Off-grid optical storage system

Abstract

The utility model relates to the field of photovoltaic technology, and especially relates to an off-grid optical storage system. An off-grid optical storage system comprises an energy storage cabinet, an electric energy management module, an energy storage battery module B, a charging and discharging module PCS, an MPPT photovoltaic controller and a photovoltaic string, wherein the electric energy management module, the energy storage battery module B and the charging and discharging module PCS are arranged in the energy storage cabinet, and the MPPT photovoltaic controller and the photovoltaic string are arranged outside the energy storage cabinet. According to the scheme, the independent MPPT adjusting capacity of the multi-path photovoltaic string is kept, the internal wiring structure of the energy storage cabinet is simplified, the overall power generation efficiency is improved, and therefore the reliability and efficiency of the system are improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to photovoltaic technology field especially relates to a kind of off-grid light storage systems. BACKGROUND

[0002] In the current off-grid light storage application, as the system power increases continuously, the traditional light storage integrated scheme usually concentrates MPPT photovoltaic controller (maximum power point tracker) and energy storage battery and inverter (charge-discharge) module in the same cabinet (energy storage cabinet) inside. This layout can be coped with under small power scene, but when power increases, the number of photovoltaic group string increases, a large number of photovoltaic direct-current cables needed to be connected inside the system will significantly increase the complexity and engineering difficulty of wiring. The easily thought way is as follows Figure 1 The scheme (referred to as document one) generally increases a busbar box at the front end, and the function of the busbar box is to concentrate the current of multiple photovoltaic panels together, and then connect to the MPPT controller of inverter through fewer cables, so that the wiring inside the system is more concise. However, the design scheme introducing the busbar box will cause the connection between photovoltaic components and MPPT controller to be transferred, increase cable loss and construction cost, and it is difficult to track the maximum power point (MPPT) of multiple photovoltaic group strings, that is, it is difficult to maintain the independent control and optimization of multiple MPPT, thereby reducing the power generation efficiency.

[0003] Therefore, how to develop an off-grid light storage system which can maintain the independent MPPT adjustment capability of multiple photovoltaic group strings, simplify the internal wiring structure of energy storage cabinet and improve the overall power generation efficiency has become a research subject for the technical personnel in the field. INVENTION CONTENTS

[0004] The utility model aims at the deficiency of prior art to provide a kind of off-grid light storage system, to maintain the independent MPPT adjustment capability of multiple photovoltaic group strings, simplify the internal wiring structure of energy storage cabinet and improve the overall power generation efficiency, so as to improve the reliability and efficiency of system.

[0005] The utility model realizes the above-mentioned purpose by the following technical scheme: an off-grid light storage system, comprising an energy storage cabinet, an electric energy management module, a battery energy module B and a charge-discharge module PCS arranged in the energy storage cabinet, and an MPPT photovoltaic controller and a photovoltaic group string arranged outside the energy storage cabinet;Wherein:

[0006] The battery energy module B comprises an energy storage battery for storing the electric energy generated by photovoltaic power generation;

[0007] The charge-discharge module PCS is connected with the battery energy module B, and is used for bidirectional conversion of direct-current and alternating-current electric energy, so as to convert the direct-current of the energy storage battery into alternating-current output and / or store the electric energy generated by photovoltaic power generation into the energy storage battery module;

[0008] MPPT photovoltaic controller, independently installed outside the energy storage cabinet, connected with photovoltaic string and charge-discharge module PCS respectively, used for outputting photovoltaic power generation electric energy to the DC bus of the system after MPPT (Maximum Power Point Tracking) of multiple photovoltaic strings, and sharing the DC bus with the charge-discharge module PCS and the battery energy module B, so as to maintain the MPPT regulation ability of multiple photovoltaic strings under the condition of high power of the system, simplify the internal wiring and improve the overall power generation efficiency;

[0009] The energy management module is in communication connection with the MPPT photovoltaic controller, and the energy management module includes but is not limited to an EMS module and / or a BMS module. Specifically, the electric energy output by the MPPT photovoltaic controller enters the DC bus, and the battery energy module B and the charge-discharge module PCS are connected to the DC bus at the same time. The BMS module is responsible for monitoring and protecting the energy storage battery, and the energy management module can schedule the energy flow direction of the system. When the battery needs to be charged, the charge-discharge module PCS realizes the charging by converting the electric energy on the DC bus into the battery energy module B, and when the battery needs to be discharged to support the load, the DC bus is fed back to the charge-discharge module PCS, and then the charge-discharge module PCS converts the AC power to the load.

[0010] As a further scheme of the utility model, the MPPT photovoltaic controller is connected to the photovoltaic string and is independently arranged outdoors.

[0011] The energy management module includes but is not limited to an EMS module and / or a BMS module, and specifically, an EMS module or a BMS module or other existing energy management modules can be used. The energy management module is used for strategically controlling the photovoltaic input according to the real-time running state of the battery energy module B (including the state information fed back by the BMS module), closing the photovoltaic input path when the charging demand is met, charging the energy storage battery, reducing or stopping the photovoltaic input through the instruction of the MPPT photovoltaic controller when the energy storage battery is close to full charge or abnormal, or disconnecting the photovoltaic input to protect the energy storage battery, so as to realize the safe and efficient operation of the off-grid energy storage system.

[0012] As a further scheme of the utility model, the energy storage cabinet further comprises:

[0013] The photovoltaic input connection port G is connected to the MPPT photovoltaic controller.

[0014] The photovoltaic switch (H) is connected with the photovoltaic input connection port G and the charge-discharge module PCS respectively, and is used for controlling the access and exit of the MPPT photovoltaic controller.

[0015] The load output connection port F is used for connecting the load equipment.

[0016] The AC power supply connection port E is used for connecting the external AC power supply.

[0017] A stand-alone grid switching module (STS) is connected with the load output interface F, the AC power supply interface E and the charge-discharge module PCS respectively, and is used for switching the stand-alone photovoltaic storage system between the stand-alone mode and the grid-connected mode.

[0018] The electric energy management module is used for closing the photovoltaic switch H when the operation condition is met, so that the photovoltaic energy is used for charging the energy storage battery energy module B or supplying power externally through the charge-discharge module PCS; and the electric energy management module is used for disconnecting the photovoltaic switch H when the access condition is not met, so that the photovoltaic electric energy is stopped from being accessed. The electric energy management module includes but is not limited to an EMS module and / or a BMS module.

[0019] As a further scheme of the utility model, at least two MPPT photovoltaic controllers and photovoltaic groups are provided, at least one MPPT photovoltaic controller is provided with at least one MPPT, and at least one MPPT photovoltaic controller is connected with at least one photovoltaic group in one-to-one correspondence. Each photovoltaic group is tracked by the MPPT photovoltaic controller to track the maximum power point, so as to optimize the photovoltaic power generation efficiency.

[0020] The electric energy management module is connected with the external MPPT photovoltaic controller through a communication protocol (such as RS485 or CAN bus), and is used for real-time adjustment and power limiting control of the photovoltaic power output.

[0021] As a further scheme of the utility model, the electric energy management module is used for controlling the photovoltaic switch H to be closed when the battery SOC state of the energy storage battery module is lower than a preset threshold (for example, 80%) battery SOC state, and is used for controlling the photovoltaic switch H to be disconnected when the battery SOC state is higher than the preset threshold or the energy storage battery module generates an alarm.

[0022] The MPPT photovoltaic controller includes a plurality of PV input interfaces, a PV input switch, an input lightning protection circuit, a plurality of DC / DC boost circuits and an output bus and lightning protection unit. The plurality of DC / DC boost circuits track the maximum power point of different photovoltaic groups respectively, so as to keep enough MPPT quantity and improve the power generation efficiency under high-power conditions. Specifically, under the condition of system power expansion, each photovoltaic group can still maintain independent MPPT adjustment, that is, the MPPT photovoltaic controller internally includes multiple MPPTs, so as to track the maximum power point of each photovoltaic group respectively.

[0023] The photovoltaic switch H is a semiconductor switching device or a mechanical switch. The semiconductor switching device includes an IGBT or a MOS tube, and the mechanical switch includes a contactor or a relay.

[0024] A photovoltaic access and exit control method, comprising the following steps:

[0025] The power monitoring step is that the EMS module monitors the SOC state of the battery energy module B in real time;

[0026] The access judgment step is to judge whether the SOC state of the battery energy module B is lower than the first preset threshold value, if yes, the photovoltaic access step is entered, if not, the exit judgment step is entered;

[0027] The photovoltaic access step is to control the photovoltaic switch H to be closed, access the photovoltaic power generation electric energy, and the photovoltaic power generation electric energy is input into the battery energy module B for charging after being optimized by the MPPT photovoltaic controller outside the energy storage cabinet, or is output to the external load through the charge-discharge module PCS;

[0028] The exit judgment step is to judge whether the SOC state of the battery energy module B is higher than the second preset threshold value, or whether the secondary alarm state, including the overvoltage, overcurrent or high temperature state, appears, if yes, the photovoltaic exit step is entered, if not, the photovoltaic access state is continued to be kept;

[0029] The photovoltaic exit step is to control the photovoltaic switch H to be disconnected, and stop the photovoltaic power generation electric energy from being input into the battery energy module B.

[0030] As a further scheme of the utility model, the abnormal protection step further comprises: when the MPPT photovoltaic controller communication interruption or power limiting regulation failure is detected, the photovoltaic switch H is controlled to be disconnected, and the photovoltaic power generation electric energy input is stopped, so as to protect the safety of the energy storage battery module;

[0031] The access judgment step further comprises: when the SOC state of the battery is lower than the first preset threshold value, whether the temperature of the battery energy module B is lower than the upper limit of the safety range is judged preferentially, if yes, the photovoltaic access step is entered, if not, the photovoltaic access (or the photovoltaic power generation electric energy access) is stopped;

[0032] The exit judgment step is to judge whether the SOC state is higher than the second preset threshold value, whether the primary alarm state of the battery energy module B appears, if yes, the abnormality is relieved by adjusting the photovoltaic input power or reducing the charging rate, whether the secondary alarm state appears, if yes, the photovoltaic exit step is entered, if all the above conditions are not triggered, the photovoltaic access state is continued to be kept.

[0033] As a further scheme of the utility model, the abnormal protection step comprises: when the secondary alarm signal of the battery energy module B is the cell overvoltage and / or overcurrent and / or high temperature, the photovoltaic switch H is disconnected; when the MPPT photovoltaic controller power limiting failure leads to the power input being greater than the power preset value, the photovoltaic switch H is disconnected;

[0034] The exit judging step further comprises: judging whether the photovoltaic input power meets the current load demand, when the load cannot completely consume the photovoltaic power generation power, controlling the MPPT photovoltaic controller to limit the power, and when the power limiting fails or the load power demand is zero, disconnecting the photovoltaic switch H;

[0035] The first alarm state comprises that the cell voltage or temperature of the energy storage battery approaches the upper limit of the setting but has not exceeded the safety range, and indicates a slight abnormal state of the battery energy module B, for example, the cell voltage or temperature approaches the upper limit of the setting but has not exceeded the safety range, and the energy management module will process when the first alarm is triggered through adjusting the photovoltaic power, reducing the charging rate and the like;

[0036] The second alarm state comprises that the cell overvoltage, overcurrent or high temperature, and indicates that the battery energy module B appears a serious abnormal state, for example, the cell overvoltage, overcurrent or high temperature, exceeds the safety range, and protection measures need to be taken immediately, including disconnecting the photovoltaic input;

[0037] The first preset threshold is that the battery charge SOC state of the battery energy module B is lower than 80%, and the second preset threshold is that the battery charge SOC state is higher than 95%.

[0038] As a further scheme of the utility model, further comprising:

[0039] The charge and discharge monitoring step: real-time monitoring the battery charge SOC state of the battery energy module B and the power demand of the external load;

[0040] The charging control step: when the battery charge SOC state is lower than the first charging threshold, controlling the charge and discharge module PCS to enter the charging mode, and charging the energy storage battery with the photovoltaic power generation electric energy through the charge and discharge module PCS;

[0041] The charging exit step: when the battery charge SOC state reaches the second charging threshold or the battery energy module B triggers the overvoltage alarm, stopping the charging operation;

[0042] The discharging control step: when the power demand of the external load is greater than zero and the battery charge SOC state is higher than the discharging minimum threshold, controlling the charge and discharge module PCS to enter the discharging mode, and outputting the electric energy of the energy storage battery to the external load;

[0043] The discharging exit step: when the load demand is zero or the battery charge SOC state is lower than the discharging minimum threshold, stopping the discharging operation;

[0044] The first charging threshold is that the battery charge SOC state is lower than 30%, the second charging threshold is that the battery charge SOC state is higher than 95%, and the discharging minimum threshold is that the battery charge SOC state is lower than 20%;

[0045] The charging control step further comprises: before entering the charging mode, checking whether the photovoltaic input power meets the charging demand of the energy storage battery, and when the power is insufficient, preferentially adjusting the photovoltaic power generation through the MPPT photovoltaic controller, so that the photovoltaic string operates at maximum power tracking;

[0046] The discharging control step further comprises: when the load demand is insufficient, controlling the charge-discharge module PCS to enter a low-power discharging mode to reduce the discharging rate of the energy storage battery; and when the load demand suddenly increases, preferentially outputting the electrical energy of the battery energy module B to the critical load.

[0047] A photovoltaic access and exit control method comprises the following steps:

[0048] The battery state monitoring step: the battery state of charge SOC is acquired by the battery management system (BMS) module, and it is determined whether the battery state of charge SOC is lower than a preset SOC threshold value;

[0049] The access condition evaluation step: when the battery state of charge SOC is lower than the preset SOC threshold value, it is determined that the photovoltaic access condition is met;

[0050] The photovoltaic access step: when the photovoltaic access condition is met, the photovoltaic switch H is closed, the photovoltaic electrical energy processed by the MPPT photovoltaic controller (i.e. an outdoor MPPT photovoltaic controller) outside the energy storage cabinet is accessed to the system, and the photovoltaic electrical energy is used to charge the battery energy module B or supply power to the outside through the charge-discharge module PCS;

[0051] The power limitation instruction step: when the battery energy module B is close to full and cannot further supply power to the outside, the power limitation instruction is sent to the MPPT photovoltaic controller through the battery management system to reduce the photovoltaic electrical energy input;

[0052] The communication abnormality handling step: if the MPPT photovoltaic controller does not execute the power limitation instruction due to communication abnormality, the photovoltaic electrical energy input is stopped by the battery management system by opening the photovoltaic switch H to protect the battery energy module B;

[0053] The re-access determination step: when the photovoltaic switch H is opened, if the battery state of charge SOC of the battery energy module B is reduced to below a predetermined recovery threshold value, the photovoltaic switch H is closed again by the battery management system to restore the photovoltaic electrical energy access, so that the dynamic access and exit control of the photovoltaic energy source is realized.

[0054] As a further scheme of the utility model, the following charge-discharge steps of the off-grid light storage system are further included:

[0055] Charging control step: when the battery charge SOC state of the battery energy module B is lower than a first set threshold, the battery energy module B is charged by the photovoltaic power until the battery charge SOC state reaches a second set threshold or the excess photovoltaic power cannot be obtained any more;

[0056] Discharging control step: in the off-grid state, when the external power source is unavailable and the load has power demand, the battery energy module B is discharged to the load by the charge and discharge module PCS according to the battery charge SOC state and the load power demand until the battery charge SOC state decreases to a third set threshold or the load demand decreases;

[0057] Safety protection step: in the above charging control and discharging control processes, if the BMS module detects that the battery has a secondary or above alarm state, the charging power is reduced or stopped, the discharging power is limited, or the photovoltaic access is disconnected, so as to ensure the safety of the battery and the stable operation of the system.

[0058] A charge and discharge method of an off-grid photovoltaic storage system, characterized in that it comprises the following steps:

[0059] Charging monitoring step: the battery charge SOC state of the battery energy module B is monitored by the EMS module in real time to determine whether the energy storage battery needs to be charged;

[0060] Charging control step: when the battery charge SOC state is lower than a first charging threshold, the charge and discharge module PCS is controlled to enter a charging mode, and the photovoltaic power is used to charge the battery energy module B through the charge and discharge module PCS;

[0061] Charging exit step: when the battery charge SOC state reaches a second charging threshold or the battery energy module B triggers an overvoltage alarm, the charging operation is stopped;

[0062] Discharging monitoring step: the power demand of the external load and the battery charge SOC state of the battery energy module B are detected in real time;

[0063] Discharging control step: when the load power demand is greater than zero and the battery charge SOC state of the energy storage battery is higher than a discharging minimum threshold, the charge and discharge module PCS is controlled to enter a discharging mode, and the energy of the battery energy module B is output to the load;

[0064] Discharging exit step: when the load demand is zero or the battery charge SOC state of the energy storage battery is lower than the discharging minimum threshold, the discharging operation is stopped.

[0065] As a further scheme of the utility model: the first charging threshold is that the battery energy module B battery charge SOC state is lower than 30%, the second charging threshold is that the battery charge SOC state is higher than 95%; the discharge minimum threshold is that the battery energy module B battery charge SOC state is lower than 20%;

[0066] The charging control step further comprises: before entering the charging mode, checking whether the photovoltaic input power meets the charging demand of the energy storage battery, when the power is insufficient, the MPPT photovoltaic controller outside the energy storage cabinet preferentially adjusts photovoltaic power generation, so that the photovoltaic group string operates at maximum power tracking;

[0067] The discharge control step further comprises: when the load demand is insufficient, the charge and discharge module PCS enters a low-power discharge mode to reduce the discharge rate of the energy storage battery; when the load demand suddenly increases, the electric energy of the battery energy module B is preferentially output to the key load.

[0068] The scheme independently installs the MPPT photovoltaic controller outside the energy storage cabinet, and shares the electric energy channel with the charge and discharge module PCS and the battery energy module B through the DC bus, and the electric energy management module is in communication connection with the MPPT photovoltaic controller, so that the following beneficial effects are realized:

[0069] 1. Simplify internal wiring, reduce construction and maintenance difficulty:

[0070] The MPPT photovoltaic controller collects multiple photovoltaic group strings close to the outside of the energy storage cabinet, and no longer needs a large number of DC cables to penetrate into the inside of the energy storage cabinet. This significantly reduces the number and length of cables inside the cabinet, reduces wiring complexity and installation cost, so that the system can still maintain a tidy and orderly cable layout under high-power conditions, and is beneficial to later maintenance and expansion.

[0071] 2. Maintain multiple MPPT regulation capabilities and improve power generation efficiency:

[0072] Multiple photovoltaic group strings independently track the maximum power point at the outdoor MPPT controller, without excessive convergence to reduce cables. This ensures that each photovoltaic component can operate at its own optimal operating point, improves overall power generation and system efficiency, and meets the high power generation performance requirements under high-power applications.

[0073] 3. Flexibly control photovoltaic access and exit, protect the energy storage battery and improve system reliability:

[0074] Through communication between the electric energy management module and the MPPT photovoltaic controller, the system can adjust the photovoltaic access in real time according to the battery state feedback of the BMS module. When the battery is close to full charge or an abnormal alarm occurs, the electric energy management module can quickly instruct the MPPT photovoltaic controller to reduce photovoltaic output or disconnect the access, thereby avoiding overcharging and potential damage to the battery, improving system safety and operation stability.

[0075] 4. High energy flow and intelligent scheduling:

[0076] The MPPT photovoltaic controller shares photovoltaic power through a DC bus and a charge-discharge module PCS and a battery energy module B, so that the charge-discharge module PCS can flexibly select to supply photovoltaic power to the load or store it in the energy storage battery. When the load is reduced or the battery is full, the photovoltaic input can be controlled to reduce in time, which helps to realize efficient use and intelligent scheduling of energy and improve the overall performance of the off-grid photovoltaic storage system.

[0077] In summary, the present scheme advantageously solves the technical problems of complex cables, limited MPPT capability and lack of flexible adjustment means in traditional off-grid photovoltaic storage systems, to realize a safer, more efficient, easier to maintain and scalable off-grid photovoltaic storage system architecture. BRIEF DESCRIPTION OF DRAWINGS

[0078] Figure 1 is a schematic connection diagram of the circuit structure of the traditional off-grid photovoltaic storage system using a bus box to realize the connection of the high-power photovoltaic storage off-grid system.

[0079] Figure 2 is a schematic connection diagram of the circuit structure of the off-grid photovoltaic storage system of the present scheme.

[0080] Figure 3 is an electrical diagram of the off-grid photovoltaic storage system of the present scheme.

[0081] Figure 4 is an electrical system schematic diagram of the MPPT photovoltaic controller of the present scheme.

[0082] Figure 5 is an example diagram of a single DC / DC circuit in the MPPT photovoltaic controller of the present scheme.

[0083] Figure 6 is a part of the control flowchart of the photovoltaic access and exit control method of the present scheme.

[0084] Figure 7 is another part of the control flowchart of the photovoltaic access and exit control method of the present scheme. DETAILED DESCRIPTION

[0085] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. It can be understood that the drawings are only provided for reference and illustration, and are not used to limit the present application. The connection relationship shown in the drawings is only for clear description, and does not limit the connection mode.

[0086] In the related art, the current off-grid commercial and industrial light storage system is mostly developed from small-power household energy storage system. This means that the early design is mainly for small and low-power applications, and the structure is relatively simple, suitable for less photovoltaic cables and lower power demand. In these traditional systems, the MPPT (Maximum Power Point Tracking) controller module of photovoltaic is arranged in the cabinet of the inverter or the PCS (Charging and Discharging Control Module). The function of the MPPT controller is to optimize the power generation of the photovoltaic panel to the maximum, so that the system can obtain as much power as possible.

[0087] However, as the demand for system power increases, the demand for photovoltaic power generation also increases, so more photovoltaic panels are needed in parallel. This means that more PV component sources (i.e. photovoltaic) DC cables need to be connected to the MPPT controller inside the inverter. Because these cables need to be connected to one place when they are connected to the inverter, the internal wiring becomes more and more complex, increasing the complexity and difficulty of maintenance in engineering.

[0088] In order to reduce the number of cables inside the system, the first thought is to add a Figure 1 box (hereinafter referred to as Document One) at the front end. The function of the box is to concentrate the current of multiple photovoltaic panels and then connect it to the MPPT controller of the inverter through fewer cables, so as to make the internal wiring of the system more concise.

[0089] However, through repeated research by the inventor, it is found that although the box simplifies the wiring, it brings new problems: the number of MPPTs is reduced. Specifically: without using the box, each group of photovoltaic panels can be equipped with an independent MPPT controller to achieve maximum power tracking and fully utilize the power generation potential of each group of photovoltaic cells. Once the box is used, the current of multiple photovoltaic panels is concentrated, and only a few MPPT controllers can be used in the system. This means that the photovoltaic panels cannot independently track the maximum power, resulting in a decrease in the overall power generation of the photovoltaic system.

[0090] In detail, the role of the combiner box is to converge the current of multiple photovoltaic panels or strings to output a total current to the back-end device (such as an MPPT controller, an inverter), and this centralized combiner design makes the subsequent device receive the "combined current" of multiple photovoltaic strings, rather than the individual current of each string. The design of each MPPT controller is to optimize the power generation of a photovoltaic string (or a group of photovoltaic panels with a specific configuration) independently. It needs to measure the voltage and current in real time, and dynamically adjust the working state of the photovoltaic component to maximize the power generation. If the current of multiple photovoltaic strings is converged together, the MPPT controller will lose the ability to optimize each string independently, and can only manage the "combined current" as a whole. Without a combiner box, the system can configure an MPPT controller for each photovoltaic string to maximize the power generation efficiency of each string. Once the combiner box is used, the current of multiple photovoltaic strings is converged, which is equivalent to "merging" these multiple strings into an input, and only one MPPT controller is needed to manage these strings as a whole. In this way, the number of MPPT controllers in the system will be reduced, because the number of strings each controller is responsible for has increased. The working states of different photovoltaic strings are usually inconsistent (for example, the conditions such as light intensity, temperature, and dust shielding are different), and their optimal working points will differ. After convergence, the MPPT controller can only optimize an average power point for the "total current", and cannot adjust each string according to its actual situation, which will cause some strings to not run at the optimal state, reducing the power generation efficiency.

[0091] To this end, the embodiment of the present application provides an off-grid light storage off-grid light storage system, which can reduce the complexity of wiring, retain sufficient MPPT controller channels, ensure that each photovoltaic panel independently performs maximum power tracking, and improve power generation efficiency under high-power system conditions, and can flexibly control photovoltaic access and exit through a photovoltaic switch H, thereby ensuring the safe operation of the energy storage battery.

[0092] As shown in Figures 2-7 The present embodiment is based on an off-grid light storage system, which includes an energy storage cabinet and various functional modules arranged inside and outside the energy storage cabinet. Through reasonable system architecture and control strategy, the system realizes efficient cooperation between photovoltaic (PV) electric energy and energy storage battery energy module B, and ensures stable, safe and efficient operation under off-grid conditions.

[0093] System overall structure and layout:

[0094] The off-grid light storage system of the present embodiment includes an energy storage cabinet, a battery energy module B, a charge and discharge module PCS, an electric energy management module, an MPPT photovoltaic controller and a photovoltaic string.

[0095] The energy storage cabinet is internally integrated with an electric energy management module, a battery energy module B, and a charge-discharge module PCS. The electric energy management module includes, but is not limited to, an EMS module and / or a BMS module.

[0096] The battery energy module B contains energy storage batteries for storing photovoltaic generated electric energy. The BMS module continuously monitors the voltage, current, temperature, and state of charge SOC of the battery cells, and generates an alarm signal when an abnormality (such as overvoltage, overcurrent, or high temperature) occurs.

[0097] The charge-discharge module PCS serves as a bidirectional energy conversion unit, which can convert the direct current in the battery energy module B into alternating current to output to the load, and can also convert the alternating current of photovoltaic electric energy or external power into direct current to charge the battery energy module B.

[0098] The MPPT photovoltaic controller is independently installed outside the energy storage cabinet, close to the photovoltaic string, and is responsible for maximum power point tracking (MPPT) control of multiple photovoltaic components. It outputs optimized direct current to the DC bus of the system, and shares the DC bus with the charge-discharge module PCS and the battery energy module B, to realize energy collection, distribution, and allocation.

[0099] The electric energy management module is connected with the MPPT photovoltaic controller through communication, and strategically controls the photovoltaic access and exit according to the battery state of charge SOC of the battery energy module B and the BMS alarm information. The electric energy management module includes, but is not limited to, an EMS module and / or a BMS module.

[0100] Connection and control of photovoltaic power generation and energy storage module:

[0101] In the present embodiment, as Figure 4 , the MPPT photovoltaic controller contains multiple maximum power point tracking (MPPT), and the MPPT photovoltaic controller is connected to multiple photovoltaic strings through its multiple PV input interfaces. For each photovoltaic string, the internal DC / DC boost circuit of the MPPT photovoltaic controller can independently perform maximum power point tracking, so as to continuously obtain the maximum possible power generation under different light irradiance conditions. When the system size or power increases, and the number of photovoltaic strings increases, sufficient MPPT quantity can still be maintained, and the number of independent paths does not need to be reduced, thereby avoiding the reduction of power generation efficiency, and at the same time simplifying the internal wiring structure of the cabinet.

[0102] The optimized photovoltaic power by MPPT controller is delivered to battery energy module B and PCS through DC bus. When the SOC of battery energy module B is low, the power management module controls the photovoltaic switch H to be closed, and the photovoltaic power charges the battery energy module B. When the battery energy module B is close to full or an abnormal alarm (such as a secondary alarm) occurs, the power management module can instruct the MPPT photovoltaic controller to reduce the power generation power. If the power limitation fails due to communication interruption, the photovoltaic switch H is immediately disconnected to cut off the photovoltaic access and protect the battery safety.

[0103] Switching between off-grid and grid-connected modes:

[0104] The embodiment can further include a stand-alone grid-connected switching module (STS) connected with the load output interface F, the AC power supply interface E and the PCS. When the power grid is unavailable or the user expects to run completely off-grid, the stand-alone grid-connected switching module (STS) switches to the off-grid mode, so that the battery energy module B and the photovoltaic power generation independently supply power to the load. When the grid-connected power supply is available, the grid-connected operation or auxiliary power supply can be realized in the grid-connected mode. When the power grid is interrupted or the voltage is unstable, the system can quickly switch to the off-grid mode to maintain reliable power supply to the load.

[0105] Control strategy for photovoltaic access and exit:

[0106] (1) Photovoltaic access condition: The power management module determines whether the photovoltaic access is needed according to the SOC of the battery energy module B. When the SOC is lower than a first preset threshold (such as 30%), the power management module controls the photovoltaic switch H to be closed, so that the photovoltaic power is input into the system DC bus to charge the battery energy module B or supply power to the load through the PCS.

[0107] (2) Photovoltaic exit condition: When the SOC of the battery energy module B is higher than a second preset threshold (such as 95%) or a secondary alarm (such as cell overvoltage, overcurrent and high temperature) occurs and the MPPT photovoltaic controller cannot timely reduce the power output, the power management module controls the photovoltaic switch H to be disconnected, and the photovoltaic power input is stopped. This can prevent the battery energy module B from overcharging, thereby ensuring the safety and stability of the system.

[0108] (3) Abnormal protection: When the MPPT photovoltaic controller fails to execute the power limitation instruction due to communication interruption, the input power cannot be controlled and the battery safety is endangered, the power management module will immediately disconnect the photovoltaic switch H, thereby realizing emergency protection.

[0109] Charging and discharging control:

[0110] When external power is unavailable and the load has power demand, the PCS discharges energy from the battery energy module B to supply the load; when the battery energy module B SOC is insufficient, it is supplemented by photovoltaic power generation. If the battery is fully charged and the load still has demand, the system can directly supply the load with photovoltaic power by adjusting the power output of the MPPT photovoltaic controller.

[0111] At a certain threshold, the power management module controls the charging and discharging mode of the PCS to charge or discharge the battery energy module B in time to meet the load demand and battery maintenance strategy (such as ensuring battery life and avoiding over-discharge).

[0112] For multi-path MPPT control and optimization under high power conditions:

[0113] The embodiment is configured to correspond to at least one MPPT photovoltaic controller and one or more photovoltaic strings, so as to ensure that each photovoltaic string obtains MPPT control. In this way, even in a high-power scenario, high parallelism and high flexibility of MPPT adjustment can still be maintained, thereby maximizing the utilization of photovoltaic energy and improving the overall power generation efficiency.

[0114] The present solution can solve the following technical problems and achieve the corresponding beneficial effects:

[0115] Technical problems solved:

[0116] Wiring complexity and maintenance difficulty: The traditional solution embeds the MPPT controller in the energy storage cabinet, resulting in numerous cables and complex engineering. By installing the MPPT photovoltaic controller independently outside the energy storage cabinet, the convergence of photovoltaic strings and MPPT control is completed outdoors, greatly reducing the number of DC cables entering the energy storage cabinet and reducing the complexity and difficulty of the system.

[0117] Reduction of MPPT number leading to reduced power generation efficiency: The traditional solution usually uses centralized MPPT or a convergence box such as Figure 1 to converge, reducing the number of MPPTs. The embodiment of the present solution maintains a high number of MPPT channels through multiple independent MPPT photovoltaic controllers, and each photovoltaic string is independently optimized, thereby avoiding the sharp reduction of MPPT number caused by excessive convergence and ensuring the maximization of photovoltaic power generation efficiency.

[0118] Uncontrollable photovoltaic access leading to battery overcharging and safety risks: When the battery is close to full charge or in an abnormal state, if the photovoltaic input cannot be quickly disconnected or reduced, it will cause the battery to be overcharged or damaged. In the embodiment, the power management module communicates with the MPPT photovoltaic controller, and when necessary, forcibly disconnects the photovoltaic access through the photovoltaic switch H, achieving rapid and effective protection of the battery safety.

[0119] The beneficial effects achieved are:

[0120] Simplified wiring and improved maintainability: The MPPT photovoltaic controller is independently installed outside the energy storage cabinet, effectively reducing the cable burden inside the cabinet, facilitating engineering installation and later maintenance, enhancing system scalability and reliability.

[0121] Improved power generation efficiency and flexibility: Each photovoltaic group string is independently maximized by its corresponding MPPT photovoltaic controller, maintaining high power generation efficiency even in high-power application scenarios. Multiple MPPTs work in parallel, without excessive convergence in the cabinet, without sacrificing power generation performance.

[0122] Enhanced safety and rapid response capability: The power management module monitors the SOC of the battery energy module B and the BMS alarm information in real time, dynamically regulates the photovoltaic input. When the battery is fully charged or an alarm occurs, the power management module can instruct the MPPT photovoltaic controller to reduce power, and if it fails, the photovoltaic switch H is immediately disconnected, ensuring that the battery is not overcharged, improving system safety and stability.

[0123] Intelligent scheduling and efficient energy utilization: Under off-grid conditions, the power management module works with the PCS to enable flexible distribution of photovoltaic and battery energy to the load. When the load demand changes or the battery state changes, the system can flexibly adjust the photovoltaic access and power output through the power management module to achieve efficient energy utilization.

[0124] In summary, the technical information disclosed in this scheme, by independently installing the MPPT photovoltaic controller, achieving multiple MPPT independent control, configuring the power management module, battery energy module B and charge-discharge module PCS in the energy storage cabinet, and introducing the photovoltaic switch H and the corresponding photovoltaic access and exit control method, this embodiment effectively solves the technical problems of traditional off-grid photovoltaic storage systems under high-power conditions, such as complex wiring, difficulty in maintaining power generation efficiency, and inability to quickly reduce or cut off photovoltaic input when the battery is close to full. Thus, the beneficial effects of simplifying engineering wiring, maintaining multiple MPPT regulation capabilities, enhancing system safety, improving power generation efficiency, and achieving intelligent energy scheduling are achieved.

[0125] In detail:

[0126] For example, Figure 2As shown in the off-grid light storage system circuit block connection diagram of the present scheme, the photovoltaic PV assembly is connected to the off-grid light storage all-in-one machine (i.e. the energy storage cabinet) through the outdoor MPPT photovoltaic controller (i.e. the MPPT photovoltaic controller outside the energy storage cabinet) for current collection and voltage rise, and then through the series-connected photovoltaic switch H to the charge-discharge module PCS and the battery energy module B. The outdoor MPPT photovoltaic controller is no longer installed in the off-grid light storage all-in-one machine, and when power limiting needs to be performed, the outdoor MPPT photovoltaic controller is connected with the electric energy management module through communication (generally RS485).

[0127] As shown in the off-grid light storage system circuit block connection diagram of the present scheme, the photovoltaic PV assembly is connected to the off-grid light storage all-in-one machine (i.e. the energy storage cabinet) through the outdoor MPPT photovoltaic controller (i.e. the MPPT photovoltaic controller outside the energy storage cabinet) for current collection and voltage rise, and then through the series-connected photovoltaic switch H to the charge-discharge module PCS and the battery energy module B. The outdoor MPPT photovoltaic controller is no longer installed in the off-grid light storage all-in-one machine, and when power limiting needs to be performed, the outdoor MPPT photovoltaic controller is connected with the electric energy management module through communication (generally RS485). Figure 3 As shown in the off-grid light storage system electrical diagram of the present scheme, it includes two parts of the off-grid light storage all-in-one machine and the photovoltaic MPPT controller. The three-phase alternating voltage enters the off-grid and grid switching module (STS) after passing through the grid switch breaker to realize off-grid and grid switching, and is then output to the input end of the charge-discharge module PCS, while being transmitted to the load through the load switch breaker, and a maintenance bypass switch is further added between the grid and the load to manually ensure the power supply of the load in the case of failure of the off-grid and grid switching module (STS). The three-phase voltage at the input end of the charge-discharge module PCS is converted by the AC / DC conversion of the charge-discharge module PCS to output the P+ end and the P- end of the DC bus. The DC bus of the P+ end and the P- end is connected with the energy storage battery pack through the high-voltage box, which includes a soft start circuit, a fuse and a breaker protection circuit, and a loop current detection circuit inside; the DC bus of the P+ end and the P- end is connected with the external MPPT photovoltaic controller through the series-connected photovoltaic switch H. Since the photovoltaic PV assembly has the characteristic of limited current, i.e. the current will not be much larger than the rated current after output short circuit, the breaker protection function is not significant, so the photovoltaic switch H is generally selected to be a switch that can be automatically controlled by software, typically a contactor or a high-power relay. The battery cluster is the battery energy module B.

[0128] As shown in the off-grid light storage system circuit block connection diagram of the present scheme, the photovoltaic PV assembly is connected to the off-grid light storage all-in-one machine (i.e. the energy storage cabinet) through the outdoor MPPT photovoltaic controller (i.e. the MPPT photovoltaic controller outside the energy storage cabinet) for current collection and voltage rise, and then through the series-connected photovoltaic switch H to the charge-discharge module PCS and the battery energy module B. The outdoor MPPT photovoltaic controller is no longer installed in the off-grid light storage all-in-one machine, and when power limiting needs to be performed, the outdoor MPPT photovoltaic controller is connected with the electric energy management module through communication (generally RS485). Figure 4 As shown in the electrical system schematic diagram of the MPPT photovoltaic controller of the present scheme, the positive and negative of 16 PV strings are connected, pass through the photovoltaic input switch and the input lightning protection circuit, and are then tapped to multiple DC / DC circuits for MPPT control. Meanwhile, the outputs of multiple groups of DC / DC circuits are uniformly collected and lightning protection to form the positive and negative BUS outputs.

[0129] As shown in the off-grid light storage system circuit block connection diagram of the present scheme, the photovoltaic PV assembly is connected to the off-grid light storage all-in-one machine (i.e. the energy storage cabinet) through the outdoor MPPT photovoltaic controller (i.e. the MPPT photovoltaic controller outside the energy storage cabinet) for current collection and voltage rise, and then through the series-connected photovoltaic switch H to the charge-discharge module PCS and the battery energy module B. The outdoor MPPT photovoltaic controller is no longer installed in the off-grid light storage all-in-one machine, and when power limiting needs to be performed, the outdoor MPPT photovoltaic controller is connected with the electric energy management module through communication (generally RS485). Figure 5The single DC / DC circuit example diagram in the MPPT photovoltaic controller of the present scheme is shown, the input voltage is connected with the inductor L after the capacitor filtering, in the conduction stage of IGBT(T), the inductor current increases, in the closing stage of IGBT(T), the inductor current charges the output capacitor through the diode D, with the inductor current drops, the energy stored on the inductor in the early stage is transferred to the rear output capacitor, realizing the boost conversion of input voltage to output voltage. In normal circumstances, the DC / DC circuit does MPPT (Max Power Point Tracking), that is, the input voltage is changed to make the output power of PV maximum.

[0130] As shown in Figure 6 The part of the control flow chart of the photovoltaic access and exit control method of the present scheme is shown, which is the BMS alarm detection flow chart of the battery energy module B of the off-grid photovoltaic storage integrated machine. The control system of the battery management module reads the voltage and temperature data of all the battery cells of the energy storage battery and the data of the cluster current in real time, judges whether the above data exceeds the first alarm threshold, if not, returns; if yes, further judges whether it exceeds the second alarm threshold. At this time, if it exceeds the first alarm threshold, but does not exceed the second alarm threshold, the BMS first alarm flag is set. If it exceeds the second alarm, further judges whether it exceeds the third alarm threshold. At this time, if it exceeds the second alarm threshold, but does not exceed the third alarm threshold, the BMS second alarm flag is set, and if it exceeds the third alarm threshold, the BMS third alarm flag is set. The first, second and third alarm thresholds of the cell voltage, temperature and current are respectively set relative to the respective rated values, 3.5V, 3.55V and 3.6V are the first, second and third alarm thresholds of the cell voltage, and 3.0V, 2.95V and 2.85V are the first, second and third alarm thresholds of the cell voltage. Similarly, the current and temperature are also similar.

[0131] As shown in Figure 7Another part of the control flow chart of the photovoltaic access and exit control method of the present scheme is shown. The system reads the SOC state of the battery energy module B in real time, if SOC < 80%, the series photovoltaic switch H is closed, the battery energy module B is charged, or the photovoltaic energy is discharged externally through the charge and discharge module C (charge and discharge module PCS). In the state that the series photovoltaic switch H is closed when SOC < 80%, it is further judged whether the specific BMS module of the power management module reaches the secondary warning, if it reaches the secondary warning, the specific information of the secondary warning is read, if it is the secondary overvoltage of the cell voltage or the secondary charging overcurrent of the battery current, the series photovoltaic switch H is disconnected, and the access of the photovoltaic energy is stopped. The specific BMS module of the power management module is generally divided into three levels of protection, when the first level of warning occurs, the charge and discharge target power is reduced, when the second level of warning occurs, the charge and discharge target power is set to 0, and when the third level of warning occurs, the contactor switch of the battery controller is tripped, and the charge and discharge is stopped. When the battery is fully charged, the battery voltage reaches the secondary warning, and the target power is set to 0, but due to the long distance of the MPPT, the power limit may fail, in order to prevent the battery from reaching the third level of warning protection, the input energy of the photovoltaic needs to be disconnected in time, that is, the series photovoltaic switch H is disconnected. Or when the number of the system photovoltaic PV component sources is too large, the voltage is too high, and the power is also too large, even if the MPPT photovoltaic controller stops boosting, the current is also relatively large, which exceeds the secondary protection of the battery energy module B, and the series photovoltaic switch H also needs to be disconnected.

[0132] The battery charge SOC state of the lithium ion battery can be calculated by various methods, including a method based on cycle times, a method based on voltage and current, a method based on a battery model, a method based on laboratory test data, and a chemical method, a voltage method, an electrochemical impedance method, a current integration method, a Kalman filtering method, a neural network method, etc. The method based on cycle times is based on the cycle times of the battery and the energy loss after cycling. The battery charge SOC state of the battery is determined by calculating the energy loss of the battery after multiple cycles. The advantage is that the capacity attenuation of the battery can be accurately calculated, and the disadvantage is that a large number of tests and calculation corrections need to be performed on the battery.

[0133] Finally, it should be noted that those skilled in the art will cross-reference or superimpose various embodiments of the present scheme, which still belongs to the original disclosure range of the present scheme. In addition, the above is only the preferred embodiment of the present utility model, and is not used to limit the present utility model, although the present utility model has been described in detail with reference to the foregoing embodiments, for those skilled in the art, the technical scheme recorded in the foregoing embodiments can still be modified, or some technical features can be replaced equivalently, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present utility model shall be included in the protection scope of the present utility model.

Claims

1. An off-grid optical storage system, characterized in that, The energy storage cabinet, the electric energy management module, the battery energy module (B), and the charge-discharge module (PCS) arranged in the energy storage cabinet, and the MPPT photovoltaic controller and the photovoltaic string arranged outside the energy storage cabinet are included. The battery energy module (B) includes an energy storage battery for storing photovoltaic power generation electric energy. The charge-discharge module (PCS) is connected with the battery energy module (B) and is used for bidirectional conversion of direct current and alternating current electric energy. The MPPT photovoltaic controller is independently installed outside the energy storage cabinet, is connected with the photovoltaic string and the charge-discharge module (PCS), respectively, and is used for outputting photovoltaic power generation electric energy to a direct current bus of the system after maximum power point tracking (MPPT) of multiple photovoltaic strings and sharing the direct current bus with the charge-discharge module (PCS) and the battery energy module (B). The electric energy management module is in communication connection with the MPPT photovoltaic controller.

2. The off-grid optical storage system of claim 1, wherein, The MPPT photovoltaic controller is connected with the photovoltaic string and is independently arranged outdoors. The electric energy management module is used for controlling photovoltaic access according to a real-time running state of the battery energy module (B), closing a photovoltaic input path to charge the energy storage battery when a charging demand is met, and reducing or stopping photovoltaic input or disconnecting photovoltaic access through the MPPT photovoltaic controller when the energy storage battery approaches full charge or an abnormality occurs.

3. The off-grid optical storage system of claim 1, wherein, The energy storage cabinet further includes: A photovoltaic input connection port (G) connected with the MPPT photovoltaic controller; A photovoltaic switch (H) connected with the photovoltaic input connection port (G) and the charge-discharge module (PCS), respectively, and used for controlling access and exit of the MPPT photovoltaic controller; A load output connection port (F) used for connecting a load device; An alternating current power supply connection port (E) used for connecting an external alternating current power supply; and An off-grid and grid-connected switching module (STS) connected with the load output connection port (F), the alternating current power supply connection port (E), and the charge-discharge module (PCS), respectively, and used for switching the off-grid photovoltaic storage system between an off-grid mode and a grid-connected mode. The electric energy management module is used for closing the photovoltaic switch (H) to make photovoltaic energy used for charging the battery energy module (B) or supplying power to the outside through the charge-discharge module (PCS) when a running condition is met, and disconnecting the photovoltaic switch (H) to stop photovoltaic electric energy access when an access condition is not met.

4. The off-grid optical storage system of claim 1, wherein, The MPPT photovoltaic controller and the photovoltaic string each have at least one, at least one MPPT photovoltaic controller is provided with at least one MPPT, at least one MPPT photovoltaic controller is correspondingly connected with at least one photovoltaic string, each photovoltaic string is tracked by the MPPT photovoltaic controller to optimize photovoltaic power generation efficiency; The electric energy management module is connected with the external MPPT photovoltaic controller through a communication protocol and is used for real-time adjustment and power limiting control of photovoltaic power output.

5. The off-grid optical storage system of claim 2, wherein, The electric energy management module is used for controlling the photovoltaic switch (H) to be closed when a state of charge (SOC) of the energy storage battery module is lower than a preset threshold state of charge (SOC) and to be disconnected when the state of charge (SOC) is higher than the preset threshold or the energy storage battery module generates an alarm. The MPPT photovoltaic controller comprises a multi-path PV input interface, a PV input switch, an input lightning protection circuit, a plurality of DC / DC boost circuits and an output bus and lightning protection unit, the plurality of DC / DC boost circuits respectively track maximum power points of different photovoltaic groups. The photovoltaic switch (H) is a semiconductor switching device or a mechanical switch.

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