CHB-based photovoltaic inverter control system

Abstract

The utility model relates to the technical field of photovoltaic power generation, and particularly discloses a CHB-based photovoltaic inverter control system, which comprises a PV module and a grid-connected inverter system which are electrically connected. The grid-connected inverter system comprises a non-isolated DC / DC module, an isolated DCDC module and a cascaded H-bridge module which are electrically connected. The number of the non-isolated DC / DC modules and the number of the isolated DCDC modules correspond to the number of the PV modules. The isolation DCDC module is a one-way circuit topology; the cascaded H-bridge module is a bidirectional topology and comprises a plurality of subunits, and the number of the subunits is the sum of output branches of the isolation DCDC module; each subunit is respectively connected with each output branch of the isolation DCDC module; the cascading form comprises multi-level cascading and common null line cascading. By adopting the technical scheme of the utility model, the problem of current leakage can be effectively solved, and the efficiency is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of photovoltaic power generation, in particular to a photovoltaic inverter control system based on CHB. Background Art

[0002] Most of the existing photovoltaic inverters are non-isolated topologies, among which the inverters use other topologies with common-mode current suppression capabilities such as H5 and H6, which effectively reduce the leakage current of the inverter but reduce the efficiency of the inverter.

[0003] Therefore, a photovoltaic inverter control system based on CHB is needed that can effectively solve the leakage current problem and improve efficiency.

[0004] Therefore, the topology based on PV with isolation transformer plus cascaded H-bridge can effectively solve the above problems. Utility Model Content

[0005] The utility model provides a photovoltaic inverter control system based on CHB, which can effectively solve the leakage current problem and improve efficiency.

[0006] In order to solve the above technical problems, this application provides the following technical solutions:

[0007] A photovoltaic inverter control system based on CHB includes electrically connected PV modules and a grid-connected inverter system; the grid-connected inverter system includes electrically connected non-isolated DC / DC modules, isolated DC / DC modules, and cascaded H-bridge modules;

[0008] The PV module has several paths. The number of non-isolated DC / DC modules and isolated DCDC modules corresponds to the number of PV modules. The isolated DCDC module has a unidirectional circuit topology.

[0009] The cascaded H-bridge module is a bidirectional topology, including several sub-units, the number of which is the sum of the output branches of the isolated DCDC module; each sub-unit is respectively connected to each output branch of the isolated DCDC module; the cascade form includes multi-level cascade and common neutral line cascade.

[0010] Furthermore, the non-isolated DC / DC module includes two Boost circuit outputs connected in parallel;

[0011] The isolated DCDC module includes an electrically connected primary bridge arm, a step-down transformer, and a secondary bridge arm; the secondary bridge arm includes two independent diode rectifier bridges;

[0012] The cascaded H-bridge module includes a first subunit, a second subunit and an AC filter;

[0013] The two boost circuit outputs are connected to the primary bridge arm; the two diode rectifier bridge outputs are connected to the first subunit and the second subunit of the cascaded H-bridge module respectively;

[0014] The first subunit and the second subunit are connected to an AC filter, and the AC filter is also connected to an external AC power grid.

[0015] Furthermore, the first Boost circuit of the non-isolated DC / DC module includes an input capacitor C1, an energy storage inductor L1, a switch tube Q1 and a diode D1;

[0016] One end of the input capacitor C1 is connected to the PV1+ terminal, and the other end of the input capacitor C1 is connected to the PV1- terminal;

[0017] One end of the energy storage inductor L1 is connected to one end of the input capacitor C1, and the other end of the energy storage inductor L1 is connected to the positive electrode of the diode D1;

[0018] The D pole of the switch tube Q1 is connected to the other end of the energy storage inductor L1, and the S pole of the switch tube Q1 is connected to the other end of the input capacitor C1;

[0019] The second Boost circuit includes input capacitor C2, energy storage inductor L2, switch tube Q2 and diode D2;

[0020] One end of the input capacitor C2 is connected to the PV2+ terminal, and the other end of the input capacitor C2 is connected to the PV2- terminal;

[0021] One end of the energy storage inductor L2 is connected to one end of the input capacitor C2, and the other end of the energy storage inductor L2 is connected to the positive electrode of the diode D2;

[0022] The D-pole of the switch tube Q2 is connected to the other end of the energy storage inductor L2, and the S-pole of the switch tube Q2 is connected to the other end of the input capacitor C2;

[0023] PV1+ and PV2+ are both connected to the positive pole of the PV module; PV1- and PV2- are both connected to the negative pole of the PV module;

[0024] The primary bridge arm of the isolated DCDC module includes switching devices Q3 and Q4, input capacitors C3, C4, C5, and resonant inductor Lr.

[0025] The secondary bridge arm includes two independent diode rectifier bridges, one diode rectifier bridge includes diode D3, diode D4, diode D5, and diode D6, and the other diode rectifier bridge includes diode D7, diode D8, diode D9, and diode D10;

[0026] The step-down transformer includes a primary winding N1 and secondary windings N2 and N3;

[0027] The cathode of diode D1 and diode D2 are both connected to one end of input capacitor C3, and the S pole of switch tube Q1 and S pole of switch tube Q2 are both connected to the other end of input capacitor C3;

[0028] One end of the input capacitor C3 is also connected to the D pole of the switch tube Q3, and the other end of the input capacitor C3 is also connected to the S pole of the switch tube Q4;

[0029] One end of the switch tube Q3 is also connected to one end of the input capacitor C4, and the other end of the switch tube Q3 is connected to the D pole of the switch tube Q4 and one end of N1 respectively;

[0030] The S pole of the switch tube Q4 is also connected to the other end of the input capacitor C5;

[0031] The other end of the input capacitor C4 is connected to one end of the input capacitor C5;

[0032] One end of the input capacitor C5 is also connected to one end of the resonant inductor Lr, and the other end of the resonant inductor Lr is connected to the other end of N1;

[0033] The anode of diode D3 is connected to one end of N2, and the cathode of diode D3 is connected to the cathode of diode D5;

[0034] The cathode of diode D4 is connected to the anode of diode D3, and the anode of diode D4 is connected to the anode of diode D6;

[0035] The anode of diode D5 is connected to the cathode of diode D6, and the cathode of diode D6 is also connected to the other end of N2;

[0036] The anode of diode D7 is connected to one end of N3, and the cathode of diode D7 is connected to the cathode of diode D9;

[0037] The cathode of diode D8 is connected to the anode of diode D7, and the anode of diode D8 is connected to the anode of diode D10;

[0038] The anode of diode D9 is connected to the cathode of diode D10, and the cathode of diode D10 is also connected to the other end of N3;

[0039] The first subunit of the cascaded H-bridge module includes an H4 bridge inverter consisting of an input capacitor C6, a switch tube Q5, a switch tube Q6, a switch tube Q7, and a switch tube Q8;

[0040] The second subunit includes another H4 bridge inverter consisting of an input capacitor C7, a switch tube Q9, a switch tube Q10, a switch tube Q11, and a switch tube Q12;

[0041] The AC filter includes a filter inductor Lf and an input capacitor Cf;

[0042] The cathode of the diode D5 is also connected to one end of the input capacitor C6, and the anode of the diode D6 is also connected to the other end of the input capacitor C6;

[0043] One end of the input capacitor C6 is also connected to the D pole of the switch tube Q5, and the other end of the input capacitor C6 is also connected to the S pole of the switch tube Q6;

[0044] The D-pole of the switch tube Q5 is also connected to the D-pole of the switch tube Q7, and the S-pole of the switch tube Q5 is connected to the D-pole of the switch tube Q6;

[0045] The S pole of the switch tube Q6 is connected to the S pole of the switch tube Q8;

[0046] The S pole of the switch tube Q7 is connected to the D pole of the switch tube Q8;

[0047] The cathode of diode D9 is also connected to one end of input capacitor C7, and the anode of diode D10 is also connected to the other end of input capacitor C7;

[0048] One end of the input capacitor C7 is also connected to the D pole of the switch tube Q9, and the other end of the input capacitor C7 is also connected to the S pole of the switch tube Q10;

[0049] The D-pole of the switch tube Q9 is also connected to the D-pole of the switch tube Q11, and the S-pole of the switch tube Q9 is connected to the D-pole of the switch tube Q10;

[0050] The S pole of the switch tube Q10 is connected to the S pole of the switch tube Q12;

[0051] The S pole of the switch tube Q11 is connected to the D pole of the switch tube Q12;

[0052] One end of the filter inductor Lf is connected to the S pole of the switch tube Q5, and the other end of the filter inductor Lf is connected to the live wire L of the AC power grid;

[0053] The two ends of the input capacitor Cf are connected to the live wire L and the neutral wire N of the AC power grid respectively;

[0054] The S pole of the switch tube Q9 is also connected to the D pole of the switch tube Q8;

[0055] The D pole of the switch tube Q12 is also connected to the neutral line N.

[0056] Furthermore, the AC filter includes a filter inductor Lf1, a filter inductor Lf2, an input capacitor Cf1, and an input capacitor Cf2;

[0057] One end of the filter inductor Lf1 is connected to the S pole of the switch tube Q5, and the other end of the filter inductor Lf1 is connected to the live wire L1;

[0058] One end of the filter inductor Lf2 is connected to the S pole of the switch tube Q9, and the other end of the filter inductor Lf2 is connected to the live wire L2;

[0059] The two ends of the input capacitor Cf1 are connected to the live wire L1 and the neutral wire N respectively;

[0060] The two ends of the input capacitor Cf2 are connected to the live wire L2 and the neutral wire N respectively;

[0061] The D pole of the switch tube Q8 and the S pole of the switch tube Q11 are both connected to the neutral line N.

[0062] Furthermore, the switch tube is a MOS tube or an IGBT tube.

[0063] Furthermore, the grid-connected inverter system further includes a battery pack;

[0064] The battery pack includes several battery subunits, the number of which is equal to the number of subunits of the cascaded H-bridge. The battery subunits are respectively connected between the outputs of the isolated DCDC module and the subunits of the cascaded H-bridge module.

[0065] Furthermore, the battery pack includes a battery subunit Bat1 and a battery subunit Bat2;

[0066] Two ends of the battery subunit Bat1 are connected to two ends of the input capacitor C6 respectively, and two ends of the battery subunit Bat2 are connected to two ends of the input capacitor C7 respectively.

[0067] Furthermore, the grid-connected inverter system further includes a second PV module and a second non-isolated DC / DC module and a second isolated DCDC module;

[0068] The second PV module is electrically connected to the second non-isolated DC / DC module, the second non-isolated DC / DC module is electrically connected to the second isolated DCDC module, and the second isolated DCDC module is electrically connected to the cascade H-bridge;

[0069] Among them, the number of sub-units of the cascaded H-bridge module is the sum of the output branches of the two isolated DCDC modules, and the second non-isolated DC / DC module and the isolated DCDC module are the same as the first non-isolated DC / DC module and the isolated DCDC module.

[0070] Furthermore, the grid-connected inverter system further includes a battery pack; the battery pack includes a battery subunit Bat1, a battery subunit Bat2, a battery subunit Bat3 and a battery subunit Bat4;

[0071] The battery subunit Bat1 and the battery subunit Bat2 are respectively connected to the outputs of the first isolation DCDC module; the battery subunit Bat3 and the battery subunit Bat4 are respectively connected to the outputs of the second isolation DCDC module.

[0072] Furthermore, the cascaded H-bridge module further includes a third subunit and a fourth subunit;

[0073] The third subunit includes another H4 bridge inverter consisting of input capacitor C12, switch tube Q17, switch tube Q18, switch tube Q19, and switch tube Q20;

[0074] The fourth subunit includes another H4 bridge inverter consisting of input capacitor C13, switch tube Q21, switch tube Q22, switch tube Q23, and switch tube Q24;

[0075] The connection circuits of the third subunit and the fourth subunit are the same as the connection circuits of the first subunit and the second subunit;

[0076] The two ends of the battery subunit Bat3 are respectively connected to the two ends of the input capacitor C12, and the two ends of the battery subunit Bat4 are respectively connected to the two ends of the input capacitor C13;

[0077] One end of the filter inductor Lf is connected to the S pole of the switch tube Q5, and the other end of the filter inductor Lf is connected to the live wire L;

[0078] The two ends of the input capacitor Cf are connected to the live wire L and the neutral wire N respectively;

[0079] The D pole of the switch tube Q24 is connected to the neutral line N;

[0080] The D pole of the switch tube Q12 is also connected to the S pole of the switch tube Q17.

[0081] In this solution, the H4 bridge (hereinafter referred to as the H-bridge) has high efficiency and simple topology, and the cascade H-bridge (CHB) can achieve higher output efficiency and better power quality.

[0082] CHB-based PV modules with isolation transformers can fundamentally solve the leakage current problem of photovoltaic systems; the isolated DCDC open-loop operation can achieve high efficiency, and the secondary side can achieve automatic voltage equalization, solving the problem of independent DC sources required for cascaded H-bridges; based on cascaded H-bridges, multi-level output waveforms can be achieved, which can significantly reduce the size and weight of the filter. The H-bridge is easy to modularize and easy to manufacture and maintain.

[0083] In summary, this solution can effectively solve the leakage current problem and improve efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Figure 1 A logic block diagram of a first embodiment of a photovoltaic inverter control system based on a CHB;

[0085] Figure 2 A circuit diagram of a first embodiment of a photovoltaic inverter control system based on a CHB;

[0086] Figure 3 A circuit diagram of a second embodiment of a photovoltaic inverter control system based on a CHB;

[0087] Figure 4 This is a logic block diagram of a third embodiment of a photovoltaic inverter control system based on a CHB;

[0088] Figure 5 A circuit diagram of a third embodiment of a photovoltaic inverter control system based on a CHB;

[0089] Figure 6 This is a logic block diagram of a fourth embodiment of a photovoltaic inverter control system based on a CHB;

[0090] Figure 7 This is a logic block diagram of a fifth embodiment of a photovoltaic inverter control system based on a CHB;

[0091] Figure 8 This is a circuit diagram of a fifth embodiment of a photovoltaic inverter control system based on CHB. DETAILED DESCRIPTION

[0092] The following is further described in detail through specific implementation methods:

[0093] The symbols in the drawings of the specification include: PV module 10, grid-connected inverter system 11, AC grid 12, non-isolated DC / DC module 110, isolated DCDC module 111, cascaded H-bridge module 112, battery pack 113, second PV module 13, second non-isolated DC / DC module 114, second isolated DCDC module 115;

[0094] Example 1

[0095] A photovoltaic inverter control system based on a CHB in this embodiment includes: an electrically connected PV module 10, a grid-connected inverter system 11, and an AC power grid 12; wherein the grid-connected inverter system 11 includes an electrically connected non-isolated DC / DC module 110, an isolated DC / DC module 111, and a cascaded H-bridge module 112;

[0096] The PV module 10 has a number of paths, and the number of non-isolated DC / DC modules 110 and isolated DCDC modules 111 corresponds to the number of PV modules 10;

[0097] The cascaded H-bridge module 112 includes a plurality of sub-units, the number of which is the sum of the output branches of the isolated DCDC module 111 ; each sub-unit is connected to each output branch of the isolated DCDC module 111 .

[0098] The non-isolated DC / DC module 110 is a boost module of the PV module 10 , and in this embodiment, a Boost circuit is used.

[0099] The isolated DCDC module 111 is a unidirectional circuit topology, and electric energy can only flow out of the PV module 10. It is generally a step-down topology, and the transformer is a multi-winding form, which can generally be a single-phase double-winding or single-phase three-winding, depending on the requirements of the subsequent cascade H-bridge module 112.

[0100] The cascaded H-bridge module 112 is a bidirectional topology, and its subunits are respectively connected to the outputs of the isolated DCDC module 111. The cascade form can be diversified, and can be cascaded in a multi-level form or in a common zero line form.

[0101] like Figure 1 As shown, this embodiment is described with a single-channel PV module 10 .

[0102] Specifically, such as Figure 2 As shown, the non-isolated DC / DC module 110 includes two Boost circuit outputs connected in parallel;

[0103] The first boost circuit includes an input capacitor C1, an energy storage inductor L1, a switch device, and a diode D1. The switch devices used include but are not limited to Si, SiC, or GaN MOS or IGBTs. This embodiment uses a MOS transistor as an example, namely, the switch transistor Q1.

[0104] One end of the input capacitor C1 is connected to the PV1+ terminal, and the other end of the input capacitor C1 is connected to the PV1- terminal;

[0105] One end of the energy storage inductor L1 is connected to one end of the input capacitor C1, and the other end of the energy storage inductor L1 is connected to the positive electrode of the diode D1;

[0106] The D pole of the switch tube Q1 is connected to the other end of the energy storage inductor L1, and the S pole of the switch tube Q1 is connected to the other end of the input capacitor C1;

[0107] The second Boost circuit includes input capacitor C2, energy storage inductor L2, switch tube Q2 and diode D2;

[0108] One end of the input capacitor C2 is connected to the PV2+ terminal, and the other end of the input capacitor C2 is connected to the PV2- terminal;

[0109] One end of the energy storage inductor L2 is connected to one end of the input capacitor C2, and the other end of the energy storage inductor L2 is connected to the positive electrode of the diode D2;

[0110] The D-pole of the switch tube Q2 is connected to the other end of the energy storage inductor L2, and the S-pole of the switch tube Q2 is connected to the other end of the input capacitor C2;

[0111] The PV1+ terminal and the PV2+ terminal are both connected to the positive electrode of the PV module 10; the PV1- terminal and the PV2- terminal are both connected to the negative electrode of the PV module 10;

[0112] The isolated DCDC module 111 includes a primary bridge arm, a secondary bridge arm, and a step-down transformer;

[0113] The primary bridge arm includes a switching device switch tube Q3, a switching device switch tube Q4, an input capacitor C3, an input capacitor C4, an input capacitor C5, and a resonant inductor Lr;

[0114] The secondary bridge arm includes two independent diode rectifier bridges, one diode rectifier bridge includes diode D3, diode D4, diode D5, and diode D6, and the other diode rectifier bridge includes diode D7, diode D8, diode D9, and diode D10.

[0115] The step-down transformer includes a primary winding N1 and secondary windings N2 and N3. In actual use, the number of windings of N2 and N3 can be set to be equal, or the number of windings of N2 can be set to an integer multiple of N3, and N1 is greater than or equal to N2 and N3.

[0116] The cathodes of diodes D1 and D2 are connected to one end of input capacitor C3, while the S terminals of switch tubes Q1 and Q2 are connected to the other end of input capacitor C3. The two boost circuit outputs are connected in parallel to input capacitor C3, connecting non-isolated DC / DC module 110 and isolated DC-DC module 111. Due to the presence of the boost circuit, the voltage across input capacitor C3 is greater than or equal to the voltage across input capacitors C1 and C2.

[0117] One end of the input capacitor C3 is also connected to the D pole of the switch tube Q3, and the other end of the input capacitor C3 is also connected to the S pole of the switch tube Q4;

[0118] One end of the switch tube Q3 is also connected to one end of the input capacitor C4, and the other end of the switch tube Q3 is connected to the D pole of the switch tube Q4 and one end of N1 respectively;

[0119] The S pole of the switch tube Q4 is also connected to the other end of the input capacitor C5;

[0120] The other end of the input capacitor C4 is connected to one end of the input capacitor C5;

[0121] One end of the input capacitor C5 is also connected to one end of the resonant inductor Lr, and the other end of the resonant inductor Lr is connected to the other end of N1;

[0122] The anode of diode D3 is connected to one end of N2, and the cathode of diode D3 is connected to the cathode of diode D5;

[0123] The cathode of diode D4 is connected to the anode of diode D3, and the anode of diode D4 is connected to the anode of diode D6;

[0124] The anode of diode D5 is connected to the cathode of diode D6, and the cathode of diode D6 is also connected to the other end of N2;

[0125] The anode of diode D7 is connected to one end of N3, and the cathode of diode D7 is connected to the cathode of diode D9;

[0126] The cathode of diode D8 is connected to the anode of diode D7, and the anode of diode D8 is connected to the anode of diode D10;

[0127] The anode of diode D9 is connected to the cathode of diode D10, and the cathode of diode D10 is also connected to the other end of N3;

[0128] Without loss of generality, the analysis assumes that the number of windings N2 and N3 is equal. The isolated DCDC module 111 operates in open loop at a frequency lower than the first resonant frequency point, which can achieve high efficiency operation of the circuit stage, and the two secondary windings can achieve automatic voltage balancing.

[0129] Each independent output of the isolated DCDC module 111 is connected to the input capacitor of the cascaded H-bridge module 112, for example, the first output of the isolated DCDC module 111 is connected to the input capacitor C6, and the second output of the isolated DCDC module 111 is connected to the input capacitor C7.

[0130] The cascaded H-bridge module 112 includes a first subunit, a second subunit, and an AC filter;

[0131] The first subunit includes an H4 bridge inverter consisting of an input capacitor C6, a switch tube Q5, a switch tube Q6, a switch tube Q7, and a switch tube Q8;

[0132] The second subunit includes another H4 bridge inverter consisting of an input capacitor C7, a switch tube Q9, a switch tube Q10, a switch tube Q11, and a switch tube Q12;

[0133] The AC filter includes a filter inductor Lf and an input capacitor Cf.

[0134] The cathode of the diode D5 is also connected to one end of the input capacitor C6, and the anode of the diode D6 is also connected to the other end of the input capacitor C6;

[0135] One end of the input capacitor C6 is also connected to the D pole of the switch tube Q5, and the other end of the input capacitor C6 is also connected to the S pole of the switch tube Q6;

[0136] The D-pole of the switch tube Q5 is also connected to the D-pole of the switch tube Q7, and the S-pole of the switch tube Q5 is connected to the D-pole of the switch tube Q6;

[0137] The S pole of the switch tube Q6 is connected to the S pole of the switch tube Q8;

[0138] The S pole of the switch tube Q7 is connected to the D pole of the switch tube Q8;

[0139] The cathode of diode D9 is also connected to one end of input capacitor C7, and the anode of diode D10 is also connected to the other end of input capacitor C7;

[0140] One end of the input capacitor C7 is also connected to the D pole of the switch tube Q9, and the other end of the input capacitor C7 is also connected to the S pole of the switch tube Q10;

[0141] The D-pole of the switch tube Q9 is also connected to the D-pole of the switch tube Q11, and the S-pole of the switch tube Q9 is connected to the D-pole of the switch tube Q10;

[0142] The S pole of the switch tube Q10 is connected to the S pole of the switch tube Q12;

[0143] The S pole of the switch tube Q11 is connected to the D pole of the switch tube Q12;

[0144] One end of the filter inductor Lf is connected to the S pole of the switch tube Q5, and the other end of the filter inductor Lf is connected to the live wire L;

[0145] The two ends of the input capacitor Cf are connected to the live wire L and the neutral wire N respectively;

[0146] The S pole of the switch tube Q9 is also connected to the D pole of the switch tube Q8;

[0147] The D pole of the switch tube Q12 is also connected to the neutral line N;

[0148] The cascade connection in this embodiment is a multi-level cascade connection, i.e., the midpoint of the first bridge arm of the first subunit (the midpoint of the switch tube Q5 and the switch tube Q6) is connected to the live wire L, the midpoint of the second bridge arm of the first subunit (the midpoint of the switch tube Q7 and the switch tube Q8) is connected to the midpoint of the first bridge arm of the second subunit (the midpoint of the switch tube Q9 and the switch tube Q10), and the midpoint of the second bridge arm of the subunit (the midpoint of the switch tube Q11 and the switch tube Q12) is connected to the neutral wire N. By cascading two H4 bridges, a five-level bridge arm output voltage can be obtained, which improves the power quality of the inverter waveform and can also reduce the inductance of the AC filter.

[0149] Example 2

[0150] like Figure 3 As shown, the difference between this embodiment and the first embodiment is that the cascade form of the cascaded H-bridge modules 112 is inconsistent. In this embodiment, the AC filter includes a filter inductor Lf1, a filter inductor Lf2, an input capacitor Cf1, and an input capacitor Cf2.

[0151] One end of the filter inductor Lf1 is connected to the S pole of the switch tube Q5, and the other end of the filter inductor Lf1 is connected to the live wire L1;

[0152] One end of the filter inductor Lf2 is connected to the S pole of the switch tube Q9, and the other end of the filter inductor Lf2 is connected to the live wire L2;

[0153] The two ends of the input capacitor Cf1 are connected to the live wire L1 and the neutral wire N respectively;

[0154] The two ends of the input capacitor Cf2 are connected to the live wire L2 and the neutral wire N respectively;

[0155] The D pole of the switch tube Q8 and the S pole of the switch tube Q11 are both connected to the neutral line N.

[0156] That is, the midpoint of the first bridge arm of the first subunit (the midpoint of the switch tube Q5 and the switch tube Q6) is connected to the live wire L1, the midpoint of the second bridge arm of the first subunit (the midpoint of the switch tube Q7 and the switch tube Q8) is connected to the midpoint of the second bridge arm of the second subunit (the midpoint of the switch tube Q11 and the switch tube Q12), and a neutral line N is led out. The midpoint of the first bridge arm of the second subunit (the midpoint of the switch tube Q9 and the switch tube Q10) is connected to the live wire L2. The cascade form is a common zero line cascade, which can realize the phase splitting function, that is, the voltage amplitude from the live wire L1 to the neutral line N is equal to the voltage amplitude from the live wire L2 to the neutral line N, and the phase is opposite. The voltage amplitude between the live wire L1 and L2 is twice the voltage amplitude between any live wire and the neutral line. This circuit topology is compatible with the single-phase three-wire power grid in the United States. Based on Figure 2 The first embodiment can also realize the phase splitting function, and only needs to control the phase inversion.

[0157] Example 3

[0158] like Figure 4 As shown, the difference between this embodiment and the first embodiment is that, in this embodiment, the grid-connected inverter system 11 further includes a battery pack 113;

[0159] The battery pack 113 is connected between the isolated DCDC module 111 and the cascaded H-bridge module 112;

[0160] The battery subunits of the battery pack 113 are respectively connected to the respective outputs of the isolated DCDC module 111, that is, the number of battery subunits in the battery pack 113 is equal to the number of subunits in the cascaded H-bridge. The battery subunits of the battery pack 113 are respectively connected to the subunits of the cascaded H-bridge module 112, and the battery pack 113 can receive energy from the PV module 10 and can also exchange its energy bidirectionally with the AC power grid 12.

[0161] Specifically, such as Figure 5 As shown, the two ends of the battery subunit Bat1 are respectively connected to the two ends of the input capacitor C6, and the two ends of the battery subunit Bat2 are respectively connected to the two ends of the input capacitor C7; the photovoltaic storage and charging integration of the 5-level inverter can be realized.

[0162] Example 4

[0163] like Figure 6 As shown, the difference between this embodiment and the first embodiment is that this embodiment further includes a second PV module 13, and the grid-connected inverter system 11 further includes a second non-isolated DC / DC module 114 and a second isolated DCDC module 115;

[0164] The second PV module 13 is electrically connected to the second non-isolated DC / DC module 114, the second non-isolated DC / DC module 114 is electrically connected to the second isolated DCDC module 115, and the second isolated DCDC module 115 is electrically connected to the cascade H-bridge;

[0165] That is, a unidirectional energy path is formed by the second PV module 13 , the second non-isolated DC / DC module 114 , and the second isolated DCDC module 115 , and flows into the AC grid 12 through the cascaded H-bridge module 112 .

[0166] Among them, the number of sub-units of the cascaded H-bridge module 112 needs to be synchronously increased to the sum of the output branches of the two isolated DCDC modules. The first non-isolated DC / DC module 110 is the same as the second non-isolated DC / DC module 114, and the first isolated DCDC module 111 is the same as the second isolated DCDC module 115.

[0167] Example 5

[0168] like Figure 7As shown, the difference between this embodiment and the fourth embodiment is that, in this embodiment, the grid-connected inverter system 11 further includes a battery pack 113;

[0169] The battery pack 113 is connected between the two isolated DCDC modules and the cascaded H-bridge module 112;

[0170] The battery subunits of the battery pack 113 are respectively connected to the outputs of the first isolated DCDC module 111 and the second isolated DCDC module 115; that is, the number of battery subunits in the battery pack 113 is equal to the number of subunits in the cascaded H-bridge, and the battery pack 113 can receive energy from the first PV module 10 and the second PV module 13, and its energy can also be bidirectionally exchanged with the AC power grid 12.

[0171] like Figure 8 As shown, specifically, the cascade H-bridge module 112 further includes a third subunit and a fourth subunit;

[0172] The third subunit includes another H4 bridge inverter consisting of input capacitor C12, switch tube Q17, switch tube Q18, switch tube Q19, and switch tube Q20;

[0173] The fourth subunit includes another H4 bridge inverter consisting of input capacitor C13, switch tube Q21, switch tube Q22, switch tube Q23, and switch tube Q24;

[0174] The connection circuits of the third subunit and the fourth subunit are the same as the connection circuits of the first subunit and the second subunit;

[0175] The two ends of the battery subunit Bat3 are respectively connected to the two ends of the input capacitor C12, and the two ends of the battery subunit Bat4 are respectively connected to the two ends of the input capacitor C13;

[0176] One end of the filter inductor Lf is connected to the S pole of the switch tube Q5, and the other end of the filter inductor Lf is connected to the live wire L;

[0177] The two ends of the input capacitor Cf are connected to the live wire L and the neutral wire N respectively;

[0178] The D pole of the switch tube Q24 is connected to the neutral line N;

[0179] The D pole of the switch tube Q12 is also connected to the S pole of the switch tube Q17.

[0180] The cascaded H-bridge module 112 of this embodiment has four sub-units, which can achieve 9-level inverter output.

[0181] The above are only embodiments of the present invention, and the present invention is not limited to the fields involved in this implementation case. Common knowledge such as the known specific structures and characteristics in the scheme is not described in detail here. Ordinary technicians in the relevant field are aware of all common technical knowledge in the technical field to which the utility model belongs before the application date or priority date, can obtain all existing technologies in the field, and have the ability to apply conventional experimental means before that date. Ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the inspiration given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A photovoltaic inverter control system based on CHB, comprising electrically connected PV modules and a grid-connected inverter system; characterized in that: The grid-connected inverter system includes an electrically connected non-isolated DC / DC module, an isolated DCDC module, and a cascaded H-bridge module; The PV module has several paths. The number of non-isolated DC / DC modules and isolated DCDC modules corresponds to the number of PV modules. The isolated DCDC module has a unidirectional circuit topology. The cascaded H-bridge module is a bidirectional topology consisting of several sub-units, the number of which is the sum of the output branches of the isolated DCDC module; Each sub-unit is connected to each output branch of the isolation DCDC module respectively; the cascade form includes multi-level cascade and common zero line cascade.

2. The photovoltaic inverter control system based on CHB according to claim 1, characterized in that: The non-isolated DC / DC module includes two Boost circuit outputs connected in parallel; The isolated DCDC module includes an electrically connected primary bridge arm, a step-down transformer, and a secondary bridge arm; the secondary bridge arm includes two independent diode rectifier bridges; The cascaded H-bridge module includes a first subunit, a second subunit and an AC filter; The two boost circuit outputs are connected to the primary bridge arm; the two diode rectifier bridge outputs are connected to the first subunit and the second subunit of the cascaded H-bridge module respectively; The first subunit and the second subunit are connected to an AC filter, and the AC filter is also connected to an external AC power grid.

3. The photovoltaic inverter control system based on CHB according to claim 2, characterized in that: The first Boost circuit of the non-isolated DC / DC module includes an input capacitor C1, an energy storage inductor L1, a switch tube Q1 and a diode D1; One end of the input capacitor C1 is connected to the PV1+ terminal, and the other end of the input capacitor C1 is connected to the PV1- terminal; One end of the energy storage inductor L1 is connected to one end of the input capacitor C1, and the other end of the energy storage inductor L1 is connected to the positive electrode of the diode D1; The D pole of the switch tube Q1 is connected to the other end of the energy storage inductor L1, and the S pole of the switch tube Q1 is connected to the other end of the input capacitor C1; The second Boost circuit includes input capacitor C2, energy storage inductor L2, switch tube Q2 and diode D2; One end of the input capacitor C2 is connected to the PV2+ terminal, and the other end of the input capacitor C2 is connected to the PV2- terminal; One end of the energy storage inductor L2 is connected to one end of the input capacitor C2, and the other end of the energy storage inductor L2 is connected to the positive electrode of the diode D2; The D-pole of the switch tube Q2 is connected to the other end of the energy storage inductor L2, and the S-pole of the switch tube Q2 is connected to the other end of the input capacitor C2; PV1+ and PV2+ are both connected to the positive pole of the PV module; PV1- and PV2- are both connected to the negative pole of the PV module; The primary bridge arm of the isolated DCDC module includes switching devices Q3 and Q4, input capacitors C3, C4, C5, and resonant inductor Lr. The secondary bridge arm includes two independent diode rectifier bridges, one diode rectifier bridge includes diode D3, diode D4, diode D5, and diode D6, and the other diode rectifier bridge includes diode D7, diode D8, diode D9, and diode D10; The step-down transformer includes a primary winding N1 and secondary windings N2 and N3; The cathode of diode D1 and diode D2 are both connected to one end of input capacitor C3, and the S pole of switch tube Q1 and S pole of switch tube Q2 are both connected to the other end of input capacitor C3; One end of the input capacitor C3 is also connected to the D pole of the switch tube Q3, and the other end of the input capacitor C3 is also connected to the S pole of the switch tube Q4; One end of the switch tube Q3 is also connected to one end of the input capacitor C4, and the other end of the switch tube Q3 is respectively connected to the D pole of the switch tube Q4 and one end of N1; The S pole of the switch tube Q4 is also connected to the other end of the input capacitor C5; The other end of the input capacitor C4 is connected to one end of the input capacitor C5; One end of the input capacitor C5 is also connected to one end of the resonant inductor Lr, and the other end of the resonant inductor Lr is connected to the other end of N1; The anode of diode D3 is connected to one end of N2, and the cathode of diode D3 is connected to the cathode of diode D5; The cathode of diode D4 is connected to the anode of diode D3, and the anode of diode D4 is connected to the anode of diode D6; The anode of diode D5 is connected to the cathode of diode D6, and the cathode of diode D6 is also connected to the other end of N2; The anode of diode D7 is connected to one end of N3, and the cathode of diode D7 is connected to the cathode of diode D9; The cathode of diode D8 is connected to the anode of diode D7, and the anode of diode D8 is connected to the anode of diode D10; The anode of diode D9 is connected to the cathode of diode D10, and the cathode of diode D10 is also connected to the other end of N3; The first subunit of the cascaded H-bridge module includes an H4 bridge inverter consisting of an input capacitor C6, a switch tube Q5, a switch tube Q6, a switch tube Q7, and a switch tube Q8; The second subunit includes another H4 bridge inverter consisting of an input capacitor C7, a switch tube Q9, a switch tube Q10, a switch tube Q11, and a switch tube Q12; The AC filter includes a filter inductor Lf and an input capacitor Cf; The cathode of the diode D5 is also connected to one end of the input capacitor C6, and the anode of the diode D6 is also connected to the other end of the input capacitor C6; One end of the input capacitor C6 is also connected to the D pole of the switch tube Q5, and the other end of the input capacitor C6 is also connected to the S pole of the switch tube Q6; The D-pole of the switch tube Q5 is also connected to the D-pole of the switch tube Q7, and the S-pole of the switch tube Q5 is connected to the D-pole of the switch tube Q6; The S pole of the switch tube Q6 is connected to the S pole of the switch tube Q8; The S pole of the switch tube Q7 is connected to the D pole of the switch tube Q8; The cathode of diode D9 is also connected to one end of input capacitor C7, and the anode of diode D10 is also connected to the other end of input capacitor C7; One end of the input capacitor C7 is also connected to the D pole of the switch tube Q9, and the other end of the input capacitor C7 is also connected to the S pole of the switch tube Q10; The D-pole of the switch tube Q9 is also connected to the D-pole of the switch tube Q11, and the S-pole of the switch tube Q9 is connected to the D-pole of the switch tube Q10; The S pole of the switch tube Q10 is connected to the S pole of the switch tube Q12; The S pole of the switch tube Q11 is connected to the D pole of the switch tube Q12; One end of the filter inductor Lf is connected to the S pole of the switch tube Q5, and the other end of the filter inductor Lf is connected to the live wire L of the AC power grid; The two ends of the input capacitor Cf are connected to the live wire L and the neutral wire N of the AC power grid respectively; The S pole of the switch tube Q9 is also connected to the D pole of the switch tube Q8; The D pole of the switch tube Q12 is also connected to the neutral line N.

4. The photovoltaic inverter control system based on CHB according to claim 3, characterized in that: The AC filter includes a filter inductor Lf1, a filter inductor Lf2, an input capacitor Cf1, and an input capacitor Cf2; One end of the filter inductor Lf1 is connected to the S pole of the switch tube Q5, and the other end of the filter inductor Lf1 is connected to the live wire L1; One end of the filter inductor Lf2 is connected to the S pole of the switch tube Q9, and the other end of the filter inductor Lf2 is connected to the live wire L2; The two ends of the input capacitor Cf1 are connected to the live wire L1 and the neutral wire N respectively; The two ends of the input capacitor Cf2 are connected to the live wire L2 and the neutral wire N respectively; The D pole of the switch tube Q8 and the S pole of the switch tube Q11 are both connected to the neutral line N.

5. The photovoltaic inverter control system based on CHB according to claim 3, characterized in that: The switch tube is a MOS tube or an IGBT tube.

6. The photovoltaic inverter control system based on CHB according to claim 3, characterized in that: The grid-connected inverter system further includes a battery pack; The battery pack includes several battery subunits, the number of which is equal to the number of subunits of the cascaded H-bridge. The battery subunits are respectively connected between the outputs of the isolated DCDC module and the subunits of the cascaded H-bridge module.

7. The photovoltaic inverter control system based on CHB according to claim 6, characterized in that: The battery pack includes a battery subunit Bat1 and a battery subunit Bat2; Two ends of the battery subunit Bat1 are connected to two ends of the input capacitor C6 respectively, and two ends of the battery subunit Bat2 are connected to two ends of the input capacitor C7 respectively.

8. The photovoltaic inverter control system based on CHB according to claim 7, characterized in that: Also comprising a second PV module, the grid-connected inverter system further comprises a second non-isolated DC / DC module and a second isolated DCDC module; The second PV module is electrically connected to the second non-isolated DC / DC module, the second non-isolated DC / DC module is electrically connected to the second isolated DCDC module, and the second isolated DCDC module is electrically connected to the cascade H-bridge; Among them, the number of sub-units of the cascaded H-bridge module is the sum of the output branches of the two isolated DCDC modules, and the second non-isolated DC / DC module and the isolated DCDC module are the same as the first non-isolated DC / DC module and the isolated DCDC module.

9. The photovoltaic inverter control system based on CHB according to claim 3, characterized in that: The grid-connected inverter system further includes a battery pack; the battery pack includes a battery subunit Bat1, a battery subunit Bat2, a battery subunit Bat3 and a battery subunit Bat4; The battery subunit Bat1 and the battery subunit Bat2 are respectively connected to the outputs of the first isolation DCDC module; The battery subunit Bat3 and the battery subunit Bat4 are respectively connected to the outputs of the second isolation DCDC module.

10. The photovoltaic inverter control system based on CHB according to claim 9, characterized in that: The cascade H-bridge module further includes a third subunit and a fourth subunit; The third subunit includes another H4 bridge inverter consisting of input capacitor C12, switch tube Q17, switch tube Q18, switch tube Q19, and switch tube Q20; The fourth subunit includes another H4 bridge inverter consisting of input capacitor C13, switch tube Q21, switch tube Q22, switch tube Q23, and switch tube Q24; The connection circuits of the third subunit and the fourth subunit are the same as the connection circuits of the first subunit and the second subunit; The two ends of the battery subunit Bat3 are respectively connected to the two ends of the input capacitor C12, and the two ends of the battery subunit Bat4 are respectively connected to the two ends of the input capacitor C13; One end of the filter inductor Lf is connected to the S pole of the switch tube Q5, and the other end of the filter inductor Lf is connected to the live wire L; The two ends of the input capacitor Cf are connected to the live wire L and the neutral wire N respectively; The D pole of the switch tube Q24 is connected to the neutral line N; The D pole of the switch tube Q12 is also connected to the S pole of the switch tube Q17.

Images