阅读说明：本技术 一种非隔离箝位型三相Heric光伏逆变器拓扑 (Non-isolation clamping type three-phase Heric photovoltaic inverter topology ) 是由 马海啸 张晓峰 兰摘星 于 2019-07-25 设计创作，主要内容包括：本发明涉及一种非隔离箝位型三相Heric光伏逆变器拓扑,该拓扑是由传统三相桥式逆变电路、三相续流电路和箝位电路组成。三相续流电路是由六个开关管通过星形连接构成,该续流电路可使逆变器在续流阶段电流不流经直流电源,省去了能量的回馈,提高了逆变器的转换效率；箝位电路是由三个直流电容和两个箝位开关管构成,三个直流电容将直流源分为0、1/3、2/3和1四个电位点,在1/3和2/3电位点分别加入两个箝位开关,使得续流阶段逆变器共模电压被箝位为直流输入电压的1/3和2/3,减小共模电压幅值,从而抑制了光伏逆变器的漏电流,确保使用时人员和设备的安全。(The invention relates to a non-isolated clamping type three-phase Heric photovoltaic inverter topology which is composed of a traditional three-phase bridge type inverter circuit, a three-phase follow current circuit and a clamping circuit. The three-phase follow current circuit is formed by connecting six switching tubes in a star shape, and current of the inverter can not flow through a direct current power supply in a follow current stage by the follow current circuit, so that energy feedback is omitted, and the conversion efficiency of the inverter is improved; the clamping circuit is composed of three direct current capacitors and two clamping switch tubes, the direct current source is divided into four potential points of 0, 1/3, 2/3 and 1 by the three direct current capacitors, and the two clamping switches are respectively added at the potential points of 1/3 and 2/3, so that the common-mode voltage of the inverter is clamped into 1/3 and 2/3 of direct current input voltage in the follow current stage, the amplitude of the common-mode voltage is reduced, the leakage current of the photovoltaic inverter is restrained, and the safety of personnel and equipment in use is ensured.)

1. The utility model provides a non-isolation clamping type three-phase Heric photovoltaic inverter topology, includes solar photovoltaic cell, traditional three-phase bridge type inverter circuit, three-phase output filter circuit and three-phase load, its characterized in that: the three-phase follow current circuit and the clamping circuit are also included; the traditional three-phase bridge inverter circuit comprises an A-phase upper bridge arm switching tube (S)_a1) Phase A lower bridge arm switch tube (S)_a2) B phase upper bridge arm switch tube (S)_b1) B phase lower bridge arm switch tube (S)_b2) C phase upper bridge arm switch tube (S)_c1) And C phase lower bridge arm switch tube (S)_c2) (ii) a The three-phase output filter circuit comprises an A-phase filter inductor (L)_fa) B phase filter inductor (L)_fb) C phase filter inductor (L)_fc) Phase A filter capacitor (C)_fa) Phase B filter capacitor (C)_fb) And a C-phase filter capacitor (C)_fc) (ii) a The three-phase load comprises an A-phase load (R)_a) Phase B load (R)_b) And C phase load (R)_c) (ii) a The three-phase follow current circuit comprises an A-phase first follow current switch tube (S)_a3) And a phase A second follow current switch tube (S)_a4) First follow current of B phaseSwitch tube (S)_b3) B phase second follow current switch tube (S)_b4) C-phase first follow current switch tube (S)_c3) And C phase second follow current switch tube (S)_c4) (ii) a The clamping circuit comprises a first DC capacitor (C)_dc1) A second DC capacitor (C)_dc2) And a third DC capacitor (C)_dc3) Upper clamping switch tube (S)_H) And a lower clamp switch tube (S)_L) (ii) a Wherein the solar photovoltaic cell (U)_PV) Positive electrode of (2) and first direct current capacitor (C)_dc1) The positive pole and the A phase upper bridge arm switch tube (S)_a1) Collector electrode, B phase upper bridge arm switch tube (S)_b1) Collector and C phase upper bridge arm switch tube (S)_c1) Are respectively connected with the solar photovoltaic cell (U)_PV) Negative electrode of (2) and a third direct current capacitor (C)_dc3) Negative pole of (1), A phase lower arm switching tube (S)_a2) Emitter, B-phase lower arm switch tube (S)_b2) Emitter and C-phase lower bridge arm switching tube (S)_c2) The emitting electrodes of the two phase bridge arm switching tubes are respectively connected with the point Q and the phase A (S)_a1) Emitter of (2) and A phase lower bridge arm switching tube (S)_a2) Collector electrode, A phase filter inductor (L)_fa) And a first freewheeling switch tube of phase A (S)_a3) The collector electrodes of the two phase bridge arm switching tubes are respectively connected with the points A and B (S)_b1) Emitter of (2) and B phase lower bridge arm switch tube (S)_b2) Collector electrode, B-phase filter inductor (L)_fb) And a B-phase first freewheel switching tube (S)_b3) The collector electrodes of the two bridge arm switching tubes are respectively connected with the points B and C (S)_c1) Emitter and C-phase lower bridge arm switching tube (S)_c2) Collector electrode, C phase filter inductor (L)_fc) And a C-phase first freewheel switching tube (S)_c3) Is connected to a point C and a first DC capacitor (C)_dc1) And a second direct current capacitor (C)_dc2) Positive pole, upper clamping switch tube (S)_H) Are connected to a second direct current capacitor (C)_dc2) Negative electrode of (2) and a third direct current capacitor (C)_dc3) Positive and lower clamping switch tube (S)_L) Are respectively connected with the upper clamping switch tube (S)_H) Collector and lower clamping switch tube (S)_L) Collector of (1), and A-phase second freewheel switching tube (S)_a4) Collector electrode, B phaseSecond follow current switch tube (S)_b4) Collector and C-phase second freewheeling switch tube (S)_c4) Are respectively connected with the collectors of the A-phase first follow current switching tubes (S)_a3) Emitter of (2) and A phase second freewheeling switching tube (S)_a4) Is connected with the emitting electrode of the B-phase first follow current switching tube (S)_b3) Emitter of (2) and a B-phase second freewheeling switching tube (S)_b4) Is connected with the emitting electrode of the C-phase first follow current switching tube (S)_c3) Emitter of (2) and C-phase second freewheeling switching tube (S)_c4) Is connected with the emitter of the A-phase filter inductor (L)_fa) The other end of the first phase filter capacitor (C) is connected with the A phase filter capacitor (C)_fa) Positive electrode and A phase load (R)_a) Are connected with each other, a B-phase filter inductor (L)_fb) The other end of the first capacitor and the B-phase filter capacitor (C)_fb) Positive electrode and B phase load (R)_b) Are connected with each other, a C-phase filter inductance (L)_fc) And the other end of the filter capacitor (C) is connected with a phase C filter capacitor (C)_fc) Positive electrode of (2) and C-phase load (R)_c) Are connected to each other, and an A-phase filter capacitor (C)_fa) Negative pole of (2) and B phase filter capacitor (C)_fb) Negative pole, C phase filter capacitor (C)_fc) Negative electrode of (2), A phase load (R)_a) The other end of (2), B-phase load (R)_b) The other end of (2) and a C-phase load (R)_c) The other ends of which are respectively connected to the points N.

2. The non-isolated clamped three-phase Heric photovoltaic inverter topology of claim 1, wherein: through the use of the clamping circuit, the amplitude of the common-mode voltage of the inverter is 1/3 or 2/3 of the DC input voltage; in the whole inversion period of the inverter, calculating the common-mode voltage of the inverter according to the following formula:

u_cm＝(u_AQ+u_BQ+u_CQ)/3

wherein u is_cmIs the common mode voltage of the inverter, u_AQIs the potential difference between the A point and the Q point, u_BQIs the potential difference between B point and Q point, u_CQIs the potential difference between the point C and the point Q.

3. The non-isolated clamped three-phase Heric photovoltaic inverter topology of claim 1, wherein: definition inverterThe switch state is [ M ]₁,M₂,M₃,M₄,M₅]；

Wherein M is₁Representing the switching state of the switching tube of the A-phase bridge arm, M₁1 represents that the switching tube of the upper bridge arm of the A phase is conducted and the switching tube of the lower bridge arm is turned off, and M₁When the switching tube of the upper bridge arm of the A phase is turned off and the switching tube of the lower bridge arm is turned on, M is 0₁Z represents that the switching tubes of the upper and lower bridge arms of the phase A are all turned off; m₂Representing the switching state of the B-phase bridge arm switching tube, M₂1 represents that the switching tube of the upper bridge arm of the B phase is conducted and the switching tube of the lower bridge arm is turned off, and M₂When the upper bridge arm switching tube of the B phase is turned off and the lower bridge arm switching tube of the B phase is turned on, M represents that M represents the number of the upper bridge arm switching tubes of the B phase₂Z represents that the switching tubes of the upper and lower bridge arms of the B phase are all turned off; m₃Representing the switching state of the C-phase bridge arm switching tube, M₃1 represents that the C-phase upper bridge arm switching tube is conducted and the lower bridge arm switching tube is turned off, and M₃When the C-phase upper bridge arm switching tube is turned off and the lower bridge arm switching tube is turned on, M is 0₃Z represents that the switching tubes of the upper and lower bridge arms of the C phase are all turned off; m₄Indicating the switching state of the upper and lower clamping switch tubes of the clamping circuit, M₄1 means that the upper clamping switch tube is conducted and the lower clamping switch tube is turned off, M₄When the upper clamping switch tube is turned off and the lower clamping switch tube is turned on, M is equal to 0₄Z represents that the upper clamping switch tube and the lower clamping switch tube are both turned off; m₅Indicating the switching state of the six switching tubes of the freewheel circuit, M₅1 indicates that six switching tubes of the follow current circuit are all conducted, M₅And 0 represents that the six switching tubes of the freewheeling circuit are all turned off.

4. The non-isolated clamped three-phase Heric photovoltaic inverter topology of claim 1, wherein: the 6 non-freewheeling switching modes of the inverter are [1,0,0, Z,0], [1,1,0, Z,0], [0,1,1, Z,0], [0,0,1, Z,0] and [1,0,1, Z,0], and the 2 freewheeling switching modes are [ Z, Z, Z,1,1] and [ Z, Z, Z,0,1], respectively.

Technical Field

The invention relates to a photovoltaic inverter topology, in particular to a non-isolation clamping type three-phase Heric photovoltaic inverter topology, and belongs to the technical field of power electronic direct current-alternating current conversion.

Background

The photovoltaic inverter is required to have high conversion efficiency and low cost, can bear the adverse effect of large output voltage fluctuation of the photovoltaic cell, and the alternating current output of the inverter also needs to meet higher electric energy quality. The photovoltaic inverter can be classified into an isolated type and a non-isolated type according to whether an isolation transformer is provided or not. The isolated photovoltaic inverter realizes the electrical isolation between a power grid and a battery panel, guarantees the safety of operators and equipment, and is large in size, heavy in weight, high in cost and low in system conversion efficiency. The non-isolated photovoltaic inverter structurally does not contain a transformer, so that the non-isolated photovoltaic inverter has the advantages of small volume, light weight, low cost and the like, but the transformer is not used for electrical isolation, a parasitic capacitor between a photovoltaic cell panel and the ground forms a common-mode loop with the inverter, a filter inductor and a power grid, and leakage current can be generated in the loop along with the high-frequency switching action of a power switching device. The existence of leakage current can increase inverter output current harmonic content, increases electromagnetic interference to reduce electric energy quality, cause the electric wire netting current distortion, cause certain power loss, simultaneously, the leakage current also brings certain hidden danger to operating personnel's safety, consequently, for guarantee personnel and equipment safety, the leakage current must be suppressed in certain within range.

Disclosure of Invention

The invention aims to: aiming at the defects of the prior art, a non-isolated clamping type three-phase Heric photovoltaic inverter topology is provided, the topology can improve the common-mode characteristic of an inverter, improve the conversion efficiency of a system, inhibit common-mode leakage current and guarantee the safety of personnel and equipment.

The invention adopts the following technical scheme for solving the technical problems:

a non-isolated clamping type three-phase Heric photovoltaic inverter topology comprises a solar photovoltaic cell, a traditional three-phase bridge type inverter circuit, a three-phase output filter circuit and a three-phase load, and is characterized by further comprising a three-phase follow current circuit and a clamping circuit; the traditional three-phase bridge inverter circuit comprises an A-phase upper bridge arm switching tube (S)_a1) Phase A lower bridge arm switch tube (S)_a2) B phase upper bridge arm switch tube (S)_b1) B phase lower bridge arm switch tube (S)_b2) C phase upper bridge arm switch tube (S)_c1) And C phase lower bridge arm switch tube (S)_c2) (ii) a Three-phase output filter circuit packageComprises an A-phase filter inductor (L)_fa) B phase filter inductor (L)_fb) C phase filter inductor (L)_fc) Phase A filter capacitor (C)_fa) Phase B filter capacitor (C)_fb) And a C-phase filter capacitor (C)_fc) (ii) a The three-phase load comprises an A-phase load (R)_a) Phase B load (R)_b) And C phase load (R)_c) (ii) a The three-phase follow current circuit comprises an A-phase first follow current switch tube (S)_a3) And a phase A second follow current switch tube (S)_a4) B phase first follow current switch tube (S)_b3) B phase second follow current switch tube (S)_b4) C-phase first follow current switch tube (S)_c3) And C phase second follow current switch tube (S)_c4) (ii) a The clamping circuit comprises a first DC capacitor (C)_dc1) A second DC capacitor (C)_dc2) And a third DC capacitor (C)_dc3) Upper clamping switch tube (S)_H) And a lower clamp switch tube (S)_L) (ii) a Wherein the solar photovoltaic cell (U)_PV) Positive electrode of (2) and first direct current capacitor (C)_dc1) The positive pole and the A phase upper bridge arm switch tube (S)_a1) Collector electrode, B phase upper bridge arm switch tube (S)_b1) Collector and C-phase upper bridge arm switching tube (S)_c1) Are respectively connected with the solar photovoltaic cell (U)_PV) Negative electrode of (2) and a third direct current capacitor (C)_dc3) Negative pole of (1), A phase lower arm switching tube (S)_a2) Emitter, B-phase lower arm switch tube (S)_b2) Emitter and C-phase lower bridge arm switching tube (S)_c2) The emitting electrodes of the two phase bridge arm switching tubes are respectively connected with the point Q and the phase A (S)_a1) Emitter of (2) and A phase lower bridge arm switching tube (S)_a2) Collector electrode, A phase filter inductor (L)_fa) And a first freewheeling switch tube of phase A (S)_a3) The collector electrodes of the two phase bridge arm switching tubes are respectively connected with the points A and B (S)_b1) Emitter of (2) and B phase lower bridge arm switch tube (S)_b2) Collector electrode, B-phase filter inductor (L)_fb) And a B-phase first freewheel switching tube (S)_b3) The collector electrodes of the two bridge arm switching tubes are respectively connected with the points B and C (S)_c1) Emitter and C-phase lower bridge arm switching tube (S)_c2) Collector electrode, C phase filter inductor (L)_fc) And a C-phase first freewheel switching tube (S)_c3) The collector electrodes of (a) are respectively connected to the point C,a first DC capacitor (C)_dc1) And a second direct current capacitor (C)_dc2) Positive pole, upper clamping switch tube (S)_H) Are connected to a second direct current capacitor (C)_dc2) Negative electrode of (2) and a third direct current capacitor (C)_dc3) Positive and lower clamping switch tube (S)_L) Are respectively connected with the upper clamping switch tube (S)_H) Collector and lower clamping switch tube (S)_L) Collector of (1), and A-phase second freewheel switching tube (S)_a4) Collector of (2), and a B-phase second freewheel switching tube (S)_b4) Collector of (2) and C-phase second freewheeling switching tube (S)_c4) Are respectively connected with the collectors of the A-phase first follow current switching tubes (S)_a3) Emitter of (2) and A phase second freewheeling switching tube (S)_a4) Is connected with the emitter of the first follow current switching tube (S) of the B phase_b3) Emitter of (2) and a B-phase second freewheeling switching tube (S)_b4) Is connected with the emitting electrode of the C-phase first follow current switching tube (S)_c3) Emitter of (2) and C-phase second continuous flow switching tube (S)_c4) Is connected with the emitter of the A-phase filter inductor (L)_fa) The other end of the first phase filter capacitor (C) is connected with the A phase filter capacitor (C)_fa) Positive electrode and A phase load (R)_a) Are connected with each other, a B-phase filter inductor (L)_fb) The other end of the first capacitor and the B-phase filter capacitor (C)_fb) Positive electrode and B phase load (R)_b) Are connected with each other, a C-phase filter inductance (L)_fc) The other end of (C) and a phase C filter capacitor (C)_fc) Positive electrode of (2) and C-phase load (R)_c) Are connected to each other, and an A-phase filter capacitor (C)_fa) Negative pole of (2) and B phase filter capacitor (C)_fb) Negative pole, C phase filter capacitor (C)_fc) Negative electrode of (2), A phase load (R)_a) The other end of (2), B-phase load (R)_b) The other end of (2) and a C-phase load (R)_c) The other ends of which are respectively connected to the points N.

As a non-isolation clamping type three-phase Heric photovoltaic inverter topology, the inverter common-mode voltage amplitude is 1/3 or 2/3 of the direct-current input voltage preferably through the use of a clamping circuit. The common-mode voltage of the inverter can be calculated according to the following formula in the whole inversion period of the inverter:

u_cm＝(u_AQ+u_BQ+u_CQ)/3

wherein u is_cmIs the common mode voltage of the inverter, u_AQIs the potential difference between the A point and the Q point, u_BQIs the potential difference between B point and Q point, u_CQIs the potential difference between the point C and the point Q.

As a non-isolated clamping type three-phase Heric photovoltaic inverter topology, the inverter switch state is preferably defined as M₁,M₂,M₃,M₄,M₅]。M₁Representing the switching state of the switching tube of the A-phase bridge arm, M₁1 represents that the switching tube of the upper bridge arm of the A phase is conducted and the switching tube of the lower bridge arm is turned off, and M₁When the phase A of the bridge arm switching tube is turned off and the phase B of the bridge arm switching tube is turned on, M represents that the phase A of the bridge arm switching tube is turned off and the phase B of the bridge arm switching tube is turned on₁Z represents that the switching tubes of the upper and lower bridge arms of the phase A are all turned off; m₂Representing the switching state of the B-phase bridge arm switching tube, M₂1 represents that the switching tube of the upper bridge arm of the B phase is switched on and the switching tube of the lower bridge arm is switched off, and M₂When the upper bridge arm switching tube of the B phase is turned off and the lower bridge arm switching tube of the B phase is turned on, M represents that M represents the number of the upper bridge arm switching tubes of the B phase₂Z represents that the switching tubes of the upper and lower bridge arms of the B phase are all turned off; m₃Representing the switching state of the C-phase bridge arm switching tube, M₃1 represents that the C-phase upper bridge arm switching tube is conducted and the lower bridge arm switching tube is turned off, and M₃When the C-phase upper bridge arm switching tube is turned off and the lower bridge arm switching tube is turned on, M is 0₃Z represents that the switching tubes of the upper and lower bridge arms of the C phase are all turned off; m₄Indicating the switching state of the clamping switch tube, M₄1 means that the upper clamping switch tube is conducted and the lower clamping switch tube is turned off, M₄When the upper clamping switch tube is turned off and the lower clamping switch tube is turned on, M is equal to 0₄Z represents that the upper clamping switch tube and the lower clamping switch tube are both turned off; m₅Indicating the switching state of the six switching tubes of the freewheel circuit, M₅1 indicates that six switching tubes of the follow current circuit are all conducted, M₅0 represents that the six switching tubes of the follow current circuit are all turned off;

therefore, the 6 non-freewheeling switching modes of the inverter are [1,0,0, Z,0], [1,1,0, Z,0], [0,1,1, Z,0], [0,0,1, Z,0] and [1,0,1, Z,0], respectively, and the 2 freewheeling switching modes are [ Z,1,1] and [ Z,0,1], respectively.

Compared with the prior art, the non-isolated clamping type three-phase Heric photovoltaic inverter topology three-phase follow current circuit has the following technical advantages that the inverter is enabled not to flow through a direct current power supply in the follow current stage due to the addition of the non-isolated clamping type three-phase Heric photovoltaic inverter topology three-phase follow current circuit, so that the energy feedback is omitted, and the conversion efficiency of the inverter is improved; the clamping circuit is added, so that the common-mode voltage of the inverter is clamped to 1/3 and 2/3 of the direct-current input voltage in the freewheeling stage, the amplitude of the common-mode voltage is reduced, the leakage current of the photovoltaic inverter is restrained, and the safety of personnel and equipment in use is ensured.

Drawings

The invention will be further described with reference to the accompanying drawings.

Fig. 1 is a main circuit configuration diagram of the present invention.

FIG. 2 is a diagram illustrating a mode one according to the present invention.

Fig. 3 is a schematic diagram of mode two according to the present invention.

Fig. 4 is a schematic diagram of mode three of the present invention.

Fig. 5 is a schematic diagram of mode four of the present invention.

Fig. 6 is a schematic diagram of mode five of the present invention.

Fig. 7 is a schematic diagram of mode six of the present invention.

Fig. 8 is a schematic diagram of mode seven of the present invention.

FIG. 9 is a schematic diagram of mode eight of the present invention.

FIG. 10 is a timing diagram of driving signals according to the present invention.

Detailed Description

The technical scheme of the invention is further explained by combining the accompanying drawings as follows:

the technical scheme of the invention is to provide a non-isolated clamping type three-phase Heric photovoltaic inverter topology, the structure of which is shown in figure 1, and the topology comprises a solar photovoltaic cell, a traditional three-phase bridge type inverter circuit, a three-phase output filter circuit, a three-phase load, a three-phase follow current circuit and a clamping circuit. The traditional three-phase bridge inverter circuit comprises an A-phase upper bridge arm switch tube (S)_a1) Phase A lower bridge arm switch tube (S)_a2) B phase upper bridge arm switchPipe closing (S)_b1) B phase lower bridge arm switch tube (S)_b2) C phase upper bridge arm switch tube (S)_c1) And C phase lower bridge arm switch tube (S)_c2) (ii) a The three-phase output filter circuit comprises an A-phase filter inductor (L)_fa) B phase filter inductor (L)_fb) C phase filter inductor (L)_fc) Phase A filter capacitor (C)_fa) Phase B filter capacitor (C)_fb) And a C-phase filter capacitor (C)_fc) (ii) a The three-phase load comprises an A-phase load (R)_a) Phase B load (R)_b) And C phase load (R)_c) (ii) a The three-phase follow current circuit comprises an A-phase first follow current switch tube (S)_a3) And a phase A second follow current switch tube (S)_a4) B phase first follow current switch tube (S)_b3) B phase second follow current switch tube (S)_b4) C-phase first follow current switch tube (S)_c3) And C phase second follow current switch tube (S)_c4) (ii) a The clamping circuit comprises a first DC capacitor (C)_dc1) A second DC capacitor (C)_dc2) And a third DC capacitor (C)_dc3) Upper clamping switch tube (S)_H) And a lower clamp switch tube (S)_L) (ii) a Wherein the solar photovoltaic cell (U)_PV) Positive electrode of (2) and first direct current capacitor (C)_dc1) The positive pole and the A phase upper bridge arm switch tube (S)_a1) Collector electrode, B phase upper bridge arm switch tube (S)_b1) Collector and C phase upper bridge arm switch tube (S)_c1) Are respectively connected with the solar photovoltaic cell (U)_PV) Negative electrode of (2) and a third direct current capacitor (C)_dc3) Negative pole of (1), A phase lower arm switching tube (S)_a2) Emitter, B-phase lower arm switch tube (S)_b2) Emitter and C-phase lower bridge arm switching tube (S)_c2) The emitting electrodes of the two phase bridge arm switching tubes are respectively connected with the point Q and the phase A (S)_a1) Emitter of (2) and A phase lower bridge arm switching tube (S)_a2) Collector and A-phase filter inductor (L)_fa) And a first freewheeling switch tube of phase A (S)_a3) The collector electrodes of the two phase bridge arm switching tubes are respectively connected with the points A and B (S)_b1) Emitter of (2) and B phase lower bridge arm switch tube (S)_b2) Collector electrode, B-phase filter inductor (L)_fb) And a B-phase first freewheel switching tube (S)_b3) The collector electrodes of the two bridge arm switching tubes are respectively connected with the points B and C (S)_c1) Of the emitterAnd C phase lower bridge arm switch tube (S)_c2) Collector electrode, C phase filter inductor (L)_fc) And a C-phase first freewheel switching tube (S)_c3) Are respectively connected to a point C and a first direct current capacitor (C)_dc1) And a second direct current capacitor (C)_dc2) Positive pole, upper clamping switch tube (S)_H) Are connected to a second direct current capacitor (C)_dc2) Negative electrode of (2) and a third direct current capacitor (C)_dc3) Positive and lower clamping switch tube (S)_L) Are respectively connected with an upper clamping switch tube (S)_H) Collector and lower clamping switch tube (S)_L) Collector of (1), and A-phase second freewheel switching tube (S)_a4) Collector of (2), and a B-phase second freewheeling switching tube (S)_b4) Collector and C-phase second freewheeling switch tube (S)_c4) Are respectively connected with the collectors of the A-phase first follow current switching tubes (S)_a3) Emitter of (2) and A phase second freewheeling switching tube (S)_a4) Is connected with the emitting electrode of the B-phase first follow current switching tube (S)_b3) Emitter of (2) and a B-phase second freewheeling switching tube (S)_b4) Is connected with the emitting electrode of the C-phase first follow current switching tube (S)_c3) Emitter of (2) and C-phase second freewheeling switching tube (S)_c4) Is connected with the emitter of the A-phase filter inductor (L)_fa) The other end of the first phase filter capacitor (C) is connected with the A phase filter capacitor (C)_fa) Positive electrode and A phase load (R)_a) Are connected with each other, a B-phase filter inductor (L)_fb) The other end of the first capacitor and the B-phase filter capacitor (C)_fb) Positive electrode and B phase load (R)_b) Are connected with each other, a C-phase filter inductance (L)_fc) And the other end of the filter capacitor (C) is connected with a phase C filter capacitor (C)_fc) Positive electrode of (2) and C-phase load (R)_c) Are connected to each other, and an A-phase filter capacitor (C)_fa) Negative pole of (2) and B phase filter capacitor (C)_fb) Negative electrode, C phase filter capacitor (C)_fc) Negative electrode of (2), A phase load (R)_a) The other end of (2), B-phase load (R)_b) The other end of (2) and a C-phase load (R)_c) The other ends of which are respectively connected to the points N.

The non-isolation clamping type three-phase Heric photovoltaic inverter provided by the invention can be divided into eight working modes according to the switching states of the three upper bridge arm switching tubes. Defining the inverter switch state as [ M₁,M₂,M₃,M₄,M₅]。M₁Representing the switching state of the switching tube of the A-phase bridge arm, M₁1 represents that the switching tube of the upper bridge arm of the A phase is conducted and the switching tube of the lower bridge arm is turned off, and M₁When the phase A is equal to 0, the switching tube of the upper bridge arm is turned off, the switching tube of the lower bridge arm is turned on, and M is₁Z represents that the switching tubes of the upper and lower bridge arms of the phase A are all turned off; m₂Representing the switching state of the B-phase bridge arm switching tube, M₂1 represents that the switching tube of the upper bridge arm of the B phase is conducted and the switching tube of the lower bridge arm is turned off, and M₂When the upper bridge arm switching tube of the B phase is turned off and the lower bridge arm switching tube of the B phase is turned on, M represents that the upper bridge arm switching tube of the B phase is turned off and the lower bridge arm switching tube of the B phase is turned on₂Z represents that the switching tubes of the upper bridge arm and the lower bridge arm of the B phase are both turned off; m₃Representing the switching state of the C-phase bridge arm switching tube, M₃1 represents that the C-phase upper bridge arm switching tube is conducted and the lower bridge arm switching tube is turned off, and M₃When the C-phase upper bridge arm switching tube is turned off and the lower bridge arm switching tube is turned on, M is 0₃Z represents that the switching tubes of the upper and lower bridge arms of the C phase are all turned off; m₄Indicating the switching state of the upper and lower clamping switch tubes of the clamping circuit, M₄1 means that the upper clamping switch tube is conducted and the lower clamping switch tube is turned off, M₄When the upper clamping switch tube is turned off and the lower clamping switch tube is turned on, M is equal to 0₄Z represents that the upper clamping switch tube and the lower clamping switch tube are both turned off; m₅Indicating the switching state of the six switching tubes of the freewheel circuit, M₅1 indicates that six switching tubes of the follow current circuit are all conducted, M₅And 0 represents that the six switching tubes of the freewheeling circuit are all turned off.

Therefore, the 6 non-freewheeling switching modes of the inverter are [1,0,0, Z,0], [1,1,0, Z,0], [0,1,1, Z,0], [0,0,1, Z,0] and [1,0,1, Z,0], respectively, and the 2 freewheeling switching modes are [ Z,1,1] and [ Z,0,1], respectively. Each mode is as shown in fig. 2 to fig. 9, and the working principle of the inverter in each mode is briefly analyzed as follows:

the first mode is as follows: as shown in FIG. 2, the inverter switching states are [1,0,0, Z,0]Switching tube S_a1、 S_b2And S_c2Is high level, S_a1、S_b2And S_c2In a conducting state; switch tube S_a2、S_b1、S_c1、S_a3、S_a4、S_b3、S_b4、S_c3、S_c4、S_HAnd S_LIs low level, S_a2、S_b1、S_c1、S_a3、S_a4、S_b3、 S_b4、S_c3、S_c4、S_HAnd S_LIn an off state. The current flows from the positive pole of the power supply through S_a1—L_fa—R_aMidpoint N-R_b、R_c—L_fb、L_fc—S_b2、S_c2And then flows back to the negative electrode of the power supply after being grouped. At this time u_AQ＝U_PV，u_BQ＝u_CQ0, so the common mode voltage u_cm＝(u_AQ+u_BQ+u_CQ)/3＝U_PV/3。

Mode two: as shown in FIG. 3, the inverter switching states are [1,1,0, Z,0]]Switching tube S_a1、 S_b1And S_c2Is high level, S_a1、S_b1And S_c2In a conducting state; switch tube S_a2、S_b2、S_c1、S_a3、S_a4、S_b3、S_b4、S_c3、S_c4、S_HAnd S_LIs low level, S_a2、S_b2、S_c1、S_a3、S_a4、S_b3、 S_b4、S_c3、S_c4、S_HAnd S_LIn an off state. The current flows from the positive pole of the power supply through S_a1、S_b1—L_fa、L_fb—R_a、R_bMidpoint N-R_c—L_fc—S_c2And then flows back to the negative electrode of the power supply after being grouped. At this time u_AQ＝u_BQ＝U_PV，u_CQ0, so the common mode voltage u_cm＝(u_AQ+u_BQ+u_CQ)/3＝2U_PV/3。

Mode three: as shown in FIG. 4, the inverter switching states are [0,1,0, Z,0]]Switching tube S_a2、 S_b1And S_c2And a gate ofThe voltage between the emitters is high, S_a2、S_b1And S_c2In a conducting state; switch tube S_a1、S_b2、S_c1、S_a3、S_a4、S_b3、S_b4、S_c3、S_c4、S_HAnd S_LIs low level, S_a1、S_b2、S_c1、S_a3、S_a4、S_b3、 S_b4、S_c3、S_c4、S_HAnd S_LIn an off state. The current flows from the positive pole of the power supply through S_b1—L_fb—R_bMidpoint N-R_a、R_c—L_fa、L_fc—S_a2、S_c2And then flows back to the negative electrode of the power supply after being grouped. At this time u_AQ＝u_CQ＝0，u_BQ＝U_PVSo that the common mode voltage u_cm＝(u_AQ+u_BQ+u_CQ)/3＝U_PV/3。

And a fourth mode: as shown in FIG. 5, the inverter switching states are [0,1,1, Z,0]]Switching tube S_a2、 S_b1And S_c1Is high level, S_a2、S_b1And S_c1In a conducting state; switch tube S_a1、S_b2、S_c2、S_a3、S_a4、S_b3、S_b4、S_c3、S_c4、S_HAnd S_LIs low level, S_a1、S_b2、S_c2、S_a3、S_a4、S_b3、 S_b4、S_c3、S_c4、S_HAnd S_LIn an off state. The current flows from the positive pole of the power supply through S_b1、S_c1—L_fb、L_fc—R_b、R_cMidpoint N-R_a—L_fa—S_a2And then flows back to the negative electrode of the power supply after being grouped. At this time u_AQ＝0，u_BQ＝u_CQ＝U_PVSo that the common mode voltage u_cm＝(u_AQ+u_BQ+u_CQ)/3＝2U_PV/3。

A fifth mode: as shown in FIG. 6, the inverter switching states are [0,0,1, Z,0]]Switching tube S_a2、 S_b2And S_c1Is high level, S_a2、S_b2And S_c1In a conducting state; switch tube S_a1、S_b1、S_c2、S_a3、S_a4、S_b3、S_b4、S_c3、S_c4、S_HAnd S_LIs low level, S_a1、S_b1、S_c2、S_a3、S_a4、S_b3、 S_b4、S_c3、S_c4、S_HAnd S_LIn an off state. The current flows from the positive pole of the power supply through S_c1—L_fc—R_cMidpoint N-R_a、R_b—L_fa、L_fb—S_a2、S_b2And then flows back to the negative electrode of the power supply after being grouped. At this time u_AQ＝u_BQ＝0，u_CQ＝U_PVSo that the common mode voltage u_cm＝(u_AQ+u_BQ+u_CQ)/3＝U_PV/3。

A sixth mode: as shown in FIG. 7, the inverter switching states are [1,0,1, Z,0]]Switching tube S_a1、 S_b2And S_c1Is high level, S_a1、S_b2And S_c1In a conducting state; switch tube S_a2、S_b1、S_c2、S_a3、S_a4、S_b3、S_b4、S_c3、S_c4、S_HAnd S_LIs low level, S_a2、S_b1、S_c2、S_a3、S_a4、S_b3、 S_b4、S_c3、S_c4、S_HAnd S_LIn an off state. The current flows from the positive pole of the power supply through S_a1、S_c1—L_fa、L_fc—R_a、R_cMidpoint N-R_b—L_fb—S_b2And then flows back to the negative electrode of the power supply after being grouped. At this time u_AQ＝u_CQ＝U_PV，u_BQ0, so the common mode voltage u_cm＝(u_AQ+u_BQ+u_CQ)/3＝2U_PV/3。

A seventh mode: as shown in FIG. 8, the inverter switching states are [ Z, Z, Z,1 [ ]]. Once switch tube S_a2、S_b2And S_c2Is simultaneously high level, S_a2、S_b2And S_c2In a conducting state, the switch tube S_a1、S_a2、S_b1、S_b2、S_c1、S_c2Requiring immediate turn-off of the freewheeling switch tube S_a3、S_a4、S_b3、S_b4、S_c3And S_c4And an upper clamping switch tube S_HOn and the current enters the freewheeling stage. The former state of the mode is generally that two of three switching tubes of the lower bridge arm are conducted, and here, the mode one enters the mode seven, and other conditions are similar. At this time, the inductor current flows, and the current flows through L in sequence_fa—R_aMidpoint N-R_b、R_c—L_fb、 L_fc—S_b3、S_c3—S_b4(body diode), S_c4(body diode) -S_a4—S_a3(body diode). In the follow current stage, the solar cell panel is disconnected from the power grid, and the upper clamping switch tube S_HConduction clamps the potential at the point of A, B and C to 2/3 of the input voltage, at which time u is_AQ＝u_BQ＝u_CQ＝2U_PV/3, so common mode voltage u_cm＝(u_AQ+u_BQ+u_CQ)/3＝2U_PV/3。

The mode is eight: as shown in FIG. 9, the inverter switching states are [ Z, Z, Z,0,1]]. Once switch tube S_a1、S_b1And S_c1Is simultaneously high level, S_a1、S_b1And S_c1In a conducting state, the switch tube S_a1、S_a2、S_b1、S_b2、S_c1、S_c2Requiring immediate turn-off of the freewheeling switch tube S_a3、S_a4、S_b3、S_b4、S_c3And S_c4And a lower clamping switch tube S_LOn and the current enters the freewheeling stage. The former state of the mode is generally that two of three switching tubes of an upper bridge arm are conducted, and the mode two enters the mode eight as an example, and other conditions are similar. At this time, the inductor current flows, and the current flows through L in sequence_fa、L_fb—R_a、R_bMidpoint N-R_c—L_fc—S_c3—S_b4(body diode) -S_a4、S_b4—S_a3(body diode), S_b3(body diode). In the follow current stage, the solar cell panel is disconnected from the power grid, and the lower clamping switch tube S_LConduction causes the potential at point A, B and C to be clamped to 1/3 of the input voltage, at which time u is clamped_AQ＝u_BQ＝u_CQ＝U_PV/3, so common mode voltage u_cm＝(u_AQ+u_BQ+u_CQ)/3＝U_PV/3。

From the above analysis, since the voltage of the freewheeling loop of the inverter is clamped to one third and two thirds of the input voltage, the amplitude of the common mode voltage of the inverter varies from 0 to U of the conventional three-phase bridge inverter during the entire inversion period_PVReduced to U_PV/3～2U_PVAnd/3, leakage current in the common mode loop can be effectively inhibited, electromagnetic interference of a system is reduced, the quality of electric energy is improved, the distortion rate of a power grid is reduced, and the safety of personnel and equipment is guaranteed.

FIG. 10 shows a timing diagram of driving signals in a control scheme of the present invention, wherein the waveforms from top to bottom are: a-phase upper bridge arm switch tube S_a1Voltage waveform u between gate and emitter_gea1(ii) a A-phase lower bridge arm switch tube S_a2Voltage waveform u between gate and emitter_gea2(ii) a B-phase upper bridge arm switch tube S_b1Voltage waveform u between gate and emitter_geb1(ii) a B-phase lower bridge arm switch tube S_b2Voltage waveform u between gate and emitter_geb2(ii) a C-phase upper bridge arm switch tube S_c1Voltage waveform u between gate and emitter_gec1(ii) a C-phase lower bridge armSwitch tube S_c2Voltage waveform u between gate and emitter_gec2(ii) a Upper clamping switch tube S_HVoltage waveform u between gate and emitter_geH(ii) a Lower clamping switch tube S_LVoltage waveform u between gate and emitter_geL(ii) a Six switching tubes S of follow current circuit_a3、S_a4、 S_b3、S_b4、S_c3And S_c4Voltage waveform u between gate and emitter_ge34。

In conclusion, the invention solves the technical problems of large leakage current, low conversion efficiency and the like of the non-isolated three-phase photovoltaic inverter, provides a method for inhibiting the leakage current of the non-isolated three-phase photovoltaic inverter, and has a certain engineering application value.

The above description is only for the purpose of illustrating specific embodiments of the present invention and is not intended to limit the scope of the present invention, and any equivalent changes and modifications made by those skilled in the art without departing from the spirit and principles of the present invention should fall within the protection scope of the present invention.