Phase compensation method and device applied to grid-connected inverter, equipment and medium

Abstract

The invention discloses a phase compensation method, device and equipment applied to a grid-connected inverter and a medium, and relates to the technical field of power grids, and the method comprises the steps: collecting electric related parameters of the grid-connected inverter and a power grid connected with the grid-connected inverter; determining the phase angle of the three-phase voltage of the power grid according to the electrical related parameters; executing a voltage outer loop control strategy on the grid-connected inverter; and selecting a dynamic calculation method or an engineering application method to carry out phase compensation according to the voltage and current phase delay compensation mode. Unified phase compensation is carried out on factors such as steady-state static error existing in an inverter control system, control delay existing in the control system, digital chip control delay, hardware sampling delay and power grid impedance characteristic change existing in a weak power grid through a dynamic calculation method or an engineering application method, so that the power factor of the grid-connected inverter is improved, and the power factor of the grid-connected inverter is improved. And the output power is improved.

Description

Technical Field

[0001] This application relates to the technical field of power grids, and particularly to a phase compensation method, device, equipment, and medium applied to grid-connected inverters. Background Art

[0002] Grid-connected inverters are the core of new energy power generation equipment such as photovoltaic and energy storage. Grid-connected inverters are generally grid-following types. Therefore, it is required that the output voltage of the inverter follows the change of the grid voltage. At the same time, only when the output current is in the same phase as the grid voltage can the power factor of the inverter output be 1, and the inverter generates electricity for the grid with the maximum active power, thereby improving the power generation conversion efficiency. However, there are still large phase errors in the existing inverter control schemes, which reduces the output power of the inverter. Summary of the Invention

[0003] The main purpose of the embodiments of this application is to propose a phase compensation method, device, equipment, and medium applied to grid-connected inverters to reduce the phase error of grid-connected inverters and improve the output power.

[0004] To achieve the above object, on the one hand, an embodiment of this application proposes a phase compensation method applied to a grid-connected inverter, and the method includes the following steps:

[0005] Collect electrical-related parameters of the grid-connected inverter and the grid to which the grid-connected inverter is connected;

[0006] Determine the phase angles of the three-phase voltages of the grid according to the electrical-related parameters;

[0007] Execute a voltage outer loop control strategy on the grid-connected inverter;

[0008] Select a dynamic calculation method or an engineering application method for phase compensation according to the voltage-current phase delay compensation mode.

[0009] In some embodiments, the collecting electrical-related parameters of the grid-connected inverter and the grid to which the grid-connected inverter is connected includes the following steps:

[0010] Sample the instantaneous values of the DC support capacitor voltage, filter inductor current, filter capacitor voltage, and grid voltage respectively, and correspondingly obtain the DC bus voltage, the three-phase output current of the grid-connected inverter, the three-phase output voltage of the grid-connected inverter, and the three-phase voltage of the grid as the electrical-related parameters.

[0011] In some embodiments, the determining the phase angles of the three-phase voltages of the grid according to the electrical-related parameters includes the following steps:

[0012] Perform phase locking on the three-phase voltages of the grid in the electrical-related parameters to obtain the phase angles of the three-phase voltages of the grid.

[0013] In some embodiments, the dynamic calculation method or the engineering application method is selected according to the voltage-current phase delay compensation mode for phase compensation, including the following steps:

[0014] Perform phase compensation by executing the dynamic calculation method according to the voltage-current phase delay compensation mode; wherein, the steps of executing the dynamic calculation method include: dynamically compensating the dq coordinate system according to whether to perform the compensation phase delay angle base value, whether to perform the reactive current dynamic compensation, and power decoupling;

[0015] Alternatively, perform phase compensation by executing the engineering application method according to the voltage-current phase delay compensation mode; wherein, the steps of executing the engineering application method include: controlling the grid-connected inverter to connect to the grid at a first set power, and then recording the compensation phase delay angle base value; controlling the grid-connected inverter to connect to the grid at a power lower than a second set power, and then recording the i q compensation base value; perform phase compensation according to the compensation phase delay angle base value and the i q compensation base value.

[0016] In some embodiments, the steps of executing the dynamic calculation method include the following steps:

[0017] Determine the reference value of the compensated active current according to Euler's formula and dq transformation;

[0018] The reference value of the compensated active current is:

[0019] I d_ref_com = I d_ref *cosθ com + I q_ref *sinθ com ;

[0020] Wherein, I d_ref_com is the reference value of the compensated active current, I d_ref is the reference value of the active current, I q_ref is the reference value of the reactive current, θ com is the phase angle compensation value;

[0021] The calculation formula of the phase angle compensation value is:

[0022]

[0023] Wherein, i1 is the inductor current, i c is the current of the filter capacitor, i 2 is the grid-connected current, ω is the frequency, C is the capacitance value, Ug a is the voltage of the grid;

[0024] Substitute the reference value of the compensated active current into the current forward channel for phase compensation;

[0025] Recalculate the reference value of the compensated active current according to the fluctuation coefficient;

[0026] The recalculated reference value of the compensated active current is

[0027] I d_ref_com = I d_ref * cosθ com + (1 + K q ) * I q_ref * sinθ com ;

[0028] The fluctuation coefficient is:

[0029]

[0030] where K q is the fluctuation coefficient, Ud is the DC bus voltage, and 220V is the single-phase voltage of the power grid;

[0031] Determine the output voltage of the grid-connected inverter;

[0032] The output voltage of the grid-connected inverter is:

[0033]

[0034] where u 0 , u d , u q are the output voltages of the grid-connected inverter; u a , u b , u c are the output voltages of the grid-connected inverter; t is time;

[0035] Substitute the recalculated reference value of the compensated active current into the current forward channel according to the output voltage of the grid-connected inverter for phase compensation;

[0036] Determine that the reference value of the compensated active current under power decoupling is:

[0037] I d_ref_com = (I d_ref - I d_ref_decouple ) * cosθ com + (I q_ref + K q * (I q_com - I q_ref_decouple )) * sinθ com ;

[0038]

[0039] Among them, I d_ref_com is the reference value of the compensated active current under power decoupling; P inv , Q inv are respectively the active power and reactive power output by the grid-connected inverter;

[0040] Substitute the reference value of the compensated active current under power decoupling into the current forward channel for phase compensation.

[0041] In some embodiments, performing the steps of the engineering application method includes the following steps:

[0042] Judge whether the base value of the phase delay angle is recorded;

[0043] If so, determine the reference value of the compensated active current under power decoupling as:

[0044] I d_ref_com =(I d_ref -I d_ref_decouple )*cosθ com +(I q_ref +K q *(I q_com -I q_ref_decouple ))*sinθ com ;

[0045]

[0046] Among them, I d_ref_com is the reference value of the compensated active current under power decoupling; P inv , Q inv are respectively the active power and reactive power output by the grid-connected inverter;

[0047] Substitute the reference value of the compensated active current under power decoupling into the current forward channel for phase compensation;

[0048] If not, control the grid-connected inverter to connect to the grid at a first set power, and then record the base value of the phase delay angle; control the grid-connected inverter to connect to the grid at a power lower than a second set power, and then record the i q compensation base value; perform phase compensation according to the base value of the phase delay angle and the i q compensation base value.

[0049] In some embodiments, after performing phase compensation by selecting the dynamic calculation method or the engineering application method according to the voltage-current phase delay compensation mode, the method further includes the following steps:

[0050] Perform an internal setpoint within the current loop for the grid-connected inverter, and then execute a current-loop internal control strategy for the grid-connected inverter.

[0051] To achieve the above object, on the other hand, an embodiment of the present application provides a phase compensation device applied to a grid-connected inverter. The device includes:

[0052] A parameter acquisition unit for acquiring electrical parameters related to the grid-connected inverter and the power grid to which the grid-connected inverter is connected;

[0053] A phase angle determination unit for determining the phase angles of the three-phase voltages of the power grid according to the electrical parameters related;

[0054] A voltage control unit for executing a voltage outer-loop control strategy for the grid-connected inverter;

[0055] A phase compensation unit for performing phase compensation by selecting a dynamic calculation method or an engineering application method according to a voltage-current phase delay compensation mode.

[0056] To achieve the above object, on the other hand, an embodiment of the present application provides an electronic device. The electronic device includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the above method is implemented.

[0057] To achieve the above object, on the other hand, an embodiment of the present application provides a computer-readable storage medium. The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the above method is implemented.

[0058] The embodiments of the present application at least include the following beneficial effects:

[0059] The present application can acquire electrical parameters related to the grid-connected inverter and the power grid to which the grid-connected inverter is connected; determine the phase angles of the three-phase voltages of the power grid according to the electrical parameters related; execute a voltage outer-loop control strategy for the grid-connected inverter; and perform phase compensation by selecting a dynamic calculation method or an engineering application method according to a voltage-current phase delay compensation mode. The present application performs unified phase compensation for the steady-state static error existing in the inverter control system, as well as factors such as control delay, digital chip control delay, hardware sampling delay, and changes in grid impedance characteristics under a weak power grid through a dynamic calculation method or an engineering application method, thereby improving the power factor of the grid-connected inverter and increasing the output power. Description of the Drawings

[0060] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0061] Figure 1 It is a schematic flowchart of a phase compensation method applied to a grid-connected inverter provided by an embodiment of the present application;

[0062] Figure 2 It is a topological structure diagram of a TNPC three-level inverter provided by an embodiment of the present application;

[0063] Figure 3 It is a control block diagram of a double closed-loop control strategy provided by an embodiment of the present application;

[0064] Figure 4 It is a phase schematic diagram of current and voltage provided by an embodiment of the present application;

[0065] Figure 5 It is an example diagram of phase dynamic compensation provided by an embodiment of the present application;

[0066] Figure 6 It is a change schematic diagram of the base value of the phase delay angle provided by an embodiment of the present application;

[0067] Figure 7 、 Figure 8 、 Figure 9 They are respectively example control block diagrams of different control strategies provided by an embodiment of the present application;

[0068] Figure 10 It is an example flowchart of a phase compensation method applied to a grid-connected inverter provided by an embodiment of the present application;

[0069] Figure 11 It is a comparison example diagram of phase compensation provided by an embodiment of the present application;

[0070] Figure 12 It is a structural schematic diagram of a phase compensation device applied to a grid-connected inverter provided by an embodiment of the present application;

[0071] Figure 13 It is a hardware structural schematic diagram of an electronic device provided by an embodiment of the present application. Detailed implementation manners

[0072] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the embodiments of the present application. They are only examples of devices and methods consistent with some aspects of the embodiments of the present application as detailed in the appended claims.

[0073] It can be understood that the terms "first", "second", etc. used in the present application can be used herein to describe various concepts, but unless otherwise specified, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another. For example, without departing from the scope of the embodiments of the present application, the first information can also be referred to as the second information, and similarly, the second information can also be referred to as the first information. Depending on the context, the words "if", "when" as used herein can be interpreted as "when...", "while...", or "in response to determining".

[0074] The terms "at least one", "multiple", "each", "any one", etc. used in the present application, at least one includes one, two or more than two, multiple includes two or more than two, each refers to each of the corresponding multiple, and any one refers to any one of the multiple.

[0075] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used herein are only for the purpose of describing the embodiments of the present application and are not intended to limit the present application.

[0076] Before elaborating on the embodiments of the present application in detail, some related technologies and terms involved in the embodiments of the present application are described first as follows:

[0077] The grid-connected inverter is the core of new energy power generation equipment such as photovoltaic and energy storage. Grid-connected inverters are generally grid-following types. Therefore, it is required that the output voltage of the inverter follows the change of the grid voltage. At the same time, only when the output current is in the same phase as the grid voltage can the power factor of the system output be 1, and the inverter generates electricity for the grid with the maximum active power, thereby improving the power generation conversion efficiency. However, the common inverter control system has a steady-state static error, resulting in a control delay in the control system. At the same time, factors such as the control delay of the digital chip, the hardware sampling delay, and the change of the grid impedance characteristics under a weak grid will all cause a phase deviation between the output current of the grid-connected inverter and the grid voltage. Therefore, it is necessary to compensate the phase of the output current of the grid-connected inverter.

[0078] The related technology 1 provides a phase lead compensation strategy for improving the robustness of the LCL grid-connected inverter under a weak grid, elaborates on the influence of control delay on the LCL grid-connected active damping control characteristics, and proposes a method of connecting a lead phase compensation in series in the capacitor current feedback loop. However, control instability still occurs at the boundary frequency of the active damping equivalent resistance.

[0079] The related technology 2 provides a delay compensation method for improving the current control performance of the LCL grid-connected inverter, and proposes a method of adding a lead compensator in the forward channel of the control system to reduce the influence of control delay on the system. However, the compensation function has a large gain in the high-frequency band, reducing the anti-electromagnetic interference ability of the system.

[0080] The related technology 3 provides an impedance regulation method for improving the grid impedance robustness of the LCL grid-connected inverter. Based on the stability criterion of the grid impedance, an RC branch is added at the grid connection point to regulate the grid impedance characteristics, so as to ensure that the inverter output can match the grid impedance characteristics, thereby compensating for the phase delay of the inverter output. However, the parameters of the RC branch need to be adapted according to the grid, and at the same time, the hardware cost is increased.

[0081] The related technology 4 provides an improved WACC feed-forward phase compensation method for the LCL inverter, elaborates on the instability of the system caused by the LCL reverse resonance peak due to digital control delay, and proposes to add a first-order complex filter to the grid connection point voltage feed-forward, which improves the phase of the inverter output impedance in the low-frequency band. However, under the change of weak grid impedance characteristics and in the high-frequency band, the phase compensation effect deteriorates.

[0082] The existing technologies only separately and specifically compensate for the delay introduced by factors such as control system deviation and digital control. There are many factors that affect the in-phase factor of the inverter output current and the grid, including but not limited to hardware sampling delay, software phase-locked loop delay, grid strength characteristics, external interference, etc. It is difficult to solve the phase deviation caused by other factors by separate compensation alone. At the same time, the improvement of power quality is limited, and there is still a large amount of reactive power output. Therefore, a general phase compensation method is needed, which has better adaptability to scenario conditions and can compensate for phase deviation to the greatest extent as a whole.

[0083] Therefore, the present application provides a phase compensation method, device, equipment and medium for grid-connected inverters. The solution of the present application includes: collecting electrical parameters related to the grid-connected inverter and the grid into which the grid-connected inverter is connected; determining the phase angles of the three-phase voltages of the grid according to the electrical parameters related to the electricity; performing a voltage outer loop control strategy on the grid-connected inverter; and selecting a dynamic calculation method or an engineering application method for phase compensation according to the voltage-current phase delay compensation mode. The present application performs unified phase compensation on the steady-state static error existing in the inverter control system, as well as factors such as control delay, digital chip control delay, hardware sampling delay, and changes in grid impedance characteristics under weak grids through the dynamic calculation method or the engineering application method, thereby improving the power factor of the grid-connected inverter and increasing the output power.

[0084] The embodiments of the present application provide a phase compensation method, device, equipment and medium for grid-connected inverters, which relate to the technical field of power grids. The phase compensation method, device, equipment and medium for grid-connected inverters provided by the embodiments of the present application can be applied to terminals, can also be applied to servers, and can also be software running on terminals or servers. In some embodiments, the terminal can be a smart phone, a tablet computer, a notebook computer, a desktop computer, a smart speaker, a smart watch, a vehicle-mounted terminal, etc., but is not limited thereto; the server side can be configured as an independent physical server, can also be configured as a server cluster or distributed system composed of multiple physical servers, and can also be configured as a cloud server providing basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communications, middleware services, domain name services, security services, CDN, and big data and artificial intelligence platforms. The server can also be a node server in a blockchain network; the software can be an application implementing the phase compensation method for grid-connected inverters, etc., but is not limited to the above forms.

[0085] The present application can be used in many general or special computer system environments or configurations. For example: personal computers, server computers, handheld or portable devices, tablet devices, multi-processor systems, microprocessor-based systems, set-top boxes, programmable consumer electronic devices, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, and so on. The present application can be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The present application can also be practiced in a distributed computing environment, where tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules can be located in local and remote computer storage media including storage devices.

[0086] Reference Figure 1 , an embodiment of the present application provides a phase compensation method applied to a grid-connected inverter, and this method may include but is not limited to S100 to S130, specifically as follows:

[0087] S100: Collect electrical related parameters of the grid-connected inverter and the grid into which the grid-connected inverter is incorporated.

[0088] Further, S100 may include the following steps:

[0089] Sample the instantaneous values of the DC support capacitor voltage, the filter inductor current, the filter capacitor voltage, and the grid voltage respectively, and correspondingly obtain the DC bus voltage, the three-phase output current of the grid-connected inverter, the three-phase output voltage of the grid-connected inverter, and the three-phase voltage of the grid as the electrical related parameters.

[0090] S110: Determine the phase angles of the three-phase voltages of the grid according to the electrical related parameters.

[0091] Further, S110 may include the following steps:

[0092] Perform phase locking on the three-phase voltages of the grid in the electrical related parameters to obtain the phase angles of the three-phase voltages of the grid.

[0093] S120: Execute a voltage outer loop control strategy on the grid-connected inverter.

[0094] S130: Select a dynamic calculation method or an engineering application method for phase compensation according to the voltage-current phase delay compensation mode.

[0095] Further, S130 may include step S131 or S132:

[0096] S131: Perform phase compensation according to the voltage-current phase delay compensation mode by executing the dynamic calculation method; wherein, the steps of executing the dynamic calculation method include: dynamically compensating the dq coordinate system according to whether to perform a compensation phase delay angle base value, whether to perform reactive current dynamic compensation, and power decoupling.

[0097] Further, the steps of executing the dynamic calculation method include the following steps S1311 to S1317:

[0098] S1311: Determine the reference value of the compensated active current according to Euler's formula and dq transformation;

[0099] The reference value of the compensated active current is:

[0100] I d_ref_com = I d_ref *cosθ com + Iq_ref *sinθ com ;

[0101] Wherein, I d_ref_com is the reference value of the compensated active current, I d_ref is the reference value of the active current, I q_ref is the reference value of the reactive current, θ com is the phase angle compensation value;

[0102] The calculation formula of the phase angle compensation value is:

[0103]

[0104] Wherein, i1 is the inductor current, i c is the current of the filter capacitor, i 2 is the grid-connected current, ω is the frequency, C is the capacitance value, Ug a is the voltage of the power grid;

[0105] S1312: Substitute the reference value of the compensated active current into the current forward channel for phase compensation;

[0106] S1313: Recalculate the reference value of the compensated active current according to the fluctuation coefficient;

[0107] The recalculated reference value of the compensated active current is

[0108] I d_ref_com = I d_ref *cosθ com +(1 + K q )*I q_ref *sinθ com ;

[0109] The fluctuation coefficient is:

[0110]

[0111] Wherein, K q is the fluctuation coefficient, Ud is the DC bus voltage, and 220V is the single-phase voltage of the power grid;

[0112] S1314: Determine the output voltage of the grid-connected inverter;

[0113] The output voltage of the grid-connected inverter is:

[0114]

[0115] Wherein, u 0 , u d , u qis the output voltage of the grid-connected inverter; u a , u b , u c is the output voltage of the grid-connected inverter; t is time;

[0116] S1315: Substitute the recalculated reference value of the compensated active current into the current forward channel according to the output voltage of the grid-connected inverter for phase compensation;

[0117] S1316: Determine that the reference value of the compensated active current under power decoupling is:

[0118] I d_ref_com = (I d_ref - I d_ref_decouple ) * cosθ com + (I q_ref + K q * (I q_com - I q_ref_decouple )) * sinθ com ;

[0119]

[0120] wherein, I d_ref_com is the reference value of the compensated active current under power decoupling; P inv , Q inv are the active power and reactive power output by the grid-connected inverter respectively;

[0121] S1317: Substitute the reference value of the compensated active current under power decoupling into the current forward channel for phase compensation.

[0122] S132: Perform phase compensation by executing the engineering application method according to the voltage-current phase delay compensation mode; wherein, the steps of executing the engineering application method include: controlling the grid-connected inverter to connect to the grid at a first set power, and then recording the base value of the phase delay angle; controlling the grid-connected inverter to connect to the grid at a power lower than a second set power, and then recording the i q compensation base value; perform phase compensation according to the base value of the phase delay angle and the i q compensation base value.

[0123] Furthermore, the steps of executing the engineering application method include the following steps S1321 to S1324:

[0124] S1321: Determine whether the base value of the phase delay angle is recorded;

[0125] S1322: If so, determine that the reference value of the compensated active current under power decoupling is:

[0126] I d_ref_com = (I d_ref - I d_ref_decouple ) * cosθ com + (I q_ref + K q * (I q_com - I q_ref_decouple )) * sinθ com ;

[0127]

[0128] wherein, I d_ref_com is the reference value of the compensated active current under power decoupling; P inv , Q inv are respectively the active power and reactive power output by the grid-connected inverter;

[0129] S1323: Substitute the reference value of the compensated active current under power decoupling into the current forward channel for phase compensation;

[0130] S1324: If not, control the grid-connected inverter to connect to the grid at a first set power, and then record the base value of the phase delay angle; control the grid-connected inverter to connect to the grid at a power lower than a second set power, and then record the i q compensation base value; perform phase compensation according to the base value of the phase delay angle and the i q compensation base value.

[0131] Furthermore, after S130, the embodiments of the present application may further include the following steps:

[0132] S140: Perform internal current loop setting on the grid-connected inverter, and then execute the internal current loop control strategy on the grid-connected inverter.

[0133] Next, the solution of the embodiments of the present application will be introduced and described in detail with specific application examples.

[0134] 1. The topological structure of the TNPC three-level inverter is as Figure 2 shown. It is necessary to sample the instantaneous values of the DC support capacitor voltage, filter inductor current, filter capacitor voltage, and grid voltage respectively to obtain the corresponding DC bus voltage Udc, three-phase output currents i a , i b , i c , output voltages u a , u b , u c , and grid voltages Ug a , Ug b , Ug c ;

[0135] 2. Phase-lock the grid voltage Ug a 、Ug b 、Ug c to obtain the three-phase voltage phase angles θ a 、θ b 、θ c ;

[0136] 3. Convert the three-phase AC quantity control into the dq-axis DC quantity control:

[0137] (1) First, determine the mathematical model of the inverter according to the KVL law in the abc coordinate system as:

[0138]

[0139] where R is the three-phase equivalent resistance and can be ignored;

[0140] (2) According to the three-phase abc-dq transformation theory, we can get:

[0141]

[0142] From ωt = θ a it can be obtained that:

[0143]

[0144] (3) Substitute Equation 3 into Equation 1 to get:

[0145]

[0146] where:

[0147] I d 、I q are the d- and q-components of the inverter output current;

[0148] Ug d 、Ug q are the d- and q-components of the grid voltage;

[0149] (4) The active power P inv and reactive power Q inv output by the grid-connected inverter can be obtained respectively as:

[0150]

[0151] (5) Decouple Equation 4 according to Ug q = 0, and perform separate control of I d 、I q to obtain:

[0152]

[0153] Wherein:

[0154] I d_ref 、I d_ref are the current reference values of I d 、I q ;

[0155] G c is the current loop regulator, which is controlled by PI, and its transfer function is

[0156] (5) Adding Udc to the voltage outer loop control gives a double closed-loop control strategy, and the control block diagram is shown in Figure 3 .

[0157] When decoupling the current, the following equivalence is adopted:

[0158]

[0159] Where P dc is the input power on the DC side;

[0160] (6) Referring to Figure 4 , since the control samples the inductor current, that is, the current on L1, and the grid-connected current is the current i1 on L1 minus the current ic of the filter capacitor, that is, i2 = i1 - ic. Therefore, even if the current on L1 is completely in the same frequency and phase as the grid voltage, the grid-connected current will still have a certain angle difference from the voltage. From the grid-connected current vector diagram, it can be seen that even if i1 is in phase with Ug, due to the influence of the filter capacitor current ic, the actual grid-connected current i2 still has an angle difference from Ug.

[0161] Since I d 、I q in formula 5 come from the dq values of the current IL on the filter inductor side, so I d 、I q lack the dq components of ic, that is, there is a phase angle difference between the inductor current and the grid-connected current. Therefore, it is necessary to compensate the dq components of Ic for I d 、I q . However, I d 、I q are the feedback links of the closed-loop system, and direct compensation will cause changes in the control characteristics of the system and bring instability to the system; according to formula 6, for I d_ref 、I q_refIt is only necessary to compensate for the delay phase, which is equivalent to compensating in the forward channel of the closed-loop system, equivalent to adding a lead compensator, and has a compensating effect on the phase lag delay. Overall, the phase difference between the output voltage and current of the grid-connected inverter comes from control delay, digital delay, sampling delay, grid impedance characteristics, etc., but ultimately can be uniformly compensated on the control system, which is equivalent to directly compensating for the phase delay angle caused by these reasons, and finally making the output voltage and current in the same phase;

[0162] According to Euler's formula and dq transformation, the compensated active current I d and reactive current I q reference values are:

[0163]

[0164] where θ _com is the phase angle compensation value;

[0165] (7) The phase angle compensation value θ com in formula (8) can be obtained in the following way:

[0166] According to the grid-connected current vector diagram, it can be obtained that:

[0167]

[0168] It can be seen that the included angle between the grid-connected current i 2 and the inductor current i1 is determined by the grid voltage Ug a , frequency ω, capacitance value C and grid-connected current i2 together; first, let the grid voltage and frequency change little and be invariant. When the filter capacitor is at different constant values, it can be seen that as the grid-connected current i 2 increases, θ _com also decreases accordingly. Therefore, one method can calculate θ _com in real time through formula (9) for phase dynamic compensation;

[0169] The first method requires sampling the instantaneous value of the grid current i2 for real-time calculation. This embodiment can also adopt another equivalent method, such as Figure 4 It can be seen that θ _com gradually decreases and tends to a stable value as i 2 increases, that is, the phase delay angle base value θ _com_base . Since the LC filter parameters of the grid-connected inverter have been determined by the hardware, it can be seen that θ _com_base is also correspondingly determined. Considering the actual engineering application here, a second method is given. When the power is full, that is, when i 2 is large enough, at this time θ _com_base is a fixed value, and the phase angle deviation on the power analyzer is recorded as the deviation impedance angle of the inverter output, that is, the phase delay angle base value θ_com_base ;

[0170] Thus, the magnitude of i2 changes. According to Compensation Formula 8, it can be known that the corresponding feedback I d 、I q also changes accordingly to offset the influence brought by i2;

[0171] (8) The above two methods are used to calculate θ _com based on the assumption that the grid voltage remains unchanged, and the standard grid voltage amplitude is set as In fact, the actual grid voltage is affected by the grid impedance characteristics and there will be voltage fluctuations. The voltage acting on the capacitor will also change. The magnitude of the capacitor current ic can be obtained by calculating ic = 2πfCUc. Therefore, by compensating a reactive current on I q the influence of the capacitor current can be offset. The compensation value on I q is given as the peak value, and approximately needs to be compensated. Through the above calculations, it is found that the magnitude of the current to be compensated is related to the magnitude of the grid voltage. Therefore, the finally actual compensation value will be adjusted according to the grid voltage U m . The fluctuation coefficient is

[0172] Formula 8 becomes:

[0173]

[0174] For the reactive power, as the grid current i2 decreases, the reactive power has a minimum value, which mainly comes from the reactive power output by the filter capacitor. Therefore, under low power, the deviation reactive current base value i q_com ,

[0175] Therefore, Formula 9 can be equivalent to:

[0176]

[0177] (9) The dq0 transformation is actually a decoupling control method. For the power under dq0, the power can also be decoupled to compensate the current on dq. Since Formula 2 ignores the voltage and current on the 0 coordinate axis and the zero-sequence component of the inverter output, in fact, the inverter output voltage dq0 transformation is:

[0178]

[0179] The inverter output current dq0 transformation is:

[0180]

[0181] If there is a zero-sequence component in the inverter output, that is, u 0 、I 0Not equal to 0; let I d0 be the current component acting on the 0-axis, and I q0 be the orthogonal component perpendicular to the 0-axis. Then the instantaneous power on the 0-axis is:

[0182] P 0 = u 0 *I d0 + u 0 *I q0 (Formula 13)

[0183] According to Formula 5 and Formula 13 and substituting them into Formula 12, it can be found that the currents I 0 、I d 、I q can be decoupled and compensated through the instantaneous powers P 0 、P inv 、Q inv . The formula is:

[0184]

[0185] where U dq 2 = U d 2 + U q 2 ;

[0186] The decoupling amount acting on the dq current command is:

[0187]

[0188] Therefore, Formula 9 is further compensated as:

[0189]

[0190] Because the zero-sequence component decoupled from the 0-axis power is also affected by the grid voltage fluctuation, Formula 16 is further transformed into:

[0191]

[0192] Next, the implementation method of the engineering application method will be described.

[0193] 1. Perform relevant voltage and current sampling according to the topology of the TNPC three-level inverter:

[0194] (1) On the DC side, it is necessary to sample the support capacitor voltage Udc and the DC current Idc.

[0195] (2) On the AC side, it is necessary to sample the instantaneous values of the filter inductor current, the filter capacitor voltage, and the grid voltage respectively to the corresponding three-phase output currents i a 、i b, i c , the output voltage u a , u b , u c , and the grid voltage Ug a , Ug b , Ug c .

[0196] (3) The sampling deviation accuracy directly affects the magnitude of the phase delay angle of the grid-connected voltage and current, and it is necessary to calibrate the relevant accuracy and zero drift to meet the design standards.

[0197] 2. Before grid connection, it is necessary to preprocess the support capacitor and the filter capacitor:

[0198] (1) The relay on the DC side is used to close the DC source to charge the support capacitor, and another soft-start circuit can be set up to perform soft start on the capacitor before grid connection.

[0199] (2) Sample the DC bus voltage and judge whether it reaches the voltage required for inversion. If so, close the DC relay.

[0200] (3) It is necessary to charge the AC-side filter capacitor to prevent a voltage difference from occurring during direct grid connection, which may cause a phase delay at the moment of grid connection.

[0201] (4) The filter capacitor is pre-charged in an open-loop manner to prevent an over-current spike problem at the output caused by a phase difference when the filter capacitor is connected to the grid.

[0202] 3. Perform improved DSOGI phase-locking on the grid voltage Ug a , Ug b , Ug c to obtain the three-phase voltage phase angles θ a , θ b , θ c , and the method is as follows:

[0203] (1) Perform three-phase DSOGI phase-locking on the phases of the three-phase grid voltage to obtain θ a ^, θ b ^, θ c ^.

[0204] (2) Perform SOGI single-phase phase-locking on the phases of the three-phase grid voltage respectively to obtain θ a ′, θ b ′, θ c ′.

[0205] (3) Correct the phases of the three-phase grid voltage to obtain θ a = θ a ^ + θ a ′, θ b = θ b ^ + θb ′, θ c = θ c ^ + θ c ′.

[0206] (3) Most of the control delay of the grid-connected voltage and current comes from the phase difference between the voltage and current caused by the phase-locked loop delay. Therefore, a single-loop SOGI needs to be used to correct the phase angle of the three-phase DSOGI respectively. The delay between the corrected phase angle and the grid voltage phase is smaller, and the dynamic performance is also better.

[0207] 4. Establish a mathematical model for the TNPC three-level grid-connected inverter, and convert the control of three-phase alternating quantities into the control of direct current quantities in the dq frame:

[0208] (1) First, according to Kirchhoff's voltage law in the abc coordinate system, list the voltage equivalent equation for the three-phase loop to determine the mathematical model of the inverter as:

[0209]

[0210] where R is the three-phase equivalent resistance and can be ignored;

[0211] (2) According to the three-phase abc to dq transformation theory, we can get:

[0212]

[0213] From ωt = θ a we can get:

[0214]

[0215] (3) Substitute Equation 3 into Equation 1 to get:

[0216]

[0217] where:

[0218] i d 、i q are the d and q components of the inverter output current;

[0219] Ug d 、Ug q are the d and q components of the grid voltage;

[0220] (4) The active power P inv and reactive power Q inv output by the grid-connected inverter can be obtained as:

[0221]

[0222] (5) According to Ug q= 0 decouples formula 4, and can separately control i d and i q individually, resulting in:

[0223]

[0224] Where:

[0225] I d_ref and I q_ref are the current reference values of I d and I q ;

[0226] G c is the current loop regulator, controlled by PI, and its transfer function is

[0227] (6) When performing decoupled control of the current, the following equivalence is adopted:

[0228]

[0229] Where P dc is the input power on the DC side;

[0230] (7) Adding Udc to the voltage outer loop control gives the traditional double closed-loop control strategy, and the control block diagram still refers to Figure 3 ;

[0231] 5. The phase difference between the voltage and current output by the grid-connected inverter mainly comes from control delay, digital delay, sampling delay, grid-connected impedance characteristics, etc. It is equivalent to directly compensating for the change in the base value of the phase delay angle caused by these reasons, and finally appears in the entire control system. Unified angular dynamic compensation can be performed, and the method is as follows:

[0232] (1) Still referring to Figure 4 , first analyze the grid-connected voltage and current vector diagram. Since the control samples the inductor current, that is, the current on L1, and the grid-connected current is the current i1 on L1 minus the current ic of the filter capacitor, that is, i2 = i1 - ic. Therefore, even if the current on L1 is completely in the same frequency and phase as the grid voltage, the grid-connected current will still have a small angle difference from the voltage. From the grid-connected current vector diagram, it can be seen that even if i1 is in phase with Ug, due to the influence of the filter capacitor current ic, the actual grid-connected current i2 still has an angle difference from Ug.

[0233] (2) Since I d and I q in formula 5 come from the dq values of the current IL on the filter inductor side, so I d and I q lack the dq components of ic, that is, there is a phase angle difference between the inductor current and the grid-connected current. Therefore, it is necessary to correct I d, I q Perform dq component compensation for the ic. However, I d , I q is the feedback link of the closed-loop system. Direct compensation will change the control characteristics of the system and cause system instability. According to Equation 6, it can be seen that for I d_ref , I q_ref compensating the delay phase is sufficient, which is equivalent to compensating in the forward path of the closed-loop system and is equivalent to adding a lead compensator, which has a compensating effect on the phase lag delay.

[0234] (3) According to Euler's formula and dq transformation, the compensated active current i d and reactive current i q reference values are:

[0235]

[0236] where θ _com is the phase angle compensation value;

[0237] 6. After compensating based on the 5 delay angle base value, perform reactive current dynamic compensation. The method is as follows:

[0238] (1) The compensation angle θ com in Equation 8 can be obtained according to the calculation method:

[0239] According to the grid-connected current vector diagram, it can be seen that:

[0240]

[0241] It can be seen that the included angle between the grid-connected current i 2 and the inductor current i1 is jointly determined by the grid voltage Ug a , frequency ω, capacitance value C, and grid-connected current i2. First, let the grid voltage and frequency change slightly and be invariant. When the filter capacitor capacitance value is different constant values (as shown in the figure as 5uf, 8uf, 10uf), it can be seen that as the grid-connected current i 2 increases, θ _com also decreases accordingly. Therefore, one method can calculate θ _com in real time through Equation 9 for phase dynamic compensation; Figure 5 is an example diagram of a phase dynamic compensation;

[0242] (2) The first method requires sampling the instantaneous value of the grid current i2 for real-time calculation. Here, another equivalent method is adopted. Referring to Figure 6 , it can be seen that θ _com gradually decreases and approaches a stable value as i 2 increases, that is, the phase delay angle base value θ _com_base, since the LC filter parameters of the grid-connected inverter have been determined by the hardware, it can be seen that θ _com_base is also correspondingly determined. Considering the actual engineering application here, a second method is given. When the full power is reached, that is, when i 2 is large enough, the θ _com_base at this time is a fixed value. By recording the phase angle deviation on the power analyzer as the deviation impedance angle of the inverter output, that is, the phase delay angle base value θ _com_base ;

[0243] From this, as the magnitude of i2 changes, according to compensation formula 8, it can be seen that the corresponding feedback I d 、I q also changes correspondingly to offset the influence brought by i2;

[0244] (3) Refer to Figure 7 , the above two methods calculate θ _com on the basis that the grid voltage remains unchanged. It is set that the standard grid voltage amplitude is The actual grid voltage will still fluctuate due to the influence of the grid impedance characteristics, and the voltage acting on the capacitor will also change. The magnitude of the capacitor current ic can be obtained by calculating ic = 2πfCUc. Therefore, by compensating a reactive current on I q , the influence of the capacitor current can be offset. The compensation value given on I q is the peak value, and about needs to be compensated. Through the above calculations, it is found that the magnitude of the current to be compensated is related to the magnitude of the grid voltage. Therefore, the final actual compensation value will be adjusted according to the grid voltage U m . The fluctuation coefficient is

[0245] Formula 8 becomes:

[0246]

[0247] (4) Refer to Figure 8 , for the reactive power, as the grid current i2 decreases, the reactive power has a minimum value. This value mainly comes from the reactive power output by the filter capacitor. Therefore, at low power, the deviation reactive current base value I q_com of the inverter output can be found. Therefore, formula 9 can be equivalent to:

[0248]

[0249] 7. After the phase delay angle base value compensation based on 5 and the dynamic compensation of the reactive current in 6, the dynamic compensation of the power decoupling current is carried out. The method is as follows:

[0250] (1) The dq0 transformation is actually a decoupling control method. For the power under dq0, the power can also be decoupled to compensate for the current on dq. Since Equation 2 ignores the voltage and current on the 0-axis and the zero-sequence component of the inverter output, in fact, the inverter output voltage dq0 transformation is:

[0251]

[0252] The inverter output current dq0 transformation is:

[0253]

[0254] (2) If there is a zero-sequence component in the inverter output, that is, u 0 、I 0 is not zero; let I d0 be the current component acting on the 0-axis, and I q0 be the orthogonal component perpendicular to the 0-axis. Then the instantaneous power on the 0-axis is:

[0255] P 0 =u 0 *I d0 +u 0 *I q0 (Equation 13)

[0256] (3) Substituting Equation 5 and Equation 13 into Equation 12, it can be found that the currents I 0 、I d 、I q can be decoupled and compensated through the instantaneous powers P 0 、P inv 、Q inv . The equation is:

[0257]

[0258] where U dq 2 =U d 2 +U q 2 ;

[0259] (4) The decoupling amount acting on the dq current reference is:

[0260]

[0261] Therefore, Equation 9 is further compensated as:

[0262]

[0263] (5) Refer to Figure 9, since the zero-sequence component decoupled from the 0-axis power is also affected by the grid voltage fluctuation, formula 16 is further transformed into:

[0264]

[0265] 8. Add I d_ref_com and I q_ref_com to the forward path of the current inner loop of the double-loop control system, and perform corresponding control on the active current I d and I q The method is as follows:

[0266] (1) The input of the active current inner loop control is taken as the reference active current according to I d_ref_com = (I d_ref - I d_ref_decouple ) * cosθ com + (I q_ref + K q * (I q_com - I q_ref_decouple )) * sinθ com ;

[0267] (2) The input of the reactive current inner loop control is taken as the reference reactive current according to I q_ref_com = -(I d_ref - i d_ref_decouple ) * sinθ com + (I q_ref + K q * (I q_com - I q_ref_decouple )) * cosθ com ;

[0268] (3) After decoupling through the inductor currents I d and I q , perform voltage feedforward control, output the reference voltage to the inverse Park transformation, output three-phase modulation waves, and finally perform in-phase stacked carrier SPWM modulation to control the IGBT to generate waves and connect to the grid.

[0269] 9. The phase delay compensation of this method is shown in the specific steps of process Figure 10 ;

[0270] 10. For the measured 40KW PV grid-connected inverter with L1 = 270uH, C = 8uf, and Lg = 150uH:

[0271] (1) Test the traditional without phase compensation (mode 0), phase angle base value compensation (mode 1), phase angle base value and reactive current Iq compensation (mode 2), phase angle base value and reactive current Iq compensation and power decoupling dq current compensation (mode 3) respectively

[0272] (2) Test the corresponding grid-connected voltage and current phase delay angles under different modes and power ranges:

[0273] (3) Figure 11 As shown, it can be seen that mode 3 is better than mode 2, which is better than mode 1, which is better than mode 0.

[0274] In summary, this embodiment includes the following key technical features:

[0275] 1. The calculation method of voltage and current phase delay angle and the method of obtaining its base value in engineering;

[0276] 2. Adjust reactive current dynamic compensation according to changes in grid characteristics;

[0277] 3. Power decoupling compensation is performed for the influence of zero-sequence components, which improves the adaptability of the power grid;

[0278] 4. Active current setting I in the forward channel of the control system d_ref , reactive current given I q_ref Direct compensation on the board makes it easy to add compensation, simple and easy to implement;

[0279] 5. The dynamic compensation of reactive current and power decoupling compensation are superimposed to improve the system stability and phase margin.

[0280] This embodiment also provides the following alternatives:

[0281] 1. Determine the Lg interval of the inverter's adaptability in weak power grid based on impedance characteristics;

[0282] 2. Use the power grid simulator to set its maximum input impedance Lg _max ;

[0283] 3. According to the inverter equivalent model, the maximum compensation angle limit value θ under system stability is obtained _max ;

[0284] 4. Under full power, find the deviation impedance angle of the inverter output as the base value of the phase delay angle θ _com_base , and Lg _max Compare and select the smaller value as the phase angle compensation value θ _com ;

[0285] 5. Under low power, find the reactive current deviation value output by the inverter as the base value Iq for dynamic reactive current compensation _dynammic_base Then, according to the value of the fundamental positive sequence component Ud of the grid voltage, the dynamic compensation coefficient of the reactive current Iq is determined. Among them, Um is the amplitude of the grid voltage, and finally the dynamic reactive power compensation value Iq is obtained. _com =Iq _k*Iq _dynamic_base ;

[0286] 6. Calculate the reference values of active power and reactive power according to the following formula:

[0287] P _inv = 1.5 * (Ud * Id_ref + Uq * Iq_ref); Q _inv = 1.5 * (Uq * Id_ref - Ud * Iq_ref);

[0288] 7. Obtain the sliding mean values of P _inv , Q _inv as P _inv_ave , Q _inv_ave according to the following formula:

[0289] P _inv_ave = 0.9996875 * P _inv_ave + 0.0003125 * P _inv ;

[0290] Q _inv_ave = 0.9996875 * Q _inv_ave + 0.0003125 * Q _inv ;

[0291] 8. Decouple the power in DQ coordinates for three phases to obtain the decoupled components of active power and reactive power:

[0292]

[0293] 9. Substitute θ com , i q_com , K q , -i d_ref_decouple , i q_ref_decouple into the following formula:

[0294]

[0295] 10. Optimize the low-power segment compared with other power segments. The method is as follows:

[0296] Low-power segment: Iq _ref_com = Iq _com - Id _ref_decouple ;

[0297] Other power segments: Iq _ref_com = Iq _com - Iq _k * Id _ref_decouple ;

[0298] Finally, add them to the control of active current Id and reactive current Iq.

[0299] The beneficial effects of this embodiment include:

[0300] 1. From the perspective of the double-loop control of the grid-connected inverter, a mathematical model is established, the root cause of the phase delay is deduced, and a feedforward lead compensation method with a lagging phase angle is introduced in the dq coordinate system from the perspective of the mismatch between the inverter output current and the grid current;

[0301] 2. Directly perform lead compensation in the forward path of the current-loop DQ control, which not only does not change the stability of the control system, but also makes the phase compensation more direct and effective. At the same time, the compensation angle base value under high power includes both the control delay and the sum of the digital delay and the sampling delay;

[0302] 3. Even under a weak grid, when the grid voltage fluctuates and the phase margin decreases, by dynamically adjusting the inverter output impedance characteristics to follow the grid fluctuations, the grid impedance can always be well matched, improving the system phase margin;

[0303] 4. The phase compensation method is based on the original voltage-current double-loop control, which does not affect the control bandwidth and performance of the original system. The added compensation method is simple, convenient and practical;

[0304] 5. Compensate the phase of the output voltage and current caused by various reasons at one time. Even if there are hardware consistency problems in different inverters, direct dynamic compensation is performed for angle correction compensation on the basis of the original compensation;

[0305] 6. The grid-connected voltage-current phase difference compensation of this embodiment compensates the dynamic reactive current for both the change of the grid impedance characteristics and the grid voltage fluctuation, and the effect is remarkable.

[0306] 7. This embodiment considers the influence of the zero-sequence component and decouples and compensates the active and reactive powers, with higher compensation accuracy and more remarkable effect;

[0307] 8. Existing methods only introduce special single compensation for a certain control link. For the change of the grid impedance characteristics, complicated digital calculations are required. There is a delay in digital control itself, so the compensation angle effect is poor and more digital control resources are occupied;

[0308] 9. According to the output curve of the impedance angle and the output current, determine the steady-state impedance angle base value, which only needs to be recorded once at full power. At the same time, find the base value method of reactive power at low power, reducing the calculation amount and facilitating engineering application.

[0309] Referring to Figure 12 , the embodiment of the present application also provides a phase compensation device applied to a grid-connected inverter, which can implement the above-mentioned phase compensation method applied to a grid-connected inverter. The device includes:

[0310] A parameter acquisition unit, configured to acquire electrical-related parameters of a grid-connected inverter and the power grid to which the grid-connected inverter is connected;

[0311] A phase angle determination unit, configured to determine the phase angles of the three-phase voltages of the power grid according to the electrical-related parameters;

[0312] A voltage control unit, configured to execute a voltage outer loop control strategy on the grid-connected inverter;

[0313] A phase compensation unit, configured to perform phase compensation by dynamically calculating method or engineering application method according to the voltage-current phase delay compensation mode selection.

[0314] It can be understood that the content in the above method embodiments is applicable to the device embodiments of the present application. The functions specifically implemented by the device embodiments of the present application are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those of the above method embodiments.

[0315] An embodiment of the present application further provides an electronic device. The electronic device includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the phase compensation method applied to the grid-connected inverter is implemented. The electronic device can be any intelligent terminal including a tablet computer, an in-vehicle computer, etc.

[0316] It can be understood that the content in the above method embodiments is applicable to the device embodiments of the present application. The functions specifically implemented by the device embodiments of the present application are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those of the above method embodiments.

[0317] Please refer to Figure 13 , Figure 13 which schematically shows the hardware structure of an electronic device according to another embodiment. The electronic device includes:

[0318] A processor 1301, which can be implemented in a general-purpose CPU (Central Processing Unit), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits, etc., and is configured to execute relevant programs to implement the technical solutions provided by the embodiments of the present application;

[0319] The memory 1302 can be implemented in the form of a read-only memory (ROM), a static storage device, a dynamic storage device, or a random access memory (RAM), etc. The memory 1302 can store an operating system and other application programs. When implementing the technical solutions provided in the embodiments of this specification through software or firmware, the relevant program codes are stored in the memory 1302 and are called by the processor 1301 to execute the phase compensation method for grid-connected inverters applied in the embodiments of this application;

[0320] The input / output interface 1303 is used to implement information input and output;

[0321] The communication interface 1304 is used to implement communication interaction between this device and other devices. Communication can be achieved through wired means (such as USB, network cable, etc.) or through wireless means (such as mobile network, WIFI, Bluetooth, etc.);

[0322] The bus 1305 transmits information between various components of the device (such as the processor 1301, the memory 1302, the input / output interface 1303, and the communication interface 1304);

[0323] Among them, the processor 1301, the memory 1302, the input / output interface 1303, and the communication interface 1304 achieve communication connections with each other inside the device through the bus 1305.

[0324] The embodiments of this application also provide a computer-readable storage medium. The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements the above-mentioned phase compensation method for grid-connected inverters.

[0325] It can be understood that the content in the above method embodiments is applicable to the embodiments of this storage medium. The functions specifically implemented by the embodiments of this storage medium are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those of the above method embodiments.

[0326] As a non-transitory computer-readable storage medium, the memory can be used to store non-transitory software programs and non-transitory computer-executable programs. In addition, the memory can include high-speed random access memory, and can also include non-transitory memory, such as at least one magnetic disk storage device, a flash memory device, or other non-transitory solid-state storage devices. In some embodiments, the memory optionally includes a memory remotely set relative to the processor, and these remote memories can be connected to the processor through a network. Examples of the above networks include but are not limited to the Internet, an enterprise intranet, a local area network, a mobile communication network, and combinations thereof.

[0327] The embodiments described in the embodiments of the present application are for more clearly explaining the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided by the embodiments of the present application. Those skilled in the art will know that with the evolution of technology and the emergence of new application scenarios, the technical solutions provided by the embodiments of the present application are equally applicable to similar technical problems.

[0328] Those skilled in the art can understand that the technical solutions shown in the figures do not constitute a limitation on the embodiments of the present application, and may include more or fewer steps than those shown in the figures, or combine some steps, or different steps.

[0329] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, that is, they may be located in one place, or may be distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0330] Those of ordinary skill in the art can understand that all or some of the steps in the methods disclosed above, and the functional modules / units in the systems and devices, can be implemented as software, firmware, hardware, and their appropriate combinations.

[0331] The terms "first", "second", "third", "fourth", etc. (if any) in the specification of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not have to be limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products, or devices.

[0332] It should be understood that in this application, "at least one (item)" means one or more, and "a plurality" means two or more. "And / or" is used to describe the association relationship of associated objects and indicates that there can be three relationships. For example, "A and / or B" can mean: only A exists, only B exists, and both A and B exist at the same time. Here, A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single item (item) or plural items (items). For example, at least one (item) of a, b, or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0333] In several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the above 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 between 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.

[0334] The units described above as separate components may or may not be physically separated. 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.

[0335] In addition, in each embodiment of this application, each functional unit 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. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

[0336] When the integrated unit 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 this application, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes multiple instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods of various embodiments of this application. The foregoing storage medium includes: various media that can store programs such as USB flash drives, mobile hard disks, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical discs.

[0337] The preferred embodiments of the embodiments of this application have been described above with reference to the accompanying drawings, and thus do not limit the scope of rights of the embodiments of this application. Any modifications, equivalent replacements, and improvements made by those skilled in the art without departing from the scope and essence of the embodiments of this application shall be within the scope of rights of the embodiments of this application.

Claims

1. A phase compensation method for a grid-connected inverter, characterized in that: The method comprises the following steps: Collecting power-related parameters of the grid-connected inverter and the grid to which the grid-connected inverter is connected; Determining the phase angle of the three-phase voltage of the power grid according to the power-related parameters; Executing a voltage outer loop control strategy on the grid-connected inverter; According to the voltage and current phase delay compensation mode, select the dynamic calculation method or the engineering application method for phase compensation.

2. The phase compensation method for grid-connected inverter according to claim 1, characterized in that: The collecting of power-related parameters of the grid-connected inverter and the grid connected to the grid-connected inverter comprises the following steps: The instantaneous values ​​of the DC support capacitor voltage, the filter inductor current, the filter capacitor voltage and the grid voltage are sampled respectively, and the corresponding DC bus voltage, the three-phase output current of the grid-connected inverter, the three-phase output voltage of the grid-connected inverter and the three-phase voltage of the grid are obtained as the electrical related parameters.

3. The phase compensation method for grid-connected inverter according to claim 1, characterized in that: Determining the phase angle of the three-phase voltage of the power grid according to the power-related parameters comprises the following steps: The three-phase voltage of the power grid in the power-related parameters is phase-locked to obtain the phase angle of the three-phase voltage of the power grid.

4. The phase compensation method for grid-connected inverter according to claim 1, characterized in that: The method of selecting a dynamic calculation method or an engineering application method for phase compensation according to the voltage and current phase delay compensation mode includes the following steps: Executing the dynamic calculation method to perform phase compensation according to the voltage and current phase delay compensation mode; wherein the step of executing the dynamic calculation method includes: dynamically compensating the dq coordinate system according to whether to compensate the phase delay angle base value, whether to perform reactive current dynamic compensation, and power decoupling; Alternatively, the engineering application method is executed according to the voltage and current phase delay compensation mode to perform phase compensation; wherein the steps of executing the engineering application method include: controlling the grid-connected inverter to achieve a first set power to be connected to the grid, and then recording the phase delay angle base value; controlling the grid-connected inverter to be connected to the grid at a power lower than the second set power, and then recording i q compensation base value; according to the phase delay angle base value and the i q Compensation base value for phase compensation.

5. The phase compensation method for grid-connected inverter according to claim 4, characterized in that: The steps of executing the dynamic calculation method include the following steps: Determine the reference value of the compensated active current according to the Euler formula and dq transformation; The reference value of the compensated active current is: I d_ref_com =I d_ref *cosθ com +I q_ref *sinθ com ; Among them, I d_ref_com is the reference value of the active current after compensation, I d_ref is the reference value of active current, I q_ref is the reference value of reactive current, θ com is the phase angle compensation value; The calculation formula of the phase angle compensation value is: Where i1 is the inductor current, i c is the current of the filter capacitor, i2 is the grid current, ω is the frequency, C is the capacitance value, Ug a is the voltage of the power grid; Bringing the reference value of the compensated active current into the current forward channel to perform phase compensation; recalculating a reference value of the compensated active current according to the fluctuation coefficient; The recalculated reference value of the compensated active current is I d_ref_com =I d_ref *cosθ com +(1+K q )*I q_ref *sinθ com ; The coefficient of fluctuation is: Among them, K q is the fluctuation coefficient, Ud is the DC bus voltage, and 220V is the single-phase voltage of the power grid; Determining the output voltage of the grid-connected inverter; The output voltage of the grid-connected inverter is: Among them, u0, u d 、u q is the output voltage of the grid-connected inverter; u a 、u b 、u c is the output voltage of the grid-connected inverter; t is time; Bringing the recalculated reference value of the compensated active current into a current forward channel according to the output voltage of the grid-connected inverter to perform phase compensation; The reference value of the compensated active current under power decoupling is determined as: I d_ref_com =(I d_ref -I d_ref_decouple )*cosθ com +(I q_ref +K q *(I q_com -I q_ref_decouple ))*sinθ com ; Among them, I d_ref_com is the reference value of the compensated active current under power decoupling; P inv , Q inv are respectively the active power and reactive power output by the grid-connected inverter; The reference value of the compensated active current under power decoupling is brought into the current forward channel to perform phase compensation.

6. The phase compensation method for grid-connected inverter according to claim 4, characterized in that: The steps of executing the engineering application method include the following steps: Determining whether the phase delay angle base value is recorded; If so, the reference value of the compensated active current under power decoupling is determined as: I d_ref_com =(I d_ref -I d_ref_decouple )*cosθ com +(I q_ref +K q *(I q_com -I q_ref_decouple ))*sinθ com ; Among them, I d_ref_com is the reference value of the compensated active current under power decoupling; P inv , Q inv are respectively the active power and reactive power output by the grid-connected inverter; Bringing the reference value of the compensated active current under power decoupling into the current forward channel to perform phase compensation; If not, the grid-connected inverter is controlled to be connected to the grid at a first set power, and the phase delay angle base value is recorded; the grid-connected inverter is controlled to be connected to the grid at a power lower than the second set power, and the phase delay angle base value is recorded. q compensation base value; according to the phase delay angle base value and the i q Compensation base value for phase compensation.

7. The phase compensation method for a grid-connected inverter according to any one of claims 1 to 6, characterized in that: After selecting the dynamic calculation method or the engineering application method to perform phase compensation according to the voltage and current phase delay compensation mode, the method further includes the following steps: The grid-connected inverter is given a current loop, and then the grid-connected inverter is controlled by a current loop control strategy.

8. A phase compensation device for a grid-connected inverter, characterized in that: The device comprises: A parameter collection unit, used to collect power-related parameters of the grid-connected inverter and the power grid to which the grid-connected inverter is connected; A phase angle determination unit, configured to determine the phase angle of the three-phase voltage of the power grid according to the power-related parameters; A voltage control unit, used for executing a voltage outer loop control strategy on the grid-connected inverter; The phase compensation unit is used to select a dynamic calculation method or an engineering application method for phase compensation according to the voltage and current phase delay compensation mode.

9. An electronic device, characterized in that: The electronic device comprises a memory and a processor, the memory stores a computer program, and the processor implements the method according to any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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