Grid-connected and off-grid split-phase inverter topology
By designing and off-grid cracking inverter topology, optimizing the current path and switching action, the problem of low efficiency of traditional circuits when connected to the grid is solved, achieving more efficient inverter system performance and lower losses.
Patent Information
- Application Number
- CN202422414147.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-08
- Publication Date
- 2024-12-20
- Estimated Expiration
- 2034-10-08
AI Technical Summary
Traditional off-grid switching circuits are difficult to cope with different off-grid working conditions, resulting in low power generation efficiency and large switching losses when connected to the grid.
A off-grid cracking inverter topology is designed, including capacitor branch, NPC bridge arm, filter circuit and DC source. Through the high-frequency operation and power frequency operation of the switch, the current path is optimized and the switching loss is reduced. And provide independent 120V output when off-grid.
It improves the power generation efficiency of the inverter system when connected to the grid, reduces switching losses, meets different requirements for off-grid work, and improves the overall performance of the system.
Smart Images
Figure CN222215204U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of power systems, in particular to a grid-connected and off-grid split-phase inverter topology. Background Art
[0002] For single-phase but split-phase output power grids in some areas, such as single-phase 240V (composed of two 120V), when the inverter system is connected to the grid, it only needs to output one 240V, that is, it can transfer energy to the grid. When the inverter system is off-grid, it not only needs to output one 240V, but also needs to output two independent 120V. Because when operating off-grid, household loads need to be powered by the inverter, and there may be 120V loads among the loads.
[0003] The traditional on-grid and off-grid switching circuit is difficult to cope with the different problems of on-grid and off-grid working states, resulting in low power generation efficiency of the inverter system when the inverter system is connected to the grid.
[0004] When the prior art CN115954938A is connected to the grid, the current path passes through many switch tubes and the loss is still relatively large.
[0005] Therefore, it is necessary to design a grid-connected and off-grid split-phase inverter topology to meet the grid-connected and off-grid requirements while improving the efficiency of the inverter system when connected to the grid. Utility Model Content
[0006] The purpose of the utility model is to provide a grid-connected and off-grid split-phase inverter topology to solve the problems raised in the above background technology.
[0007] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: a grid-connected and off-grid split-phase inverter topology, including: a capacitor branch, two NPC type bridge arms, the two NPC type bridge arms are a first NPC type bridge arm and a second NPC type bridge arm, the capacitor branch is composed of a first capacitor and a second capacitor connected in series, the first end, the second end, and the third end of each of the NPC type bridge arms are respectively connected to the midpoint of the capacitor branch, the positive electrode of the first capacitor, and the negative electrode of the second capacitor, and also include a first switch and a second switch, the first switch is bridged between the second end and the midpoint of the first NPC type bridge arm, and the second switch is bridged between the midpoint and the third end of the first NPC type bridge arm.
[0008] Furthermore, two filter circuits are included, wherein the first ends of the two filter circuits are respectively connected to the midpoints of the two NPC-type bridge arms, and the second end of each of the filter circuits is connected to the midpoint of the capacitor branch.
[0009] Furthermore, it also includes a direct current source, wherein the positive and negative ends of the direct current source are connected to the positive electrode of the first capacitor and the negative electrode of the second capacitor respectively.
[0010] Furthermore, the first switch and the second switch are IGBT or MOSFET.
[0011] Furthermore, each NPC type bridge arm includes four switches connected in series.
[0012] Furthermore, the four switches are all MOSFETs or IGBTs.
[0013] Furthermore, two switches among the four switches located in the middle of the NPC type bridge arm are both IGBTs, and two switches at both ends are both MOSFETs; or, two switches among the four switches located in the middle of the NPC type bridge arm are both MOSFETs, and two switches at both ends are both IGBTs.
[0014] Furthermore, two loads are included, each of the filter circuits is an LC filter circuit, and each of the loads is connected in parallel with a capacitor in the LC filter circuit.
[0015] Furthermore, the topology is connected to a single-phase three-wire split-phase power grid.
[0016] Furthermore, the split-phase voltage range of the single-phase three-wire split-phase power grid is 100V-120V.
[0017] Compared with the prior art, the beneficial effects of the utility model are:
[0018] The utility model utilizes the different on-grid and off-grid working states to have different requirements for the inverter output voltage, and designs a switchable circuit topology that meets different on-grid and off-grid working conditions; thereby, while meeting the on-grid and off-grid requirements, the power generation efficiency of the inverter system when the inverter system is on-grid is improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 This is a topological circuit diagram of a grid-connected and off-grid split-phase inverter according to Embodiment 1 of the utility model;
[0020] Figure 2 This is a schematic diagram of an off-grid excitation circuit of Embodiment 4 of the utility model;
[0021] Figure 3 This is a schematic diagram of the off-grid freewheeling circuit of the fourth embodiment of the utility model;
[0022] Figure 4 This is a schematic diagram of the positive half-cycle excitation circuit when connected to the grid in Embodiment 1 of the utility model;
[0023] Figure 5 This is a schematic diagram of a positive half-cycle freewheeling circuit when connected to the grid in Embodiment 1 of the utility model;
[0024] Figure 6This is a schematic diagram of the negative half-cycle excitation circuit when connected to the grid according to the first embodiment of the utility model;
[0025] Figure 7 This is a schematic diagram of a negative half-cycle freewheeling circuit when connected to the grid in Embodiment 1 of the utility model;
[0026] Figure 8 This is a topological circuit diagram of a grid-connected and off-grid split-phase inverter according to Embodiment 2 of the utility model;
[0027] Fig. 9 This is a topological circuit diagram of a grid-connected and off-grid split-phase inverter according to Embodiment 3 of the utility model;
[0028] Fig.10 This is a topological circuit diagram of a grid-connected and off-grid split-phase inverter according to Embodiment 4 of the utility model;
[0029] Fig.11 This is a topological circuit diagram of a grid-connected and off-grid split-phase inverter according to Embodiment 5 of the utility model. DETAILED DESCRIPTION
[0030] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.
[0031] See also Figure 1 A grid-connected and off-grid split-phase inverter topology includes: a capacitor branch, two NPC-type bridge arms, the two NPC-type bridge arms are a first NPC-type bridge arm and a second NPC-type bridge arm, the capacitor branch is formed by a first capacitor C1 and a second capacitor C2 connected in series; a first end P1A of the first NPC-type bridge arm is connected to a midpoint Pc of the capacitor branch, a second end P2A of the first NPC-type bridge arm is connected to a positive electrode of the first capacitor C1, and a third end P3A of the first NPC-type bridge arm is connected to a negative electrode of the second capacitor C2; a first end P1B of the second NPC-type bridge arm is connected to a midpoint Pc of the capacitor branch, a second end P2B of the second NPC-type bridge arm is connected to a positive electrode of the first capacitor C1, and a third end P3B of the second NPC-type bridge arm is connected to a negative electrode of the second capacitor C2; the grid-connected and off-grid split-phase inverter topology also includes a first switch S1 and a second switch S2, the first switch S1 is connected between the second end P2A and the midpoint PA of the first NPC-type bridge arm, and the second switch S2 is connected between the midpoint PA of the first NPC-type bridge arm and its third end P3A.
[0032] Specifically, the first NPC type bridge arm includes a first diode D1A, a second diode D2A, a third switch T1A, a fourth switch T2A, a fifth switch T3A, and a sixth switch T4A; the third switch T1A, the fourth switch T2A, the fifth switch T3A, and the sixth switch T4A are connected in series, the third switch T1A and the fourth switch T2A are connected in series to form a first upper bridge arm, and the fifth switch T3A and the sixth switch T4A are connected in series to form a first lower bridge arm; the first diode D1A and the second diode D2A are connected in series with their two ends connected across the midpoint of the first upper bridge arm and the midpoint of the first lower bridge arm; the first end P1A of the first NPC type bridge arm is the junction point of the first diode D1A and the second diode D2A, the second end P2A of the first NPC type bridge arm is the upper end of the first upper bridge arm, and the third end P3A of the first NPC type bridge arm is the lower end of the first lower bridge arm.
[0033] Specifically, the second NPC type bridge arm includes a third diode D1B, a fourth diode D2B, a seventh switch T1B, an eighth switch T2B, a ninth switch T3B, and a tenth switch T4B; the seventh switch T1B, the eighth switch T2B, the ninth switch T3B, and the tenth switch T4B are connected in series, the seventh switch T1B and the eighth switch T2B are connected in series to form a second upper bridge arm, and the ninth switch T3B and the tenth switch T4B are connected in series to form a second lower bridge arm; the third diode D1B and the fourth diode D2B are connected in series, and both ends are connected across the midpoint of the second upper bridge arm and the midpoint of the second lower bridge arm; the first end P1B of the second NPC type bridge arm is the junction point of the third diode D1B and the fourth diode D2B, the second end P2B of the second NPC type bridge arm is the upper end of the second upper bridge arm, and the third end P3B of the second NPC type bridge arm is the lower end of the second lower bridge arm.
[0034] Figure 1 In the embodiment, the third switch T1A, the fourth switch T2A, the fifth switch T3A, the sixth switch T4A, the seventh switch T1B, the eighth switch T2B, the ninth switch T3B, and the tenth switch T4B are all IGBTs; in another embodiment, the third switch T1A, the fourth switch T2A, the fifth switch T3A, the sixth switch T4A, the seventh switch T1B, the eighth switch T2B, the ninth switch T3B, and the tenth switch T4B are all MOSFETs; in another embodiment, the fourth switch T2A, the fifth switch T3A, the eighth switch T2B, and the ninth switch T3B are all MOSFETs, and the third switch T1A, the sixth switch T4A, the seventh switch T1B, and the tenth switch T4B are all IGBTs; in another embodiment, the fourth switch T2A, the fifth switch T3A, the eighth switch T2B, and the ninth switch T3B are all IGBTs, and the third switch T1A, the sixth switch T4A, the seventh switch T1B, and the tenth switch T4B are all MOSFETs.
[0035] In one embodiment, the grid-connected and off-grid split-phase inverter topology further includes two filter circuits, such as Figure 1 As shown, the filter circuit is an LC filter circuit, and the two filter circuits are the first filter circuit and the second filter circuit. The first filter circuit is formed by the first inductor L1 and the third capacitor C3 connected in series, one end of the first inductor L1 (the first end of the first filter circuit) is connected to the midpoint PB of the second NPC type bridge arm, one end of the third capacitor C3 is connected to the other end of the first inductor L1, and the other end of the third capacitor C3 (the second end of the first filter circuit) is connected to the midpoint Pc of the capacitor branch. The second filter circuit is formed by the second inductor L2 and the fourth capacitor C4 connected in series, one end of the second inductor L2 (the first end of the second filter circuit) is connected to the midpoint PA of the first NPC type bridge arm, one end of the fourth capacitor C4 is connected to the other end of the second inductor L2, and the other end of the fourth capacitor C4 (the second end of the second filter circuit) is connected to the midpoint Pc of the capacitor branch; the common point of the third capacitor C3 and the fourth capacitor C4 is N.
[0036] In one embodiment, the grid-connected and off-grid split-phase inverter topology also includes a DC source DC1, which provides electrical energy to the capacitor branch. The DC source DC1 can be a battery, etc.; the positive end of the DC source DC1 is connected to the positive electrode of the first capacitor C1, and the negative end of the DC source DC1 is connected to the negative electrode of the second capacitor C2. Example
[0037] like Figure 8 As shown, the second embodiment is substantially the same as the first embodiment, except that: the first switch S1 and the second switch S2 are IGBTs, and the C pole and the E pole of the first switch S1 in the figure are respectively connected to the second end P2A of the first NPC type bridge arm and the midpoint PA of the first NPC type bridge arm, and the C pole and the E pole of the second switch S2 are respectively connected to the midpoint PA of the first NPC type bridge arm and the third end P3A of the first NPC type bridge arm. Example
[0038] like Fig. 9 As shown, the third embodiment is substantially the same as the second embodiment, except that: the first switch S1 and the second switch S2 are MOSFETs, and the D pole and the S pole of the first switch S1 in the figure are respectively connected to the second end P2A of the first NPC type bridge arm and the midpoint PA of the first NPC type bridge arm, and the D pole and the S pole of the second switch S2 are respectively connected to the midpoint PA of the first NPC type bridge arm and the third end P3A of the first NPC type bridge arm. Example
[0039] like Fig.10 As shown, the fourth embodiment is substantially the same as the first embodiment, except that the grid-connected and off-grid split-phase inverter topology further includes a first load R1 and a second load R2, the first load R1 is connected in parallel with the third capacitor C3, and the second load R2 is connected in parallel with the fourth capacitor C4. Example
[0040] like Fig.11 As shown, Example 5 is substantially the same as Example 4, the difference being that the grid-connected and off-grid split-phase inverter topology is connected to a single-phase three-wire split-phase power grid (a first power grid Gr1 and a second power grid Gr2), and the split-phase voltage range of the single-phase three-wire split-phase power grid is 100V-120V, that is, the voltage range of the first power grid Gr1 is 100V-120V, and the voltage range of the second power grid Gr2 is 100-120V; for example, the voltage value may be 100V, 102V, 105V, 108V, 112V, 114V, 115V, 118V, 120V, and so on.
[0041] Working principle of this grid-connected and off-grid split-phase inverter topology:
[0042] like Figure 2 , Figure 3 As shown, when off-grid, the first switch S1 and the second switch S2 are normally disconnected and do not participate in the work. The first NPC type bridge arm and the second NPC type bridge arm work alone and can output two independent sine waves to meet the requirements of off-grid split-phase output. The third capacitor C3 and the fourth capacitor C4 can carry loads (first load R1, second load R2) respectively, and the loads (first load R1, second load R2) can be unbalanced.
[0043] in, Figure 2 The green path shows Fig.10 In the excitation circuit when the topology is off-grid, if the loads carried by C3 and C4 are equal, that is, the first load R1 and the second load R2 are equal, then there is no current at all between points N and Pc; if the loads of C3 and C4 are not equal, that is, the first load R1 and the second load R2 are not equal, that is, the split-phase load is unbalanced, there will be an unbalanced current between points N and Pc.
[0044] in, Figure 3 The green path shows Fig.10 The freewheeling circuit when the topology is off-grid is different according to the load conditions, as follows:
[0045] If the loads of C3 and C4 are equal, the freewheeling circuit is R1-L1-T3B-D2B-P1A-D1A-T2A-L2-R2; if the first load R1> the second load R2, and both are not 0, the freewheeling circuit is N-R1-L1-T3B-D2B-P1B-N and R1-L1-T3B-D2B-P1A-D1A-T2A-L2-R2;
[0046] If the second load R2>the first load R1, and both are not 0, the freewheeling circuit is N-P1A-D1A-T2A-L2-R2-N and R1-L1-T3B-D2B-P1A-D1A-T2A-L2-R2.
[0047] When connected to the grid, the first switch S1 / the second switch S2 is in high-frequency operation, and S1 / S2 / T1B / T2B / T3B / T4B participate in the operation (the specific current path is as follows Figure 4-Figure 7 As shown in the green path of ), T1B / T2B, T3B / T4B are in power frequency operation, T1A / T2A / T3A / T4A do not work, the software control logic is simple, there is almost no switching loss, only conduction loss, and the loss is small; the inverter topology output voltage is three-level, and the output ripple is small, which is conducive to the design of the filtering parameters of the subsequent LC (first inductor L1, second inductor L2; third capacitor C3, fourth capacitor C4).
[0048] When connected to the grid, the loss comparison of the specific switch circuit of the utility model topology compared with the prior art CN115954938A is shown in the following table:
[0049]
[0050] It can be seen from the above table that when working in grid connection, no matter in the positive half cycle or the negative half cycle, the current path of the topology of the utility model passes through fewer switch tubes and has lower losses. Therefore, in the entire cycle, the loss of the topology of the utility model is significantly better than that of the prior art CN115954938A.
[0051] Among them, the positive half cycle refers to the positive half cycle of the output voltage of the topology of the utility model, and the negative half cycle refers to the negative half cycle of the output voltage of the topology of the utility model.
[0052] The utility model is aimed at a single-phase power grid with split-phase output (for example, a single-phase 240V is composed of two 120V, etc.), and utilizes the different on-grid and off-grid working states to have different requirements for the inverter output voltage, and designs a switchable circuit topology that meets different on-grid and off-grid working conditions; thereby, while meeting the on-grid and off-grid requirements, the power generation efficiency of the inverter system is improved when the inverter system is on-grid.
[0053] Parts not involved in the present invention are the same as the prior art or can be implemented by the prior art. Although the embodiments of the present invention have been shown and described, it is understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the attached claims and their equivalents.
Claims
1. A grid-connected and off-grid split-phase inverter topology, comprising: A capacitor branch, two NPC type bridge arms, the two NPC type bridge arms are a first NPC type bridge arm and a second NPC type bridge arm, the capacitor branch is formed by connecting a first capacitor and a second capacitor in series, the first end, the second end, and the third end of each of the NPC type bridge arms are respectively connected to the midpoint of the capacitor branch, the positive electrode of the first capacitor, and the negative electrode of the second capacitor, characterized in that it also includes a first switch and a second switch, the first switch is connected between the second end and the midpoint of the first NPC type bridge arm, and the second switch is connected between the midpoint and the third end of the first NPC type bridge arm.
2. The grid-connected and off-grid split-phase inverter topology according to claim 1, characterized in that: It also includes two filter circuits, wherein the first ends of the two filter circuits are respectively connected to the midpoints of the two NPC type bridge arms, and the second end of each of the filter circuits is connected to the midpoint of the capacitor branch.
3. The grid-connected and off-grid split-phase inverter topology according to claim 1, characterized in that: It also includes a direct current source, wherein the positive and negative ends of the direct current source are connected to the positive electrode of the first capacitor and the negative electrode of the second capacitor respectively.
4. The grid-connected and off-grid split-phase inverter topology according to claim 1, characterized in that: The first switch and the second switch are IGBT or MOSFET.
5. The grid-connected and off-grid split-phase inverter topology according to claim 1, characterized in that: Each of the NPC type bridge arms includes four switches connected in series.
6. The grid-connected and off-grid split-phase inverter topology according to claim 5, characterized in that: The four switches are all MOSFETs or IGBTs.
7. The grid-connected and off-grid split-phase inverter topology according to claim 5, characterized in that: The two switches in the middle of the NPC type bridge arm among the four switches are both IGBTs, and the two switches at both ends are both MOSFETs; or, the two switches in the middle of the NPC type bridge arm among the four switches are both MOSFETs, and the two switches at both ends are both IGBTs.
8. The grid-connected and off-grid split-phase inverter topology according to claim 2, characterized in that: It also includes two loads, each of the filter circuits is an LC filter circuit, and each of the loads is connected in parallel with a capacitor in the LC filter circuit.
9. The grid-connected and off-grid split-phase inverter topology according to claim 8, characterized in that: The topology is connected to a single-phase three-wire split-phase power grid.
10. The grid-connected and off-grid split-phase inverter topology according to claim 9, characterized in that: The split-phase voltage range of the single-phase three-wire split-phase power grid is 100V-120V.