Multi-channel flyback type three-phase photovoltaic grid-connected micro inverter circuit

Abstract

The invention discloses a multi-channel flyback type three-phase photovoltaic grid-connected micro-inverter circuit in the technical field of photovoltaic power generation. The multi-channel flyback type three-phase photovoltaic grid-connected micro-inverter circuit comprises a plurality of flyback circuits, a three-phase direct current bus, a three-phase power frequency commutation bridge circuit and a three-phase filter, wherein the flyback circuits are respectively connected with a plurality of channels of a plurality of photovoltaic modules; each channel flyback circuit is composed of a three-phase flyback converter, the input ends of the three-phase flyback converters are connected in parallel to form the direct-current input end of the flyback circuit of each channel, and the output ends of the three-phase flyback converters are connected to corresponding phases of a three-phase direct-current bus respectively. The direct current side of the three-phase power frequency commutation bridge circuit is connected to a corresponding phase of a three-phase direct current bus, the middle point of the left bridge arm of the three-phase power frequency commutation bridge circuit is connected with a three-phase filter and then connected to a corresponding phase of a three-phase power grid, and the middle point of the right bridge arm of the three-phase power frequency commutation bridge circuit is connected to a zero line of the three-phase power grid. According to the three-phase four-wire grid-connected inverter, high power density and low cost are realized, and high cost performance is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic grid-connected power generation, and in particular to a photovoltaic grid-connected micro-inverter circuit. Background Art

[0002] Both centralized grid-connected inverters and string-connected inverters must be designed based on the voltage and power levels of the photovoltaic array. This results in inflexible system design, particularly in situations of shadowing and hotspot effects, where maximum power point tracking (MPPT) cannot be guaranteed for each photovoltaic module. Consequently, photovoltaic grid-connected microinverters, which can achieve MPPT for each photovoltaic module, have attracted considerable attention. Currently, existing photovoltaic grid-connected microinverters for higher power applications mostly expand capacity by using a simple series-parallel connection of multiple PV modules based on a single-phase microinverter topology, such as by interleaving multi-channel flyback circuits. However, with the continuous increase in PV module power and the demand for microinverter applications in industrial and commercial energy storage, the power level of photovoltaic grid-connected microinverters continues to increase. Continuing to achieve single-phase grid-connected power by increasing the number of channels connected to the DC side of the photovoltaic modules through stacking similar flyback circuits would reduce power density and reliability, while increasing control complexity and cost. If a three-phase photovoltaic grid-connected micro-inverter circuit topology is simply constructed using a single-phase circuit to increase the grid-connected power generation capacity, it is very easy to cause an imbalance in the power generation capacity to the three-phase grid. Summary of the Invention

[0003] In view of the deficiencies in the prior art, the present invention provides a multi-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit to achieve high power density and low cost, thereby obtaining high cost performance.

[0004] The object of the present invention is achieved as follows: a multi-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit, comprising: a flyback circuit of several channels respectively connected to several photovoltaic modules, a three-phase DC bus, a three-phase power frequency commutation bridge circuit, and a three-phase filter;

[0005] Each channel flyback circuit is composed of its own three-phase flyback converter. The input ends of the three-phase flyback converters are connected in parallel to form the DC input ends of the flyback circuit of each channel. The output ends of the three-phase flyback converters are respectively connected to the corresponding phases of the three-phase DC bus. The DC side of the three-phase power frequency commutation bridge circuit is connected to the corresponding phases of the three-phase DC bus. The midpoints of the left bridge arms of the three-phase power frequency commutation bridge circuit are respectively connected to the three-phase filter and then to the corresponding phases of the three-phase power grid. The midpoints of the right bridge arms of the three-phase power frequency commutation bridge circuit are all connected to the neutral line of the three-phase power grid, realizing a three-phase four-wire grid-connected connection.

[0006] Furthermore, the three-phase power frequency commutation bridge circuits have the same composition, and each of the three-phase power frequency commutation bridge circuits is composed of four power switching devices;

[0007] The left bridge arm of the three-phase power frequency commutation bridge circuit is composed of two power switching devices of the four power switching devices connected in series;

[0008] The right bridge arms of the three-phase power frequency commutation bridge circuit are each formed by the other two power switching devices of the four power switching devices being connected in series.

[0009] Furthermore, the positive ends of the upper bridge arm power devices in the left bridge arm of the three-phase power frequency commutation bridge circuit are respectively connected to the positive ends of the corresponding phases on the three-phase DC bus, and the negative ends of the lower bridge arm power devices in the left bridge arm of the three-phase power frequency commutation bridge circuit are respectively connected to the negative ends of the corresponding phases on the three-phase DC bus; the negative ends of the upper bridge arm power devices in the left bridge arm of the three-phase power frequency commutation bridge circuit are respectively connected to the positive ends of the lower bridge arm power devices in the left bridge arm, forming the midpoint of the left bridge arm of the three-phase power frequency commutation bridge circuit;

[0010] The positive ends of the upper bridge arm power devices in the right bridge arm of the three-phase power frequency commutation bridge circuit are respectively connected to the positive ends of the corresponding phases on the three-phase DC bus, and the negative ends of the lower bridge arm power devices in the right bridge arm of the three-phase power frequency commutation bridge circuit are respectively connected to the negative ends of the corresponding phases on the three-phase DC bus; the negative ends of the upper bridge arm power devices in the right bridge arm of the three-phase power frequency commutation bridge circuit are respectively connected to the positive ends of the lower bridge arm power devices in the right bridge arm, forming the midpoint of the right bridge arm of the three-phase power frequency commutation bridge circuit.

[0011] Furthermore, the high-frequency transformer, primary-side switching tube, secondary-side rectifier diode and high-frequency filter capacitor of the three-phase inverter are selected in the same manner, and the input ends of the three-phase inverters in the same channel are connected in parallel and share a decoupling capacitor; the cathode of the single-phase secondary-side rectifier diode of the single-phase inverter in each channel is connected to one end of the single-phase high-frequency filter capacitor and then to the corresponding phase positive end of the three-phase power grid; the other end of the single-phase high-frequency filter capacitor is connected to the corresponding phase negative end of the three-phase power grid.

[0012] Furthermore, the three-phase excitation converter in each channel transmits the energy of the photovoltaic components connected to the respective channels to the three-phase DC bus through control; the three-phase DC bus provides energy to the three-phase power frequency commutation bridge circuit respectively; after the power frequency commutation control of the three-phase power frequency commutation bridge circuit, AC energy is obtained through the left bridge arm and the right bridge arm of the three-phase power frequency commutation bridge circuit, and is sent to the three-phase power grid after filtering by the three-phase filter; the three-phase filter includes an AC side filter inductor and an AC side filter capacitor.

[0013] Furthermore, the three-phase excitation converter in each channel controls the transmission of the energy of the photovoltaic modules connected to the respective channels to the three-phase DC bus. Specifically, the energy of the photovoltaic modules in multiple channels can be evenly distributed to the three-phase DC bus by the three-phase excitation converter in each channel, providing equal energy for the three-phase industrial frequency commutation bridge circuit, thereby achieving balanced power generation on the three-phase AC side grid.

[0014] Furthermore, the power frequency commutation control of the three-phase power frequency commutation bridge circuit is specifically as follows: the power frequency phase sequence of the three-phase power frequency commutation bridge circuit is controlled to lag by 120 electrical degrees in sequence to form a three-phase AC phase sequence; by controlling the peak current in the primary winding of the three-phase excitation converter in each channel, the three-phase grid-connected current output from the grid side lags by 120 electrical degrees in sequence, and tracks the phase of the three-phase grid voltage respectively, thereby realizing grid-connected power generation of photovoltaic modules connected in multiple channels to the three-phase AC grid.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The DC side of the present invention can access multiple photovoltaic modules through multiple channels, and the grid side can achieve grid-connected power generation of phases A, B, and C in the three-phase AC side grid through the A-phase power-frequency commutated bridge circuit, the B-phase power-frequency commutated bridge circuit, and the C-phase power-frequency commutated bridge circuit, thereby achieving a power circuit topology for high-power grid-connected power generation. The circuit topology of the present invention is based on the multi-channel access to photovoltaic modules implemented in a traditional flyback circuit, and therefore has the advantage of achieving maximum power tracking for each photovoltaic module. Because each channel has its own corresponding A-phase flyback converter, B-phase flyback converter, and C-phase flyback converter providing energy to the A-phase DC bus (BusA), the B-phase DC bus (BusB), and the C-phase DC bus (BusC), respectively, control can achieve balanced grid-connected power transmission from the photovoltaic modules in all channels to the A-phase, B-phase, and C-phase of the three-phase AC side grid, thereby ensuring power balance among the A-phase, B-phase, and C-phase grids. The invented multi-channel flyback three-phase photovoltaic grid-connected microinverter circuit topology can easily achieve higher-power grid-connected power generation by expanding the number of channels. In addition, the multi-channel flyback-type three-phase photovoltaic grid-connected micro-inverter circuit topology of the present invention utilizes multi-channel access to photovoltaic modules. The phase A flyback converter, phase B flyback converter, and phase C flyback converter in all channels share the A-phase power frequency commutation bridge circuit, the B-phase power frequency commutation bridge circuit, and the C-phase power frequency commutation bridge circuit, respectively. Furthermore, a set of three-phase filters is shared on the AC grid side, thereby facilitating the realization of high power density and low cost. The three-phase photovoltaic grid-connected micro-inverter circuit topology of the present invention can achieve full digital control using a single digital control chip, thereby reducing the complexity of coordinated control and facilitating control. Therefore, the three-phase photovoltaic grid-connected micro-inverter implemented using the method of the present invention has a high cost-effectiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0018] Figure 1 This is a topological principle diagram of the present invention.

[0019] Figure 2 Schematic diagram of the X-phase industrial frequency commutation bridge circuit of the present invention.

[0020] Figure 3 Schematic diagram of the flyback converter of phase A, phase B and phase C in each channel of the present invention (taking the flyback circuit of channel k# as an example).

[0021] Figure 4 This is the current conversion waveform in the flyback three-phase photovoltaic grid-connected micro-inverter circuit topology of the present invention.

[0022] Figure 5 Schematic diagram of an application of an embodiment of the present invention.

[0023] Figure 6 This is a schematic diagram of an embodiment of the present invention.

[0024] Figure 7 This is a grid-connected power generation simulation waveform of an embodiment of the present invention.

[0025] Figure 8 This is a maximum power tracking diagram of a photovoltaic module according to an embodiment of the present invention.

[0026] Figure 1 Symbolic names in:

[0027]

[0028]

[0029] Figure 2 Symbolic names in:

[0030]

[0031] Figure 3 Symbolic names in:

[0032]

[0033] Other symbols are the same Figure 1 ;

[0034] Figure 4 Symbolic names in:

[0035]

[0036] Other symbols are the same Figure 1 ;

[0037] Figure 5 Symbolic names in:

[0038]

[0039] Other symbols are the same Figure 1 ;

[0040] Figure 6 Symbolic names in:

[0041]

[0042] Other symbols are the same Figure 1 and Figure 5 ;

[0043] Figure 7 The symbol names in Figure 1

[0044] Figure 8 Symbolic names in:

[0045] DETAILED DESCRIPTION

[0046] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0047] like Figure 1 As shown, the components of the present invention are composed of: a flyback circuit 1 for channel 1#, a flyback circuit 2 for channel 2#, a flyback circuit 3 for channel N#, an A-phase power frequency commutation bridge circuit 4, a B-phase power frequency commutation bridge circuit 5, a C-phase power frequency commutation bridge circuit 6 and a three-phase filter 7.

[0048] like Figure 1 and Figure 2As shown, a multi-channel flyback type three-phase photovoltaic grid-connected micro-inverter circuit topology is characterized in that the circuit topology of the invention is composed of a 1# channel flyback circuit 1, a 2# channel flyback circuit 2, an N# channel flyback circuit 3, an A-phase power frequency commutation bridge circuit 4, a B-phase power frequency commutation bridge circuit 5, a C-phase power frequency commutation bridge circuit 6 and a three-phase filter 7; the DC input terminals of the 1# channel flyback circuit 1, the 2# channel flyback circuit 2 and the N# channel flyback circuit 3 are respectively used to connect the 1# channel photovoltaic module PV1, the 2# channel photovoltaic module PV2 and the N# channel photovoltaic module PV N The flyback circuit of each channel is composed of its own phase A flyback converter, phase B flyback converter and phase C flyback converter. The input ends of the phase A flyback converter, phase B flyback converter and phase C flyback converter are connected in parallel to form the DC input end of the flyback circuit of each channel. The output ends of the phase A flyback converter, phase B flyback converter and phase C flyback converter in each channel are respectively connected to the A-phase DC bus (BusA), the B-phase DC bus (BusB) and the C-phase DC bus (BusC); the A-phase power frequency commutation bridge circuit, the B-phase power frequency commutation bridge circuit and the C-phase power frequency commutation bridge circuit are connected to the A-phase power frequency commutation bridge circuit. The DC side of the power-frequency commutated bridge circuit is connected to the A-phase DC bus (BusA), the B-phase DC bus (BusB) and the C-phase DC bus (BusC). The midpoints of the left bridge arms of the A-phase power-frequency commutated bridge circuit 4, the B-phase power-frequency commutated bridge circuit 5 and the C-phase power-frequency commutated bridge circuit 6 are respectively connected to the three-phase filter 7, and then connected to the A-phase, B-phase and C-phase of the three-phase power grid. The midpoints of the right bridge arms of the A-phase power-frequency commutated bridge circuit 4, the B-phase power-frequency commutated bridge circuit 5 and the C-phase power-frequency commutated bridge circuit 6 are all connected to the neutral line of the three-phase power grid, thereby realizing a three-phase four-wire grid-connected connection.

[0049] like Figure 1 As shown, the A-phase power-frequency commutated bridge circuit 4, the B-phase power-frequency commutated bridge circuit 5 and the C-phase power-frequency commutated bridge circuit 6 have the same composition, and the A-phase power-frequency commutated bridge circuit 4, the B-phase power-frequency commutated bridge circuit 5 and the C-phase power-frequency commutated bridge circuit 6 are each composed of four power switching devices. The left bridge arms of the A-phase power-frequency commutated bridge circuit 4, the B-phase power-frequency commutated bridge circuit 5 and the C-phase power-frequency commutated bridge circuit 6 are each composed of two power switching devices in series among the four power switching devices, and the right bridge arms of the A-phase power-frequency commutated bridge circuit 4, the B-phase power-frequency commutated bridge circuit 5 and the C-phase power-frequency commutated bridge circuit 6 are each composed of the other two power switching devices in series among the four power switching devices.

[0050] Figure 2 In the equation, X=A,B,C. Figure 2 The diagram shows the principle of the X-phase power frequency commutation bridge circuit. The X-phase power frequency commutation bridge circuit consists of the thyristor D in the upper bridge arm of the left bridge arm of the X-phase power frequency commutation bridge circuit. X5 , the thyristor D in the upper bridge arm of the right bridge arm of the X-phase power frequency commutation bridge circuitX6 , the power MOS tube Q in the lower bridge arm of the left bridge arm of the X-phase power frequency commutation bridge circuit X5 And the power MOS tube Q in the lower bridge arm of the right bridge arm of the X-phase power frequency commutation bridge circuit X6 The left bridge arm of the X-phase power frequency commutation bridge circuit is composed of the thyristor D in the upper bridge arm of the left bridge arm of the X-phase power frequency commutation bridge circuit. X5 And the power MOS tube Q in the lower bridge arm of the left bridge arm of the X-phase power frequency commutation bridge circuit X5 The right bridge arm of the X-phase power frequency commutation bridge circuit is composed of the thyristor D in the upper bridge arm of the right bridge arm of the X-phase power frequency commutation bridge circuit. X6 And the power MOS tube Q in the lower bridge arm of the right bridge arm of the X-phase power frequency commutation bridge circuit X6 Series structure.

[0051] like Figure 1 As shown, the positive terminals of the upper bridge arm power devices in the left bridge arms of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit 6 are respectively connected to the positive terminal of the A-phase DC bus (BusA+), the positive terminal of the B-phase DC bus (BusB+) and the positive terminal of the C-phase DC bus (BusC+), and the negative terminals of the lower bridge arm power devices in the left bridge arms of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit 6 are respectively connected to the negative terminal of the A-phase DC bus (BusA-), the negative terminal of the B-phase DC bus (BusB-). The negative end of the DC bus (BusB-) and the negative end of the C-phase DC bus (BusC-); the negative ends of the upper bridge arm power devices in the left bridge arms of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit 6 are respectively connected to the positive ends of the lower bridge arm power devices in the left bridge arms of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit 6, forming the midpoint of the left bridge arms of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit 6.

[0052] like Figure 1As shown, the positive terminals of the upper bridge arm power devices in the right bridge arms of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit 6 are respectively connected to the positive terminal of the A-phase DC bus (BusA+), the positive terminal of the B-phase DC bus (BusB+) and the positive terminal of the C-phase DC bus (BusC+), and the negative terminals of the lower bridge arm power devices in the right bridge arms of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit 6 are respectively connected to the negative terminal of the A-phase DC bus (BusA-), the negative terminal of the B-phase DC bus (BusB-). The negative end of the DC bus (BusB-) and the negative end of the C-phase DC bus (BusC-); the negative ends of the upper bridge arm power devices in the right bridge arms of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit 6 are respectively connected to the positive ends of the lower bridge arm power devices in the right bridge arms of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit 6, forming the midpoint of the right bridge arms of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit 6;

[0053] Figure 2 In the equation, X=A,B,C. Figure 2 As shown, the thyristor D in the upper bridge arm of the left bridge arm of the X-phase power frequency commutation bridge circuit 8 X5 The anode is connected to the positive terminal of the X-phase DC bus (BusX+), and the power MOS tube Q in the lower bridge arm of the left bridge arm of the X-phase power frequency commutation bridge circuit is connected to the positive terminal of the X-phase DC bus (BusX+). X5 The source is connected to the negative end of the X-phase DC bus (BusX-), and the thyristor D in the upper bridge arm of the left bridge arm of the X-phase power frequency commutation bridge circuit is connected to the negative end of the X-phase DC bus (BusX-). X5 The cathode is connected to the power MOS tube Q in the lower bridge arm of the left bridge arm of the X phase X5 The drain of the X-phase power frequency commutation bridge circuit forms the midpoint of the left bridge arm. X6 The anode is connected to the positive terminal of the X-phase DC bus (BusX+), and the power MOS tube Q in the lower bridge arm of the right bridge arm of the X-phase power frequency commutation bridge circuit is connected to the positive terminal of the X-phase DC bus (BusX+). X6 The source is connected to the negative end of the X-phase DC bus (BusX-), and the thyristor D in the upper bridge arm of the right bridge arm of the X-phase power frequency commutation bridge circuit is connected to the negative end of the X-phase DC bus (BusX-). X5 The cathode is connected to the power MOS tube Q in the lower bridge arm of the right bridge arm of the X phase X6 , thereby forming the midpoint of the right bridge arm of the X-phase industrial frequency commutation bridge circuit.

[0054] like Figure 1 and Figure 3, the flyback circuit of each channel is composed of its own A-phase flyback converter, B-phase flyback converter and C-phase flyback converter, which is characterized in that the high-frequency transformer, primary-side switch tube, secondary-side rectifier diode and high-frequency filter capacitor of the A-phase flyback converter, B-phase flyback converter and C-phase flyback converter in each channel are selected in the same way, and the input ends of the A-phase flyback converter, B-phase flyback converter and C-phase flyback converter in the same channel are connected in parallel and share a decoupling capacitor; the cathode of the A-phase secondary-side rectifier diode of the A-phase flyback converter in each channel is connected to one end of the A-phase high-frequency filter capacitor and then to the positive end of the A-phase DC bus (BusA+), and the other end of the A-phase high-frequency filter capacitor is connected to the negative end of the A-phase DC bus (BusA-), and the B-phase flyback converter in each channel is connected to the negative end of the A-phase DC bus (BusA-). The cathode of the B-phase secondary rectifier diode of the reverse-inverting converter is connected to one end of the B-phase high-frequency filter capacitor and then to the positive end of the B-phase DC bus (BusB+). The other end of the B-phase high-frequency filter capacitor is connected to the negative end of the B-phase DC bus (BusB-). The cathode of the C-phase secondary rectifier diode of the C-phase reverse-inverting converter in each channel is connected to one end of the C-phase high-frequency filter capacitor and then to the positive end of the C-phase DC bus (BusC+). The other end of the C-phase high-frequency filter capacitor is connected to the negative end of the C-phase DC bus (BusC-). That is, the A-phase high-frequency filter capacitor, the B-phase high-frequency filter capacitor, and the C-phase high-frequency filter capacitor are respectively connected in parallel with the A-phase DC bus (BusA), the B-phase DC bus (BusB), and the C-phase DC bus (BusC).

[0055] Figure 3 In k=1,2,3,···,N. Figure 3 The flyback circuit 9 of channel k# is composed of phase A flyback converter of channel k#, phase B flyback converter of channel k# and phase C flyback converter of channel k#. The phase A flyback converter of channel k# includes phase A high frequency transformer T of channel k#. Ak 、k# channel A phase primary side switch tube Q Ak 、k# channel A phase secondary side rectifier diode D Ak And k# channel A phase high frequency filter capacitor C Ak The B-phase reverse-excitation converter of the k# channel includes a k# channel B-phase high-frequency transformer T Bk 、k# channel B phase primary side switch tube Q Bk 、k# channel B phase secondary side rectifier diode D Bk And k# channel B phase high frequency filter capacitor C Bk The k# channel C phase reverse excitation converter includes a k# channel C phase high frequency transformer T Ck 、k# channel C phase primary side switch tube Q Ck 、k# channel C phase secondary side rectifier diode D Ck And k# channel C phase high frequency filter capacitor C Ck, and the input ends of the phase A reverse converter of k# channel, the phase B reverse converter of k# channel and the phase C reverse converter of k# channel are connected in parallel and share the k# channel decoupling capacitor C ik The k# channel A phase primary side switch tube Q Ak 、k# channel B phase primary side switch tube Q Bk And k# channel C phase primary side switch tube Q Ck The drain of k# channel A phase high frequency transformer T Ak Primary winding, k# channel B phase high frequency transformer T Bk Primary winding and k# channel C phase high frequency transformer T Ck The primary winding is connected to the k# channel A phase primary switch tube Q Ak 、k# channel B phase primary side switch tube Q Bk And k# channel C phase primary side switch tube Q Ck The source of the k# channel photovoltaic module PV k Input negative terminal connection. k# channel A phase high frequency transformer k# channel A phase secondary rectifier diode D Ak The cathode is connected to the high-frequency filter capacitor C of phase A of channel k#. Ak One end is then connected to the positive end of the A-phase DC bus (BusA+), and the k# channel A-phase high-frequency filter capacitor C Ak The other end is connected to the negative end of the k# channel A phase DC bus (BusA-); k# channel B phase high frequency transformer T Bk k# channel B phase secondary rectifier diode D Bk The cathode is connected to the k# channel B phase high frequency filter capacitor C Bk One end is then connected to the positive end of the B-phase DC bus (BusB+), and the k# channel B-phase high-frequency filter capacitor C Bk The other end is connected to the negative end of the DC busbar (BusB-) of the k# channel B phase; the k# channel C phase high frequency transformer T Ck k# channel C phase secondary rectifier diode D Ck The cathode is connected to the k# channel C phase high frequency filter capacitor C Ck One end is then connected to the positive end of the C-phase DC bus (BusC+), and the k# channel C-phase high-frequency filter capacitor C Ck The other end is connected to the negative terminal of the C-phase DC bus of channel k# (BusC-). Figure 3 The k# channel A phase high frequency filter capacitor C Ak , k# channel B phase high frequency filter capacitor C Bk And k# channel C phase high frequency filter capacitor C Ck They are connected in parallel with the A-phase DC bus (BusA), the B-phase DC bus (BusB), and the C-phase DC bus (BusC) respectively.

[0056] The DC input terminals of claim 1 and claim 2 are used to connect the 1# channel photovoltaic module PV1, the 2# channel photovoltaic module PV2 and the 3# channel photovoltaic module PV N , and realize three-phase four-wire grid-connected connection, characterized in that the A-phase flyback converter, the B-phase flyback converter and the C-phase flyback converter in each channel of a multi-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit topology can transmit the energy of the photovoltaic components connected in each channel to the A-phase DC bus (BusA), the B-phase DC bus (BusB) and the C-phase DC bus (BusC) respectively through control; the A-phase DC bus (BusA), the B-phase DC bus (BusB) and the C-phase DC bus (BusC) are respectively the A-phase power frequency commutation bridge circuit 4 , B-phase power frequency commutation bridge circuit 5 and C-phase power frequency commutation bridge circuit 6 provide energy; after the power frequency commutation control of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit 6, AC energy is obtained through the left bridge arm of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit 6, and the right bridge arm of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit 6, and then sent to the three-phase power grid after filtering by the three-phase filter 7. The three-phase filter 7 is composed of the AC side A-phase filter inductor L fA , AC side B phase filter inductor L fB , AC side C phase filter inductor L fC , AC side A phase filter capacitor C fA , AC side B phase filter capacitor C fB , and the AC side C phase filter capacitor C fC constitute.

[0057] like Figure 1 The secondary rectifier output current i of the phase A phase-excited converter, the phase B phase-excited converter and the phase C phase-excited converter in the circuit of the present invention is sA 、i sB and i sC The power frequency commutation control of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit 6 is characterized in that the power frequency phase sequence of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit is controlled to lag by 120 electrical degrees in sequence, thereby forming the following Figure 4 The three-phase AC phase sequence is shown in Figure 1. Figure 4 It can be seen that sA 、i sB and i sC After passing through the three-phase filter 7, the sinusoidal A-phase grid-connected current i gA , B phase grid-connected current i gB and C phase grid-connected current i gC .

[0058] Formed as Figure 4 The three-phase AC phase sequence shown is achieved by controlling the peak current in the primary winding of the A-phase reverse-excitation converter, the B-phase reverse-excitation converter, and the C-phase reverse-excitation converter in each channel, so that the three-phase grid-connected current output from the grid side lags behind by 120 electrical degrees (i gB Lag i gA 120 degrees,i gC Lag i gB 120 degrees,i gA Lag i gC 120 degrees), and respectively track the three-phase grid A phase voltage v gA 、B phase voltage v gB and C phase voltage v gC phase, thereby enabling the photovoltaic modules connected in multiple channels to generate electricity in conjunction with the three-phase AC grid.

[0059] Based on the control, the energy of the photovoltaic components connected to each channel can be transmitted to the A-phase DC bus (BusA), the B-phase DC bus (BusB) and the C-phase DC bus (BusC), and the high-frequency transformer (T) based on the A-phase reverse converter, the B-phase reverse converter and the C-phase reverse converter in each channel. Ak / T Bk / T Ck , k=1,2,…N), primary side switch tube (Q Ak / Q Bk / Q Ck , k=1,2,···,N), secondary side rectifier diode (D Ak / D Bk / D Ck , k=1,2,…N) and high frequency filter capacitors (C Ak / C Bk / C Ck , k=1,2,···,N) are selected in the same way, and the input terminals of the A-phase reverse-phase converter, the B-phase reverse-phase converter, and the C-phase reverse-phase converter in the same k-channel are connected in parallel and share the k# channel decoupling capacitor C. ik (k=1,2,···,N), characterized in that the energy of the photovoltaic modules in multiple channels can be evenly distributed to the A-phase DC bus (BusA), the B-phase DC bus (BusB), and the C-phase DC bus (BusC) by the A-phase reverse-excitation converter, the B-phase reverse-excitation converter, and the C-phase reverse-excitation converter in each channel, thereby providing equal energy to the A-phase power-frequency commutation bridge circuit 4, the B-phase power-frequency commutation bridge circuit 5, and the C-phase power-frequency commutation bridge circuit 6. In this way, the grid-connected power generation power of phases A, B, and C in the three-phase AC side power grid can be balanced.

[0060] A specific embodiment of the present invention is as follows:

[0061] like Figure 5 , which is an application schematic diagram of a three-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit topology constructed using the method of the present invention, and comprises a three-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit topology 9, a sampling and conditioning circuit 10, a maximum power point tracking algorithm and a grid-connected control algorithm 11, and a drive circuit 12. The maximum power point tracking algorithm and the grid-connected control algorithm 11 are implemented by software programming in a digital control chip; Figure 6 The schematic diagram of the circuit topology 9 of a three-channel flyback three-phase photovoltaic grid-connected micro-inverter constructed by the method of the present invention.

[0062] like Figure 5 and Figure 6 As shown, photovoltaic module 1, photovoltaic module 2 and photovoltaic module 3 are respectively connected to the three channels of the three-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit topology 9, and the output voltage v of photovoltaic module 1 is pv1 、The output voltage v of PV module 2 pv2 and the output voltage v of the photovoltaic module 3 pv3 , respectively providing input voltages for the flyback circuit 1 of channel 1#, the flyback circuit 2 of channel 2#, and the flyback circuit 8 of channel 3#; the output current i of the photovoltaic module 1 pv1 , the output current i of PV module 2 pv2 and the output current i of the photovoltaic module 3 pv3 , respectively, provide input current to the flyback circuit of channel 1#, the flyback circuit of channel 2# and the flyback circuit 8 of channel 3; and photovoltaic module 1, photovoltaic module 2 and photovoltaic module 3 are shared by the corresponding phase A flyback converter, phase B flyback converter and phase C flyback converter in the flyback circuit 1 of channel 1#, the flyback circuit 2 of channel 2# and the flyback circuit 8 of channel 3#. The output voltage v pv1 , the output voltage v of PV module 2 pv2 , the output voltage v of photovoltaic module 3 pv3 , the output current i of PV module 1 pv1 , the output current i of PV module 2 pv2 and the output current i of the photovoltaic module 3 pv3 , the A phase voltage v of the three-phase power grid gA , B phase voltage v gB , C phase voltage v gCThe A-phase grid-connected current, the B-phase grid-connected current, and the C-phase grid-connected current of the three-phase grid are all sent to the sampling and conditioning circuit 10. The sampling signals of the corresponding electric quantity obtained after conditioning by the sampling and conditioning circuit 10 are sent to the maximum power point tracking algorithm and grid-connected control algorithm 11 in the digital control chip. The maximum power point tracking algorithm and grid-connected control algorithm 11 achieve the maximum power output of the photovoltaic module of the corresponding channel according to the input voltage and input current sampling signals of the photovoltaic module, and generate the switch tube Q in the three-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit topology 9 required for the corresponding grid-connected current. A1 ,Q B1 ,Q C1 , Q A2 ,Q B2 ,Q C2 , Q A3 , Q B3 , Q C3 The pulse control signal is then passed through the driving circuit 12 to generate the corresponding switch tube driving signal v QA1 ,v QB1 , v QC1 , v QA2 , v QB2 ,v QC2 , v QA3 , v QB3 ,v QC3 Used to control the switch tube Q in the three-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit topology 9 A1 ,Q B1 ,Q C1 , Q A2 ,Q B2 ,Q C2 , Q A3 ,Q B3 ,Q C3 The grid-connected control algorithm in the maximum power point tracking algorithm and grid-connected control algorithm 11 includes a grid voltage phase-locked loop algorithm and a control algorithm for the grid current to track the grid voltage phase. If the grid current tracks the grid voltage phase, grid-connected power generation with a unity power factor of 1 is achieved.

[0063] The power output of this embodiment is 2250W. PV Modules 1, 2, and 3 are each constructed using two 380Wp PV modules connected in parallel. The MPPT voltage range is 20-60Vdc, the grid's rated phase voltage is 230Vac, and the frequency is 50Hz. The digital control chip used is a TI DSP, model TMS320F280049. Figure 6 The primary switch tube Q of the flyback circuit A1 ,Q B1 ,Q C1 ,Q A2 ,QB2 ,Q C2 , Q A3 ,Q B3 ,Q C3 Toshiba MosFeet, model TPH1500CNH, two in parallel (actually 18 pieces are used), with a rated voltage / rated current of 150V / 50A, and a secondary rectifier diode D A1 ,D B1 ,D C1 , D A2 ,D B2 ,D C2 , D A3 ,D B3 ,D C3 All of them use CREE's silicon carbide C4D02120 (actually 9 are used), with a rated voltage and current of 1200V / 5A. A1 ,T B1 ,T C1 , T A2 ,T B2 ,T C2 , T A3 ,T B3 ,T C3 Both use Feimagnetic PQ32 / 30, with 6 turns on the primary side and 36 turns on the secondary side; the decoupling capacitor C i1 =C i2 =C i3 =6400µF, filter capacitor C A1 =C B1 =C C1 =C A2 =C B2 =C C2 =C A3 =C B3 =C C3 =20nF. Thyristor D in the upper bridge arm of the left bridge arm of the A-phase power frequency commutation bridge circuit A5 , thyristor D in the upper bridge arm of the right bridge arm of the A-phase power frequency commutation bridge circuit A6 , thyristor D in the upper bridge arm of the left bridge arm of the B-phase power frequency commutation bridge circuit B5 , thyristor D in the upper bridge arm of the right bridge arm of the B-phase power frequency commutation bridge circuit B6 , thyristor D in the upper bridge arm of the left bridge arm of the C-phase power frequency commutation bridge circuit C5 , thyristor D in the upper bridge arm of the right bridge arm of the C phase power frequency commutation bridge circuit C6 S8008D from Littelfuse is used, and its rated voltage and current are 800V / 8A; the power MOS tube Q A5, the power MOS tube Q in the lower bridge arm of the right bridge arm of the A phase power frequency commutation bridge circuit A6 , the power MOS tube Q in the lower bridge arm of the left bridge arm of the B phase power frequency commutation bridge circuit B5 , the power MOS tube Q in the lower bridge arm of the right bridge arm of the B phase power frequency commutation bridge circuit B6 , the power MOS tube Q in the lower bridge arm of the left bridge arm of the C phase power frequency commutation bridge circuit C5 , the power MOS tube Q in the lower bridge arm of the right bridge arm of the C phase power frequency commutation bridge circuit C6 STB30N80K5 from STMicroelectronics is used, with a rated voltage and current of 800V and 24A. The AC side A phase filter inductor L fA , AC side B phase filter inductor L fB , AC side C phase filter inductor L fC Both are 150µH; AC side A phase filter capacitor C fA , AC side B phase filter capacitor C fB , AC side C phase filter capacitor C fC 390nF high frequency filter capacitors are used.

[0064] The embodiment of the present invention is simulated and verified using Psim. The maximum power point tracking algorithm and the grid-connected control algorithm 11 are implemented by programming with the dynamic link library of Psim: the power frequency phase sequence of the A-phase power frequency commutation bridge circuit 4, the B-phase power frequency commutation bridge circuit 5 and the C-phase power frequency commutation bridge circuit of the three-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit topology 9 is controlled to lag 120 degrees in electrical angle in sequence, thereby forming the following Figure 4 The three-phase AC phase sequence shown in Figure 4 The three-phase AC phase sequence shown in FIG. 1 needs to control the peak currents in the primary windings of the phase A flyback converter, the phase B flyback converter, and the phase C flyback converter in the three channels of the three-channel flyback type three-phase photovoltaic grid-connected micro-inverter circuit topology 9, so that the three-phase grid-connected current output from the grid side lags by 120 electrical degrees (i gB Lag i gA 120 degrees,i gC Lag i gB 120 degrees,i gA Lag i gC 120 degrees), and track the three-phase grid A phase v gA 、B phase v gB and C phase v gC The phase of the voltage. Figure 7 The following is a Psim simulation waveform of a three-channel flyback three-phase photovoltaic grid-connected micro-inverter according to an embodiment of the present invention. gA 、i gB 、i gC They are respectively the A phase grid-connected current, the B phase grid-connected current, and the C phase grid-connected current, vgA 、v gB 、v gC They are the A-phase voltage, B-phase voltage, and C-phase voltage of the power grid respectively; as can be seen from the figure, the sinusoidal A-phase grid-connected current i on the three-phase power grid side is obtained by control. gA , B phase grid-connected current i gB and C phase grid-connected current i gC , and lags behind by 120 electrical degrees in turn. Thus, three-phase grid-connected power generation based on the circuit topology of the present invention is realized. Figure 7 In the example, the grid-connected current of phase A is i gA , B phase grid-connected current i gB , C phase grid-connected current i gC The sine peak value is 3.69A, and the A phase voltage v gA , B phase voltage v gB , C phase voltage v gC The peak value of the sine wave is 230V, which shows that the circuit topology of the embodiment outputs 1800W of power.

[0065] The three channels of the embodiment of the present invention are connected to two parallel photovoltaic modules, and the photovoltaic module connected to the 1# channel is configured with a maximum power of 300W and a maximum power point voltage of 34V through the Chroma photovoltaic simulation power supply. Figure 8 From the volt-ampere characteristic curve IV and the power characteristic curve PV of the 1# channel PV module, we can see that the open-circuit voltage (Voc) of the 1# channel PV module is 43.63V, the short-circuit current (Isc) of the 1# channel PV module is 9.933A, the maximum power point (Vmp) of the 1# channel PV module is 34V, the maximum power point (Imp) of the 1# channel PV module is 8.824A, and the maximum power point (Pmp) of the 1# channel PV module is 300W. This shows that the 1# channel PV module has achieved its maximum power output of 300W.

[0066] Therefore, the simulation and experimental results prove that the three-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit topology 9 using the method of the present invention not only realizes the grid-connected power generation of the photovoltaic module to the three-phase power grid through the maximum power point tracking algorithm and the grid-connected control algorithm 11, but also realizes the maximum power point tracking of the photovoltaic module.

[0067] The present invention has the following advantages:

[0068] (1) The method of the present invention adopts a flyback isolation circuit to construct a three-phase photovoltaic grid-connected micro-inverter circuit topology, thereby providing a main circuit for high-power grid-connected power generation. The DC side can be connected to multiple photovoltaic modules through multiple channels, making it easy to achieve high-power photovoltaic grid-connected power generation.

[0069] (2) In each channel, three corresponding flyback converters are designed for the A-phase industrial frequency phase-commutated bridge circuit, the B-phase industrial frequency phase-commutated bridge circuit, and the C-phase industrial frequency phase-commutated bridge circuit. The three flyback converters share the energy of the photovoltaic modules in the same channel. Through control, the photovoltaic modules in each channel can transmit balanced grid-connected power to the three-phase AC side grid, thereby ensuring the power balance of phases A, B, and C of the three-phase grid.

[0070] (3) After adopting multi-channel access to photovoltaic modules, the A-phase reverse-excitation converter, the B-phase reverse-excitation converter and the C-phase reverse-excitation converter in the channel share the A-phase industrial frequency phase-commutation bridge circuit, the B-phase industrial frequency phase-commutation bridge circuit and the C-phase industrial frequency phase-commutation bridge circuit respectively, and share a set of three-phase filters on the AC grid side, which helps to achieve high power density and low cost of the grid-connected inverter, thereby obtaining high cost performance.

[0071] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A multi-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit, characterized in that: include: A flyback circuit, a three-phase DC bus, a three-phase power frequency commutation bridge circuit, and a three-phase filter are connected to several channels of several photovoltaic modules respectively; Each channel flyback circuit is composed of its own three-phase flyback converter. The input ends of the three-phase flyback converters are connected in parallel to form the DC input ends of the flyback circuit of each channel. The output ends of the three-phase flyback converters are respectively connected to the corresponding phases of the three-phase DC bus. The DC side of the three-phase power frequency commutation bridge circuit is connected to the corresponding phases of the three-phase DC bus. The midpoints of the left bridge arms of the three-phase power frequency commutation bridge circuit are respectively connected to the three-phase filter and then to the corresponding phases of the three-phase power grid. The midpoints of the right bridge arms of the three-phase power frequency commutation bridge circuit are all connected to the neutral line of the three-phase power grid, realizing a three-phase four-wire grid-connected connection.

2. The multi-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit according to claim 1, characterized in that: The three-phase power frequency commutation bridge circuits have the same composition, and each of the three-phase power frequency commutation bridge circuits is composed of four power switching devices; The left bridge arm of the three-phase power frequency commutation bridge circuit is composed of two power switching devices of the four power switching devices connected in series; The right bridge arms of the three-phase power frequency commutation bridge circuit are each formed by the other two power switching devices of the four power switching devices being connected in series.

3. The multi-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit according to claim 2, characterized in that: The positive ends of the upper bridge arm power devices in the left bridge arm of the three-phase power frequency commutation bridge circuit are respectively connected to the positive ends of the corresponding phases on the three-phase DC bus, and the negative ends of the lower bridge arm power devices in the left bridge arm of the three-phase power frequency commutation bridge circuit are respectively connected to the negative ends of the corresponding phases on the three-phase DC bus; the negative ends of the upper bridge arm power devices in the left bridge arm of the three-phase power frequency commutation bridge circuit are respectively connected to the positive ends of the lower bridge arm power devices in the left bridge arm, forming the midpoint of the left bridge arm of the three-phase power frequency commutation bridge circuit; The positive ends of the upper bridge arm power devices in the right bridge arm of the three-phase power frequency commutation bridge circuit are respectively connected to the positive ends of the corresponding phases on the three-phase DC bus, and the negative ends of the lower bridge arm power devices in the right bridge arm of the three-phase power frequency commutation bridge circuit are respectively connected to the negative ends of the corresponding phases on the three-phase DC bus; the negative ends of the upper bridge arm power devices in the right bridge arm of the three-phase power frequency commutation bridge circuit are respectively connected to the positive ends of the lower bridge arm power devices in the right bridge arm, forming the midpoint of the right bridge arm of the three-phase power frequency commutation bridge circuit.

4. The multi-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit according to claim 3, characterized in that: The high-frequency transformer, primary-side switching tube, secondary-side rectifier diode and high-frequency filter capacitor of the three-phase inverter are selected in the same manner, and the input ends of the three-phase inverters in the same channel are connected in parallel and share a decoupling capacitor; the cathode of the single-phase secondary-side rectifier diode of the single-phase inverter in each channel is connected to one end of the single-phase high-frequency filter capacitor and then to the corresponding phase positive end of the three-phase power grid; the other end of the single-phase high-frequency filter capacitor is connected to the corresponding phase negative end of the three-phase power grid.

5. The multi-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit according to claim 4, characterized in that: The three-phase excitation converter in each channel controls and transmits the energy of the photovoltaic modules connected to the respective channels to the three-phase DC bus; the three-phase DC bus provides energy to the three-phase power frequency commutation bridge circuit respectively; after the power frequency commutation control of the three-phase power frequency commutation bridge circuit, AC energy is obtained through the left bridge arm and the right bridge arm of the three-phase power frequency commutation bridge circuit, and is sent to the three-phase power grid after filtering by the three-phase filter; the three-phase filter includes an AC side filter inductor and an AC side filter capacitor.

6. The multi-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit according to claim 5, characterized in that: The three-phase excitation converter in each channel controls and transmits the energy of the photovoltaic modules connected to each channel to the three-phase DC bus. Specifically, the energy of the photovoltaic modules in multiple channels can be evenly distributed to the three-phase DC bus by the three-phase excitation converter in each channel, providing equal energy for the three-phase industrial frequency commutation bridge circuit, thereby achieving balanced power generation on the three-phase AC side grid.

7. The multi-channel flyback three-phase photovoltaic grid-connected micro-inverter circuit according to claim 6, characterized in that: The power frequency commutation control of the three-phase power frequency commutation bridge circuit is specifically as follows: the power frequency phase sequence of the three-phase power frequency commutation bridge circuit is controlled to lag by 120 electrical degrees in sequence to form a three-phase AC phase sequence; by controlling the peak current in the primary winding of the three-phase excitation converter in each channel, the three-phase grid-connected current output from the grid side is made to lag by 120 electrical degrees in sequence and track the phase of the three-phase grid voltage respectively, thereby realizing grid-connected power generation of photovoltaic modules connected in multiple channels to the three-phase AC grid.

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