A photovoltaic energy storage system and its energy regulation method

Abstract

The present application discloses a photovoltaic energy storage system and its energy regulation method, which relates to the technical field of energy storage system control. The system includes a photovoltaic module, a micro-inverter, a battery, a first voltage converter, a second voltage converter, and a third voltage converter. The photovoltaic module, the micro-inverter, and the battery are respectively connected to a DC bus through the first voltage converter, the second voltage converter, and the third voltage converter. The method includes: based on a sampling frequency f1, collecting the voltage U at the photovoltaic module end multiple times PV , to obtain a first data set; determining whether the mean value U PV‑AVG1 of the first data set satisfies a first regulation condition; if so, adopting a first regulation strategy to regulate the system energy; if not, adopting a second regulation strategy to regulate the system energy. The present application improves the problem that the power of the micro-inverter is unstable due to the change of the output power of the photovoltaic module, and the energy scheduling is more flexible.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage system control, and in particular to a control system for a photovoltaic energy storage system and an energy regulation method thereof. Background Art

[0002] With the growing global demand for renewable energy, photovoltaic power generation, as a clean and sustainable energy form, has been increasingly widely used. Common photovoltaic power generation systems include centralized inverters, string inverters, and micro-inverters. Among them, compared with traditional centralized inverters and string inverters, micro-inverters can achieve maximum power point tracking (MPPT) at the component level, ensuring that each photovoltaic component can operate at the highest efficiency, thereby improving the power generation efficiency of the entire photovoltaic system. Moreover, its low-voltage operation characteristics can effectively reduce the fire risk caused by high-voltage arcing and improve the safety of the system. In addition, due to the modular design of micro-inverters, each micro-inverter works independently without affecting each other, improving the reliability and flexibility of the system, and is particularly suitable for household power generation fields.

[0003] Although micro-inverters have many advantages, in actual applications, micro-inverters also have some problems: First, since micro-inverters are directly connected to photovoltaic components, factors such as the temperature, light conditions, and whether there is occlusion of the photovoltaic components will affect the photovoltaic output power, resulting in unstable micro-inverter power. Second, since micro-inverters can only be used when the photovoltaic has output, they cannot well adapt to different electricity consumption demands and grid operating conditions. Summary of the Invention

[0004] In order to solve at least one of the above technical problems, the present application provides a control system for a photovoltaic energy storage system and an energy regulation method thereof.

[0005] In a first aspect, the present application provides an energy regulation method for a photovoltaic energy storage system, adopting the following technical solutions:

[0006] The photovoltaic energy storage system includes a photovoltaic component, a micro-inverter, a battery, a first voltage converter, a second voltage converter, and a third voltage converter; the photovoltaic component, the micro-inverter, and the battery are respectively connected to a DC bus through the first voltage converter, the second voltage converter, and the third voltage converter; the energy regulation method includes:

[0007] Based on a sampling frequency f1, the voltage U at the photovoltaic component end is collected multiple times PV , obtaining a first data set;

[0008] Judge whether the mean value U of the first data set PV-AVG1 satisfies a first regulation condition; wherein, the first regulation condition is: UPV-AVG1 >U TH1 , U TH1 is a preset first voltage threshold;

[0009] If so, adopt the first regulation strategy to regulate the system energy;

[0010] If not, adopt the second regulation strategy to regulate the system energy.

[0011] In a specific feasible implementation, the adoption of the first regulation strategy to regulate the system specifically includes:

[0012] Collect the bus voltage U of the DC bus BUS ; and based on the average value U PV-AVG1 and the preset first expected voltage U PVBUS , perform regulation at the photovoltaic module end to regulate the value of the bus voltage U BUS to the first expected voltage U PVBUS ;

[0013] Based on the sampling frequency f2, collect the bus voltage U BUS multiple times to obtain a second data set;

[0014] Judge whether the average value U BUS-AVG2 of the second data set meets the second regulation condition; among them, the second regulation condition is: U BUS-AVG2 >U OUTBUS , U OUTBUS is a preset second expected voltage;

[0015] If so, collect the voltage U at the micro-inverter end OUT , and based on the voltage U OUT and the second expected voltage U OUTBUS , perform regulation at the micro-inverter end to regulate the value of the bus voltage U BUS to the second expected voltage U OUTBUS ;

[0016] Based on the sampling frequency f3, collect the bus voltage U BUS multiple times to obtain a third data set;

[0017] Judge whether the average value U BUS-AVG3 of the third data set meets the third regulation condition; among them, the third regulation condition is: U BUS-AVG3 >U PVBUS -U TH2 , U TH2 is a preset second voltage threshold;

[0018] If so, collect the voltage U at the battery end BAT1, and based on the voltage U BAT1 and a preset third desired voltage U BATBUS , perform regulation at the battery end to absorb the excess energy of the system through the battery.

[0019] By adopting the above technical solution, first adjust at the photovoltaic module end to enable the photovoltaic module to output energy; then, adjust at the micro-inverter end to enable the energy to flow from the photovoltaic module to the micro-inverter; in addition, also use the battery to dynamically absorb the system energy to improve the energy utilization rate.

[0020] In a specific feasible implementation, after performing regulation at the battery end to absorb the excess energy of the system through the battery, it further includes:

[0021] Based on the sampling frequency f4, collect the bus voltage U BUS multiple times to obtain a fourth data set;

[0022] Judge whether the mean value U BUS-AVG4 of the fourth data set meets the fourth regulation condition; wherein, the fourth regulation condition is: U BUS-AVG4 <U PVBUS -U TH3 , U TH3 is a preset third voltage threshold;

[0023] If so, collect the voltage U BAT2 at the battery end, and based on the voltage U BAT2 and the third desired voltage U BATBUS , perform secondary regulation at the battery end to supplement the system energy through the battery.

[0024] By adopting the above technical solution, by monitoring the bus voltage U BUS in real time, when the energy output by the photovoltaic module is insufficient and the battery needs to discharge to supplement the system energy, through the secondary regulation at the battery end, the system energy is flexibly allocated to maintain the stability of the bus voltage.

[0025] In a specific feasible implementation, the energy regulation method further includes: adjusting the value of the sampling frequency f1 based on the first data set;

[0026] Adjusting the value of the sampling frequency f2 based on the second data set;

[0027] Adjusting the value of the sampling frequency f3 based on the third data set;

[0028] Adjusting the value of the sampling frequency f4 based on the fourth data set;

[0029] wherein, , , β is a set adjustment coefficient;

[0030] When i = 1, is the standard deviation of the difference between U in the first data set and U PV and U TH1 , f i is the sampling frequency f1, f adjust-i is the adjusted value of the sampling frequency f1;

[0031] When i = 2, is the standard deviation of the difference between U in the second data set and U BUS and U OUTBUS , f i is the sampling frequency f2, f adjust-i is the adjusted value of the sampling frequency f2;

[0032] When i = 3, is the standard deviation of the difference between U in the third data set and U BUS and U PVBUS -U TH2 , f i is the sampling frequency f3, f adjust-i is the adjusted value of the sampling frequency f3;

[0033] When i = 4, is the standard deviation of the difference between U in the fourth data set and U BUS and U PVBUS -U TH3 , f i is the sampling frequency f4, f adjust-i is the adjusted value of the sampling frequency f4.

[0034] By adopting the above technical solution, after the system is collected according to the initially set sampling frequency, the voltage fluctuation situation is judged based on the collected data, so as to adjust the initial sampling frequency and reduce the influence of voltage fluctuation on the accuracy and reliability of system regulation.

[0035] In a specific feasible implementation, the second regulation strategy is adopted to regulate the system energy, which specifically includes:

[0036] Collect the bus voltage U of the DC bus BUS and the voltage U at the battery terminal BAT3 ;

[0037] Based on the voltage U BAT3 and the preset third expected voltage U of the DC bus BATBUS , regulation is carried out at the battery terminal to supplement the system energy through the battery.

[0038] By adopting the above technical solution, when the output of the photovoltaic module is very small or even basically zero, the battery is directly discharged to provide energy for the system.

[0039] In a specific implementable embodiment, the first voltage converter includes a switching transistor Q1 and a switching transistor Q2; wherein, the switching transistor Q1 is connected between the positive electrode of the photovoltaic module and the positive bus of the DC bus, and one end of the switching transistor Q2 is connected to the intermediate node between the positive electrode of the photovoltaic module and the switching transistor Q1, and the other end is connected to the negative electrode of the photovoltaic module and the negative bus of the DC bus;

[0040] Based on the mean value U PV-AVG1 and a preset first expected voltage U PVBUS , regulation is performed at the photovoltaic module end, specifically including:

[0041] Based on the mean value U PV-AVG1 and a preset first expected voltage U PVBUS , the first duty ratio D1 and the second duty ratio D2 are respectively calculated; wherein, U PV-AVG1 =U PVBUS *(1 - D1); D2 = 1 - D1;

[0042] Based on the first duty ratio D1 and the second duty ratio D2, the switching transistors Q1 and Q2 are respectively controlled to be turned on and off.

[0043] In a specific implementable embodiment, the second voltage converter includes a switching transistor Q3 and a switching transistor Q4, wherein, the switching transistor Q3 is connected between the positive electrode of the micro-inverter and the positive bus of the DC bus, and one end of the switching transistor Q4 is connected to the intermediate node between the positive electrode of the micro-inverter and the switching transistor Q3, and the other end is connected to the negative electrode of the micro-inverter and the negative bus of the DC bus;

[0044] Based on the voltage U OUT and the second expected voltage U OUTBUS , regulation is performed at the micro-inverter end, specifically including:

[0045] Based on the voltage U OUT and the second expected voltage U OUTBUS , the third duty ratio D3 and the fourth duty ratio D4 are respectively calculated; wherein, U OUT =U OUTBUS *D3; D4 = 1 - D3;

[0046] Based on the third duty ratio D3 and the fourth duty ratio D4, the switching transistors Q3 and Q4 are respectively controlled to be turned on and off.

[0047] In a specific implementable embodiment, the third voltage converter includes a switching transistor Q5 and a switching transistor Q6. Among them, the switching transistor Q5 is connected between the positive electrode of the battery and the positive bus of the DC bus, and one end of the switching transistor Q6 is connected to the middle node between the positive electrode of the battery and the switching transistor Q5, and the other end is connected to the negative electrode of the battery and the negative bus of the DC bus;

[0048] Based on the voltage U BAT1 and a preset third desired voltage U BATBUS , regulation is performed at the battery end, specifically including:

[0049] Based on the voltage U BAT1 and the third desired voltage U BATBUS , a fifth duty cycle D5 and a sixth duty cycle D6 are respectively calculated; among them, U BAT1 =U BATBUS *D5; D6 = 1 - D5;

[0050] Based on the fifth duty cycle D5 and the sixth duty cycle D6, on - off control is respectively performed on the switching transistor Q5 and the switching transistor Q6.

[0051] In a specific implementable embodiment, based on the voltage U BAT2 and the third desired voltage U BATBUS , secondary regulation is performed at the battery end, specifically including:

[0052] Based on the voltage U BAT2 and the third desired voltage U BATBUS , the values of the fifth duty cycle D5 and the sixth duty cycle D6 are updated; among them, U BAT2 =U BATBUS *(1 - D5); D6 = 1 - D5;

[0053] Based on the updated values of the fifth duty cycle D5 and the sixth duty cycle D6, on - off control is respectively performed on the switching transistor Q5 and the switching transistor Q6.

[0054] In a second aspect, the present application provides a photovoltaic energy storage system, adopting the following technical solution: The photovoltaic energy storage system includes a photovoltaic module, a micro - inverter, a battery, a first voltage converter, a second voltage converter, and a third voltage converter; the photovoltaic module, the micro - inverter, and the battery are respectively connected to the DC bus through the first voltage converter, the second voltage converter, and the third voltage converter; when the photovoltaic energy storage system operates, it adopts the photovoltaic energy storage system energy regulation method described in the above - mentioned first aspect or any implementable embodiment of the first aspect.

[0055] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0056] In the technical solution of the present application, corresponding control strategies are adopted at the photovoltaic module end, the micro-inverter end, and the battery end. Through comprehensive coordinated control, the problem that the power of the micro-inverter is unstable due to the influence of temperature, light conditions, occlusion, etc. on the output power of the photovoltaic module is improved. In addition, a battery is added to the system to participate in the means of solving the output power fluctuation of the photovoltaic module, better adapting to different electricity consumption demands and making the energy scheduling more flexible. This not only improves the overall energy utilization efficiency but also enhances the reliability and stability of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 is a schematic structural diagram of a photovoltaic energy storage system in an embodiment of the present application;

[0058] Figure 2 is a schematic flowchart of a method for regulating energy of a photovoltaic energy storage system in an embodiment of the present application;

[0059] Figure 3 is another schematic flowchart of a method for regulating energy of a photovoltaic energy storage system in an embodiment of the present application;

[0060] Figure 4 is a schematic diagram of the voltage, current, and power changes at the micro-inverter end when tracking the maximum power point of a photovoltaic module in an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0061] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments.

[0062] In the description of the embodiments of the present application, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the technical features indicated. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. The terms "include", "comprise", "have" and their variants all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0063] The embodiments of the present application provide a method for regulating energy of a photovoltaic energy storage system, as Figure 1As shown, the photovoltaic energy storage system includes a photovoltaic module, a micro-inverter, a battery, a first voltage converter, a second voltage converter, and a third voltage converter. Among them, the photovoltaic module, the micro-inverter, and the battery are respectively connected to the DC bus through the first voltage converter, the second voltage converter, and the third voltage converter.

[0064] Further, the first voltage converter is a unidirectional BOOST converter, the second voltage converter is a unidirectional BUCK converter, and the third voltage converter is a bidirectional BUCK-BOOST converter. The first voltage converter, the second voltage converter, and the third voltage converter are all of the DC-DC type. The back end of the micro-inverter is connected to a load or the grid and is used to convert direct current into alternating current. A capacitor C1 for supporting the bus voltage is also provided on the DC bus. A filter capacitor C2 is connected between the photovoltaic module and the first voltage converter. A filter capacitor C3 is connected between the micro-inverter and the second voltage converter. A filter capacitor C4 is connected between the battery and the third voltage converter.

[0065] As Figure 2 shown, the energy regulation method includes the following steps S1 - S2:

[0066] S1, based on the sampling frequency f1, collect the voltage U PV at the photovoltaic module end multiple times to obtain a first data set.

[0067] S2, determine whether the mean value U PV-AVG1 of the first data set satisfies a first regulation condition. Among them, the first regulation condition is: U PV-AVG1 > U TH1 , and U TH1 is a preset first voltage threshold.

[0068] S3, if so, adopt a first regulation strategy to regulate the system energy;

[0069] If not, adopt a second regulation strategy to regulate the system energy.

[0070] It can be understood that the first regulation condition is used to judge whether the photovoltaic module has energy output. When the first regulation condition is satisfied, it means that the photovoltaic module has energy output at this time, and then the first regulation strategy is adopted accordingly. When the first regulation condition is not satisfied, it means that the output voltage of the photovoltaic module is low or there is no energy output at this time, and then the second regulation strategy is adopted accordingly. Then for the value of U TH1 , it needs to be determined according to the number of panels of the photovoltaic module connected. It can be set to 0 or leave a certain margin and set it to a value slightly larger than 0. This application does not make specific limitations on this.

[0071] In a possible implementation, in combination with Figure 3 , step S3, the first regulation strategy is used to regulate the system energy, which specifically includes steps A1 - A5:

[0072] A1. Collect the bus voltage U of the DC bus BUS ; and based on the average value U PV-AVG1 and the preset first expected voltage U PVBUS , perform regulation at the photovoltaic module end to regulate the value of the bus voltage U BUS to the first expected voltage U PVBUS .

[0073] Through step A1, first adjust at the photovoltaic module end to make the most of the output of the photovoltaic module and provide energy for the system.

[0074] In a possible implementation, continue to refer to Figure 1 , the first voltage converter includes a switching tube Q1 and a switching tube Q2. Among them, the switching tube Q1 is connected between the positive pole of the photovoltaic module and the positive bus of the DC bus, and one end of the switching tube Q2 is connected to the middle node between the positive pole of the photovoltaic module and the switching tube Q1, and the other end is connected to the negative pole of the photovoltaic module and the negative bus of the DC bus;

[0075] Further, the first voltage converter further includes a storage inductor L1, and the storage inductor L1 is connected between the photovoltaic module and the switching tube Q1.

[0076] In this step, based on the average value U PV-AVG1 and the preset first expected voltage U PVBUS , perform regulation at the photovoltaic module end, which specifically includes steps A11 - A12.

[0077] A11. Based on the average value U PV-AVG1 and the preset first expected voltage U PVBUS , calculate the first duty cycle D1 and the second duty cycle D2 respectively; where, U PV-AVG1 = U PVBUS * (1 - D1); D2 = 1 - D1;

[0078] A12. Based on the first duty cycle D1 and the second duty cycle D2, perform on - off control on the switching tube Q1 and the switching tube Q2 respectively.

[0079] In a possible implementation, after step A12, where the on - off control is performed on the switching tube Q1 and the switching tube Q2 respectively, the following steps A13 - A14 are further included:

[0080] A13. Monitor the bus voltage UBUS and compare the bus voltage U BUS with the first desired voltage U PVBUS ;

[0081] A14, if U BUS < U PVBUS , then increase the value of the first duty cycle D1 and decrease the value of the second duty cycle D2;

[0082] If U BUS > U PVBUS , then decrease the value of the first duty cycle D1 and increase the value of the second duty cycle D2.

[0083] Those skilled in the art can understand that when adjusting the values of D1 and D2, it is also necessary to ensure that D1 + D2 = 1.

[0084] Therefore, through steps A13 - A14, after controlling the duty cycles of the switching transistors Q1 and Q2, continuously monitor whether the bus voltage U BUS is adjusted in place, and correspondingly adjust the duty cycles of the switching transistors to eliminate system interference and maintain the stability of the bus voltage.

[0085] A2, based on the sampling frequency f2, collect the bus voltage U BUS multiple times to obtain a second data set;

[0086] A3, determine whether the mean value U BUS-AVG2 of the second data set satisfies a second regulation condition; wherein, the second regulation condition is: U BUS-AVG2 > U OUTBUS , and U OUTBUS is a preset second desired voltage.

[0087] Those skilled in the art can understand that if the second regulation condition is satisfied, it means that the power generation of the photovoltaic module can flow to the micro-inverter, and the energy is regulated by the inverter.

[0088] A4, if so, collect the voltage U OUT at the micro-inverter end, and based on the voltage U OUT and the second desired voltage U OUTBUS , perform regulation at the micro-inverter end to make the energy output by the photovoltaic module flow to the micro-inverter and regulate the value of the bus voltage U BUS to the second desired voltage U OUTBUS .

[0089] Therefore, through steps A2 - A4, after adjusting at the photovoltaic module end, then perform adjustment at the micro-inverter end to make the energy flow from the photovoltaic module to the micro-inverter and provide energy for the load.

[0090] In a possible implementation, with continued reference to Figure 1 , the second voltage converter includes a switching transistor Q3 and a switching transistor Q4. Among them, the switching transistor Q3 is connected between the positive electrode of the micro-inverter and the positive bus of the DC bus, and one end of the switching transistor Q4 is connected to the intermediate node between the positive electrode of the micro-inverter and the switching transistor Q3, and the other end is connected to the negative electrode of the micro-inverter and the negative bus of the DC bus;

[0091] Furthermore, the second voltage converter further includes a storage inductor L2, and the storage inductor L2 is connected between the micro-inverter and the switching transistor Q3; the voltage U OUT at the micro-inverter end is the voltage value at the intermediate node between the micro-inverter and the second voltage converter.

[0092] In step A4, based on the voltage U OUT and the second desired voltage U OUTBUS , regulation is performed at the micro-inverter end, specifically including the following steps A41 - A42:

[0093] A41, based on the voltage U OUT and the second desired voltage U OUTBUS , calculate a third duty cycle D3 and a fourth duty cycle D4 respectively; among them, U OUT = U OUTBUS * D3; D4 = 1 - D3;

[0094] A42, based on the third duty cycle D3 and the fourth duty cycle D4, perform on-off control on the switching transistor Q3 and the switching transistor Q4 respectively.

[0095] In a possible implementation, after step A42, when performing on-off control on the switching transistor Q3 and the switching transistor Q4 respectively, the following steps A43 - A44 are further included:

[0096] A43, monitor the bus voltage U BUS , and compare the bus voltage U BUS and the second desired voltage U OUTBUS ;

[0097] A44, if U BUS < U OUTBUS , then increase the value of the third duty cycle D3 and decrease the value of the fourth duty cycle D4;

[0098] If U BUS > U OUTBUS , then decrease the value of the third duty cycle D3 and increase the value of the fourth duty cycle D4.

[0099] Those skilled in the art can understand that when adjusting the values of D3 and D4, it is also necessary to ensure that D3 + D4 = 1.

[0100] Therefore, through steps A53 - A54, after controlling the duty cycles of the switching transistors Q3 and Q4, continuously monitor the bus voltage U BUS to determine whether the adjustment is in place, and correspondingly adjust the duty cycle of the switching transistor to eliminate system interference and maintain the stability of the bus voltage.

[0101] A5, based on the sampling frequency f3, collect the bus voltage U BUS multiple times to obtain a third data set;

[0102] A6, determine whether the mean value U BUS-AVG3 of the third data set meets the third regulation condition; where the third regulation condition is: U BUS-AVG3 > U PVBUS - U TH2 and U TH2 is a preset second voltage threshold, and U TH2 is, for example, 2V.

[0103] It can be understood that the third regulation condition is used to determine whether there is excess energy in the system to charge the battery; when in step A4, the energy flows to the micro-inverter, the micro-inverter starts to track the maximum power point of the photovoltaic module, which in turn causes the voltage U OUT at the micro-inverter end and the voltage U PV at the photovoltaic module end to decrease, and the bus voltage U BUS also decreases. To maintain the bus voltage U BUS at the target value, the duty cycles corresponding to the switching transistor Q1 in the first voltage converter and the switching transistor Q3 in the second voltage converter will increase until the micro-inverter tracks the maximum power point.

[0104] As Figure 4 shown, during the process of the micro-inverter tracking the maximum power point of the photovoltaic module, the voltage U OUT , current, and power at the micro-inverter end satisfy the relationship shown in Figure 4 . In the figure, the blue line is the current curve and the orange line is the power curve.

[0105] A7, if so, collect the voltage U BAT1 at the battery end, and based on the voltage U BAT1 and the preset third expected voltage U BATBUS , perform regulation at the battery end. The battery absorbs the excess energy in the system to regulate the value of the bus voltage U BUS to the third expected voltage U BATBUS .

[0106] Therefore, through step A7, the remaining energy generated by the photovoltaic module is directed to the battery to charge the battery and improve the energy utilization rate.

[0107] In a possible implementation, continue to refer to Figure 1 , the third voltage converter includes a switching transistor Q5 and a switching transistor Q6. Among them, the switching transistor Q5 is connected between the positive pole of the battery and the positive bus of the DC bus, and one end of the switching transistor Q6 is connected to the middle node between the positive pole of the battery and the switching transistor Q5, and the other end is connected to the negative pole of the battery and the negative bus of the DC bus;

[0108] Furthermore, the third voltage converter further includes a storage inductor L3, and the storage inductor L3 is connected between the battery and the switching transistor Q5.

[0109] In step A7, based on the voltage U BAT1 and a preset third desired voltage U BATBUS , regulation is performed at the battery end, which specifically includes the following steps A71 - A72:

[0110] A71, based on the voltage U BAT1 and the third desired voltage U BATBUS , calculate a fifth duty cycle D5 and a sixth duty cycle D6 respectively; where, U BAT1 =U BATBUS *D5; D6 = 1 - D5;

[0111] A72, based on the fifth duty cycle D5 and the sixth duty cycle D6, perform on - off control on the switching transistor Q5 and the switching transistor Q6 respectively.

[0112] In a possible implementation, after step A72, where on - off control is performed on the switching transistor Q5 and the switching transistor Q6 respectively, the following steps A73 - A74 are further included:

[0113] A73, monitor the bus voltage U BUS , and compare the bus voltage U BUS with the third desired voltage U BATBUS ;

[0114] A74, if U BUS <U BATBUS , then increase the value of the fifth duty cycle D5 and decrease the value of the sixth duty cycle D6;

[0115] If U BUS >U BATBUS , then decrease the value of the fifth duty cycle D5 and increase the value of the sixth duty cycle D6.

[0116] Those skilled in the art can understand that when adjusting the values of D5 and D6, it is also necessary to ensure that D5 + D6 = 1.

[0117] Therefore, through steps A73 - A74, after controlling the duty cycles of switch tubes Q5 and Q6, continuously monitor the bus voltage U BUS to check whether the adjustment is in place, and correspondingly adjust the duty cycle of the switch tube to eliminate system interference and maintain the stability of the bus voltage.

[0118] In a possible implementation manner, in step A7, after regulating at the battery end and having the battery absorb the excess energy of the system, the following steps A8 - A10 are further included:

[0119] A8, based on the sampling frequency f4, collect the bus voltage U BUS multiple times to obtain a fourth data set.

[0120] A9, determine whether the mean value U BUS-AVG4 of the fourth data set meets the fourth regulation condition; wherein, the fourth regulation condition is: U BUS-AVG4 <U PVBUS -U TH3 where U TH3 is a preset third voltage threshold, and U TH3 is, for example, 4V.

[0121] A10, if so, collect the voltage U BAT2 at the battery end, and based on the voltage U BAT2 and the third expected voltage U BATBUS , perform secondary regulation at the battery end to supplement the system energy through the battery and regulate the value of the bus voltage U BUS to the third expected voltage U BATBUS .

[0122] Therefore, through real-time monitoring of the bus voltage U BUS , when the fourth regulation condition is met, it indicates that the energy output by the photovoltaic module is insufficient at this time, and the battery needs to discharge to supplement the system energy. Through secondary regulation at the battery end, the system energy is flexibly allocated to maintain the stability of the bus voltage and the output power of the photovoltaic module.

[0123] In a possible implementation manner, in step A10, based on the voltage U BAT2 and the third expected voltage U BATBUS , performing secondary regulation at the battery end specifically includes the following steps A101 - A102:

[0124] A101, based on the voltage U BAT2 and the third expected voltage U BATBUS, update the values of the fifth duty cycle D5 and the sixth duty cycle D6; where, U BAT2 =U BATBUS *(1 - D5); D6 = 1 - D5;

[0125] A102, based on the updated values of the fifth duty cycle D5 and the sixth duty cycle D6, respectively control the on - off of the switching transistor Q5 and the switching transistor Q6.

[0126] Those skilled in the art can understand that when the fourth regulation condition is not met, there is no need to control the battery discharge.

[0127] In a possible implementation manner, after obtaining the first data set in step S1, it further includes:

[0128] Based on the first data set, adjust the value of the sampling frequency f1;

[0129] After obtaining the second data set in step A2, it further includes: Based on the second data set, adjust the value of the sampling frequency f2;

[0130] After obtaining the third data set in step A5, it further includes: Based on the third data set, adjust the value of the sampling frequency f3;

[0131] After obtaining the fourth data set in step A8, it further includes: Based on the fourth data set, adjust the value of the sampling frequency f4;

[0132] Where, , , β is a set adjustment coefficient; represents the degree of voltage fluctuation;

[0133] When i = 1, is the standard deviation of the difference between U PV and U TH1 in the first data set, f i is the sampling frequency f1, f adjust-i is the value of the sampling frequency f1 after adjustment;

[0134] When i = 2, is the standard deviation of the difference between U BUS and U OUTBUS in the second data set, f i is the sampling frequency f2, f adjust-i is the value of the sampling frequency f2 after adjustment;

[0135] When i = 3, is the standard deviation of the difference between U BUS and U PVBUS -UTH2 Standard deviation of the difference, f i Is the sampling frequency f3, f adjust-i Is the adjusted value of the sampling frequency f3;

[0136] When i = 4, Is U in the fourth data set BUS And U PVBUS -U TH3 Standard deviation of the difference, f i Is the sampling frequency f4, f adjust-i Is the adjusted value of the sampling frequency f4.

[0137] Preferably, at the initial setting, the sampling frequencies f1, f2, f3, f4 are the same, all being 20 kHz.

[0138] Therefore, after the system is collected according to the initially set sampling frequency, the voltage fluctuation situation is judged based on the collected data, so as to adjust the initial sampling frequency and reduce the influence of voltage fluctuation on the accuracy and reliability of system regulation.

[0139] In a possible implementation manner, in combination with Figure 3 , the above step S3, a second regulation strategy is adopted to regulate the system energy, which specifically includes the following steps B1 - B3:

[0140] B1, collect the bus voltage U of the DC bus BUS And the voltage U at the battery terminal BAT3 ;

[0141] B2, based on the voltage U BAT3 And the preset third expected voltage U of the DC bus BATBUS , perform regulation at the battery terminal, and provide energy for the system by discharging the battery, and regulate the value of the bus voltage U BUS To the third expected voltage U BATBUS .

[0142] Specifically, in step B2, based on the voltage U BAT3 And the preset third expected voltage U of the DC bus BATBUS , perform regulation at the battery terminal, which specifically includes the following steps B21 - B22:

[0143] B21, based on the voltage U BAT3 And the preset third expected voltage U of the DC bus BATBUS , calculate the values of the seventh duty ratio D7 and the eighth duty ratio D8; where, U BAT3 =U BATBUS *(1 - D7); D8 = 1 - D7;

[0144] B22. Based on the values of the seventh duty cycle D7 and the eighth duty cycle D8, the on / off control of the switching transistor Q5 and the switching transistor Q6 is respectively performed.

[0145] Therefore, when the output of the photovoltaic module is very small or even basically non-existent, through steps B1 - B2, the battery is directly discharged to provide energy for the system.

[0146] That is to say, the main idea of this application is as follows: First, when it is determined that the photovoltaic module has an output under the first regulation condition, by controlling the output of the photovoltaic module, the bus voltage is regulated to the first desired voltage U PVBUS ; then, when it is determined that the energy output by the photovoltaic module can flow to the micro-inverter to supply power to the load under the second regulation condition, through the regulation at the micro-inverter end, the bus voltage is regulated to the second desired voltage U OUTBUS , so that the photovoltaic module operates at the maximum power point; then, when it is determined that the energy output by the photovoltaic module is excessive under the third regulation condition, through the regulation at the battery end, the battery is used to absorb the excess energy of the system, and the bus voltage is regulated to the third desired voltage U BATBUS ; finally, when it is determined that the energy output by the photovoltaic module is insufficient under the fourth regulation condition, through the regulation at the battery end, the battery is used to supplement the system energy, and the bus voltage is stabilized to the third desired voltage U again BATBUS .

[0147] For several preset desired voltage values, their magnitude relationship is: the first desired voltage U PVBUS > the second desired voltage U OUTBUS > the third desired voltage U BATBUS .

[0148] Therefore, the technical solution of this application adopts corresponding control strategies at the photovoltaic module end, the micro-inverter end and the battery end. Through comprehensive coordinated control, it improves the problem that the power of the micro-inverter is unstable due to the influence of temperature, light conditions and shading on the output power of the photovoltaic module; in addition, adding a battery to the system not only participates in the means of solving the output power fluctuation of the photovoltaic module, better adapts to different electricity consumption demands, and makes the energy scheduling more flexible; for example, when the energy of the photovoltaic module is sufficient, the excess energy is stored in the battery to ensure that the photovoltaic module operates at the maximum power point and improve the power generation efficiency; when the light is insufficient or at night, the electric energy is released to supplement the system energy, which not only improves the overall energy utilization efficiency, but also enhances the reliability and stability of the entire system.

[0149] Those skilled in the art can understand that the voltage at the photovoltaic module end in this embodiment is the voltage at the intermediate node between the first voltage converter and the photovoltaic module; the voltage at the micro-inverter end is the voltage at the intermediate node between the micro-inverter and the second voltage converter; the voltage at the battery end is the voltage at the intermediate node between the battery and the third voltage converter.

[0150] An embodiment of the present application provides a photovoltaic energy storage system, including a photovoltaic module, a micro-inverter, a battery, a first voltage converter, a second voltage converter, and a third voltage converter; the photovoltaic module, the micro-inverter, and the battery are respectively connected to a DC bus through the first voltage converter, the second voltage converter, and the third voltage converter; when the photovoltaic energy storage system operates, the above-mentioned photovoltaic energy storage system energy regulation method is adopted.

[0151] The above are all preferred embodiments of the present application, and do not limit the protection scope of the present application accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A photovoltaic energy storage system energy control method, characterized in that: The photovoltaic energy storage system includes a photovoltaic module, a micro inverter, a battery, a first voltage converter, a second voltage converter and a third voltage converter; the photovoltaic module, the micro inverter and the battery are connected to a DC bus through the first voltage converter, the second voltage converter and the third voltage converter respectively; the energy regulation method includes: Based on the sampling frequency f1, the voltage U at the photovoltaic module end is collected PV , obtain a first data set; Determine the mean U of the first data set PV-AVG1 Whether the first control condition is met; the first control condition is: U PV-AVG1 >U TH1 , U TH1 is a preset first voltage threshold; if so, the first control strategy is adopted to control the system energy; if not, the second control strategy is adopted to control the system energy; The adopting the first control strategy to control the system includes: Collect the bus voltage U of the DC bus BUS ; and based on the mean U PV-AVG1 and the preset first expected voltage U PVBUS , and regulate the bus voltage U BUS The value of the voltage is adjusted to the first desired voltage U PVBUS ; Based on the sampling frequency f2, the bus voltage U is collected BUS , obtain a second data set; Determine the mean U of the second data set BUS-AVG2 Whether the second control condition is met; the second control condition is: U BUS-AVG2 >U OUTBUS , U OUTBUS is the preset second expected voltage; if so, the voltage U at the micro inverter end is collected OUT , and based on the voltage U OUT and the second desired voltage U OUTBUS , and regulate the bus voltage U BUS The value is adjusted to the second desired voltage U OUTBUS ; Based on the sampling frequency f3, the bus voltage U is collected BUS , obtain a third data set; Determine the mean U of the third data set BUS-AVG3 Whether the third control condition is met; the third control condition is: U BUS-AVG3 >U PVBUS -U TH2 , U TH2 is the preset second voltage threshold; if so, the voltage U at the battery terminal is collected BAT1 , and based on the voltage U BAT1 and the preset third expected voltage U BATBUS , it is regulated at the battery end, and the excess energy of the system is absorbed through the battery; After the battery absorbs the excess energy of the system, it also includes: Based on the sampling frequency f4, the bus voltage U is collected BUS , obtaining a fourth data set; Determine the mean U of the fourth data set BUS-AVG4 Whether the fourth control condition is met; the fourth control condition is: U BUS-AVG4 <U PVBUS -U TH3 , U TH3 is the preset third voltage threshold; if so, the voltage U at the battery terminal is collected BAT2 , and based on the voltage U BAT2 and the third desired voltage U BATBUS , perform secondary regulation at the battery end to supplement system energy through the battery; The method further includes: adjusting the value of the sampling frequency f1 based on the first data set; adjusting the value of the sampling frequency f2 based on the second data set; adjusting the value of the sampling frequency f3 based on the third data set; adjusting the value of the sampling frequency f4 based on the fourth data set; Among them, f adjust-i =f i *g(σ i ), β is the set adjustment coefficient, i∈{1,2,3,4}, σ1 is the value of U in the first data set PV with U TH1 The standard deviation of the difference between the two, σ2 is the standard deviation of the difference between the two, and σ2 is the standard deviation of the difference between the two, BUS with U OUTBUS The standard deviation of the difference between the two, σ3 is the standard deviation of the difference between the two, and σ4 is the standard deviation of the difference between the two, σ3 is the standard deviation of the difference between the two, and σ3 is the standard deviation of the difference between the two, BUS with U PVBUS -U TH2 The standard deviation of the difference between the two, σ4 is the standard deviation of the difference between the two, and σ4 is the standard deviation of the difference between the two, BUS with U PVBUS -U TH3 The standard deviation of the difference, f adjust-i is the sampling frequency f i Adjusted value; The second control strategy is used to control the system energy, specifically including: collecting the bus voltage U of the DC bus BUS and the battery terminal voltage U BAT3 ; Based on voltage U BAT3 and the preset DC bus third expected voltage U BATBUS , it is regulated at the battery end and the system energy is supplemented by the battery.

2. The photovoltaic energy storage system energy control method according to claim 1, characterized in that: The first voltage converter includes a switch tube Q1 and a switch tube Q2; wherein the switch tube Q1 is connected between the positive electrode of the photovoltaic module and the positive busbar of the DC busbar, one end of the switch tube Q2 is connected to the positive electrode of the photovoltaic module and the intermediate node of the switch tube Q1, and the other end is connected to the negative electrode of the photovoltaic module and the negative busbar of the DC busbar; Based on the mean value U PV-AVG1 and the preset first expected voltage U PVBUS , and regulate the photovoltaic modules, including: Based on the mean value U PV-AVG1 and the preset first expected voltage U PVBUS , respectively calculate the first duty cycle D1 and the second duty cycle D2; where U PV-AVG1 =U PVBUS *(1-D1); D2=1-D1; Based on the first duty cycle D1 and the second duty cycle D2, the switch tube Q1 and the switch tube Q2 are respectively controlled to be on and off.

3. The photovoltaic energy storage system energy control method according to claim 1, characterized in that: The second voltage converter includes a switch tube Q3 and a switch tube Q4, wherein the switch tube Q3 is connected between the positive electrode of the micro-inverter and the positive bus of the DC bus, one end of the switch tube Q4 is connected to the positive electrode of the micro-inverter and the middle node of the switch tube Q3, and the other end is connected to the negative electrode of the micro-inverter and the negative bus of the DC bus; Based on the voltage U OUT and the second desired voltage U OUTBUS , and control is performed at the micro inverter end, specifically including: based on the voltage U OUT and the second desired voltage U OUTBUS , respectively calculate the third duty cycle D3 and the fourth duty cycle D4; wherein, U OUT =U OUTBUS *D3;D4=1-D3; Based on the third duty cycle D3 and the fourth duty cycle D4, the switch tube Q3 and the switch tube Q4 are respectively controlled to be on and off.

4. The photovoltaic energy storage system energy control method according to claim 1, characterized in that: The third voltage converter includes a switch tube Q5 and a switch tube Q6, wherein the switch tube Q5 is connected between the positive electrode of the battery and the positive busbar of the DC bus, one end of the switch tube Q6 is connected to the positive electrode of the battery and the middle node of the switch tube Q5, and the other end is connected to the negative electrode of the battery and the negative busbar of the DC bus; Based on the voltage U BAT1 and the preset third expected voltage U BATBUS , and regulate at the battery end, including: Based on the voltage U BAT1 and the third desired voltage U BATBUS , respectively calculate the fifth duty cycle D5 and the sixth duty cycle D6; wherein, U BAT1 =U BATBUS *D5;D6=1-D5; Based on the fifth duty cycle D5 and the sixth duty cycle D6, the switch tube Q5 and the switch tube Q6 are respectively controlled to be on and off.

5. The photovoltaic energy storage system energy control method according to claim 4, characterized in that: Based on the voltage U BAT2 and the third desired voltage U BATBUS , perform secondary regulation at the battery end, including: Based on the voltage U BAT2 and the third desired voltage U BATBUS , update the values ​​of the fifth duty cycle D5 and the sixth duty cycle D6; wherein, U BAT2 =U BATBUS *(1-D5); D6=1-D5; Based on the updated values ​​of the fifth duty cycle D5 and the sixth duty cycle D6, the switch tube Q5 and the switch tube Q6 are respectively controlled to be on and off.

6. A photovoltaic energy storage system, characterized in that: It includes a photovoltaic component, a micro inverter, a battery, a first voltage converter, a second voltage converter and a third voltage converter; the photovoltaic component, the micro inverter and the battery are connected to a DC bus through the first voltage converter, the second voltage converter and the third voltage converter respectively; when the photovoltaic energy storage system is in operation, the photovoltaic energy storage system energy control method according to any one of claims 1 to 5 is adopted.

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