Photovoltaic rapid turn-off system and control method thereof
By introducing a discharge device into the fast shutdown control box of the photovoltaic fast shutdown system and electrically coupled to the ground, the problem of difficulty in reducing the voltage caused by the failure of the shutdown device to be electrically coupled to the ground in the existing system is solved, and the rapid shutdown and safety improvement of the system is achieved.
Patent Information
- Application Number
- CN202510128954.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-05
- Publication Date
- 2025-05-30
AI Technical Summary
In the existing photovoltaic rapid shutdown system, the shutdown device is not electrically coupled to the ground line, which makes it difficult to quickly reduce the voltage between the DC bus and the ground line during the rapid shutdown process, affecting the rapid shutdown effect and safety of the system.
A photovoltaic fast shutdown system is designed to achieve a rapid reduction in voltage between the DC bus and the ground by introducing a drain device into the fast shutdown control box and electrically coupled with the shutdown device and the ground.
It effectively guarantees the rapid shutdown effect and safety of the system in emergency situations, ensuring that the voltage between the DC bus and the ground line is reduced to below 30V within 30 seconds, and complies with safety specifications.
Smart Images
Figure CN120073631A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of photovoltaic power generation, and particularly to a photovoltaic fast shutdown system and a control method thereof. Background Art
[0002] Photovoltaic power generation systems belong to the high-voltage field in power electronic systems. For safety considerations, the National Fire Protection Association in the United States revised the National Electrical Code, requiring that in residential photovoltaic power generation systems: in case of an emergency, after the AC grid connection port of the photovoltaic power generation system is disconnected, the maximum voltage at the DC end shall not exceed 80 volts. The safety regulations in Italy caution that firefighters cannot carry out fire extinguishing operations when the building is energized. Germany took the lead in implementing fire safety standards and also clearly stipulated that an additional DC cut-off device needs to be added between the inverter and the components in the photovoltaic power generation system. Worldwide, due to safety considerations, even if a fire occurs in a photovoltaic module, fire fighting work is only allowed after all photovoltaic modules are burned out so that they cannot provide a voltage endangering personal safety.
[0003] Taking the US safety standard NECCODE2017 as an example, it requires that photovoltaic power generation systems have a fast shutdown function, and after shutdown, the voltage between the internal conductors of the photovoltaic array and between the conductors and the ground shall not exceed 80 volts. Many power stations' positive measures to cope with safety standards are: to achieve fast shutdown, a shutdown device that plays a shutdown role is installed at the output end of each photovoltaic module, and a command sending device is installed on the battery string or DC bus that provides DC power. The command sending device is mainly powered by the AC grid. When it is necessary to shut down the photovoltaic module, for example, when a hot spot occurs in the photovoltaic module or the photovoltaic junction box is not properly connected, the temperature inside the junction box rises. The coping scheme of shutting down the photovoltaic module can prevent the deterioration of this heat collection phenomenon, thereby improving the reliability and safety of the module. At the same time, the standard NECCODE2017 also requires that when quickly shutting down outside the photovoltaic array, the voltage between any conductors and between any conductor and the ground should be reduced to below 30V within 30s.
[0004] In the existing photovoltaic fast shutdown system, it includes photovoltaic modules, a shutdown device, an inverter, a ground wire, and a power grid, among which the inverter and the ground wire are electrically coupled. In the existing technology, since the shutdown device is not coupled to the ground wire, it is difficult to quickly reduce the voltage from the DC bus to the ground wire during the fast shutdown process, or it is difficult to quickly reduce the common-mode voltage of the system. Summary of the Invention
[0005] In view of the deficiencies of the prior art, the present invention provides a photovoltaic fast shutdown system and its control method, which solve the problems in the prior art that the shutdown device is not electrically coupled to the ground wire, resulting in the inability to rapidly reduce the voltage between the DC bus and the ground wire during the fast shutdown process, or it is difficult to effectively reduce the common-mode voltage of the system, thus affecting the fast shutdown effect and safety of the system.
[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A photovoltaic fast shutdown system includes: a photovoltaic module, a shutdown device, a fast shutdown control box, and an inverter. The photovoltaic module is electrically coupled to the shutdown device. The output end of the shutdown device is connected in series and electrically coupled to the input end of the fast shutdown control box through a DC bus. The output end of the fast shutdown control box is connected to the DC end of the inverter, and the inverter is connected to the power grid. The fast shutdown control box is electrically coupled to the ground wire. The fast shutdown control box internally includes a discharging device, which is used to reduce the voltage between the DC bus and the ground wire during the fast shutdown process.
[0007] Preferably, the fast shutdown control box further includes at least one input line, at least one output line, at least one power input, a power module, and a control module. The power module provides power for the control module and the discharging device. The control module is used to control the operation of the discharging device. The discharging device is electrically coupled to the positive end of the input line and the ground wire, or electrically coupled to the negative end of the input line and the ground wire, or electrically coupled to the positive end and the negative end of the input line, and the power module provides AC power.
[0008] Preferably, the control module controls the operation of the discharging device by receiving signals in the system. The signals include one or more of a fast shutdown signal, the differential-mode voltage value at the input end of the fast shutdown control box, or the common-mode voltage value at the input end of the fast shutdown control box.
[0009] Preferably, the discharging device includes a resistive device and a switching device. The resistive device can be selected from one of a resistor, a resistor in parallel with a capacitor, or a resistor in series with an inductor. The switching device can be selected from one of a relay and its driving circuit, an IGBT and its driving circuit, or a MOSFET and its driving circuit.
[0010] Preferably, the shutdown device is one of a photovoltaic optimizer or a photovoltaic fast shutdown device, which is used to receive and send data through communication. The communication is wireless communication or power line carrier communication.
[0011] Preferably, when the communication module and the shutdown device communicate using the power line carrier method, the fast shutdown control box includes a communication magnetic ring, and the communication magnetic ring is penetrated by the input of the fast shutdown control box and electrically coupled to the communication module.
[0012] Preferably, the fast shutdown control box further includes a sampling module, and the signals sampled by the sampling module include one or more of the input voltage, output voltage, common mode of the input to ground, common mode of the output to ground, input current, output current, and temperature of the fast shutdown control box.
[0013] Preferably, a protection circuit is also connected between the input line and the output line of the fast shutdown control box, and the protection circuit can be a fuse or an air switch.
[0014] A control method for photovoltaic fast shutdown includes the following steps:
[0015] Collect DC bus electrical signals;
[0016] When the electrical signal meets the preset conditions and the fast shutdown signal in the system is detected, drive and control the switching device of the discharge device to form a path, allowing the current in the DC bus to flow through the discharge device to the ground wire, thereby quickly reducing the voltage between the DC bus and the ground wire and ensuring the safety of the system.
[0017] Preferably, when the electrical signal is the voltage signal inside the fast shutdown control box, the discharge device is started when the voltage signal is lower than the first threshold, and the voltage signal can be the input voltage or the common mode voltage of the input to ground of the fast shutdown control box;
[0018] After the fast shutdown signal is detected by collection, after delaying and waiting for the first interval time, control the discharge device to be enabled, and the first interval time is less than 30s.
[0019] The present invention provides a photovoltaic fast shutdown system and its control method. It has the following beneficial effects:
[0020] 1. Through the discharge device inside the fast shutdown control box of the present invention, the current inside the DC bus can be guided out along the ground wire, achieving the effect of quickly reducing the system voltage to a safe level. In an emergency, the discharge device is quickly started to release the excessive voltage to the ground wire, preventing the voltage from continuously rising, thereby effectively ensuring the safety of the system.
[0021] 2. By collecting a variety of electrical signals, the present system can monitor and evaluate the operating state in real time, discover potential faults or abnormalities in advance, so it can respond before problems occur, effectively avoiding system downtime or equipment damage, and improving the stability and reliability of the photovoltaic system. Description of the Drawings
[0022] Figure 1 It is a structural schematic diagram of the present invention;
[0023] Figure 2 It is a schematic diagram of the internal structure of the fast shutdown control box of the present invention;
[0024] Figure 3 This is a schematic structural diagram of the discharge device of the present invention.
[0025] Among them, 101 is a photovoltaic module; 201 is a shut-off device; 301 is an inverter; 401 is a ground wire; 501 is a power grid; 601 is a fast shut-off control box; 602 is a discharge device; 6021 is a resistive device; 6022 is a switching device; 603 is a communication magnetic ring; 604 is a protection circuit. Specific embodiments
[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the specification of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.
[0027] To better understand the present invention, the above content will be described in detail below in conjunction with specific embodiments.
[0028] Please refer to the attached Figure 1 - attached Figure 3 , an embodiment of the present invention provides a photovoltaic fast shut-off system, including: a photovoltaic module 101, a shut-off device 201, a fast shut-off control box 601 and an inverter 301. The photovoltaic module 101 is electrically coupled to the shut-off device 201. The output end of the shut-off device 201 is connected in series and electrically coupled to the input end of the fast shut-off control box 601 through a DC bus. The output end of the fast shut-off control box 601 is connected to the DC end of the inverter 301. The inverter 301 is connected to the power grid 501. The fast shut-off control box 601 is electrically coupled to the ground wire 401. The fast shut-off control box 601 internally includes a discharge device 602, which is used to reduce the voltage between the DC bus and the ground wire 401 during the fast shut-off process.
[0029] In this embodiment, the current generated by the photovoltaic module 101 will flow along the DC bus through the fast shut-off control box 601 and enter the inverter 301. After being inverted into alternating current by the inverter 301, it enters the power grid 501. At this time, the fast shut-off control box 601 is responsible for receiving information from the shut-off device 201 and other monitoring systems, and in an emergency, by controlling the switching device 6022 of the discharge device 602, a path is formed to guide the current in the DC bus to quickly flow to the ground wire 401, thereby quickly reducing the voltage between the DC bus and the ground wire 401, ensuring that the system can quickly reach a safe voltage level in an emergency, and reducing the risk of fire or electrical failure.
[0030] The fast shutdown control box 601 further includes at least one input line, at least one output line, at least one power input, a power module, and a control module. The power module supplies power to the control module and the discharge device 602. The control module is used to control the operation of the discharge device 602. The discharge device 602 is electrically coupled to the positive end of the input line and the ground wire 401, or electrically coupled to the negative end of the input line and the ground wire 401, or electrically coupled to the positive end and the negative end of the input line, and the power module provides an AC power supply. The control module controls the operation of the discharge device 602 by receiving signals in the system. The signals include one or more of a fast shutdown signal, the differential mode voltage value at the input end of the fast shutdown control box 601, or the common mode voltage value at the input end of the fast shutdown control box 601.
[0031] In this embodiment, the input line is connected to the current signal from the photovoltaic module 101 or the shutdown device 201, the output line is connected to the inverter 301, the power module provides an AC power supply and converts it into power suitable for the control module and the discharge device 602. The control module receives signals according to the system state and controls the operation of the discharge device 602. The discharge device 602 is electrically coupled to the positive end, negative end, or positive and negative ends of the input line, so that the voltage can be discharged to the ground wire 401, thereby quickly reducing the system voltage and ensuring system safety. And the control module receives the fast shutdown signal in the system, the differential mode voltage value at the input end of the fast shutdown control box 601, or the common mode voltage value at the input end, or any combination of the above signals. According to the changes of these signals, the control module judges whether it is necessary to start the discharge device 602, and then controls the fast shutdown process of the system.
[0032] The discharge device 602 includes a resistive device 6021 and a switching device 6022. The resistive device 6021 can be selected from one of a resistor, a resistor in parallel with a capacitor, or a resistor in series with an inductor. The switching device 6022 can be selected from one of a relay and its drive circuit, an IGBT and its drive circuit, or a MOSFET and its drive circuit.
[0033] In this embodiment, by using the switching device 6022, the discharge device 602 can form a path, and then guide the current in the DC bus to the ground wire 401, thereby quickly reducing the voltage between the DC bus and the ground wire 401 and ensuring system safety.
[0034] The shutdown device 201 is one of a photovoltaic optimizer or a photovoltaic fast shutdown device, and is used to receive and send data through communication. The communication is wireless communication or power line carrier communication. When the communication module and the shutdown device 201 use the power line carrier mode for communication, the fast shutdown control box 601 includes a communication magnetic ring 603, and the communication magnetic ring 603 is penetrated by the input of the fast shutdown control box 601 and is electrically coupled to the communication module.
[0035] In this embodiment, the shutdown device 201 is one of a PV optimizer or a PV rapid shutdown device, and exchanges data with other components in the system through wireless communication or power line carrier communication. When the communication adopts the power line carrier mode, a communication magnetic ring 603 needs to be configured inside the rapid shutdown control box 601, and the communication magnetic ring 603 passes through the input line and is electrically coupled to the communication module, enabling the power line carrier communication to effectively transmit data, ensuring that the system can respond in a timely manner and control the operation of the shutdown device 201 when a fault or a rapid shutdown signal occurs, thereby ensuring the safe operation of the system.
[0036] The rapid shutdown control box 601 also includes a sampling module inside, and the signals sampled by the sampling module include one or more of the input voltage, output voltage, common mode of the input to the ground, common mode of the output to the ground, input current, output current, and temperature of the rapid shutdown control box 601. A protection circuit 604 is also connected between the input line and the output line of the rapid shutdown control box 601, and the protection circuit 604 can be a fuse or an air switch optionally.
[0037] In this embodiment, by collecting various signals, including the input voltage, output voltage, common mode voltage of the input to the ground, common mode voltage of the output to the ground, input current, output current, and temperature, etc., the rapid shutdown control box 601 can comprehensively and real-time monitor the operating state of the system. Therefore, the effect of comprehensive monitoring of multiple signal sources can be achieved, which helps to detect potential faults or unstable factors at an early stage, such as ground faults, poor wiring, or equipment damage, etc., thereby ensuring that the system is in a safe working state, preventing extreme situations such as overvoltage, overcurrent, or overheating. At the same time, the method of collecting multiple signals can also provide accurate data information, and then can promptly activate the shutdown device 201 to reduce risks, and at the same time enable the system to quickly diagnose the source of the fault, reduce the downtime, and improve the safety, reliability, and response ability of the system.
[0038] The present invention provides a control method using the above system, including the following steps:
[0039] Collect the DC bus electrical signal;
[0040] When the electrical signal meets the preset conditions and a rapid shutdown signal in the system is detected, drive the switching device 6022 of the discharge device 602 to form a path, allowing the current in the DC bus to flow through the discharge device 602 to the ground wire 401, thereby rapidly reducing the voltage between the DC bus and the ground wire 401 and ensuring the safety of the system.
[0041] When the electrical signal is the voltage signal inside the fast turn-off control box 601, the discharge device 602 is activated when the voltage signal is lower than the first threshold. The voltage signal can optionally be the input voltage or the input-to-ground common-mode voltage of the fast turn-off control box 601. After the fast turn-off signal is detected and collected, after waiting for the first interval time, the discharge device 602 is controlled to be enabled, and the first interval time is less than 30 s.
[0042] Working principle: During use, first, the sampling module in the fast turn-off control box 601 is used to monitor the electrical signals in the system in real time. The collected signals include the DC bus voltage, input voltage, input-to-ground common-mode voltage, output voltage, etc. These signals are transmitted to the control module, which judges the electrical parameters according to the preset conditions and standards.
[0043] When it is monitored that the electrical signal meets the preset conditions (for example, the input voltage exceeds the set safety threshold, or a fast turn-off signal appears in the system), the control module analyzes these signals to judge whether the system enters a fault state or an emergency (such as a hot spot, connection problem, etc.). At this time, the system triggers the fast turn-off process.
[0044] Subsequently, the control module drives the switch device 6022 in the discharge device 602 to close to form a path, so that the current in the DC bus flows through the discharge device 602 to the ground wire 401. Through this process, the resistive device 6021 (such as a resistor, capacitor, inductor, etc.) of the discharge device 602 starts to function, quickly releasing the excessive voltage to the ground wire 401, thereby effectively reducing the voltage between the DC bus and the ground wire 401.
[0045] And during the discharge process, the current flows to the ground wire 401 and the voltage drops to the safe range. Usually within 30 seconds, the voltage will quickly drop below 30 V, meeting the safety requirements of fast turn-off. And during this process, the internal protection circuit 604 of the system will also play a protective role to prevent the system from being damaged due to excessive current.
[0046] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A photovoltaic rapid shutdown system, comprising: A photovoltaic assembly (101), a shutoff device (201), a rapid shutoff control box (601) and an inverter (301), wherein the photovoltaic assembly (101) is electrically coupled to the shutoff device (201), an output end of the shutoff device (201) is connected in series and electrically coupled to an input end of the rapid shutoff control box (601) via a DC bus, an output end of the rapid shutoff control box (601) is connected to a DC end of the inverter (301), and the inverter (301) is connected to a power grid (501), characterized in that the rapid shutoff control box (601) is electrically coupled to a ground wire (401), and a discharge device (602) is included inside the rapid shutoff control box (601), which is used to reduce the voltage between the DC bus and the ground wire (401) during the rapid shutoff process.
2. A photovoltaic rapid shutdown system according to claim 1, characterized in that: The rapid shutdown control box (601) also includes at least one input line, at least one output line, at least one power input, a power module and a control module, wherein the power module provides power to the control module and the discharge device (602), the control module is used to control the operation of the discharge device (602), the discharge device (602) is electrically coupled to the positive end of the input line and the ground line (401), or electrically coupled to the negative end of the input line and the ground line (401), or electrically coupled to the positive end of the input line and the negative end of the input line, and the power module provides AC power.
3. A photovoltaic rapid shutdown system according to claim 2, characterized in that: The control module controls the operation of the discharge device (602) by receiving a signal in the system, wherein the signal comprises one or more of a fast shutdown signal, a differential mode voltage value at the input end of the fast shutdown control box (601), or a common mode voltage value at the input end of the fast shutdown control box (601).
4. A photovoltaic rapid shutdown system according to claim 2, characterized in that: The discharge device (602) comprises a resistive device (6021) and a switch device (6022); the resistive device (6021) may be one of a resistor, a resistor in parallel with a capacitor, or a resistor in series with an inductor; and the switch device (6022) may be one of a relay and a drive circuit thereof, an IGBT and a drive circuit thereof, or a MOSFET and a drive circuit thereof.
5. A photovoltaic rapid shutdown system according to claim 1, characterized in that: The shut-off device (201) is a photovoltaic optimizer or a photovoltaic fast shut-off device, and is used for receiving and sending data via communication, wherein the communication is wireless communication or power line carrier communication.
6. A photovoltaic rapid shutdown system according to claim 5, characterized in that: When the communication module and the shutoff device (201) communicate using a power line carrier, the rapid shutoff control box (601) includes a communication magnetic ring (603), and the communication magnetic ring (603) is passed through the input of the rapid shutoff control box (601) and electrically coupled to the communication module.
7. A photovoltaic rapid shutdown system according to claim 2, characterized in that: The rapid shutdown control box (601) further comprises a sampling module, and the signal sampled by the sampling module comprises one or more of the input voltage, output voltage, input-to-ground common mode, output-to-ground common mode, input current, output current and temperature of the rapid shutdown control box (601).
8. A photovoltaic rapid shutdown system according to claim 1, characterized in that: A protection circuit (604) is also connected between the input line and the output line of the rapid shutdown control box (601), and the protection circuit (604) can be a fuse or an air switch.
9. A photovoltaic rapid shutdown control method, based on a photovoltaic rapid shutdown system according to any one of claims 1 to 8, characterized in that: The following steps are involved: Collect DC bus electrical signals; When the electrical signal meets the preset conditions and a fast shutdown signal in the system is detected, the switch device (6022) of the driving control discharge device (602) forms a path, allowing the current in the DC bus to flow to the ground line (401) through the discharge device, thereby quickly reducing the voltage between the DC bus and the ground line, ensuring system safety.
10. A photovoltaic fast shutdown control method according to claim 9, characterized in that: When the electrical signal is a voltage signal inside the fast shutdown control box (601), the discharge device (602) is started when the voltage signal is lower than a first threshold value, and the voltage signal may be an input voltage of the fast shutdown control box (601) or an input common mode voltage to ground; After the rapid shutdown signal is detected, the discharge device (602) is controlled to be enabled after a delay of a first interval time, wherein the first interval time is less than 30 seconds.