A direct current coupling type photovoltaic energy storage system

Abstract

The utility model discloses a direct current coupling type photovoltaic energy storage system relates to photovoltaic energy storage technical field. This photovoltaic energy storage system includes battery group, photovoltaic module, photovoltaic converter, energy storage converter, charge -discharge control circuit and detection control module. When detecting that photovoltaic power generation power is greater than the power required by load, the redundant electric energy charges the battery, after detecting that the battery group is full, the second electronic switch opens, and charging stops. At this time, the photovoltaic converter can continue to output, realize power generation maximization consumption, and the system will not be down due to the overvoltage of battery group. When detecting that photovoltaic power generation power is insufficient, the first electronic switch is closed, and if the battery group discharges, the second electronic switch is closed. When detecting that photovoltaic power generation power is sufficient, the battery group is charged again. The utility model aims at solving the problem of the existing system for preventing battery overcharge and frequently interrupting photovoltaic power supply or limiting battery full charge, resulting in the problem of reducing photovoltaic energy utilization.

Description

Technical Field

[0001] This utility model relates to the field of photovoltaic energy storage system technology, and in particular to a DC-coupled photovoltaic energy storage system. Background Technology

[0002] With the rapid development of new energy technologies, DC-coupled photovoltaic energy storage systems have been widely used in distributed energy, microgrids, and industrial and commercial power applications. In this type of system, the photovoltaic converter, energy storage converter, and battery system are coupled together via a DC bus, aiming to maximize the utilization of photovoltaic power generation while ensuring that the battery does not overcharge when it is close to full charge, thereby ensuring the stable operation of the system.

[0003] Current technical solutions typically employ two methods to prevent battery overcharging. The first method involves actively shutting down the photovoltaic converter's output after the battery is fully charged, then discharging the battery to a predetermined capacity (e.g., SOC dropping to 95%) via the energy storage converter, before restarting the photovoltaic MPPT operation. The second method involves charging the battery to near full charge (e.g., SOC reaching 95%), then adjusting the photovoltaic output power to match load demand. However, both methods have significant drawbacks: the former releases capacity through frequent charge-discharge cycles, causing unnecessary battery aging and reducing lifespan, while also interrupting photovoltaic power generation and affecting overall energy efficiency; the latter sacrifices the battery's effective energy storage capacity and places extremely high demands on the real-time adjustment accuracy and response speed of photovoltaic power. If the load fluctuates drastically or control is delayed, it can still lead to excess energy and a rise in DC bus voltage, ultimately forcing the system into passive protection mode or even causing battery overcharging. Utility Model Content

[0004] The main purpose of this invention is to provide a DC-coupled photovoltaic energy storage system, which aims to solve the problem that existing systems frequently interrupt photovoltaic power supply or limit full battery charging to prevent battery overcharging, resulting in reduced photovoltaic energy utilization.

[0005] To achieve the above objectives, the present invention proposes a DC-coupled photovoltaic energy storage system, comprising:

[0006] Battery pack;

[0007] Photovoltaic modules are used to convert solar energy into direct current power output.

[0008] A photovoltaic converter, connected to the photovoltaic module, is used to convert the DC power output from the photovoltaic module into voltage and then output it.

[0009] An energy storage converter is connected to both the photovoltaic converter and the mains power. The energy storage converter is used to convert the DC power output from the photovoltaic converter and / or the battery pack into AC power output, or to convert the mains power into the charging power output required by the battery pack.

[0010] A charge / discharge control circuit is connected to the battery pack, the photovoltaic converter, and the energy storage converter, respectively, and is used to control the charging / discharging of the battery pack; wherein, the charge / discharge control circuit includes a first electronic switch, a second electronic switch, a first diode, and a second diode;

[0011] The first terminal of the first electronic switch, the positive terminal of the first diode, and the positive output terminal of the photovoltaic converter are connected to the positive terminal of the DC power supply of the energy storage converter. The second terminal of the first electronic switch, the first terminal of the second electronic switch, the negative terminal of the first diode, and the negative terminal of the second diode are connected to the negative terminal of the second diode. The second terminal of the second electronic switch and the positive terminal of the second diode are connected to the positive terminal of the battery pack.

[0012] A detection and control module is connected to the battery pack, the photovoltaic converter, the controlled terminal of the first electronic switch, and the controlled terminal of the second electronic switch. The detection and control module is used to detect the power generation of the photovoltaic converter and the state of charge of the battery pack, and control the operation of the first electronic switch and the second electronic switch according to the power generation of the photovoltaic converter, the power required by the electrical load, and the state of charge of the battery pack.

[0013] In one embodiment, the charge / discharge control circuit further includes a third electronic switch and a first resistor;

[0014] The first end of the third electronic switch is connected to the first end of the first electronic switch, the second end of the third electronic switch is connected to one end of the first resistor, and the other end of the first resistor is connected to the second end of the second electronic switch.

[0015] In one embodiment, one or more of the first electronic switch, the second electronic switch, and the third electronic switch are contactors.

[0016] In one embodiment, the charge / discharge control circuit further includes a first fuse, a first shunt, and a fourth electronic switch;

[0017] In this configuration, one end of the first fuse is connected to the second end of the second electronic switch, and the other end of the first fuse is connected to the positive terminal of the battery pack. One end of the first shunt is connected to the negative terminal of the battery pack, and the other end of the first shunt is connected to the second end of the fourth electronic switch. The first end of the fourth electronic switch and the negative output terminal of the photovoltaic converter are connected to the negative DC power supply terminal of the energy storage converter. The signal output terminal of the first shunt is connected to the detection and control module, and the controlled terminal of the fourth electronic switch is connected to the detection and control module.

[0018] In one embodiment, the DC-coupled photovoltaic energy storage system further includes a first bipolar circuit breaker;

[0019] The first terminal of the first bipolar circuit breaker is connected to the first terminal of the first electronic switch. The second terminal of the first bipolar circuit breaker and the positive output terminal of the photovoltaic converter are connected to the positive DC power supply terminal of the energy storage converter. The third terminal of the first bipolar circuit breaker is connected to the first terminal of the fourth electronic switch. The fourth terminal of the first bipolar circuit breaker and the negative output terminal of the photovoltaic converter are connected to the negative DC power supply terminal of the energy storage converter. The controlled terminal of the first bipolar circuit breaker is connected to the detection and control module.

[0020] In one embodiment, the photovoltaic converter includes a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a first capacitor, a second capacitor, a first inductor, a second inductor, a third inductor, and a fourth inductor.

[0021] In this configuration, the first end of the first switch, the first end of the fifth switch, and one end of the first capacitor are connected to the positive output terminal of the photovoltaic converter; the second end of the first switch and the first end of the second switch are connected to one end of the second inductor; the second end of the second switch is connected to the first end of the third switch; the second end of the third switch and the first end of the fourth switch are connected to one end of the fourth inductor; the second end of the fourth switch, the second end of the eighth switch, and one end of the second capacitor are connected to the negative output terminal of the photovoltaic converter; the second end of the fifth switch and the first end of the sixth switch are connected to one end of the first inductor; the second end of the sixth switch is connected to the first end of the seventh switch; the second end of the seventh switch and the first end of the eighth switch are connected to one end of the third inductor; and the other ends of the first inductor, the second inductor, the third inductor, and the fourth inductor are connected to the photovoltaic module.

[0022] In one embodiment, the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, and the eighth switch are all MOSFETs with anti-integrated parallel diodes.

[0023] In one embodiment, the energy storage converter includes a third capacitor, a fourth capacitor, and a three-phase switching branch; each phase of the switching branch includes a ninth switch, a tenth switch, an eleventh switch, a twelfth switch, a third diode, and a fourth diode;

[0024] Specifically, one end of the third capacitor and the second end of the ninth switch are connected to the positive terminal of the DC power supply of the energy storage converter; the other end of the third capacitor, one end of the fourth capacitor, the positive terminal of the third diode, and the negative terminal of the fourth diode are connected; the first end of the ninth switch and the second end of the tenth switch are connected to the negative terminal of the third diode; the first end of the tenth switch and the second end of the eleventh switch are connected to the power supply terminal of one phase of the switching branch; the first end of the eleventh switch and the second end of the twelfth switch are connected to the positive terminal of the fourth diode; and the other end of the fourth capacitor and the first end of the twelfth switch are connected to the negative terminal of the DC power supply of the energy storage converter.

[0025] In one embodiment, the ninth, tenth, eleventh, and twelfth switching transistors are all MOS transistors with anti-integrated parallel diodes.

[0026] In one embodiment, the energy storage converter further includes a fifth inductor, a sixth inductor, a seventh inductor, an eighth inductor, a ninth inductor, a tenth inductor, a fifth capacitor, a sixth capacitor, and a seventh capacitor;

[0027] Wherein, one end of the seventh inductor is connected to the power supply terminal of the first phase conversion branch, one end of the sixth inductor is connected to the power supply terminal of the second phase conversion branch, one end of the fifth inductor is connected to the power supply terminal of the third phase conversion branch, the other end of the seventh inductor, one end of the sixth capacitor, one end of the seventh capacitor are connected to one end of the tenth inductor, the other end of the sixth inductor, one end of the fifth capacitor, one end of the sixth capacitor are connected to one end of the ninth inductor, the other end of the fifth inductor, the other end of the fifth capacitor, the other end of the seventh capacitor are connected to one end of the eighth inductor, and the other end of the eighth inductor, the other end of the ninth inductor, and the other end of the tenth inductor are used to connect to the mains power.

[0028] This utility model employs a DC-coupled photovoltaic energy storage system, comprising a battery pack, photovoltaic modules, a photovoltaic converter, an energy storage inverter, a charge / discharge control circuit, and a detection and control module. The photovoltaic modules convert solar energy into DC power output; the photovoltaic converter converts the DC power output from the photovoltaic modules into voltage; the energy storage inverter converts the DC power output from the photovoltaic converter and / or battery pack into AC power output, or converts mains power into the charging power required by the battery pack; the charge / discharge control circuit includes a first electronic switch, a second electronic switch, a first diode, and a second diode. In this utility model, the detection and control module detects the power output of the photovoltaic converter and the state of charge (SOC) of the battery pack. When the power output of the photovoltaic converter exceeds the power required by the load, the photovoltaic power generation charges the battery pack. Once the SOC of the battery pack is detected to be fully charged, the second electronic switch is disconnected, stopping charging. At this time, the first electronic switch and the second diode are conducting, maintaining voltage regulation on the bus, while external current cannot flow into the battery pack through the first diode, ensuring a stable state of DC bus voltage regulation and preventing overcharging of the battery pack. At this time, the detection and control module can control the photovoltaic converter to continue tracking the power required by the load and continuously output power, maximizing the consumption of photovoltaic power generation. This invention does not require high control precision from the photovoltaic converter; even if the photovoltaic converter is improperly controlled, it will only raise the bus voltage, and the photovoltaic energy storage system will not shut down due to overvoltage protection of the battery pack. When the power output of the photovoltaic converter is detected to be less than the power required by the load, the first electronic switch is kept closed. If the detection and control module detects battery discharge, it immediately closes the second electronic switch to enter discharge mode. In this mode, the battery pack directly discharges to the load, preventing overheating caused by prolonged discharge of the first diode. When the power output of the photovoltaic converter is detected to be greater than the power required by the load again, the battery is recharged until the battery pack reaches a fully charged state, at which point the second electronic switch is opened to stop charging. Thus, this invention allows the battery pack to reach a fully charged state during photovoltaic energy storage without needing to discharge to prevent overcharging. It can also instantly enter discharge mode when backup power is needed, ensuring off-grid backup power requirements. Compared with the prior art, this invention can prevent the battery pack from being overcharged and does not require frequent interruption of photovoltaic power supply or limitation of full charging of the battery pack, thus maximizing the utilization of photovoltaic energy. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0030] Figure 1 A schematic diagram of an embodiment of the DC-coupled photovoltaic energy storage system provided by this utility model;

[0031] Figure 2 A schematic diagram of another embodiment of the DC-coupled photovoltaic energy storage system provided by this utility model;

[0032] Figure 3 An electronic circuit diagram of a photovoltaic converter in an embodiment of a DC-coupled photovoltaic energy storage system provided by this utility model;

[0033] Figure 4 Electronic circuit diagram of the energy storage converter in an embodiment of the DC-coupled photovoltaic energy storage system provided by this utility model;

[0034] Figure 5 A schematic diagram of the structure of a photovoltaic energy storage system, which is an exemplary example of the present invention.

[0035] Explanation of icon numbers:

[0036]

[0037] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0038] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0039] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0040] Furthermore, the use of terms such as "first" and "second" in this utility model is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this utility model.

[0041] Current technical solutions typically employ two methods to prevent battery overcharging. The first method involves actively shutting down the photovoltaic converter's output after the battery is fully charged, then discharging the battery to a predetermined capacity (e.g., SOC dropping to 95%) via the energy storage converter, before restarting the photovoltaic MPPT operation. The second method involves charging the battery to near full charge (e.g., SOC reaching 95%), then adjusting the photovoltaic output power to match load demand. However, both methods have significant drawbacks: the former releases capacity through frequent charge-discharge cycles, causing unnecessary battery aging and reducing lifespan, while also interrupting photovoltaic power generation and affecting overall energy efficiency; the latter sacrifices the battery's effective energy storage capacity and places extremely high demands on the real-time adjustment accuracy and response speed of photovoltaic power. If the load fluctuates drastically or control is delayed, it can still lead to excess energy and a rise in DC bus voltage, ultimately forcing the system into passive protection mode or even causing battery overcharging.

[0042] In one exemplary manner, please refer to Figure 5A photovoltaic energy storage system includes a battery system, photovoltaic modules, a photovoltaic converter, an energy storage inverter, and a battery system. The battery system includes a fuse FUSE2, a shunt FL2, contactors KM5, KM6, and KM7, a resistor R2, a double-pole circuit breaker QF2, and a battery pack. When the battery system is fully charged, if the photovoltaic system continues to generate electricity and the load cannot absorb it or the load fluctuation suddenly decreases, energy may be poured into the battery system. At this time, the battery system voltage rises. Even with precise control of the photovoltaic converter's power, repeated occurrences can still lead to battery overcharging, triggering overvoltage protection. In this circuit, the DC bus voltage regulation relies on the battery system. Once the battery system is in overvoltage protection mode, the photovoltaic energy storage system will shut down. Existing solutions mainly include two approaches: one is to release a portion of the battery pack's charge (e.g., 5%) by reducing the photovoltaic converter's power to zero after the battery system is fully charged, thereby lowering the battery pack voltage, and then activating the photovoltaic system to track the power required by the load. In this case, even if the photovoltaic power is uncontrollable, the battery pack will not be overcharged after repeated cycles. The other approach is to charge the battery pack to near full capacity (e.g., 95%) and then control the photovoltaic power to follow the load. However, both of these solutions reduce the battery's backup SOC / battery charging capacity, which not only affects the photovoltaic power generation but also places extremely high demands on the precision of photovoltaic power control. If this continues for a long time, there is still a risk of battery overcharging.

[0043] This invention proposes a DC-coupled photovoltaic energy storage system.

[0044] Please see Figure 1 In one embodiment of this utility model, the DC-coupled photovoltaic energy storage system includes:

[0045] Battery pack 10;

[0046] Photovoltaic module 20 is used to convert solar energy into DC power output;

[0047] The photovoltaic converter 30 is connected to the photovoltaic module 20 and is used to convert the DC power output from the photovoltaic module 20 into voltage and output it.

[0048] The energy storage converter 40 is connected to the photovoltaic converter 30 and the mains power respectively. The energy storage converter 40 is used to convert the DC power output of the photovoltaic converter 30 and / or the battery pack 10 into AC power output, or to convert the mains power into the charging power output required by the battery pack 10.

[0049] The charge / discharge control circuit 50 is connected to the battery pack 10, the photovoltaic converter, and the energy storage inverter 40, respectively, and is used to control the charging / discharging of the battery pack 10; wherein, the charge / discharge control circuit 50 includes a first electronic switch KM1, a second electronic switch KM2, a first diode D1, and a second diode D2;

[0050] The first terminal of the first electronic switch KM1, the positive terminal of the first diode D1, the positive output terminal of the photovoltaic converter 30 are connected to the positive terminal of the DC power supply of the energy storage converter 40. The second terminal of the first electronic switch KM1, the first terminal of the second electronic switch KM2, the negative terminal of the first diode D1 are connected to the negative terminal of the second diode D2. The second terminal of the second electronic switch KM2 and the positive terminal of the second diode D2 are connected to the positive terminal of the battery pack 10.

[0051] The detection and control module (not shown in the figure) is connected to the battery pack 10, the photovoltaic converter 30, the controlled terminal of the first electronic switch KM1, and the controlled terminal of the second electronic switch KM2. The detection and control module is used to detect the power generation of the photovoltaic converter 30 and the state of charge of the battery pack 10, and control the operation of the first electronic switch KM1 and the second electronic switch KM2 according to the power generation of the photovoltaic converter 30, the power required by the electrical load, and the state of charge of the battery pack 10.

[0052] It should be noted that the battery pack 10 can be a lithium-ion battery pack 10, such as a lithium-ion battery pack 10 composed of multiple lithium iron phosphate battery packs 10. The photovoltaic module 20 can be a photovoltaic panel composed of multiple solar cells connected in series and encapsulated, such as a monocrystalline silicon, polycrystalline silicon, or thin-film module, used to absorb solar energy and output DC power, with voltage and current varying with light intensity. The photovoltaic converter 30 can be a DC-DC converter with MPPT (maximum power point tracking) function, which can extract the maximum available power from the photovoltaic module 20 and output an adjustable DC voltage to meet the charging needs of the downstream energy storage converter 40 or the battery. The energy storage converter 40 is a bidirectional DC-AC converter. The DC terminal of the bidirectional DC-AC converter is connected to the output terminal of the photovoltaic converter 30, and the AC terminal of the bidirectional DC-AC converter is connected to the mains power and the electrical load respectively. It can convert DC power to AC power for output to the mains power and the electrical load, and rectify the input mains power into DC power to charge the battery pack 10. The charge / discharge control circuit 50 includes a first electronic switch KM1, a second electronic switch KM2, a first diode D1, and a second diode D2. The first electronic switch KM1 and the second electronic switch KM2 can be switching elements such as contactors and relays, or controllable semiconductor switches such as MOSFETs and IGBTs; no limitation is made here. The photovoltaic module 20, the energy storage converter 40, and the charge / discharge control circuit 50 can be connected via a DC bus. The detection and control module can include a microcontroller (MCU), a digital signal processor (DSP), or a field-programmable gate array (FPGA), as well as signal acquisition devices including current sensors and voltage sensors. It can detect the operating status of the photovoltaic converter 30 and the battery pack 10, and control the on / off operation of the first electronic switch KM1 and the second electronic switch KM2.

[0053] Understandably, the detection and control module can also be used to control the operation of the photovoltaic converter 30 and the energy storage converter 40. In one embodiment, the detection and control module can collect the output voltage and output current of the photovoltaic array in real time, calculate its current output power, and execute a maximum power point tracking (MPPT) algorithm (such as the perturbation observation method, incremental conductance method, etc.). Based on the calculation results of the MPPT algorithm, the detection and control module dynamically generates a pulse width modulation (PWM) signal to adjust the on and off duty cycles of the switching devices (such as MOSFETs or IGBTs) inside the photovoltaic converter 30, so that the photovoltaic array always operates near the maximum power point, thereby maximizing the utilization efficiency of solar energy. In another embodiment, the detection and control module can determine the operating mode and power command of the energy storage converter 40 based on a preset energy dispatch strategy (such as peak-valley electricity pricing mechanism, load power requirements, photovoltaic converter 30 power generation, etc.), send active power control commands / reactive power control commands and voltage / frequency setpoints to the energy storage converter 40, and control the on / off switching of its internal power electronic switching devices to realize bidirectional energy conversion between DC and AC within the energy storage converter 40. When operating in grid-connected mode, it ensures that the AC power output by the energy storage converter 40 maintains the same frequency, phase, and amplitude as the mains voltage, or ensures that the mains power is converted into the charging power required by the battery pack 10, charging the battery pack 10 simultaneously with photovoltaic power generation. When operating off-grid, it converts the DC power output by the photovoltaic converter 30 and / or the battery pack 10 into AC power to supply power to local electrical loads.

[0054] In this embodiment, the detection and control module can detect the power output of the photovoltaic converter 30 and the state of charge (SOC) of the battery pack 10, and control the operation of the first electronic switch KM1 and the second electronic switch KM2 based on the power output of the photovoltaic converter 30, the power required by the electrical load, and the SOC of the battery pack 10. It should be noted that the power required by the electrical load can be preset or obtained from the electrical load; no limitation is made here. Specifically, when the power output of the photovoltaic converter 30 is detected to be greater than the power required by the load, the photovoltaic power generation charges the battery pack 10. After the SOC of the battery pack 10 is detected to be fully charged, the second electronic switch KM2 is controlled to open, stopping charging. At this time, the first electronic switch KM1 and the second diode D2 are conducting, still stabilizing the DC bus voltage, while external current cannot flow into the battery pack 10 through the first diode D1, ensuring a stable state where the DC bus voltage is regulated and the battery pack 10 is not overcharged. At this time, the detection and control module can control the photovoltaic converter 30 to continue tracking the power required by the load and continuously output power, maximizing the consumption of photovoltaic power generation. This embodiment does not place much emphasis on the control precision of the photovoltaic converter 30; even if the photovoltaic converter 30 is improperly controlled, it will only raise the bus voltage, and the photovoltaic energy storage system will not shut down due to overvoltage protection of the battery pack 10. When the power output of the photovoltaic converter 30 is detected to be less than the power required by the load or when the mains power fails (the mains voltage is less than the preset minimum voltage, at which point the mains power supply to the load is insufficient), the first electronic switch KM1 is controlled to be closed. If the detection and control module detects battery discharge, it immediately controls the second electronic switch KM2 to close and enter the discharge mode. At this time, the battery pack 10 directly discharges to the load, preventing the first diode D1 from overheating due to prolonged discharge. When the power output of the photovoltaic converter 30 is detected to be greater than the power required by the load or when the mains power is restored (the mains voltage is greater than or equal to the preset minimum voltage, at which point the mains power supply to the load is sufficient), the battery pack 10 is recharged until the battery pack 10 is detected to be fully charged, at which point the second electronic switch KM2 is controlled to open and charging is stopped. Thus, in this embodiment, the battery pack 10 can reach a fully charged state during photovoltaic energy storage without needing to discharge to prevent overcharging. When backup power is needed, it can still instantly enter discharge mode, ensuring off-grid backup power requirements. Compared with existing technologies, this embodiment can prevent overcharging of the battery pack 10 and avoids frequent interruptions to photovoltaic power supply or limiting the full charge of the battery pack, thereby maximizing the utilization of photovoltaic energy.

[0055] Please see Figure 2 In one embodiment of the present invention, the charge and discharge control circuit 50 further includes a third electronic switch KM3 and a first resistor R1;

[0056] The first terminal of the third electronic switch KM3 is connected to the first terminal of the first electronic switch KM1, the second terminal of the third electronic switch KM3 is connected to one end of the first resistor R1, and the other end of the first resistor R1 is connected to the second terminal of the second electronic switch KM2.

[0057] It should be noted that capacitors are present inside the photovoltaic converter 30 and the energy storage converter 40. In this embodiment, upon initial power-on, the third electronic switch KM3 is first closed to reduce the current in the circuit through the first resistor R1 and to fully charge the capacitors in the photovoltaic converter 30 and the energy storage converter 40. Then, the first electronic switch KM1 and the second electronic switch KM2 are closed, and the third electronic switch KM3 is opened to charge the battery pack 10. In this way, the first electronic switch KM1 and the second electronic switch KM2 will not be closed with a large current, which could cause them to stick together.

[0058] Please see Figure 2 In one embodiment of this utility model, one or more of the first electronic switch KM1, the second electronic switch KM2 and the third electronic switch KM3 are contactors.

[0059] In this embodiment, the contactor has a high rated current and voltage withstand capability, and is suitable for controlling the on / off of high-power loads such as photovoltaic converter 30 and battery pack 10, ensuring the stability and safety of the system under high power operation.

[0060] Please see Figure 2 In one embodiment of the present invention, the charge and discharge control circuit 50 further includes a first fuse FUSE1, a first shunt FL1 and a fourth electronic switch KM4;

[0061] In this circuit, one end of the first fuse FUSE1 is connected to the second end of the second electronic switch KM2, and the other end of the first fuse FUSE1 is connected to the positive terminal of the battery pack 10. One end of the first shunt FL1 is connected to the negative terminal of the battery pack 10, and the other end of the first shunt FL1 is connected to the second end of the fourth electronic switch KM4. The first end of the fourth electronic switch KM4 and the negative output terminal of the photovoltaic converter 30 are connected to the negative DC power supply terminal of the energy storage converter 40. The signal output terminal of the first shunt FL1 is connected to the detection and control module, and the controlled terminal of the fourth electronic switch KM4 is connected to the detection and control module.

[0062] In this embodiment, the first fuse FUSE1 can automatically blow when the charging / discharging current of the battery pack 10 exceeds the rated value, cutting off the circuit to prevent overcurrent damage. The first shunt FL1 is used to measure the current flowing through the battery pack 10 and convert the current information into a voltage signal, which is then output to the detection and control module. The detection and control module can acquire the current detection signal output by the first shunt FL1. When the charging / discharging current flowing through the first shunt FL1 is greater than a preset current threshold, it indicates an overcurrent risk. The detection and control module then controls the fourth electronic switch KM4 to open, quickly cutting off the circuit and improving circuit safety.

[0063] Please see Figure 2 In one embodiment of the present invention, the DC-coupled photovoltaic energy storage system further includes a first bipolar circuit breaker QF1;

[0064] The first terminal of the first bipolar circuit breaker QF1 is connected to the first terminal of the first electronic switch KM1. The second terminal of the first bipolar circuit breaker QF1 and the positive output terminal of the photovoltaic converter 30 are connected to the positive DC power supply terminal of the energy storage converter 40. The third terminal of the first bipolar circuit breaker QF1 is connected to the first terminal of the fourth electronic switch KM4. The fourth terminal of the first bipolar circuit breaker QF1 and the negative output terminal of the photovoltaic converter 30 are connected to the negative DC power supply terminal of the energy storage converter 40. The controlled terminal of the first bipolar circuit breaker QF1 is connected to the detection and control module.

[0065] In this embodiment, the detection and control module can control the battery pack 10 to disconnect all poles through the first bipolar circuit breaker QF1, which can simultaneously disconnect the positive and negative DC circuits, completely cut off the electrical connection between the battery pack 10 and the photovoltaic module 20 and the energy storage converter 40, avoid the safety hazards caused by the negative pole still being charged when disconnecting one pole, effectively prevent the risk of DC side arcing, leakage or short circuit, and significantly improve personal safety during maintenance and repair.

[0066] Please see Figure 3 In one embodiment of the present invention, the photovoltaic converter 30 includes a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, a sixth switch Q6, a seventh switch Q7, an eighth switch Q8, a first capacitor C1, a second capacitor C2, a first inductor L1, a second inductor L2, a third inductor L3, and a fourth inductor L4.

[0067] Specifically, the first terminal of the first switch Q1, the first terminal of the fifth switch Q5, and one terminal of the first capacitor C1 are connected to the positive output terminal of the photovoltaic converter 30; the second terminal of the first switch Q1 and the first terminal of the second switch Q2 are connected to one terminal of the second inductor L2; the second terminal of the second switch Q2 is connected to the first terminal of the third switch Q3; the second terminal of the third switch Q3 and the first terminal of the fourth switch Q4 are connected to one terminal of the fourth inductor L4; the second terminal of the fourth switch Q4, the second terminal of the eighth switch Q8, and one terminal of the second capacitor C2 are connected to the negative output terminal of the photovoltaic converter 30; the second terminal of the fifth switch Q5 and the first terminal of the sixth switch Q6 are connected to one terminal of the first inductor L1; the second terminal of the sixth switch Q6 is connected to the first terminal of the seventh switch Q7; the second terminal of the seventh switch Q7 and the first terminal of the eighth switch Q8 are connected to one terminal of the third inductor L3; and the other terminals of the first inductor L1, the second inductor L2, the third inductor L3, and the fourth inductor L4 are connected to the photovoltaic module 20.

[0068] In one embodiment, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, the fifth switch Q5, the sixth switch Q6, the seventh switch Q7, and the eighth switch Q8 are all MOSFETs with anti-integrated parallel diodes.

[0069] In this embodiment, the control terminals of the first to eighth switches Q1 can be connected to the detection and control module. It is understood that in another embodiment, a separate first controller can be used to control the switches; this is not a limitation here. In this embodiment, the detection and control module can generate multiple pulse width modulation (PWM) signals according to the transformer requirements. Following the drive logic of the full-bridge converter, it controls the switching of the switches in a diagonal conduction and complementary turn-off manner, and sets necessary dead time to prevent bridge arm shoot-through. By periodically alternating the switching of the switches, the first to fourth inductors L4 sequentially store and release energy at different switching stages, achieving continuous energy transfer from the photovoltaic module 20 to the DC bus, completing the DC voltage rise and fall conversion. Furthermore, the detection and control module can integrate a maximum power point tracking (MPPT) algorithm to detect the output voltage and current of the photovoltaic module 20 in real time, calculate its output power, and dynamically change the input equivalent load of the photovoltaic converter by adjusting the duty cycle of the PWM signal, ensuring that the operating point of the photovoltaic module 20 always approaches the maximum power point under the current light and temperature conditions, thereby improving the overall power generation efficiency of the photovoltaic energy storage system. Among them, the first capacitor C1 and the second capacitor C2 together constitute the filter capacitor of the DC bus, which can help maintain the voltage stability of the DC bus.

[0070] Please see Figure 4In one embodiment of this utility model, the energy storage converter 40 includes a third capacitor C3, a fourth capacitor C4 and a three-phase conversion branch; each phase conversion branch includes a ninth switch Q9, a tenth switch Q10, an eleventh switch Q11, a twelfth switch Q12, a third diode D3 and a fourth diode D4;

[0071] In this circuit, one end of the third capacitor C3 and the second end of the ninth switch Q9 are connected to the positive terminal of the DC power supply of the energy storage converter 40; the other end of the third capacitor C3, one end of the fourth capacitor C4, and the positive terminal of the third diode D3 are connected to the negative terminal of the fourth diode D4; the first end of the ninth switch Q9 and the second end of the tenth switch Q10 are connected to the negative terminal of the third diode D3; the first end of the tenth switch Q10 and the second end of the eleventh switch Q11 are connected to the power supply terminal of a phase switching branch; the first end of the eleventh switch Q11 and the second end of the twelfth switch Q12 are connected to the positive terminal of the fourth diode D4; and the other end of the fourth capacitor C4 and the first end of the twelfth switch Q12 are connected to the negative terminal of the DC power supply of the energy storage converter 40.

[0072] Among them, the ninth switch Q9, the tenth switch Q10, the eleventh switch Q11 and the twelfth switch Q12 are all MOSFETs with anti-integrated parallel diodes.

[0073] In one embodiment, the energy storage converter 40 further includes a fifth inductor L5, a sixth inductor L6, a seventh inductor L7, an eighth inductor L8, a ninth inductor L9, a tenth inductor L10, a fifth capacitor C5, a sixth capacitor C6, and a seventh capacitor C7.

[0074] Among them, one end of the seventh inductor L7 is connected to the power supply terminal of the first phase conversion branch, one end of the sixth inductor L6 is connected to the power supply terminal of the second phase conversion branch, one end of the fifth inductor L5 is connected to the power supply terminal of the third phase conversion branch, the other end of the seventh inductor L7, one end of the sixth capacitor C6, one end of the seventh capacitor C7 are connected to one end of the tenth inductor L10, the other end of the sixth inductor L6, one end of the fifth capacitor C5, one end of the sixth capacitor C6 are connected to one end of the ninth inductor L9, the other end of the fifth inductor L5, the other end of the fifth capacitor C5, the other end of the seventh capacitor C7 are connected to one end of the eighth inductor L8, and the other end of the eighth inductor L8, the other end of the ninth inductor L9, and the other end of the tenth inductor L10 are used to connect to the mains power.

[0075] In this embodiment, the controlled terminals of the ninth to twelfth switches Q9 to Q12 of the three-phase conversion branch can be connected to the detection and control module. It is understood that in another embodiment, a second controller can also be provided for switching control; this is not a limitation here. In this embodiment, the detection and control module can employ a space vector pulse width modulation algorithm to generate multiple PWM signals based on active power control commands / reactive power control commands and control signals such as voltage setpoints / frequency setpoints to drive the ninth to twelfth switches Q9 to Q12. This controls the switches in the three-phase conversion branch to periodically and alternately turn on and off, converting DC power to three-phase power output, or rectifying three-phase power to DC voltage output. Each phase conversion branch in the three-phase conversion branch is independent, with a 120° electrical angle difference between the three phases. In this embodiment, the third capacitor C3 and the fourth capacitor C4 together constitute the DC bus filter capacitor, which helps maintain the voltage stability of the DC bus. The fifth inductor L5 to the tenth inductor L10, and the fifth capacitor C5 to the seventh capacitor C7 constitute the LC filter network of the three-phase conversion branch output. This network can filter out switching noise, ensure that the AC side output current is close to a sine wave, and help achieve safe grid connection with the mains power.

[0076] The above description is merely an exemplary embodiment of the present utility model and does not limit the patent scope of the present utility model. Any equivalent structural transformations made based on the technical concept of the present utility model and the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present utility model.

Claims

1. A DC-coupled photovoltaic energy storage system, characterized in that, include: Battery pack; Photovoltaic modules are used to convert solar energy into direct current power output. A photovoltaic converter, connected to the photovoltaic module, is used to convert the DC power output from the photovoltaic module into voltage and then output it. An energy storage converter is connected to both the photovoltaic converter and the mains power. The energy storage converter is used to convert the DC power output from the photovoltaic converter and / or the battery pack into AC power output, or to convert the mains power into the charging power output required by the battery pack. A charge / discharge control circuit is connected to the battery pack, the photovoltaic converter, and the energy storage converter, respectively, and is used to control the charging / discharging of the battery pack; wherein, the charge / discharge control circuit includes a first electronic switch, a second electronic switch, a first diode, and a second diode; The first terminal of the first electronic switch, the positive terminal of the first diode, and the positive output terminal of the photovoltaic converter are connected to the positive terminal of the DC power supply of the energy storage converter. The second terminal of the first electronic switch, the first terminal of the second electronic switch, the negative terminal of the first diode, and the negative terminal of the second diode are connected to the negative terminal of the second diode. The second terminal of the second electronic switch and the positive terminal of the second diode are connected to the positive terminal of the battery pack. A detection and control module is connected to the battery pack, the photovoltaic converter, the controlled terminal of the first electronic switch, and the controlled terminal of the second electronic switch. The detection and control module is used to detect the power generation of the photovoltaic converter and the state of charge of the battery pack, and control the operation of the first electronic switch and the second electronic switch according to the power generation of the photovoltaic converter, the power required by the electrical load, and the state of charge of the battery pack.

2. The DC-coupled photovoltaic energy storage system as described in claim 1, characterized in that, The charge / discharge control circuit also includes a third electronic switch and a first resistor; The first end of the third electronic switch is connected to the first end of the first electronic switch, the second end of the third electronic switch is connected to one end of the first resistor, and the other end of the first resistor is connected to the second end of the second electronic switch.

3. The DC-coupled photovoltaic energy storage system as described in claim 2, characterized in that, One or more of the first electronic switch, the second electronic switch and the third electronic switch are contactors.

4. The DC-coupled photovoltaic energy storage system as described in claim 1, characterized in that, The charge and discharge control circuit also includes a first fuse, a first shunt and a fourth electronic switch; In this configuration, one end of the first fuse is connected to the second end of the second electronic switch, and the other end of the first fuse is connected to the positive terminal of the battery pack. One end of the first shunt is connected to the negative terminal of the battery pack, and the other end of the first shunt is connected to the second end of the fourth electronic switch. The first end of the fourth electronic switch and the negative output terminal of the photovoltaic converter are connected to the negative DC power supply terminal of the energy storage converter. The signal output terminal of the first shunt is connected to the detection and control module, and the controlled terminal of the fourth electronic switch is connected to the detection and control module.

5. The DC-coupled photovoltaic energy storage system as described in claim 4, characterized in that, It also includes the first double-pole circuit breaker; The first terminal of the first bipolar circuit breaker is connected to the first terminal of the first electronic switch. The second terminal of the first bipolar circuit breaker and the positive output terminal of the photovoltaic converter are connected to the positive DC power supply terminal of the energy storage converter. The third terminal of the first bipolar circuit breaker is connected to the first terminal of the fourth electronic switch. The fourth terminal of the first bipolar circuit breaker and the negative output terminal of the photovoltaic converter are connected to the negative DC power supply terminal of the energy storage converter. The controlled terminal of the first bipolar circuit breaker is connected to the detection and control module.

6. The DC-coupled photovoltaic energy storage system as described in claim 1, characterized in that, The photovoltaic converter includes a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a first capacitor, a second capacitor, a first inductor, a second inductor, a third inductor, and a fourth inductor; In this configuration, the first end of the first switch, the first end of the fifth switch, and one end of the first capacitor are connected to the positive output terminal of the photovoltaic converter; the second end of the first switch and the first end of the second switch are connected to one end of the second inductor; the second end of the second switch is connected to the first end of the third switch; the second end of the third switch and the first end of the fourth switch are connected to one end of the fourth inductor; the second end of the fourth switch, the second end of the eighth switch, and one end of the second capacitor are connected to the negative output terminal of the photovoltaic converter; the second end of the fifth switch and the first end of the sixth switch are connected to one end of the first inductor; the second end of the sixth switch is connected to the first end of the seventh switch; the second end of the seventh switch and the first end of the eighth switch are connected to one end of the third inductor; and the other ends of the first inductor, the second inductor, the third inductor, and the fourth inductor are connected to the photovoltaic module.

7. The DC-coupled photovoltaic energy storage system as described in claim 6, characterized in that, The first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, and the eighth switch are all MOSFETs with anti-integrated parallel diodes.

8. The DC-coupled photovoltaic energy storage system as described in claim 1, characterized in that, The energy storage converter includes a third capacitor, a fourth capacitor, and a three-phase conversion branch; each phase of the conversion branch includes a ninth switch, a tenth switch, an eleventh switch, a twelfth switch, a third diode, and a fourth diode; Specifically, one end of the third capacitor and the second end of the ninth switch are connected to the positive terminal of the DC power supply of the energy storage converter; the other end of the third capacitor, one end of the fourth capacitor, the positive terminal of the third diode, and the negative terminal of the fourth diode are connected; the first end of the ninth switch and the second end of the tenth switch are connected to the negative terminal of the third diode; the first end of the tenth switch and the second end of the eleventh switch are connected to the power supply terminal of one phase of the switching branch; the first end of the eleventh switch and the second end of the twelfth switch are connected to the positive terminal of the fourth diode; and the other end of the fourth capacitor and the first end of the twelfth switch are connected to the negative terminal of the DC power supply of the energy storage converter.

9. The DC-coupled photovoltaic energy storage system as described in claim 8, characterized in that, The ninth, tenth, eleventh, and twelfth switching transistors are all MOS transistors with anti-integrated parallel diodes.

10. The DC-coupled photovoltaic energy storage system as described in claim 8, characterized in that, The energy storage converter also includes a fifth inductor, a sixth inductor, a seventh inductor, an eighth inductor, a ninth inductor, a tenth inductor, a fifth capacitor, a sixth capacitor, and a seventh capacitor; Wherein, one end of the seventh inductor is connected to the power supply terminal of the first phase conversion branch, one end of the sixth inductor is connected to the power supply terminal of the second phase conversion branch, one end of the fifth inductor is connected to the power supply terminal of the third phase conversion branch, the other end of the seventh inductor, one end of the sixth capacitor, one end of the seventh capacitor are connected to one end of the tenth inductor, the other end of the sixth inductor, one end of the fifth capacitor, one end of the sixth capacitor are connected to one end of the ninth inductor, the other end of the fifth inductor, the other end of the fifth capacitor, the other end of the seventh capacitor are connected to one end of the eighth inductor, and the other end of the eighth inductor, the other end of the ninth inductor, and the other end of the tenth inductor are used to connect to the mains power.

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