase angle , and are subjected to Clark and Park transformations to obtain the three-phase modulation signal . The PWM signal generator processes , after pulse width modulation, a PWM switching signal of the power device in the inverter is generated; by processing the PWM switching signal through a drive circuit, the turn-on and turn-off of the power device can be controlled.

[0061] Please refer to Figure 2 , which shows a schematic flowchart of a grid-connected inverter phase-locked loop stability control method based on phase-locked offset compensation provided by an embodiment of the present application. This method can be applied to Figure 1 the new energy grid-connected inverter system shown in

[0062] Step 201: Determine the voltage control signal of the inverter in the two-phase synchronous rotating coordinate system according to the first formula, and the first formula is:

[0063]

[0064] Where , are the d-axis and q-axis voltage control signals respectively, , are the preset d-axis and q-axis grid current command signals, , are the d-axis and q-axis current variables respectively, , are the d-axis and q-axis voltage variables respectively, is the Laplace operator, is the rated angular frequency of the grid voltage, is the current loop PI regulator, is the transfer function based on the grid-side capacitor voltage feedforward link, is the compensation matrix transfer function based on the phase-locked frequency offset, is the output filter inductor of the inverter, is the offset frequency output by the phase-locked loop PI regulator;

[0065] Where , is the current loop proportional regulation coefficient, is the current loop integral regulation coefficient.

[0066] Where , is the feedforward regulation coefficient of the grid-side capacitor voltage.

[0067] Where , is the phase-locked loop bandwidth, , are respectively the proportional regulation coefficient and the low-pass filter regulation coefficient of the qq channel of

[0068] It should be noted that the PI controller is one of the most common control methods in current industrial automation systems. During the automated production process, the PI controller is widely used to precisely control some fuzzy and uncertain industrial processes. The PI controller has two adjustment parameters, namely the proportional gain and the integral time. For example, when applied to the current loop PI controller, the proportional gain is the above-mentioned current loop proportional adjustment coefficient , and the integral time is the above-mentioned current loop integral adjustment coefficient ; Another example is when applied to the phase-locked loop PI controller, the proportional gain is the proportional adjustment coefficient of the phase-locked loop , and the integral time is the integral adjustment coefficient of the phase-locked loop .

[0069] Furthermore, the proportional adjustment coefficient and the low-pass filter adjustment coefficient can be designed according to the following method, and the method further includes:

[0070] Determine , according to the second formula, and the second formula is:

[0071]

[0072] wherein, is the output side inductor current during the steady-state operation of the grid-connected inverter, is the grid side capacitor voltage during the steady-state operation of the grid-connected inverter, is the current loop proportional adjustment coefficient, is the current loop integral adjustment coefficient, is the feedforward adjustment coefficient of the grid side capacitor voltage.

[0073] Even further, before determining , according to the second formula, the method further includes: determining according to the third formula, and determining according to the fourth formula;

[0074] The third formula is:

[0075] ;

[0076] The fourth formula is:

[0077] ;

[0078] wherein, is the rated capacity of the inverter, is the amplitude of the grid voltage.

[0079] Step 202: Control the turning on and off of the power device according to the voltage control signal to achieve stable control of the grid-connected inverter phase-locked loop.

[0080] Further, before determining the voltage control signal of the inverter in the two-phase synchronous rotating coordinate system according to the first formula, the method further includes:

[0081] Collect the three-phase voltages of the grid-side capacitor in the three-phase stationary coordinate system 、 、 ;

[0082] Perform Clark and Park transformations on the three-phase voltages 、 、 to obtain the d-axis and q-axis voltage variables in the two-phase synchronous rotating coordinate system 、 。

[0083] Further, before determining the voltage control signal of the inverter in the two-phase synchronous rotating coordinate system according to the first formula, the method further includes:

[0084] Collect the three-phase currents of the output filter inductor of the inverter in the three-phase stationary coordinate system 、 、 ;

[0085] According to the phase angle of the grid-side capacitor voltage, perform Clark and Park transformations on the three-phase currents 、 、 to obtain the d-axis and q-axis current variables in the synchronous rotating coordinate system 、 , and the phase angle of the grid-side capacitor voltage is obtained after passing through the phase-locked loop by the q-axis voltage variable 。

[0086] Among them, the phase angle of the grid-side capacitor voltage is determined based on the fifth formula, and the fifth formula is:

[0087]

[0088] Among them, is the phase-locked loop PI regulator, is the proportional regulation coefficient of the phase-locked loop, is the integral regulation coefficient of the phase-locked loop.

[0089] Specifically, the controlling the turning on and off of the power device according to the voltage control signal includes:

[0090] The Clark and Park inverse transformation is performed on the voltage control signal according to the phase angle of the grid-side capacitor voltage to obtain the modulation signal in the three-phase stationary coordinate system;

[0091] The modulation signal is subjected to pulse width modulation to generate the PWM switching signal of the power device in the inverter;

[0092] The PWM switching signal is processed through a drive circuit to control the turning on and off of the power device.

[0093] It can be seen that when determining the voltage control signal, the first formula takes into account the phase-locked frequency offset compensation, and the phase-locked frequency offset compensation is determined according to the compensation matrix transfer function and the offset frequency output by the phase-locked loop PI regulator, providing a stable control method for the phase-locked loop of the grid-connected inverter based on phase-locked offset compensation, which is beneficial to canceling the disturbance signal in the phase-locked loop disturbance path of the output impedance model and completing the closed-loop decoupling control of the grid-connected inverter, thereby significantly improving the operation stability of the grid-connected inverter.

[0094] Please refer to Figure 3 , which shows the schematic flow chart of the stable control method for the phase-locked loop of the grid-connected inverter based on phase-locked offset compensation provided by an embodiment of the present application. This method can be applied to a computer device, and the above computer device refers to an electronic device with data calculation and processing capabilities. This method can be applied to Figure 1 the new energy grid-connected AC converter system shown in the figure, and may include the following steps:

[0095] Step 301: Determine the output-side inductor current during the steady-state operation of the grid-connected AC converter according to the third formula , and determine the grid-side capacitor voltage during the steady-state operation of the grid-connected AC converter according to the fourth formula ;

[0096] The third formula is:

[0097] ;

[0098] The fourth formula is:

[0099] ;

[0100] Among them, is the rated capacity of the inverter, is the amplitude of the grid voltage.

[0101] Step 302: Determine the proportional regulation coefficient of the qq channel of and the low-pass filtering regulation coefficient according to the second formula; the second formula is:

[0102]

[0103] Among them, is the proportional regulation coefficient of the current loop, is the integral regulation coefficient of the current loop, is the feed-forward regulation coefficient of the grid-side capacitor voltage.

[0104] Step 303: Determine and to obtain , is the compensation matrix transfer function based on the phase-locked frequency offset; where:

[0105] , where is the phase-locked loop bandwidth.

[0106] Step 304: Collect the three-phase voltage , , of the grid-side capacitor in the three-phase stationary coordinate system and the three-phase current , , of the output filter inductor in the three-phase stationary coordinate system;

[0107] Step 305: Perform Clark and Park transformations on the three-phase voltage , , to obtain the d-axis and q-axis voltage variables , in the two-phase synchronous rotating coordinate system.

[0108] Step 306: According to the phase angle of the grid-side capacitor voltage, perform Clark and Park transformations on the three-phase current , , to obtain the d-axis and q-axis current variables , in the synchronous rotating coordinate system. The phase angle of the grid-side capacitor voltage is obtained after passing the three-phase current through the phase-locked loop, where:

[0109]

[0110] Where is the PI regulator of the phase-locked loop, is the proportional regulation coefficient of the phase-locked loop, is the integral regulation coefficient of the phase-locked loop.

[0111] Step 307: Determine the voltage control signal of the inverter in the two synchronous rotating coordinate systems according to the first formula, where the first formula is:

[0112]

[0113] where and are the voltage control signals of the d-axis and q-axis respectively, and are the preset d-axis and q-axis grid current command signals, and are the current variables of the d-axis and q-axis respectively, and are the voltage variables of the d-axis and q-axis respectively, is the Laplace operator, is the rated angular frequency of the grid voltage, is the current loop PI regulator, is the transfer function based on the grid-side capacitor voltage feed-forward link, is the compensation matrix transfer function based on the phase-locked frequency offset, is the output filter inductor of the inverter, is the offset frequency output by the phase-locked loop PI regulator.

[0114] Step 308: Perform Clark and Park inverse transformation on the voltage control signal according to the phase angle of the grid-side capacitor voltage to obtain the modulation signal in the three-phase stationary coordinate system.

[0115] Step 309: Perform pulse width modulation on the modulation signal to generate the PWM switching signal of the power device in the inverter.

[0116] Step 310: Process the PWM switching signal through the drive circuit to control the turning on and off of the power device.

[0117] It should be noted that the implementation manner of the steps in the embodiments of the present application can refer to the specific implementation manner of the steps in the embodiments shown in Figure 2 and will not be elaborated here.

[0118] In a specific embodiment of the present application, Figure 1 the parameters of the new energy grid-connected inverter system shown in , , , . If , , , then through Figure 2 or Figure 3 the third formula and the fourth formula in the embodiments can be calculated to obtain , ; Design , , , then it can be calculated according to the second formula , ; Furthermore, it can be based on and to determine . Finally, the waveform diagram of the grid connection point current output can be drawn according to the first formula.

[0119] Figure 4 is the waveform diagram of the output current of the grid-connected inverter before and after adopting the control strategy of this application according to the above parameters when the short-circuit ratio of the power grid is 1.2 (SCR = 1.2, extremely weak power grid). From Figure 4 it can be clearly found that: after adopting the embodiment in this application, the grid-connected inverter under an extremely weak power grid can operate stably, and the output current has no distortion; without adopting the embodiment in this application, the output current of the grid-connected inverter is greatly distorted, the harmonic content increases significantly, and the low-frequency oscillation problem of the grid-connected inverter is aggravated.

[0120] Figure 5 shows the structural schematic diagram of the phase-locked loop stable control device of the grid-connected inverter based on phase-locked offset compensation provided by an embodiment of this application, which is applied to the new energy grid-connected AC system. The device includes:

[0121] A control signal determination unit 501, configured to determine the voltage control signal of the inverter in the two-phase synchronous rotating coordinate system according to the first formula, and the first formula is:

[0122]

[0123] where , are the voltage control signals of the d-axis and q-axis respectively, , are the preset grid current command signals of the d-axis and q-axis, , are the current variables of the d-axis and q-axis respectively, , are the voltage variables of the d-axis and q-axis respectively, is the Laplace operator, is the rated angular frequency of the grid voltage, is the current loop PI regulator, is the transfer function based on the grid-side capacitor voltage feed-forward link, is the compensation matrix transfer function based on the phase-locked frequency offset, is the output filter inductor of the inverter, is the offset frequency output by the phase-locked loop PI regulator;

[0124] A switch control unit 502 is configured to control the turning on and off of a power device according to the voltage control signal to achieve stable control of the grid-connected inverter phase-locked loop.

[0125] Figure 6 The structural schematic diagram of a computer device provided by an embodiment of the present application is shown, which includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it realizes the functions of the computer system for the stable control method of the grid-connected inverter phase-locked loop based on phase-locked offset compensation in any of the above embodiments.

[0126] An embodiment of the present application also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a computer, the computer realizes the functions of the computer system for the stable control method of the grid-connected inverter phase-locked loop based on phase-locked offset compensation in any of the above embodiments.

[0127] An embodiment of the present application also provides a computer program product containing instructions. When the instructions are executed by a computer, the computer realizes the functions of the computer system for the stable control method of the grid-connected inverter phase-locked loop based on phase-locked offset compensation in any of the above embodiments.

[0128] It can be understood that the specific examples in the present application are only for helping those skilled in the art to better understand the embodiments of the present application, rather than limiting the scope of the present invention.

[0129] It can be understood that in various embodiments of the present application, the magnitudes of the sequence numbers of the processes do not mean the order of execution is prior or posterior. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0130] It can be understood that the various embodiments described in the present application can be implemented alone or in combination, and the embodiments of the present application do not limit this.

[0131] Unless otherwise specified, all technical and scientific terms used in the embodiments of the present application have the same meaning as commonly understood by those skilled in the technical field of the present application. The terms used in the present application are only for the purpose of describing specific embodiments, and are not intended to limit the scope of the present application. The term "and / or" used in the embodiments of the present application and the appended claims includes any and all combinations of one or more of the related listed items. The singular forms "a", "the above", and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0132] It can be understood that the processor in the embodiments of the present application can be an integrated circuit chip with signal processing capabilities. In the implementation process, the steps of the above method embodiments can be completed by the integrated logic circuit in the hardware of the processor or instructions in the form of software. The above processor can be a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components. It can implement or execute the various methods, steps, and logic block diagrams disclosed in the embodiments of the present application. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor, etc. The steps of the method disclosed in combination with the embodiments of the present application can be directly embodied as being executed and completed by a hardware decoding processor, or executed and completed by a combination of hardware and software modules in the decoding processor. The software module can be located in a mature storage medium in the art such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, or an electrically erasable programmable memory, a register, etc. This storage medium is located in the memory, and the processor reads the information in the memory and combines its hardware to complete the steps of the above method.

[0133] It can be understood that the memory in the embodiments of the present application can be a volatile memory or a non-volatile memory, or can include both volatile and non-volatile memories. Among them, the non-volatile memory can be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory can be a random access memory (RAM). It should be noted that the memory of the systems and methods described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0134] Those of ordinary skill in the art can realize that the units and algorithm steps of the examples described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or by a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present application.

[0135] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the systems, devices, and units described above can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0136] In several embodiments provided in the present application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of units is only a logical function division. In actual implementation, there can be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection to each other can be through some interfaces. The indirect coupling or communication connection of devices or units can be in electrical, mechanical, or other forms.

[0137] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0138] In addition, in each embodiment of the present application, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit.

[0139] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods in each embodiment of the present application. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM), random access memories (RAM), magnetic disks, or optical discs that can store program codes.

[0140] The above are only the specific embodiments of the present application, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present application and should be covered by the protection scope of the present application. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A stable control method for the phase-locked loop of a grid-connected inverter based on phase-locked offset compensation, characterized in that, The method includes: Determining a voltage control signal of an inverter in two identical synchronous rotating coordinate systems according to a first formula, where the first formula is: Wherein, and are the d-axis and q-axis voltage control signals respectively, and are the preset d-axis and q-axis grid current command signals, and are the d-axis and q-axis current variables respectively, and are the d-axis and q-axis voltage variables respectively, is the Laplace operator, is the rated angular frequency of the grid voltage, is the current loop PI regulator, is the transfer function based on the grid-side capacitor voltage feedforward link, is the compensation matrix transfer function based on the phase-locked frequency offset, is the output filter inductor of the inverter, is the offset frequency output by the phase-locked loop PI regulator; Controlling the turning on and off of a power device according to the voltage control signal to achieve stable control of the phase-locked loop of a grid-connected inverter; Among them, , is the phase-locked loop bandwidth, , are respectively the proportional adjustment coefficient and the low-pass filter adjustment coefficient of the qq channel of; The method further includes: Determine according to the second formula and , where the second formula is: Among them, is the inductor current on the output side during the steady-state operation of the grid-connected inverter, is the capacitor voltage on the grid side during the steady-state operation of the grid-connected inverter, is the proportional regulation coefficient of the current loop, is the integral regulation coefficient of the current loop, is the feedforward regulation coefficient of the capacitor voltage on the grid side.

2. The method according to claim 1, wherein Before determining according to the second formula , the method further includes: Determined according to the third formula , and determined according to the fourth formula ; The third formula is: ； The fourth formula is: ； Among them, is the rated capacity of the inverter, is the amplitude of the grid voltage.

3. The method according to claim 1, wherein Before determining the voltage control signal of the inverter in two identical synchronous rotating coordinate systems according to the first formula, the method further includes: Collect the three-phase voltages of the grid-side capacitor in the three-phase static coordinate system , , ; For the three-phase voltage , , , perform Clark and Park transformations to obtain the d-axis and q-axis voltage variables , .

4. The method according to claim 3, wherein Before determining the voltage control signal of the inverter in two identical synchronous rotating coordinate systems according to the first formula, the method further includes: The three-phase currents of the output filter inductor of the collection inverter in the three-phase stationary coordinate system , , ; According to the phase angle of the grid-side capacitor voltage, the three-phase current , , is subjected to Clark and Park transformations to obtain the d-axis and q-axis current variables , in the synchronous rotating coordinate system. The phase angle of the grid-side capacitor voltage is obtained after the q-axis voltage variable passes through a phase-locked loop.

5. The method according to claim 4, wherein The phase angle of the grid-side capacitor voltage is determined based on a fifth formula, where the fifth formula is: Among them, is the PI regulator of the phase-locked loop, is the proportional regulation coefficient of the phase-locked loop, is the integral regulation coefficient of the phase-locked loop.

6. The method according to claim 4 or 5, characterized in that, Controlling the turning on and off of the power device according to the voltage control signal includes: Performing Clark and Park inverse transforms on the voltage control signal according to the phase angle of the grid-side capacitor voltage to obtain a modulation signal in a three-phase stationary coordinate system; Performing pulse width modulation on the modulation signal to generate a PWM switching signal of a power device in the inverter; Processing the PWM switching signal through a driving circuit to control the turning on and off of the power device.

7. A grid-connected inverter phase-locked loop stable control device based on phase-locked offset compensation, characterized in that The device includes: A control signal determination unit for determining a voltage control signal of an inverter in two identical synchronous rotating coordinate systems according to a first formula, where the first formula is: Among them, and are the d-axis and q-axis voltage control signals respectively, and are the preset d-axis and q-axis grid current command signals, and are the d-axis and q-axis current variables respectively, and are the d-axis and q-axis voltage variables respectively, is the Laplace operator, is the rated angular frequency of the grid voltage, is the current loop PI regulator, is the transfer function based on the grid-side capacitor voltage feed-forward link, is the compensation matrix transfer function based on the phase-locked frequency offset, is the output filter inductor of the inverter, is the offset frequency output by the phase-locked loop PI regulator; A switch control unit for controlling the turning on and off of a power device according to the voltage control signal to achieve stable control of the phase-locked loop of a grid-connected inverter; Among them, , is the phase-locked loop bandwidth, , are respectively the proportional adjustment coefficient and the low-pass filter adjustment coefficient of the qq channel of The control signal determination unit is further configured to determine according to the second formula , , and the second formula is: Among them, is the inductor current on the output side during the steady-state operation of the grid-connected AC converter, is the capacitor voltage on the grid side during the steady-state operation of the grid-connected AC converter, is the proportional regulation coefficient of the current loop, is the integral regulation coefficient of the current loop, is the feed-forward regulation coefficient of the capacitor voltage on the grid side.

8. An electronic device, characterized in that, including: A processor and a memory; The processor and the memory are connected, where the memory is used to store a computer program, and the processor is used to call the computer program to execute the method according to any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, where the computer program includes program instructions, and when the program instructions are executed by a processor, the method according to any one of claims 1-6 is executed.

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