A hybrid optical storage inverter with pid effect repair

Abstract

The utility model discloses a kind of light storage hybrid inverter with PID effect repair, belong to inverter technical field. Including: at least one component boost circuit, at least one group photovoltaic interface, DC / AC inverter bridge arm and output interface;The component boost circuit is between DC / AC inverter bridge arm and photovoltaic interface, including inductance, first capacitor, first switch tube, second switch tube and unidirectional conducting device;Each group photovoltaic interface includes positive photovoltaic interface and negative photovoltaic interface, and photovoltaic interface is used to be connected with external photovoltaic array.The utility model is through the design component boost circuit, by increasing second switch tube and unidirectional conducting device, the PID repair of light storage hybrid inverter is realized, suitable for single machine and parallel operation light storage hybrid inverter, and TN-S / TN-C-S / TT three-phase four-wire power grid.

Description

Technical Field

[0001] This utility model relates to the field of inverter technology, and in particular to a photovoltaic-storage hybrid inverter with PID effect repair. Background Technology

[0002] Potential-Induced Degradation (PID) in photovoltaic (PV) modules refers to the phenomenon where a high-intensity negative voltage is applied between the solar cells and the frame (ground) of a PV module, causing a continuous degradation in the module's performance. Severe PID can lead to a power reduction of over 50% in the module, thus affecting the power output of the entire battery string.

[0003] Existing solutions to the PID effect in photovoltaic systems include: (1) The AC side virtual neutral point raising scheme is adopted. The AC side virtual neutral point to ground potential is raised by adding an external DC source, thereby raising the bus center point to ground potential and indirectly raising the component negative electrode to ground potential.

[0004] (2) When there is no power grid and only the battery is running, an additional PID repair module is added to the DC side.

[0005] (3) Change the PV boost topology from the traditional direct connection between PV- and BUS- to a direct connection between PV+ and BUS+.

[0006] The above technical solutions have the following drawbacks: Solution 1 is only suitable for isolated three-phase three-wire power grids, not three-phase four-wire power grids. Specifically, when the inverter stops working at night, the internal relays of the inverter disconnect, and the rise of the virtual neutral point on the AC side cannot change the midpoint potential of the DC input bus, thus failing to achieve PID compensation and repair for the components. Combining Solution 1 and Solution 2 can be used for three-phase four-wire power grids, but adding a PID repair module on the DC side increases product size, weight, and cost. Solution 3, with its direct connection topology between PV+ and BUS+, requires extensive adjustments to both software and hardware designs. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention designs a boost circuit structure, resulting in a circuit with PID repair function, suitable for stand-alone and parallel photovoltaic-storage hybrid inverters, as well as TN-S / TN-CS / TT three-phase four-wire power grids.

[0008] To achieve the above objectives, this utility model provides a photovoltaic-storage hybrid inverter with PID effect repair, comprising: at least one component boost circuit, at least one set of photovoltaic interfaces, a DC / AC inverter bridge arm, and an output interface; the component boost circuit is located between the DC / AC inverter bridge arm and the photovoltaic interfaces, and includes an inductor L1, a first capacitor C1, a first switch S1, a second switch S2, and a unidirectional conducting device D1; each set of photovoltaic interfaces includes a positive photovoltaic interface and a negative photovoltaic interface, and the photovoltaic interface is used to connect to an external photovoltaic array; The DC terminals of the DC / AC inverter bridge arms are connected to the positive and negative DC buses respectively, and the AC terminals of the DC / AC inverter bridge arms are connected to the output interface. The first capacitor C1 is connected between the positive photovoltaic interface and the negative photovoltaic interface; the positive photovoltaic interface is connected to the emitter of the second switching transistor S2 through the inductor L1, and the collector of the second switching transistor S2 is connected to the positive DC bus; the common point of the inductor L1 and the second switching transistor S2 is connected to the collector of the first switching transistor S1; the negative photovoltaic interface is connected to the cathode of the unidirectional conducting device D1, and the anode of the unidirectional conducting device D1 is connected to the negative DC bus and the emitter of the first switching transistor S1.

[0009] Furthermore, it also includes a DC / DC converter connected between the positive and negative DC buses and the energy storage battery.

[0010] Furthermore, a switch K4 is also connected between the DC / DC converter and the positive DC bus.

[0011] Furthermore, it also includes grid connection switch K1, load switch K2 and grounding switch K3; One end of the grid-connected switch K1 is connected to the AC terminal of the DC / AC inverter bridge arm, and the other end of the grid-connected switch is connected to the AC power grid. One end of the load switch K2 is connected to the AC terminal of the DC / AC inverter bridge arm, and the other end of the load switch is connected to the load. One end of the grounding switch K3 is connected to the neutral line of the DC / AC inverter bridge arm, and the other end of the grounding switch is grounded.

[0012] Furthermore, the neutral line of the DC / AC inverter bridge arm is led out from the midpoint of the DC bus; Alternatively, the neutral line of the DC / AC inverter bridge arm is drawn out from the midpoint formed by the star connection of the AC output phase lines of the DC / AC inverter bridge arm; Alternatively, the neutral line of the DC / AC inverter bridge arm is drawn from the midpoint of one of the bridge arms.

[0013] Furthermore, the neutral line of the DC / AC inverter bridge arm is connected to the ground or an equipotential body of the ground via a switch.

[0014] Furthermore, the AC power grid is a system with a neutral point grounded.

[0015] Furthermore, the first switch S1 and the second switch S2 are IGBTs or MOSFETs.

[0016] The beneficial effects of this utility model are: 1. Based on the existing component boost circuit topology, this utility model can achieve PID repair of the photovoltaic-storage hybrid inverter by simply adding S2 and D1, thus without changing the traditional hardware and software control, making it simple to implement.

[0017] 2. This utility model is applicable to single-unit and parallel photovoltaic-storage hybrid inverters, as well as TN-S / TN-CS / TT three-phase four-wire power grids.

[0018] 3. This utility model does not require additional module costs, so it has little impact on product size, weight, and cost. Attached Figure Description

[0019] Figure 1 This is a circuit diagram of a photovoltaic-storage hybrid inverter with PID effect repair according to an embodiment of the present invention.

[0020] Figure 2 This is a circuit diagram of a parallel photovoltaic-storage hybrid inverter with PID effect repair according to an embodiment of the present invention. Detailed Implementation

[0021] The present invention will be further explained and described below with reference to the accompanying drawings and embodiments.

[0022] like Figure 1 As shown, this utility model provides a photovoltaic-storage hybrid inverter with PID effect repair, which is applied to a photovoltaic-storage hybrid system, including: at least one component boost circuit, at least one set of photovoltaic interfaces, DC / AC inverter bridge arms, energy storage interfaces and output interfaces.

[0023] In this embodiment of the invention, a photovoltaic-storage hybrid inverter including a set of photovoltaic interfaces is used as an example. Each set of photovoltaic interfaces includes a positive photovoltaic interface and a negative photovoltaic interface, and the photovoltaic interfaces are used to connect to an external photovoltaic array; the positive photovoltaic interface is used to connect to the positive electrode PV+ of the photovoltaic array, and the negative photovoltaic interface is used to connect to the negative electrode PV+ of the photovoltaic array. connect.

[0024] The component boost circuit is arranged between the DC / AC inverter bridge arm and the photovoltaic interface, including an inductor L1, a first capacitor C1, a first switching tube S1, a second switching tube S2 and a unidirectional conduction device D1 (diode). Compared with the traditional component boost circuit, the PID repair function is realized by adding the second switching tube S2 and the unidirectional conduction device D1.

[0025] The DC / AC inverter bridge arm is used to convert direct current into alternating current, and includes a DC terminal and an AC terminal, wherein the DC terminal is respectively connected to the positive and negative DC buses, and the AC terminal is connected to the output interface. The first capacitor C1 is connected between the positive photovoltaic interface and the negative photovoltaic interface; the positive photovoltaic interface is connected to the emitter of the second switching tube S2 through the inductor L1, and the collector of the second switching tube S2 is connected to the positive DC bus; the common point of the inductor L1 and the second switching tube S1 is connected to the collector of the first switching tube S1; the negative photovoltaic interface is connected to the cathode of the unidirectional conduction device D1, and the anode of the unidirectional conduction device D1 is connected to the negative DC bus and the emitter of the first switching tube S1. The first switching tube S1 and the second switching tube S2 are bidirectional conduction semiconductors, such as IGBTs or MOSFETs.

[0026] The photovoltaic-energy storage hybrid inverter further includes a DC / DC converter, the DC / DC converter is connected between the positive and negative DC buses and the energy storage battery, and a switch K4 is further connected between the DC / DC converter and the positive DC bus.

[0027] The photovoltaic-energy storage hybrid inverter further includes a control unit, which is connected to the bases of the first switching tube S1 and the second switching tube S2, and is used for controlling the closing and opening of the first switching tube S1 and the second switching tube S2.

[0028] The working principle of the photovoltaic-energy storage hybrid inverter is as follows: When it is detected that the BAT battery is connected, the switch K4 is closed, so that the bus voltage BUS+ is in a high voltage state regardless of the presence or absence of PV voltage.

[0029] If the photovoltaic-energy storage hybrid inverter is at night and the photovoltaic array stops working, the first switching tube S1 is opened, and then the second switching tube S2 is closed, so that the potential of BUS+ = PV+ = PV-, thereby starting PID repair. The principle of PID repair is that since the potential of BUS- < PE < BUS+, when the potential of BUS+ = PV+ = PV-, it is inevitable that PV+ = PV- > the potential of PE, so that the component is in the PID repair state.

[0030] If the photovoltaic array meets the working conditions, the second switching tube S2 is opened, and then the first switching tube S1 is closed to perform PWM pulse width modulation, thereby entering a normal working state.

[0031] The component boost circuit is also applicable to parallel-connected photovoltaic-energy storage hybrid inverters, such as Figure 2As shown, it also includes a grid connection switch, a load switch, and a grounding switch.

[0032] One end of the grid-connected switch is connected to the AC terminal of the DC / AC inverter bridge arm, and the other end of the grid-connected switch is connected to the AC power grid.

[0033] One end of the load switch is connected to the AC terminal of the DC / AC inverter bridge arm, and the other end of the load switch is connected to the load.

[0034] One end of the grounding switch is connected to the neutral line of the DC / AC inverter bridge arm, and the other end of the grounding switch is grounded.

[0035] In this embodiment of the present invention, K1 includes at least four switches, with L1, L2, L3, and N each connected to one switch. In practical applications, for safety reasons, each phase of L1, L2, L3, and N should be composed of two or more switches connected in series. This invention does not limit this.

[0036] When the inverter is running in grid-connected mode, the controller controls K1 and K2 to close. The equivalent circuit diagram at this time is... Figure 1 The inverter topology shown will not be described in detail here.

[0037] When the inverter is off-grid, the controller disconnects K1 and simultaneously closes K2 and K3. After K2 is closed, the electrical energy output from the energy storage battery is converted into AC power by the DC / AC inverter bridge arm and supplied to the load.

[0038] In this embodiment, the neutral line of the DC / AC inverter bridge arm is directly connected to the midpoint of the DC bus. Therefore, after K3 is closed, the neutral line of the DC / AC inverter bridge arm is grounded, which means that the midpoint of the DC bus of the inverter is grounded, and the potential of the midpoint of the DC bus is always equal to that of the ground.

[0039] The neutral line of a DC / AC inverter bridge arm can also be drawn from the midpoint of the AC output phase line of the DC / AC inverter bridge arm through a star connection of the first capacitor; or, the neutral line can be drawn from the midpoint of one of the bridge arms of the DC / AC inverter bridge arm. For example, the neutral line of the DC / AC inverter bridge arm can be drawn from the midpoint of the N-arm of a single-phase inverter with a two-arm topology or a three-phase inverter with a four-arm topology.

[0040] In both methods described above, the midpoint of the DC bus is not directly connected to the neutral line. Therefore, the real-time potential of the midpoint of the DC bus is not necessarily exactly equal to the ground potential. However, since the average voltage to ground of the midpoint of the DC side of the inverter (i.e., the midpoint of the DC bus) and the average voltage to ground of the neutral line led out from the inverter always remain approximately equal, and since the neutral line is grounded through the power grid, meaning the potential of the neutral line is equal to the ground potential (0V), the voltage to ground of the midpoint of the DC side is also 0V. Therefore, both methods achieve the same effect of closing K3 to make the average potential of the midpoint of the DC bus the same as the ground potential.

[0041] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A photovoltaic-storage hybrid inverter with PID effect repair, characterized in that, include: The system includes at least one component boost circuit, at least one set of photovoltaic interfaces, a DC / AC inverter bridge arm, and an output interface; the component boost circuit is located between the DC / AC inverter bridge arm and the photovoltaic interfaces, and includes an inductor L1, a first capacitor C1, a first switch S1, a second switch S2, and a unidirectional conducting device D1; each set of photovoltaic interfaces includes a positive photovoltaic interface and a negative photovoltaic interface, and the photovoltaic interface is used to connect to an external photovoltaic array; The DC terminals of the DC / AC inverter bridge arms are connected to the positive and negative DC buses respectively, and the AC terminals of the DC / AC inverter bridge arms are connected to the output interface. The first capacitor C1 is connected between the positive photovoltaic interface and the negative photovoltaic interface; the positive photovoltaic interface is connected to the emitter of the second switching transistor S2 through the inductor L1, and the collector of the second switching transistor S2 is connected to the positive DC bus; the common point of the inductor L1 and the second switching transistor S2 is connected to the collector of the first switching transistor S1; the negative photovoltaic interface is connected to the cathode of the unidirectional conducting device D1, and the anode of the unidirectional conducting device D1 is connected to the negative DC bus and the emitter of the first switching transistor S1.

2. The photovoltaic-storage hybrid inverter with PID effect repair according to claim 1, characterized in that: It also includes a DC / DC converter connected between the positive and negative DC buses and the energy storage battery.

3. The photovoltaic-storage hybrid inverter with PID effect repair according to claim 2, characterized in that: A switch K4 is also connected between the DC / DC converter and the positive DC bus.

4. The photovoltaic-storage hybrid inverter with PID effect repair according to claim 1, characterized in that: It also includes grid connection switch K1, load switch K2 and grounding switch K3; One end of the grid-connected switch K1 is connected to the AC terminal of the DC / AC inverter bridge arm, and the other end of the grid-connected switch is connected to the AC power grid. One end of the load switch K2 is connected to the AC terminal of the DC / AC inverter bridge arm, and the other end of the load switch is connected to the load. One end of the grounding switch K3 is connected to the neutral line of the DC / AC inverter bridge arm, and the other end of the grounding switch is grounded.

5. The photovoltaic-storage hybrid inverter with PID effect repair according to claim 4, characterized in that: The neutral line of the DC / AC inverter bridge arm is drawn out from the midpoint of the DC bus; Alternatively, the neutral line of the DC / AC inverter bridge arm is drawn out from the midpoint formed by the star connection of the AC output phase lines of the DC / AC inverter bridge arm; Alternatively, the neutral line of the DC / AC inverter bridge arm is drawn from the midpoint of one of the bridge arms.

6. The photovoltaic-storage hybrid inverter with PID effect repair according to claim 5, characterized in that: The neutral line of the DC / AC inverter bridge arm is connected to the ground or an equipotential body of the ground via a switch.

7. The photovoltaic-storage hybrid inverter with PID effect repair according to claim 4, characterized in that: The AC power grid is a system with a neutral point grounded.

8. The photovoltaic-storage hybrid inverter with PID effect repair according to claim 1, characterized in that: The first switch S1 and the second switch S2 are IGBTs or MOSFETs.

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