Off-grid inverter control system based on photovoltaic energy storage system

Abstract

The invention relates to the field of new energy, in particular to an off-grid inverter control system based on a photovoltaic energy storage system, which comprises a photovoltaic power generation module, an energy storage module, an inversion module, a data acquisition module and a control module, the energy storage module is used for storing electric energy converted by the photovoltaic power generation module, the inversion module is used for converting direct current into alternating current and outputting the alternating current to each power utilization unit, the data acquisition module is used for acquiring load requirements of each power utilization unit, and the control module is used for generating a requirement index. And the input source of the inversion module is controlled according to the demand index. According to the scheme, the demand indexes of the inverter module for the photovoltaic power generation module and the energy storage module are acquired, so that the current suitability degree of the inverter module and the two power sources can be judged according to the demand indexes, and the power sources of the inverter module can be flexibly adjusted according to actual conditions.

Description

Technical Field

[0001] The present invention relates to the field of new energy, and in particular to an off-grid inverter control system based on a photovoltaic energy storage system. Background Art

[0002] With the growth of global energy demand and the enhancement of environmental protection awareness, photovoltaic energy storage systems have received widespread attention as a way to utilize clean and renewable energy. Photovoltaic power generation systems provide power support for homes, businesses and remote areas by converting solar energy into electrical energy. In areas lacking grid coverage, off-grid photovoltaic energy storage systems can operate independently to provide users with a reliable power supply.

[0003] For example, the prior art disclosed in CN102684218B discloses a non-isolated photovoltaic grid-connected inverter, which belongs to the technical field of power electronic converters. The non-isolated photovoltaic grid-connected inverter described in the present invention is composed of an input capacitor branch, a full-bridge switch unit, and a grid-in filter branch, wherein the full-bridge switch circuit is divided into a six-switch full-bridge switch circuit and a seven-switch full-bridge switch circuit according to the number of switches.

[0004] Another typical example is a photovoltaic off-grid energy storage inverter disclosed in the prior art of CN108899926A, comprising: a photovoltaic component, an MPPT controller connected to the photovoltaic component, a bidirectional converter connected to the power grid at one end, an energy storage component and an inverter component; the other end of the bidirectional converter, the output end of the MPPT controller, the energy storage component, and the input end of the inverter component are interconnected; the energy storage inverter also includes a control component connected to the MPPT controller, the bidirectional converter and the inverter component, the control component is used to determine whether the photovoltaic component is operating at the maximum power point, if the photovoltaic component is not operating at the maximum power point, the control component controls the MPPT controller to make the energy storage inverter operate at the maximum power point.

[0005] Let's take a look at an off-grid photovoltaic inverter disclosed in the prior art such as CN116799863B, which includes: a DC-DC circuit, a first generating circuit and a grid-connected photovoltaic inverter; the input end of the DC-DC circuit is connected to the photovoltaic power generation system to convert the first direct current output by the photovoltaic power generation system into a second direct current; the input end of the first generating circuit is connected to the output end of the DC-DC circuit to generate an alternating voltage signal and a second voltage simulation signal based on the second direct current; the first input end of the grid-connected photovoltaic inverter is connected to the first output end of the first generating circuit; the second input end of the grid-connected photovoltaic inverter is connected to the photovoltaic power generation system; the output end of the grid-connected photovoltaic inverter is connected to the power grid; when the grid-connected photovoltaic inverter detects the alternating voltage signal and / or the second voltage simulation signal, it inverts the first direct current output by the photovoltaic power generation system into an alternating voltage and outputs it to the power grid.

[0006] At present, the existing photovoltaic energy storage system usually uses an inverter to output the energy stored in the battery or directly outputs the energy converted by the solar panel through the inverter. The usage mode is relatively simple and cannot be flexibly adjusted according to load demand. In order to solve the common problems in this field, the present invention is made. Summary of the invention

[0007] The purpose of the present invention is to propose an off-grid inverter control system based on a photovoltaic energy storage system in view of the current deficiencies.

[0008] In order to overcome the shortcomings of the prior art, the present invention adopts the following technical solutions: An off-grid inverter control system based on a photovoltaic energy storage system includes a photovoltaic power generation module, an energy storage module, an inverter module, a data acquisition module and a control module, wherein the photovoltaic power generation module is used to collect solar energy and convert the solar energy into direct current, the energy storage module is used to store the electric energy converted by the photovoltaic power generation module, the inverter module is used to convert direct current into alternating current and output it to each power user, the data acquisition module is used to collect the load demand of each power user, and the control module is used to generate a demand index of the inverter module for the photovoltaic power generation module and the energy storage module according to the data collected by the data acquisition module, and control the input source of the inverter module according to the demand index.

[0009] Furthermore, the photovoltaic power generation module includes a plurality of solar panels and a maximum power point tracking controller, wherein the solar panels are used to collect solar energy and convert the solar energy into direct current, and the maximum power point tracking controller is used to adjust the output voltage of the solar panels so that the solar panels always operate at the maximum power point.

[0010] Furthermore, the energy storage module includes a battery pack, which is used to store the electric energy obtained by the photovoltaic power generation module. The inverter module includes a conversion unit, a filtering unit, a digital signal processor and a PWM controller. The conversion unit is used to convert direct current into alternating current. The PWM controller is used to adjust the frequency, amplitude and phase of the alternating current obtained by the conversion unit according to load requirements. The filtering unit is used to filter the adjusted alternating current. The digital signal processor is used to adjust the output of the filtered alternating current according to load requirements.

[0011] Furthermore, the data acquisition module includes a power generation information acquisition module, an energy storage information acquisition module and a load information acquisition module. The power generation information acquisition module is used to collect various data generated by the photovoltaic power generation module during the power generation process, the energy storage information acquisition module is used to collect various data of the energy storage module, and the load information acquisition module is used to exchange signals with each power consumption unit and obtain the load demand data of each power consumption unit.

[0012] Furthermore, the control module includes a data sorting unit, a calculation unit and a command generating unit. The data sorting unit is used to sort, classify and reduce noise of various data collected by the data acquisition module. The calculation unit is used to calculate the demand index according to the sorted data. The command generating unit is used to generate a control command according to the demand index. The control command is used to control the photovoltaic power generation module, energy storage module and inverter module.

[0013] Furthermore, the workflow of the system includes the following steps: S1, the photovoltaic power generation module collects solar energy and converts the collected solar energy into electrical energy.

[0014] S2, the energy storage module stores the electric energy obtained by the photovoltaic power generation module.

[0015] S3, the data acquisition module collects various data of the photovoltaic power generation module, the energy storage module and each electricity user.

[0016] S4, the control module calculates the demand index of the inverter module for the photovoltaic power generation module and the demand index of the inverter module for the energy storage module according to the collected data of the data acquisition module.

[0017] S5, the control module connects the input end of the inverter module to the photovoltaic power generation module or the energy storage module according to the demand index.

[0018] S6, the inverter module converts the DC power into the AC power that meets the requirements according to the load demand data and sends it to each power consumption unit.

[0019] Furthermore, the inverter module converts DC power into AC power that meets the requirements, including the following steps: S61, receiving load demand data collected by the data collection unit.

[0020] S62, the conversion unit converts the direct current received from the input end of the inverter module into alternating current.

[0021] S63, the PWM controller adjusts the frequency, amplitude and phase of the converted AC power according to the load demand data.

[0022] S64, the filtering unit filters the alternating current adjusted by the PWM controller.

[0023] S65, the digital signal processor adjusts the output of the filtered AC power according to the load demand data and sends it to each power consumption unit.

[0024] The beneficial effects achieved by the present invention are: 1. By obtaining the demand indicators of the inverter module for the photovoltaic power generation module and the energy storage module, it is helpful to judge the current suitability of the inverter module and the two power sources according to the demand indicators, and it is helpful to flexibly adjust the power source of the inverter module according to actual conditions, thereby improving the flexibility of the system.

[0025] 2. By obtaining the time-varying function of the average light intensity and the time-varying function of the average temperature, it is helpful to obtain the demand index of the inverter module for the photovoltaic power generation module according to the future conditions of light intensity and temperature, taking into account the future power generation conditions and being foresighted. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention can be further understood from the following description in conjunction with the accompanying drawings. The components in the figures are not necessarily drawn to scale, but the emphasis is placed on illustrating the principles of the embodiments. In different views, the same reference numerals designate the same parts.

[0027] Figure 1 It is a schematic diagram of the structure of the present invention.

[0028] Figure 2 It is the work flow chart of the present invention.

[0029] Figure 3 The present invention is a flow chart of the inverter module converting direct current into alternating current that meets the requirements.

[0030] Figure 4 It is a graph showing the relationship between the demand index, the rated power of the energy storage module, and the current remaining power percentage of the battery pack (presented in decimal form in the figure). DETAILED DESCRIPTION

[0031] The following is an explanation of the embodiments of the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. In addition, the drawings of the present invention are only simple schematic illustrations and are not depicted according to actual sizes. It is stated in advance. The following embodiments will further explain the relevant technical contents of the present invention in detail, but the disclosed contents are not intended to limit the scope of protection of the present invention.

[0032] Embodiment 1: According to Figure 1 , Figure 2 , Figure 3 and Figure 4 This embodiment provides an off-grid inverter control system based on a photovoltaic energy storage system, including a photovoltaic power generation module, an energy storage module, an inverter module, a data acquisition module and a control module. The photovoltaic power generation module is used to collect solar energy and convert the solar energy into direct current. The energy storage module is used to store the electric energy converted by the photovoltaic power generation module. The inverter module is used to convert direct current into alternating current and output it to each power consumption unit. The data acquisition module is used to collect the load demand of each power consumption unit. The control module is used to generate a demand index of the inverter module for the photovoltaic power generation module and the energy storage module according to the data collected by the data acquisition module, and control the input source of the inverter module according to the demand index.

[0033] Specifically, the demand index is used to characterize the suitability of the inverter module and the power source (photovoltaic power generation module or energy storage module) at the current moment. The larger the demand index, the higher the suitability.

[0034] Furthermore, the photovoltaic power generation module includes a plurality of solar panels and a maximum power point tracking controller, wherein the solar panels are used to collect solar energy and convert the solar energy into direct current, and the maximum power point tracking controller is used to adjust the output voltage of the solar panels so that the solar panels always operate at the maximum power point.

[0035] Specifically, the maximum power point tracking controller adjusts the output voltage of the solar panel through the maximum power point tracking technology. The maximum power point tracking technology belongs to the existing technology and will not be described in detail here.

[0036] Furthermore, the energy storage module includes a battery pack, which is used to store the electric energy obtained by the photovoltaic power generation module. The inverter module includes a conversion unit, a filtering unit, a digital signal processor and a PWM controller. The conversion unit is used to convert direct current into alternating current. The PWM controller is used to adjust the frequency, amplitude and phase of the alternating current obtained by the conversion unit according to load requirements. The filtering unit is used to filter the adjusted alternating current. The digital signal processor is used to adjust the output of the filtered alternating current according to load requirements.

[0037] Specifically, the digital signal processor adjusts the output of the filtered alternating current according to a pre-set communication protocol to meet the load requirements of each power-consuming unit.

[0038] Furthermore, the data acquisition module includes a power generation information acquisition module, an energy storage information acquisition module and a load information acquisition module. The power generation information acquisition module is used to collect various data generated by the photovoltaic power generation module during the power generation process, the energy storage information acquisition module is used to collect various data of the energy storage module, and the load information acquisition module is used to exchange signals with each power consumption unit and obtain the load demand data of each power consumption unit.

[0039] Furthermore, the control module includes a data sorting unit, a calculation unit and a command generating unit. The data sorting unit is used to sort, classify and reduce noise of various data collected by the data acquisition module. The calculation unit is used to calculate the demand index according to the sorted data. The command generating unit is used to generate a control command according to the demand index. The control command is used to control the photovoltaic power generation module, energy storage module and inverter module.

[0040] Furthermore, the workflow of the system includes the following steps: S1, the photovoltaic power generation module collects solar energy and converts the collected solar energy into electrical energy; S2, the energy storage module stores the electric energy obtained by the photovoltaic power generation module; S3, the data acquisition module collects various data of the photovoltaic power generation module, the energy storage module and each electricity user; S4, the control module calculates the demand index of the inverter module for the photovoltaic power generation module and the demand index of the inverter module for the energy storage module according to the collected data of the data collection module; Specifically, the demand index can be calculated according to the following method: The demand index of the inverter module for the photovoltaic power generation module can be calculated according to the following formula: in, is the demand index of the inverter module for the photovoltaic power generation module, is the average light intensity detected by each solar panel, The rated power of the solar panel. is the function of average light intensity changing with time, which can be obtained by linear fitting the past data of the day. is the average temperature detected by each solar panel, is the function of average temperature changing with time, which can be obtained by linear fitting the past data of the day. is the temperature coefficient, which can be obtained by testing the photovoltaic power generation module under test conditions, where the test environment is 25 degrees Celsius. is the temperature value when testing under the test environment, PP is the power value detected when testing under the test environment, and T is the reference temperature, which can be set to a normal temperature value (generally 25 degrees Celsius).

[0041] Specifically, t may be set to the same value as the control period of the control module, and the control period is generally set to 60 minutes or 30 minutes.

[0042] The following is the procedure for calculating the inverter module's demand index for the photovoltaic power generation module: def calculate_xqzb(F1_t, F2_t, W1, P1, T1, T, PP, TT): """ Calculate the demand index XQZB1 of the inverter module for the photovoltaic power generation module.

[0043] parameter: F1_t (float): Average light intensity over time.

[0044] F2_t (float): Average temperature as a function of time.

[0045] W1 (float): Average light intensity.

[0046] P1 (float): The rated power of the photovoltaic panel.

[0047] T1 (float): Average temperature.

[0048] T (float): Current detected temperature.

[0049] PP (float): The power detected under test.

[0050] TT (float): Test environment temperature.

[0051] return: float: demand index XQZB1.

[0052] """ # Temperature coefficient calculation alpha = (PP - P1) / (P1 * (T - TT)) # Demand indicator XQZB1 calculation XQZB1 = (F1_t / W1) * P1 * (1 - (F2_t / T1) * alpha * (T1 - T)) return XQZB1 # Example parameters F1_t = 0.8 # Example value F2_t = 0.9 # Example value W1 = 1000 # Average light intensity, unit: W / m² P1 = 250 # Rated power of photovoltaic panel, unit: W T1 = 25 # Average temperature, unit: °C T = 30 # Current detection temperature, unit: ℃ PP = 240 # Power detected in the test environment, unit: W TT = 25 # Test environment temperature, unit: ℃ # Calculate demand indicators XQZB1 = calculate_xqzb(F1_t, F2_t, W1, P1, T1, T, PP, TT) print(f"Calculated demand index XQZB1: {XQZB1:.2f}") The demand index of the inverter module for the energy storage module can be calculated according to the following formula: in, is the demand index of the inverter module for the energy storage module, is the rated power of the energy storage module, A is the remaining power parameter of the energy storage module, tem is the battery temperature threshold, and the battery temperature threshold is set by technicians in this field according to the energy loss of the battery at different temperatures and the temperature value when the energy loss suddenly changes. TEM is the current average temperature of the battery pack, a is the current remaining power percentage of the battery pack, and e is a natural constant.

[0053] like Figure 4 As shown, Figure 4 Assumption When the current average temperature of the battery pack is equal to the battery temperature threshold, the relationship between the demand indicator and the rated power of the energy storage module and the current remaining power percentage of the battery pack (presented in decimal form in the figure) is shown.

[0054] S5, the control module connects the input end of the inverter module to the photovoltaic power generation module or the energy storage module according to the demand index; Specifically, when the inverter module has a larger demand index for the photovoltaic power generation module, the input end of the inverter module is connected to the photovoltaic power generation module; when the inverter module has a larger demand index for the energy storage module, the input end of the inverter module is connected to the energy storage module.

[0055] S6, the inverter module converts the DC power into the AC power that meets the requirements according to the load demand data and sends it to each power consumption unit.

[0056] Furthermore, the inverter module converts DC power into AC power that meets the requirements, including the following steps: S61, receiving load demand data collected by a data collection unit; S62, the conversion unit converts the direct current received from the input end of the inverter module into alternating current; S63, the PWM controller adjusts the frequency, amplitude and phase of the converted AC power according to the load demand data; S64, the filtering unit filters the alternating current adjusted by the PWM controller; S65, the digital signal processor adjusts the output of the filtered AC power according to the load demand data and sends it to each power consumption unit.

[0057] The beneficial effects of this solution are: 1. By obtaining the demand indicators of the inverter module for the photovoltaic power generation module and the energy storage module, it is helpful to judge the current suitability of the inverter module and these two power sources based on the demand indicators, and it is helpful to flexibly adjust the power source of the inverter module according to actual conditions, thereby improving the flexibility of the system.

[0058] 2. By obtaining the time-varying function of the average light intensity and the time-varying function of the average temperature, it is helpful to obtain the demand index of the inverter module for the photovoltaic power generation module according to the future conditions of light intensity and temperature, taking into account the future power generation conditions and being foresighted.

[0059] Embodiment 2: This embodiment should be understood as including all the features of any of the foregoing embodiments, and further improved thereon, and also includes a preferred method for obtaining a function of average light intensity varying with time, the method filters the original data collected by the data acquisition module in the following manner, and re-obtains the average light intensity at different times based on the filtered data, and obtains the function of average light intensity varying with time based on the re-obtained average light intensity.

[0060] Specifically, the power generation information collection module includes a plurality of light sensors, the light sensors are used to detect light intensity, and the raw data is the light intensity detected by each light sensor; The above method calculates the deviation index of each raw data of each light sensor through the following formula. The following takes a certain raw data of a light sensor as an example: in, is the deviation index of the original data, e is a natural constant, is the light intensity detected by the light sensor at the current moment, V is the average light intensity corresponding to the moment, B is the number of light sensors adjacent to the light sensor, is the illumination deviation parameter between the illumination sensor and its adjacent b-th illumination sensor at the moment, case 1 is that the difference in illumination intensity detected by the illumination sensor and its adjacent b-th illumination sensor is less than or equal to the illumination difference threshold, case 2 is that the difference in illumination intensity detected by the illumination sensor and its adjacent b-th illumination sensor is greater than the illumination difference threshold, and the illumination difference threshold is set by those skilled in the art with reference to the difference in illumination intensity between the cloudy part and the cloudless part on the solar panel at noon, is the light intensity detected by the adjacent b-th light sensor at the current moment, and max() is the maximum value function.

[0061] Specifically, the larger the deviation index is, the greater the possibility that the data is erroneous. The above screening method is to eliminate the data whose deviation index is greater than the deviation index threshold, and then calculate the average light intensity based on the remaining original data.

[0062] Specifically, the deviation index threshold is set by those skilled in the art between 1.5 and 3 according to the required accuracy. The greater the required accuracy, the greater the value of the deviation index threshold.

[0063] The beneficial effects of this embodiment are as follows: by setting the deviation index, it is helpful to judge the degree of deviation between each original data and the actual situation, so as to screen out the values ​​with greater possibility of error in the original data; by recalculating the average light intensity, it is helpful to improve the fit between the demand index and the actual demand situation.

[0064] The above disclosed contents are only preferred feasible embodiments of the present invention, and do not limit the protection scope of the present invention. Therefore, all equivalent technical changes made by using the contents of the present invention specification and drawings are included in the protection scope of the present invention. In addition, the elements therein can be updated with the development of technology. The above units are only examples. Those skilled in the art can use corresponding units according to different designs according to actual needs when implementing this solution.

Claims

1. An off-grid inverter control system based on a photovoltaic energy storage system, characterized in that: It includes a photovoltaic power generation module, an energy storage module, an inverter module, a data acquisition module and a control module. The photovoltaic power generation module is used to collect solar energy and convert it into direct current. The energy storage module is used to store the electric energy converted by the photovoltaic power generation module. The inverter module is used to convert direct current into alternating current and output it to each power-consuming unit. The data acquisition module is used to collect the load demand of each power-consuming unit. The control module is used to generate the demand index of the inverter module for the photovoltaic power generation module and the energy storage module according to the data collected by the data acquisition module, and control the input source of the inverter module according to the demand index.

2. According to claim 1, an off-grid inverter control system based on a photovoltaic energy storage system is characterized in that: The photovoltaic power generation module includes a plurality of solar panels and a maximum power point tracking controller. The solar panels are used to collect solar energy and convert it into direct current. The maximum power point tracking controller is used to adjust the output voltage of the solar panels so that the solar panels always operate at the maximum power point.

3. The off-grid inverter control system based on the photovoltaic energy storage system according to claim 2, characterized in that: The energy storage module includes a battery pack, which is used to store the electric energy obtained by the photovoltaic power generation module. The inverter module includes a conversion unit, a filtering unit, a digital signal processor and a PWM controller. The conversion unit is used to convert direct current into alternating current. The PWM controller is used to adjust the frequency, amplitude and phase of the alternating current obtained by the conversion unit according to load requirements. The filtering unit is used to filter the adjusted alternating current. The digital signal processor is used to adjust the output of the filtered alternating current according to load requirements.

4. The off-grid inverter control system based on the photovoltaic energy storage system according to claim 3 is characterized in that: The data acquisition module includes a power generation information acquisition module, an energy storage information acquisition module and a load information acquisition module. The power generation information acquisition module is used to collect various data generated by the photovoltaic power generation module during the power generation process, the energy storage information acquisition module is used to collect various data of the energy storage module, and the load information acquisition module is used to exchange signals with each power consumption unit and obtain the load demand data of each power consumption unit.

5. The off-grid inverter control system based on the photovoltaic energy storage system according to claim 4, characterized in that: The control module includes a data sorting unit, a calculation unit and a command generating unit. The data sorting unit is used to sort, classify and reduce noise of various data collected by the data acquisition module. The calculation unit is used to calculate demand indicators based on the sorted data. The command generating unit is used to generate control commands based on the demand indicators. The control commands are used to control the photovoltaic power generation module, energy storage module and inverter module.

6. The off-grid inverter control system based on the photovoltaic energy storage system according to claim 5, characterized in that: The workflow of the system includes the following steps: S1, the photovoltaic power generation module collects solar energy and converts the collected solar energy into electrical energy; S2, the energy storage module stores the electric energy obtained by the photovoltaic power generation module; S3, the data acquisition module collects various data of the photovoltaic power generation module, the energy storage module and each electricity user; S4, the control module calculates the demand index of the inverter module for the photovoltaic power generation module and the demand index of the inverter module for the energy storage module according to the collected data of the data collection module; S5, the control module connects the input end of the inverter module to the photovoltaic power generation module or the energy storage module according to the demand index; S6, the inverter module converts the DC power into the AC power that meets the requirements according to the load demand data and sends it to each power consumption unit.

7. The off-grid inverter control system based on the photovoltaic energy storage system according to claim 6, characterized in that: The inverter module converts DC power into AC power that meets the requirements, including the following steps: S61, receiving load demand data collected by a data collection unit; S62, the conversion unit converts the direct current received from the input end of the inverter module into alternating current; S63, the PWM controller adjusts the frequency, amplitude and phase of the converted AC power according to the load demand data; S64, the filtering unit filters the alternating current adjusted by the PWM controller; S65, the digital signal processor adjusts the output of the filtered AC power according to the load demand data and sends it to each power consumption unit.

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