A single-stage photovoltaic inverter maximum power tracking control method and related device

Abstract

The application belongs to the technical field of photovoltaic power generation, and particularly relates to a single-stage photovoltaic inverter maximum power tracking control method and related equipment. First, the output voltage and current of a photovoltaic array are sampled in real time, and the instantaneous output power is calculated. An improved perturbation and observation method is used to obtain the reference value of the direct current side voltage in the current period by combining the current output power with the historical reference value of the direct current side voltage in the last period. A network type matching control strategy is introduced, and a proportional coupling relationship between the direct current side voltage and the alternating current side frequency is constructed by relying on a matching coefficient. The voltage phase angle required for grid synchronization control is generated by combining the power data of the direct current side and the alternating current side. Finally, the single-stage photovoltaic inverter is implemented closed-loop control according to the voltage phase angle and the output voltage amplitude reference. The application can realize stable grid-connected inversion and accurate maximum power point tracking of the photovoltaic system at the same time, and effectively improve the power generation utilization rate of the photovoltaic array.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic power generation technology, and specifically relates to a maximum power point tracking control method and related equipment for a single-stage photovoltaic inverter. Background Technology

[0002] As a core form of clean energy, photovoltaic (PV) power generation is evolving from a supplementary energy source to a primary energy source. However, its intermittent and random power generation poses challenges to the stable operation of weak power grids and isolated microgrids. Grid-connected inverters have become a key development direction for improving the resilience and flexibility of power systems. Traditional grid-connected PV inverters rely on the stable voltage and frequency reference provided by the grid. When grid strength is insufficient or absent, they cannot autonomously establish voltage and frequency support, easily leading to system instability.

[0003] Currently, the mainstream commercial high-power photovoltaic grid-connected system adopts a two-stage inverter topology. This structure divides energy conversion into two stages. The front-stage DC-DC Boost converter enables the photovoltaic array to achieve maximum power point tracking and boosts the DC bus voltage. The rear-stage DC-AC inverter converts DC power into AC power synchronized with the grid and completes grid-connected control. The two stages are connected by a large-capacity DC bus capacitor, realizing the decoupling of MPPT control and grid-connected control. The technology is mature and the control strategy is relatively simple.

[0004] Two-stage topologies have significant drawbacks. First, energy requires two power conversions, resulting in switching and conduction losses. The high-frequency switching in the front-end, in particular, reduces overall system efficiency. Furthermore, the large number of components increases cost and size, reducing power density. Second, grid-based control relies on grid references, making it unable to autonomously construct grids in weak grids or islanded environments, resulting in poor grid adaptability. To overcome these issues, the industry has proposed single-stage topologies, eliminating the front-end DC-DC converter and combining boost and inverter functions. However, the direct coupling between the photovoltaic DC-side voltage and AC-side control variables makes it difficult to simultaneously achieve stable and fast MPPT and reliable grid-based control within a single power stage. This control challenge has become a bottleneck in its development. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a maximum power point tracking (MPPT) control method and related equipment for a single-stage photovoltaic inverter, which addresses the shortcomings of the prior art and solves the technical problem of the failure of traditional MPPT caused by the coupling between DC side voltage and AC side frequency in a single-stage grid-type photovoltaic inverter.

[0006] The objective of this invention is achieved through the following technical solutions: In a first aspect, the present invention provides a maximum power point tracking (MPPT) control method for a single-stage photovoltaic inverter, comprising: The output voltage and output current of the photovoltaic array are sampled, and the current output power is calculated. An improved disturbance observation method is used to obtain the DC-side voltage reference value for the current cycle based on the current output power and the historical reference voltage value, wherein the historical reference voltage value is the DC-side voltage reference value for the previous cycle. Based on the grid-type matching control strategy, the voltage phase angle required for grid-connected synchronous control is generated according to the DC-side voltage reference value and the power values ​​of the DC-side and AC-side. The grid-type matching control strategy establishes a proportional coupling relationship between the DC-side voltage and the AC-side frequency through the matching coefficient. Based on the voltage phase angle and output voltage amplitude reference, the single-stage photovoltaic inverter is subjected to closed-loop control to achieve grid-connected inverter and maximum power point tracking.

[0007] As a further improvement of the present invention, the formula for calculating the voltage phase angle required for the grid-connected synchronous control is as follows:

[0008] In the formula, The generated voltage phase angle; The preset reference angular frequency; The matching coefficient; The preset matching coefficient; This represents the power value on the DC side. This refers to the power value on the AC side; This is the DC side voltage; This is the reference value for the DC side voltage.

[0009] As a further improvement of the present invention, an improved perturbation observation method is adopted to obtain the DC-side voltage reference value for the current cycle based on the current output power and historical reference voltage values, including: Based on the current output power and the output power of the previous cycle, determine the direction of power change; Based on the direction of power change, determine the direction of voltage disturbance in the current cycle; The maximum power point reference voltage for the current cycle is calculated and updated based on the DC-side reference voltage value of the previous cycle, the voltage disturbance direction, and the preset disturbance step size. The maximum power point reference voltage of the current cycle is used as the DC-side voltage reference value for the current cycle.

[0010] As a further improvement of the present invention, determining the voltage disturbance direction of the current cycle based on the power change direction includes: If the current output power is greater than the output power of the previous cycle, the direction of power change is judged to be increasing, and thus the voltage disturbance direction of the current cycle remains unchanged. If the current output power is not greater than the output power of the previous cycle, the direction of power change is determined to be decreasing, and the voltage disturbance direction of the current cycle is reversed.

[0011] As a further improvement of the present invention, the preset disturbance step size is dynamically and adaptively adjusted according to the rate of change of the output power of the photovoltaic array.

[0012] As a further improvement of the present invention, the closed-loop control of the single-stage photovoltaic inverter, wherein the closed-loop control is a dual closed-loop control of voltage and current, includes: Voltage outer loop control: The difference between the output voltage amplitude reference and the output voltage of the photovoltaic array is used as input to generate the reference current of the current inner loop through the controller; Current inner loop control: Using the difference between the reference current and the output current of the photovoltaic array as input, combined with the voltage phase angle, a pulse width modulation signal is generated through a decoupling control algorithm, and the pulse width modulation signal is used to drive the power switching tubes of the single-stage photovoltaic inverter.

[0013] As a further improvement of the present invention, the controller for the voltage outer loop control is a proportional-integral controller; and the decoupling control algorithm for the current inner loop control is a feedforward decoupling control algorithm.

[0014] Secondly, the present invention provides a single-stage photovoltaic inverter system, comprising: Photovoltaic array; The DC bus capacitor is connected in parallel with the photovoltaic array; A single-stage three-phase full-bridge inverter, with its DC side connected to the DC bus capacitor; An LCL filter is connected between the AC side of the single-stage three-phase full-bridge inverter and the DC grid. The controller is configured to execute the single-stage photovoltaic inverter maximum power point tracking control method described above and output a pulse width modulation signal to the three-phase full-bridge inverter.

[0015] Thirdly, the present invention provides a computer device, comprising: a processor and a computer-readable storage medium; A processor, adapted to execute computer programs; A computer-readable storage medium storing a computer program, which, when executed by the processor, implements the single-stage photovoltaic inverter maximum power point tracking control method described above.

[0016] Fourthly, the present invention provides a computer-readable storage medium storing a computer program adapted to be loaded by a processor and executed as described above for the maximum power point tracking control method for a single-stage photovoltaic inverter.

[0017] The beneficial effects of this invention are as follows: This invention provides a maximum power point tracking (MPPT) control method for a single-stage photovoltaic (PV) inverter. By sampling and calculating the output voltage and current of the PV array, the current output power is obtained, enabling real-time acquisition of the actual output state of the PV array and providing accurate power basis for MPPT. An improved perturbation observation method is adopted, using the DC-side voltage reference value of the previous cycle as a historical reference voltage value to determine the DC-side voltage reference value of the current cycle. This allows the MPPT perturbation search to proceed based on the historical optimal operating point. Compared to the traditional perturbation observation method, which starts perturbation from a fixed initial point or a random point, the convergence path is shorter, and the oscillation amplitude around the maximum power point in steady state is significantly narrowed. Based on a grid-type matched control strategy, a DC-side matching coefficient is established. The proportional coupling relationship between voltage and AC frequency, combined with the power values ​​of DC and AC sides, generates the voltage phase angle required for grid-connected synchronization. The inverter operates with voltage source characteristics, and changes in DC voltage are directly mapped to AC frequency adjustment via a matching coefficient. Grid-connected synchronization can be achieved without relying on a phase-locked loop. Stable synchronous operation can still be maintained in weak grid scenarios with high grid impedance. Compared with the strong dependence on grid strength of existing grid-following control strategies, grid-connected adaptability is substantially improved. Closed-loop control of the single-stage photovoltaic inverter is performed based on the voltage phase angle and output voltage amplitude reference. Grid-connected inversion and maximum power point tracking are completed synchronously in a single-stage conversion topology, eliminating the additional losses and costs introduced by the front-stage DC-DC conversion stage in the existing two-stage scheme. In this invention, the DC-side voltage reference value output by the improved disturbance observation method is directly input into the grid-type matching control strategy. During MPPT adjustment, the change in DC-side voltage is naturally transmitted to the AC-side frequency through the matching coefficient. Maximum power point tracking and grid frequency support are coupled and completed in the same control link. The single-stage structure simultaneously takes into account MPPT accuracy, grid-connected synchronization robustness, and system efficiency. Compared with the problem that MPPT control and grid-connected control operate independently or even restrict each other in dynamic processes in the prior art, this solution eliminates the conflict between the two from the control architecture, realizing the unification of high-precision maximum power point tracking and stable grid-type grid connection of single-stage photovoltaic inverters in complex grid environments. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1This is a schematic diagram illustrating the principle of inverter synchronization control in the single-stage photovoltaic inverter maximum power point tracking control method in an embodiment of the present invention. Figure 2 This is a schematic diagram illustrating the overall working principle of a single-stage grid-type photovoltaic inverter in an embodiment of the present invention. Figure 3 This is a schematic diagram illustrating the failure of maximum power point tracking due to voltage deviation when using the conventional perturbation observation method in an embodiment of the present invention. Figure 4 This is a schematic diagram of the system response when the MPPT control step size is increased to exceed the steady-state deviation of the DC voltage in an embodiment of the present invention; Figure 5 This is a schematic diagram of the traditional perturbation observation method; Figure 6 This is a schematic diagram of the improved perturbation observation method proposed in this invention in an embodiment of the invention; Figure 7 This is a response waveform diagram of a photovoltaic inverter using this control strategy in an embodiment of the present invention when the light intensity decreases. Figure 8 This is a response waveform diagram of a photovoltaic inverter using the control strategy in an embodiment of the present invention when the light intensity increases. Figure 9 This is an internal structural diagram of a computer device in an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives and technical solutions of this invention clearer and easier to understand, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0021] Traditional photovoltaic inverters mostly employ grid-following control strategies, heavily relying on the stable voltage and frequency reference provided by the power grid, essentially functioning as controlled current sources. When the grid strength is insufficient or completely absent, these inverters cannot autonomously establish voltage and frequency support, potentially leading to system instability.

[0022] Currently, high-power photovoltaic grid-connected systems generally adopt a two-stage inverter topology. The front stage is a DC-DC Boost converter to achieve maximum power point tracking and DC voltage boosting, while the rear stage is a DC-AC inverter for grid-connected control. The two stages are connected by a large-capacity DC bus capacitor, allowing the front-stage MPPT control and the rear-stage grid-connected control to be designed relatively independently. However, this structure has inherent defects: First, energy needs to undergo two complete power conversions, with each stage generating switching and conduction losses. In particular, the front-stage Boost converter operates in a high-frequency switching state, directly reducing the overall system conversion efficiency. At the same time, the required number of power switching devices, magnetic components, DC support capacitors, and other components increases the system's material costs, manufacturing costs, equipment size and weight, and reduces power density. Second, traditional two-stage photovoltaic inverters use a grid-following control strategy based on phase-locked loops. Under weak grid conditions formed by high proportion of renewable energy access or in islanded operation mode, due to the lack of a stable grid reference, they cannot autonomously establish and maintain AC voltage and frequency, and cannot provide the necessary voltage and frequency support for the grid or local loads.

[0023] To overcome the efficiency and cost shortcomings of two-stage structures, existing technologies propose single-stage photovoltaic inverter topologies, eliminating the need for a front-stage DC-DC converter and combining boost and inversion functions into a single stage. However, in a single-stage structure, the DC-side voltage of the photovoltaic array is directly coupled to the control variables on the AC side of the inverter, making it extremely challenging to simultaneously achieve stable and rapid maximum power point tracking and reliable grid-based control within a single power stage. The key technical bottleneck of existing single-stage photovoltaic inverter control lies in how to design an effective control strategy to coordinate the dynamic relationship between DC-side voltage regulation and AC-side voltage frequency construction, preventing system instability and ensuring optimal performance for both.

[0024] like Figure 5 As shown, the traditional disturbance-observation method is a commonly used MPPT control strategy, such as... Figure 3 As shown, within each control cycle, the voltage reference value for the next cycle is calculated and updated based on the actual output voltage value of the photovoltaic array sampled at the current moment. Under the grid-matched control strategy, since the grid-side frequency and DC-side voltage are coupled through a matching coefficient, a steady-state deviation will occur between the actual DC-side voltage and the DC-side reference voltage when the grid-side frequency changes. When the control step size of the traditional disturbance-observation method is smaller than this steady-state deviation, the adjustment logic of MPPT control will be overwhelmed by the voltage deviation, failing to drive the system to move towards the correct maximum power point, resulting in MPPT failure. Figure 4 As shown, when the control step size is increased to exceed the steady-state deviation, although the MPPT function can recover, each voltage disturbance will cause significant fluctuations in the AC side output frequency through control coupling, injecting harmonic interference into the grid, affecting power quality, and weakening the frequency support capability that the inverter should provide as a grid unit, thus adversely affecting the frequency stability of the power system.

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. The described embodiments are only some embodiments of the present invention, and not all embodiments.

[0026] Example 1 This embodiment provides a maximum power point tracking (MPPT) control method for a single-stage photovoltaic inverter, such as... Figure 1 , Figure 2 As shown, the synchronous control strategy employs a matched control method combined with an improved disturbance observation method. This achieves grid-based control of the inverter while simultaneously enabling maximum power point tracking (MPPT) of the photovoltaic cells. The following is a detailed implementation of the MPPT control method for a single-stage photovoltaic inverter.

[0027] S1. Sample the output voltage and output current of the photovoltaic array and calculate the current output power.

[0028] A voltage sensor is connected in parallel and a current sensor is connected in series at the output of the photovoltaic array to sample the output voltage and current of the photovoltaic array in real time at a preset sampling frequency. The sampling frequency is selected according to the control cycle of the system.

[0029] Based on the sampled output voltage and current values, the current output power of the photovoltaic array is calculated. The output power is calculated as the product of the current output voltage and current values. This calculated output power value is stored for subsequent power change direction determination and MPPT control.

[0030] By setting the sampling frequency appropriately and using high-precision sensors and analog-to-digital converters, sampling errors can be effectively reduced, ensuring the effectiveness and stability of the control strategy.

[0031] S2. Using the improved disturbance observation method, the DC side voltage reference value for the current cycle is obtained based on the current output power and historical reference voltage value.

[0032] The historical reference voltage value is the DC-side voltage reference value of the previous cycle. The improved disturbance observation method used in this invention, such as... Figure 6 As shown, the core idea is to construct the voltage reference value generation process as an iterative update sequence. The DC-side voltage reference value of the current cycle is directly based on the DC-side voltage reference value of the previous cycle, and updated in combination with the power change direction and a preset disturbance step size, rather than relying on the actual voltage sample value at the current moment. This approach can effectively isolate the direct impact of potential steady-state error or fluctuations in the actual DC-side voltage on the MPPT decision logic in the control structure, thereby improving the robustness and accuracy of MPPT control.

[0033] Specifically, the implementation process of the improved disturbance observation method includes the following steps: First, obtain the output power value stored in the previous cycle and compare it with the currently calculated output power value to determine the direction of power change. If the current output power is greater than the output power of the previous cycle, the power change direction is determined to be increasing, and the voltage disturbance direction of the current cycle remains unchanged. If the current output power is not greater than the output power of the previous cycle, the power change direction is determined to be decreasing, and the voltage disturbance direction of the current cycle is reversed. Then, based on the stored DC-side reference voltage value of the previous cycle, and according to the determined voltage disturbance direction and the preset disturbance step size, calculate the maximum power point reference voltage of the current cycle. The calculation method is to add the DC-side reference voltage value of the previous cycle to the product of the voltage disturbance direction and the disturbance step size. The voltage disturbance direction is represented by a symbol, with positive for positive disturbances and negative for negative disturbances. The calculated maximum power point reference voltage of the current cycle is used as the DC-side voltage reference value of the current cycle and input to the subsequent network matching control loop. The output power value and DC-side voltage reference value of the current cycle are stored for control calculation in the next cycle.

[0034] Furthermore, the preset perturbation step size can be dynamically and adaptively adjusted according to the rate of change of the photovoltaic array's output power. When the rate of change of the photovoltaic array's output power exceeds a preset first threshold, for example, ... Figure 7 , Figure 8 As shown, in cases of a sudden change in light intensity, a larger perturbation step size is used to accelerate the tracking speed of the maximum power point and reduce the dynamic adjustment time. When the rate of change of the photovoltaic array output power is less than a preset second threshold, such as in cases of stable light intensity, a smaller perturbation step size is used to reduce power oscillations near the maximum power point and improve tracking accuracy. The first threshold is greater than the second threshold. The adaptive step size adjustment balances the speed and accuracy of MPPT control, ensuring the system maintains good MPPT performance under different operating conditions.

[0035] S3. Based on the grid-type matching control strategy, the voltage phase angle required for grid-connected synchronous control is generated according to the DC side voltage reference value and the power values ​​of the DC side and AC side.

[0036] The grid-connected matching control strategy establishes a proportional coupling relationship between the DC-side voltage and the AC-side frequency through a matching coefficient, enabling the inverter to autonomously establish and stabilize the AC voltage and frequency, thus possessing grid-connected capability. Under this control strategy, the inverter no longer relies on the voltage and frequency reference provided by the grid, and can provide the necessary voltage and frequency support for the system under weak grid or islanded operation conditions.

[0037] Specifically, such as Figure 1 As shown, the voltage phase angle required for grid-connected synchronous control is calculated using the following formula:

[0038] In the formula, The generated voltage phase angle; The preset reference angular frequency; The matching coefficient; The preset matching coefficient; This represents the power value on the DC side. This refers to the power value on the AC side; This is the DC side voltage; This is the reference value for the DC side voltage.

[0039] As can be seen from the above formula, when the DC-side power is unbalanced with the AC-side power, or when there is a deviation between the actual DC-side voltage and the DC-side reference voltage, the system will adjust the output angular frequency to maintain power balance and voltage stability. This control method enables the inverter to exhibit a stable and rapid response to changes in the external grid frequency, enhances the grid voltage strength, and has good DC-side voltage support capability, allowing it to adapt to constant power input.

[0040] S4. Based on the voltage phase angle and output voltage amplitude reference, a closed-loop control is performed on the single-stage photovoltaic inverter to achieve grid-connected inverter and maximum power point tracking.

[0041] Based on the generated voltage phase angle and the preset output voltage amplitude reference, a dual-loop voltage and current control is implemented for the single-stage photovoltaic inverter to achieve coordinated control of grid-connected inverter and maximum power point tracking. This dual-loop control simultaneously ensures the stability of the output voltage and the rapid response of the output current, improving the system's dynamic and steady-state performance.

[0042] Specifically, the voltage and current dual closed-loop control includes an outer voltage loop control and an inner current loop control. The outer voltage loop control uses the difference between a preset output voltage amplitude reference and the amplitude of the inverter's AC output voltage as input, and adjusts it through a proportional-integral controller to generate the reference current for the inner current loop. The main function of the outer voltage loop is to maintain the stability of the inverter's output voltage amplitude, ensuring the quality of the output power. The proportional and integral coefficients of the proportional-integral controller are tuned according to the system's voltage regulation accuracy and dynamic response requirements.

[0043] The inner current loop control uses the difference between the reference current generated by the outer voltage loop and the inverter's AC output current as input. Combined with the generated voltage phase angle, it is adjusted through a feedforward decoupling control algorithm to generate a pulse-width modulation (PWM) signal. This algorithm eliminates the coupling effect between the d-axis and q-axis currents, achieving fast, decoupled current control. The generated PWM signal drives the power switches of the single-stage photovoltaic inverter, controlling their on / off states to convert DC power to AC power and deliver the AC power to the grid or local load.

[0044] Throughout the control process, the DC-side voltage reference value generated by the improved disturbance observation method is transformed into frequency and phase control signals on the AC side through a grid-matched control strategy. Simultaneously, dual closed-loop voltage and current control ensures stable output voltage amplitude. This achieves the organic integration of maximum power point tracking control and grid-matched control in a single-stage photovoltaic inverter, resolving the coupling contradiction between the two.

[0045] Example 2 This invention also provides a single-stage photovoltaic inverter system, comprising a photovoltaic array, a DC bus capacitor, a single-stage three-phase full-bridge inverter, an LCL filter, and a controller. The photovoltaic array converts solar energy into DC power, and its output is connected in parallel with the DC bus capacitor. The DC bus capacitor smooths the DC-side voltage and suppresses voltage fluctuations; its capacitance value is selected based on the system's power rating and voltage ripple requirements. The DC side of the single-stage three-phase full-bridge inverter is connected to the DC bus capacitor and converts DC power into AC power; its power switching transistors are insulated-gate bipolar transistors (IGBTs). The LCL filter is connected between the AC side of the single-stage three-phase full-bridge inverter and the power grid to filter out high-order harmonics at the inverter output, ensuring the quality of the output power; its inductance and capacitance parameters are designed according to the system's harmonic suppression requirements and switching frequency. The controller is electrically connected to the voltage and current sensors of the photovoltaic array, the power switching transistors of the single-stage three-phase full-bridge inverter, and the voltage and current sensors of the LCL filter. The controller is configured to execute the single-stage photovoltaic inverter maximum power point tracking control method described above, generate a pulse width modulation signal based on the sampled voltage and current signals, and output it to the power switching transistor of the single-stage three-phase full-bridge inverter to drive the power switching transistor to work.

[0046] Specific limitations on the controller in a single-stage photovoltaic inverter system can be found in the limitations of the maximum power point tracking (MPPT) control method for single-stage photovoltaic inverters described above; the corresponding technical effects are equivalent and will not be repeated here. Each module in the aforementioned controller can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the corresponding operations of each module.

[0047] Example 3 Figure 9 An internal structural diagram of a computer device is shown in one embodiment. This computer device may specifically be a terminal or a server. Figure 9 As shown, the computer device includes a processor, memory, network interface, display, camera, and input device connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The network interface is used to communicate with external terminals via a network connection. When the computer program is executed by the processor, it implements a maximum power point tracking (MPPT) control method for a single-stage photovoltaic inverter. The display screen can be an LCD screen or an e-ink display. The input device can be a touch layer covering the display screen, buttons, a trackball, or a touchpad mounted on the computer device casing, or an external keyboard, touchpad, or mouse.

[0048] As will be understood by those skilled in the art, computer equipment Figure 9 The structure shown is merely a block diagram of a portion of the structure related to the present invention and does not constitute a limitation on the computer device to which the present invention is applied. A specific computing device may include more or fewer components than those shown in the figure, or combine certain components, or have the same component arrangement.

[0049] In one embodiment, a computer device is provided, 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 method described above.

[0050] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0051] In summary, the single-stage photovoltaic inverter maximum power point tracking control method provided in this application adopts a single-stage power conversion topology, which eliminates the front-stage DC-DC converter in the traditional two-stage structure, reduces the number of power conversion stages, reduces switching losses and conduction losses, and improves the overall conversion efficiency of the system. At the same time, it reduces the number of power switching devices, magnetic components and other components, reduces the material cost and manufacturing cost of the system, reduces the size and weight of the equipment, and increases the power density.

[0052] By combining a grid-based matching control strategy with an improved disturbance observation method, maximum power point tracking control and grid-based control are organically integrated within a single-stage framework. The grid-based matching control strategy establishes a proportional coupling relationship between the DC-side voltage and the AC-side frequency through a matching coefficient, enabling the inverter to autonomously build a grid. This allows it to provide voltage and frequency support to the system under weak grid or islanded operation conditions, enhancing the system's grid adaptability.

[0053] An improvement on the traditional perturbation observation method was made by constructing the voltage reference value generation process as an iterative update sequence based on the reference voltage of the previous cycle, rather than relying on the actual voltage sampling value at the current moment. This effectively isolates the interference of DC side voltage steady-state error or fluctuation on MPPT decision logic, solves the problem that the traditional MPPT method is prone to failure under network control, and avoids AC side frequency fluctuation caused by increasing the step size, thus ensuring power quality and system frequency stability.

[0054] By adopting a dual closed-loop control structure for voltage and current, combined with a feedforward decoupling control algorithm, fast and stable control of output voltage and output current is achieved, improving the dynamic and steady-state performance of the system.

[0055] The various embodiments in this specification are described in a progressive manner. For directly identical or similar parts of the embodiments, refer to each other. Each embodiment focuses on its differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. It should be noted that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification.

[0056] The above-described embodiments are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and substitutions without departing from the principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention. Therefore, the scope of protection of this invention should be determined by the scope of the claims.

Claims

1. A maximum power point tracking control method for a single-stage photovoltaic inverter, characterized in that, include: The output voltage and output current of the photovoltaic array are sampled, and the current output power is calculated. An improved disturbance observation method is used to obtain the DC-side voltage reference value for the current cycle based on the current output power and the historical reference voltage value, wherein the historical reference voltage value is the DC-side voltage reference value for the previous cycle. Based on the grid-connected matching control strategy, the voltage phase angle required for grid-connected synchronous control is generated according to the DC side voltage reference value and the power values ​​of the DC side and AC side. The network-type matching control strategy establishes a proportional coupling relationship between the DC-side voltage and the AC-side frequency through the matching coefficient; Based on the voltage phase angle and output voltage amplitude reference, the single-stage photovoltaic inverter is subjected to closed-loop control to achieve grid-connected inverter and maximum power point tracking.

2. The maximum power point tracking control method for a single-stage photovoltaic inverter according to claim 1, characterized in that, The formula for calculating the voltage phase angle required for the grid-connected synchronous control is as follows: In the formula, The generated voltage phase angle; The preset reference angular frequency; The matching coefficient; The preset matching coefficient; This represents the power value on the DC side. This refers to the power value on the AC side; This is the DC side voltage; This is the reference value for the DC side voltage.

3. The maximum power point tracking control method for a single-stage photovoltaic inverter according to claim 1, characterized in that, Using an improved disturbance observation method, the DC-side voltage reference value for the current cycle is obtained based on the current output power and historical reference voltage values, including: Based on the current output power and the output power of the previous cycle, determine the direction of power change; Based on the direction of power change, determine the direction of voltage disturbance in the current cycle; The maximum power point reference voltage for the current cycle is calculated and updated based on the DC-side reference voltage value of the previous cycle, the voltage disturbance direction, and the preset disturbance step size. The maximum power point reference voltage of the current cycle is used as the DC-side voltage reference value for the current cycle.

4. The maximum power point tracking control method for a single-stage photovoltaic inverter according to claim 3, characterized in that, Based on the power change direction, the voltage disturbance direction for the current cycle is determined, including: If the current output power is greater than the output power of the previous cycle, the direction of power change is judged to be increasing, and thus the voltage disturbance direction of the current cycle remains unchanged. If the current output power is not greater than the output power of the previous cycle, the direction of power change is determined to be decreasing, and the voltage disturbance direction of the current cycle is reversed.

5. The maximum power point tracking control method for a single-stage photovoltaic inverter according to claim 3, characterized in that, The preset perturbation step size is dynamically and adaptively adjusted according to the rate of change of the output power of the photovoltaic array.

6. The maximum power point tracking control method for a single-stage photovoltaic inverter according to claim 1, characterized in that, The closed-loop control of the single-stage photovoltaic inverter, wherein the closed-loop control is a dual closed-loop control of voltage and current, includes: Voltage outer loop control: The difference between the output voltage amplitude reference and the output voltage of the photovoltaic array is used as input to generate the reference current of the current inner loop through the controller; Current inner loop control: Using the difference between the reference current and the output current of the photovoltaic array as input, combined with the voltage phase angle, a pulse width modulation signal is generated through a decoupling control algorithm, and the pulse width modulation signal is used to drive the power switching tubes of the single-stage photovoltaic inverter.

7. The maximum power point tracking control method for a single-stage photovoltaic inverter according to claim 6, characterized in that, The voltage outer loop control uses a proportional-integral controller; the current inner loop control uses a feedforward decoupling control algorithm.

8. A single-stage photovoltaic inverter system, characterized in that, include: Photovoltaic array; The DC bus capacitor is connected in parallel with the photovoltaic array; A single-stage three-phase full-bridge inverter, with its DC side connected to the DC bus capacitor; An LCL filter is connected between the AC side of the single-stage three-phase full-bridge inverter and the DC grid. The controller is configured to perform the single-stage photovoltaic inverter maximum power point tracking control method as described in any one of claims 1 to 7, and to output a pulse width modulation signal to the three-phase full-bridge inverter.

9. A computer device, characterized in that, include: Processor and computer-readable storage media; A processor, adapted to execute computer programs; A computer-readable storage medium storing a computer program, which, when executed by the processor, implements the single-stage photovoltaic inverter maximum power point tracking control method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program adapted to be loaded by a processor and executed as described in any one of claims 1 to 7 for maximum power point tracking control of a single-stage photovoltaic inverter.

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