Switching circuit, off-grid / grid-connected circuit, and off-grid / grid-connected control method

Abstract

The present invention relates to a switching circuit, an off-grid / grid-connected circuit, and an off-grid / grid-connected control method. By means of a relay, the switching circuit can reasonably control the on / off of a contactor on a power supply loop, so that only one auxiliary power supply is arranged to obtain power from any power supply port, thus achieving simple control, high reliability, and low cost. Additionally, according to the switching circuit of the present application, by connecting a current quick turn-off unit in parallel to two ends of a first relay, when a short circuit on a power grid side is detected, a control unit controls the current quick turn-off unit to be turned off, so that the contact separation and arc extinguishing time of the first relay can be saved, thereby greatly reducing the time required for a grid-connected to off-grid transition, and effectively reducing safety risks. Additionally, by combining a sampling calculation unit sampling a power grid voltage in real time for detection and the described switching circuit, the fault detection time can be effectively reduced, thereby reducing the total time required for a grid-connected to off-grid transition, and effectively reducing safety risks.

Description

A switching circuit, an off-grid circuit, and an off-grid control method Technical Field

[0001] The present invention relates to the field of off-grid and on-grid technology, and in particular to a switch circuit, an off-grid and on-grid circuit, and an off-grid and on-grid control method. Background Art

[0002] With the widespread adoption of photovoltaic power generation and the advancement of energy storage technology, household energy storage products are becoming increasingly popular. Household electricity sources are also becoming diverse, including the grid, photovoltaics, batteries, and diesel generators. How to rationally distribute these energy sources to ensure uninterrupted power supply to households requires an intelligent control device that acts as an energy router. This router must be able to provide power to households regardless of whether power is available from the grid, photovoltaics, batteries, or diesel generators. The router must include control circuitry and a switch to enable and disable the control circuitry. The auxiliary power supply must be designed to draw power from multiple ports, ensuring that it can operate from any power source. This imposes additional requirements on the auxiliary power supply, such as requiring each port to meet EMC and surge requirements. This not only increases power supply costs but also increases the risk of failure. Current power supply solutions for multiple power ports typically utilize several ports for power supply, with the internal auxiliary power supply drawing power from the circuit breakers of these ports. This requires additional EMC filtering and protection circuitry for each power source. Furthermore, multiple primary windings are added to a single auxiliary power transformer to provide a single auxiliary power source. However, only one primary winding can participate in the operation of the transformer at a time, so there is a complex interlocking relationship between the control circuits of multiple primary windings, and each primary winding must have an independent control circuit and main switch tube. The circuit form is relatively complex and the cost is high, so it is necessary to optimize and adjust the switching circuit to achieve reliable and stable power-on of the auxiliary power supply.

[0003] In addition, referring to Figure 4, the existing off-grid circuit usually includes an on-grid power supply 1, a power grid 2 and a contactor unit. The contactor unit includes a contactor contact 3, a contactor coil 4 and a coil relay 5. The contactor contact 3 is connected between the on-grid power supply 1 and the power grid 2. The contactor coil 4 is connected to the contactor contact 3 and controls the closing and opening of the contactor contact 3. The coil relay 5 is connected to the contactor coil 4.

[0004] When grid 2 is operating normally, coil relay 5 closes, contactor coil 4 is energized, and contactor coil 4 controls contactor contact 3 to close, achieving grid connection. If a grid-side short circuit occurs, control unit 6 controls coil relay 5 to disconnect, de-energizing contactor coil 4 and disconnecting contact 3. The output port of grid-connected power supply 1 short-circuits, the voltage drops to zero, and grid-connected power supply 1 switches to voltage source mode, completing the grid-connection-to-off-grid transition. The grid-connection-to-off-grid transition time consists of three parts:

[0005] 1. Grid 2 fault detection time;

[0006] 2. Contact separation and arc extinguishing time of coil relay 5;

[0007] 3. Contactor contact 3 separation time;

[0008] In summary, the current total time required for grid-connection and off-grid switching is about 30-60ms, wherein the hysteresis in the operation of the coil relay 5 increases the grid-connection and off-grid switching time, and a higher delay largely means a higher safety risk.

[0009] Therefore, a new switching circuit and grid-connected to off-grid solution are urgently needed to solve the above problems.

[0010] Summary of the Invention

[0011] A main purpose of the present invention is to overcome at least one of the above-mentioned defects, and to provide a switching circuit in which the auxiliary power supply can be powered at any power supply end, with simple control, high reliability, low cost, and also optimized to achieve rapid current shutdown.

[0012] A main purpose of the present invention is to overcome at least one of the above-mentioned defects, and to provide an off-grid circuit and an off-grid control method, which, based on the above-mentioned design of rapid current shutdown, can greatly reduce the time required for grid-connected to off-grid conversion and effectively reduce safety risks.

[0013] In order to achieve the above object, the technical solution adopted by the present invention is:

[0014] The present invention provides a switching circuit, which includes a first power supply end, a second power supply end, a first contactor, a first relay, and a control unit, wherein the first power supply end is connected to the power grid, the second power supply end is connected to the grid power supply, the first contactor is used to control the on-off of the circuit, and the first relay is used to control the conversion and isolation of the signal;

[0015] The first contactor includes a first contactor contact and a first contactor coil;

[0016] The first power supply end is connected to the second power supply end through the first contactor contact, and the first power supply end is also connected to the first contactor coil through the first relay;

[0017] The control unit controls on and off of the first relay.

[0018] According to one embodiment of the present invention, the switching circuit also includes an auxiliary power supply, the first power supply end is connected to the second power supply end and the auxiliary power supply respectively through the first contactor contacts, the auxiliary power supply is connected to the control unit and is used to provide working power for the control unit, and the contacts of the first relay are normally closed contacts.

[0019] According to one embodiment of the present invention, the first power supply end is further connected to a user load via the first contactor contact.

[0020] According to one embodiment of the present invention, the switching circuit further includes a first circuit breaker, and the first power supply end is connected to the power grid through the first circuit breaker, wherein the first circuit breaker is used to disconnect the current path in the circuit, the contacts of the first relay are normally closed contacts, and the contacts of the first contactor are normally open contacts.

[0021] According to one embodiment of the present invention, the switching circuit further includes a third power supply terminal, a second contactor and a second relay, wherein the second contactor is used to control the on and off of the circuit, and the second relay is used to control the conversion and isolation of the signal;

[0022] The second contactor includes a second contactor contact and a second contactor coil;

[0023] The third power supply end is connected to the second power supply end through the second contactor contact, and the third power supply end is also connected to the second contactor coil through the second relay;

[0024] The control unit is further configured to control the on and off of the second relay.

[0025] According to one embodiment of the present invention, it also includes an auxiliary power supply and an electrical load, and the third power supply end is connected to the second power supply end, the auxiliary power supply and the user load respectively through the second contactor contact, and the auxiliary power supply is connected to the control unit for providing working power to the control unit.

[0026] According to one embodiment of the present invention, the switching circuit further includes a third relay, the second contactor coil is connected to the second power supply end via the third relay, and the control unit is further configured to control the on and off of contacts of the third relay.

[0027] According to one embodiment of the present invention, the switching circuit further includes a second circuit breaker, and the third power supply end is connected to the oil engine or the smart load through the second circuit breaker, wherein the second circuit breaker is used to disconnect the current path in the circuit, the contacts of the second relay are normally closed contacts, and the contacts of the second contactor are normally open contacts.

[0028] According to one embodiment of the present invention, the switching circuit further includes a semiconductor switch tube, and the semiconductor switch tube is connected in parallel with the contact of the first relay;

[0029] The control unit is used to control the semiconductor switch tube to be turned on and control the contacts of the first relay to be disconnected when the auxiliary power supply is energized.

[0030] According to one embodiment of the present invention, the semiconductor switch tube is any one of the following: a power diode, a field effect transistor, a bipolar junction transistor, an insulated gate bipolar transistor and a thyristor.

[0031] According to one embodiment of the present invention, the grid-connected power supply includes one or more of photovoltaic, wind, nuclear or energy storage power supplies, and the second power supply end is connected to the grid-connected power supply via an inverter.

[0032] According to one embodiment of the present invention, the switch circuit further includes a fast current shutoff unit connected in parallel to both ends of the first relay, and the control unit controls the on and off of the fast current shutoff unit.

[0033] According to one embodiment of the present invention, the fast current shutdown unit includes a first IGBT and a second IGBT, the emitter of the first IGBT is connected to the emitter of the second IGBT, and the collector of the first IGBT and the collector of the second IGBT are respectively connected to the two ends of the first relay; or, the fast current shutdown unit includes a first IGBT and a second IGBT, the collector of the first IGBT is connected to the collector of the second IGBT, and the emitter of the first IGBT and the emitter of the second IGBT are respectively connected to the two ends of the first relay.

[0034] According to one embodiment of the present invention, the control unit controls the first IGBT and the second IGBT to be closed or opened simultaneously, so as to bidirectionally conduct or bidirectionally disconnect the branch where the first IGBT and the second IGBT are located.

[0035] According to one embodiment of the present invention, the response time of the fast current shutoff unit is less than 0.1 ms.

[0036] The present invention also provides an off-grid and on-grid circuit, which includes an on-grid power supply, an electric grid and the above-mentioned switch circuit, wherein the first contactor contact is connected between the on-grid power supply and the electric grid.

[0037] According to one embodiment of the present invention, after the first relay is energized, the first contactor coil is energized to control the first contactor contact to close, and the online power supply is connected to the power grid; when the online power supply is connected to the power grid, the control unit controls the first IGBT and the second IGBT to close at the same time, and controls the first relay to open.

[0038] According to one embodiment of the present invention, when the grid side is short-circuited, the control unit controls the first IGBT and the second IGBT to be turned off simultaneously.

[0039] According to one embodiment of the present invention, the off-grid and grid-connected circuit further includes a detection unit, which is connected to the control unit. The detection unit detects in real time whether a short circuit occurs on the grid side, and the control unit controls the first IGBT and the second IGBT to be closed or opened at the same time according to the detection result of the detection unit.

[0040] According to one embodiment of the present invention, the detection unit determines whether a short circuit occurs on the grid side by detecting the voltage and / or instantaneous active power of the grid in real time.

[0041] According to one embodiment of the present invention, the off-grid and grid-connected circuit further includes a sampling and calculation unit, which samples the grid voltage in real time and compares the sampled grid voltage with a voltage threshold. When the grid voltage sampled by the sampling and calculation unit is lower than the voltage threshold, the control unit disconnects the first relay or the current fast shutdown unit.

[0042] According to one embodiment of the present invention, the sampling and calculation unit is also used to sample the grid voltage and grid current in real time before the grid-connected power supply is connected to the grid, and the control unit is also used to turn on the current fast shutdown unit when the grid voltage is higher than the voltage threshold and the grid current is lower than the current threshold.

[0043] According to one embodiment of the present invention, the voltage threshold is any value between 50% and 95% of the reference grid voltage.

[0044] According to one embodiment of the present invention, the voltage threshold is any value between 5% and 50% of the reference grid voltage.

[0045] The present invention also provides an off-grid and on-grid control method, which is applied to the off-grid and on-grid circuit described above, and the method comprises the following steps:

[0046] S1: After the grid is powered on, the first relay is turned on, and after the first contactor coil is energized, the first contactor contact is closed, and the on-grid power supply is connected to the grid;

[0047] S2. After the on-grid power supply is connected to the power grid, controlling the current fast shutdown unit to close and controlling the first relay to open.

[0048] According to one embodiment of the present invention, the following steps are also included:

[0049] S3. When the grid side is short-circuited, the control unit controls the first IGBT and the second IGBT to be disconnected simultaneously, and the branches where the first IGBT and the second IGBT are located are bidirectionally disconnected.

[0050] According to one embodiment of the present invention, in step S3, a detection unit is used to detect in real time whether a short circuit occurs on the grid side.

[0051] The present invention also provides an off-grid and on-grid control method, which is applied to the off-grid and on-grid circuit described above and is characterized by comprising the following steps:

[0052] L1. Before the on-grid power supply is connected to the grid, the sampling and calculation unit samples the grid voltage and grid current in real time. When the grid voltage is higher than the voltage threshold and the grid current is lower than the current threshold, the control unit controls the first relay or the current fast shutdown unit to turn on;

[0053] L2. After the on-grid power supply is connected to the grid, the sampling and calculation unit samples the grid voltage in real time. When the sampling and calculation unit detects that the grid voltage is lower than a voltage threshold, the control unit controls the first relay or the current fast shutdown unit to disconnect.

[0054] 28. An off-grid and on-grid control method, applied to the off-grid and on-grid circuit according to claim 21, characterized in that it comprises the following steps:

[0055] L1. Before the on-grid power supply is connected to the grid, the sampling and calculation unit samples the grid voltage and grid current in real time. When the grid voltage is higher than a voltage threshold and the grid current is lower than a current threshold, the control unit controls the first relay to be turned on;

[0056] L2. After the on-grid power supply is connected to the grid, the control unit controls the current fast shutdown unit to turn on, and then the control unit controls the first relay to turn off. The sampling calculation unit samples the grid voltage in real time. When the sampling calculation unit detects that the grid voltage is lower than the voltage threshold, the control unit controls the current fast shutdown unit to turn off.

[0057] Compared with the prior art, the advantages and beneficial effects of the patent application of this invention are:

[0058] The switching circuit of the present application sets a first relay in the power-taking circuit of the auxiliary power supply. When the first power supply end has power, the coil of the first contactor is energized, the contacts of the first contactor are closed, and the subsequent user load and the auxiliary power supply are energized and start to work normally. When the first power supply end has no power and the second power supply end has power, the user load and the auxiliary power supply draw power from the second power supply end and can also work normally. That is to say, the on and off of the contactor in the power supply circuit can be reasonably controlled by the relay, so that only one auxiliary power supply can draw power from any power supply port, which is simple to control, highly reliable and low cost.

[0059] Furthermore, the switching circuit of the present application connects a current fast shut-off unit in parallel at both ends of the first relay. When a short circuit is detected on the grid side, the control unit controls the current fast shut-off unit to disconnect, which can save the time for contact separation and arc extinguishing of the first relay, thereby greatly reducing the time required for grid-connected and off-grid switching, and effectively reducing safety risks.

[0060] In addition, the off-grid circuit samples the grid voltage in real time through the sampling calculation unit and compares the sampled grid voltage with the voltage threshold. When the grid voltage sampled by the sampling calculation unit is lower than the voltage threshold, the control unit disconnects the current fast shutdown unit or the first relay without waiting until the grid voltage drops to 0, thereby effectively saving fault detection time, thereby reducing the total time required for grid-connected to off-grid conversion, and effectively reducing safety risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0062] FIG1 is a block diagram of the structure of the provided intelligent power distribution cabinet;

[0063] FIG2 is a connection diagram of a switch circuit in one embodiment of the present application;

[0064] FIG3 is a partial connection diagram of a switch circuit in another embodiment of the present application;

[0065] FIG4 is a connection diagram of an existing off-grid circuit;

[0066] FIG5 is a connection diagram of an off-grid circuit in a preferred embodiment of the present invention;

[0067] FIG6 is a connection diagram of an off-grid circuit in another preferred embodiment of the present invention.

[0068] FIG7 is a connection diagram of an off-grid and on-grid circuit in Embodiment 8 of the present invention;

[0069] FIG8 is a connection diagram of an off-grid and on-grid circuit in Embodiment 9 of the present invention;

[0070] FIG9 is a connection diagram of an off-grid and grid-connected circuit in the tenth embodiment of the present invention.

[0071] The accompanying drawings are explained as follows: KA1, first contactor; KA2, second contactor; K1, contact of first relay; K2, contact of second relay; K3, contact of third relay; QF1, first circuit breaker; QF2, second circuit breaker; S1, semiconductor switch tube; 1, grid power supply; 2, grid; 3, first contactor contact; 4, first contactor coil; 5, control unit; 6, first IGBT; 7, second IGBT; 8, auxiliary power supply; 9, sampling and calculation unit. DETAILED DESCRIPTION

[0072] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0073] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0074] Below, one of the technical fields of this application (i.e., intelligent distribution cabinet) is briefly described in conjunction with the specific implementation methods of this application.

[0075] Referring to Figure 1, the intelligent power distribution cabinet has three main power supply ports: grid, inverter and oil generator. The oil generator port can also be connected to intelligent loads, such as some high-power electrical appliances.

[0076] Based on this, this application provides a switching circuit and control system for an intelligent distribution cabinet to solve the following technical problems: 1. How to make only one auxiliary power supply that can draw power from multiple power supply ends at will, with simple control, high reliability and low cost; 2. How to quickly switch between on-grid and off-grid to prevent household power interruption; 3. How to ensure that after the auxiliary power supply or control unit of the intelligent distribution cabinet fails, the user can still draw power normally from the power grid to meet the basic electricity needs of the family.

[0077] Example 1

[0078] Referring to Figure 2, an embodiment of the present application discloses an auxiliary power supply circuit, which includes a first power supply end, a second power supply end, a first contactor KA1, a first relay, a control unit and an auxiliary power supply; in this embodiment, the first power supply end is the grid end, and the second power supply end is the inverter output end of the photovoltaic or battery, that is, the online power supply in this embodiment uses photovoltaic or battery.

[0079] The first power supply end is connected to the second power supply end, the auxiliary power supply and the user load respectively through the contacts of the first contactor KA1, and the first power supply end is also connected to the coil of the first contactor KA1 through the contact K1 of the first relay;

[0080] The auxiliary power supply is also connected to the control unit, and the control unit is used to control the on and off of the contact K1 of the first relay.

[0081] In this embodiment, the control function of the control unit can be implemented by MPU, MCU, DSP, FPGA or any combination thereof.

[0082] Auxiliary power refers to the power supply used in a power system to provide electrical energy to support system operation, monitoring, protection, or perform specific functions. It is typically not the primary power source, but rather an additional source of power for maintenance and management of the power system. Auxiliary power typically uses a backup power source (such as batteries, diesel generators, solar cells, etc.) or an uninterruptible power supply (UPS). The primary goal of auxiliary power is to ensure the availability and stability of the power system, especially in the event of a primary power failure or other emergency.

[0083] Contactors are primarily used for switching high-current loads, while relays are used to convert and isolate control signals and perform various complex control functions. Both are important components in electrical control systems, used for automation and circuit protection.

[0084] Circuit breakers are used to disconnect the path of current in a circuit to prevent accidents caused by circuit overload, short circuit and other electrical faults.

[0085] The auxiliary power supply circuit in the present application is provided with a first relay. When the first power supply end has power, the coil of the first contactor KA1 is energized, the contacts of the first contactor KA1 are closed, and the subsequent user load and auxiliary power supply are energized and start to work normally. When the first power supply end has no power and the second power supply end has power, the user load and the auxiliary power supply take power from the second power supply end and can also work normally. In summary, the on and off of the contactor in the power supply circuit can be reasonably controlled by the relay, so that only one auxiliary power supply can take power from any power supply port, which is simple to control, highly reliable and low cost.

[0086] Furthermore, the auxiliary power supply circuit further includes a first circuit breaker QF1 , the first power supply end is connected to the power grid through the first circuit breaker QF1 , and the contact K1 of the first relay is a normally closed contact.

[0087] In this embodiment, the second power supply end is connected to an inverter, and the inverter is connected to a photovoltaic module or an energy storage battery.

[0088] By configuring the first circuit breaker QF1, when the grid is powered, closing it will cause the normally closed contact K1 of the first relay on the control board to close. This energizes the coil of the first contactor KA1, closing the contacts of the first contactor KA1. This energizes the inverter port, energizing the auxiliary power supply and starting operation. The circuit breaker provides overload and short-circuit protection, protecting circuits and electrical equipment from damage caused by current overloads, short circuits, and other electrical faults.

[0089] Furthermore, the auxiliary power supply circuit also includes a third power supply terminal, a second contactor KA2 and a second relay; the third power supply terminal can be the output terminal of the oil engine intelligent load.

[0090] The third power supply end is connected to the second power supply end, the auxiliary power supply and the user load respectively through the contacts of the second contactor KA2, and the third power supply end is also connected to the coil of the second contactor KA2 through the contact K2 of the second relay;

[0091] The control unit is further configured to control the on and off of the contact K2 of the second relay.

[0092] By setting the second relay, when the third power supply end has power, the coil of the second contactor KA2 is energized, the contacts of the second contactor KA2 are closed, and the subsequent user load and auxiliary power supply are energized and start to work normally; when the third power supply end has no power and the second power supply end has power, the user load and auxiliary power supply draw power from the second power supply end and can also work normally.

[0093] Furthermore, the auxiliary power supply circuit further includes a second circuit breaker QF2, the third power supply end is connected to the oil engine through the second circuit breaker QF2, and the contact K2 of the second relay is a normally closed contact.

[0094] By setting the second circuit breaker QF2, when the oil engine is powered, the second circuit breaker QF2 is closed. Since the contact K2 of the second relay on the control panel is a normally closed contact, at this time, the contact K2 of the second relay is in a closed state, the coil of the second contactor KA2 is energized, the contact of the second contactor KA2 is closed, the inverter port is powered, and the auxiliary power supply is energized and starts working.

[0095] 3 , further, the auxiliary power supply circuit further includes a semiconductor switch tube S1 , and the semiconductor switch tube S1 is connected in parallel with the contact K1 of the first relay;

[0096] The control unit is used to control the semiconductor switch tube S1 to be turned on and control the contact K1 of the first relay to be turned off when the auxiliary power supply is powered.

[0097] In this embodiment, the semiconductor switch tube S1 is any one of the following: a power diode, a field effect transistor, a bipolar junction transistor, an insulated gate bipolar transistor, and a thyristor.

[0098] For the fast on-grid and off-grid function, the switching time of traditional contactors or relay contacts is at the millisecond level. Combined with the judgment time in the control, the entire on-grid and off-grid switching time will be greater than 20ms, which may cause the user-side load to lose power and shut down. In addition, during the switching process from off-grid to on-grid, due to the large tolerance of the mechanical action time of the contactor or relay contacts, it is easy to cause the grid phase to be inconsistent at the moment of switching, resulting in a momentary large current shock, affecting the life of the switching device and the operation of the subsequent load. By adopting the auxiliary power supply circuit of this embodiment, taking advantage of the fast response speed of the semiconductor switch tube S1, the semiconductor switch tube S1 switches the grid-side contactor on and off, and a 5ms fast on-grid and off-grid switching function can be achieved.

[0099] Specifically, a semiconductor switch S1 is connected in parallel across the normally closed contact K1 of the first relay in the coil power supply circuit of the first contactor KA1. When the auxiliary power supply is energized, the control unit turns on the semiconductor switch S1 and then turns off the normally closed contact K1 of the first relay. When the auxiliary power supply is energized, the semiconductor switch S1 is used to control the on / off state of the first contactor KA1, essentially keeping the normally closed contact K1 of the first relay in a normally open state. The on / off time of the semiconductor switch S1 is in the nanosecond range, while that of a relay is in the millisecond range. Using the semiconductor switch S1 to control the on / off state of the first contactor KA1 significantly shortens the time it takes to switch between the intelligent power distribution cabinet and the grid.

[0100] In response to the problem of failure of smart distribution cabinets, the current common practice in the industry is to first allow the auxiliary power supply to work, and then close the contactor on the grid side to allow the user side to get power. The disadvantage of this approach is that once the auxiliary power supply fails, the user side will be out of power. Even if the grid has power at this time, the user will not be able to use electricity. If you want to solve this fault condition, you may need to add an additional circuit breaker bypass contactor as an emergency condition. Using the auxiliary power supply circuit of this embodiment, the first contactor KA1 on the grid side is controlled to be closed through the normally closed contact K1 of the first relay. Once the control circuit fails or the auxiliary power supply fails, the normally closed contact can maintain the first contactor KA1 on the grid side to be closed, ensuring the user's basic electricity needs. In other words, it can be ensured that after the auxiliary power supply or control unit of the smart distribution cabinet fails, the user can still draw electricity normally from the grid to meet the basic electricity needs of the family.

[0101] Specifically, as shown in Figure 3, the coil of the first contactor KA1 draws power from the grid, and the normally closed contact K1 of the first relay is connected in series to the power supply circuit of the coil of the first contactor KA1. When the grid is powered, the coil of the first contactor KA1 receives power, its normally open contact closes, and downstream user loads are powered. When the grid loses power, the coil of the first contactor KA1 loses power, its normally open contact opens, and downstream user loads lose power. By leveraging the basic power supply characteristics of the grid, when the control unit or semiconductor switch S1 fails, the normally closed contact K1 of the first relay returns to its normally closed state, deactivating other functions of the smart distribution cabinet, allowing the smart distribution cabinet to retain its basic grid power supply characteristics. Furthermore, when the auxiliary power supply fails, the first relay loses power, and its normally closed contact naturally returns to its normally closed state. Simultaneously, since the downstream inverter cannot communicate with the smart distribution cabinet, it will warn the user that the smart distribution cabinet is malfunctioning. However, in this case, the user can still draw power from the grid normally.

[0102] Example 2

[0103] This embodiment discloses an auxiliary power supply circuit. The auxiliary power supply circuit in this embodiment differs from the auxiliary power supply circuit in the first embodiment in that:

[0104] In this embodiment, the third power supply terminal is connected to the smart load via the second circuit breaker QF2, wherein the smart load may be, for example, a high-power electrical appliance.

[0105] In this embodiment, intelligent loads refer to loads or devices used in computing, electronics, communications, and automation systems, which possess a certain degree of intelligence, automation, and remote control capabilities. These loads are typically able to sense their environment, automatically adapt to conditions, and respond to external commands to optimize performance, improve efficiency, or provide higher-level functionality.

[0106] Smart loads can include smart home devices (e.g., smart lighting, smart thermostats), industrial automation systems (e.g., automatically controlled machines, robots), intelligent transportation systems (e.g., smart traffic lights, self-driving cars), and various embedded systems and IoT devices.

[0107] Example 3

[0108] 2 and 3 , this embodiment discloses a control system for an intelligent power distribution cabinet, the control system including the auxiliary power supply circuit, the power grid and the inverter;

[0109] The first power supply end of the auxiliary power supply circuit is connected to the power grid, and the second power supply end of the auxiliary power supply circuit is connected to the inverter.

[0110] Furthermore, the control system also includes an oil engine or an intelligent load;

[0111] The third power supply end of the auxiliary power supply circuit is connected to the oil generator or the smart load.

[0112] With this control system, users can switch loads by controlling the on / off switching of the second contactor KA2, saving power in off-grid mode. The auxiliary power supply typically draws power from the inverter input, then connects to multiple ports via the first, second, and third relays.

[0113] Furthermore, the third power supply terminal of the auxiliary power circuit is connected to the smart load, and the control unit of the auxiliary power circuit controls the normally open contact K3 of the third relay to close; or,

[0114] The third power supply end of the auxiliary power circuit is connected to the oil engine, and the control unit of the auxiliary power circuit controls the normally open contact K3 of the third relay to be disconnected.

[0115] Specifically, on the one hand, when the third power supply end is connected to the smart load, although the contact K2 of the second relay is a normally closed contact, the contact of the second contactor KA2 is disconnected due to lack of power. The control unit can be used to control the normally open contact K3 of the third relay to close, thereby allowing the contact of the second contactor KA2 to be turned on, thereby supplying power to the smart load; on the other hand, when the third power supply end is connected to the oil engine, the normally closed contact K2 of the second relay is in a normally closed state, and the control unit controls the normally open contact K3 of the third relay to be disconnected. At this time, the contact of the second contactor KA2 can also be turned on, and the second power supply end (i.e., the inverter output end) has power.

[0116] Example 4

[0117] 5 , this embodiment discloses a switch circuit, which includes a first contactor, a first relay 5 , a current fast shutoff unit, and a control unit 5 .

[0118] The first contactor includes a first contactor contact 3 and a first contactor coil 4. The first contactor coil 4 is connected to the first contactor contact 3 and controls the closing and opening of the first contactor contact 3. The first relay 5 is connected to the first contactor coil 4. The current fast shutdown unit is connected in parallel at both ends of the first relay. The control unit 5 controls the conduction and disconnection of the first relay 5 and the current fast shutdown unit.

[0119] The switching circuit in the present invention connects a current fast shut-off unit in parallel at both ends of the first relay 5. When a short circuit is detected on the grid side, the control unit 5 controls the current fast shut-off unit to be disconnected, thereby eliminating the time for contact separation and arc extinguishing of the first relay 5, thereby greatly reducing the time required for grid-connected to off-grid switching, and effectively reducing safety risks.

[0120] In this embodiment, the fast current shutdown unit includes a first IGBT 6 and a second IGBT 7. The emitter of the first IGBT 6 is connected to the emitter of the second IGBT 7, and the collector of the first IGBT 6 and the collector of the second IGBT 7 are respectively connected to the two ends of the first relay 5. The back-to-back connection of the two diodes in the first IGBT 6 and the second IGBT 7 ensures that the branches containing the first IGBT 6 and the second IGBT 7 can be turned on and off in both directions, which is suitable for AC power supply scenarios.

[0121] Among them, the response time of IGBT is usually at the microsecond (μs) level. Compared with the contact separation and arc extinguishing time of the first relay 5, the turn-off time of IGBT can be ignored. Therefore, it is equivalent to saving the contact separation and arc extinguishing time of the first relay 5 during the process of grid-connected to off-grid.

[0122] Furthermore, the control unit 5 controls the first IGBT 6 and the second IGBT 7 to be closed or opened simultaneously, so as to bidirectionally conduct or bidirectionally disconnect the branch where the first IGBT 6 and the second IGBT 7 are located, thereby reducing the disconnection time of the entire current fast shutdown unit and further shortening the time from grid connection to off-grid connection.

[0123] The first relay 5 is in a normally closed state, and the first contactor contact 3 is in a normally open state. That is, before the grid-connected power supply 1 is connected to the grid 2, the first relay 5 is closed and the first contactor contact 3 is open. When the first relay 5 is powered on, the first contactor coil 4 is powered on and controls the first contactor contact 3 to close, connecting the grid-connected power supply 1 to the grid 2. The control unit 5 then controls the first IGBT 6 and the second IGBT 7 to close simultaneously, controlling the first relay 5 to open.

[0124] Furthermore, the switching circuit in this embodiment further includes an auxiliary power supply 8, which is connected to the control unit 5 to supply power to the control unit 5. In other embodiments, the auxiliary power supply 8 is connected to the control unit 5 and the first relay 5, respectively, and the auxiliary power supply 8 supplies power to the control unit 5 and the first relay 5. Furthermore, the auxiliary power supply 8 can be integrated or split. An integrated auxiliary power supply can supply power to both the control unit 5 and the first relay 5 simultaneously, while a split auxiliary power supply can supply power to both the control unit 5 and the first relay 5 independently.

[0125] Preferably, the response time of the fast current shutoff unit is less than 0.1 ms. In other embodiments, the fast current shutoff unit is not limited to IGBT, and can be replaced by other devices that can achieve fast current shutoff, without specific limitation.

[0126] Example 5

[0127] This embodiment discloses a switch circuit. The switch circuit in this embodiment differs from the switch circuit in the first embodiment in that:

[0128] In this embodiment, the fast current shutdown unit includes a first IGBT 6 and a second IGBT 7. The collector of the first IGBT 6 is connected to the collector of the second IGBT 7, and the emitter of the first IGBT 6 and the emitter of the second IGBT 7 are respectively connected to the two ends of the first relay 5. This can be understood as follows: based on Figure 5, the first IGBT 6 in Figure 5 is shifted to the right and the second IGBT 7 to the left, so that the emitter of the first IGBT 6 is connected to the emitter of the second IGBT 7 (the two diodes are back-to-back), and the collector of the first IGBT 6 is connected to the collector of the second IGBT 7 (the two diodes are face-to-face).

[0129] Example 6

[0130] 5 and 6 , this embodiment discloses an off-grid circuit, including an on-grid power supply 1 and a grid 2 , which also includes a switching circuit as described in any of the above embodiments, and a first contactor contact 3 is connected between the on-grid power supply 1 and the grid 2 .

[0131] Among them, after the control unit 5 controls the first relay 5 to close, the first contactor coil 4 controls the first contactor contact 3 to close, and the online power supply 1 is connected to the grid 2; when the online power supply is connected to the grid 2, the control unit 5 controls the first IGBT6 and the second IGBT7 to close at the same time, and controls the first relay 5 to open.

[0132] Furthermore, when a short circuit occurs on the grid side, the control unit controls the first IGBT and the second IGBT to be turned off simultaneously, thereby reducing the overall disconnection time of the current fast shutdown unit and further shortening the time from grid connection to off-grid connection.

[0133] Furthermore, the off-grid and on-grid circuit of the present invention further includes a detection unit connected to the control unit 5. The detection unit detects in real time whether a short circuit occurs on the grid side. The control unit 5 controls the first IGBT 6 and the second IGBT 7 to be simultaneously closed or opened based on the detection result of the detection unit. Specifically, when the detection unit detects a short circuit on the grid side, the control unit 5 controls the first IGBT 6 and the second IGBT 7 to be simultaneously opened. When the detection unit does not detect a short circuit on the grid side, the first IGBT 6 and the second IGBT 7 remain closed.

[0134] Optionally, the detection unit determines whether a short circuit occurs on the grid side by detecting the voltage and / or instantaneous active power of the grid in real time. Specifically, when the detection unit detects that the voltage and / or instantaneous active power of the grid drops to 0, it determines that a short circuit occurs on the grid side.

[0135] Furthermore, the first contactor contact 3 includes a first contactor contact and a second first contactor contact, wherein the first contactor contact is connected to the live line of the power grid 2, and the second contactor contact is connected to the neutral line of the power grid 2. The first contactor coil 4 controls the first contactor contact and the second first contactor contact to open or close simultaneously.

[0136] Optionally, the first contactor coil 4 and the first relay 5 are connected in series to the grid 2 and are powered by the grid 2; or the first contactor coil 4 and the first relay 5 are connected in series to the grid power supply 1 and are powered by the grid power supply 1. It is not necessary to provide a separate power supply to power the first relay 5.

[0137] An auxiliary power supply 8 may also be provided, connected to the grid 2, which supplies power to the auxiliary power supply 8; alternatively, the auxiliary power supply 8 may be connected to the grid power supply 1, which supplies power to the auxiliary power supply 8. Specifically, the auxiliary power supply 8 may be powered by either the grid power supply 1 or the grid 2. Here, the auxiliary power supply 8 stores and converts the electrical energy from the grid power supply 1 or the grid 2, ensuring a more stable output. Furthermore, the auxiliary power supply 8 may be independent, meaning it is not connected to the grid power supply 1 or the grid 2 and does not rely on the electrical energy from the grid power supply 1 or the grid 2. The auxiliary power supply 8 may also independently power the control unit 5, as shown in FIG6 . Furthermore, the control unit 5 may be connected to either the grid power supply 1 or the grid 2, with the grid power supply 1 or the grid 2 supplying power to the control unit 5.

[0138] Optionally, the grid-connected power supply 1 includes one or more of photovoltaic, wind, nuclear, or energy storage power sources, without limitation.

[0139] The off-grid circuit in the present invention connects a current fast shut-off unit in parallel at both ends of the first relay 5. When a short circuit is detected on the grid side, the control unit 5 controls the current fast shut-off unit to be disconnected, thereby eliminating the time for contact separation and arc extinguishing of the first relay 5, thereby greatly reducing the time required for grid-connected to off-grid conversion and effectively reducing safety risks.

[0140] Example 7

[0141] This embodiment discloses an off-grid and on-grid control method, which is applied to the switch circuit in the above embodiment. The off-grid and on-grid control method includes the following steps:

[0142] Step S1: Control the first relay 5 to be turned on, the first contactor contact 3 to be closed, and the on-grid power supply 1 to be connected to the grid 2. Specifically, the control unit 5 controls the first relay 5 to be turned on. After the first relay 5 is turned on, the first contactor coil 4 is energized. The first contactor coil 4 controls the first contactor contact 3 to be closed, thereby connecting the on-grid power supply 1 to the grid 2.

[0143] Step S2: After the grid-connected power supply 1 is connected to the grid 2, the fast current shutdown unit is controlled to close and the first relay 5 is controlled to open. Specifically, the fast current shutdown unit includes a first IGBT 6 and a second IGBT 7, the connection relationship of which is as described in the first and second embodiments. After the grid-connected power supply 1 is connected to the grid 2, the control unit controls the first IGBT 6 and the second IGBT 7 to close, and current flows through the first IGBT 6 and the second IGBT 7. Then, the control unit controls the first relay 5 to open.

[0144] Furthermore, the off-grid and on-grid control method further includes the following steps:

[0145] S3. When a short circuit occurs on the grid side, the control unit 5 controls the first IGBT 6 and the second IGBT 7 to be simultaneously disconnected, bidirectionally disconnecting the branch circuit containing the first IGBT 6 and the second IGBT 7. Specifically, when a short circuit occurs on the grid side, the control unit 5 controls the first IGBT 6 and the second IGBT 7 to be simultaneously disconnected, effectively reducing the current in the first contactor coil 4. The first contactor coil 4 controls the first contactor contact 3 to be disconnected, thereby achieving a transition from a parallel connection between the grid power source 1 and the grid 2 to an off-grid state.

[0146] Furthermore, in step S3, a detection unit is used to detect in real time whether a short circuit occurs on the grid side. The detection unit is connected to the control unit 5 and detects in real time whether a short circuit occurs on the grid side. The control unit 5 controls the first IGBT 6 and the second IGBT 7 to be simultaneously closed or opened based on the detection result of the detection unit.

[0147] The off-grid control method of the present invention can significantly reduce the time required for switching from grid connection to off-grid operation, effectively reducing safety risks.

[0148] Example 8

[0149] 7 , this embodiment discloses an off-grid and grid-connected circuit, which includes an on-grid power supply 1 , a grid 2 , a switching circuit, a sampling and calculation unit 10 , and a control unit 6 .

[0150] The above-mentioned off-grid circuit includes a first contactor and a current shut-off module. The first contactor includes a first contactor contact 3 and a first contactor coil 4. The first contactor contact 3 is connected between the grid power supply 1 and the grid 2. The first contactor coil 4 is connected to the first contactor contact 3 and controls the closing and opening of the first contactor contact 3. The current shut-off module is connected to the first contactor coil 4.

[0151] The sampling and calculation unit 9 samples the grid voltage in real time and compares the sampled grid voltage with the voltage threshold. The control unit 5 is used to disconnect the current shutdown module when the grid voltage sampled by the sampling and calculation unit 9 is lower than the voltage threshold.

[0152] The off-grid circuit in the present invention samples the grid voltage in real time through the sampling and calculation unit 9 and compares the sampled grid voltage with the voltage threshold. When the grid voltage sampled by the sampling and calculation unit 9 is lower than the voltage threshold, the current shutdown module is disconnected by the control unit 5 without waiting for the grid voltage to drop to 0, thereby effectively saving fault detection time and further reducing the total time required for grid connection to off-grid, which is at least several milliseconds shorter than the off-grid time of the prior art, effectively reducing safety risks.

[0153] Optionally, the sampling calculation unit 9 is also used to sample the grid voltage and grid current in real time before the grid power supply 1 is connected to the grid 2, and the control unit 5 is also used to turn on the current shutdown module when the grid voltage is higher than the voltage threshold and the grid current is lower than the current threshold.

[0154] Preferably, the voltage threshold is any value between 50% and 95% of the reference grid voltage. In other embodiments of the present invention, the voltage threshold can be other values ​​such as 50%, 75%, or 95% of the reference grid voltage, without limitation.

[0155] Preferably, the voltage threshold can also be any value between 5% and 50% of the reference grid voltage. In other embodiments of the present invention, the voltage threshold can be other values ​​such as 5%, 10%, 15%, or 50% of the reference grid voltage, without limitation.

[0156] In this embodiment, the above-mentioned current shutdown module includes a coil relay 5, which is connected to the first contactor coil 4; after the online power supply 1 is connected to the grid 2, the coil relay 5 is in the on state, and the control unit 5 is used to disconnect the coil relay 5 when the sampling calculation unit 9 detects that the grid voltage is lower than the voltage threshold.

[0157] Furthermore, the first contactor contact 3 includes a first contactor contact and a second first contactor contact, wherein the first contactor contact is connected to the live line of the power grid 2, and the second contactor contact is connected to the neutral line of the power grid 2. The first contactor coil 4 controls the first contactor contact and the second first contactor contact to open or close simultaneously.

[0158] Optionally, the first contactor coil 4 and the coil relay 5 are connected in series to the grid 2 and are powered by the grid 2; or the first contactor coil 4 and the coil relay 5 are connected in series to the grid power supply 1 and are powered by the grid power supply 1. It is not necessary to provide an additional power supply to power the coil relay 5.

[0159] Furthermore, the switching circuit in this embodiment further includes an auxiliary power supply 8, which is connected to the control unit 5 to supply power to the control unit 5. In other embodiments, the auxiliary power supply 8 is connected to the control unit 5 and the coil relay 5, respectively, to supply power to the control unit 5 and the coil relay 5. Furthermore, the auxiliary power supply 8 can be integrated or split. An integrated auxiliary power supply can supply power to both the control unit 5 and the coil relay 5 simultaneously, while a split auxiliary power supply can supply power to both the control unit 5 and the coil relay 5 independently.

[0160] Furthermore, the auxiliary power supply 8 is connected to the grid 2, which supplies power to the auxiliary power supply 8; alternatively, the auxiliary power supply 8 is connected to the grid power supply 1, which supplies power to the auxiliary power supply 8. That is, the auxiliary power supply 8 can be powered by either the grid power supply 1 or the grid 2. Here, the auxiliary power supply 8 stores and converts the electrical energy from the grid power supply 1 or the grid 2, ensuring a more stable output power. Furthermore, the auxiliary power supply 8 can be independent, meaning it is not connected to the grid power supply 1 or the grid 2 and does not rely on the electrical energy from the grid power supply 1 or the grid 2. The auxiliary power supply 8 can also independently power the control unit 5, as shown in FIG8 . Furthermore, the control unit 5 can be connected to either the grid power supply 1 or the grid 2, with the grid power supply 1 or the grid 2 supplying power to the control unit 5.

[0161] Furthermore, the grid-connected power supply 1 includes one or more of photovoltaic, wind, nuclear, or energy storage power sources, without specific limitation.

[0162] Embodiment 9

[0163] 8 , this embodiment discloses an off-grid circuit. The difference between the off-grid circuit in this embodiment and the off-grid circuit in the first embodiment is that:

[0164] In this embodiment, the current shutdown module includes a current fast shutdown unit, which is connected to the first contactor coil 4; after the online power supply 1 is connected to the grid 2, the current fast shutdown unit is in the on state, and the control unit 5 is used to disconnect the current fast shutdown unit when the sampling calculation unit 9 detects that the grid voltage is lower than the voltage threshold. The response time of the current fast shutdown unit is less than 0.1ms.

[0165] In this embodiment, the current fast shutdown unit includes a first IGBT6 and a first IGBT7, and the emitter of the first IGBT6 is connected to the emitter of the first IGBT7; ensuring that the branch where the first IGBT6 and the first IGBT7 are located can be turned on and off in both directions, which is suitable for AC power supply scenarios. In another embodiment, the collector of the first IGBT6 is connected to the collector of the first IGBT7, which can be understood as: based on Figure 8, the first IGBT6 in Figure 8 is shifted to the right and the first IGBT7 is shifted to the left, so that the emitter of the first IGBT6 is connected to the emitter of the first IGBT7 (two diodes back to back), and the collector of the first IGBT6 is connected to the collector of the first IGBT7 (two diodes face to face).

[0166] Among them, the response time of IGBT is usually at the microsecond (μs) level. Compared with the contact separation and arc extinguishing time of the coil relay 5 in Example 1, the turn-off time of IGBT can be ignored. Therefore, it is equivalent to saving the contact separation and arc extinguishing time of the coil relay 5 during the process of grid-connected to off-grid.

[0167] Furthermore, when the sampling calculation unit 9 samples that the grid voltage is lower than the voltage threshold, the control unit controls the first IGBT and the second IGBT to be disconnected simultaneously, thereby reducing the overall disconnection time of the current fast shutdown unit and further shortening the time from grid connection to grid disconnection.

[0168] Example 10

[0169] 9 , this embodiment discloses an off-grid circuit. The difference between the off-grid circuit in this embodiment and the off-grid circuit in the first embodiment is that:

[0170] In this embodiment, the current shut-off module includes a coil relay 5 and a current fast shut-off unit, and the current fast shut-off unit is connected in parallel at both ends of the coil relay 5; the control unit 5 is used to control the coil relay 5 to be in the disconnected state and the current fast shut-off unit to be in the on state after the online power supply 1 is connected to the grid 2. When it is detected that the grid voltage is lower than the voltage threshold, the control unit 5 controls the current fast shut-off unit to be disconnected.

[0171] Furthermore, the current fast shutdown unit includes a first IGBT6 and a first IGBT7, the emitter of the first IGBT6 is connected to the emitter of the first IGBT7, and the collector of the first IGBT6 and the collector of the first IGBT7 are respectively connected to the two ends of the line pack relay 5; or, the current fast shutdown unit includes a first IGBT6 and a first IGBT7, the collector of the first IGBT6 is connected to the collector of the first IGBT7, and the emitter of the first IGBT6 and the emitter of the first IGBT7 are respectively connected to the two ends of the line pack relay 5.

[0172] After the online power supply 1 is connected to the grid 2, the control unit 5 controls the first IGBT 6 and the first IGBT 7 to close simultaneously, and the control unit 5 controls the coil relay 5 to open. The coil relay 5 is normally closed, and the first contactor contact 3 is normally open. That is, before the online power supply 1 is connected to the grid 2, the coil relay 5 is closed, and the first contactor contact 3 is open. When the coil relay 5 is powered on, the first contactor coil 4 is powered on and controls the first contactor contact 3 to close, connecting the online power supply 1 to the grid 2. The control unit 5 then controls the first IGBT 6 and the first IGBT 7 to close simultaneously, and controls the coil relay 5 to open.

[0173] Example 11

[0174] This embodiment discloses an off-grid and on-grid control method, which is applied to the off-grid and on-grid circuit in the above embodiment 1 and includes the following steps:

[0175] Step S1: Before the grid power source 1 is connected to the grid 2, the sampling calculation unit 9 samples the grid voltage and grid current in real time. When the grid voltage is higher than the voltage threshold and the grid current is lower than the current threshold, the control unit 5 controls the current shutdown module to turn on.

[0176] Step S2: After the grid power supply 1 is connected to the grid 2, the sampling and calculation unit 9 samples the grid voltage in real time. When the sampling and calculation unit 9 detects that the grid voltage is lower than the voltage threshold, the control unit 5 controls the current shutdown module to disconnect.

[0177] Example 12

[0178] This embodiment discloses an off-grid and on-grid control method, which is applied to the off-grid and on-grid circuit in the above-mentioned embodiment 1, wherein the current shutoff module includes a coil relay 5. The method includes the following steps:

[0179] Step S1: Before the grid power source 1 is connected to the grid 2, the sampling calculation unit 9 samples the grid voltage and grid current in real time. When the grid voltage is higher than the voltage threshold and the grid current is lower than the current threshold, the control unit 5 controls the coil relay 5 to turn on.

[0180] Step S2: After the grid power supply 1 is connected to the grid 2, the sampling and calculation unit 9 samples the grid voltage in real time. When the sampling and calculation unit 9 detects that the grid voltage is lower than the voltage threshold, the control unit 5 controls the coil relay 5 to disconnect.

[0181] Example 13

[0182] This embodiment discloses an off-grid and on-grid control method, which is applied to the off-grid and on-grid circuit in the above-mentioned embodiment 2, wherein the current shutoff module includes a current fast shutoff unit. The method includes the following steps:

[0183] Step S1: Before the grid power source 1 is connected to the grid 2, the sampling calculation unit 9 samples the grid voltage and grid current in real time. When the grid voltage is higher than the voltage threshold and the grid current is lower than the current threshold, the control unit 5 controls the current fast shutdown unit to turn on.

[0184] Step S2: After the grid power supply 1 is connected to the grid 2, the sampling and calculation unit 9 samples the grid voltage in real time. When the sampling and calculation unit 9 detects that the grid voltage is lower than the voltage threshold, the control unit 5 controls the current fast shutdown unit to disconnect.

[0185] Example 14

[0186] This embodiment discloses an off-grid and on-grid control method, which is applied to the off-grid and on-grid circuit in the above-mentioned embodiment 3, wherein the current shutoff module includes a coil relay 5 and a current fast shutoff unit. The method includes the following steps:

[0187] Step S1: Before the grid power source 1 is connected to the grid 2, the sampling calculation unit 9 samples the grid voltage and grid current in real time. When the grid voltage is higher than the voltage threshold and the grid current is lower than the current threshold, the control unit 5 controls the coil relay to be turned on.

[0188] Step S2: After the online power supply 1 is connected to the grid 2, the control unit 5 controls the current fast shutdown unit to turn on, and then the control unit 5 controls the coil relay 5 to turn off. The sampling and calculation unit 9 samples the grid voltage in real time. When the sampling and calculation unit 9 detects that the grid voltage is lower than the voltage threshold, the control unit 5 controls the current fast shutdown unit to turn off.

[0189] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A switching circuit, characterized in that: It includes a first power supply end, a second power supply end, a first contactor, a first relay and a control unit, wherein the first power supply end is connected to the power grid, the second power supply end is connected to the online power supply, the first contactor is used to control the on-off of the circuit, and the first relay is used to control the conversion and isolation of the signal; The first contactor comprises a first contactor contact and a first contactor coil; The first power supply end is connected to the second power supply end through the first contactor contact, and the first power supply end is also connected to the first contactor coil through the first relay; The control unit controls turning on and off of the first relay.

2. The switch circuit according to claim 1, characterized in that: It also includes an auxiliary power supply. The first power supply end is connected to the second power supply end and the auxiliary power supply respectively through the first contactor contacts. The auxiliary power supply is connected to the control unit and is used to provide working power for the control unit. The contacts of the first relay are normally closed contacts.

3. The switch circuit according to claim 1 or 2, characterized in that: The first power supply end is also connected to a user load via the first contactor contact.

4. The switch circuit according to claim 1, characterized in that: The switch circuit also includes a first circuit breaker, and the first power supply end is connected to the power grid through the first circuit breaker, wherein the first circuit breaker is used to disconnect the current path in the circuit, the contacts of the first relay are normally closed contacts, and the contacts of the first contactor are normally open contacts.

5. The switch circuit according to claim 1, characterized in that: The switch circuit further comprises a third power supply terminal, a second contactor and a second relay, wherein the second contactor is used to control the on and off of the circuit, and the second relay is used to control the conversion and isolation of the signal; The second contactor comprises a second contactor contact and a second contactor coil; The third power supply end is connected to the second power supply end through the second contactor contact, and the third power supply end is also connected to the second contactor coil through the second relay; The control unit is also used to control the on and off of the second relay.

6. The switch circuit according to claim 5, characterized in that: It also includes an auxiliary power supply and a power load. The third power supply end is respectively connected to the second power supply end, the auxiliary power supply and the user load through the second contactor contacts. The auxiliary power supply is connected to the control unit to provide working power for the control unit.

7. The switch circuit according to claim 5 or 6, characterized in that: The switch circuit further includes a third relay, and the second contactor coil is connected to the second power supply end via the third relay. The control unit is further used to control the on and off of the contacts of the third relay.

8. The switch circuit according to claim 5 or 6, characterized in that: The switching circuit also includes a second circuit breaker, and the third power supply end is connected to the oil engine or the intelligent load through the second circuit breaker, wherein the second circuit breaker is used to disconnect the current path in the circuit, the contacts of the second relay are normally closed contacts, and the contacts of the second contactor are normally open contacts.

9. The switch circuit according to claim 2, characterized in that: The switch circuit further comprises a semiconductor switch tube, and the semiconductor switch tube is connected in parallel with the contact of the first relay; The control unit is used to control the semiconductor switch tube to be turned on and control the contacts of the first relay to be disconnected when the auxiliary power supply is powered.

10. The switch circuit according to claim 9, characterized in that: The semiconductor switch tube is any one of the following: a power diode, a field effect transistor, a bipolar junction transistor, an insulated gate bipolar transistor and a thyristor.

11. The switch circuit according to claim 1, characterized in that: The grid-connected power supply includes one or more of photovoltaic, wind, nuclear or energy storage power supplies, and the second power supply end is connected to the grid-connected power supply via an inverter.

12. The switch circuit according to claim 1, characterized in that: The switch circuit further includes a current fast shutoff unit, which is connected in parallel to both ends of the first relay, and the control unit controls the on and off of the current fast shutoff unit.

13. The switch circuit according to claim 12, characterized in that: The fast current shutdown unit includes a first IGBT and a second IGBT, the emitter of the first IGBT is connected to the emitter of the second IGBT, and the collector of the first IGBT and the collector of the second IGBT are respectively connected to the two ends of the first relay; or, the fast current shutdown unit includes a first IGBT and a second IGBT, the collector of the first IGBT is connected to the collector of the second IGBT, and the emitter of the first IGBT and the emitter of the second IGBT are respectively connected to the two ends of the first relay.

14. The switch circuit according to claim 13, characterized in that: The control unit controls the first IGBT and the second IGBT to be closed or opened simultaneously, so as to bidirectionally conduct or bidirectionally disconnect the branch where the first IGBT and the second IGBT are located.

15. The switch circuit according to claim 1, characterized in that: The response time of the current fast shut-off unit is less than 0.1 ms.

16. An off-grid circuit, comprising an on-grid power supply and a power grid, characterized in that: It also includes a switch circuit as claimed in any one of claims 12 to 15, wherein the first contactor contact is connected between the on-grid power supply and the power grid.

17. The off-grid circuit according to claim 16, characterized in that: After the first relay is energized, the first contactor coil is energized to control the first contactor contact to close, and the online power supply is connected to the power grid; when the online power supply is connected to the power grid, the control unit controls the first IGBT and the second IGBT to close at the same time, and controls the first relay to open.

18. The off-grid circuit according to claim 17, characterized in that: When the grid side is short-circuited, the control unit controls the first IGBT and the second IGBT to be turned off simultaneously.

19. The off-grid circuit according to claim 16, characterized in that: The off-grid circuit also includes a detection unit, which is connected to the control unit. The detection unit detects in real time whether a short circuit occurs on the grid side. The control unit controls the first IGBT and the second IGBT to close or open simultaneously according to the detection result of the detection unit.

20. The off-grid circuit according to claim 19, characterized in that: The detection unit determines whether a short circuit occurs on the grid side by detecting the voltage and / or instantaneous active power of the grid in real time.

21. An off-grid circuit, comprising an on-grid power supply and a power grid, characterized in that: It also includes the switching circuit as described in any one of claims 1 to 11, and the off-grid circuit also includes a sampling calculation unit, which samples the grid voltage in real time and compares the sampled grid voltage with a voltage threshold. When the grid voltage sampled by the sampling calculation unit is lower than the voltage threshold, the control unit disconnects the first relay.

22. The off-grid circuit according to claim 21, characterized in that: The switch circuit also includes a current fast shutdown unit, which is connected in parallel at both ends of the first relay. The control unit controls the conduction and disconnection of the current fast shutdown unit. When the sampling calculation unit samples that the grid voltage is lower than the voltage threshold, the control unit disconnects the first relay or the current fast shutdown unit.

23. The switch circuit according to claim 22, characterized in that: The fast current shutdown unit includes a first IGBT and a second IGBT, the emitter of the first IGBT is connected to the emitter of the second IGBT, and the collector of the first IGBT and the collector of the second IGBT are respectively connected to the two ends of the first relay; or, the fast current shutdown unit includes a first IGBT and a second IGBT, the collector of the first IGBT is connected to the collector of the second IGBT, and the emitter of the first IGBT and the emitter of the second IGBT are respectively connected to the two ends of the first relay.

24. The switch circuit according to claim 23, characterized in that: The control unit controls the first IGBT and the second IGBT to be closed or opened simultaneously, so as to bidirectionally conduct or bidirectionally disconnect the branch where the first IGBT and the second IGBT are located.

25. The switch circuit according to claim 22, characterized in that: The response time of the current fast shut-off unit is less than 0.1 ms.

26. The off-grid circuit according to claim 22, characterized in that: The sampling calculation unit is also used to sample the grid voltage and grid current in real time before the grid power supply is connected to the grid. The control unit is also used to turn on the current fast shutdown unit when the grid voltage is higher than the voltage threshold and the grid current is lower than the current threshold.

27. The off-grid circuit according to claim 22, characterized in that: The voltage threshold is any value between 50% and 95% of the reference grid voltage.

28. The off-grid circuit according to claim 22, characterized in that: The voltage threshold is any value between 5% and 50% of the reference grid voltage.

29. An off-grid control method, applied to the off-grid circuit of claim 16, characterized in that: The following steps are involved: S1, after the grid is powered on, the first relay is turned on, after the first contactor coil is powered on, the first contactor contact is closed, and the online power supply is connected to the grid; S2. After the on-grid power supply is connected to the power grid, the current fast shut-off unit is controlled to be closed, and the first relay is controlled to be disconnected.

30. The off-grid and on-grid control method according to claim 29, characterized in that: The following steps are also included: S3. When the grid side is short-circuited, the control unit controls the first IGBT and the second IGBT to be disconnected simultaneously, and the branches where the first IGBT and the second IGBT are located are bidirectionally disconnected.

31. The off-grid and on-grid control method according to claim 29, characterized in that: In step S3, a detection unit is used to detect in real time whether a short circuit occurs on the grid side.

32. An off-grid control method, applied to the off-grid circuit of claim 21, characterized in that: The following steps are involved: L1. Before the grid power source is connected to the grid, the sampling calculation unit samples the grid voltage and grid current in real time. When the grid voltage is higher than the voltage threshold and the grid current is lower than the current threshold When the first relay or the current fast shutoff unit is turned on, the control unit controls the first relay or the current fast shutoff unit to be turned on; L2. After the online power supply is connected to the power grid, the sampling and calculation unit samples the power grid voltage in real time. When the sampling and calculation unit detects that the power grid voltage is lower than the voltage threshold, the control unit controls the first relay or the current fast shutdown unit to disconnect.

33. An off-grid control method, applied to the off-grid circuit of claim 21, characterized in that: The following steps are involved: L1. Before the online power supply is connected to the power grid, the sampling and calculation unit samples the grid voltage and grid current in real time. When the grid voltage is higher than the voltage threshold and the grid current is lower than the current threshold, the control unit controls the first relay to be turned on; L2. After the online power supply is connected to the power grid, the control unit controls the current fast shutdown unit to be turned on and then the control unit controls the first relay to be turned off. The sampling and calculation unit samples the grid voltage in real time. When the sampling and calculation unit detects that the grid voltage is lower than the voltage threshold, the control unit controls the current fast shutdown unit to be turned off.

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