Harmonic suppression method for network construction type optical storage converter

Abstract

The invention discloses a harmonic suppression method for a network construction type optical storage converter, and belongs to the technical field of new energy. According to the method, the operation of the photovoltaic inverter is adjusted through a constant voltage control strategy, remarkable advantages are shown, the energy loss is effectively reduced by inhibiting the photovoltaic inter-harmonics, and the operation stability of the system is improved. The photovoltaic power fluctuation can be obviously reduced, the energy storage control cost is effectively reduced, and the service life of energy storage equipment is prolonged. Meanwhile, the grid-connected performance is excellent, the distortion rate of grid-connected voltage and current can be reduced, and the electric energy grid-connected quality is improved. In addition, a network construction control method is introduced into the system, the network voltage can be effectively supported, the network frequency can be flexibly adjusted, and the adaptability and supporting capacity of the system to network operation are enhanced. According to the invention, stable operation requirements in different grid-connected environments can be met. The method has important technical innovation in the aspects of improving the operation efficiency, the reliability and the system coordination, and has extremely high application and popularization values.

Description

Technical Field

[0001] The present invention relates to the field of new energy technology, and in particular to a method for suppressing harmonics of a grid-type photovoltaic storage converter. Background Art

[0002] New energy generation is gradually replacing traditional fossil energy, and photovoltaic power generation has become an important form of new energy due to its clean and renewable advantages. However, the intermittent and volatile nature of photovoltaic power generation, especially in a high-penetration grid-connected environment, poses a huge challenge to the stability of the power system.

[0003] In order to deal with the low inertia and other problems caused by photovoltaic access and provide the necessary frequency support for the power grid, grid control has been widely used due to its unique advantages. However, since the photovoltaic system is significantly affected by environmental changes, its output power has a high uncertainty, and it is often necessary to suppress power fluctuations through the energy storage system and provide additional energy support to the grid control. Traditional photovoltaic systems generally use maximum power point tracking (MPPT) technology to improve the efficiency of photovoltaic power generation, but this technology will cause large power fluctuations during dynamic tracking, resulting in unstable DC bus voltage, which in turn affects the performance of the energy storage system. In addition, interharmonics (voltage components that are not integer multiples of the fundamental wave) will be generated during the operation of the photovoltaic system. These interharmonics will not only increase system losses, but may also cause grid flicker, nuisance triggering protection system triggering grid protection mechanism, and affect the stability of the power system. Therefore, relying solely on MPPT technology cannot effectively improve the stability and power quality problems that occur during the photovoltaic storage grid connection process.

[0004] At present, the control strategies of photovoltaic storage systems mainly include MPPT control on the photovoltaic side, voltage and current dual closed-loop control on the energy storage side, and inverter network control. However, these control methods usually operate independently and lack global coordination. Photovoltaic power fluctuations directly affect the charging and discharging strategies of the energy storage system, and the regulation capability of the energy storage system determines the suppression effect of photovoltaic power fluctuations to a certain extent. Therefore, coordinated control between photovoltaic and energy storage systems is crucial for stabilizing system performance. Although many studies have proposed photovoltaic power fluctuation control and energy storage system control methods, the existing control methods still have many shortcomings in harmonic suppression, power fluctuation control, and system coordination. In particular, the suppression of intermediate harmonics in photovoltaic storage systems has not been effectively solved, resulting in the system power quality being difficult to meet the grid connection requirements. At the same time, the DC bus voltage fluctuations caused by photovoltaic power fluctuations not only affect the operating efficiency of the energy storage system, but also aggravate the distortion of grid voltage and current, further increase the total harmonic distortion, and affect the operation of the grid.

[0005] Therefore, there is an urgent need for an efficient harmonic suppression method for photovoltaic-storage converters that can effectively reduce the impact of interharmonics in the photovoltaic-storage system, smooth photovoltaic power fluctuations, and achieve coordinated control between the photovoltaic system and the energy storage system, thereby improving the overall stability and power quality of the photovoltaic-storage system and meeting the needs of large-scale access of renewable energy power generation to the power grid. Summary of the invention

[0006] The purpose of the present invention is to provide a harmonic suppression method for a grid-type photovoltaic storage converter, which can suppress photovoltaic interharmonics, reduce system losses, and improve system stability. At the same time, in view of the photovoltaic power fluctuation problem existing in the traditional control strategy, it can smooth out its fluctuation and alleviate the fluctuation of the DC bus voltage caused by it, reduce the energy storage control cost and extend the service life of the energy storage equipment. In addition, it can effectively support the grid voltage and flexibly adjust the grid frequency, thereby enhancing the system's adaptability and support capabilities for grid operation.

[0007] To achieve the above object, the present invention provides a method for suppressing harmonics of a grid-type photovoltaic storage converter, comprising the following steps: S1. Obtain the DC bus voltage value, photovoltaic output voltage and current, energy storage battery voltage and current, LC filter inductor current, and grid connection point voltage and current in the current photovoltaic storage system; S2, tracking photovoltaic output power through constant voltage control, which can effectively suppress photovoltaic power fluctuations compared with traditional disturbance observation method control; S3. Use voltage and current dual closed-loop control to adjust the output of the energy storage system to ensure a constant DC bus voltage.

[0008] S4. Based on step S2 and step S3, combined with inverter network control, the overall coordinated control of the photovoltaic storage system is completed.

[0009] Preferably, in step S2, the photovoltaic output power is tracked based on constant voltage control to suppress photovoltaic power fluctuations, and the control process specifically includes the following steps: S21, obtain the voltage difference feedback signal and collect the output voltage of the photovoltaic system and the set photovoltaic voltage reference value Compare and get the voltage error signal , as shown in formula (1): (1); S22, perform PI regulation, input the voltage error signal into the proportional-integral controller, and output the duty cycle signal through PI regulation, as shown in formula (2): (2); in and Respectively represent the proportional and integral values ​​in the photovoltaic proportional-integral controller.

[0010] S23, generate PWM signal, input the duty cycle signal output by PI controller (proportional integral controller) into pulse width modulation PWM module (modulation module), and generate PWM control signal , using constant voltage control to track photovoltaic output power, compared with the traditional disturbance observation method control, it can suppress photovoltaic interharmonics, reduce system losses, and improve system stability. Reduce the DC bus voltage fluctuation caused by photovoltaic power fluctuations.

[0011] Preferably, in step S23, the conventional disturbance observation method is used for control, and the control process specifically includes the following steps: S231, obtain photovoltaic cell parameters and collect the voltage at the photovoltaic cell end and current Signal, input maximum power point tracking control; S232: Execute maximum power point tracking control, calculate and output voltage reference value according to the collected photovoltaic voltage and current , so that the photovoltaic cell works at the maximum power point; S233, generate a voltage error signal and convert the voltage reference value The actual photovoltaic output voltage Perform comparison to generate a voltage error signal; S234, executing PI regulation, inputting the voltage error signal into a proportional-integral PI controller, performing PI regulation, and outputting a duty cycle signal for adjusting the photovoltaic converter; S235: Inputting the duty cycle signal of the photovoltaic converter into the pulse width modulation (PWM) module to generate a PWM switch signal .

[0012] Preferably, in step S232, the maximum power point tracking control (MPPT) specifically includes the following steps: S2321, calculating the increments of power and voltage, and calculating the relationship between the power increment and the voltage increment based on the current photovoltaic output power and voltage values; S2322. Determine the sign of the increment and adjust the working voltage. If the power increment is greater than 0, it means that the current working point is on the left side of the maximum power point. At this time, increase the working voltage of the photovoltaic cell. If the power increment is less than 0, it means that the current working point is on the right side of the maximum power point. At this time, reduce the working voltage of the photovoltaic cell. If the power increment is equal to 0, it indicates that the system has reached the maximum power point and maintain the current working voltage of the photovoltaic cell unchanged.

[0013] S2323, execute voltage adjustment according to the judgment result of the increment sign, and control the working voltage of the photovoltaic cell until the system stabilizes at the maximum power point.

[0014] S2324. Repeat the above steps to continuously collect the output parameters of the photovoltaic cells, and cyclically perform the disturbance observation operation of power and voltage to ensure that the photovoltaic system operates at the maximum power point in real time.

[0015] Preferably, in step S3, the control process specifically includes the following steps: S31, obtain the DC bus voltage feedback signal and collect the current DC bus voltage value and the set DC bus voltage reference value Compare and obtain the voltage error signal , as shown in formula (3): (3); S32, perform voltage loop PI regulation, input the voltage error signal into the proportional-integral (PI) controller, perform voltage loop PI regulation, and output current reference instruction , as shown in formula (4): (4); in , Represent the voltage loop proportional and integral gains respectively.

[0016] S33, execute current loop PI adjustment, and compare the current reference command with the actual feedback current value Compare and get the current error signal. Input the current error signal into the proportional-integral (PI) controller to adjust the current loop PI and output the duty cycle signal, as shown in formula (5): (5); in , Represent the current loop proportional and integral gains respectively.

[0017] S34, generating a PWM signal, inputting the duty cycle signal into a pulse width modulation (PWM) generation module, and generating a PWM switch signal for driving the energy storage converter .

[0018] Preferably, in step S4, the control method adopted by photovoltaic, energy storage and inverter, combined with inverter grid control, specifically includes the following steps: S41. The photovoltaic system adopts constant voltage control.

[0019] S42. The energy storage system adopts constant DC bus voltage control and adjusts the DC bus voltage through voltage and current dual closed-loop control.

[0020] S43, the inverter uses virtual synchronous generator control technology (VSG) for network control. The control principle is shown in equation (6) and equation (7): (6); (7); Among them, the active power reference value and reactive power reference Assigned by superior dispatcher. and ω Represent the rated angular frequency and actual angular frequency of the power grid respectively, J and D p Respectively represent the system's moment of inertia and damping coefficient. In the reactive loop, and V o Respectively represent the rated phase voltage amplitude and the actual output phase voltage amplitude of the power grid, K and D q are the proportional coefficient and reactive droop coefficient respectively. The virtual synchronous generator control is adopted as the network control strategy. By simulating the main body model, active frequency regulation and reactive voltage regulation characteristics of the synchronous generator, the inertia and damping performance of the system are effectively improved. When the power grid fails or is disturbed, it can provide inertia support power to ensure the stability of the power grid frequency.

[0021] Therefore, the present invention adopts a harmonic suppression method of a grid-type photovoltaic storage converter with the above structure, which has the following beneficial effects: (1) The present invention suppresses photovoltaic interharmonics, reduces system losses, and improves system stability through a constant voltage control strategy.

[0022] (2) The present invention reduces photovoltaic power fluctuations and significantly reduces the DC bus voltage fluctuations caused by photovoltaic power fluctuations, can suppress grid-connected harmonics, and reduce the harmonic distortion rate of grid-connected voltage and current, thereby improving the quality of power grid connection.

[0023] (3) The present invention improves the DC bus voltage stability, reduces the DC bus voltage fluctuation under the traditional control strategy, and effectively reduces the control error and operation risk caused by voltage fluctuation.

[0024] (4) The present invention reduces the energy loss of the energy storage system caused by frequent adjustment of photovoltaic power fluctuations, reduces the operating cost of the energy storage system, and extends its service life.

[0025] (5) The present invention introduces a photovoltaic-storage network control method, which significantly improves the system's ability to support grid voltage and regulate frequency, and improves the grid adaptability of the photovoltaic-storage system.

[0026] (6) The present invention can effectively improve the reliability of the photovoltaic storage system, reduce the risk of operational failures, and achieve efficient power management to meet the needs of various grid-connected operation scenarios.

[0027] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a topological diagram of a typical photovoltaic energy storage system with a DC bus according to the present invention; Figure 2 This is a control block diagram of a constant voltage controlled photovoltaic system for harmonic suppression of a grid-type photovoltaic storage inverter according to the present invention; Figure 3 This is a control block diagram of a photovoltaic system based on maximum power point tracking according to the present invention; Figure 4 This is a voltage and current dual-loop control block diagram of the energy storage system of the present invention; Figure 5 It is a schematic diagram of the harmonic suppression method of the grid-type photovoltaic storage converter; Figure 6 Schematic diagram of photovoltaic voltage before and after improvement; (a) is the schematic diagram of photovoltaic voltage before improvement, (b) is the schematic diagram of photovoltaic voltage after improvement; Figure 7 Schematic diagram of DC bus voltage before and after improvement of the present invention; (a) is a schematic diagram of DC bus voltage before improvement; (b) is a schematic diagram of DC bus voltage after improvement; Figure 8 Before and after the improvement of the present invention a Schematic diagram of phase-connected grid current and total harmonic distortion; (a) is before improvement a Fast Fourier transform analysis (FFT) of phase-connected grid current; (b) is the improved a Fast Fourier transform analysis (FFT) of phase-connected grid current; Fig. 9 The present invention is a schematic flow chart of the steps of a method for suppressing harmonics in a grid-type photovoltaic storage inverter. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0030] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0031] Example like Figure 1-Figure 9 As shown, the present invention provides a method for suppressing harmonics of a grid-type photovoltaic storage converter, comprising the following steps: S1. Obtain the DC bus voltage value, photovoltaic output voltage and current, energy storage battery voltage and current, LC filter inductor current, and grid connection point voltage and current in the current photovoltaic storage system; S2, tracking photovoltaic output power through constant voltage control, which can effectively suppress photovoltaic power fluctuations compared with traditional disturbance observation method control; S3. Use voltage and current dual closed-loop control to adjust the output of the energy storage system to ensure a constant DC bus voltage.

[0032] S4. Based on step S2 and step S3, combined with inverter network control, the overall coordinated control of the photovoltaic storage system is completed.

[0033] In step S2, the photovoltaic output power is tracked based on constant voltage control to suppress photovoltaic power fluctuations, as shown in the attached Figure 2 As shown. and Respectively represent the photovoltaic reference voltage and photovoltaic voltage. PI represents the proportional integral controller, and PWM is the modulation module. The control process specifically includes the following steps: S21, obtain the voltage difference feedback signal and collect the output voltage of the photovoltaic system and the set photovoltaic voltage reference value Compare and get the voltage error signal , as shown in formula (1): (1); S22, perform PI regulation, input the voltage error signal into the proportional-integral controller, and output the duty cycle signal through PI regulation, as shown in formula (2): (2); in and Respectively represent the proportional and integral values ​​in the photovoltaic proportional-integral controller.

[0034] S23, generate PWM signal, input the duty cycle signal output by PI controller into pulse width modulation PWM module, generate PWM control signal , using constant voltage control to track the maximum output power of photovoltaics, suppress photovoltaic interharmonics, reduce system losses, and improve system stability. In addition, this control method reduces photovoltaic power fluctuations and the DC bus voltage fluctuations caused by them, can suppress grid-connected harmonics, reduce the harmonic distortion rate of grid-connected voltage and current, and thus improve the quality of power grid connection.

[0035] In step S23, the conventional disturbance observation method is used for control, as shown in the attached Figure 3 As shown. and Represent the voltage and current of the PV panel respectively. It is the photovoltaic reference voltage generated by the photovoltaic maximum power tracking technology. PI stands for proportional integral controller, and PWM is the modulation module. MPPT is the maximum power point tracking technology. Here we take the disturbance observation method as an example for comparison and analysis. The control process specifically includes the following steps: S231, obtain photovoltaic cell parameters and collect the voltage at the photovoltaic cell end and current Signal, input maximum power point tracking control; S232: Execute maximum power point tracking control, calculate and output voltage reference value according to the collected photovoltaic voltage and current , so that the photovoltaic cell works at the maximum power point; S233, generate a voltage error signal and convert the voltage reference value The actual photovoltaic output voltage Perform comparison to generate a voltage error signal; S234, executing PI regulation, inputting the voltage error signal into a proportional-integral PI controller, performing PI regulation, and outputting a duty cycle signal for adjusting the photovoltaic converter; S235: Inputting the duty cycle signal of the photovoltaic converter into the pulse width modulation (PWM) module to generate a PWM switch signal S pv .

[0036] In step S232, the maximum power point tracking control (MPPT) specifically includes the following steps: S2321, calculating the increments of power and voltage, and calculating the relationship between the power increment and the voltage increment based on the current photovoltaic output power and voltage values; S2322. Determine the sign of the increment and adjust the working voltage. If the power increment is greater than 0, it means that the current working point is on the left side of the maximum power point. At this time, increase the working voltage of the photovoltaic cell. If the power increment is less than 0, it means that the current working point is on the right side of the maximum power point. At this time, reduce the working voltage of the photovoltaic cell. If the power increment is equal to 0, it indicates that the system has reached the maximum power point and maintain the current working voltage of the photovoltaic cell unchanged.

[0037] S2323, execute voltage adjustment according to the judgment result of the increment sign, and control the working voltage of the photovoltaic cell until the system stabilizes at the maximum power point.

[0038] S2324. Repeat the above steps to continuously collect the output parameters of the photovoltaic cells, and cyclically perform the disturbance observation operation of power and voltage to ensure that the photovoltaic system operates at the maximum power point in real time.

[0039] In step S3, the energy storage system is controlled as shown in the attached Figure 4 As shown, Indicates the DC bus voltage reference value, Indicates the DC bus voltage value, Represents the energy storage output current, PI represents the proportional integral controller, and PWM is the modulation module. The control process specifically includes the following steps: S31, obtain the DC bus voltage feedback signal and collect the current DC bus voltage value and the set DC bus voltage reference value Compare and obtain the voltage error signal , as shown in formula (3): (3); S32, perform voltage loop PI regulation, input the voltage error signal into the proportional-integral (PI) controller, perform voltage loop PI regulation, and output current reference instruction , as shown in formula (4): (4); in , Represent the voltage loop proportional and integral gains respectively.

[0040] S33, execute current loop PI adjustment, and compare the current reference command with the actual feedback current value Compare and get the current error signal. Input the current error signal into the proportional-integral (PI) controller to adjust the current loop PI and output the duty cycle signal, as shown in formula (5): (5); in , Represent the current loop proportional and integral gains respectively.

[0041] S34, generating a PWM signal, inputting the duty cycle signal into a pulse width modulation (PWM) generation module, and generating a PWM switch signal for driving the energy storage converter S bat .

[0042] In step S4, the control method adopted by photovoltaic, energy storage and inverter, combined with inverter grid control, specifically includes the following steps: S41. The photovoltaic system adopts constant voltage control.

[0043] S42. The energy storage system adopts constant DC bus voltage control and adjusts the DC bus voltage through voltage and current dual closed-loop control.

[0044] S43, the inverter uses virtual synchronous generator control technology (VSG) for network control. The control principle is shown in equation (6) and equation (7): (6); (7); Among them, the active power reference value and reactive power reference Assigned by superior dispatcher. and ω Represent the rated angular frequency and actual angular frequency of the power grid respectively, J and D p Respectively represent the system's moment of inertia and damping coefficient. In the reactive loop, and V o Respectively represent the rated phase voltage amplitude and the actual output phase voltage amplitude of the power grid, K and D q are the proportional coefficient and reactive droop coefficient respectively. The virtual synchronous generator control is adopted as the network control strategy. By simulating the main body model, active frequency regulation and reactive voltage regulation characteristics of the synchronous generator, the inertia and damping performance of the system are effectively improved. When the power grid fails or is disturbed, it can provide inertia support power to ensure the stability of the power grid frequency.

[0045] Specifically, Figure 5 The photovoltaic system adopts a constant voltage control strategy. By collecting the photovoltaic output voltage and the set reference voltage By comparison, the error signal is adjusted using a proportional integral controller (PI) to generate a control signal to drive the photovoltaic converter. The constant voltage control proposed by the present invention can track the photovoltaic output power, reduce photovoltaic interharmonics, ensure the stable operation of the photovoltaic system, reduce the DC bus voltage fluctuation caused by photovoltaic power fluctuation, and improve the overall stability and power quality of the system.

[0046] The energy storage system adopts voltage and current dual closed-loop control. First, obtain the DC bus voltage feedback signal and reference value By contrast, the voltage loop PI adjusts the output current reference instruction, and then adjusts the output duty cycle signal through the current loop PI, and finally generates a PWM signal to drive the energy storage converter. This control can ensure that the DC bus voltage is constant and effectively deal with the impact of photovoltaic power fluctuations on the energy storage system. Under traditional control, photovoltaic power fluctuations can easily cause the DC bus voltage to be unstable, increase energy storage control costs and losses, and shorten service life. The control method of the present invention can reduce photovoltaic power fluctuations, stabilize the DC bus voltage, reduce energy loss and regulation frequency of the energy storage system, extend its service life, and enhance system reliability.

[0047] The inverter uses virtual synchronous generator control technology VSG for grid control. Power reference value （ specified by the superior dispatcher), combined with the actual angular frequency of the power grid , Rated angular frequency 、System moment of inertia , damping coefficient D p In the reactive loop, according to the rated phase voltage amplitude of the power grid V n and the actual output phase voltage amplitude V o , and the proportionality factor K and reactive droop coefficient D q This control strategy simulates the characteristics of synchronous generators. When a fault or disturbance occurs in the power grid, it can provide inertia support power to ensure the stability of the grid frequency, effectively improve the system's support and regulation capabilities for the grid voltage and frequency, enhance the adaptability and compatibility of the photovoltaic storage system and the grid, and ensure the stable operation of the grid under different working conditions.

[0048] Specifically, Figure 6 (b) and Figure 6Compared with (a), after adopting the harmonic suppression method of the grid-type photovoltaic storage inverter of the present invention, the photovoltaic voltage shows higher stability. In practical applications, a stable photovoltaic voltage can ensure that the photovoltaic system operates more efficiently, reduce energy losses caused by voltage fluctuations, and improve the efficiency and quality of photovoltaic power generation. At the same time, it also reduces the adverse effects of the photovoltaic system on the energy storage system, reduces the problems of increased energy storage control costs and shortened service life caused by the transmission of photovoltaic power fluctuations to the energy storage system, and improves the overall performance and stability of the photovoltaic storage system, providing a strong guarantee for the reliable operation of the system.

[0049] Specifically, Figure 7 (b) and Figure 7 Compared with (a) in the figure, the improved DC bus voltage fluctuation is reduced from 16V to 1.2V. This is because the harmonic suppression method of the grid-type photovoltaic storage converter of the present invention effectively reduces the photovoltaic power fluctuation, thereby alleviating its impact on the DC bus voltage. It effectively extends the service life of the energy storage equipment; at the same time, it also improves the reliability and stability of the entire photovoltaic storage system, reduces various potential problems caused by DC bus voltage fluctuations, ensures efficient conversion of electric energy and stable grid connection, and improves the overall performance of the system.

[0050] Specifically, Figure 8 Showing the before and after improvements a Phase grid-connected current and fast Fourier transform analysis, Figure 8 (a) shows the improvement before a Phase grid-connected current FFT analysis results, Figure 8 (b) shows the improved a Phase grid-connected current FFT analysis results.

[0051] The grid-connected current before improvement is converted from time domain to frequency domain for analysis by fast Fourier transform. Figure 8 (a) in the figure shows the amplitude distribution under different frequency components. Under the traditional control method, the harmonic distortion of the grid-connected current is relatively serious, with more harmonic components and a large proportion of dominant interharmonics. These harmonics will increase the total harmonic distortion (THD) of the power grid, interfere with the normal operation of other equipment in the power grid, reduce the power supply reliability of the power grid, and increase the loss and heat generation of electrical equipment.

[0052] and Figure 8 (b) and Figure 8Compared with (a), the amplitude of the dominant interharmonic component is significantly reduced, and the spectrum is purer. The effectiveness of the method of the present invention in suppressing interharmonics of grid-connected current is proved. By reducing a series of measures such as photovoltaic power fluctuation, the harmonic distortion rate of grid-connected current is successfully reduced, the quality of power grid connection is effectively improved, the safe and stable operation of the power grid is guaranteed, and the energy loss and equipment failure risk caused by interharmonic problems are reduced.

[0053] Therefore, the present invention adopts the above-mentioned harmonic suppression method of a grid-type photovoltaic storage inverter, which effectively reduces energy loss and improves the stability of system operation by suppressing photovoltaic interharmonics. In view of the photovoltaic power fluctuation problem existing in traditional control strategies, it can significantly reduce photovoltaic power fluctuations, thereby alleviating the fluctuations in DC bus voltage caused by it, thereby effectively reducing the energy storage control cost and extending the service life of energy storage equipment. At the same time, it has excellent performance in grid-connected performance, can reduce the distortion rate of grid-connected voltage and current, and improve the quality of power grid connection. In addition, the introduction of a grid-connected control method in the system can effectively support the grid voltage and flexibly adjust the grid frequency, thereby enhancing the system's adaptability and support capabilities for grid operation.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for suppressing harmonics of a grid-type photovoltaic storage converter, characterized in that: The following steps are involved: S1. Obtain the DC bus voltage value, photovoltaic output voltage and current, energy storage battery voltage and current, LC filter inductor current, and grid connection point voltage and current in the current photovoltaic storage system; S2, adjust the photovoltaic output power through constant voltage control to suppress photovoltaic power fluctuations; S3, using voltage and current double closed-loop control to adjust the output of the energy storage system; S4. Based on step S2 and step S3, combined with inverter network control, the overall coordinated control of the photovoltaic storage system is completed.

2. A method for suppressing harmonics of a grid-type photovoltaic storage converter according to claim 1, characterized in that: In step S2, the photovoltaic output power is tracked based on constant voltage control to suppress photovoltaic power fluctuations. The control process specifically includes the following steps: S21, obtain the voltage difference feedback signal and collect the output voltage of the photovoltaic system and the set photovoltaic voltage reference value Compare and get the voltage error signal , as shown in formula (1): (1)； S22, perform PI regulation, input the voltage error signal into the proportional integral controller PI, and adjust the output duty cycle signal through PI, as shown in formula (2): (2)； in and They represent the proportional and integral gains in the photovoltaic proportional-integral controller respectively; S23, generate PWM signal, input the duty cycle signal output by PI into the pulse width modulation PWM module, and generate PWM control signal .

3. A method for suppressing harmonics of a grid-type photovoltaic storage converter according to claim 2, characterized in that: In step S3, the specific steps of adjusting the output of the energy storage system by using the voltage and current dual closed-loop control are as follows: S31, obtain DC bus voltage feedback signal: collect the current DC bus voltage value and the set DC voltage reference value Compare and obtain the voltage error signal , as shown in formula (3): (3)； S32, execute voltage loop PI adjustment: input voltage error signal into PI, perform voltage loop PI adjustment, and output current reference instruction , as shown in formula (4): (4)； in , Respectively represent the voltage loop proportional and integral gains; S33, execute current loop PI adjustment: compare the current reference command with the actual feedback current value By comparison, the current error signal is obtained, the current error signal is input into PI, the current loop PI is adjusted, and the duty cycle signal is output, as shown in formula (5): (5)； in , Respectively represent the current loop proportional and integral gains; S34, generating PWM signal: inputting the duty cycle signal into the pulse width modulation PWM generation module to generate a PWM switch signal for driving the energy storage converter .

4. The method for suppressing harmonics of a grid-type photovoltaic storage converter according to claim 1, characterized in that: In step S4, the control method adopted for photovoltaic, energy storage and inverter is as follows: S41, Photovoltaic system adopts constant voltage control; S42, the energy storage system adopts constant DC bus voltage control, and adjusts the DC bus voltage through voltage and current double closed-loop control; S43, the inverter adopts virtual synchronous generator control technology VSG for network control. The control principle is shown in equation (6) and equation (7). (6)； (7)； Among them, the active power reference value and reactive power reference Designated by the superior dispatcher, and ω Represent the rated angular frequency and actual angular frequency of the power grid respectively, J and D p Respectively represent the system's moment of inertia and damping coefficient; in the reactive loop, and V o Respectively represent the rated phase voltage amplitude and the actual output phase voltage amplitude of the power grid, K and D q are the proportional coefficient and reactive power droop coefficient respectively.

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