Photovoltaic energy storage system and energy regulation and control method thereof

Abstract

The invention discloses a photovoltaic energy storage system and an energy regulation and control method thereof, and relates to the technical field of energy storage system control, and the system comprises 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 direct current bus through the first voltage converter, the second voltage converter and the third voltage converter; the method comprises the following steps: based on a sampling frequency f1, acquiring a voltage UPV of a photovoltaic module end for multiple times to obtain a first data set; judging whether the mean value UPV-AVG1 of the first data set meets a first regulation and control condition or not; if yes, regulating and controlling the system energy by adopting a first regulation and control strategy; and if not, regulating and controlling the system energy by adopting a second regulation and control strategy. The problem that the power of the micro inverter is unstable due to the change of the output power of the photovoltaic module is solved, and the energy dispatching 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 photovoltaic energy storage system control system and an energy regulation method thereof. Background Art

[0002] As the global demand for renewable energy continues to grow, photovoltaic power generation is becoming more and more widely used as a clean and sustainable form of energy. Common photovoltaic power generation systems include centralized inverters, string inverters and micro inverters. 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 work 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 risk of fire 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, which improves the reliability and flexibility of the system, especially suitable for household power generation.

[0003] Although micro inverters have many advantages, they also have some problems in actual application: First, since the micro inverter is directly connected to the photovoltaic module, the temperature, lighting conditions, and whether there is any obstruction of the photovoltaic module will affect the photovoltaic output power, resulting in unstable power of the micro inverter; second, since the micro inverter can only be used when the photovoltaic has output, it cannot adapt well to different power demand and grid operation status. Summary of the invention

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

[0005] In the first aspect, the present application provides a method for energy regulation of a photovoltaic energy storage system, which adopts 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 connected to a DC bus through the first voltage converter, the second voltage converter and the third voltage converter respectively; the energy control method includes: Based on the sampling frequency f1, the voltage U at the photovoltaic module end is collected multiple times PV , obtain a first data set; Determine the mean value U of the first data set PV-AVG1 Whether the first control condition is met; wherein the first control condition is: PV-AVG1 >U TH1 , U TH1is a preset first voltage threshold; If so, the first control strategy is used to control the system energy; If not, the second control strategy is used to control the system energy.

[0006] In a specific implementation scheme, the first control strategy is used to control the system, specifically including: Collect the bus voltage U of the DC bus BUS ; and based on the mean value U PV-AVG1 and the preset first expected voltage U PVBUS , and regulate the bus voltage U BUS The value of the first desired voltage U PVBUS ; Based on the sampling frequency f2, the bus voltage U is collected multiple times BUS , obtain a second data set; Determine the mean value U of the second data set BUS-AVG2 Whether the second control condition is met; wherein the second control condition is: BUS-AVG2 >U OUTBUS , U OUTBUS is a preset second expected voltage; If so, collect the voltage U at the micro inverter end OUT , and based on the voltage U OUT and the second desired voltage U OUTBUS , and regulate the bus voltage U BUS The value of the second desired voltage U OUTBUS ; Based on the sampling frequency f3, the bus voltage U is collected multiple times BUS , obtain a third data set; Determine the mean value U of the third data set BUS-AVG3 Whether the third control condition is met; wherein the third control condition is: BUS-AVG3 >U PVBUS -U TH2 , U TH2 is a preset second voltage threshold; If yes, then collect the voltage U at the battery terminal 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.

[0007] By adopting the above technical solution, adjustments are first made at the photovoltaic module end so that the photovoltaic module outputs energy; then, adjustments are made at the micro-inverter end so that energy flows from the photovoltaic module to the micro-inverter; in addition, batteries are used to dynamically absorb system energy to improve energy utilization.

[0008] In a specific implementation scheme, after the battery is regulated to absorb the excess energy of the system through the battery, it also includes: Based on the sampling frequency f4, the bus voltage U is collected multiple times BUS , obtaining a fourth data set; Determine the mean value U of the fourth data set BUS-AVG4 Whether the fourth control condition is met; wherein the fourth control condition is: BUS-AVG4 <U PVBUS -U TH3 , U TH3 is a preset third voltage threshold; If yes, then collect the voltage U at the battery terminal BAT2 , and based on the voltage U BAT2 and the third desired voltage U BATBUS , secondary regulation is carried out at the battery end to replenish system energy through the battery.

[0009] By adopting the above technical solution, the bus voltage U BUS Real-time monitoring: when the energy output by the photovoltaic modules is insufficient, the battery needs to be discharged to supplement the system energy. Through secondary regulation at the battery end, the system energy can be flexibly allocated to maintain the stability of the bus voltage.

[0010] In a specific possible implementation, the energy control method further includes: adjusting the value of the sampling frequency f1 based on the first data set; Based on the second data set, adjusting the value of the sampling frequency f2; Based on the third data set, adjusting the value of the sampling frequency f3; Based on the fourth data set, adjusting the value of the sampling frequency f4; in, , , β is the set adjustment coefficient; When i=1, is the first data set U PV with U TH1 The standard deviation of the difference, f i is the sampling frequency f1, f adjust-i is the adjusted value of the sampling frequency f1; When i=2, is the second data set U BUS with UOUTBUS The standard deviation of the difference, f i is the sampling frequency f2, f adjust-i is the adjusted value of the sampling frequency f2; When i=3, is the third data set U BUS with U PVBUS -U TH2 The standard deviation of the difference, f i is the sampling frequency f3, f adjust-i is the adjusted value of the sampling frequency f3; When i=4, is the fourth data set U BUS with U PVBUS -U TH3 The standard deviation of the difference, f i is the sampling frequency f4, f adjust-i is the adjusted value of the sampling frequency f4.

[0011] By adopting the above technical solution, after the system is collected according to the initially set sampling frequency, the voltage fluctuation is judged based on the collected data, thereby adjusting the initial sampling frequency and reducing the impact of voltage fluctuations on the accuracy and reliability of system control.

[0012] In a specific implementation scheme, the second control strategy is used to control the system energy, specifically including: Collect the bus voltage U of the DC bus BUS and the battery terminal voltage U BAT3 ; Based on the 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.

[0013] By adopting the above technical solution, when the output of the photovoltaic module is very little or even basically no output, the battery discharge is directly used to provide energy for the system.

[0014] In a specific implementation scheme, 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 bus of the DC bus, 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 bus of the DC bus; 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.

[0015] In a specific implementation scheme, 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 intermediate 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, 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.

[0016] In a specific implementation scheme, 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 bus of the DC bus, one end of the switch tube Q6 is connected to the positive electrode of the battery and the intermediate node of the switch tube Q5, and the other end is connected to the negative electrode of the battery and the negative bus 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.

[0017] In a specific implementation scheme, 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.

[0018] In a second aspect, the present application provides a photovoltaic energy storage system, which adopts 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 a DC bus through the first voltage converter, the second voltage converter and the third voltage converter; when the photovoltaic energy storage system is in operation, the photovoltaic energy storage system energy control method as described in the first aspect or any one of the implementation schemes of the first aspect is adopted.

[0019] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages: The technical solution of the present 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 of unstable power of the micro-inverter caused by the influence of temperature, light conditions and shading on the output power of the photovoltaic module; in addition, batteries are added to the system to participate in the means of solving the fluctuation of the output power of the photovoltaic module, so as to better adapt to different electricity demands and make energy scheduling more flexible, which not only improves the overall energy utilization efficiency, but also enhances the reliability and stability of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of the structure of a photovoltaic energy storage system in an embodiment of the present application; Figure 2 It is a flow chart of the energy control method of the photovoltaic energy storage system in the embodiment of the present application; Figure 3 It is another flow chart of the energy control method of the photovoltaic energy storage system in the embodiment of the present application; Figure 4 It is a schematic diagram of the voltage, current and power changes at the micro inverter end when tracking the maximum power point of the photovoltaic module in an embodiment of the present application. DETAILED DESCRIPTION

[0021] In order to enable technicians in this field 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 in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this application, not all of the embodiments.

[0022] In the description of the embodiments of the present application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. The terms "include", "comprises", "has" and their variations all mean "including but not limited to", unless otherwise specifically emphasized.

[0023] The present application provides a method for controlling energy of a photovoltaic energy storage system. Figure 1 As shown, 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; wherein the photovoltaic component, the micro inverter and the battery are connected to the DC bus through the first voltage converter, the second voltage converter and the third voltage converter respectively.

[0024] Furthermore, 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 DC-DC type, and the rear end of the micro inverter is connected to a load or a power grid for converting 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, and a filter capacitor C4 is connected between the battery and the third voltage converter.

[0025] like Figure 2 As shown, the energy control method includes the following steps S1-S2: S1, based on the sampling frequency f1, collects the voltage U of the photovoltaic module terminal multiple times PV , and obtain the first data set.

[0026] S2, determining the mean value U of the first data set PV-AVG1 Whether the first control condition is met; wherein the first control condition is: PV-AVG1 >U TH1 , U TH1 is a preset first voltage threshold.

[0027] S3, if yes, then use the first control strategy to control the system energy; If not, the second control strategy is used to control the system energy.

[0028] It can be understood that the first control condition is used to determine whether the photovoltaic module has energy output. When the first control condition is met, it means that the photovoltaic module has energy output at this time, and the first control strategy is adopted accordingly; when the first control condition is not met, it means that the output voltage of the photovoltaic module is low or there is no energy output at this time, and the second control strategy is adopted accordingly. TH1 The value needs to be determined according to the number of panels connected to the photovoltaic module, and can be set to 0 or leave a certain margin and be set to a value slightly larger than 0. This application does not make specific limitations on this.

[0029] In one possible implementation, combining Figure 3 , step S3, the first control strategy is used to control the system energy, specifically including steps A1-A5: A1, collects the bus voltage U of the DC bus BUS ; and based on the mean value U PV-AVG1 and the preset first expected voltage U PVBUS , and regulate the bus voltage U BUS The value of the first desired voltage U PVBUS .

[0030] Through step A1, adjustments are first made at the photovoltaic module end to maximize the use of the output of the photovoltaic module to provide energy for the system.

[0031] In one possible implementation, continue to refer to Figure 1 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 bus of the DC bus, one end of the switch tube Q2 is connected to the positive electrode of the photovoltaic module and the middle node of the switch tube Q1, and the other end is connected to the negative electrode of the photovoltaic module and the negative bus of the DC bus; Furthermore, the first voltage converter further includes an energy storage inductor L1, and the energy storage inductor L1 is connected between the photovoltaic component and the switch tube Q1.

[0032] In this step, based on the mean value UPV-AVG1 and the preset first expected voltage U PVBUS , regulation is performed at the photovoltaic component end, specifically including steps A11-A12.

[0033] A11, based on the mean 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; A12: Based on the first duty cycle D1 and the second duty cycle D2, respectively, the switch tube Q1 and the switch tube Q2 are controlled to be on and off.

[0034] In a possible implementation manner, after step A12, respectively controlling the on / off of the switch tube Q1 and the switch tube Q2, further includes the following steps A13-A14: A13, monitors the bus voltage U BUS , and compare the bus voltage U BUS and the first desired voltage U PVBUS ; 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; If U BUS >U PVBUS , then reduce the value of the first duty cycle D1 and increase the value of the second duty cycle D2.

[0035] 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.

[0036] Therefore, through steps A13-A14, after controlling the duty cycle of the switch tube Q1 and the switch tube Q2, the bus voltage U is continuously monitored. BUS Check whether the adjustment is in place and adjust the duty cycle of the switching tube accordingly to eliminate system interference and maintain the stability of the bus voltage.

[0037] A2, based on the sampling frequency f2, repeatedly collects the bus voltage U BUS , obtain a second data set; A3, determine the mean value U of the second data set BUS-AVG2 Whether the second control condition is met; wherein the second control condition is: BUS-AVG2 >U OUTBUS , U OUTBUS is a preset second expected voltage.

[0038] Those skilled in the art can understand that if the second control condition is met, it means that the power generated by the photovoltaic module can flow to the micro-inverter at this time, and the energy can be regulated by the inverter.

[0039] A4, if yes, then collect the voltage U at the micro inverter end OUT , and based on the voltage U OUT and the second desired voltage U OUTBUS , and regulate the micro-inverter end so that the energy output by the photovoltaic module flows to the micro-inverter, and the bus voltage U BUS The value of the second desired voltage U OUTBUS .

[0040] Therefore, through steps A2-A4, after adjustment at the photovoltaic module end, adjustment is performed at the micro inverter end, so that energy flows from the photovoltaic module to the micro inverter to provide energy for the load.

[0041] In one possible implementation, continue to refer to Figure 1 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 intermediate 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; Furthermore, the second voltage converter further includes an energy storage inductor L2, and the energy storage inductor L2 is connected between the micro inverter and the switch tube Q3; the voltage U OUT , is the voltage value of the intermediate node between the micro inverter and the second voltage converter.

[0042] In step A4, based on the voltage U OUT and the second desired voltage U OUTBUS , and control is performed at the micro inverter end, specifically including the following steps A41-A42: A41, 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; A42, based on the third duty cycle D3 and the fourth duty cycle D4, respectively controlling the on / off of the switch tube Q3 and the switch tube Q4.

[0043] In a possible implementation manner, after step A42, respectively controlling the on / off of the switch tube Q3 and the switch tube Q4, further includes the following steps A43-A44: A43, monitors the bus voltage U BUS , and compare the bus voltage U BUS and the second desired voltage U OUTBUS ; 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; If U BUS >U OUTBUS , then reduce the value of the third duty cycle D3 and increase the value of the fourth duty cycle D4.

[0044] 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.

[0045] Therefore, through steps A53-A54, after controlling the duty cycle of the switch tubes Q3 and Q4, the bus voltage U is continuously monitored. BUS Check whether the adjustment is in place and adjust the duty cycle of the switching tube accordingly to eliminate system interference and maintain the stability of the bus voltage.

[0046] A5, based on the sampling frequency f3, the bus voltage U is collected multiple times BUS , obtain a third data set; A6, determining the mean value U of the third data set BUS-AVG3 Whether the third control condition is met; wherein the third control condition is: BUS-AVG3 >U PVBUS -U TH2 , U TH2 is the preset second voltage threshold, U TH2 For example, 2V.

[0047] It is understandable that the third control condition is used to determine whether the system has excess energy to charge the battery; when the energy flows to the micro-inverter in step A4, the micro-inverter starts to track the maximum power point of the photovoltaic module, which leads to the voltage U OUT and the voltage U at the PV module end PV Reduce, bus voltage U BUS will also decrease, in order to maintain the bus voltage U BUS When the target value is reached, the duty cycle corresponding to the switch tube Q1 in the first voltage converter and the switch tube Q3 in the second voltage converter will increase until the micro inverter tracks the maximum power point.

[0048] like Figure 4 As shown in the figure, when the micro-inverter is tracking the maximum power point of the photovoltaic module, the voltage U at the micro-inverter end is OUT , current and power meet Figure 4 The relationship is shown in the figure. In the figure, the blue line is the current curve and the orange line is the power curve.

[0049] A7, if yes, then collect the voltage U at the battery end BAT1 , and based on the voltage U BAT1 and the preset third expected voltage U BATBUS , and regulates the battery end, absorbing the excess energy of the system through the battery, and the bus voltage U BUS The value of the third desired voltage U BATBUS .

[0050] Therefore, step A7 is to allow the surplus energy generated by the photovoltaic module to flow to the battery, charge the battery, and improve energy utilization.

[0051] In one possible implementation, continue to refer to Figure 1 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 bus 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 bus of the DC bus; Furthermore, the third voltage converter also includes an energy storage inductor L3, and the energy storage inductor L3 is connected between the battery and the switch tube Q5.

[0052] In step A7, based on the voltage U BAT1 and the preset third expected voltage U BATBUS , regulation is performed at the battery end, specifically including the following steps A71-A72: A71, 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; A72, based on the fifth duty cycle D5 and the sixth duty cycle D6, respectively controlling the on-off of the switch tube Q5 and the switch tube Q6.

[0053] In a possible implementation manner, after step A72, respectively controlling the on / off of the switch tube Q5 and the switch tube Q6, further includes the following steps A73-A74: A73, monitors the bus voltage UBUS , and compare the bus voltage U BUS and the third desired voltage U BATBUS ; 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; If U BUS >U BATBUS , then reduce the value of the fifth duty cycle D5 and increase the value of the sixth duty cycle D6.

[0054] Those skilled in the art will appreciate that when adjusting the values ​​of D5 and D6, it is also necessary to ensure that D5+D6=1.

[0055] Therefore, through steps A73-A74, after controlling the duty cycle of switch tube Q5 and switch tube Q6, the bus voltage U is continuously monitored. BUS Check whether the adjustment is in place and adjust the duty cycle of the switching tube accordingly to eliminate system interference and maintain the stability of the bus voltage.

[0056] In a possible implementation, step A7, after performing regulation at the battery end and absorbing excess energy of the system through the battery, further includes the following steps A8-A10: A8, based on the sampling frequency f4, repeatedly collects the bus voltage U BUS , and obtain the fourth data set.

[0057] A9, determining the mean value U of the fourth data set BUS-AVG4 Whether the fourth control condition is met; wherein the fourth control condition is: BUS-AVG4 <U PVBUS -U TH3 , U TH3 is the preset third voltage threshold, U TH3 For example, 4V.

[0058] A10, if yes, then collect the voltage U at the battery terminal BAT2 , and based on the voltage U BAT2 and the third desired voltage U BATBUS , perform secondary regulation at the battery end, supplement the system energy through the battery, and increase the bus voltage U BUS The value of the third desired voltage U BATBUS .

[0059] Therefore, by adjusting the bus voltage U BUSReal-time monitoring: when the fourth control condition is met, it means that the energy output by the photovoltaic module is insufficient and the battery needs to be discharged to supplement the system energy. Through secondary control at the battery end, the system energy can be flexibly allocated to maintain the stability of the bus voltage and the output power of the photovoltaic module.

[0060] In a possible implementation manner, in step A10, based on the voltage U BAT2 and the third desired voltage U BATBUS , secondary regulation is performed at the battery end, specifically including the following steps A101-A102: A101, 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; 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 switch tube Q5 and the switch tube Q6.

[0061] Those skilled in the art will appreciate that when the fourth regulation condition is not met, there is no need to control the battery discharge.

[0062] In a possible implementation manner, after obtaining the first data set in step S1, the method further includes: Based on the first data set, adjusting the value of the sampling frequency f1; After obtaining the second data set in step A2, the method further includes: adjusting the value of the sampling frequency f2 based on the second data set; After obtaining the third data set in step A5, the method further includes: adjusting the value of the sampling frequency f3 based on the third data set; After obtaining the fourth data set in step A8, the method further includes: adjusting the value of the sampling frequency f4 based on the fourth data set; in, , , β is the set adjustment coefficient; Characterize the degree of voltage fluctuation; When i=1, is the first data set U PV with U TH1 The standard deviation of the difference, f i is the sampling frequency f1, f adjust-i is the adjusted value of the sampling frequency f1; When i=2, is the second data set U BUS with UOUTBUS The standard deviation of the difference, f i is the sampling frequency f2, f adjust-i is the adjusted value of the sampling frequency f2; When i=3, is the third data set U BUS with U PVBUS -U TH2 The standard deviation of the difference, f i is the sampling frequency f3, f adjust-i is the adjusted value of the sampling frequency f3; When i=4, is the fourth data set U BUS with U PVBUS -U TH3 The standard deviation of the difference, f i is the sampling frequency f4, f adjust-i is the adjusted value of the sampling frequency f4.

[0063] Preferably, during initial setting, the sampling frequencies f1, f2, f3, and f4 are the same, which are all 20 khz.

[0064] Therefore, after collecting data from the system according to the initially set sampling frequency, the voltage fluctuation is judged based on the collected data, so as to adjust the initial sampling frequency and reduce the impact of voltage fluctuation on the accuracy and reliability of system control.

[0065] In one possible implementation, combining Figure 3 In the above step S3, the second control strategy is used to control the system energy, which specifically includes the following steps B1-B3: B1, collects the bus voltage U of the DC bus BUS and the battery terminal voltage U BAT3 ; B2, based on the voltage U BAT3 and the preset DC bus third expected voltage U BATBUS , and regulates at the battery end, providing energy to the system through battery discharge, and the bus voltage U BUS The value of the third desired voltage U BATBUS .

[0066] Specifically, in step B2, based on the voltage U BAT3 and the preset DC bus third expected voltage U BATBUS , regulation is performed at the battery end, specifically including the following steps B21-B22: B21, based on the voltage U BAT3 and the preset DC bus third expected voltage U BATBUS, calculate the values ​​of the seventh duty cycle D7 and the eighth duty cycle D8; wherein, U BAT3 =U BATBUS *(1-D7); D8=1-D7; B22, based on the values ​​of the seventh duty cycle D7 and the eighth duty cycle D8, respectively controlling the on / off of the switch tube Q5 and the switch tube Q6.

[0067] Therefore, when the output of the photovoltaic module is very little or even almost non-existent, the battery discharge is directly used to provide energy for the system through steps B1-B2.

[0068] That is to say, the main idea of ​​the present application is: first, when the first control condition is adopted and it is judged that the photovoltaic module has output, the bus voltage is regulated to the first desired voltage U by controlling the output of the photovoltaic module. PVBUS Afterwards, when the second control condition is adopted and it is determined that the energy output by the photovoltaic module can flow to the micro-inverter to supply power to the load, the bus voltage is regulated to the second desired voltage U by regulating the micro-inverter end. OUTBUS , so that the photovoltaic module works at the maximum power point; then, when the third control condition is adopted and it is judged that the energy output by the photovoltaic module is too much, the bus voltage is regulated to the third desired voltage U by regulating the battery end and using the battery to absorb the excess energy of the system BATBUS Finally, when the fourth control condition is adopted and it is determined that the energy output by the photovoltaic module is insufficient, the bus voltage is stabilized to the third desired voltage U again by regulating the battery end and using the battery to supplement the system energy. BATBUS .

[0069] For several preset expected voltage values, their magnitude relationship is: the first expected voltage U PVBUS >The second expected voltage U OUTBUS >The third expected voltage U BATBUS .

[0070] Therefore, the technical solution of the present 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 of unstable power of the micro-inverter caused by the influence of temperature, light conditions and shading on the output power of the photovoltaic module; in addition, adding batteries to the system not only participates in the means of solving the fluctuation of the output power of the photovoltaic module, but also better adapts to different electricity demands and makes energy scheduling more flexible; for example, when the photovoltaic module has sufficient energy, the excess energy is stored in the battery to ensure that the photovoltaic module operates at the maximum power point and improves the power generation efficiency; when the light is insufficient or at night, the electric energy is released to replenish the system energy, which not only improves the overall energy utilization efficiency, but also enhances the reliability and stability of the entire system.

[0071] It can be understood by those skilled in the art that the voltage at the photovoltaic module end described in this embodiment is the voltage of the intermediate node between the first voltage converter and the photovoltaic module; the voltage at the micro inverter end is the voltage of the intermediate node between the micro inverter and the second voltage converter; the voltage at the battery end is the voltage of the intermediate node between the battery and the third voltage converter.

[0072] An embodiment of the present application provides a photovoltaic energy storage system, comprising 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; when the photovoltaic energy storage system is in operation, the above-mentioned photovoltaic energy storage system energy control method is adopted.

[0073] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in 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 comprises 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 control method comprises: Based on the sampling frequency f1, the voltage U at the photovoltaic module end is collected multiple times PV , obtain a first data set; Determine the mean value U of the first data set PV-AVG1 Whether the first control condition is met; wherein the first control condition is: PV-AVG1 >U TH1 , U TH1 is a preset first voltage threshold; If so, the first control strategy is used to control the system energy; If not, the second control strategy is used to control the system energy.

2. The photovoltaic energy storage system energy control method according to claim 1, characterized in that: The adopting the first control strategy to control the system specifically includes: Collect the bus voltage U of the DC bus BUS ; and based on the mean value U PV-AVG1 and the preset first expected voltage U PVBUS , and regulate the bus voltage U BUS The value of the first desired voltage U PVBUS ; Based on the sampling frequency f2, the bus voltage U is collected multiple times BUS , obtain a second data set; Determine the mean value U of the second data set BUS-AVG2 Whether the second control condition is met; wherein the second control condition is: BUS-AVG2 >U OUTBUS , U OUTBUS is a preset second expected voltage; If so, collect the voltage U at the micro inverter end OUT , and based on the voltage U OUT and the second desired voltage U OUTBUS , and regulate the bus voltage U BUS The value of the second desired voltage U OUTBUS ; Based on the sampling frequency f3, the bus voltage U is collected multiple times BUS , obtain a third data set; Determine the mean value U of the third data set BUS-AVG3 Whether the third control condition is met; wherein the third control condition is: BUS-AVG3 >U PVBUS -U TH2 , U TH2 is a preset second voltage threshold; If yes, then collect the voltage U at the battery terminal 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.

3. The photovoltaic energy storage system energy control method according to claim 2, characterized in that: 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 multiple times BUS , obtaining a fourth data set; Determine the mean value U of the fourth data set BUS-AVG4 Whether the fourth control condition is met; wherein the fourth control condition is: BUS-AVG4 <U PVBUS -U TH3 , U TH3 is a preset third voltage threshold; If yes, then collect the voltage U at the battery terminal BAT2 , and based on the voltage U BAT2 and the third desired voltage U BATBUS , secondary regulation is carried out at the battery end to replenish system energy through the battery.

4. The method for regulating energy of a photovoltaic energy storage system according to claim 3, characterized in that: Also includes: Based on the first data set, adjusting the value of the sampling frequency f1; Based on the second data set, adjusting the value of the sampling frequency f2; Based on the third data set, adjusting the value of the sampling frequency f3; Based on the fourth data set, adjusting the value of the sampling frequency f4; in, , , β is the set adjustment coefficient; When i=1, is the first data set U PV with U TH1 The standard deviation of the difference, f i is the sampling frequency f1, f adjust-i is the adjusted value of the sampling frequency f1; When i=2, is the second data set U BUS with U OUTBUS The standard deviation of the difference, f i is the sampling frequency f2, f adjust-i is the adjusted value of the sampling frequency f2; When i=3, is the third data set U BUS with U PVBUS -U TH2 The standard deviation of the difference, f i is the sampling frequency f3, f adjust-i is the adjusted value of the sampling frequency f3; When i=4, is the fourth data set U BUS with U PVBUS -U TH3 The standard deviation of the difference, f i is the sampling frequency f4, f adjust-i is the adjusted value of the sampling frequency f4.

5. The photovoltaic energy storage system energy control method according to claim 1, characterized in that: The second control strategy is used to control the system energy, including: Collect the bus voltage U of the DC bus BUS and the battery terminal voltage U BAT3 ; Based on the 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.

6. The energy control method of the photovoltaic energy storage system according to claim 2, 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.

7. The photovoltaic energy storage system energy control method according to claim 2, 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, 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.

8. The photovoltaic energy storage system energy control method according to claim 2, 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.

9. The photovoltaic energy storage system energy control method according to claim 8, 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.

10. 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 9 is adopted.

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