Photovoltaic disconnect device for a light storage device

Abstract

The application discloses a photovoltaic disconnection device of a light storage device, relates to the technical field of light storage devices, and solves the problem that a photovoltaic switch is difficult to reliably disconnect when auxiliary power supply fails. The device comprises a power supply unit, an energy storage unit, a voltage conversion unit, a sampling unit, a control unit, a driving unit and a photovoltaic switch. The power supply unit has a first power supply branch connected with the energy storage battery and a second power supply branch connected with a direct-current bus, and respectively provides a backup energy storage power supply voltage and a main energy storage power supply voltage to the energy storage unit; the second power supply branch also outputs a control power supply voltage; when the control power supply voltage is reduced, a backup power supply voltage output by the energy storage unit is used to maintain sampling, control and disconnection, so that the electrical connection between the photovoltaic module and the main power circuit can still be disconnected when the polarity of the photovoltaic input is reversely connected or the direct-current bus is short-circuited.

Description

Technical Field

[0001] This application relates to the field of photovoltaic energy storage equipment technology, and in particular to a photovoltaic disconnection device for photovoltaic energy storage equipment. Background Technology

[0002] With the development of photovoltaic power generation and energy storage technologies, photovoltaic-energy storage devices that integrate photovoltaic input, energy storage batteries, and inverter functions are widely used. Photovoltaic modules are typically connected to the main power circuit of the inverter via photovoltaic switches. When the inverter experiences abnormal conditions such as bus short circuits or reversed polarity of the photovoltaic input, if the electrical connection between the photovoltaic modules and the main power circuit cannot be disconnected in time, the fault current output by the photovoltaic modules may continue to flow into the equipment, easily causing damage to internal power devices and affecting the operational safety of the photovoltaic-energy storage device.

[0003] An existing photovoltaic interruption scheme is as follows: Figure 1 As shown, a power transistor Q1 is installed in the photovoltaic input branch, and its on / off state is controlled by a control unit and a drive unit. In other implementations, a DC relay can be used instead of the power transistor Q1. This scheme requires the installation of corresponding power switching devices and their drive circuits, increasing losses and occupying a certain amount of circuit board space. Furthermore, its disconnection action depends on the normal power supply of the control circuit. When an inverter failure causes the auxiliary power supply to fail, the photovoltaic disconnection may not be able to continue.

[0004] Another existing photovoltaic interruption scheme is as follows: Figure 2 As shown, a photovoltaic switch (PV SWITCH) with electronic shunt function is used. The control unit and drive unit output a disconnect signal to the PV SWITCH to disconnect the photovoltaic panel from the main power circuit. In this scheme, the control unit and drive unit are still powered by the inverter-side auxiliary power supply. When the auxiliary power supply fails due to bus short circuits, extremely weak light, or other conditions, the control and drive circuits may lose power, thus affecting the reliable disconnection of the PV SWITCH. Furthermore, during the equipment installation phase, if the positive and negative terminals of the photovoltaic input are reversed, there is also a problem of not being able to implement timely disconnection protection.

[0005] Therefore, providing a photovoltaic disconnection solution that can still provide power support for fault detection and PVSWITCH disconnection when the normal auxiliary power supply of the photovoltaic energy storage device fails has become an urgent technical problem to be solved. Summary of the Invention

[0006] The purpose of this application is to provide a photovoltaic disconnection device for photovoltaic energy storage equipment to solve the problem of lack of reliable power supply support for fault detection and photovoltaic switch disconnection when the normal auxiliary power supply of photovoltaic energy storage equipment fails.

[0007] To address the aforementioned technical problems, this application provides a photovoltaic disconnection device for a photovoltaic energy storage system, comprising a power supply unit, an energy storage unit, a voltage conversion unit, a sampling unit, a control unit, a drive unit, and a photovoltaic switch. The photovoltaic switch is connected between the photovoltaic module and the main power circuit of the photovoltaic energy storage system. The power supply unit includes a first power supply branch and a second power supply branch. The first power supply branch is connected to the energy storage battery and outputs a backup energy storage power supply voltage to the energy storage unit via a first unidirectional conduction branch. The second power supply branch is connected to the DC bus of the main power circuit and outputs the main energy storage power supply voltage to the energy storage unit via a second unidirectional conduction branch and a control power supply voltage to the power supply node via a third unidirectional conduction branch. When the main energy storage power supply voltage is lower than the backup energy storage power supply voltage, the first power supply branch... The first unidirectional conduction branch supplies power to the energy storage unit; the energy storage unit outputs backup power supply voltage and connects to the power supply node via the fourth unidirectional conduction branch. The power supply node is connected to the sampling unit and control unit via the voltage conversion unit. When the control power supply voltage is higher than the backup power supply voltage, the second power supply branch supplies power to the sampling unit and control unit. When the control power supply voltage is lower than the backup power supply voltage, the energy storage unit supplies power to the sampling unit and control unit. The power supply terminal of the drive unit is connected to the energy storage unit. The sampling unit collects electrical parameters and outputs sampling signals. The control unit outputs a disconnect command when the photovoltaic input polarity is reversed or the DC bus is short-circuited, based on the sampling signals. The drive unit drives the photovoltaic switch to disconnect the electrical connection between the photovoltaic module and the main power circuit according to the disconnect command.

[0008] Furthermore, the first power supply branch includes a first DC-DC converter, the input terminals of which are connected to the positive and negative terminals of the energy storage battery, respectively; the second power supply branch includes a second DC-DC converter, the input terminals of which are connected to the positive and negative terminals of the DC bus, and the second DC-DC converter has a first output terminal for outputting the main energy storage power supply voltage and a second output terminal for outputting the control power supply voltage.

[0009] Furthermore, the first unidirectional conduction branch includes a first diode, and the second unidirectional conduction branch includes a second diode; the energy storage unit includes a current-limiting resistor and at least one supercapacitor, and the output terminals of the first diode and the second diode are both connected to the supercapacitor through the current-limiting resistor.

[0010] Furthermore, the third unidirectional conduction branch includes a third diode, and the fourth unidirectional conduction branch includes a fourth diode; when the control supply voltage is higher than the backup supply voltage, the third diode conducts and the fourth diode is cut off; when the control supply voltage drops to below the backup supply voltage, the fourth diode conducts and the third diode is cut off.

[0011] Furthermore, the photovoltaic switch includes a shunt trip actuator, and a drive unit is connected to the shunt trip actuator. The drive unit uses the backup power supply voltage output by the energy storage unit to drive the shunt trip actuator to operate, so as to trip and disconnect the photovoltaic switch.

[0012] Furthermore, the sampling unit includes a photovoltaic voltage sampling terminal, which is connected between the photovoltaic switch and the photovoltaic module to collect the photovoltaic voltage of the photovoltaic module and to collect the photovoltaic open-circuit voltage of the photovoltaic module after the photovoltaic switch is turned off.

[0013] Furthermore, the sampling unit is used to collect the bus voltage and photovoltaic current; when the bus voltage is less than the bus voltage threshold and the photovoltaic current is greater than the photovoltaic current threshold, the control unit determines that the photovoltaic input polarity is reversed and outputs a disconnect command to the drive unit.

[0014] Furthermore, the sampling unit is also used to collect bus voltage and bus current; the control unit determines the DC bus short circuit based on the bus voltage and bus current, and outputs a disconnect command to the drive unit; the energy storage unit provides the drive unit with the electrical energy required to drive the photovoltaic switch to trip when the DC bus is short-circuited.

[0015] Furthermore, the sampling unit is also used to collect photovoltaic current, and the control unit obtains the photovoltaic output power based on the photovoltaic voltage and photovoltaic current collected by the sampling unit. When the photovoltaic output power is greater than the first power threshold, the control unit controls the photovoltaic switch to remain closed. When the photovoltaic output power is greater than or equal to the second power threshold and less than or equal to the first power threshold, the control unit maintains the current on / off state of the photovoltaic switch unchanged. When the photovoltaic output power is less than the second power threshold and the duration reaches the preset duration, the control unit outputs a disconnection command to the drive unit to trip and disconnect the photovoltaic switch. The second power threshold is less than the first power threshold.

[0016] Furthermore, after the photovoltaic switch trips and disconnects, the sampling unit collects the photovoltaic open-circuit voltage of the photovoltaic module through the photovoltaic voltage sampling terminal; the control unit determines that the light is restored when the photovoltaic open-circuit voltage reaches the start-up voltage threshold, and the photovoltaic switch remains disconnected after the light is restored until it is manually reset.

[0017] The photovoltaic disconnection device for the photovoltaic-energy storage equipment provided in this application obtains power from the energy storage battery and the DC bus through a first power supply branch and a second power supply branch of the power supply unit, respectively. The second power supply branch provides the main energy storage power to the energy storage unit, while the first power supply branch provides backup energy storage power to the energy storage unit when the main energy storage power supply voltage is lower than the backup energy storage power supply voltage. This ensures that the energy storage unit can continue to obtain power when the DC bus power supply is abnormal, improving the reliability of the energy storage unit's power supply. The control power supply voltage output from the second power supply branch and the backup power supply voltage output from the energy storage unit are respectively connected to the power supply node via unidirectional conducting branches. When the control power supply voltage is higher than the backup power supply voltage, the second power supply branch supplies power to the sampling unit and the control unit; when the control power supply voltage is lower than the backup power supply voltage, the energy storage unit supplies power to the sampling unit and the control unit. This achieves automatic switching between normal power supply and backup power supply, and reduces the mutual interference between different power supply branches through the unidirectional conducting branches. Therefore, when a DC bus short circuit causes an abnormal power supply to the bus side, the energy storage unit can continue to provide the sampling unit, control unit, and drive unit with the electrical energy required for the disconnection process. This allows the sampling unit and control unit to continue collecting electrical parameters and diagnosing faults, and enables the drive unit to drive the photovoltaic switch to disconnect the electrical connection between the photovoltaic module and the main power circuit according to the disconnection command. Furthermore, when the photovoltaic input is in a reverse polarity state, the photovoltaic disconnection can be performed promptly, thereby reducing the risk of power failure in the control and drive circuits due to abnormal power supply, which would prevent the photovoltaic disconnection from being completed. This improves the reliability and safety of the photovoltaic energy storage device in the conditions of reverse polarity photovoltaic input and DC bus short circuit. Attached Figure Description

[0018] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of an existing relay or power transistor disconnection scheme; Figure 2 A schematic diagram of an existing photovoltaic switch disconnection scheme with shunt excitation function; Figure 3 This is a block diagram illustrating the operation of the photovoltaic disconnection device provided in the embodiments of this application. Figure 4 A flowchart illustrating the operation of the photovoltaic disconnection device provided in this application embodiment. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0021] The core of this application is to provide a photovoltaic disconnection device for photovoltaic energy storage equipment.

[0022] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 3 As shown, this embodiment provides a photovoltaic disconnection device for a photovoltaic energy storage device, including a power supply unit, an energy storage unit, a voltage conversion unit, a sampling unit, a control unit, a drive unit, and a photovoltaic switch; the photovoltaic switch is connected between the photovoltaic module and the main power circuit of the photovoltaic energy storage device. The power supply unit includes a first power supply branch and a second power supply branch. The first power supply branch is connected to the energy storage battery and outputs a backup energy storage power supply voltage to the energy storage unit via a first unidirectional conduction branch; the second power supply branch is connected to the DC bus of the main power circuit and outputs the main energy storage power supply voltage to the energy storage unit via a second unidirectional conduction branch and outputs a control power supply voltage to the power supply node via a third unidirectional conduction branch; when the main energy storage power supply voltage is lower than the backup energy storage power supply voltage, the first power supply branch supplies power to the energy storage unit via the first unidirectional conduction branch. The energy storage unit outputs a backup power supply voltage, which is connected to the power supply node via the fourth unidirectional conduction branch. The power supply node is connected to the sampling unit and the control unit via a voltage conversion unit. When the control power supply voltage is higher than the backup power supply voltage, the second power supply branch supplies power to the sampling unit and the control unit; when the control power supply voltage is lower than the backup power supply voltage, the energy storage unit supplies power to the sampling unit and the control unit. The power supply terminal of the drive unit is connected to the energy storage unit. The sampling unit collects electrical parameters and outputs sampling signals. The control unit determines whether the photovoltaic input polarity is reversed or the DC bus is short-circuited based on the sampling signals and outputs a disconnect command. The drive unit drives the photovoltaic switch to disconnect the electrical connection between the photovoltaic module and the main power circuit according to the disconnect command. The photovoltaic module is the photovoltaic panel shown in the diagram.

[0024] This embodiment can be applied to photovoltaic and energy storage devices that integrate photovoltaic input, energy storage battery, and inverter functions. The main power circuit can adopt a two-stage inverter topology, with the photovoltaic modules connected to the main power circuit via a photovoltaic switch. The power supply unit is used to convert the electrical energy from the energy storage battery side or the DC bus side into low-voltage DC power usable by the sampling unit, control unit, and disconnection-related circuits. The first power supply branch corresponds to the backup power source on the energy storage battery side, and the second power supply branch corresponds to the normal power source on the DC bus side. The energy storage unit is used to store electrical energy under normal conditions and provide backup power when the power supply on the DC bus side decreases. The control unit can be composed of a digital signal processor (DSP) and peripheral circuits, used to receive sampling signals, perform status judgments, and output disconnection commands; the sampling unit can collect the voltage and current in the main power circuit; the drive unit is used to convert the disconnection command into an electrical signal that causes the photovoltaic switch to perform a disconnection action.

[0025] Since the first and second power supply branches draw power from the energy storage battery and the DC bus, respectively, the energy storage unit can still obtain power from the energy storage battery even when the DC bus is not yet established, when a short circuit occurs on the DC bus, or when the auxiliary power supply on the bus side decreases. On the other hand, the control supply voltage and backup supply voltage are connected to the power supply node through their respective unidirectional conduction branches, allowing the backup power supply to continue supplying power to the sampling unit and control unit after a drop in normal power supply. Simultaneously, the energy storage unit also provides the drive unit with the power required for photovoltaic switch disconnection. Therefore, even when a fault causes the normal auxiliary power supply to fail, fault detection, status judgment, and disconnection operations still have the necessary power supply conditions.

[0026] Considering that the voltage levels on different power supply sides are generally higher than the operating voltage of the control circuit, this embodiment further defines the two power supply branches based on Embodiment 1. The first power supply branch includes a first DC-DC converter, the input terminals of which are connected to the positive and negative terminals of the energy storage battery, respectively; the second power supply branch includes a second DC-DC converter, the input terminals of which are connected to the positive and negative terminals of the DC bus, respectively. The second DC-DC converter has a first output terminal for outputting the main energy storage power supply voltage and a second output terminal for outputting the control power supply voltage.

[0027] The first and second DC-DC converters can be DC-DC converters (DC / DC converters). Figure 3In one implementation shown, the first DC-DC converter, denoted as DC / DC1, has its inputs connected to the positive terminal BAT+ and the negative terminal BAT- of the energy storage battery. Its output backup energy storage supply voltage can be 12V, corresponding to BAT_12V in the figure. The second DC-DC converter, denoted as DC / DC2, has its inputs connected to the positive terminal BUS+ and the negative terminal BUS- of the DC bus. Its first output terminal can output a 12V main energy storage supply voltage, corresponding to BUS_12V in the figure, and its second output terminal can output a 15V control supply voltage, corresponding to DSP_15V in the figure. The DC-DC conversion section of the power supply unit can use a flyback power supply or other DC-DC conversion methods capable of performing the corresponding voltage conversion. The 12V and 15V mentioned above are only examples; other suitable voltage levels can be used depending on the power of the photovoltaic energy storage device and the operating voltage requirements of the devices.

[0028] When both power sources may exist, it is necessary to limit the reverse current between different power sources and prioritize maintaining the energy storage state of the energy storage unit when the bus side is supplying power normally. Based on this, this embodiment proposes, based on the above embodiment: the first unidirectional conduction branch includes a first diode D1, and the second unidirectional conduction branch includes a second diode D2; the energy storage unit includes a current-limiting resistor and at least one supercapacitor, and the output terminals of the first diode D1 and the second diode D2 are both connected to the supercapacitor through the current-limiting resistor.

[0029] like Figure 3 As shown, the first diode D1 and the second diode D2 correspond to the unidirectional power supply paths on the energy storage battery side and the DC bus side, respectively. The current-limiting resistor corresponds to R1, and the supercapacitors can be C1 and C2. The first diode D1 and the second diode D2 enable the two power supplies to supply power to the energy storage unit according to their respective output voltages, and prevent the energy storage unit or one power supply from feeding power back to the other. The current-limiting resistor is used to limit the charging current during the initial charging of the supercapacitor. Although... Figure 3 Two supercapacitors are shown, but the number of supercapacitors can be determined based on the backup power duration and the energy required for interruption; a single supercapacitor can also be used. Using diodes and current-limiting resistors to complete the dual energy storage power supply eliminates the need for a separate charging management chip, thereby reducing the number of external components.

[0030] Under one operating condition, when the DC bus is established normally, the main energy storage supply voltage replenishes the supercapacitor with power. During the installation and commissioning phase, when the DC bus has not yet been established but the energy storage battery has been connected, the backup energy storage supply voltage pre-charges the supercapacitor. Thus, backup power supply conditions can be established in advance during the installation phase.

[0031] Furthermore, considering that the electrical energy in the energy storage unit should be prioritized for fault detection and disconnection processes after a drop in normal auxiliary power supply, this embodiment proposes, based on the above embodiment, that: the third unidirectional conduction branch includes a third diode D3, and the fourth unidirectional conduction branch includes a fourth diode D4; when the control supply voltage is higher than the backup supply voltage, the third diode D3 is turned on and the fourth diode D4 is turned off; when the control supply voltage drops to below the backup supply voltage, the fourth diode D4 is turned on and the third diode D3 is turned off.

[0032] exist Figure 3 In one implementation shown, the backup power supply voltage can be 12V, and the control power supply voltage can be 15V. During normal operation, the control power supply voltage is higher than the backup power supply voltage. The sampling unit and control unit are powered by the second power supply branch, and the supercapacitor in the energy storage unit stores energy. When a short circuit on the DC bus causes the control power supply voltage to drop below the backup power supply voltage, the fourth unidirectional conduction branch is activated, and the energy storage unit supplies power to the sampling unit and control unit via the power supply node and voltage conversion unit. The voltage conversion unit can further convert the voltage of the power supply node into low-voltage DC power such as 5V or 3V used by the sampling unit and control unit.

[0033] Under a set of simulated fault conditions, the response time for switching to backup power after a drop in normal power supply can be no greater than 5μs. The backup power supply can maintain the operation of sampling, control, and disconnection-related circuits for no less than 300ms, and the total time for fault judgment and photovoltaic switch disconnection can be controlled within 30ms. The above time data is used to illustrate the implementation results under one prototype condition and does not limit the values ​​of other device parameters. In another comparative condition, compared with setting a continuously operating independent backup power supply, this embodiment uses the control supply voltage to power the control system during normal operation, and the energy storage unit maintains energy storage, which can reduce standby power consumption by approximately 8W to 12W.

[0034] Considering that fault isolation requires physical disconnection, this embodiment proposes, based on the above embodiment, that: the photovoltaic switch includes a shunt trip actuator, the drive unit is connected to the shunt trip actuator, and the drive unit uses the backup power supply voltage output by the energy storage unit to drive the shunt trip actuator to operate, so as to trip and disconnect the photovoltaic switch.

[0035] The photovoltaic switch can be a photovoltaic switch with electronic shunt trip function. After the control unit outputs a disconnect command, the drive unit outputs an electrical signal to the shunt trip actuator to activate it. The shunt trip actuator then switches the photovoltaic switch from a closed state to an open state, thereby cutting off the electrical connection between the photovoltaic module and the main power circuit. Since the power supply terminal of the drive unit is connected to the energy storage unit, the shunt trip actuator still has the electrical energy required to operate when the normal auxiliary power supply decreases.

[0036] In one equipment layout, backup power supply, energy storage switching, and disconnection circuits can be located near the photovoltaic switch module to reduce the occupancy of additional power switching devices and independent auxiliary power supply modules. In contrast, using independent high-power relays and related power supply circuits may increase the printed circuit board (PCB) footprint by approximately 15% to 20%. Under certain material costing conditions, eliminating the high-power relays and independent isolated auxiliary power supplies can reduce the material cost per unit by approximately 40 to 70 yuan.

[0037] When the photovoltaic switch is turned off, if the voltage sampling terminal is located on the main power circuit side, it is difficult to directly obtain the open-circuit voltage of the photovoltaic module. To address this issue, this embodiment proposes, based on the above embodiment, that the sampling unit includes a photovoltaic voltage sampling terminal, which is connected between the photovoltaic switch and the photovoltaic module, for collecting the photovoltaic voltage of the photovoltaic module, and for collecting the photovoltaic open-circuit voltage of the photovoltaic module after the photovoltaic switch is turned off.

[0038] In other words, the photovoltaic voltage sampling terminal is located on the photovoltaic module side of the photovoltaic switch. When the photovoltaic switch is closed, this sampling terminal can obtain the photovoltaic voltage used to determine the illumination status; after the photovoltaic switch is opened, the electrical connection between the main power circuit and the photovoltaic module is cut off, but the sampling terminal is still connected to the photovoltaic module, so it can continue to obtain the photovoltaic open-circuit voltage. This sampling position allows the control unit to determine whether illumination has recovered while the photovoltaic switch remains open.

[0039] To further consider the possibility of reverse polarity of the photovoltaic input during the installation and wiring stage, this embodiment proposes, based on the above embodiment, that: the sampling unit is used to collect the bus voltage and photovoltaic current; when the bus voltage is less than the bus voltage threshold and the photovoltaic current is greater than the photovoltaic current threshold, the control unit determines that the photovoltaic input polarity is reversed and outputs a disconnect command to the drive unit.

[0040] For example, the bus voltage threshold can be denoted as The photovoltaic current threshold is denoted as .

[0041] in, Based on the overall debugging results, a voltage value close to 0 V can be selected in one implementation method. Similarly, based on the overall system debugging results, a current value close to the short-circuit current of the photovoltaic module can be selected in one implementation method. When the bus cannot be established normally and a large current appears in the photovoltaic input branch, the control unit determines that the photovoltaic input polarity is reversed and outputs a disconnect command. During the installation phase, the energy storage battery can first supplement the energy storage unit with power through the first power supply branch, so that the sampling unit and control unit can perform the above detection even when the DC bus has not been established normally.

[0042] Besides the photovoltaic input polarity reversal during the installation phase, a DC bus short circuit may also occur during equipment operation. Based on this, this embodiment proposes, building upon the previous embodiments, that: the sampling unit is also used to collect bus voltage and bus current; the control unit determines a DC bus short circuit based on the bus voltage and bus current and outputs a disconnect command to the drive unit; and the energy storage unit provides the drive unit with the electrical energy required to trip the photovoltaic switch when a DC bus short circuit occurs.

[0043] The control unit can jointly determine a DC bus short circuit based on the bus voltage drop and bus current change. The specific judgment threshold can be determined according to the rated voltage, rated current, and short circuit protection requirements of the main power circuit. A DC bus short circuit may cause a drop in the control supply voltage output by the second power supply branch. At this time, the backup supply voltage output by the energy storage unit supplies power to the power supply node through the fourth unidirectional conduction branch, enabling the sampling unit and control unit to continue operating during the fault. At the same time, the energy storage unit directly provides the power required for the shunt trip to the drive unit.

[0044] In a comparative test, the disconnection scheme without backup power supply may cause the short-circuit current to last for more than 200 ms after the auxiliary power supply fails. With the backup power supply of this embodiment, the bus voltage and bus current can continue to be collected and short-circuit judgment can be completed during the normal power supply decline, and the photovoltaic switch can be disconnected, thereby shortening the duration of photovoltaic short-circuit current.

[0045] Photovoltaic modules may be in a low-light state under conditions such as early morning, evening, cloudy / rainy weather, or cloud cover. If the photovoltaic switch is turned off as soon as the light intensity decreases slightly, the usable weak light energy may not be able to enter the main power circuit; if it is kept closed for a long time in the absence of light or in extremely low light conditions, energy consumption from the energy storage battery to the photovoltaic side may occur. Therefore, this embodiment, based on embodiment 6, proposes that: the sampling unit is also used to collect photovoltaic current, and the control unit obtains the photovoltaic output power based on the photovoltaic voltage and photovoltaic current collected by the sampling unit; when the photovoltaic output power is greater than a first power threshold, the control unit controls the photovoltaic switch to remain closed; when the photovoltaic output power is greater than or equal to a second power threshold and less than or equal to the first power threshold, the control unit maintains the current on / off state of the photovoltaic switch unchanged; when the photovoltaic output power is less than the second power threshold and the duration reaches a preset duration, the control unit outputs a disconnection command to the drive unit, causing the photovoltaic switch to trip and open; wherein, the second power threshold is less than the first power threshold.

[0046] The output power of a photovoltaic system can be obtained using the following formula: ; In the formula, Indicates photovoltaic output power. Indicates photovoltaic voltage. This represents photovoltaic current.

[0047] In one implementation, the first power threshold can correspond to the weak light threshold. The second power threshold can correspond to the extremely weak light threshold. When the photovoltaic output power is higher than the first power threshold, the photovoltaic switch remains closed, and the photovoltaic-storage device can continue to perform maximum power point tracking (MPPT) under low light conditions. When the photovoltaic output power is between the second and first power thresholds, it remains unchanged as a stagnation interval to reduce frequent switching caused by changes in photovoltaic output power near the thresholds. When the photovoltaic output power is lower than the second power threshold and continues for a preset duration, it is determined to be in a no-light or extremely low-light state and the switch is disconnected. In one implementation, the preset duration can be 30 seconds.

[0048] After a photovoltaic (PV) switch trips due to extremely low light conditions, it is necessary to determine whether subsequent light exposure has recovered, while also preventing the control unit from directly reclosing the shunt-triggered PV switch. Based on this, this embodiment proposes, building upon the previous embodiment, that after the PV switch trips, the sampling unit collects the PV open-circuit voltage of the PV module through the PV voltage sampling terminal; the control unit determines that light exposure has recovered when the PV open-circuit voltage reaches the start-up voltage threshold, and the PV switch remains open after light exposure recovers until manually reset.

[0049] Because the photovoltaic voltage sampling terminal is located between the photovoltaic switch and the photovoltaic module, it can continue to obtain the open-circuit voltage of the photovoltaic module even after the photovoltaic switch is turned off. When the photovoltaic open-circuit voltage reaches the start-up voltage threshold, the control unit can generate illumination recovery status information, but does not output an automatic closing command to the photovoltaic switch. After the staff completes the fault diagnosis or confirms the illumination conditions, they can manually reset the photovoltaic switch. This allows the illumination recovery judgment to be distinguished from the actual closing action of the photovoltaic switch.

[0050] Figure 4 This embodiment illustrates a workflow of a photovoltaic disconnection device, demonstrating an execution sequence under conditions of installation, low-light operation, and DC bus short circuit. Figure 4 The process described herein is used to illustrate the judgment relationship between each state. The various units of the device and their connection relationships can still adopt any of the aforementioned embodiments.

[0051] After the photovoltaic and energy storage equipment is installed and connected to the energy storage battery, the first power supply branch can provide backup energy storage power to the energy storage unit, allowing the supercapacitor to pre-store electrical energy. The voltage conversion unit then provides operating voltage to the sampling unit and control unit. After the photovoltaic switch is manually closed, the control unit first determines whether a reverse polarity photovoltaic input has occurred based on the bus voltage and photovoltaic current. If a reverse polarity photovoltaic input is confirmed, a disconnect command is output to trip the photovoltaic switch, allowing staff to troubleshoot wiring faults. After the fault is cleared, the photovoltaic switch is manually reset.

[0052] If the photovoltaic input polarity is not confirmed to be reversed, the photovoltaic voltage and current are sampled to obtain the photovoltaic output power. When the photovoltaic output power is higher than the first power threshold, the photovoltaic switch remains closed, and maximum power point tracking under low light conditions can be performed. When the photovoltaic output power is between the second and first power thresholds, the current state is maintained. When the photovoltaic output power is lower than the second power threshold and remains below it for a preset duration, the control unit outputs a trip command to disconnect the photovoltaic switch. After the photovoltaic switch is disconnected, the photovoltaic open-circuit voltage continues to be sampled. When the photovoltaic open-circuit voltage reaches the start-up voltage threshold, it is determined that illumination has recovered, but the photovoltaic switch remains open until manually reset.

[0053] If the equipment enters normal operation, the control unit continues to determine whether the DC bus is short-circuited based on the bus voltage and bus current. If a DC bus short circuit is not confirmed, normal operation continues; if a DC bus short circuit is confirmed, the control supply voltage of the second power supply branch may drop. The energy storage unit provides backup power to the sampling unit, control unit, and drive unit. The control unit outputs a trip command, causing the photovoltaic switch to trip and disconnect. After the staff completes the troubleshooting and repair, the photovoltaic switch is manually reset.

[0054] The photovoltaic disconnection device for the photovoltaic energy storage equipment provided in this application has been described in detail above. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of this application.

[0055] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A photovoltaic disconnection device for a photovoltaic energy storage system, characterized in that, It includes a power supply unit, an energy storage unit, a voltage conversion unit, a sampling unit, a control unit, a drive unit, and a photovoltaic switch; the photovoltaic switch is connected between the photovoltaic module and the main power circuit of the photovoltaic energy storage device. The power supply unit includes a first power supply branch and a second power supply branch. The first power supply branch is connected to the energy storage battery and outputs a backup energy storage power supply voltage to the energy storage unit through a first unidirectional conduction branch. The second power supply branch is connected to the DC bus of the main power circuit, and outputs the main energy storage power supply voltage to the energy storage unit through the second unidirectional conduction branch and the control power supply voltage to the power supply node through the third unidirectional conduction branch; when the main energy storage power supply voltage is lower than the backup energy storage power supply voltage, the first power supply branch supplies power to the energy storage unit through the first unidirectional conduction branch. The energy storage unit outputs a backup power supply voltage and is connected to the power supply node via the fourth unidirectional conduction branch. The power supply node is connected to the sampling unit and the control unit via the voltage conversion unit. When the control power supply voltage is higher than the backup power supply voltage, the second power supply branch supplies power to the sampling unit and the control unit; when the control power supply voltage is lower than the backup power supply voltage, the energy storage unit supplies power to the sampling unit and the control unit. The power supply terminal of the drive unit is connected to the energy storage unit; the sampling unit collects electrical parameters and outputs sampling signals; the control unit determines, based on the sampling signals, that the photovoltaic input is in a reverse polarity state or the DC bus is in a short circuit state and outputs a disconnection command; the drive unit drives the photovoltaic switch to disconnect the electrical connection between the photovoltaic module and the main power circuit based on the disconnection command.

2. The photovoltaic disconnection device for a photovoltaic energy storage system according to claim 1, characterized in that, The first power supply branch includes a first DC converter, and the input terminals of the first DC converter are respectively connected to the positive and negative terminals of the energy storage battery; The second power supply branch includes a second DC converter. The input terminals of the second DC converter are respectively connected to the positive and negative terminals of the DC bus. The second DC converter has a first output terminal for outputting the main energy storage power supply voltage and a second output terminal for outputting the control power supply voltage.

3. The photovoltaic disconnection device for a photovoltaic energy storage system according to claim 1, characterized in that, The first unidirectional conduction branch includes a first diode, and the second unidirectional conduction branch includes a second diode; The energy storage unit includes a current-limiting resistor and at least one supercapacitor. The output terminals of the first diode and the second diode are both connected to the supercapacitor through the current-limiting resistor.

4. The photovoltaic disconnection device for a photovoltaic energy storage system according to claim 1, characterized in that, The third unidirectional conduction branch includes a third diode, and the fourth unidirectional conduction branch includes a fourth diode; When the control power supply voltage is higher than the backup power supply voltage, the third diode is turned on and the fourth diode is turned off; When the control power supply voltage drops below the backup power supply voltage, the fourth diode turns on and the third diode turns off.

5. The photovoltaic disconnection device for a photovoltaic energy storage system according to claim 1, characterized in that, The photovoltaic switch includes a shunt trip actuator. The drive unit is connected to the shunt trip actuator. The drive unit uses the backup power supply voltage output by the energy storage unit to drive the shunt trip actuator to operate, so as to trip and disconnect the photovoltaic switch.

6. The photovoltaic disconnection device for a photovoltaic energy storage system according to claim 1, characterized in that, The sampling unit includes a photovoltaic voltage sampling terminal, which is connected between the photovoltaic switch and the photovoltaic module. It is used to collect the photovoltaic voltage of the photovoltaic module and to collect the photovoltaic open-circuit voltage of the photovoltaic module after the photovoltaic switch is turned off.

7. The photovoltaic disconnection device for a photovoltaic energy storage system according to claim 1, characterized in that, The sampling unit is used to collect bus voltage and photovoltaic current; When the bus voltage is less than the bus voltage threshold and the photovoltaic current is greater than the photovoltaic current threshold, the control unit determines that the photovoltaic input polarity is reversed and outputs the disconnect command to the drive unit.

8. The photovoltaic disconnection device for a photovoltaic energy storage system according to claim 1, characterized in that, The sampling unit is also used to collect bus voltage and bus current; The control unit determines that the DC bus is short-circuited based on the bus voltage and the bus current, and outputs the disconnect command to the drive unit; the energy storage unit provides the drive unit with the electrical energy required to trip the photovoltaic switch when the DC bus is short-circuited.

9. The photovoltaic disconnection device for a photovoltaic energy storage device according to claim 6, characterized in that, The sampling unit is also used to collect photovoltaic current, and the control unit obtains photovoltaic output power based on the photovoltaic voltage and photovoltaic current collected by the sampling unit; When the photovoltaic output power is greater than the first power threshold, the control unit controls the photovoltaic switch to remain closed; When the photovoltaic output power is greater than or equal to the second power threshold and less than or equal to the first power threshold, the control unit keeps the current on / off state of the photovoltaic switch unchanged. When the photovoltaic output power is less than the second power threshold and the duration reaches a preset time, the control unit outputs the disconnect command to the drive unit to cause the photovoltaic switch to trip and disconnect. Wherein, the second power threshold is less than the first power threshold.

10. The photovoltaic disconnection device for a photovoltaic energy storage device according to claim 9, characterized in that, After the photovoltaic switch trips and disconnects, the sampling unit collects the photovoltaic open-circuit voltage of the photovoltaic module through the photovoltaic voltage sampling terminal; The control unit determines that the light is restored when the photovoltaic open-circuit voltage reaches the start-up voltage threshold, and the photovoltaic switch remains open after the light is restored until it is manually reset.

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