Control method and device of grid-connected converter, controller and grid-connected converter

Abstract

The invention provides a grid-connected converter control method and device, a controller and a grid-connected converter. The method comprises the following steps: monitoring a power grid signal of a common coupling point of a power grid and a grid-connected converter in real time; the power grid signal comprises power grid voltage and / or power grid frequency; if the power grid signal exceeds a first preset range, entering a fault ride-through state, and adjusting a reference filter coefficient into a dynamic filter coefficient in the fault ride-through state; the dynamic filter coefficient is greater than the reference filter coefficient; filtering the power grid voltage by adopting the dynamic filtering coefficient to obtain a voltage feedback value; and carrying out voltage loop control on the grid-connected converter based on the voltage feedback value, outputting a voltage loop control quantity, and generating a control signal of the grid-connected converter by adopting the voltage loop control quantity. According to the method, the control loop can quickly capture the voltage jump of the weak power grid, the adaptive voltage loop control quantity is output in time, the disturbance influence in the weak power grid is effectively counteracted, and the current distortion and the off-grid risk are avoided.

Description

Technical Field

[0001] This invention relates to the field of converter control technology, and in particular to a control method, device, controller, and grid-connected converter for a grid-connected converter. Background Technology

[0002] With the large-scale application of new energy power generation technologies such as photovoltaics and wind power, distributed new energy power plants are mostly connected to the distribution network through grid-connected converters, making weak grid access scenarios increasingly common. On the one hand, new energy resources are mostly distributed in remote areas, requiring long-distance transmission lines to connect to the main grid, leading to increased equivalent impedance at the grid connection point and a decreased short-circuit ratio (SCR), forming a typical weak grid environment. On the other hand, the centralized connection of a high proportion of power electronic equipment further weakens the inertia and voltage support capacity of the grid, making the voltage of weak grids susceptible to disturbances such as power fluctuations and load switching, exhibiting characteristics such as large voltage fluctuation amplitude, high harmonic content, and poor stability. As the core equipment connecting new energy to the grid, the grid-connected converter's control performance directly determines the grid connection stability and power quality of the new energy power generation system. Therefore, control technologies adapted to the complex operating conditions of weak grids have become a key research focus in the industry.

[0003] Existing grid-connected converter control strategies are mostly designed for strong grid scenarios. In weak grid environments, these fixed control parameters are difficult to balance the dynamic requirements of response speed and signal stability. Summary of the Invention

[0004] This invention provides a control method, device, controller, and grid-connected converter for a grid-connected converter, in order to solve the problem of slow control response speed of grid-connected converters in weak power grid environments in the prior art.

[0005] In a first aspect, embodiments of the present invention provide a control method for a grid-connected converter, comprising: Real-time monitoring of the grid signal at the common coupling point between the power grid and the grid-connected converter; the grid signal includes grid voltage and / or grid frequency; If the power grid signal exceeds the first preset range, it enters the fault ride-through state, and in the fault ride-through state, the reference filter coefficient is adjusted to the dynamic filter coefficient; the dynamic filter coefficient is greater than the reference filter coefficient. The grid voltage is filtered using the dynamic filtering coefficients to obtain a voltage feedback value; Based on the voltage feedback value, voltage loop control of the grid-connected converter is performed, and voltage loop control quantity is output. The control signal of the grid-connected converter is generated using the voltage loop control quantity.

[0006] Secondly, embodiments of the present invention provide a control device for a grid-connected converter, comprising: A power grid signal acquisition module is used to monitor the power grid signal at the common coupling point between the power grid and the grid-connected converter in real time; the power grid signal includes power grid voltage and / or power grid frequency. The filter coefficient switching module is used to enter a fault ride-through state if the power grid signal exceeds a first preset range, and to adjust the reference filter coefficient to a dynamic filter coefficient in the fault ride-through state; the dynamic filter coefficient is greater than the reference filter coefficient. A voltage feedforward module is used to filter the grid voltage using the dynamic filtering coefficients to obtain a voltage feedback value; The voltage loop control module is used to perform voltage loop control of the grid-connected converter based on the voltage feedback value, output voltage loop control quantity, and use the voltage loop control quantity to generate the control signal of the grid-connected converter.

[0007] Thirdly, embodiments of the present invention provide a controller, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the control method for a grid-connected converter as described in any possible implementation of the first aspect above.

[0008] Fourthly, embodiments of the present invention provide a grid-connected converter, including the controller described in the third aspect above.

[0009] This invention provides a control method, device, controller, and grid-connected converter for a grid-connected converter. The method triggers a fault ride-through state when the grid voltage exceeds the limit. During this state, the reference filter coefficient is switched to a larger dynamic filter coefficient, enabling the control loop to quickly capture voltage surges in a weak grid and output appropriate voltage loop control quantities in a timely manner. This effectively counteracts disturbances in the weak grid and avoids current distortion and grid disconnection risks. Simultaneously, the clear definition of the fault ride-through state ensures uninterrupted operation of the grid-connected converter during grid anomalies, guaranteeing the continuity of renewable energy generation. Voltage loop control based on dynamically filtered voltage feedback values ​​further improves the accuracy of the control quantities, ultimately achieving a dual improvement in grid stability and power quality under weak grid conditions, solving the problem of slow response speed in existing fixed-parameter control systems in weak grids. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1This is an application scenario diagram of the control method for grid-connected converters provided in the embodiments of the present invention; Figure 2 This is a flowchart illustrating the implementation of the control method for a grid-connected converter provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of the control loop of the control method for the grid-connected converter provided in the embodiments of the present invention; Figure 4 This is a schematic diagram of the control device for a grid-connected converter provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the controller provided in an embodiment of the present invention. Detailed Implementation

[0012] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0013] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described below in conjunction with the accompanying drawings.

[0014] Figure 1 This diagram illustrates an application scenario of the control method for a grid-connected converter provided in an embodiment of the present invention. For example... Figure 1 As shown, taking a photovoltaic grid-connected system as an example, the photovoltaic device is connected to the power grid through a grid-connected converter. Under normal circumstances, the control loop of the grid-connected converter includes an outer current loop and an inner voltage loop. In the outer current loop, the output current setpoint of the grid-connected converter is reduced by the output current feedback value I. o The current difference is obtained, and then input into the first PI controller. The output current loop control value is used as the voltage setpoint of the voltage loop. Then, the voltage setpoint is subtracted from the real-time grid voltage U. g The voltage difference is obtained, and then a voltage loop control value is derived based on the voltage difference. This voltage loop control value is then used to generate a PWM (Pulse Width Modulation) signal to control the grid-connected converter. The grid-connected converter can be a grid-connected inverter or an energy storage converter connected to an energy storage system; no specific restriction is imposed here.

[0015] Currently, the control parameters of grid-connected converters designed for strong power grids are typically set to fixed values ​​or simple segmented settings. In weak power grid environments, these fixed control parameters struggle to balance the dynamic requirements of response speed and signal stability. The filtering coefficients used to ensure signal stability in strong power grids cannot quickly capture voltage fluctuations in weak power grids, leading to slow control loop response, difficulty in timely mitigation of disturbances, and potentially causing grid-connected current distortion, voltage oscillations, or even grid disconnection risks.

[0016] To avoid the aforementioned problems, this application provides a control method for a grid-connected converter. The controller of the grid-connected converter is the executing entity of this method. See [link to relevant documentation]. Figure 2 The flowchart illustrating the implementation of the control method for a grid-connected converter provided in an embodiment of the present invention is described in detail below: S101: Real-time monitoring of the grid signal at the common coupling point between the power grid and the grid-connected converter; the grid signal includes grid voltage and / or grid frequency.

[0017] In this embodiment, the common coupling point is the point where the grid-connected side of the grid-connected converter connects to the power grid. The power grid signal may include grid voltage, grid current, and grid frequency.

[0018] S102: If the power grid signal exceeds the first preset range, it enters the fault ride-through state, and in the fault ride-through state, the reference filter coefficient is adjusted to the dynamic filter coefficient; the dynamic filter coefficient is greater than the reference filter coefficient.

[0019] In this embodiment, fault ride-through state refers to the working mode in which the grid-connected converter does not disconnect from the grid and continues to operate stably and support the grid when the grid signal exceeds the normal operating range. Specifically, it can include high voltage ride-through, low voltage ride-through, overvoltage fault, and undervoltage fault.

[0020] Specifically, when the grid signal is the grid voltage, the first preset range may include an upper voltage limit and a lower voltage limit. If the grid voltage is higher than the upper voltage limit, the grid-connected system is determined to enter a high voltage ride-through state. If the grid voltage is lower than the lower voltage limit, the grid-connected system is determined to enter a low voltage ride-through state.

[0021] Optionally, when the grid signal is the grid frequency, the first preset range may include an upper frequency limit and a lower frequency limit. If the grid frequency is higher than the upper frequency limit, the grid-connected system is determined to have entered a high-voltage ride-through state; or, if the grid frequency shows an upward trend and the rate of change of the grid frequency is greater than a preset rate of change threshold, the grid-connected system is determined to have entered a high-voltage ride-through state. If the grid frequency is lower than the lower frequency limit, the grid-connected system is determined to have entered a low-voltage ride-through state; or, if the grid frequency shows a downward trend and the rate of change of the grid frequency is greater than a preset rate of change threshold, the grid-connected system is determined to have entered a low-voltage ride-through state.

[0022] The baseline filter coefficient is a fixed filter coefficient used under normal grid operating conditions. Its value is typically small, prioritizing signal stability. The dynamic filter coefficient is a filter coefficient switched during fault ride-through, used to improve control response speed when grid fluctuations are significant. When the grid-connected system enters fault ride-through mode, the baseline filter coefficient under normal operating conditions is switched to the dynamic filter coefficient to improve control response speed for scenarios with large grid fluctuations, preventing the grid-connected converter's control from failing to keep up with grid changes.

[0023] S103: The grid voltage is filtered using the dynamic filtering coefficients to obtain a voltage feedback value.

[0024] Specifically, the voltage feedback value is the voltage signal fed back to the control loop after the grid voltage has been filtered, and it is the core input of the voltage loop control. This embodiment uses dynamic filtering coefficients to perform shallow filtering on the grid voltage, which can accelerate the response speed of the voltage feedback value, enabling the control loop to quickly capture voltage changes in weak grids, effectively offset the impact of disturbances in weak grids, and avoid current distortion and grid disconnection risks.

[0025] In this embodiment, the dynamic filtering coefficient can be a fixed value greater than the baseline filtering coefficient; for example, the dynamic filtering coefficient can be 0.1.

[0026] Alternatively, the dynamic filter coefficients can also be dynamic coefficients that vary with the voltage drop / overvoltage depth of the grid voltage. For example, they can be based on the formula... ,in, a Indicates the dynamic filtering coefficients; b The proportionality coefficient can be obtained through prior calibration. This represents the voltage dip depth / overvoltage depth of the mains voltage. The controller can determine the dynamic filtering coefficients based on the above formula, and then use the dynamic filtering coefficients to perform full filtering on the mains voltage to obtain the voltage feedback value.

[0027] S104: Based on the voltage feedback value, perform voltage loop control of the grid-connected converter, output voltage loop control quantity, and use the voltage loop control quantity to generate the control signal of the grid-connected converter.

[0028] In one possible implementation, refer to Figure 3 The specific implementation process of S104 includes: Obtain the current loop output value U of the grid-connected converter. ref ; The voltage loop control quantity is determined based on the difference between the current loop output value and the voltage feedback value.

[0029] refer to Figure 3 The calculation process for the above current loop output value includes: Obtain the output current setpoint I of the grid-connected converter o_ref and the actual value of the output current I o_fdb The output current setpoint I o_ref Subtract the actual value of the output current I o_fdb The output current difference is obtained. The output current difference is input into the first PI controller to obtain the current loop output value U. ref .

[0030] Subsequently, the above-mentioned output value U based on the current loop... ref The specific implementation process for determining the voltage loop control quantity based on the difference between the voltage feedback value and the actual voltage feedback value includes: The current loop output value U ref Subtracting the voltage feedback value yields the voltage loop difference, which is then input into the second PI controller to obtain the voltage loop control quantity.

[0031] After determining the voltage loop control quantity, the voltage loop control quantity is used to generate the PWM signal for controlling the grid-connected converter.

[0032] As can be seen from the above embodiments, this embodiment triggers a fault ride-through state when the grid voltage exceeds the limit. During this state, the reference filter coefficient is switched to a larger dynamic filter coefficient, enabling the control loop to quickly capture voltage surges in the weak grid and output appropriate voltage loop control quantities in a timely manner. This effectively counteracts the impact of disturbances in the weak grid, avoiding current distortion and grid disconnection risks. Simultaneously, the clear division of the fault ride-through state ensures that the grid-connected converter operates continuously during grid anomalies, guaranteeing the continuity of renewable energy generation. Voltage loop control based on the dynamically filtered voltage feedback value further improves the accuracy of the control quantities, ultimately achieving a dual improvement in grid stability and power quality under weak grid conditions. This solves the problem of slow response speed in existing fixed-parameter control systems under weak grid conditions.

[0033] In one possible implementation, the specific implementation process of S103 includes: Multiplying the grid voltage by a first weighting factor yields the first grid voltage component; The first grid voltage component is filtered using the dynamic filtering coefficients to obtain the first voltage value; Subtracting the first grid voltage component from the grid voltage yields the second grid voltage component; The voltage feedback value is obtained by adding the first voltage value to the second grid voltage component.

[0034] Specifically, the first weighting coefficient is a proportional coefficient used to split the grid voltage, determining the proportion of voltage components participating in dynamic filtering. The value range of the first weighting coefficient is... When the power grid is in a normal state,k A value of 1 can be set to filter the entire grid voltage to improve the robustness of system control. When the grid-connected system enters a fault ride-through state, This is to achieve a balance between response speed and control stability.

[0035] In one possible implementation, the specific process of filtering the first grid voltage component using the dynamic filtering coefficient to obtain the first voltage value includes: The first grid voltage component is decomposed into fundamental and harmonic components; The fundamental component is filtered using a third dynamic filter coefficient. The harmonic components are filtered using a fourth dynamic filtering coefficient, wherein the third dynamic filtering coefficient is greater than the fourth dynamic filtering coefficient. The fundamental and harmonic components, after being filtered, are combined to obtain the first voltage value.

[0036] Specifically, the above method can ensure a fast response of the fundamental component, while achieving good noise removal for the noisy harmonic components, thereby improving the response speed and signal quality of the first voltage value.

[0037] As can be seen from the above embodiments, this embodiment, through a differentiated filtering design that partially filters and partially passes through the grid voltage, can overcome the inherent limitations of full filtering. It achieves the stability of the first grid voltage component through dynamic filtering coefficients, and ensures the real-time control through the passing through of the second grid voltage component. The voltage feedback value obtained by superimposing the two components has the advantages of both stability and fast response, making the control performance of the grid-connected converter more stable under complex operating conditions of weak grids.

[0038] In one possible implementation, the specific implementation process of S103 further includes: The grid voltage is transformed from the abc coordinate system to the dq axis coordinate system to obtain the d-axis voltage component and the q-axis voltage component. Multiplying the d-axis voltage component by the third weighting factor yields the fifth grid voltage component; The fifth grid voltage component is filtered using the dynamic filtering coefficients to obtain a second voltage value; Subtract the fifth grid voltage component from the d-axis voltage component to obtain the sixth grid voltage component; The second voltage value is added to the sixth grid voltage component to obtain the d-axis voltage feedback value.

[0039] Multiplying the q-axis voltage component by the fourth weighting factor yields the seventh grid voltage component; The voltage component of the seventh power grid is filtered using the dynamic filtering coefficients to obtain a third voltage value; Subtract the seventh grid voltage component from the q-axis voltage component to obtain the eighth grid voltage component; The third voltage value is added to the eighth grid voltage component to obtain the q-axis voltage feedback value.

[0040] The third weighting coefficient is greater than the fourth weighting coefficient.

[0041] Since the power grid mainly supports the grid voltage by absorbing / outputting reactive power during fault ride-through, the response speed of the reactive power loop needs to be faster than that of the active power loop. Therefore, in this embodiment, the fourth weighting coefficient of the reactive power loop is set to be smaller than the third weighting coefficient of the active power loop in order to improve the control response speed of the reactive power loop.

[0042] In one possible implementation, the specific implementation process of S102 includes: Under the fault ride-through condition, the dynamic filtering coefficient is determined based on the grid short-circuit ratio; Switch the reference filter coefficients to the dynamic filter coefficients.

[0043] In one possible implementation, the grid short-circuit ratio is negatively correlated with the dynamic filtering coefficient.

[0044] Specifically, the short circuit ratio (SCR) represents the ratio of the short circuit capacity at the grid connection point to the rated capacity of the grid-connected converter. It is a core indicator for measuring grid strength. The larger the SCR value, the stronger the grid; the smaller the SCR value, the weaker the grid.

[0045] The dynamic filter coefficient is a filter coefficient matched according to the size of the SCR value. It requires a larger filter coefficient under weak grid conditions to improve the response speed and meet the needs of large voltage fluctuations in weak grids.

[0046] Specifically, to improve computational efficiency, this embodiment classifies the power grid into weak, medium-intensity, and strong grids based on the short-circuit ratio (SCR) value. A weak grid is defined as an SCR value less than a first value; a medium-intensity grid as an SCR value greater than or equal to the first value but less than a second value; and a strong grid as an SCR value greater than or equal to the second value. The first value is less than the second value. For example, the first value can be 2, and the second value can be 3. The controller can determine the current grid type based on its SCR value and then determine the corresponding dynamic filtering coefficient. A higher SCR value corresponds to a lower dynamic filtering coefficient, ensuring signal stability when grid voltage fluctuations are small; conversely, a lower SCR value corresponds to a higher dynamic filtering coefficient, improving control response speed under weak grid conditions.

[0047] As can be seen from the above embodiments, a low SCR (Short Circuit Ratio) value indicates a weak power grid and susceptibility to voltage fluctuations, requiring a larger dynamic filter coefficient to improve response speed; while a high SCR value indicates a strong power grid and good voltage support, requiring a moderate filter coefficient to balance response speed and stability. Therefore, this embodiment, by acquiring the SCR value of the power grid in real time and adjusting the dynamic filter coefficient accordingly, can quickly offset voltage surges in weak power grids and suppress noise interference in strong power grids, further improving the fault ride-through capability and operational stability of the grid-connected converter in power grids of varying strengths.

[0048] In one possible implementation, the specific implementation process for determining the dynamic filter coefficients based on the grid short-circuit ratio includes: The depth of the grid voltage anomaly is determined based on the degree to which the grid voltage deviates from the preset voltage range; The dynamic filtering coefficients are determined based on the grid short-circuit ratio and the anomaly depth of the grid voltage. The abnormal depth of the grid voltage is positively correlated with the dynamic filtering coefficient, and the grid short-circuit ratio is negatively correlated with the dynamic filtering coefficient.

[0049] Specifically, the short-circuit ratio of the power grid can be negatively proportional to the dynamic filtering coefficient.

[0050] In this embodiment, the abnormal depth of the grid voltage includes the voltage drop depth and the overvoltage depth. If the grid voltage is less than the lower limit of the preset voltage range, the lower limit is subtracted from the grid voltage to obtain the voltage difference. Then, the voltage difference is divided by the grid rated voltage to obtain the voltage drop depth. If the grid voltage is greater than the upper limit of the preset voltage range, the grid voltage is subtracted from the upper limit to obtain the voltage difference. Then, the voltage difference is divided by the grid rated voltage to obtain the overvoltage depth.

[0051] After obtaining the anomaly depth of the grid voltage and the grid short-circuit ratio, based on the formula... Determine the first reference value; among which, M Indicates the first reference value. r This represents the second weighting coefficient. Dt Indicates abnormal depth. SCR This represents the short-circuit ratio of the power grid. Among them, .

[0052] Then based on M The magnitude of the value determines the corresponding dynamic filtering coefficient.

[0053] As can be seen from the above embodiments, this embodiment achieves comprehensive perception of grid conditions and precise matching of coefficients through a dual-parameter collaborative design of voltage anomaly depth and SCR value. Voltage anomaly depth reflects the severity of voltage deviation from the normal range; a greater anomaly depth indicates a more prominent grid problem, requiring a larger filter coefficient for rapid response; a smaller anomaly depth indicates a minor problem, allowing for a more appropriate reduction in the filter coefficient to suppress noise. The SCR value reflects grid strength; weak grids require a larger filter coefficient, while strong grids require a smaller one. The combination of these two parameters covers more complex operating conditions. For example, in the case of a weak grid with severe voltage anomalies, the dynamic filter coefficient is set to its maximum value to ensure the fastest response; in the case of a strong grid with minor voltage anomalies, the dynamic filter coefficient is set to a smaller value to balance response and stability. This dual-parameter collaborative logic is more comprehensive and precise than single-parameter settings, avoiding the problem of inappropriate filter coefficient selection caused by single parameters, and making the control performance of the grid-connected converter more stable under diverse weak grid conditions.

[0054] In one possible implementation, the dynamic filtering coefficients include a first filtering coefficient and a second filtering coefficient; the specific implementation process of S103 includes: During the first preset time period of entering the fault ride-through state, the first filtering coefficient is used to filter at least a portion of the grid voltage; After a first preset time period of entering the fault ride-through state, the first filter coefficient is multiplied by a preset adjustment parameter to obtain a second filter coefficient, and the second filter coefficient is used to filter at least a portion of the grid voltage; the preset adjustment parameter is less than 1.

[0055] In this embodiment, since the grid voltage fluctuation is relatively large when entering the fault ride-through state, in order to follow the grid voltage fluctuation more quickly and effectively offset the disturbance effect in the weak grid, this embodiment sets a large filter coefficient to filter the grid voltage when entering the fault ride-through state, thereby improving the signal response speed. After entering the fault ride-through state for a first preset time, the grid voltage fluctuation gradually decreases. At this time, the filter coefficient can be reduced further to balance the control response speed and stability.

[0056] The first preset duration can be a fixed value set in advance according to the experiment. For example, the first preset duration can be 60ms.

[0057] Optionally, the first preset duration can be dynamically adjusted according to the abnormal depth of the grid voltage, and the greater the abnormal depth of the grid voltage, the longer the first preset duration.

[0058] As can be seen from the above embodiments, this embodiment achieves dynamic adaptation of the filter coefficient to the fault stage by adjusting the dynamic filter coefficient in stages: within the first preset time of entering the fault ride-through state, a larger first filter coefficient is used to prioritize rapid response, suppress drastic voltage fluctuations, and avoid the risk of grid disconnection; after entering the first preset time of entering the fault ride-through state, the dynamic filter coefficient is reduced to significantly reduce noise introduction and improve signal stability while ensuring basic response capability. This staged strategy avoids the problems of insufficient initial response or excessive noise in the later stage in the prior art, allowing the dynamic filter coefficient to be gradually optimized as the fault develops. This not only ensures rapid ride-through capability in the early stage of the fault but also improves power quality in the later stage of the fault, further improving the full-cycle control logic of fault ride-through.

[0059] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0060] The following are device embodiments of the present invention. For details not described in detail, please refer to the corresponding method embodiments described above.

[0061] Figure 4 A schematic diagram of the control device for a grid-connected converter provided in an embodiment of the present invention is shown. For ease of explanation, only the parts related to the embodiment of the present invention are shown, and are described in detail below: like Figure 4 As shown, the control device 100 of the grid-connected converter includes: The power grid signal acquisition module 110 is used to monitor the power grid signal at the common coupling point between the power grid and the grid-connected converter in real time; the power grid signal includes the power grid voltage and / or the power grid frequency. The filter coefficient switching module 120 is used to enter a fault ride-through state if the power grid signal exceeds a first preset range, and to adjust the reference filter coefficient to a dynamic filter coefficient in the fault ride-through state; the dynamic filter coefficient is greater than the reference filter coefficient. The voltage feedforward module 130 is used to filter the grid voltage using the dynamic filtering coefficients to obtain a voltage feedback value; The voltage loop control module 140 is used to perform voltage loop control of the grid-connected converter based on the voltage feedback value, output voltage loop control quantity, and generate control signal for the grid-connected converter using the voltage loop control quantity.

[0062] In one possible implementation, the voltage feedforward module 130 includes: Multiplying the grid voltage by a first weighting factor yields the first grid voltage component; The first grid voltage component is filtered using the dynamic filtering coefficients to obtain the first voltage value; Subtracting the first grid voltage component from the grid voltage yields the second grid voltage component; The voltage feedback value is obtained by adding the first voltage value to the second grid voltage component.

[0063] In one possible implementation, the filter coefficient switching module 120 includes: Under the fault ride-through condition, the dynamic filtering coefficient is determined based on the grid short-circuit ratio; Switch the reference filter coefficients to the dynamic filter coefficients.

[0064] In one possible implementation, the grid short-circuit ratio is negatively correlated with the dynamic filtering coefficient.

[0065] In one possible implementation, the filter coefficient switching module 120 is specifically used for: The depth of the grid voltage anomaly is determined based on the degree to which the grid voltage deviates from the preset voltage range; The dynamic filtering coefficients are determined based on the grid short-circuit ratio and the anomaly depth of the grid voltage. The abnormal depth of the grid voltage is positively correlated with the dynamic filtering coefficient, and the grid short-circuit ratio is negatively correlated with the dynamic filtering coefficient.

[0066] In one possible implementation, the dynamic filtering coefficients include a first filtering coefficient and a second filtering coefficient; the voltage feedforward module 130 is specifically used for: During the first preset time period of entering the fault ride-through state, the first filtering coefficient is used to filter at least a portion of the grid voltage; After a first preset time period of entering the fault ride-through state, the first filter coefficient is multiplied by a preset adjustment parameter to obtain a second filter coefficient, and the second filter coefficient is used to filter at least a portion of the grid voltage; the preset adjustment parameter is less than 1.

[0067] In one possible implementation, the voltage loop control module 140 is specifically used for: Obtain the current loop output value of the grid-connected converter; The voltage loop control quantity is determined based on the difference between the current loop output value and the voltage feedback value.

[0068] Figure 5 This is a schematic diagram of the controller provided in an embodiment of the present invention. Figure 5As shown, the controller 5 in this embodiment includes a processor 50, a memory 51, and a computer program 52 stored in the memory 51 and executable on the processor 50. When the processor 50 executes the computer program 52, it implements the steps in the control method embodiments of the various grid-connected converters described above, for example... Figure 2 Steps S101 to S104 are shown. Alternatively, when the processor 50 executes the computer program 52, it implements the functions of each module / unit in the above-described device embodiments.

[0069] For example, the computer program 52 may be divided into one or more modules / units, which are stored in the memory 51 and executed by the processor 50 to complete the present invention. The one or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program 52 in the controller 5.

[0070] The controller 5 can be a computing device such as a desktop computer, laptop, handheld computer, or cloud server. The controller 5 may include, but is not limited to, a processor 50 and a memory 51. Those skilled in the art will understand that... Figure 5 This is merely an example of controller 5 and does not constitute a limitation on controller 5. It may include more or fewer components than shown, or combine certain components, or different components. For example, the controller may also include input / output devices, network access devices, buses, etc.

[0071] The processor 50 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0072] The memory 51 can be an internal storage unit of the controller 5, such as a hard disk or memory of the controller 5. The memory 51 can also be an external storage device of the controller 5, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the controller 5. Furthermore, the memory 51 can include both internal storage units and external storage devices of the controller 5. The memory 51 is used to store the computer program and other programs and data required by the controller. The memory 51 can also be used to temporarily store data that has been output or will be output.

[0073] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0074] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0075] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0076] In the embodiments provided by this invention, it should be understood that the disclosed devices / controllers and methods can be implemented in other ways. For example, the device / controller embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0077] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0078] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0079] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the control method embodiments for each of the above-described grid-connected converters. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0080] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A control method for a grid-connected converter, characterized in that, include: Real-time monitoring of the grid signal at the common coupling point between the power grid and the grid-connected converter; the grid signal includes grid voltage and / or grid frequency; If the power grid signal exceeds the first preset range, it enters the fault ride-through state, and in the fault ride-through state, the reference filter coefficient is adjusted to the dynamic filter coefficient. The dynamic filtering coefficient is greater than the baseline filtering coefficient; The grid voltage is filtered using the dynamic filtering coefficients to obtain a voltage feedback value; Based on the voltage feedback value, voltage loop control of the grid-connected converter is performed, and voltage loop control quantity is output. The control signal of the grid-connected converter is generated using the voltage loop control quantity.

2. The control method for a grid-connected converter according to claim 1, characterized in that, The step of filtering the grid voltage using the dynamic filtering coefficients to obtain a voltage feedback value includes: Multiplying the grid voltage by a first weighting factor yields the first grid voltage component; The first grid voltage component is filtered using the dynamic filtering coefficients to obtain the first voltage value; Subtracting the first grid voltage component from the grid voltage yields the second grid voltage component; The voltage feedback value is obtained by adding the first voltage value to the second grid voltage component.

3. The control method for a grid-connected converter according to claim 1, characterized in that, The step of adjusting the baseline filter coefficients to dynamic filter coefficients under the fault ride-through state includes: Under the fault ride-through condition, the dynamic filtering coefficient is determined based on the grid short-circuit ratio; Switch the reference filter coefficients to the dynamic filter coefficients.

4. The control method for a grid-connected converter according to claim 3, characterized in that, The grid short-circuit ratio is negatively correlated with the dynamic filtering coefficient.

5. The control method for a grid-connected converter according to claim 3, characterized in that, The determination of dynamic filtering coefficients based on the grid short-circuit ratio includes: The depth of the grid voltage anomaly is determined based on the degree to which the grid voltage deviates from the preset voltage range; The dynamic filtering coefficients are determined based on the grid short-circuit ratio and the anomaly depth of the grid voltage. The abnormal depth of the grid voltage is positively correlated with the dynamic filtering coefficient, and the grid short-circuit ratio is negatively correlated with the dynamic filtering coefficient.

6. The control method for a grid-connected converter according to claim 1, characterized in that, The dynamic filtering coefficients include a first filtering coefficient and a second filtering coefficient; the step of using the dynamic filtering coefficients to filter the grid voltage to obtain a voltage feedback value includes: During the first preset time period after entering the fault ride-through state, at least a portion of the grid voltage is filtered using the first filtering coefficient. After a first preset time period of entering the fault ride-through state, the first filter coefficient is multiplied by a preset adjustment parameter to obtain a second filter coefficient, and the second filter coefficient is used to filter at least a portion of the grid voltage; the preset adjustment parameter is less than 1.

7. The control method for a grid-connected converter according to claim 1, characterized in that, The voltage loop control of the grid-connected converter based on the voltage feedback value, outputting voltage loop control quantities, includes: Obtain the current loop output value of the grid-connected converter; The voltage loop control quantity is determined based on the difference between the current loop output value and the voltage feedback value.

8. A control device for a grid-connected converter, characterized in that, include: A power grid signal acquisition module is used to monitor the power grid signal at the common coupling point between the power grid and the grid-connected converter in real time; the power grid signal includes power grid voltage and / or power grid frequency. The filter coefficient switching module is used to enter the fault ride-through state if the power grid signal exceeds the first preset range, and to adjust the reference filter coefficient to the dynamic filter coefficient in the fault ride-through state. The dynamic filtering coefficient is greater than the baseline filtering coefficient; A voltage feedforward module is used to filter the grid voltage using the dynamic filtering coefficients to obtain a voltage feedback value; The voltage loop control module is used to perform voltage loop control of the grid-connected converter based on the voltage feedback value, output voltage loop control quantity, and use the voltage loop control quantity to generate the control signal of the grid-connected converter.

9. A controller comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the control method for the grid-connected converter as described in any one of claims 1 to 7.

10. A grid-connected converter, characterized in that, Includes the controller as described in claim 9.

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