Improved auxiliary switch device for photovoltaic inverter and photovoltaic system

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By designing an improved auxiliary switch device in a photovoltaic inverter, the MCU chip is used to determine whether the auxiliary switch is disconnected, which solves the current sinking and overheating problems caused by the auxiliary switch not being disconnected before the grid is connected, and improves the stability and safety of the grid connection.

CN119813341APending Publication Date: 2025-04-11SINENG ELECTRIC CO LTD

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Patent Information

Application Number: CN202411784618.1
Authority / Receiving Office: CN · China
Patent Type: Applications(China)
Current Assignee / Owner
Filing Date: 2024-12-05
Publication Date: 2025-04-11

AI Technical Summary

Technical Problem

When the photovoltaic inverter forgets to disconnect the auxiliary switch before connecting to the grid, it may cause the PV terminal to be reversed or the grid connection process to fail, causing a large current to pour into the PV side, and the auxiliary switch to overheat, posing a major safety hazard.

Method used

An improved auxiliary switch device is designed, including a switching module, a control module, a filter module, a power decoupling module and a conversion module, and a first-level auxiliary switch is added and connected to the control module through a signal line loop. The control module determines whether the auxiliary switch has been disconnected before being connected to the grid through the MCU chip.

Benefits of technology

It effectively prevents the overheating of current into the PV side and auxiliary switch due to reverse connection of PV terminals or faults in the grid connection process, improves the working stability of the grid connection and reduces safety hazards.

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Abstract

The invention is applicable to the technical field of photovoltaic inverters, and provides an improved auxiliary switch device for a photovoltaic inverter, which is applied to a photovoltaic system to control a photovoltaic module string connected with the photovoltaic system, and the photovoltaic module string comprises at least two photovoltaic modules connected in series. The auxiliary switch device comprises a switch module, a control module, a filtering module, a power decoupling module and a conversion module, the switch module is arranged to be a tripping switch, a first auxiliary switch and a second auxiliary switch, and the control module achieves normal grid connection according to the fact that the first auxiliary switch and the second auxiliary switch are in an off state during grid connection. The invention further provides a photovoltaic system, a primary auxiliary switch is added and is connected with the control module through a wiring loop, and the control module judges whether the auxiliary switch is switched off before machine grid connection, so that the potential safety hazards that large current flows into the PV side, the auxiliary switch is overheated and the like due to reverse connection of PV terminals or faults in the machine grid connection process are prevented, and the reliability of the photovoltaic system is improved. And the working stability of grid connection is improved.

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Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaic inverters, and in particular relates to an improved auxiliary switch device for photovoltaic inverters and a photovoltaic system. Background Art

[0002] Inverter, also known as power regulator, is a device used to convert the direct current generated by solar cells into alternating current during the process of solar photovoltaic grid-connected power generation. Photovoltaic inverter not only has the function of direct-to-alternating conversion, but also has the function of maximizing the performance of solar cells and system fault protection. It has the characteristics of automatic operation and shutdown function, maximum power tracking control function, anti-single operation function (for grid-connected system), automatic voltage adjustment function (for grid-connected system), DC detection function (for grid-connected system), and DC grounding detection function (for grid-connected system).

[0003] At present, when the photovoltaic inverter is powered on first with DC power, the auxiliary switch is usually closed first. The auxiliary switch connects one or a few PV strings (photovoltaic component strings) to the MPPT (maximum power point tracking) power conversion circuit. When the machine is connected to DC power through the auxiliary switch, the DC auxiliary source is started to check whether the machine has any faults. If there are no faults, the auxiliary power switch can be disconnected and the machine can be connected to the grid. However, if the machine is checked to have no faults after closing the auxiliary switch, but the auxiliary switch is forgotten to be disconnected before the machine is connected to the grid, when the PV terminals are reversed or a fault occurs during the machine's grid connection process, a large current will be injected into the PV side, causing the auxiliary switch to overheat. The auxiliary switch itself does not have a tripping function, so this solution has a large safety hazard. Summary of the invention

[0004] The present invention provides an improved auxiliary switch device for a photovoltaic inverter and a photovoltaic system, aiming to solve the problem of preventing a large current from being injected into the PV side when a PV terminal is reversely connected or a machine fails during grid connection, and the problem of overheating of the auxiliary switch.

[0005] The present invention is implemented in this way. The present invention provides an improved auxiliary switch device for a photovoltaic inverter, which is applied to a photovoltaic system to control a photovoltaic component string connected thereto, wherein the photovoltaic component string comprises at least two photovoltaic components connected in series, and the auxiliary switch device comprises a switch module, a control module, a filter module, a power decoupling module and a conversion module, wherein the photovoltaic component string, the control module and the filter module are all connected to the switch module, one end of the filter module and the conversion module are all connected to the power decoupling module, and the other end of the conversion module is connected to a power grid;

[0006] The switch module includes at least two trip switches, a first auxiliary switch and a second auxiliary switch, the trip switch is connected to the photovoltaic component, the first auxiliary switch is connected to the control module, one end of the second auxiliary switch is used to connect the positive and negative poles of the photovoltaic component string, and the other end of the second auxiliary switch is connected to the first auxiliary switch and the filter module, wherein the control module is in a disconnected state according to the first auxiliary switch and the second auxiliary switch when connected to the grid to achieve normal grid connection.

[0007] Furthermore, the improved auxiliary switch device for a photovoltaic inverter further includes a capacitor, which is connected in parallel between the power decoupling module and the conversion module.

[0008] Furthermore, the conversion module includes a DCAC conversion circuit.

[0009] Furthermore, the power decoupling module includes at least two MPPT units, and the MPPT units are used to detect the power generation voltage of the photovoltaic component in real time and track the maximum voltage and current value so that the photovoltaic system outputs maximum power.

[0010] Furthermore, the filtering module includes a DC EMI filtering circuit.

[0011] Furthermore, the number of the first auxiliary switches is less than the number of the second auxiliary switches.

[0012] Furthermore, the first auxiliary switch is connected to the control module through a signal line loop.

[0013] Furthermore, the control module includes an MCU chip, and the MCU chip is used to detect the on or off status of the first auxiliary switch and the second auxiliary switch when they are connected to the grid.

[0014] The present invention also provides a photovoltaic system, which includes at least one of the above-mentioned improved auxiliary switch devices for photovoltaic inverters, at least one photovoltaic component string corresponding to the improved auxiliary switch device for photovoltaic inverters, and a photovoltaic inverter, the input end of the improved auxiliary switch device for photovoltaic inverters is connected to the photovoltaic component string, the output end of the improved auxiliary switch device for photovoltaic inverters is connected to the input end of the photovoltaic inverter, and the improved auxiliary switch device for photovoltaic inverters controls the opening or closing of the photovoltaic component string to achieve grid connection.

[0015] The present invention provides an improved auxiliary switch device for a photovoltaic inverter and a photovoltaic system. The improved auxiliary switch device for a photovoltaic inverter comprises a switch module, a control module, a filter module, a power decoupling module and a conversion module. The switch module is configured as a trip switch, a first auxiliary switch and a second auxiliary switch. The control module adds a first-level auxiliary switch and connects it to the control module through a wiring loop according to the first auxiliary switch and the second auxiliary switch being in a disconnected state when connected to the grid to achieve normal grid connection. The control module determines whether the auxiliary switch has been disconnected before the machine is connected to the grid, so as to prevent safety hazards such as a large current being injected into the PV side and overheating of the auxiliary switch caused by reverse connection of the PV terminal or failure of the machine in the grid connection process, thereby improving the working stability of the grid connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a circuit diagram of a photovoltaic inverter connected to the grid provided by the prior art;

[0017] Figure 2 It is a structural block diagram of an improved auxiliary switch device for a photovoltaic inverter provided by the present invention;

[0018] Figure 3 The invention provides a circuit diagram of an improved auxiliary switch device for a photovoltaic inverter.

[0019] The main component symbols are as follows:

[0020] 100 - photovoltaic component string; 110 - switch module; 120 - control module; 130 - filter module; 140 - power decoupling module; 150 - conversion module; 160 - trip switch; 170 - first auxiliary switch; 180 - second auxiliary switch; 190 - capacitor. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] The auxiliary switch in the embodiment of the present invention is increased in one stage, and is connected to the main control chip MCU through a signal line loop. The MCU determines whether the auxiliary switch has been disconnected when connected to the grid, thereby ensuring normal grid-connected operation.

[0023] See also Figure 1 , Figure 2 and Figure 3The present invention provides an improved auxiliary switch device for a photovoltaic inverter, which is applied to a photovoltaic system to control a photovoltaic component string connected thereto, wherein the photovoltaic component string 100 comprises at least two photovoltaic components connected in series, and the auxiliary switch device comprises a switch module 110, a control module 120, a filter module 130, a power decoupling module 140 and a conversion module 150, wherein the photovoltaic component string 100, the control module 120 and the filter module 130 are all connected to the switch module 110, one end of the filter module 130 and the conversion module 150 are both connected to the power decoupling module 140, and the other end of the conversion module 150 is connected to a power grid;

[0024] The switch module 110 includes at least two trip switches 160, a first auxiliary switch 170 and a second auxiliary switch 180, wherein the trip switch 160 is connected to the photovoltaic component, the first auxiliary switch 170 is connected to the control module 120, one end of the second auxiliary switch 180 is used to connect the positive and negative poles of the photovoltaic component string 100, and the other end of the second auxiliary switch 180 is connected to the first auxiliary switch 170 and the filter module 130, wherein the control module 120 is in a disconnected state according to the first auxiliary switch 170 and the second auxiliary switch 180 when connected to the grid to achieve normal grid connection.

[0025] In this embodiment, the improved auxiliary switch device for the photovoltaic inverter also includes a capacitor 190, and the capacitor 190 is connected in parallel between the power decoupling module 140 and the conversion module 150. The conversion module 150 includes a DCAC conversion circuit. The power decoupling module 140 includes at least two MPPT units. The MPPT unit is used to detect the power generation voltage of the photovoltaic component in real time and track the highest voltage and current values so that the photovoltaic system can output maximum power.

[0026] As described above, the filtering module 130 includes a DC EMI filtering circuit, the number of the first auxiliary switches 170 is less than the number of the second auxiliary switches 180, the first auxiliary switches 170 are connected to the control module 120 through a signal line loop, and the control module 120 includes an MCU chip, and the MCU chip is used to detect the on or off state of the first auxiliary switch 170 and the second auxiliary switch 180 when connected to the grid, wherein the on or off state includes open and closed.

[0027] In the above, PV1+ represents the positive electrode of the first photovoltaic module PV, PV1- represents the negative electrode of the first photovoltaic module PV, the power decoupling module 140 includes MPPT1-MPPTn, and the maximum power point tracking (MPPT) is an electrical system that adjusts the working state of the electrical module so that the photovoltaic panel can output more electrical energy. It can effectively store the direct current generated by the solar panel in the battery, which can effectively solve the living and industrial electricity consumption in remote areas and tourist areas that are not covered by conventional power grids without causing environmental pollution.

[0028] It should be noted that if Figure 1 As shown, the strings PV1~PVn are connected to the DC EMI filter board through the tripping DC switch, and are sent to the inverter part through the MPPT power part after filtering. The auxiliary switch is connected by connecting one or less PV strings to realize the fault inspection of the machine before grid connection. If there is no fault, the auxiliary switch can be disconnected for grid connection. The control module 120 in this embodiment can be a microprocessor MCU, and multiple photovoltaic modules are connected in series to form a photovoltaic module string 100. The lever and spring mechanism in the tripping switch 160 are supported by the tripping device. Once the tripping device is activated, the lever and spring mechanism in the switch will reset freely, that is, the switch trips.

[0029] As mentioned above, a DC EMI filter circuit composed of multiple DC EMI filters is arranged on the filter board. The functions of the DC EMI filter include: using an EMI filter in the power supply line can effectively reduce the impact of electromagnetic interference on electronic equipment and improve quality and stability; effectively protect the equipment from damage by electromagnetic interference, reduce the probability of equipment failure, and make the equipment have a longer life and more stable use; suppress the propagation of electromagnetic interference signals, ensure the normal operation of the equipment or system, and improve the anti-interference ability of the system.

[0030] As mentioned above, the capacitor 190 is located between the power decoupling module 140 and the conversion module 150, which can smooth the signal in the circuit to reduce noise to a certain extent, and can also collect charges and transfer the stored energy to the output end. The DCAC conversion circuit converts DC voltage or current into AC voltage or current. In other words, the auxiliary switch is increased by one level, and the signal line loop is connected to the main control chip MCU. The MCU determines whether the auxiliary switch has been disconnected when connected to the grid. If it is determined that the auxiliary switch is not disconnected, normal grid connection cannot be achieved, and the relevant personnel are informed that the auxiliary switch needs to be disconnected to connect to the grid. Among them, the first auxiliary switch 170 and the second auxiliary switch 180 constitute the auxiliary switch.

[0031] The present invention also provides a photovoltaic system comprising at least one of the above-mentioned improved auxiliary switch devices for photovoltaic inverters, at least one photovoltaic component string 100 corresponding to the improved auxiliary switch device for photovoltaic inverters, and a photovoltaic inverter (not shown), wherein the input end of the improved auxiliary switch device for photovoltaic inverters is connected to the photovoltaic component string 100, the output end of the improved auxiliary switch device for photovoltaic inverters is connected to the input end of the photovoltaic inverter, and the improved auxiliary switch device for photovoltaic inverters controls the opening or closing of the photovoltaic component string 100 to achieve grid connection.

[0032] In this embodiment, each switch in the trip switch 160 can be recorded as k1-kn, and each switch in the auxiliary switch can be recorded as Q1-Q3, that is, the first auxiliary switch 170 is recorded as Q1, and the second auxiliary switch 180 is recorded as Q2, Q3. The switches k1-kn are connected to the positive terminals of the corresponding photovoltaic components PV1-PVn, wherein the switch k1 is connected between the positive terminal of the corresponding photovoltaic component PV1 and the negative terminal of the photovoltaic component PV2, the switch k2 is connected between the positive terminal of the corresponding photovoltaic component PV2 and the negative terminal of the photovoltaic component PV3, and the switch kn is connected between the positive terminal of the corresponding photovoltaic component PVn and the positive terminal of the photovoltaic component string 100. The switch Q1 is connected to the MCU through a signal line loop, one end of the switch Q2 is connected to the positive terminal of the photovoltaic component PVn, the other end of the switch Q2 is connected to the DC EMI filter circuit, one end of the switch Q3 is connected to the negative terminal of the photovoltaic component PVn, and the other end of the switch Q3 is connected to the DC EMI filter circuit. In normal operation, when switches k1-kn are turned on, i.e., switches Q1-Q3 are turned on, each photovoltaic module of the photovoltaic module string 100 outputs electric energy. When an emergency occurs, when the MCU chip issues a shutdown command, all switches are turned off, and each photovoltaic module is open circuited to each other. At this time, the output voltage is 0. In other words, the auxiliary switches Q1-Q3 are checked for faults before being connected to the grid. If there is no fault, the auxiliary switches can be disconnected for grid connection. When the MCU chip determines whether the auxiliary switches Q1-Q3 have been disconnected when connected to the grid, if there is no fault, the auxiliary switches Q1-Q3 can be disconnected for grid connection.

[0033] It should be understood that the improved auxiliary switch device for the photovoltaic inverter includes a switch module 110, a control module 120, a filter module 130, a power decoupling module 140 and a conversion module 150. The switch module 110 is configured as a trip switch 160, a first auxiliary switch 170 and a second auxiliary switch 180. The control module 120 adds a first-level auxiliary switch and connects it to the control module through a wiring loop according to the first auxiliary switch 170 and the second auxiliary switch 180 being in a disconnected state when connected to the grid to achieve normal grid connection. The control module 120 determines whether the auxiliary switch has been disconnected before the machine is connected to the grid to prevent safety hazards such as a large current being injected into the PV side and overheating of the auxiliary switch caused by reverse connection of the PV terminal or failure of the machine during the grid connection process, thereby improving the working stability of the grid connection.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An improved auxiliary switch device for a photovoltaic inverter, used in a photovoltaic system to control a photovoltaic component string connected thereto, wherein the photovoltaic component string comprises at least two photovoltaic components connected in series, characterized in that: The improved auxiliary switch device for photovoltaic inverter comprises a switch module, a control module, a filter module, a power decoupling module and a conversion module. The photovoltaic component string, the control module and the filter module are all connected to the switch module. One end of the filter module and the conversion module are both connected to the power decoupling module. The other end of the conversion module is connected to the power grid. The switch module includes at least two trip switches, a first auxiliary switch and a second auxiliary switch, the trip switch is connected to the photovoltaic component, the first auxiliary switch is connected to the control module, one end of the second auxiliary switch is used to connect the positive and negative poles of the photovoltaic component string, and the other end of the second auxiliary switch is connected to the first auxiliary switch and the filter module, wherein the control module is in a disconnected state according to the first auxiliary switch and the second auxiliary switch when connected to the grid to achieve normal grid connection.

2. The improved auxiliary switch device for photovoltaic inverter according to claim 1, characterized in that: The improved auxiliary switch device for a photovoltaic inverter further includes a capacitor, which is connected in parallel between the power decoupling module and the conversion module.

3. The improved auxiliary switch device for photovoltaic inverter according to claim 2, characterized in that: The conversion module includes a DCAC conversion circuit.

4. The improved auxiliary switch device for photovoltaic inverter according to claim 2, characterized in that: The power decoupling module includes at least two MPPT units, and the MPPT units are used to detect the power generation voltage of the photovoltaic component in real time and track the highest voltage and current values so that the photovoltaic system can output maximum power.

5. The improved auxiliary switch device for photovoltaic inverter according to claim 1, characterized in that: The filtering module includes a DC EMI filtering circuit.

6. The improved auxiliary switch device for photovoltaic inverter according to claim 1, characterized in that: The number of the first auxiliary switches is smaller than the number of the second auxiliary switches.

7. The improved auxiliary switch device for photovoltaic inverter according to claim 6, characterized in that: The first auxiliary switch is connected to the control module through a signal line loop.

8. The improved auxiliary switch device for photovoltaic inverter according to claim 7, characterized in that: The control module includes an MCU chip, and the MCU chip is used to detect the on or off status of the first auxiliary switch and the second auxiliary switch when they are connected to the grid.

9. A photovoltaic system, characterized in that: The photovoltaic system comprises at least one improved auxiliary switch device for a photovoltaic inverter as described in any one of claims 1 to 8, at least one photovoltaic component string corresponding to the improved auxiliary switch device for the photovoltaic inverter and a photovoltaic inverter, the input end of the improved auxiliary switch device for the photovoltaic inverter is connected to the photovoltaic component string, the improved auxiliary switch device for the photovoltaic inverter is connected to the input end of the photovoltaic inverter, and the improved auxiliary switch device for the photovoltaic inverter controls the opening or closing of the photovoltaic component string to achieve grid connection.