Grid-connected and off-grid switching device and power system

Abstract

The invention discloses a grid-connected and off-grid switching device and an electric power system, and belongs to the technical field of electric power. The grid-connected and off-grid switching device comprises a main loop; the main switch is arranged in the main loop; the power supply module is connected with the main loop, and the power supply module is configured to supply power by utilizing electric energy of at least two of a power grid side, a load side and an external power supply interface in a switchable manner; the short circuit detection unit is connected with the load side of the main loop and the power supply module, and is configured to detect impedance between lines of the load side based on power supply of the power supply module and provide a detection signal; the control unit is configured to determine whether a short-circuit fault exists on the load side or not based on the detection signal under the condition that the main switch is switched off; and controlling the main switch to be closed under the condition that the load side has no short circuit fault. Whether the power distribution system at the load side has a short-circuit fault can be monitored before the main switch is closed, and the power grid cannot be disconnected within a certain period of time when the power grid is abnormal through multi-side power supply.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electric power, and particularly relates to a parallel-off-grid switching device and an electric power system. BACKGROUND

[0002] The light storage system is the first choice for solving the instability of the household power grid in areas due to its outstanding low-carbon environmental protection. Under the condition that the photovoltaic power is sufficient during the day, the surplus power generated by the photovoltaic cell will be preferentially stored in the battery energy storage system by the energy management system, and then delivered to the power grid or household load when the household load demand or power grid dispatching is needed. Or when the power grid fails, the light storage system will operate independently as a small micro-grid system to support the power load of a household. When the power grid fails, the energy management system will cut off the switch of the parallel-off-grid switching device on the grid side, and the battery will release electricity to the household power load.

[0003] The power connection between the light storage system and the grid side is controlled through the parallel-off-grid switching device, but the current parallel-off-grid switching device has safety hazards in the working process, and it is difficult to maintain off-grid when the power grid is abnormal. SUMMARY

[0004] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a parallel-off-grid switching device and an electric power system, which can monitor whether the distribution system on the load side has a short-circuit fault before the main switch is attracted, and can maintain off-grid for a certain period of time when the power grid is abnormal through multi-side power supply.

[0005] In a first aspect, the present application provides a parallel-off-grid switching device, comprising: a main circuit; a main switch, arranged in the main circuit and defining a grid side and a load side on the main circuit; a power supply module, connected with the main circuit, the power supply module being configured to supply power using the electric energy of at least two of the grid side, the load side and an external power supply interface, the external power supply interface being used for connecting an external power source; a short-circuit detection unit, connected with the load side of the main circuit and the power supply module, and configured to detect the impedance between the lines of the load side based on the power supply of the power supply module and provide a detection signal; a control unit, connected with the power supply module, the short-circuit detection unit and the main switch, and configured to determine whether the load side has a short-circuit fault based on the detection signal when the main switch is open, and to control the main switch to close when the load side has no short-circuit fault.

[0006] According to one embodiment of this application, the short-circuit detection unit includes a switch configured to connect or disconnect the impedance between the lines on the load side, and to provide corresponding detection signals in the connected and disconnected states based on the power supply of the power module. The control unit is also configured to determine whether there is a short circuit fault on the load side based on the comparison results between the detection signals corresponding to the access and disconnection situations.

[0007] According to one embodiment of this application, the off-grid switching device further includes a self-test unit connected to a short-circuit detection circuit and configured to controllably provide an impedance to the short-circuit detection circuit to adjust the detection signal. The control unit is also configured to determine whether the switch in the short-circuit detection unit is stuck based on the detection signals before and after the self-test unit is adjusted.

[0008] According to one embodiment of this application, the short-circuit detection unit includes: The first resistor is connected between the lines on the load side of the main circuit; The first switch, the first end of the first switch is connected to the first end of the first resistor; The second switch has its first terminal connected to the second terminal of the first resistor. The voltage divider resistor string has its first terminal node connected to the first polarity node of the power module, and its second terminal node connected to the second polarity node of the power module. The voltage divider resistor string also includes a second resistor, the first terminal of which is connected to the second terminal of the first switch, and the second terminal of which is connected to the second terminal of the second switch. The detection unit is connected to both ends of the resistors in the voltage divider resistor string except for the second resistor, and is configured to detect the voltage or current of the corresponding resistor. The self-test unit is connected to a series of voltage divider resistors and is configured to controllably adjust the voltage division ratio of the voltage divider resistor series.

[0009] According to one embodiment of this application, the voltage divider resistor string further includes a third resistor and a fourth resistor. The first end of the third resistor is connected to the first polarity node of the power module, the second end of the third resistor is connected to the first end of the second resistor, the first end of the fourth resistor is connected to the second polarity node of the power module, and the second end of the fourth resistor is connected to the second end of the second resistor. The self-test unit includes: The fifth resistor has its first terminal connected to the first polarity node of the power module. The sixth resistor has its first terminal connected to the second polarity node of the power module. The third switch, the first end of the third switch is connected to the second end of the fifth resistor, and the second end of the third switch is connected to the first end of the second resistor; The fourth switch has its first terminal connected to the second terminal of the sixth resistor, and its second terminal connected to the second terminal of the second resistor.

[0010] According to one embodiment of this application, the short-circuit detection unit further includes: The DC isolated power supply has its input side connected to the output side of the power module, and its output side is connected to the first terminal node and the first terminal node of the voltage divider resistor string, respectively.

[0011] According to one embodiment of this application, the power module includes: The anti-reverse power supply circuit has a first input terminal, a second input terminal, a third input terminal, and an output terminal. The first input terminal of the anti-reverse power supply circuit is connected to an external power supply interface. The first AC-DC converter unit has its AC side connected to the main circuit's grid side and its DC side connected to the second input terminal of the anti-reverse current circuit. The second AC-DC converter unit has its AC side connected to the load side of the main circuit and its DC side connected to the third input terminal of the anti-reverse current circuit. The power supply unit has its input side connected to the output terminal of the anti-backflow circuit, and its output side is used to provide electrical energy.

[0012] According to one embodiment of this application, the first AC-DC conversion unit includes: The electromagnetic filter unit has its first side connected to the power grid side of the main circuit. The fifth switch, the first side of the fifth switch is connected to the second side of the electromagnetic filter unit; The AC-DC converter circuit has its AC side connected to the second side of the fifth switch, and its DC side connected to the input side of the power supply unit.

[0013] According to one embodiment of this application, the fifth switch includes a relay, the switch contacts of which are connected between the AC side of the AC-DC conversion circuit and the second side of the electromagnetic filter unit, and the coil of the relay is connected to an external power supply interface.

[0014] Secondly, this application provides a power system including the aforementioned grid-connected / off-grid switching device.

[0015] According to one embodiment of this application, the power system further includes a photovoltaic energy storage system and a distribution box. The distribution box is equipped with an in-home power distribution unit, an electrical instrument panel, and an electricity meter. The in-home power distribution unit is connected to the load end of the photovoltaic energy storage system and the electrical instrument panel, respectively. The load side of the off-grid switching device is connected to the load end of the electrical instrument panel, and the grid side of the off-grid switching device is connected to the first end of the electricity meter. The second end of the electricity meter is connected to the grid end of the electrical instrument panel.

[0016] According to one embodiment of this application, the photovoltaic energy storage system includes multiple photovoltaic modules and an inverter-energy storage unit, which is connected to the household power distribution unit and the grid-connected / off-grid switching device, respectively. Each photovoltaic module is connected to the input side of the inverter-energy storage unit; or, Some photovoltaic modules are connected to the input side of the inverter-energy storage unit, while others are connected to the household power distribution unit via independent inverters.

[0017] According to the grid connection and off-grid switching device and power system of this application, a load-side short-circuit detection unit is added to the grid connection and off-grid switching device, so that the grid connection and off-grid switching device can monitor whether there is a short-circuit fault in the power distribution system on the load side before the main switch is closed. Moreover, by using power from at least two of the grid side, load side and external power supply interface, it can be ensured that the grid will not disconnect for a certain period of time when the grid experiences a drop in power.

[0018] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0019] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the on-grid / off-grid switching device provided in the embodiments of this application; Figure 2 This is a schematic diagram of the short-circuit detection circuit provided in the embodiments of this application; Figure 3 This is a schematic diagram of the power module provided in an embodiment of this application; Figure 4 This is a schematic diagram of the structure of an integrated device provided in an embodiment of this application; Figure 5 This is one of the structural schematic diagrams of the power system provided in the embodiments of this application; Figure 6 This is the second schematic diagram of the power system provided in the embodiments of this application.

[0020] Figure label: Main circuit 100, main switch 200, power module 300, power supply unit 310, electromagnetic filter unit 320, AC / DC conversion circuit 330, AC / DC power supply 340, short circuit detection unit 400, detection unit 410, DC isolation power supply 420, control unit 500, self-test unit 600, interface unit 700, external connector 800, metering unit 900, voltage detection unit 1000, drive unit 1100, WiFi unit 1200, first to fifth switches K1~K5, first to fifth resistors R1~R5, first to second connectors A1~A2. Detailed Implementation

[0021] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0022] In the following description, a "circuit" refers to a conductive loop consisting of at least one element or sub-circuit connected by an electrical or electromagnetic link. When an element or circuit is said to be "coupled to" or "connected to" another element, or when an element / circuit is said to be "coupled at" or "connected at" two nodes, it can be directly coupled to or connected to the other element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there are no intermediate elements between them.

[0023] In the description, the terms "first," "second," etc., are used to distinguish similar objects, not to describe a specific order or sequence. It should be understood that such numerical descriptors can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0024] Furthermore, the use of terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0025] In related technologies, when a photovoltaic-storage system operates off-grid, after the computer in the battery storage system is used up and it is nighttime with no photovoltaic power, it can only wait for the grid to restore power to charge the battery and for household loads to be used. At this time, it is necessary to close the grid-side switch of the off-grid switching device. However, if an abnormality occurs in the circuit, such as a short circuit fault, it will cause a short circuit current (often up to 22kA) at the moment the switch is closed, causing electrical hazards such as overheating, fire, or arcing in the household circuit.

[0026] Furthermore, grid-connected and off-grid switching devices need to comply with local grid code requirements and meet grid testing requirements for high-voltage and low-voltage switching, such as maintaining grid connection for more than 10 seconds at 0% voltage. However, since grid-connected and off-grid switching devices draw power from the grid's AC source, it is difficult for them to remain connected when the grid experiences an anomaly.

[0027] To address this, this application proposes a grid-connected switching device and a power system. The grid-connected switching device includes a load-side short-circuit detection unit, enabling it to monitor whether there is a short-circuit fault in the power distribution system on the load side before closing the main switch. Furthermore, by using power from at least two of the grid side, the load side, and the external power supply interface, it can ensure that the device remains connected to the grid for a certain period of time even when the grid experiences a voltage drop anomaly.

[0028] Reference Figure 1 , Figure 1The structure of a grid-connected / off-grid switching device is shown. One embodiment of this application proposes a grid-connected / off-grid switching device. In this embodiment, the grid-connected / off-grid switching device includes a main circuit 100, a main switch 200, a power module 300, a short-circuit detection unit 400, and a control unit 500. The main switch 200 is disposed in the main circuit 100 and defines the grid side and the load side on the main circuit 100. The power module 300 is connected to the main circuit 100 and is configured to switchably utilize power from at least two of the grid side, the load side, and an external power supply interface for power supply. The external power supply interface is used to connect to an external power source. The short-circuit detection unit 400 is connected to the load side of the main circuit 100 and the power module 300, and is configured to detect the impedance between the lines on the load side based on the power supply of the power module 300, and provide a detection signal. The control unit 500 is connected to the power module 300, the short-circuit detection unit 400, and the main switch 200, and is configured to determine whether there is a short-circuit fault on the load side based on the detection signal when the main switch 200 is open; and to control the main switch 200 to close when there is no short-circuit fault on the load side.

[0029] The main circuit 100 is used to connect the photovoltaic energy storage system and the power grid. The main circuit 100 may include a single-phase AC phase line or a three-phase AC phase line. The portion of the main circuit 100 between the main switch 200 and the photovoltaic energy storage system is the load side, and the portion of the main circuit 100 between the main switch 200 and the power grid is the grid side.

[0030] The main switch 200 is installed on the main circuit 100 and controls the connection or disconnection between the photovoltaic energy storage system and the power grid by controlling the on / off state of the main circuit 100 lines. The main switch 200 may include multiple switchable parts, each of which is installed on a line of the main circuit 100. The main switch 200 may be a circuit breaker, a solid-state switch, or an integrated switch, etc.

[0031] The power module 300 is used to draw power and supply power to the short-circuit detection unit 400 and the control unit 500. In this embodiment, the power module 300 adopts at least two power drawing methods. The first method is that the power module 300 is connected to the load side of the main circuit 100 and draws power from the load side of the main circuit 100. The second method is that the power module 300 is connected to the grid side of the main circuit 100 and draws power from the grid side of the main circuit 100. The third method is that the power module 300 is equipped with an external power supply interface for connecting to an external power source, and the power module 300 draws power from the external power source. The external power source can be an inverter or battery pack in the photovoltaic energy storage system, etc.

[0032] Therefore, the power module 300 can provide a stable working power supply to the control unit 500 when the power grid is abnormal by drawing power from multiple sources, ensuring the operation of the grid-connected and off-grid switching device and realizing operation without disconnecting from the grid when the power grid is abnormal.

[0033] The detection signal can be a voltage signal or a current signal, which characterizes the impedance of the load side of the main circuit 100. Alternatively, the detection signal can directly characterize whether the load side of the main circuit 100 is short-circuited. For example, when the load side of the main circuit 100 is short-circuited, the detection signal is the first signal; when the load side of the main circuit 100 is not short-circuited, the detection signal is the second signal; the first signal and the second signal have different voltages or currents.

[0034] Before closing the main switch 200, the control unit 500 can send a detection control signal to the short-circuit detection unit 400. The short-circuit detection unit 400 responds to the detection control signal to perform short-circuit detection on the load side of the main circuit 100 and feeds back the detection signal. The control unit 500 determines whether there is a short circuit on the load side of the main circuit 100 based on the received detection signal. If there is a short circuit, it controls the main switch 200 to remain open and issues an alarm; if there is no short circuit, the main switch 200 is closed.

[0035] The control unit 500 can be implemented using an MCU (Microcontroller Unit) chip, a DSP (Digital Signal Processor) chip, an FPGA (Field-Programmable Gate Array), or a custom controller chip, etc.; the embodiments of this application do not limit the specific hardware implementation of the controller.

[0036] In this embodiment, the short-circuit detection unit 400 performs impedance detection on the load side of the main circuit 100 based on the power supply of the power module 300, independent of the operating status of the load side of the main circuit 100. This allows for detection of whether the load of the main circuit 100 is short-circuited before the main switch 200 is closed, reducing electrical hazards caused at the moment of closing.

[0037] In some embodiments, the short-circuit detection unit 400 includes a switch configured to connect or disconnect the impedance between the lines on the load side, and to provide corresponding detection signals in the connected and disconnected states based on the power supply of the power module 300; the control unit 500 is further configured to determine whether a short-circuit fault exists on the load side based on the comparison result between the corresponding detection signals in the connected and disconnected states.

[0038] The short-circuit detection unit 400 may include multiple switches connected to the load-side lines of the main circuit 100 to connect or disconnect the impedance between the load-side lines. For example, a switch may be connected to the positive line of the load side of the main circuit 100, and a switch may be connected to the negative line of the load side of the main circuit 100. When both switches are closed, the load line between the positive and negative lines is connected to the short-circuit detection unit 400; when both switches are open, the load line between the positive and negative lines is disconnected from the short-circuit detection unit 400.

[0039] Understandably, the short-circuit detection unit 400 is connected to the power supply module 300 and can provide a detection signal based on its own impedance. Due to the connection and disconnection of impedance between the lines on the load side, a short circuit on the load side of the main circuit 100 will cause a change in the impedance of the short-circuit detection unit 400, thereby causing a change in the detection signal; if there is no short circuit on the load side of the main circuit 100, there will be no change in the impedance of the short-circuit detection unit 400, and the detection signal will remain unchanged.

[0040] Therefore, the control unit 500 can determine whether there is a short circuit on the load side by comparing the detection signal when the impedance between the lines on the load side is connected with the detection signal when the impedance between the lines on the load side is disconnected. That is, if there is a change, the load side is short-circuited; if there is no change, the load side is not short-circuited.

[0041] As an example, the detection signal is a voltage signal. Assume the voltage signal is U1 when the impedance between the lines on the load side is connected, and U2 when the impedance between the lines on the load side is disconnected. The control unit 500 determines that the detection signal has changed and the load side is short-circuited when the difference between U1 and U2 is greater than a threshold; conversely, if the difference is less than or equal to the threshold, it determines that the detection signal has not changed and the load side is not short-circuited. The threshold value can be used to eliminate errors caused by signal fluctuations.

[0042] In some embodiments, the on-grid switching device further includes a self-test unit 600, which is connected to the short-circuit detection circuit 400 and configured to controllably provide an impedance to the short-circuit detection circuit 400 to adjust the detection signal; the control unit 500 is further configured to determine whether the switch in the short-circuit detection unit 400 is stuck based on the detection signal before and after adjustment by the self-test unit 600.

[0043] The self-test unit 600 performs a self-test before the short-circuit detection unit 400 detects the impedance on the load side of the main circuit 100 to determine whether the switch in the short-circuit detection unit 400 is stuck. If sticking occurs, the control signal sent by the control unit 500 to the switch in the short-circuit detection unit 400 will not have an actual control effect, and the switch will not actually operate. At this time, even if there is a short circuit on the load side of the main circuit 100, the detection signal received by the control unit 500 will be misinterpreted as unchanged, resulting in a false detection.

[0044] The self-test unit 600 may include a switch and a resistor. The switch controls the connection or disconnection of the resistor and the short-circuit detection circuit 400, allowing the short-circuit detection circuit 400 to determine whether its own switch is stuck by detecting the self-test unit 600. When the self-test unit 600 is connected or disconnected, if the detection signal received by the control unit 500 does not change, it can be determined that the switch within the short-circuit detection circuit 400 is stuck; if the detection signal received by the control unit 500 changes, it can be determined that the switch within the short-circuit detection circuit 400 is not stuck. The comparison process of the detection signals can be referred to the above.

[0045] Furthermore, the self-test unit 600 and the short-circuit detection circuit 400 are two sets of switches, thus allowing for four switching states. The control unit 500 can compare and analyze the detection signals under these four switching states. The meaning of the analysis results can be determined based on the compared detection signals, thereby ensuring that the main circuit 100 can be accurately detected for short circuits on the load side when there are no abnormalities in its own circuit, thus providing detection accuracy.

[0046] Reference Figure 2 , Figure 2 The structure of a short-circuit detection circuit 400 is shown. In this embodiment, the short-circuit detection unit 400 includes a first resistor R1, a first switch K1, a second switch K2, a voltage divider resistor string, and a detection unit 410. The first resistor R1 is connected between the lines on the load side of the main circuit 100; the first end of the first switch K1 is connected to the first end of the first resistor R1; the first end of the second switch K2 is connected to the second end of the first resistor R2; the first terminal of the voltage divider resistor string is connected to the first polarity terminal of the power supply module 300, and the second terminal of the voltage divider resistor string is connected to the second polarity terminal of the power supply module 300; the voltage divider resistor string includes a second resistor R2, the first end of the second resistor R2 is connected to the second end of the first switch K1, and the second end of the second resistor R2 is connected to the second end of the second switch K2; the detection unit 410 is connected to both ends of the resistors in the voltage divider resistor string except for the second resistor R2, and is configured to detect the voltage or current of the corresponding resistors; wherein, the self-test unit 600 is connected to the voltage divider resistor string and is configured to controllably adjust the voltage division ratio of the voltage divider resistor string.

[0047] As an example, the main circuit 100 is a three-phase AC line. The first end of the first resistor R1 can be connected to the first phase line on the load side of the main circuit 100, and the second end of the first resistor R1 can be connected to the second phase line on the load side of the main circuit 100. When the load side of the main circuit 100 is short-circuited, the two ends of the first resistor R1 are equivalent to being short-circuited, and the resistance between K1 and the second switch K2 is close to zero. When the load side of the main circuit 100 is not short-circuited, the resistance between the first switch K1 and the second switch K2 is the impedance of the first resistor R1 and the impedance of the load side of the main circuit 100 in parallel.

[0048] The first resistor R1 is connected in parallel with the second resistor R2 through the first switch K1 and the second switch K2. When the first switch K1 and the second switch K2 are closed, the first resistor R1, the second resistor R2, and the impedance of the load side of the main circuit 100 are connected in parallel. Therefore, the operation of the first switch K1 and the second switch K2 can adjust the voltage division ratio of the voltage divider resistor string. The detection unit 410 provides a detection signal based on the voltage division ratio of the voltage divider resistor string.

[0049] The voltage divider resistor string also includes at least one resistor connected in series with the second resistor R2. The detection unit 410 is used to detect the voltage or current of this resistor to provide a detection signal. When the first switch K1 and the second switch K2 are closed, a short circuit or no short circuit on the load side of the main circuit 100 causes the voltage divider resistor string to have different voltage division ratios, thereby causing different voltage or current values ​​in the detection signal.

[0050] In some embodiments, the voltage divider resistor string further includes a third resistor R3 and a fourth resistor R4. The first end of the third resistor R3 is connected to the first polarity node of the power module 300, and the second end of the third resistor R3 is connected to the first end of the second resistor R2. The first end of the fourth resistor R4 is connected to the second polarity node of the power module 300, and the second end of the fourth resistor R4 is connected to the second end of the second resistor R2. The self-test unit includes a fifth resistor R5, a sixth resistor R6, a third switch K3, and a fourth switch K4. The first end of the fifth resistor R5 is connected to the first polarity node of the power module 300. The first end of the sixth resistor R6 is connected to the second polarity node of the power module 300. The first end of the third switch K3 is connected to the second end of the fifth resistor R5, and the second end of the third switch K3 is connected to the first end of the second resistor R2. The first end of the fourth switch K4 is connected to the second end of the sixth resistor R6, and the second end of the fourth switch K4 is connected to the second end of the second resistor R2.

[0051] As an example, the detection unit 410 is connected to the third resistor R3 to detect the voltage across the third resistor R3. The third switch K3 and the fourth switch K4 can be integrated relays, and the third switch K3 and the fourth switch K4 are synchronously closed or opened. The control unit 500 controls the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4, and determines whether there is a short circuit on the load side of the main circuit 100 based on the detection signal fed back by the detection unit 410.

[0052] The first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 can be relays or IGBTs (Insulated Gate Bipolar Transistors), or other types of switching devices.

[0053] As an example, the process of detecting whether there is a short circuit on the load side of the main circuit 100 can be as follows: Step 1: Control the first switch K1, the second switch K2, the third switch K3 and the fourth switch K4 to be open, and measure the voltage VL1=(V1*R3) / (R1+R2+R3); The second step is to open the first switch K1 and the second switch K2, and close the third switch K3 and the fourth switch K4. The voltage VI1' is measured as [(V1*R3*RS2) / (R3+RS2)] / [(R1*RS) / (R1+RS)+(R3*RS2) / (R3+RS2)+R2]. The third step is to compare the values ​​of VI1 and VI1' to determine whether the third switch K3 and the fourth switch K4 are stuck together. If they are stuck together, a fault will be reported; otherwise, proceed to the next step. If VI1 and VI1' are equal, it means that the third switch K3 and the fourth switch K4 are stuck together; otherwise, they are not stuck together.

[0054] Step 4: Close the first switch K1 and the second switch K2, and open the third switch K3 and the fourth switch K4. Measure the voltage VI2 = (V1*R3) / {R1+R3+[R2*(R5*Rx) / (R5+Rx)] / [R2+(R5*Rx) / (R5+Rx)]}; where Rx is the impedance of the load side of the main circuit 100.

[0055] Step 5: By comparing the values ​​of VI1 and VI2, it can be determined whether RL2 and RL3 are stuck together. If they are stuck together, a fault is reported; if they are normal, proceed to the next step. If VI1 and VI2 are equal, it means that the first switch K1 and the second switch K2 are stuck together; otherwise, they are not stuck together.

[0056] Step 6: Close the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4, and measure the voltage VI3 = [(V1*R3*RS2) / (R3+RS2)] / {(R1*RS) / (R1+RS)+(R3*RS2) / (R3+RS2)+[R2*(R5* Rx) / (R5+Rx)] / [ R2+(R5*Rx) / (R5+Rx)]}; Step 7: By comparing the values ​​of VI2 and VI3, it can be determined whether there is a short circuit fault between L1 and L2 on the load side.

[0057] Of course, the detection process for whether the load side of the main circuit 100 is short-circuited can also be carried out by sampling voltage comparison, which can be set according to needs.

[0058] In some embodiments, the short-circuit detection unit 400 further includes a DC isolation power supply 420, the input side of which is connected to the output side of the power module 300, and the output side of which is connected to the first terminal node and the first terminal node of the voltage divider resistor string, respectively.

[0059] Using a DC isolation power supply 420 to provide voltage to the voltage divider resistor string can isolate the interference from the power module 300, provide a stable voltage to the voltage divider resistor string, and ensure the stability of the detection signal.

[0060] In addition, the short-circuit detection unit 400 also includes a power supply detection unit 430. The input terminal of the power supply detection unit 430 is connected to the output side of the DC isolation power supply 420, and the output terminal of the power supply detection unit 430 is connected to the control unit 500. The power supply detection unit 430 is used to detect the output voltage of the DC isolation power supply 420, can provide a reference voltage to the control unit 500, and simultaneously detect whether the output of the DC isolation power supply 420 is abnormal.

[0061] Reference Figure 3 , Figure 3 The structure of a power supply module 300 is shown. In this embodiment, the power supply module 300 includes a backflow prevention circuit, a first AC-DC converter unit, a second AC-DC converter unit, and a power supply unit 310. The backflow prevention circuit has a first input terminal, a second input terminal, a third input terminal, and an output terminal. The first input terminal of the backflow prevention circuit is connected to an external power supply interface. The AC side of the first AC-DC converter unit is connected to the power grid side of the main circuit 100, and the DC side of the first AC-DC converter unit is connected to the second input terminal of the backflow prevention circuit. The AC side of the second AC-DC converter unit is connected to the load side of the main circuit 100, and the DC side of the second AC-DC converter unit is connected to the third input terminal of the backflow prevention circuit. The input side of the power supply unit 310 is connected to the output terminal of the backflow prevention circuit, and the output side of the power supply unit is used to provide electrical energy.

[0062] The first AC-DC converter unit draws power from the grid side of the main circuit 100, and can obtain power from the grid when the grid voltage is normal to provide power to the power supply unit 310. The second AC-DC converter unit draws power from the load side of the main circuit 100, and can obtain power from the photovoltaic energy storage system to provide power to the power supply unit 310. The external power supply interface is used to obtain power from an external power source to provide power to the power supply unit 310.

[0063] The on / off-grid switching device includes an interface unit 700, and an external power supply interface can be integrated into the interface unit 700. In addition to the external power supply interface, the interface unit 700 may also include 485 communication ports such as RJ45 port and DI / DO port, and each interface can be connected to external devices through an external connector 800.

[0064] The interface unit 700 can also integrate other interactive components, such as manual reset levers and reset buttons. These interactive components are connected to the control unit 500 to provide interactive signals. For example, the control unit 500 can respond to the signal from the manual reset lever to control the reset of each switch; the control unit 500 can also respond to the signal from the reset button to reset and initialize the grid-connected switching device.

[0065] The anti-reverse current circuit is used to prevent backflow of current from the input terminals from damaging electronic components. The anti-reverse current circuit can connect to a power source from the first AC-DC converter unit, the second AC-DC converter unit, and an external power supply interface, transmitting the power supplied by one of these sources to the power supply unit 310. The power supply unit 310 may include voltage conversion circuits and voltage regulation circuits, etc.

[0066] The anti-reverse current circuit can include multiple diodes. Each diode can be set on the output side of the first AC-DC conversion unit, the output side of the second AC-DC conversion unit, and the external power supply interface, respectively. The diodes limit the unidirectional flow of current and prevent current reverse current.

[0067] As an example, when the entire power system is in a prolonged abnormal grid state with no normal power supply, and the photovoltaic-storage system is depleted, and the photovoltaic modules cannot generate power normally due to weather or nighttime, the entire power system is in a state of power outage. When power is suddenly restored to the grid, the first AC-DC converter can normally output voltage, and the off-grid switching device starts working normally, activating the short-circuit detection function. If no abnormality is detected, the main switch 20 is closed to energize the AC side of the photovoltaic-storage system, at which point the system can begin normal operation.

[0068] Alternatively, in a power outage situation, after the photovoltaic modules begin generating electricity, the second AC-DC converter draws power from the photovoltaic-storage system, starts operating normally, and activates the short-circuit detection function. If no abnormality is detected, the main switch 200 is closed to restore power to the grid. Alternatively, power can be drawn from an external power source, and the off-grid switching device maintains basic functions.

[0069] In some embodiments, the first AC-DC conversion unit includes an electromagnetic filter unit 320, a fifth switch K5, and an AC-DC conversion circuit 330. The first side of the electromagnetic filter unit 320 is connected to the power grid side of the main circuit 100; the first side of the fifth switch K5 is connected to the second side of the electromagnetic filter unit 320; the AC side of the AC-DC conversion circuit 330 is connected to the second side of the fifth switch K5; and the DC side of the AC-DC conversion circuit 330 is connected to the input side of the power supply unit 310.

[0070] like Figure 3 As shown, the AC-DC conversion circuit 330 is used to convert AC power into DC power to provide power to the power supply unit 310, the electromagnetic filter unit 320 is used to improve the stability of the power supply, and the fifth switch K5 is used to control the start and stop of the first AC-DC conversion unit.

[0071] As another example, the fifth switch K5 includes a relay, the relay's switch contacts being connected between the AC side of the AC-DC conversion circuit and the second side of the electromagnetic filter unit, and the relay's coil being connected to an external power supply interface.

[0072] In this example, the fifth switch K5 is controlled by an external power supply interface. When power is supplied to the external power supply interface, the fifth switch K5 is open; when power is not supplied to the external power supply interface, the fifth switch K5 is closed. This ensures that each power supply circuit operates in an orderly manner.

[0073] As another example, the control terminal of the fifth switch K5 is connected to the control unit 500. The control unit 500 controls the fifth switch K5 to close, and the first AC-DC conversion unit is turned on. This ensures that each power supply path operates in an orderly manner.

[0074] It should be noted that the second AC-DC conversion unit can adopt the same structure as the first AC-DC conversion unit, or it can adopt a different structure.

[0075] One embodiment of this application also provides a power system including the aforementioned grid-connected / off-grid switching device.

[0076] In some embodiments, the grid-connected / off-grid switching device can be integrated with some functional components in the power system. For example, the grid-connected / off-grid switching device can be integrated with an electricity meter.

[0077] Reference Figure 4 , Figure 4The structure of an integrated device is shown. In this embodiment, the integrated device includes the aforementioned grid-connected / off-grid switching device, metering unit 900, and voltage detection unit 1000. Voltage detection unit 1000 is connected to metering unit 900, and metering unit 900 is connected to control unit 500.

[0078] The integrated device is connected to a first connector A1 and a second connector A2. One port of the first connector A1 is used to connect to the power grid, and the other port is used to connect to the photovoltaic energy storage system. The ports of the first connector A1 and the second connector A2 are connected accordingly. The main switch 200 is located on the line between one pair of ports.

[0079] Metering unit 900 is connected to another pair of port lines for detecting the power supply on the grid side. Voltage detection unit 1000 is connected to the grid side of main switch 200 for detecting grid voltage. Control unit 500 receives the detection data from metering unit 900 and voltage detection unit 1000, monitors the voltage and power information of the grid in real time, and performs grid connection / disconnection control based on the detection data, or transmits the data to external devices.

[0080] The integrated device also includes a drive unit 1100, which is connected to the main switch 200 and the control unit 500. The drive unit 1100 receives control signals transmitted from the control unit 500 to drive the main switch 200 to close or open.

[0081] The integrated device may also include a WiFi unit 1200, which is connected to the control unit 500. The control unit 500 can communicate with external devices by driving the WiFi unit 1200 to transmit information.

[0082] It should be noted that, Figure 4 The AC / DC power supply 340 shown is used to obtain electrical energy from the grid side and the load side of the main circuit 100, respectively, and includes the aforementioned first AC-DC conversion circuit and second AC-DC conversion unit.

[0083] In some embodiments, the power system further includes a photovoltaic energy storage system and a distribution box 10. The distribution box 10 is provided with an in-home power distribution unit 11, an electrical instrument panel 12, and an electricity meter 13. The in-home power distribution unit 11 is connected to the load end of the photovoltaic energy storage system and the electrical instrument panel 12, respectively. The load side of the off-grid switching device 30 is connected to the load end of the electrical instrument panel 12, and the grid side of the off-grid switching device 30 is connected to the first end of the electricity meter 13. The second end of the electricity meter 13 is connected to the grid end of the electrical instrument panel 12.

[0084] This embodiment provides a power system structure that can operate as a home microgrid system. A distribution box 10 connects to the power grid and a photovoltaic-storage system for power management. An in-home distribution unit 11 can connect to the home wiring to control the transmission of power from the power grid and / or the photovoltaic-storage system's computer to the home wiring.

[0085] The distribution box 10 is equipped with an electrical instrument panel 12 for installing electricity meters 13 to measure the electricity consumed from the power grid. The electricity meters 13 and the grid-connected / off-grid switching device 30 are integrated using a detachable connection; the integrated circuit structure can be referenced... Figure 4 As described above, this embodiment will not be repeated here. Of course, the electricity meter 13 and the grid-connected / off-grid switching device 30 can also be integrated into the same housing.

[0086] Reference Figure 5 , Figure 5 The structure of a power system is shown. As an example, the photovoltaic-energy storage system includes multiple photovoltaic modules 21 and an inverter-energy storage unit 22, which is connected to the household power distribution unit 11 and the grid-connected / off-grid switching device 30, respectively; each photovoltaic module 21 is connected to the input side of the inverter-energy storage unit 22.

[0087] In this example, each photovoltaic module 21 is managed and controlled by the inverter-energy storage unit 22, which helps improve energy management efficiency. The inverter-energy storage unit 22 is an energy conversion and control device that integrates an energy storage battery system, an energy management unit, and a bidirectional inverter into a single device. It can realize the storage, conversion, and intelligent scheduling of electrical energy, thereby improving energy utilization efficiency and grid optimization.

[0088] The inverter-energy storage unit 22 can communicate with the grid-connected and off-grid switching device 30. The grid-connected and off-grid switching device 30 can transmit the grid-side information and load-side information it detects to the inverter-energy storage unit 22, which facilitates energy management by the inverter-energy storage unit 22.

[0089] Reference Figure 6 , Figure 6 Another power system structure is shown. As another example, the energy storage system includes multiple photovoltaic modules 21 and an inverter-energy storage unit 22. Some of the photovoltaic modules 21 are connected to the input side of the inverter-energy storage unit 22, and some of the photovoltaic modules 21 are connected to the household distribution unit 11 through an independent inverter.

[0090] In this example, some of the photovoltaic modules 21 are managed and controlled by the inverter energy storage unit 22, while the other part of the photovoltaic modules 21 are directly connected to the household power distribution unit 11, making energy distribution more flexible.

[0091] In this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0092] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A grid-connected / off-grid switching device, characterized in that, include: Main circuit; A main switch is installed in the main circuit and defines the grid side and the load side on the main circuit; A power module is connected to the main circuit. The power module is configured to switchably use electrical energy from at least two of the grid side, the load side, and the external power supply interface for power supply. The external power supply interface is used to connect to an external power source. A short-circuit detection unit is connected to the load side of the main circuit and the power supply module, and is configured to detect the impedance between the lines on the load side based on the power supply of the power supply module, and provide a detection signal; The control unit is connected to the power module, the short-circuit detection unit, and the main switch, and is configured to determine whether there is a short-circuit fault on the load side based on the detection signal when the main switch is open; and to control the main switch to close when there is no short-circuit fault on the load side.

2. The grid-connected / off-grid switching device according to claim 1, characterized in that, The short-circuit detection unit includes a switch configured to connect or disconnect the impedance between the lines on the load side, and provides corresponding detection signals in the connected and disconnected states based on the power supply of the power module. The control unit is further configured to determine whether there is a short circuit fault on the load side based on the comparison result between the detection signals corresponding to the access situation and the cut-off situation.

3. The grid-connected / off-grid switching device according to claim 2, characterized in that, The grid-connected / off-grid switching device further includes a self-test unit, which is connected to the short-circuit detection circuit and configured to controllably provide an impedance to the short-circuit detection circuit to adjust the detection signal. The control unit is further configured to determine whether the switch in the short-circuit detection unit is stuck based on the detection signals before and after the self-test unit is adjusted.

4. The grid-connected / off-grid switching device according to claim 3, characterized in that, The short-circuit detection unit includes: The first resistor is connected between the lines on the load side of the main circuit; A first switch, wherein the first end of the first switch is connected to the first end of the first resistor; A second switch, wherein the first end of the second switch is connected to the second end of the first resistor; A voltage divider resistor string, wherein the first terminal node of the voltage divider resistor string is connected to the first polarity node of the power module, and the second terminal node of the voltage divider resistor string is connected to the second polarity node of the power module; the voltage divider resistor string includes a second resistor, the first terminal of the second resistor is connected to the second terminal of the first switch, and the second terminal of the second resistor is connected to the second terminal of the second switch; The detection unit is connected to both ends of the resistors in the voltage divider resistor string except for the second resistor, and is configured to detect the voltage or current of the corresponding resistor; The self-test unit is connected to the voltage divider resistor string and is configured to controllably adjust the voltage division ratio of the voltage divider resistor string.

5. The grid-connected / off-grid switching device according to claim 4, characterized in that, The voltage divider resistor string also includes a third resistor and a fourth resistor. The first end of the third resistor is connected to the first polarity node of the power module, the second end of the third resistor is connected to the first end of the second resistor, the first end of the fourth resistor is connected to the second polarity node of the power module, and the second end of the fourth resistor is connected to the second end of the second resistor. The self-test unit includes: The fifth resistor, the first end of which is connected to the first polarity node of the power module; The sixth resistor, the first end of which is connected to the second polarity node of the power module; The third switch, the first end of which is connected to the second end of the fifth resistor, and the second end of the third switch is connected to the first end of the second resistor; The fourth switch has its first end connected to the second end of the sixth resistor, and its second end connected to the second end of the second resistor.

6. The grid-connected / off-grid switching device according to claim 4, characterized in that, The short-circuit detection unit further includes: A DC isolated power supply, wherein the input side of the DC isolated power supply is connected to the output side of the power module, and the output side of the DC isolated power supply is connected to the first terminal node and the first terminal node of the voltage divider resistor string, respectively.

7. The grid-connected / off-grid switching device according to any one of claims 1-6, characterized in that, The power module includes: The anti-backflow circuit has a first input terminal, a second input terminal, a third input terminal, and an output terminal. The first input terminal of the anti-backflow circuit is connected to the external power supply interface. The first AC-DC conversion unit has its AC side connected to the power grid side of the main circuit, and its DC side connected to the second input terminal of the anti-backflow circuit. The second AC-DC converter unit has its AC side connected to the load side of the main circuit and its DC side connected to the third input terminal of the anti-reverse current circuit. The power supply unit has its input side connected to the output terminal of the anti-backflow circuit, and its output side is used to provide electrical energy.

8. The grid-connected / off-grid switching device according to claim 7, characterized in that, The first AC-DC conversion unit includes: An electromagnetic filter unit, wherein a first side of the electromagnetic filter unit is connected to the power grid side of the main circuit; The fifth switch, wherein the first side of the fifth switch is connected to the second side of the electromagnetic filter unit; An AC-DC conversion circuit is provided, wherein the AC side of the AC-DC conversion circuit is connected to the second side of the fifth switch, and the DC side of the AC-DC conversion circuit is connected to the input side of the power supply unit.

9. The grid-connected / off-grid switching device according to claim 8, characterized in that, The fifth switch includes a relay, the switch contacts of which are connected between the AC side of the AC-DC conversion circuit and the second side of the electromagnetic filter unit, and the coil of the relay is connected to the external power supply interface.

10. An electric power system, characterized in that, The power system includes a grid-connected / off-grid switching device according to any one of claims 1-9.

11. The power system according to claim 10, characterized in that, The power system also includes a photovoltaic energy storage system and a distribution box. The distribution box is equipped with an in-home power distribution unit, an electrical instrument panel, and a meter. The in-home power distribution unit is connected to the load side of the photovoltaic energy storage system and the electrical instrument panel, respectively. The load side of the grid-connected / off-grid switching device is connected to the load side of the electrical instrument panel. The grid side of the grid-connected / off-grid switching device is connected to the first terminal of the meter, and the second terminal of the meter is connected to the grid terminal of the electrical instrument panel.

12. The power system according to claim 11, characterized in that, The photovoltaic-energy storage system includes multiple photovoltaic modules and an inverter-energy storage unit, which is connected to the household power distribution unit and the grid-connected / off-grid switching device, respectively. Each of the photovoltaic modules is connected to the input side of the inverter-energy storage unit; or, Some of the photovoltaic modules are connected to the input side of the inverter-energy storage unit, while some of the photovoltaic modules are connected to the household power distribution unit through an independent inverter.

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