A comprehensive energy efficiency evaluation method for a photovoltaic energy storage microgrid system

Abstract

The present application relates to photovoltaic power generation technical field, specifically provide a kind of comprehensive energy efficiency evaluation method of light storage microgrid system, method includes: according to the actual working junction temperature of photovoltaic power generation component of light storage microgrid system and daily total irradiance, combined with power temperature attenuation coefficient, the daily comprehensive energy efficiency of photovoltaic power generation component is calculated;According to the DC side comprehensive round-trip efficiency of energy storage unit of energy storage component, and the conversion efficiency of energy storage converter of energy storage component in charge-discharge mode, the non-steady-state comprehensive round-trip efficiency of energy storage component is calculated;According to daily comprehensive energy efficiency, non-steady-state comprehensive round-trip efficiency, photovoltaic direct supply ratio and AC comprehensive line loss rate, the comprehensive energy efficiency of light storage microgrid system is calculated.The present application combines photovoltaic strong / weak light segmentation and energy storage temperature loss model, introduces energy routing factor, can multi-working condition analysis and evaluation larger light storage microgrid comprehensive energy efficiency such as industrial park.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic power generation technology, and in particular to a method for evaluating the comprehensive energy efficiency of a photovoltaic-storage microgrid system. Background Technology

[0002] To overcome the limitations of single photovoltaic (PV) power generation, the combination of microgrid technology and energy storage systems (ESS) has emerged. Organically integrating PV power generation systems with energy storage systems using power electronic conversion equipment forms a PV-storage microgrid system, which is currently one of the most effective methods for solving the problems of distributed renewable energy consumption and grid connection. The energy storage system in the PV-storage microgrid acts as an energy buffer, absorbing excess energy when sunlight is abundant and power generation exceeds load, and releasing energy to compensate for power shortages during periods of insufficient sunlight or peak demand. Due to its ability to suppress power fluctuations, the PV-storage microgrid can operate as a micro-independent power system off-grid or interconnected with the main power grid, thereby greatly improving the reliability and flexibility of power supply.

[0003] Although photovoltaic-storage microgrid technology has entered the stage of large-scale application, the academic and engineering communities have significant problems in oversimplifying and severing the physical mechanisms when conducting system-level macroscopic energy efficiency evaluations. Traditional studies mostly use static constant method models, which assume that the overall conversion efficiency of the photovoltaic array over the calculation period is a fixed experience discount and that the AC / DC round-trip efficiency of the energy storage system is anchored to a certain nominal value. However, the static evaluation system has obvious theoretical flaws in practical applications, mainly reflected in the neglect of the unsteady-state distortions of both the photovoltaic side and the energy storage system. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a comprehensive energy efficiency evaluation method for photovoltaic-storage microgrid systems, so as to solve the problem that the efficiency and energy evaluation of photovoltaic-storage microgrid systems in related technologies is overly simplified and the physical mechanisms are fragmented, resulting in low accuracy.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution: This invention provides a method for evaluating the comprehensive energy efficiency of a photovoltaic-storage microgrid system, comprising: Based on the actual junction temperature and total daily irradiance of the photovoltaic power generation modules in the photovoltaic-storage microgrid system, and combined with the power temperature decay coefficient, the daily comprehensive energy efficiency of the photovoltaic power generation modules is calculated. The unsteady-state integrated round-trip efficiency of the energy storage component is calculated based on the DC-side comprehensive round-trip efficiency of the energy storage unit and the conversion efficiency of the energy storage converter in charge and discharge mode. The overall energy efficiency of the photovoltaic-storage microgrid system is calculated based on the daily comprehensive energy efficiency, the unsteady-state comprehensive round-trip efficiency, the photovoltaic direct supply ratio, and the AC comprehensive line loss rate.

[0006] In some embodiments of the present invention, the daily comprehensive energy efficiency of the photovoltaic power generation module is calculated based on the actual operating junction temperature and total daily irradiance of the photovoltaic power generation module in the photovoltaic-storage microgrid system, combined with the power temperature decay coefficient, including: The actual working junction temperature is calculated based on the ambient temperature and the total daily irradiance. Compare the total daily irradiance with the segmented threshold; When the total daily irradiance is not less than the segmented threshold, and the inverter is in the high irradiance range, the daily comprehensive energy efficiency under heavy load conditions is obtained based on the actual operating junction temperature, the temperature decay coefficient, and the inverter's nominal efficiency under heavy load. When the total daily irradiance is less than the segmented threshold, it is in the low irradiance range. Based on the actual operating junction temperature, the temperature decay coefficient, and the inverter light load index loss term, the daily comprehensive energy efficiency under light load conditions is obtained.

[0007] In some embodiments of the present invention, the daily comprehensive energy efficiency under heavy load conditions is obtained based on the actual operating junction temperature, the temperature decay coefficient, and the inverter's nominal efficiency under heavy load, including: Calculate the temperature correction term based on the actual operating junction temperature and the temperature decay coefficient; The daily comprehensive energy efficiency under heavy load is obtained by multiplying the temperature correction term by a preset coefficient and the inverter's nominal efficiency under heavy load. Based on the actual operating junction temperature, the temperature decay coefficient, and the inverter's light-load exponential loss term, the daily comprehensive energy efficiency under light-load conditions is obtained, including: Calculate the temperature correction term based on the actual operating junction temperature and the temperature decay coefficient; The daily comprehensive energy efficiency under light load conditions is obtained by multiplying the temperature correction term by a preset coefficient and the inverter light load index loss term.

[0008] In some embodiments of the present invention, the actual operating junction temperature is calculated based on the ambient temperature and the total daily irradiance, including: The total daily irradiance is calculated using the integral summation formula based on the time-series sampling values ​​and sampling intervals of irradiance. Based on the total daily irradiance and the effective sunshine duration, the equivalent average irradiance during the effective sunshine period is obtained; The equivalent temperature rise coefficient is calculated based on the rated battery operating temperature of the photovoltaic module and its standard conditions, as well as the effective sunshine duration. The actual operating junction temperature of the photovoltaic module is calculated based on the ambient temperature, total daily irradiance, and equivalent temperature rise coefficient.

[0009] In some embodiments of the present invention, the unsteady-state comprehensive round-trip efficiency of the energy storage component is calculated based on the DC-side comprehensive round-trip efficiency of the energy storage unit and the conversion efficiency of the energy storage converter in charge-discharge mode, including: The combined round-trip efficiency of the DC side is calculated based on the ambient temperature and a sixth-order high-order polynomial model. The unsteady-state integrated round-trip efficiency is obtained by multiplying the DC-side comprehensive round-trip efficiency, the conversion efficiency of the energy storage converter in charging mode, and the conversion efficiency of the energy storage converter in discharging mode.

[0010] In some embodiments of the present invention, the comprehensive energy efficiency of the photovoltaic-storage microgrid system is calculated based on the daily comprehensive energy efficiency, the unsteady-state comprehensive round-trip efficiency, the photovoltaic direct supply ratio, and the AC comprehensive line loss rate, including: Calculate the energy path weighting term based on the photovoltaic direct supply ratio and the unsteady-state comprehensive round-trip efficiency; Multiplying the daily integrated energy efficiency by the energy path weighting term yields the source-storage coupling basic efficiency; The overall energy efficiency of the photovoltaic-storage microgrid system is calculated by multiplying the source-storage coupling basic efficiency by the AC integrated line loss rate.

[0011] In some embodiments of the present invention, the method further includes: When the photovoltaic-storage microgrid system is in a grid-connected operating state with energy surplus, the corresponding comprehensive energy efficiency is calculated based on the grid connection ratio and the conversion efficiency of each link. When the photovoltaic-storage microgrid system is in a grid-connected operating state with energy shortage, the corresponding comprehensive energy efficiency is calculated based on the grid disconnection ratio and the conversion efficiency of each link.

[0012] In some embodiments of the present invention, when the photovoltaic-storage microgrid system is in a grid-connected operating state with energy surplus, the conversion efficiency of each component includes the grid-connected transmission efficiency and the conversion efficiency of the energy storage converter. Based on the internet access ratio and the conversion efficiency of each stage, the corresponding overall energy efficiency is calculated, including: Calculate the local direct supply path efficiency term based on the photovoltaic direct supply ratio and the AC comprehensive line loss rate; Calculate the surplus power grid connection efficiency term based on the grid connection ratio and grid transmission efficiency; The energy storage buffer path efficiency term is calculated based on the weighting coefficient, the conversion efficiency of the energy storage converter, the comprehensive round-trip efficiency on the DC side, and the comprehensive line loss rate on the AC side. The efficiency items of the local direct supply path, the surplus power grid connection path, and the energy storage buffer path are added together to obtain the weighted sum of energy paths. The overall energy efficiency under the surplus power grid connection condition is calculated based on the daily comprehensive energy efficiency and the weighted sum of the energy paths.

[0013] In some embodiments of the present invention, when the photovoltaic-storage microgrid system is in a grid-connected operating state with energy shortage, the conversion efficiency of each component includes the grid power supply reference efficiency and the conversion efficiency of the energy storage converter. Based on the grid connection ratio and the conversion efficiency of each stage, the corresponding overall energy efficiency is calculated, including: Based on the photovoltaic direct supply ratio, the conversion efficiency of the energy storage converter, and the comprehensive round-trip efficiency of the DC side, the photovoltaic side energy path weighting term is calculated. Based on the daily comprehensive energy efficiency, the photovoltaic side energy path weighting term, and the proportion of photovoltaic power supply to the load, calculate the total efficiency term of the photovoltaic power supply branch; Calculate the efficiency term of the power supply branch in the grid based on the grid off-grid ratio and the grid power supply benchmark efficiency; The total efficiency of the photovoltaic power supply branch is added to the efficiency of the grid-connected power supply branch to obtain the total weighted efficiency of the load power supply. The overall energy efficiency of the grid-connected operating conditions is calculated based on the AC integrated line loss rate and the total weighted efficiency of the load power supply.

[0014] In some embodiments of the present invention, the method further includes: After calculating the overall energy efficiency, the overall energy efficiency is compared with the expected target efficiency to clarify the direction of efficiency adjustment; Based on the relationship between the influencing parameter and the overall energy efficiency, the influencing parameter is adjusted so that the overall energy efficiency approaches the target efficiency. The influencing parameters include the direct photovoltaic power supply ratio, the grid connection ratio, and the grid disconnection ratio.

[0015] Compared with the prior art, the above-described technical solution of the present invention has the following advantages: This invention proposes a comprehensive energy efficiency evaluation method for photovoltaic-storage microgrid systems. Addressing the challenges of complex multi-source power flow and difficulty in quantifying unsteady-state losses in AC-coupled photovoltaic-storage microgrids, this method establishes a multi-physics unsteady-state sub-model. It obtains the dynamic junction temperature of photovoltaic modules through NOCT equivalent mapping, introduces a segmented efficiency model for inverters under strong / weak illumination, and combines temperature polarization polynomials to characterize temperature-related losses in energy storage. Furthermore, it introduces the direct photovoltaic supply ratio, grid connection ratio, and grid disconnection ratio as energy routing factors to distinguish multiple energy paths, including direct supply, energy storage buffering, and grid interaction, enabling analytical calculation of the system's comprehensive energy efficiency under various operating conditions such as islanding, surplus power grid connection, and grid disconnection. The method considers the coupling effects of meteorological environment, device thermoelectric losses, and scheduling strategies, achieving high evaluation accuracy and providing reliable technical support for energy efficiency analysis and operation optimization of photovoltaic-storage microgrids in industrial parks. Attached Figure Description

[0016] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other embodiments based on these drawings without creative effort.

[0017] Figure 1 This is a topology diagram of the photovoltaic-storage microgrid system according to an embodiment of the present invention; Figure 2 This is a flowchart illustrating a comprehensive energy efficiency evaluation method for a photovoltaic-storage microgrid system provided in an embodiment of the present invention. Figure 3 A schematic diagram of the structure of the electronic device provided in the embodiment of the present invention. Detailed Implementation

[0018] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0019] The physical topology of a distributed photovoltaic-storage microgrid system determines how energy is collected, where it flows, and how various electrical devices are coupled. Taking into account factors such as good compatibility with industrial park power distribution networks, convenient modular expansion of equipment, and reliable system operation, this embodiment of the invention establishes a distributed AC-coupled photovoltaic-storage microgrid physical topology model with a 380V common AC bus as the main hub.

[0020] In this topology, the photovoltaic-storage microgrid system mainly consists of the following nodes, which are composed of external connection nodes and physical units.

[0021] External interconnection and grid connection nodes: Microgrid systems achieve physical interconnection with the upper-level utility grid using static transfer switches (STS) or points of common coupling (PCC). These nodes have bidirectional power flow interaction capabilities and, under normal operating conditions, provide rigid support for the microgrid's frequency and voltage. When the microgrid's power is insufficient or lacking, they act as a safety net at the lower level.

[0022] Distributed photovoltaic (PV) power generation units, serving as the sole internal power source for a microgrid system, consist of multiple PV arrays and corresponding string inverters (DC / AC). The fluctuating DC power generated by the PV modules after receiving solar radiation must be converted into 380V AC power that meets power quality standards through maximum power point tracking (MPPT) and unidirectional inversion processing by the inverter before it can be unidirectionally injected into the common AC bus.

[0023] In this embodiment of the invention, the energy storage dispatch unit uses high-cycle-life, high-safety lithium iron phosphate battery clusters as a microgrid energy buffer. Since the battery system only supports physical access to DC power, a bidirectional energy storage converter (PCS, with AC / DC and DC / AC bidirectional conversion functions) is installed in the system. When there is excess AC bus power, the PCS operates in rectification mode, converting AC power into DC power to charge the battery clusters; when the bus power supply is insufficient, the PCS switches to inverter mode, converting the chemical energy in the battery clusters into AC power and releasing it to the bus.

[0024] Terminal power units include various AC loads such as heavy motors, central air conditioning, and lighting equipment in the industrial park. They are directly connected in parallel to the 380V common AC bus and have the physical property of unidirectionally absorbing AC power.

[0025] like Figure 1As shown, the biggest advantage of the AC-coupled architecture is that it completely decouples the "source" and "storage" from the AC side. The photovoltaic system and the energy storage system each have independent power conversion modules and do not affect each other. Therefore, the energy management system (EMS) can flexibly perform millisecond-level independent scheduling of the photovoltaic direct supply ratio and the energy storage charge and discharge depth.

[0026] In order to accurately measure the actual physical losses generated by devices within a microgrid during AC / DC conversion, this embodiment of the invention must strictly define the system operating boundary and the dimensions of multi-physics coupling at the beginning of modeling.

[0027] In a real distributed grid-connected topology, the main grid acts like a high-capacity "energy sponge," readily absorbing or replenishing the power deficit of the microgrid. However, the high efficiency of external power exchange can easily mask the cascading losses incurred by the microgrid's internal photovoltaic and energy storage systems during unsteady-state environments and charge-discharge cycles. Therefore, this invention, in performing system-level unsteady-state loss analysis, establishes a progressive operational boundary of "first isolating isolated systems, then integrating them into the grid."

[0028] First, in the microgrid basic physical characteristics analysis phase, the system is set to "maximum autonomous operation mode," that is, through real-time precise scheduling of the energy management system, the instantaneous power balance of "source-load-storage" within the microgrid is forced to be achieved, so that the interaction power between the microgrid and the upper-level power grid approaches zero. This "islanding" baseline effectively eliminates the data dilution effect of the high transmission efficiency of the external power grid, establishing a rigorous benchmark for exploring the overlapping loss patterns of energy storage and photovoltaic thermal degradation. It should be noted that islanding operation here differs from complete off-grid operation. Here, "islanding" refers only to an ideal state where the interaction power between the microgrid and the upper-level main grid is close to zero. The energy storage converter does not need to switch to a grid-connected control mode, which is fundamentally different from the control architecture of true off-grid operation.

[0029] Then, in the comprehensive energy efficiency evaluation stage under all operating conditions, the island boundary is broken through, and a two-way interaction mechanism of the large power grid (i.e., surplus power going to the grid and power going off the grid) is added to restore the real multi-source power flow topology of the distributed microgrid in the actual industrial park. The determination of the dynamic boundary from closed to open can ensure the rigor of microscopic physical analysis on the one hand, and provide certain guidance for macroscopic engineering applications on the other hand.

[0030] like Figure 2 As shown in the figure, this embodiment of the invention provides a flowchart of a method for evaluating the comprehensive energy efficiency of a photovoltaic-storage microgrid system. Figure 2This is a flowchart illustrating the comprehensive energy efficiency evaluation method for a photovoltaic-storage microgrid system. This flowchart only shows the logical sequence of the method in this embodiment; however, in other possible embodiments of the invention, different methods may be used, provided there are no conflicts. Figure 2 Complete the steps shown or described in the order indicated.

[0031] See Figure 2 The method of this invention specifically includes the following steps: Step S101: Calculate the daily comprehensive energy efficiency of the photovoltaic power generation modules based on the actual operating junction temperature and total daily irradiance of the photovoltaic power generation modules in the photovoltaic-storage microgrid system, combined with the power temperature decay coefficient.

[0032] In this embodiment of the invention, this step specifically includes steps S1011 to S1014.

[0033] Step S1011: Calculate the actual working junction temperature based on the ambient temperature and total daily irradiance.

[0034] When photovoltaic modules operate outdoors, their photoelectric conversion efficiency is significantly affected by the module's operating junction temperature. To convert meteorological data into a temperature variable that can be incorporated into the system efficiency model, this embodiment of the invention employs the Nominal Operating Cell Temperature (NOCT) equivalent method: first, the sampled irradiance is integrated into the total daily irradiance, then converted into the equivalent average irradiance during the effective sunshine period, and finally substituted into the NOCT temperature rise relationship to obtain the mapping between the actual operating junction temperature of the photovoltaic module and the ambient temperature and total daily irradiance. The general form is shown in equation (1-1).

[0035] (1-1) in, The actual junction temperature of the photovoltaic module, in units of... ; The outdoor reference temperature for the photovoltaic-storage microgrid system is given in units of 1. ; The total daily radiation on the horizontal surface, in units of ; The equivalent temperature rise coefficient, determined jointly by the component's NOCT parameters and the effective sunshine duration, is taken in this embodiment. ; The rated operating cell temperature of a photovoltaic module is an inherent factory parameter of the photovoltaic module.

[0036] The specific calculation steps are as follows: According to the irradiance sequence The total daily irradiance was calculated, where, For the first The sampling time interval corresponding to the sampling point; For the first Instantaneous irradiance at each sampling point; This refers to the number of sampling points per day. Press again Calculate the equivalent average irradiance during the effective sunshine period, where, Effective sunshine duration; Finally, substitute Calculate the actual junction temperature of the photovoltaic module.

[0037] The temperature rise coefficient in equation (1-1) is not an empirical guess. The NOCT test reference ambient temperature is 20℃ and the irradiance is 800W / m².

[0038] Embodiments of the present invention =45℃, effective sunshine duration ,therefore ,Right now .

[0039] If the component's NOCT or effective sunshine duration changes, the coefficient must be recalculated; 3.125 cannot be regarded as a constant applicable to all sites and seasons.

[0040] Step S1012: Compare the total daily irradiance with the segmented threshold.

[0041] by This represents the segmented threshold for total daily irradiance. This parameter is related to the site irradiance distribution, module series-parallel connection method, inverter MPPT voltage window, and light-load efficiency curve, and is not a universal constant. This embodiment of the invention establishes a segmented model based on annual measured data from a 50kW test platform in a certain location, obtaining... .

[0042] In this embodiment of the invention, only empirical switching parameters are used to distinguish between light-load and high-load areas. When migrating to other sites or equipment configurations, the daily irradiance, DC input energy, and AC output energy recorded by the on-site SCADA system (Supervisory Control and Data Acquisition) should be used for segmented regression or breakpoint identification, and the threshold should be verified in conjunction with the inverter's MPPT lower limit and load rate curve. Direct application of [specific parameters] is not advisable. .

[0043] Step S1013: When the total daily irradiance is not less than the segmented threshold ( Under the condition of high irradiation, the daily comprehensive energy efficiency under heavy load is obtained based on the actual junction temperature, temperature decay coefficient and inverter heavy load nominal efficiency.

[0044] Step S1014: When the total daily irradiance is less than the segmented threshold ( Under the condition of low irradiance, the daily comprehensive energy efficiency under light load is obtained based on the actual junction temperature, temperature decay coefficient, and inverter light load index loss term.

[0045] In this embodiment of the invention, a 50kW distributed photovoltaic test platform in a certain location is used as the object. Using annual data on daily irradiance on the inclined plane and actual power generation, nonlinear relationships between photovoltaic array efficiency, inverter efficiency, and daily irradiance are established. The study found that MPPT operating voltage mismatch and inverter light-load operation under low irradiance conditions are the main reasons for the decrease in system efficiency; the error between the dynamic model and the measured monthly system efficiency is 2%–5%. Based on this, this embodiment of the invention introduces a piecewise relationship for irradiance and superimposes the junction temperature correction of equation (1-1) to obtain the calculation formula for the daily comprehensive energy efficiency, as shown in equation (1-2).

[0046] (1-2) The total daily irradiance is not less than the segmented threshold ( In the case of ), based on the actual working temperature With temperature decay coefficient Calculate the temperature correction term The daily comprehensive energy efficiency under heavy load is obtained by multiplying the temperature correction term by a preset coefficient of 0.90 and the inverter's nominal efficiency under heavy load.

[0047] When the total daily irradiance is less than the segmented threshold ( In the case of ), based on the actual working temperature With temperature decay coefficient Calculate the temperature correction term The temperature correction term is multiplied by a preset coefficient of 0.90, and the inverter light load index loss term is also applied. The daily comprehensive energy efficiency under light load conditions is obtained.

[0048] The power temperature degradation coefficient of the photovoltaic module is 0.004℃ in some embodiments of the present invention, based on the selected module parameters. - ¹ The actual values ​​may vary depending on the components. You can consult the manufacturer for these values. This invention does not impose any restrictions on them. The nominal efficiency of the inverter under heavy load is 0.98. At the same time, the power attenuation caused by the junction temperature of the components is still retained. When the equipment model or operating conditions change, the efficiency should be corrected to 0.98 based on the manufacturer's efficiency curve or on-site measured data. This is an exponential loss function derived for inverters under light load conditions. 0.75 and the inverter light load exponential loss term are measured fitting parameters from this embodiment of the invention. When used for other inverters or array configurations, they should be recalibrated using equipment efficiency curves or field data.

[0049] This is the daily integrated energy efficiency of a photovoltaic power generation unit under given daily total irradiance and module operating junction temperature. The variable transfer relationship explains that the external meteorological input to the system model remains daily total irradiance and ambient temperature. During calculation, the actual operating junction temperature of the photovoltaic module is first obtained from equation (1-1). Then, the actual work results were... Substitute into equation (1-2). Therefore, equation (1-2) is written as... To maintain consistency of variables within the formula; after embedding into a system-level model, its composite form is: .

[0050] In the low-light mismatch and light load penalty range ( The theoretical maximum power point voltage of the photovoltaic array may be close to or lower than the lower limit of the inverter's MPPT voltage. Simultaneously, the DC-side load rate of the inverter is low, increasing the proportion of array tracking losses and converter standby losses. In the higher irradiance stable output range (… When the DC input power of the inverter enters the higher load region, the conversion efficiency tends to stabilize.

[0051] Step S102: Calculate the unsteady-state integrated round-trip efficiency of the energy storage module based on the DC-side integrated round-trip efficiency of the energy storage unit and the conversion efficiency of the energy storage converter in charge-discharge mode.

[0052] Energy loss in energy storage units mainly stems from electrochemical polarization heating of the battery itself and high-frequency switching losses in the PCS (Power Control System). For lithium iron phosphate batteries, charge transfer impedance and electrolyte viscosity change drastically with ambient temperature. At low temperatures, hindered ion diffusion causes a sharp increase in internal resistance. Within a moderately warming range, electrochemical reaction kinetics improve, leading to increased energy conversion efficiency.

[0053] To accurately reflect this complex nonlinear thermoelectric process, this embodiment of the invention cites the long-term experimental engineering conclusions of Huo Shouxing et al. regarding outdoor 1500V high-capacity liquid-cooled energy storage cabinets. Specifically, within the temperature range of 5–50℃, the overall energy efficiency of the battery cabinet increases with temperature; above 50℃, electrolyte side reactions intensify, leading to a decrease in efficiency. By controlling the single-cell charge / discharge voltage between 2.8 and 3.6V, and employing a combined control of a 40℃ threshold for the battery body and a 30℃ outlet water temperature in heating mode, both efficiency and lifespan can be balanced. The highest cabinet-level energy efficiency achieved in the engineering test reached 95.24%. Based on this conclusion, this embodiment of the invention fits the DC-side round-trip energy efficiency of the battery body as a function of ambient temperature. The sixth-order higher-order polynomial model is shown in equation (2-1): (2-1) in, The combined round-trip efficiency on the DC side of the energy storage unit; the effective definition of this polynomial is physically bounded at... between.

[0054] It should be noted that Formula (2-1) is an empirical formula summarized based on measured data of liquid-cooled energy storage cabinets. It is suitable for the comprehensive energy efficiency assessment of larger photovoltaic-energy storage microgrid systems in industrial parks, and can be used as a reference for other energy storage systems. In addition, Formula (2-1) focuses on the influence of temperature. After the energy storage system is installed, temperature is an important factor affecting its efficiency during operation.

[0055] Considering that industrial microgrids (EMS) actively guide energy storage converters to avoid harsh, inefficient operating ranges by setting control dead zones during actual operation, this embodiment of the invention provides a reasonable and efficient equivalent treatment for the converter stage. The unsteady-state comprehensive round-trip efficiency of the entire energy storage unit (covering the entire process of bidirectional AC-DC conversion of the energy storage converter and battery chemical storage) is also considered. The expression is as shown in equation (2-2): (2-2) in, The unsteady overall round-trip efficiency of the energy storage unit connected to the AC bus side; The conversion efficiency of the energy storage converter in charging mode; The conversion efficiency of the energy storage converter in discharge mode; and In some embodiments of this invention, the value is 0.97. and The specific values ​​may vary depending on the application, and this invention does not impose any limitations on them.

[0056] It should be noted that, on a specific day, the energy storage system may operate in one of the following states: charging only; discharging only; both charging and discharging; and neither charging nor discharging. Regardless of the state, each state is a variation of formula (2-2). For example, if only discharging occurs, there is no charging conversion efficiency term in (2-2). Furthermore, over a longer period, the energy storage system will eventually achieve both charging and discharging. For simplicity, the subsequent discussion of microgrid systems will only cover the most complex scenario: the situation where both charging and discharging occur. The efficiency of microgrid systems in other operating states can be referenced to this scenario.

[0057] Step S103: Calculate the overall energy efficiency of the photovoltaic-storage microgrid system based on the daily comprehensive energy efficiency, unsteady-state comprehensive round-trip efficiency, photovoltaic direct supply ratio, and AC comprehensive line loss rate.

[0058] After the unsteady-state physical model of the underlying core equipment is established, the solution for the system-level macroscopic efficiency needs to be combined with the scheduling strategy of energy flow paths. Figure 1 In the AC-coupled topology shown, the usable electrical energy generated by the photovoltaic system has two completely different physical transmission paths. The first is the direct supply path (low loss): after flowing out of the photovoltaic inverter, the electrical energy is directly consumed by the load through the AC bus, resulting in only one DC / AC conversion and line loss. The second is the energy storage buffer path (high loss): the electrical energy cannot be consumed by the load in time at the bus side, so it enters the PCS rectification (AC / DC), becoming chemical energy stored. When load demand increases, it is released through a chemical reaction and output by the PCS inverter (DC / AC). This results in a very high AC / DC cascade conversion cost.

[0059] To mathematically quantify the energy transfer weights of these two paths, this invention extracts and defines the photovoltaic direct supply ratio. As the core energy routing factor characterizing the internal energy scheduling strategy of the system.

[0060] In this embodiment of the invention, the steps for calculating the overall energy efficiency of the photovoltaic-storage microgrid system include: According to the direct supply ratio of photovoltaic power Combined round-trip efficiency with unsteady state The energy path weighting term is calculated using the following formula: ;in, The range of values ​​is strictly defined within the closed interval [0,1]. Multiplying the daily integrated energy efficiency by the energy path weighting term yields the source-storage coupling basic efficiency, calculated using the following formula: ]; Multiply the source-storage coupling basic efficiency by the AC comprehensive line loss rate. The overall energy efficiency of the photovoltaic-storage microgrid system is calculated using the formula shown in equation (3-1): (3-1) in, The AC comprehensive line loss rate of the 380V AC bus and internal cables of the photovoltaic-storage microgrid system is set to 0.99 in some embodiments of this invention. However, this value may vary depending on the actual system. Therefore, this invention... The specific value is not limited.

[0061] High light conditions For example, the analytical expression for the comprehensive energy efficiency with multi-parameter expansion is shown in equation (3-2): (3-2) After completing the modeling of individual photovoltaic modules and energy storage batteries, they are applied to system-level energy flow analysis. In actual industrial park microgrid projects, microgrids generally need to achieve energy exchange with the upper-level distribution network. According to the source-load matching situation, there are two operating conditions: "surplus electricity fed into the grid" and "disconnected from the main grid".

[0062] In some embodiments of the invention, the method for evaluating the overall energy efficiency of the photovoltaic-storage microgrid system of the present invention further includes: When the photovoltaic-storage microgrid system is in a grid-connected operating state with energy surplus, the corresponding comprehensive energy efficiency is calculated based on the grid connection ratio and the conversion efficiency of each link. When the photovoltaic-storage microgrid system is in a grid-connected operating state with energy shortage, the corresponding comprehensive energy efficiency is calculated based on the grid disconnection ratio and the conversion efficiency of each link.

[0063] When a photovoltaic-storage microgrid system is in a grid-connected operating state with energy surplus, the conversion efficiency of each component includes the grid-connected transmission efficiency and the conversion efficiency of the energy storage converter.

[0064] When sunlight is abundant and local load is low, the photovoltaic-storage microgrid system, after meeting its own consumption and energy storage charging needs, feeds surplus electricity into the main grid. (Definition of grid connection ratio) ( The percentage of total photovoltaic power generation directly connected to the main power grid is denoted as . In this case, energy flow is divided into local direct supply (…). ), large power grid feed-in ( ) and stored energy ( Taking into account both grid connection efficiency and the conversion efficiency of the energy storage converter, the overall energy efficiency under the condition of surplus power being fed into the grid is calculated. The calculation formula is shown in equation (4-1): (4-1) The specific calculation process is as follows: According to the direct supply ratio of photovoltaic power Combined line loss rate Calculate the efficiency of the local direct supply path. ; Based on internet usage rate With grid-connected transmission efficiency Calculate the efficiency of the surplus power grid connection path. ; According to the weighting coefficient Conversion efficiency of energy storage converter DC-side comprehensive round-trip efficiency and AC integrated line loss rate Calculate the energy storage buffer path efficiency term ; Adding the efficiency items of the local direct supply path, the surplus electricity grid connection path, and the energy storage buffer path yields the weighted sum of energy paths. ; Daily comprehensive energy efficiency Multiplying the weighted sum of energy paths by the total energy efficiency, the overall energy efficiency under the surplus power grid connection condition is calculated. .

[0065] High light conditions For example, the comprehensive energy efficiency analytical expression for the surplus power grid connection operation under multi-parameter expansion is shown in equation (4-2): (4-2) When a photovoltaic-storage microgrid system is in a grid-connected operating state with energy shortage, the conversion efficiency of each component includes the grid power supply reference efficiency and the conversion efficiency of the energy storage converter.

[0066] When encountering cloudy or rainy days, weak sunlight in the early morning or late afternoon, or nighttime, the microgrid photovoltaic power generation is insufficient to support the local load, and the photovoltaic-storage microgrid system needs to purchase electricity from the main grid to supplement it. Define the grid connection depth factor. ( The percentage of total load demand supplied by the external power grid is represented by ( ). The overall energy efficiency under grid-connected operating conditions is calculated by comprehensively considering the grid supply baseline efficiency and the conversion efficiency of the energy storage converter. As shown in equation (4-3): (4-3) The specific calculation process is as follows: According to the direct supply ratio of photovoltaic power Conversion efficiency of energy storage converter and DC-side integrated round-trip efficiency Calculate the photovoltaic-side energy path weighting term ; Based on daily comprehensive energy efficiency PV-side energy path weighting and the proportion of PV power supplied to loads Calculate the total efficiency term of the photovoltaic power supply branch. ; Based on the offline ratio Compared with grid power supply reference efficiency Calculate the efficiency of the power supply branch in the power grid. ; The total efficiency of the photovoltaic power supply branch is added to the efficiency of the grid-connected power supply branch to obtain the total weighted efficiency of the load power supply. The overall line loss rate of AC The overall energy efficiency under grid-connected operating conditions is calculated by multiplying the total weighted efficiency of the load power supply. .

[0067] High light conditions For example, the analytical expression for the comprehensive energy efficiency under the grid-connected operating conditions with multiple parameters is shown in equation (4-4): (4-4) The comprehensive energy efficiency formula for the photovoltaic-storage microgrid system shown in Equation (3-1), the comprehensive energy efficiency formula for the surplus power grid connection condition shown in Equation (4-1), and the comprehensive energy efficiency formula for the grid disconnection condition shown in Equation (4-3) can be regarded as related to parameters. The overall energy efficiency objective function is determined. Therefore, in some embodiments of the invention, after calculating the overall energy efficiency, the overall energy efficiency is compared with the expected target efficiency to clarify the direction of efficiency adjustment; based on the influencing parameter terms... The relationship between the overall energy efficiency and the overall energy efficiency is investigated, and the influencing parameters are adjusted to make the overall energy efficiency approach the target efficiency.

[0068] An embodiment of the present invention also provides a non-transitory machine-readable medium storing a computer program, wherein the computer program, when executed by a computer's processor, is used to cause the computer to perform a comprehensive energy efficiency evaluation method for a photovoltaic-storage microgrid system according to an embodiment of the present invention.

[0069] An embodiment of the present invention also provides a computer program product, including a computer program, wherein the computer program, when executed by a computer's processor, is used to cause the computer to perform the comprehensive energy efficiency evaluation method for a photovoltaic-storage microgrid system according to an embodiment of the present invention.

[0070] An embodiment of the present invention also provides an electronic device, comprising: at least one processor; and a memory communicatively connected to the at least one processor. The memory stores a computer program executable by the at least one processor, which, when executed by the at least one processor, causes the electronic device to perform the integrated energy efficiency evaluation method for a photovoltaic-storage microgrid system according to an embodiment of the present invention.

[0071] refer to Figure 3The present invention will now describe a structural block diagram of an electronic device that can serve as an embodiment of the present invention, serving as an example of a hardware device applicable to various aspects of the present invention. The electronic device is intended to represent various forms of digital electronic computer devices, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processors, cellular phones, smartphones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely illustrative and are not intended to limit the implementation of the present invention described and / or claimed herein.

[0072] like Figure 3 As shown, the electronic device includes a computing unit 101, which can perform various appropriate actions and processes based on a computer program stored in a read-only memory (ROM) 102 or a computer program loaded from a storage unit 108 into a random access memory (RAM) 103. The RAM 103 may also store various programs and data required for the operation of the electronic device. The computing unit 101, ROM 102, and RAM 103 are interconnected via a bus 104. An input / output (I / O) interface 105 is also connected to the bus 104.

[0073] Multiple components in the electronic device are connected to I / O interface 105, including: input unit 106, output unit 107, storage unit 108, and communication unit 109. Input unit 106 can be any type of device capable of inputting information into the electronic device. Input unit 106 can receive input digital or character information and generate key signal inputs related to user settings and / or function control of the electronic device. Output unit 107 can be any type of device capable of presenting information and may include, but is not limited to, a display, speaker, video / audio output terminal, vibrator, and / or printer. Storage unit 108 may include, but is not limited to, disks and optical discs. Communication unit 109 allows the electronic device to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks, and may include, but is not limited to, modems, network cards, infrared communication devices, and / or wireless communication transceivers, such as Bluetooth devices, WiFi devices, WiMax devices, cellular communication devices, and / or the like.

[0074] The computing unit 101 can be a variety of general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of the computing unit 101 include, but are not limited to, CPUs, graphics processing units (GPUs), various special-purpose artificial intelligence (AI) computing units, various computing units running machine learning model algorithms, digital signal processors (DSPs), and any suitable processor, controller, microcontroller, etc. The computing unit 101 performs the various methods and processes described above. For example, in some embodiments, the method embodiments of the present invention can be implemented as computer programs tangibly contained in a machine-readable medium, such as storage unit 108. In some embodiments, part or all of the computer program can be loaded and / or installed on an electronic device via ROM 102 and / or communication unit 109. In some embodiments, the computing unit 101 can be configured to perform the methods described above by any other suitable means (e.g., by means of firmware).

[0075] Computer programs for implementing the methods of embodiments of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus, such that when executed by the processor or controller, the computer programs cause the functions / operations specified in the flowcharts and / or block diagrams to be performed. The computer programs may be executed entirely on a machine, partially on a machine, or as a standalone software package, partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0076] In the context of embodiments of this invention, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. A machine-readable signal medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, or infrared systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0077] It should be noted that the term "comprising" and its variations used in the embodiments of this invention are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The modifications of "one" and "a plurality" mentioned in the embodiments of this invention are illustrative and not restrictive, and those skilled in the art should understand that unless explicitly indicated otherwise in the context, they should be understood as "one or more".

[0078] The user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in the embodiments of this invention are subject to strict compliance with relevant laws, regulations, and regulatory requirements in their collection, storage, use, processing, transmission, provision, and disclosure, and adhere to the principles of legality, legitimacy, necessity, and good faith. The acquisition of relevant information and data is premised on the user's explicit consent or other legitimate reasons, and a clear and convenient authorization management approach is provided to the user, allowing the user to independently choose to consent, withdraw consent, or refuse to provide relevant information. For functions that rely on user information, if the user does not authorize or withdraws authorization, the corresponding technical function cannot be implemented, and the technical solution of this invention is not applicable in this scenario.

[0079] The steps described in the method embodiments provided by the present invention can be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of protection of the present invention is not limited in this respect.

[0080] The term "embodiment" in this specification refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily imply the same embodiment, nor does it imply independence or alternativeity from other embodiments. The various embodiments in this specification are described in a related manner, with reference to each other for similar or identical parts. In particular, for apparatus, device, and system embodiments, since they are substantially similar to method embodiments, the description is relatively simple, and relevant details are referred to in the description of the method embodiments.

[0081] The above embodiments merely illustrate several implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for evaluating the comprehensive energy efficiency of a photovoltaic-storage microgrid system, characterized in that, include: Based on the actual junction temperature and total daily irradiance of the photovoltaic power generation modules in the photovoltaic-storage microgrid system, and combined with the power temperature decay coefficient, the daily comprehensive energy efficiency of the photovoltaic power generation modules is calculated. The unsteady-state integrated round-trip efficiency of the energy storage component is calculated based on the DC-side comprehensive round-trip efficiency of the energy storage unit and the conversion efficiency of the energy storage converter in charge and discharge mode. The overall energy efficiency of the photovoltaic-storage microgrid system is calculated based on the daily comprehensive energy efficiency, the unsteady-state comprehensive round-trip efficiency, the photovoltaic direct supply ratio, and the AC comprehensive line loss rate.

2. The method for evaluating the comprehensive energy efficiency of a photovoltaic-storage microgrid system according to claim 1, characterized in that, Based on the actual junction temperature and total daily irradiance of the photovoltaic (PV) power generation modules in the photovoltaic-storage microgrid system, and combined with the power temperature decay coefficient, the daily comprehensive energy efficiency of the PV power generation modules is calculated, including: The actual working junction temperature is calculated based on the ambient temperature and the total daily irradiance. Compare the total daily irradiance with the segmented threshold; When the total daily irradiance is not less than the segmented threshold, and the inverter is in the high irradiance range, the daily comprehensive energy efficiency under heavy load conditions is obtained based on the actual operating junction temperature, the temperature decay coefficient, and the inverter's nominal efficiency under heavy load. When the total daily irradiance is less than the segmented threshold, it is in the low irradiance range. Based on the actual operating junction temperature, the temperature decay coefficient, and the inverter light load index loss term, the daily comprehensive energy efficiency under light load conditions is obtained.

3. The comprehensive energy efficiency evaluation method for a photovoltaic-storage microgrid system according to claim 2, characterized in that, Based on the actual operating junction temperature, the temperature decay coefficient, and the inverter's nominal efficiency under heavy load, the daily comprehensive energy efficiency under heavy load conditions is obtained, including: Calculate the temperature correction term based on the actual operating junction temperature and the temperature decay coefficient; The daily comprehensive energy efficiency under heavy load is obtained by multiplying the temperature correction term by a preset coefficient and the inverter's nominal efficiency under heavy load. Based on the actual operating junction temperature, the temperature decay coefficient, and the inverter's light-load exponential loss term, the daily comprehensive energy efficiency under light-load conditions is obtained, including: Calculate the temperature correction term based on the actual operating junction temperature and the temperature decay coefficient; The daily comprehensive energy efficiency under light load conditions is obtained by multiplying the temperature correction term by a preset coefficient and the inverter light load index loss term.

4. The method for evaluating the comprehensive energy efficiency of a photovoltaic-storage microgrid system according to claim 2, characterized in that, The actual operating junction temperature is calculated based on the ambient temperature and total daily irradiance, including: The total daily irradiance is calculated using the integral summation formula based on the time-series sampling values ​​and sampling intervals of irradiance. Based on the total daily irradiance and the effective sunshine duration, the equivalent average irradiance during the effective sunshine period is obtained; The equivalent temperature rise coefficient is calculated based on the rated operating temperature of the photovoltaic module's cells and its standard conditions, as well as the effective sunshine duration. The actual operating junction temperature of the photovoltaic module is calculated based on the ambient temperature, total daily irradiance, and equivalent temperature rise coefficient.

5. The method for evaluating the comprehensive energy efficiency of a photovoltaic-storage microgrid system according to claim 1, characterized in that, The unsteady-state comprehensive round-trip efficiency of the energy storage component is calculated based on the DC-side integrated round-trip efficiency of the energy storage unit and the conversion efficiency of the energy storage converter in charge-discharge mode, including: The combined round-trip efficiency of the DC side is calculated based on the ambient temperature and a sixth-order high-order polynomial model. The unsteady-state integrated round-trip efficiency is obtained by multiplying the DC-side comprehensive round-trip efficiency, the conversion efficiency of the energy storage converter in charging mode, and the conversion efficiency of the energy storage converter in discharging mode.

6. The method for evaluating the comprehensive energy efficiency of a photovoltaic-storage microgrid system according to claim 1, characterized in that, The overall energy efficiency of the photovoltaic-storage microgrid system is calculated based on the daily comprehensive energy efficiency, the unsteady-state comprehensive round-trip efficiency, the photovoltaic direct supply ratio, and the AC comprehensive line loss rate, including: Calculate the energy path weighting term based on the photovoltaic direct supply ratio and the unsteady-state comprehensive round-trip efficiency; Multiplying the daily integrated energy efficiency by the energy path weighting term yields the source-storage coupling basic efficiency; The overall energy efficiency of the photovoltaic-storage microgrid system is calculated by multiplying the source-storage coupling basic efficiency by the AC integrated line loss rate.

7. The method for evaluating the comprehensive energy efficiency of a photovoltaic-storage microgrid system according to claim 1, characterized in that, The method further includes: When the photovoltaic-storage microgrid system is in a grid-connected operating state with energy surplus, the corresponding comprehensive energy efficiency is calculated based on the grid connection ratio and the conversion efficiency of each link. When the photovoltaic-storage microgrid system is in a grid-connected operating state with energy shortage, the corresponding comprehensive energy efficiency is calculated based on the grid disconnection ratio and the conversion efficiency of each link.

8. The method for evaluating the comprehensive energy efficiency of a photovoltaic-storage microgrid system according to claim 7, characterized in that, When the photovoltaic-storage microgrid system is in a grid-connected operating state with energy surplus, the conversion efficiency of each component includes the grid-connected transmission efficiency and the conversion efficiency of the energy storage converter. Based on the internet access ratio and the conversion efficiency of each stage, the corresponding overall energy efficiency is calculated, including: Calculate the local direct supply path efficiency term based on the photovoltaic direct supply ratio and the AC comprehensive line loss rate; Calculate the surplus power grid connection efficiency term based on the grid connection ratio and grid transmission efficiency; The energy storage buffer path efficiency term is calculated based on the weighting coefficient, the conversion efficiency of the energy storage converter, the comprehensive round-trip efficiency on the DC side, and the comprehensive line loss rate on the AC side. The efficiency items of the local direct supply path, the surplus power grid connection path, and the energy storage buffer path are added together to obtain the weighted sum of energy paths. The overall energy efficiency under the surplus power grid connection condition is calculated based on the daily comprehensive energy efficiency and the weighted sum of the energy paths.

9. The method for evaluating the comprehensive energy efficiency of a photovoltaic-storage microgrid system according to claim 7, characterized in that, When the photovoltaic-storage microgrid system is in a grid-connected operating state with energy shortage, the conversion efficiency of each component includes the grid power supply reference efficiency and the conversion efficiency of the energy storage converter. Based on the grid connection ratio and the conversion efficiency of each stage, the corresponding overall energy efficiency is calculated, including: Based on the photovoltaic direct supply ratio, the conversion efficiency of the energy storage converter, and the comprehensive round-trip efficiency of the DC side, the photovoltaic side energy path weighting term is calculated. Based on the daily comprehensive energy efficiency, the photovoltaic side energy path weighting term, and the proportion of photovoltaic power supply to the load, calculate the total efficiency term of the photovoltaic power supply branch; Calculate the efficiency term of the power supply branch in the grid based on the grid off-grid ratio and the grid power supply benchmark efficiency; The total efficiency of the photovoltaic power supply branch is added to the efficiency of the grid-connected power supply branch to obtain the total weighted efficiency of the load power supply. The overall energy efficiency of the grid-connected operating conditions is calculated based on the AC integrated line loss rate and the total weighted efficiency of the load power supply.

10. The method for evaluating the comprehensive energy efficiency of a photovoltaic-storage microgrid system according to claim 7, characterized in that, The method further includes: After calculating the overall energy efficiency, the overall energy efficiency is compared with the expected target efficiency to clarify the direction of efficiency adjustment; Based on the relationship between the influencing parameter and the overall energy efficiency, the influencing parameter is adjusted so that the overall energy efficiency approaches the target efficiency. The influencing parameters include the direct photovoltaic power supply ratio, the grid connection ratio, and the grid disconnection ratio.

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