Grid-connected inverter extreme working condition adaptive power angle compensation stability control method and system

Abstract

The application provides a grid-connected inverter extreme working condition adaptive power angle compensation stable control method and system, calculates active power and reactive power output by the grid-connected inverter; compares the grid voltage amplitude, when the grid voltage amplitude is greater than the threshold value, virtual synchronous generator control is adopted, a power ring generates an internal potential signal and a phase signal, a modulation signal is generated through a virtual impedance and a voltage and current double closed loop part, otherwise, a fault ride-through control is started, an active ring is frozen, the power reference value of the active ring is replaced by the active power output by the grid-connected inverter, and adaptive power angle compensation control is put into the active ring; after the grid voltage returns to the normal range, the fault ride-through mode is kept until the system enters the steady state, the adaptive power angle compensation stable control is exited, the active ring is restarted, and the virtual synchronous generator control mode is entered. The application ensures that the VSG can still be grid-connected during the fault period, and fully plays the active power output capacity of the VSG.

Description

Technical Field

[0001] This invention belongs to the field of new energy grid-connected power generation technology, specifically relating to an adaptive power angle compensation stability control method and system for grid-connected inverters under extreme operating conditions. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Against the backdrop of the rapid development of new energy sources, grid-connected inverters controlled by virtual synchronous generators (VSGs) can support grid voltage and frequency, thereby ensuring the stable operation of the system and facilitating the large-scale grid connection of new energy sources.

[0004] When grid voltage drops due to faults, small-capacity grid-connected inverters or renewable energy grid-connected systems can disconnect from the grid. However, with high renewable energy penetration and VSG control in inverter operation mode, the disconnection of a large number of devices from the grid reduces the system's equivalent inertia, significantly weakening its anti-interference capability and making it highly susceptible to power quality deterioration, even leading to system instability. Therefore, in the context of grid voltage drops, VSGs should possess fault ride-through capability, ensuring stable operation for a certain period during faults to enhance system robustness.

[0005] The inventors have discovered that the main ways to improve the fault ride-through capability of VSG are as follows: (1) Reduce the active power reference value. During a fault, if the active power is reduced to a certain extent, the acceleration area can be smaller than the deceleration area, thus allowing the VSG to operate at a stable operating point. (2) Increase the reactive power reference value. Increasing the reactive power causes the grid connection point voltage to rise, which in turn increases the maximum transmission power, thereby increasing the deceleration area and improving the transient stability of the VSG. (3) Transient power compensation. When a fault occurs, the active power reference value is reduced or the reactive power reference value is increased, and the system automatically exits after stabilization, meaning that the active power reference value and the reactive power reference value are consistent with those before the fault. Methods (1) and (2) are relatively simple and easy to implement, but in method (1), excessive reduction of active power will violate the grid specifications, and in method (2), excessive increase of reactive power will lead to overcurrent. Method (3) cannot solve the scenario where the VSG does not have a stable equilibrium point during a fault.

[0006] In summary, during fault ride-through, grid-connected inverters under VSG control cannot fully utilize their active power output capacity based on the grid voltage drop depth. Therefore, based on the VSG's power angle stability, fully leveraging the VSG's active power output capacity during fault ride-through—that is, maintaining the pre-fault active power output when a stable equilibrium point exists, and outputting active power at maximum capacity according to power angle stability when no stable equilibrium point exists—is crucial for improving the transient stability of the VSG and ensuring stable system operation. Summary of the Invention

[0007] To address the aforementioned problems, this invention proposes an adaptive power angle compensation stabilization control method and system for grid-connected inverters under extreme operating conditions. This invention ensures that the VSG can still operate in grid-connected mode during fault periods and fully utilizes the active power output capability of the VSG.

[0008] According to some embodiments, the present invention adopts the following technical solution:

[0009] An adaptive power angle compensation stability control method for grid-connected inverters under extreme operating conditions includes the following steps:

[0010] Obtain the grid connection point voltage, grid voltage, inverter side current, and DC side voltage, and perform dq transformation on them respectively to obtain the dq axis components of the grid connection point voltage, grid voltage, and inverter side current;

[0011] The active and reactive power output of the grid-connected inverter are calculated based on the dq-axis components of the grid connection point voltage and the inverter-side current.

[0012] Compared with the grid voltage amplitude, when the grid voltage amplitude is greater than the threshold, virtual synchronous generator control is adopted. The power loop generates internal potential signal and phase signal, which generate modulation signal through virtual impedance and voltage and current double closed loop to realize the control of inverter. Otherwise, fault ride-through control is initiated.

[0013] After the fault ride-through control is activated, the active power loop is frozen, the power reference value of the active power loop is replaced with the active power output of the grid-connected inverter, and adaptive power angle compensation control is put into the active power loop.

[0014] After the grid voltage returns to the normal range, maintain the fault ride-through mode, periodically check whether the system is stable, and exit the adaptive power angle compensation stabilization control after stabilization, restart the active power loop, and enter the virtual synchronous generator control mode.

[0015] As an alternative implementation, the specific process of calculating the active and reactive power output of the grid-connected inverter based on the dq-axis components of the grid connection point voltage and the inverter-side current includes: the active power P output by the grid-connected inverter e and reactive power Q e :

[0016]

[0017] Among them, v Cd and v Cq Let i represent the d-axis and q-axis components of the grid connection point voltage, respectively. sd and i sq These represent the d-axis and q-axis components of the inverter-side current, respectively.

[0018] Grid voltage amplitude u m The calculation process includes:

[0019]

[0020] Among them, v gd and v gq These represent the d-axis and q-axis components of the grid voltage, respectively.

[0021] As an alternative implementation, the threshold is 0.9U. Cn U Cn This indicates the rated grid voltage amplitude.

[0022] As an alternative implementation, the specific process of the power loop generating the internal potential signal and the phase signal includes:

[0023]

[0024] Among them, P ref Represents the active power reference values, ω and ω n These represent the actual angular frequency and the rated angular frequency, respectively; J represents the moment of inertia; and D represents the moment of inertia. p Q represents the damping coefficient, θ represents the reference phase, and Q represents the damping coefficient. ref This represents the reactive power reference value, K represents the reactive power loop inertia coefficient, and D... q E represents the reactive power loop voltage droop factor. int This represents the voltage compensation value generated by the reactive power loop, and E represents the internal electromotive force of the virtual synchronous generator.

[0025] As an alternative implementation, the specific process of generating the modulated signal via the virtual impedance and voltage-current dual closed-loop section includes:

[0026]

[0027] Among them, i sdref and i sqref E represents the given values ​​of the inverter-side current on the d-axis and q-axis, respectively. dref and E qref These represent the d-axis and q-axis components of the inverter voltage command, respectively, k pu and kiu k represents the proportional and integral coefficients of the voltage loop, respectively. pi and k ii L represents the proportional and integral coefficients of the current loop, respectively. s Indicates the inverter-side inductance, C f Represents the filter capacitor, ω n Indicates the rated angular frequency, v Cdref and v Cqref The d-axis and q-axis reference signals of the grid connection point voltage are represented respectively, i sd and i sq These represent the d-axis and q-axis components of the inverter-side current, respectively.

[0028] As an alternative implementation method, the specific process of implementing adaptive power angle compensation control in the active power loop includes:

[0029] Calculate the angle of work;

[0030] Based on the active power reference value, set the sampling time for adaptive power angle compensation control and set the initial power angle change step size;

[0031] Calculate the error between the inverter's output active power and power angle at adjacent sampling times, and at the same time calculate the error between the active power reference value at the previous sampling time and the inverter's output active power.

[0032] The error of the inverter's output active power and power angle, as well as the positive and negative generation judgment conditions of the error between the active power reference value and the inverter's output active power.

[0033] Determine whether the error between the active power reference value and the inverter output active power is within the set error threshold. If yes, perform a region judgment; otherwise, calculate the change step size of the power angle and determine the output power angle reference signal based on the value of the judgment condition.

[0034] Output a power angle reference signal to record the inverter output power, power angle, and power angle reference value at the current moment, and participate in the next power angle compensation control.

[0035] Furthermore, the process of generating judgment conditions based on the error of the inverter output active power and power angle, and the positive or negative value of the error between the active power reference value and the inverter output active power includes:

[0036] The judgment condition S is expressed as:

[0037]

[0038] Where, Δp e (k) represents the active power output of the inverter, Δδ(k) represents the error of the power angle, and ΔP represents the error between the active power reference value and the active power output of the inverter.

[0039] The error threshold is a multiple of the active power reference value.

[0040] As an alternative implementation method, the specific process of periodically determining whether the system is stable includes: starting a timer, determining whether the system has entered a steady state after the timer ends, and restarting the timer if it has not entered a steady state, until the system reaches a steady state;

[0041] P ref -P e ≤P th ;

[0042] Among them, P th This represents the active power threshold. If the above formula is satisfied after the timer ends, it indicates that the system is stable.

[0043] An adaptive power angle compensation stability control system for grid-connected inverters under extreme operating conditions includes:

[0044] The data acquisition module is used to acquire the grid connection point voltage, grid voltage, inverter side current and DC side voltage, and perform dq transformation on them to obtain the dq axis components of the grid connection point voltage, grid voltage and inverter side current.

[0045] The calculation module is used to calculate the active and reactive power output of the grid-connected inverter based on the grid connection point voltage and the dq axis components of the inverter side current.

[0046] The first judgment control module is used to compare the grid voltage amplitude. When the grid voltage amplitude is greater than the threshold, virtual synchronous generator control is adopted. The power loop generates internal potential signal and phase signal, which generate modulation signal through the virtual impedance and voltage and current double closed loop to realize the control of the inverter. Otherwise, fault ride-through control is started.

[0047] The adaptive power angle compensation control module is used to freeze the active power loop after the fault ride-through control is started, replace the active power output of the grid-connected inverter with the power reference value of the active power loop, and put adaptive power angle compensation control into the active power loop.

[0048] The second judgment control module is used to maintain the fault ride-through mode after the grid voltage returns to the normal range, periodically judge whether the system is stable, and exit the adaptive power angle compensation stability control after stabilization, restart the active power loop, and enter the virtual synchronous generator control mode.

[0049] An electronic device includes a memory and a processor, as well as computer instructions stored in the memory and running on the processor, wherein the computer instructions, when executed by the processor, perform the steps in the method described above.

[0050] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0051] This invention innovatively proposes an adaptive power angle compensation stability control method for grid-connected inverters under extreme operating conditions, which fully utilizes the active power output capability of the inverter during fault ride-through and ensures the transient stability of the inverter.

[0052] During a fault, if the inverter has a stable equilibrium point, it maintains the active power output as before the fault; otherwise, it outputs active power at maximum capacity based on the power angle stability. Simultaneously, the proposed control method can accelerate the inverter's response speed to active power, thereby enabling the system to quickly enter a stable state.

[0053] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0054] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0055] Figure 1 This is a control structure diagram of a traditional virtual synchronous generator;

[0056] Figure 2 This is a diagram of the adaptive power angle compensation control structure introduced in this invention;

[0057] Figure 3 For the implementation of this invention Figure 2 Flowchart;

[0058] Figure 4 When the grid voltage drops to 0.8pu, the inverter output active power, inverter side current, and power angle waveform under traditional virtual synchronous generator control are shown.

[0059] Figure 5 The waveforms of the inverter output active power, inverter side current, power angle, and power angle compensation value under the improved virtual synchronous generator control of this invention when the grid voltage drops to 0.8pu.

[0060] Figure 6 When the grid voltage drops to 0.6pu, under the control of a traditional virtual synchronous generator, the inverter output active power, inverter side current, and power angle waveform are shown.

[0061] Figure 7 The waveforms of the active power output, inverter-side current, power angle, and power angle compensation value of the inverter under the control of the improved virtual synchronous generator are shown when the grid voltage drops to 0.6 pu. Detailed Implementation

[0062] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0063] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0064] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0065] Where there is no conflict, the embodiments and features described in this application may be combined with each other.

[0066] Example 1

[0067] by Figure 1 As shown, this embodiment uses the operation of a three-phase grid-connected inverter system as an example, but it does not mean that the solution provided in this embodiment can only be used for this system. In this embodiment, the three-phase grid-connected inverter system includes a DC power supply V. dc Filter capacitor C f Filter inductor L s and resistance R s Grid-side inductance L g and resistance R g An AC power grid and a three-phase full-bridge inverter circuit consisting of six IGBT switches.

[0068] The control system of a three-phase grid-connected inverter system includes active loop, reactive loop, power loop, virtual impedance, and voltage and current dual closed loop. The above control loops can all adopt existing technologies, and their control processes will not be described in detail here.

[0069] like Figure 2 As shown, the main improvement of this invention lies in that, during the fault ride-through of the grid-connected inverter, the power reference value P of the active power loop is adjusted according to the operating conditions. ref Replace with P e Adaptive power angle compensation control is implemented in the active power loop.

[0070] The entire technical solution is described below.

[0071] like Figure 3 As shown, the flexible power angle compensation method for grid-connected inverter fault ride-through conditions provided in this implementation case includes the following steps:

[0072] S1: Collect grid connection point voltage, grid voltage, inverter side current, and DC side voltage, and obtain the dq axis components of grid voltage, grid connection point voltage, and inverter side current through dq transformation;

[0073] S2: Calculate the active power P output by the grid-connected inverter based on the dq-axis components of the grid connection point voltage and the inverter-side current. e and reactive power Q e ;

[0074] S3: Detect the grid voltage amplitude u m , when u m Greater than 0.9U Cn At this time, normal virtual synchronous generator control is adopted. The power loop generates internal potential and phase signals, which are then modulated by the virtual impedance and voltage-current dual closed-loop section to achieve inverter control. U Cn Indicates the rated grid voltage amplitude; when u m Less than 0.9U Cn At that time, fault-crossing control is activated;

[0075] S4: After initiating fault ride-through control, freeze the active power loop and set the active power loop power reference value P. ref Replace with P e Adaptive power angle compensation control is implemented in the active power loop;

[0076] S5: After the grid voltage returns to the normal range, maintain the fault ride-through mode, start the timer, and after the timer ends, determine whether the system has entered a steady state. If it has not entered a steady state, restart the timer until the system reaches a steady state.

[0077] S6: After the timer ends and the system enters steady state, exit adaptive power angle compensation control, end fault ride-through mode, and restart the active power loop.

[0078] In this embodiment, step S2 specifically includes the following steps:

[0079] The active power P output by the grid-connected inverter is calculated using the following formula. e and reactive power Q e :

[0080]

[0081] Among them, v Cd and v Cq Let i represent the d-axis and q-axis components of the grid connection point voltage, respectively. sd and i sq These represent the d-axis and q-axis components of the inverter-side current, respectively.

[0082] Step S3 calculates the grid voltage amplitude u using the following formula. m :

[0083]

[0084] Among them, v gd and v gq These represent the d-axis and q-axis components of the grid voltage, respectively.

[0085] The internal electromotive force and phase of the virtual synchronous generator are obtained using the following formula:

[0086]

[0087] Among them, P ref Represents the active power reference values, ω and ω n These represent the actual angular frequency and the rated angular frequency, respectively; J represents the moment of inertia; and D represents the moment of inertia. p Q represents the damping coefficient, θ represents the reference phase, and Q represents the damping coefficient. ref This represents the reactive power reference value, K represents the reactive power loop inertia coefficient, and D... q E represents the reactive power loop voltage droop factor. int This represents the voltage compensation value generated by the reactive power loop, and E represents the internal electromotive force of the virtual synchronous generator.

[0088] The grid connection point voltage reference signal is obtained using the following formula:

[0089]

[0090] Among them, R v and L v and represent virtual resistance and virtual inductance, respectively, v Cdref and v Cqref These represent the d-axis and q-axis reference signals for the grid connection point voltage, respectively.

[0091] The inverter's voltage command is obtained using the following formula:

[0092]

[0093] Among them, i sdref and i sqref E represents the given values ​​of the inverter-side current on the d-axis and q-axis, respectively. dref and E qref These represent the d-axis and q-axis components of the inverter voltage command, respectively, k pu and k iu k represents the proportional and integral coefficients of the voltage loop, respectively. pi and k ii L represents the proportional and integral coefficients of the current loop, respectively. s Indicates the inverter-side inductance, Cf This represents the filter capacitor.

[0094] In this embodiment, step S4 includes the following steps:

[0095] S4.1: Calculate the work angle using the following formula:

[0096] δ=∫(ω-ω n (6)

[0097] Where δ represents the work angle.

[0098] P in equation (3) of S2 ref Replace with P e This achieves the freezing of the active power loop.

[0099] S4.2: Receive the active power reference value from S2, set the sampling time T for adaptive power angle compensation control, and set the initial power angle change step size A. ini .

[0100] S4.3: Calculate the error between the inverter output active power and power angle at time kT (where k represents the kth sampling) and time (k-1)T. Simultaneously, calculate the error between the active power reference value at time kT and the inverter output active power, as follows:

[0101]

[0102] In the formula, ΔP represents the error between the inverter output active power and the active power reference value at time kT, δ(k) and δ(k-1) represent the power angle at time kT and (k-1)T respectively, Δδ(k) represents the error between the power angle at time kT and (k-1)T, and p e (k) and p e (k-1) represent the active power output of the inverter at time kT and (k-1)T respectively, Δp e (k) represents the error in the active power output of the inverter at time kT compared to time (k-1)T.

[0103] S4.4: Based on the errors ΔP, Δδ(k) and Δp e The positive / negative generation condition of (k) can be expressed as:

[0104]

[0105] Then, whether the magnitude of the error ΔP is within the set error threshold is used as a further judgment condition:

[0106]

[0107] In the formula, dp thThis represents the error threshold, where k1 is the error threshold coefficient.

[0108] S4.5: If the active power output of the inverter satisfies equation (9), then a region judgment is performed. If the operating point is located to the left of the power angle curve, then the power angle reference value δ output by the program is set to... ref (k)=δ ref (k-1). If the operating point is located to the right of the power angle curve, then let δ ref (k)=δ ref (k-1)-A ini The operating range of the working point can be determined by the following formula:

[0109]

[0110] S4.6: If the active power output of the inverter does not meet (9), then the step size of the power angle change is calculated according to the following formula:

[0111] A s =k A ΔP(11)

[0112] Where A s k represents the step size of the change in the work angle. A This represents the compensation coefficient for changes in the power angle.

[0113] The output power angle reference signal is then determined based on the value of S, which can be expressed as:

[0114]

[0115] S4.7: Output the power angle reference signal and record the inverter output power, power angle and power angle reference value at this moment, and participate in the next power angle compensation control.

[0116] In this embodiment, step S5 includes the following steps:

[0117] Determine whether the system is stable using the following formula:

[0118] P ref -P e ≤P th (13)

[0119] Among them, P th This represents the active power threshold. If equation (13) is satisfied after the timer ends, the system is considered stable.

[0120] Step S6 includes the following steps:

[0121] Exit power angle compensation control, let δ ref (k) = 0, P refConnect to the active power loop to restart the active power loop.

[0122] The flexible power angle compensation control in this invention is used to fully utilize the active power output capability of the inverter during fault ride-through, and is specifically achieved through the following methods:

[0123] First, if the system has a stable equilibrium point after the grid voltage drops, the power angle reference values ​​can be output according to the above S1-S6.

[0124] If the system does not have a stable equilibrium point after the grid voltage drops, meaning the inverter's maximum output power cannot reach the set value P ref The method proposed in this invention enables the inverter to output maximum power, as follows:

[0125] In this case, ΔP < 0, i.e., X = 0, then S ≤ 3. According to the description in S2, the following formula holds:

[0126]

[0127] Equation (14) allows the operating point to reciprocate at the maximum output power point. With proper parameter settings, the change in the power angle reference value will not be too large, thus enabling the inverter to output at maximum power.

[0128] A simulation was performed on the grid-connected operation of a three-phase grid-connected inverter using the control method provided in this embodiment, under the condition that the grid voltage drops to 0.8U. Cn At the same time, compared with the traditional virtual synchronous generator control method (such as...) Figure 4 (as shown) and the virtual synchronous generator control of the present invention (such as Figure 5 As shown in the figure, the control effect after the test shows that both control methods can enable the inverter to output the set active power P during the fault period. ref However, this implementation method allows for rapid tracking of the given active power, even during fault recovery. This is also true when the grid voltage drops to 0.6U. Cn At that time, the inverter's maximum output power cannot reach P. ref Therefore, traditional virtual synchronous generator control (such as...) Figure 6 The virtual synchronous generator control (as shown) exhibited instability and failed to return to a stable state even after the fault ended. Figure 7 As shown, it can automatically find the inverter's maximum output power, causing the operating point to oscillate back and forth at the maximum power point, with a small power fluctuation range, thus achieving fault ride-through.

[0129] Example 2

[0130] An adaptive power angle compensation stability control system for grid-connected inverters under extreme operating conditions includes:

[0131] The data acquisition module is used to acquire the grid connection point voltage, grid voltage, inverter side current and DC side voltage, and perform dq transformation on them to obtain the dq axis components of the grid connection point voltage, grid voltage and inverter side current.

[0132] The calculation module is used to calculate the active and reactive power output of the grid-connected inverter based on the grid connection point voltage and the dq axis components of the inverter side current.

[0133] The first judgment control module is used to compare the grid voltage amplitude. When the grid voltage amplitude is greater than the threshold, virtual synchronous generator control is adopted. The power loop generates internal potential signal and phase signal, which generate modulation signal through the virtual impedance and voltage and current double closed loop to realize the control of the inverter. Otherwise, fault ride-through control is started.

[0134] The adaptive power angle compensation control module is used to freeze the active power loop after the fault ride-through control is started, replace the active power output of the grid-connected inverter with the power reference value of the active power loop, and put adaptive power angle compensation control into the active power loop.

[0135] The second judgment control module is used to maintain the fault ride-through mode after the grid voltage recovers to the normal range, start a timer, and judge whether the system has entered steady state after the timer ends. If it has not entered steady state, the timer is restarted until the system reaches steady state. If the system enters steady state, the adaptive power angle compensation stabilization control is exited, the active power loop is restarted, and the virtual synchronous generator control mode is entered.

[0136] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0137] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1A device that provides the functions specified in one or more boxes.

[0138] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0139] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0140] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art without creative effort within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for adaptive power angle compensation stability control of a grid-connected inverter under extreme operating conditions, characterized in that, Includes the following steps: Obtain the grid connection point voltage, grid voltage, inverter side current, and DC side voltage, and perform dq transformation on them respectively to obtain the dq axis components of the grid connection point voltage, grid voltage, and inverter side current; The active and reactive power output of the grid-connected inverter are calculated based on the dq-axis components of the grid connection point voltage and the inverter side current. Compared with the grid voltage amplitude, when the grid voltage amplitude is greater than the threshold, virtual synchronous generator control is adopted. The power loop generates internal potential signal and phase signal, which generate modulation signal through virtual impedance and voltage and current double closed loop to realize the control of inverter. Otherwise, fault ride-through control is initiated. After the fault ride-through control is activated, the active power output of the grid-connected inverter is replaced by the power reference value of the active power loop, and adaptive power angle compensation control is put into the active power loop. The specific process of implementing adaptive power angle compensation control in the active power loop includes: Calculate the angle of work; Based on the active power reference value, set the sampling time for adaptive power angle compensation control and set the initial power angle change step size; Calculate the error between the inverter's output active power and power angle at adjacent sampling times, and at the same time calculate the error between the active power reference value at the previous sampling time and the inverter's output active power. The error of the inverter's output active power and power angle, as well as the positive and negative generation judgment conditions of the error between the active power reference value and the inverter's output active power. Determine whether the error between the active power reference value and the inverter output active power is within the set error threshold. If yes, perform a region judgment; otherwise, calculate the change step size of the power angle and determine the output power angle reference signal based on the value of the judgment condition. Output power angle reference signal, record the inverter output power, power angle and power angle reference value at the current moment, and participate in the next power angle compensation control; After the grid voltage returns to the normal range, the fault ride-through mode is maintained, and the system is periodically checked to determine whether it has entered a steady state. When it is in a steady state, the adaptive power angle compensation stabilization control is exited, the active power loop is restarted, and the virtual synchronous generator control mode is entered.

2. The adaptive power angle compensation stability control method for grid-connected inverters under extreme operating conditions as described in claim 1, characterized in that, The specific process of calculating the active and reactive power output of the grid-connected inverter based on the dq-axis components of the grid connection point voltage and the inverter-side current includes: the active power output of the grid-connected inverter. P e and reactive power Q e : in, v Cd and v Cq These represent the d-axis and q-axis components of the grid connection point voltage, respectively. i sd and i sq These represent the d-axis and q-axis components of the inverter-side current, respectively. Grid voltage amplitude u m The calculation process includes: in, v gd and v gq These represent the d-axis and q-axis components of the grid voltage, respectively.

3. The adaptive power angle compensation stability control method for grid-connected inverters under extreme operating conditions as described in claim 1, characterized in that, The threshold is 0.9 U Cn , U Cn This indicates the rated grid voltage amplitude.

4. The adaptive power angle compensation stability control method for grid-connected inverters under extreme operating conditions as described in claim 1, characterized in that, The specific process by which the power loop generates internal potential and phase signals includes: in, P ref This represents the reference value for active power. ω and ω n These represent the actual angular frequency and the rated angular frequency, respectively. J Indicates the moment of inertia. D p Indicates the damping coefficient. θ Indicates the reference phase. Q ref This represents the reference value for reactive power. K Indicates the reactive loop inertia coefficient. D q This represents the reactive power loop voltage droop factor. E int This represents the voltage compensation value generated by the reactive power loop. E This represents the internal electromotive force of the virtual synchronous generator.

5. The adaptive power angle compensation stability control method for grid-connected inverters under extreme operating conditions as described in claim 1, characterized in that, The specific process of generating the modulated signal through the dual closed-loop section of virtual impedance and voltage and current includes: in, i sdref and i sqref These represent the given values ​​of the inverter-side current on the d-axis and q-axis, respectively. E dref and E qref These represent the d-axis and q-axis components of the inverter voltage command, respectively. k pu and k iu These represent the proportional and integral coefficients of the voltage loop, respectively. k pi and k ii These represent the proportional coefficient and integral coefficient of the current loop, respectively. L s Indicates the inverter-side inductance. C f Indicates the filter capacitor. ω n Indicates the rated angular frequency. v Cdref and v Cqref The d-axis and q-axis reference signals represent the grid connection point voltage, respectively. i sd and i sq These represent the d-axis and q-axis components of the inverter-side current, respectively.

6. The adaptive power angle compensation stability control method for grid-connected inverters under extreme operating conditions as described in claim 1, characterized in that, The process of generating judgment conditions based on the errors in the inverter's output active power and power angle, as well as the positive or negative value of the error between the active power reference value and the inverter's output active power, includes: The judgment condition S is expressed as: ； in, p e ( k () represents the active power output of the inverter. δ ( k The error is the angle of attack. P This represents the error between the active power reference value and the inverter's output active power. The error threshold is a multiple of the active power reference value.

7. The adaptive power angle compensation stability control method for grid-connected inverters under extreme operating conditions as described in claim 1, characterized in that, The specific process of periodically determining whether the system is stable includes: starting the timer, determining whether the system has entered a steady state after the timer ends, and restarting the timer until the system reaches a steady state; ； in, P th This represents the active power threshold. If the above formula is satisfied after the timer ends, it indicates that the system is stable.

8. An adaptive power angle compensation stability control system for a grid-connected inverter under extreme operating conditions, characterized in that it includes: The data acquisition module is used to acquire the grid connection point voltage, grid voltage, inverter side current and DC side voltage, and perform dq transformation on them to obtain the dq axis components of the grid connection point voltage, grid voltage and inverter side current. The calculation module is used to calculate the active and reactive power output of the grid-connected inverter based on the grid connection point voltage and the dq axis components of the inverter side current. The first judgment control module is used to compare the grid voltage amplitude. When the grid voltage amplitude is greater than the threshold, virtual synchronous generator control is adopted. The power loop generates internal potential signal and phase signal, which generate modulation signal through the virtual impedance and voltage and current double closed loop to realize the control of the inverter. Otherwise, fault ride-through control is started. The adaptive power angle compensation control module is used to replace the active power output of the grid-connected inverter with the power reference value of the active power loop after the fault ride-through control is started, and to put adaptive power angle compensation control into the active power loop. The specific process of implementing adaptive power angle compensation control in the active power loop includes: Calculate the angle of work; Based on the active power reference value, set the sampling time for adaptive power angle compensation control and set the initial power angle change step size; Calculate the error between the inverter's output active power and power angle at adjacent sampling times, and at the same time calculate the error between the active power reference value at the previous sampling time and the inverter's output active power. The error of the inverter's output active power and power angle, as well as the positive and negative generation judgment conditions of the error between the active power reference value and the inverter's output active power. Determine whether the error between the active power reference value and the inverter output active power is within the set error threshold. If yes, perform a region judgment; otherwise, calculate the change step size of the power angle and determine the output power angle reference signal based on the value of the judgment condition. Output power angle reference signal, record the inverter output power, power angle and power angle reference value at the current moment, and participate in the next power angle compensation control; The second judgment control module is used to maintain the fault ride-through mode after the grid voltage recovers to the normal range, periodically judge whether the system has entered a steady state, exit the adaptive power angle compensation stability control when the system is in a steady state, restart the active power loop, and enter the virtual synchronous generator control mode.

9. An electronic device comprising a memory and a processor, and computer instructions stored in the memory and running on the processor, wherein the computer instructions, when executed by the processor, perform the steps of the method according to any one of claims 1-7.

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