Non-isolated high-gain three-port converter with low leakage current characteristic and control method thereof

Abstract

The invention discloses a non-isolated high-gain three-port converter with a low leakage current characteristic and a control method thereof. The non-isolated high-gain three-port converter comprises a direct-current port I, a direct-current port II and an alternating-current port, the positive electrode of the first direct current port and the positive electrode of the second direct current port are electrically connected with the drain electrode of the first switching device. The negative electrode of the first direct-current port is electrically connected with the source electrode of the third switching device and one end of the third energy storage inductor. The negative electrode of the second direct-current port is electrically connected with one end of the first energy storage inductor. Stable alternating current output under the condition of wide-range photovoltaic voltage fluctuation can be achieved, leakage current is restrained, the size of the converter is reduced through the three-port structure and the single-stage topology, power density is high, efficiency is high, voltage stress of a switching device is low, cost is low, and the converter can be widely applied to various occasions needing direct current / direct current / alternating current conversion.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electricity, and particularly relates to a non-isolated high-gain three-port converter with low leakage current characteristics and a control method thereof. BACKGROUND

[0002] The three-port converter has a wide application prospect in the field of new energy power generation, battery energy storage system and micro-grid construction due to its high-level connection of new energy power generation devices, energy storage devices and loads. Among them, the direct current-direct current-alternating current converter has more advantages in new energy grid connection and other fields compared with the direct current-direct current-direct current three-port converter because it can directly connect the alternating current load and the alternating current grid. At present, the direct current-direct current-alternating current converter is divided into an isolated three-port converter and a non-isolated three-port converter according to whether the alternating current output port uses electrical isolation. The isolated three-port converter needs a high-frequency transformer for electrical isolation, and has large volume and weight, high cost and low power density; the non-isolated three-port converter has smaller volume, light weight and high power density compared with the isolated three-port converter, but when applied to a photovoltaic power generation scene, there is a high leakage current, which will affect the system reliability to a certain extent; in addition, the photovoltaic power generation is greatly affected by environmental factors such as light intensity and environmental temperature, and the voltage fluctuation range is large, so the traditional non-isolated converter is limited by the voltage gain and is difficult to be applied to a wide range of voltage input scenes. In order to meet the requirement of wide range of input voltage, the traditional method needs to add a boost converter in front of the inverter, but the two-stage structure makes the system volume and weight larger, the efficiency is reduced, and the system is complex and high in cost. SUMMARY

[0003] The application aims to disclose a non-isolated high-gain three-port converter with low leakage current characteristics and a control method and system thereof. The application can realize stable alternating current output under the condition of wide range of photovoltaic voltage fluctuation, inhibit leakage current, reduce the volume of the converter through the three-port structure and single-stage topology, has high power density, high efficiency, low voltage stress of switching devices and low cost, and can be widely applied to various occasions requiring direct current / direct current / alternating current conversion.

[0004] To achieve the above-mentioned purpose, the technical scheme of the application is as follows: A non-isolated high-gain three-port converter with low leakage current characteristics comprises a direct current port one 1, a direct current port two 2 and an alternating current port 3; the positive electrode of the direct current port one 1 and the positive electrode of the direct current port two 2 are electrically connected to the drain electrode of a switching device one S 1 The negative electrode of the direct current port one 1 is electrically connected to the source electrode of a switching device three S 3 and an energy storage inductor three L 3one end of the DC port one 1, the positive electrode of the DC port two 2 is electrically connected to the energy storage inductor one L 1 one end of the energy storage inductor one energy storage inductor one L 1 the other end of the energy storage inductor one is electrically connected to the switch device two S 2 the source electrode of the switch device two and the switch device three S 3 the drain electrode of the switch device three and the switch device one S 1 the source electrode of the switch device one and the switch device two S 2 the drain electrode of the switch device two is electrically connected to the energy storage inductor two L 2 one end of the energy storage inductor two energy storage inductor two L 2 the other end of the energy storage inductor two is electrically connected to the switch device four S 4 the drain electrode of the switch device four and the switch device five S 5 the source electrode of the switch device five and the switch device four S 4 the source electrode of the switch device four is grounded and electrically connected to the filter capacitor one C 1 one end of the filter capacitor one C 1 the other end of the filter capacitor one is electrically connected to the switch device five S 5 the drain electrode of the switch device five and the switch device eight S 8 the drain electrode of the switch device eight and the switch device ten S 10 the drain electrode of the switch device ten energy storage inductor three L 3 the other end of the energy storage inductor three is electrically connected to the switch device six S 6 the drain electrode of the switch device six and the switch device seven S 7 the source electrode of the switch device seven and the switch device six S 6 the drain electrode of the switch device six is grounded and electrically connected to the filter capacitor two C 2 one end of the filter capacitor two C 2 the other end of the filter capacitor two is electrically connected to the switch device seven S 7 the source electrode of the switch device seven and the switch device nine S 9 the source electrode of the switch device nine and the switch device eleven S 11 the source electrode of the switch device eleven the switch device eight S8 Source and switching devices nine S 9 Drain connection filter coupling inductor L 4a The same-name terminal, switching device ten S 10 Source and switching devices eleven S 11 Drain connection filter coupling inductor two L 4b Heterogeneous terminals; filter coupling inductor L 4a The three terminals of the filter capacitor are connected to the opposite name. C 3 One end of the filter coupling inductor and one end of AC port 3; L 4b The same terminal connection of the filter capacitor three C 3 The other end and the other end of AC port 3.

[0005] Further improvements, the switching device one S 1 To switching devices eleven S 11 It can be a MOSFET or an IGBT.

[0006] A further improvement is that the three-port converter operates symmetrically in the negative half-cycle and positive half-cycle modes of the output AC voltage.

[0007] A non-isolated, high-gain three-port converter with low leakage current characteristics, when the output voltage 0 < v ac <( v dc1 - v dc2 When the three-port converter operates in buck mode one, the switching device one... S 1 、 Switching device three S 3 Switching devices eight S 8. Switching Devices (Nine) S 9. Switching devices S 10 and switching devices eleven S 11 High-frequency operation, switching device two S 2 Switching devices five S 5 and switching devices seven S 7 On, switching device four S4 and switch device six S 6 off; wherein v ac is the voltage of the AC port 3, v dc is the voltage of the DC port one 1, v dc2 is the voltage of the DC port two 2; when v dc1 - v dc2 ) < V2 v ac < V1 v dc1 , the three-port converter works in the step-down mode two, at this time, switch device one S 1, switch device two S 2 and switch device three S 3 work in high frequency, switch device four S 4, switch device six S 6, switch device nine S 9 and switch device ten S 10 are off, switch device five S 5 , switch device seven S 7 , switch device eight S 8 and switch device eleven S 11 are on; when v ac > V2 v dc1 , the three-port converter works in the step-up mode, at this time, switch device one S 1 is on, switch device two S 2, switch device three S3, switch device four S 4, switch device five S 5 , switch device six S 6 and switch device seven S 7 work in high frequency; wherein, switch device one S 1 to switch device eleven S 11 work in high frequency with a switching frequency of f s and a switching period of T s , fs and T s The relationship is T s =1 / f s ; The three-port converter works in the first buck mode ， Switching device eight S 8 to switching device eleven S 11 High-frequency operation, the three-port converter works in a mode other than the first buck mode, switching device eight S 8 to switching device eleven S 11 Low-frequency operation, the switching frequency of low-frequency operation v ac is the same as the frequency of f o .

[0008] Further improvement, the first buck mode includes mode 1 and mode 2; Mode 1: Switching device one S 1, switching device two S 2, switching device five S 5, switching device seven S 7, switching device eight S 8 and switching device eleven S 11 Conducting, switching device three S 3, switching device four S 4, switching device six S 6, switching device nine S 9 and switching device ten S 10 Off, DC port one 1 through switching device one S 1, switching device five S 5 and switching device seven S 7 to energy storage inductor two L 2 and energy storage inductor three L 3 charging, through switching device eight S 8 and switching device eleven S 11 Output to v ac , energy storage inductor one L 1 through switching device one S 1 and switching device two S 2 to DC port two 2 charging, while filter capacitor one C 1 , filter capacitor two C 2, DC port one 1 and AC port 3 through switch device eight S 8 and switch device eleven S 11 Form a charge and discharge circuit, energy exchange, at this time the energy storage inductance one L 1 release energy, energy storage inductance two L 2 and energy storage inductance three L 3 energy storage; Mode 2: switch device one S 1, switch device four S 4, switch device six S 6, switch device eight S 8 and switch device eleven S 11 Off, switch device two S 2, switch device three S 3, switch device five S 5, switch device seven S 7, switch device nine S 9 and switch device ten S 10 Conduct, energy storage inductance two L 2 and energy storage inductance three L 3 through switch device switch device two S 2, switch device three S 3, switch device five S 5, switch device seven S 7, switch device nine S 9 and switch device ten S 10 Transmit energy to AC port 3, while filter capacitor one C 1 , filter capacitor two C 2 , DC port one 1 and AC port 3 through switch device nine S 9 and switch device ten S 10 Form a charge and discharge circuit, energy exchange, at this time the energy storage inductance one L 1 energy storage, energy storage inductance two L 2 and energy storage inductance three L 3 release energy.

[0009] Further improvement, the said step-down mode two includes mode 3, mode 4 and mode 7; Mode 3: switch device two S 2, switch device five S 5, switch device seven S 7, switch device eight S 8 and switch device eleven S 11Conduct, switch device one S 1, switch device three S 3, switch device four S 4, switch device six S 6, switch device nine S 9 and switch device ten S 10 Turn off, DC port one 1 and DC port two 2 through switch device two S 2, switch device five S 5 and switch device seven S 7 to energy storage inductor two L 2 and energy storage inductor three L 3 charges, while filter capacitor one C 1 , filter capacitor two C 2 , DC port one 1 and AC port 3 through switch device eight S 8 and switch device eleven S 11 Form a charge and discharge loop to exchange energy, at this time energy storage inductor one L 1 energy storage, energy storage inductor two L 2 and energy storage inductor three L 3 energy storage; Mode 4: switch device two S 2, switch device three S 3, switch device five S 5, switch device seven S 7, switch device eight S 8 and switch device eleven S 11 Conduct, switch device one S 1, switch device four S 4, switch device six S 6, switch device nine S 9 and switch device ten S 10 Turn off, DC port one 1 through DC port two 2 to energy storage inductor one L 1 charges, energy storage inductor two L 2 and energy storage inductor three L 3 through switch device two S 2, switch device three S 3, switch device five S 5, switch device seven S 7, switch device eight S 8 and switch device eleven S 11 Power supply to AC port voltage, while filter capacitor one C 1, filter capacitor two C2, AC port 3 through switch device eight S 8 and switch device eleven S 11 form a charge-discharge circuit to exchange energy, at this time energy storage inductor one L 1 energy storage, energy storage inductor two L 2 and energy storage inductor three L 3 release energy; Mode 7: switch device one S 1, switch device two S 2, switch device five S 5, switch device seven S 7, switch device eight S 8 and switch device eleven S 11 conduct, switch device three S 3, switch device four S 4, switch device six S 6, switch device nine S 9 and switch device ten S 10 off, DC port one 1 through switch device one S 1, switch device five S 5, switch device seven S 7, switch device eight S 8 and switch device eleven S 11 power supply to AC port 3, at the same time, energy storage inductor two L 2 and energy storage inductor three L 3 charge, energy storage inductor one L 1 through switch device one S 1 and switch device two S 2 charge to DC port two 2, at the same time, filter capacitor one C 1 , filter capacitor two C 2 , DC port one 1 and AC port 3 through switch device eight S 8 and switch device eleven S 11 form a charge-discharge circuit to exchange energy, at this time energy storage inductor one L 1 release energy, energy storage inductor two L 2 and energy storage inductor three L 3 energy storage.

[0010] Further improvement, the boost mode includes mode 5 and mode 6; Mode 5: switch device one S 1, switch device two S 2, switch device four S 4, switch device sixS 6, switch device eight S 8 and switch device eleven S 11 on, switch device three S3, switch device five S 5, switch device seven S 7, switch device nine S9 and switch device ten S 10 off, direct current port one 1 through switch device four S 4 and switch device six S 6 to energy storage inductor two L 2 and energy storage inductor three L 3 charge, energy storage inductor one L 1 through switch device one S 1 and switch device two S 2 charge direct current port two 2, while filter capacitor one C 1, filter capacitor two C 2, direct current port one 1 and alternating current port 3 through switch device nine S 9 and switch device ten S 10 form a charge and discharge loop, energy exchange, at this time energy storage inductor one L 1 release energy, energy storage inductor two L 2, energy storage inductor three L 3 energy storage mode 6: off device one S 1, switch device three S 3, switch device five S 5, switch device seven S 7, switch device eight S 8 and switch device eleven S 11 on, switch device two S 2, switch device four S 4, switch device six S 6, switch device nine S 9 and switch device ten S 10 off, direct current port one 1 and energy storage inductor two L 2 and energy storage inductor three L 3 through switch device switch device one S 1, switch device five S 5, switch device seven S 7, switch device eight S 8 and switch device eleven S 11 power alternating current port 3, direct current port one 1 through direct current port two 2 and switch device three S 3 to energy storage inductor oneL 1 charging, filter capacitor one C 1 , filter capacitor two C 2 , direct current port one 1 and alternating current port 3 through switch device eight S 8 and switch device eleven S 11 form a charge-discharge circuit, energy exchange is carried out, at this time energy storage inductor one L 1 energy storage, energy storage inductor two L 2 and energy storage inductor three L 3 release energy.

[0011] The present application has the following beneficial effects: The present application has a wide range of step-up and step-down capability; the converter works in boost mode only exists stable DC common mode voltage, zero leakage current is realized; the working time is shorter and the common mode voltage is lower in buck mode, and the leakage current can be ignored; the proposed converter has three ports, which can realize DC-AC wide range step-up and step-down output and DC-DC step-down output, and can realize energy transmission between two DC ports and AC port; the converter is a single-stage non-isolated structure, with high conversion efficiency and high power density; in addition, the switching device voltage stress of the proposed three-port converter is low, and low-voltage switching devices can be selected, with low device cost.

[0012] The present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0013] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application, illustrate the preferred embodiments of the application and assist in explaining the application. In the drawings: Figure 1 The low common mode voltage wide voltage regulation coupled inductor type step-up and step-down inverter circuit topology proposed by the present application.

[0014] Figure 2 The low common mode voltage wide voltage regulation coupled inductor type step-up and step-down inverter control method proposed by the present application.

[0015] Figure 3(a) is a mode 1 working schematic diagram of the low common mode voltage wide voltage regulation coupled inductor type step-up and step-down inverter proposed by the present application.

[0016] Figure 3(b) is a mode 2 working schematic diagram of the low common mode voltage wide voltage regulation coupled inductor type step-up and step-down inverter proposed by the present application.

[0017] Figure 3(c) is a mode 3 working schematic diagram of the low common mode voltage wide voltage regulation coupled inductor type step-up and step-down inverter proposed by the present application.

[0018] Figure 3(d) is a schematic diagram of the operation of the low common-mode voltage wide voltage-adjustable coupled inductor buck-boost inverter mode 4 proposed in this invention.

[0019] Figure 3(e) is a schematic diagram of the operation of the low common-mode voltage wide voltage-adjustable coupled inductor buck-boost inverter mode 5 proposed in this invention.

[0020] Figure 3(f) is a schematic diagram of the operation of the low common-mode voltage wide voltage-adjustable coupled inductor buck-boost inverter mode 6 proposed in this invention.

[0021] Figure 3(g) is a schematic diagram of the operation of the low common-mode voltage wide voltage-adjustable coupled inductor buck-boost inverter mode 7 proposed in this invention.

[0022] Figure 4 This is a schematic diagram of the common-mode equivalent circuit of the non-isolated high-gain three-port converter with low leakage current characteristics proposed in this invention.

[0023] Figure 5 This is the voltage waveform across the energy storage capacitor of the non-isolated high-gain three-port converter with low leakage current characteristics proposed in this invention. Detailed Implementation

[0024] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0025] This invention proposes a non-isolated high-gain three-port converter with low leakage current characteristics (e.g., Figure 1 (Including DC port one, voltage is) v dc1 DC port two, voltage is v dc2 AC port, voltage is v ac Energy storage inductor L 1, L 2, L 3, L 2= L 3. Filtering coupling inductor L 4a and L 4b Semiconductor switching devices S 1, S 2, S 3, S 4, S 5, S 6, S 7, S 8, S 9, S 10 ,S 11 filtering capacitor C 1, C 2, C 3; the positive pole of the first direct current port is connected to the drain of the first transistor S 1, S 6, C 2 and the positive pole of the second direct current port respectively; S 3 the source of the third transistor S 4 the source of the fourth transistor and C 1 the negative pole of the fifth transistor; the positive pole of the second direct current port is connected to the same node as the positive pole of the first direct current port; L 1 is connected to the negative pole of the second direct current port at one end and to the source of the second transistor S 2 at the other end; L 2 is connected to the source of the first transistor S 1 and the drain of the second transistor S 2 at one end and to the drain of the fourth transistor S 4 and the source of the fifth transistor S 5 at the other end; L 3 is connected to the source of the third transistor S 3 and the negative pole of the first direct current port at one end and to the source of the sixth transistor S 6 and the drain of the seventh transistor S 7 at the other end; L 4a is connected to the source of the eighth transistor S 8 and the drain of the ninth transistor S 9 at one end and to the positive pole of the filtering capacitor C 3 at the other end; L 4b is connected to the source of the tenth transistor S 10 and the drain of the eleventh transistor S 11 at one end and to the negative pole of the filtering capacitor C 3 at the other end; v ac is connected to the drain of the twelfth transistor S 1 the positive pole of the thirteenth transistor, C 8 the drain of the fourteenth transistor and S 10 the drain of the fifteenth transistor; S 7 the source of the sixteenth transistor is connected to the negative pole of the seventeenth transistor, S 2 the negative pole of the eighteenth transistor, C 9 the positive pole of the nineteenth transistor and S the drain of the twentieth transistor.9 The source pole and S 11 The source pole; S 8 Source connection to AC port v ac one end and S 9 The drain electrode; S 10 The source connection AC port voltage v ac The other end and S 11 The drain of the coupled inductor. L 4a and L 4b Both ends of the term are different names from each other; The semiconductor switching device described in this embodiment S 1, S 2, S 3, S 4, S 5, S 6, S 7, S 8, S 9, S 10 , S 11 All are either MOSFETs or IGBTs.

[0026] This embodiment provides a control method for a non-isolated high-gain three-port converter with low leakage current characteristics, applied to the aforementioned non-isolated high-gain three-port converter topology. The method includes the following steps: like Figure 2 As shown, the non-isolated high-gain three-port converter with low leakage current characteristics has seven operating modes during the positive half-cycle of the output voltage. The inverter operates in modes 1, 2, 3, 4, 5, 6, and 7, respectively. The converter's operating modes during the negative half-cycle of the output AC voltage are symmetrical to those during the positive half-cycle. The following analysis of the converter is conducted during the positive half-cycle of the output AC voltage. Figure 2 The converter has three operating modes: buck mode 1, buck mode 2, and boost mode. Switching devices. S 1- S 11 The switching frequency during high-frequency operation is f s The switching cycle is T s , f s and T s The relationship isT s =1 / f s ; S 8, S 9, S 10 , S 11 In the converter works in step-down mode 1, high frequency work. S 1 and S 3 switch signal after taking the opposite as S 2 switch signal, S 4 and S 6 switch signal is the same and S 5 and S 7 complementary, S 8 and S 11 switch signal is the same and S 9 and S 10 complementary.

[0027] Converter works in step-down mode 1, that is, the output voltage 0 < Vout < Vbus, v ac < ( v dc1 - v dc2 ), S 1 、S 3, S 8, S 9, S 10 and S 11 high frequency work, on, S 4 and S 6 off, S 2 、S 5 and S 7 on; converter works in step-down mode 2, that is, v dc1 - v dc2 ) < Vout < Vbus, v ac < ( v dc1 , S 1 , S 2 and S 3 high frequency work, S 5 , S 7, S 8 and S 11 turned on, S 4 , S 6 、S 9 and S 10 turned off; the converter operates in boost mode, i.e. v ac > v dc1 , S 1 turned on, S 2 , S 3 , S 4 , S 5 , S 6 , S 7 high frequency operation. Among them S 1 the duty cycle of high frequency operation is d 1, S 3 the duty cycle of high frequency operation is d 2, S 4 and S 6 the duty cycle of high frequency operation is d 2, S 8 and S 11 the duty cycle of high frequency operation is d 4。

[0028] Mode 1: as shown in Fig. 3(a), the converter operates in buck mode 1, the switching devices S 1, S 2, S 8 and S 11 are turned on, the switching devices S 3, S 9 and S 10 are turned off, the switching devices S 4 and S 6 are always turned off, the switching devices S 5 and S 7 are always turned on, the DC port is charged by the switching devices S 1, S 5 and S 7 to the energy storage inductors L 2 and L 3, and the energy storage inductorsS 8 and S 11 output to v ac , the energy storage inductor L 1 through the switching device S 1 and S 2 charges the DC port two, while the filter capacitor C 1 , the filter capacitor C 2 , the DC port one and the AC port through the device S 8 and S 11 forms a charge-discharge loop to exchange energy, at this time the energy storage inductor L 1 releases energy, the inductor L 2 and L 3 stores energy. Mode 1: as shown in Figure 3(a), the converter works in buck mode 1, the switching device S 1, S 2, S 8 and S 11 are turned on, the switching device S 3, S 9 and S 10 are turned off, the switching device S 4 and S 6 are always turned off, the switching device S 5 and S 7 are always turned on, the DC port one through the switching device S 1, S 5 and S 7 charges the energy storage inductor L 2 and L 3, through S 8 and S 11 output to v ac , the energy storage inductor L 1 through the switching device S 1 and S 2 charges the DC port two, while the filter capacitor C 1 , the filter capacitor C 2 , the DC port one and the AC port through the device S 8 and S 11 forms a charge-discharge loop to exchange energy, at this time the energy storage inductor L 1 releases energy, the inductor L 2 and L 3 stores energy.

[0029] Mode 2: As shown in Fig. 3(b), the converter works in step-down mode 1, switch device S 1, S 4, S 6, S 8 and S 11 is turned off, switch device S 2, S 3, S 5, S 7, S 9 and S 10 is turned on, energy storage inductor L 2 and L 3 is charged through switch device S 2, S 3, S 5, S 7, S 9 and S 10 transfers energy to AC port, while filter capacitor C 1 is discharged, filter capacitor C 2 is charged, DC port 1 and AC port pass through switch device S 9 and S 10 forms a charge-discharge loop to exchange energy, at this time energy storage inductor L 1 stores energy, energy storage inductor L 2 and L 3 releases energy.

[0030] Mode 3: As shown in Fig. 3(c), the converter works in step-down mode 2, switch device S 2, S 5, S 7, S 8 and S 11 is turned on, switch device S 1, S 3, S 4, S 6, S 9 and S 10 is turned off, DC port 1 and DC port 2 pass through switch device S 2, S 5 and S 7 to charge energy storage inductor L 2 and L 3, while filter capacitor C 1 is discharged, filter capacitor C 2, DC port one and AC port through switching device S 8 and S 11 forming a charge-discharge loop, energy exchange, at this time the energy storage inductor L 1 energy storage, energy storage inductor L 2 and L 3 energy storage.

[0031] Mode 4: as shown in Figure 3 (d), the converter works in step-down mode 2, switching device S 2, S 3, S 5, S 7, S 8 and S 11 turned on, switching device S 1, S 4, S 6, S 9 and S 10 turned off, DC port one through DC port two to the energy storage inductor L 1 charge, energy storage inductor L 2 and L 3 through switching device S 2, S 3, S 5, S 7, S 8 and S 11 AC port voltage supply, while the filter capacitor C 1, filter capacitor C 2, AC port through switching device S 8 and S 11 forming a charge-discharge loop, energy exchange, at this time the energy storage inductor L 1 energy storage, energy storage inductor L 2 and L 3 release energy.

[0032] Mode 5: as shown in Figure 3 (e), the converter works in step-up mode, switching device S 1, S 2, S 4, S 6, S 8 and S 11 turned on, switching device S 3, S 5, S 7, S 8, S 10 turned off, DC port one through switching deviceS 4、 S 6 to the energy storage inductor L 2、 L 3 charging, the energy storage inductor L 1 through the switching device S 1 and S 2 to the DC port two, while filtering capacitor C 1, filtering capacitor C 2, the DC port one and the AC port through the switching device S 9 and S 10 forming a charge-discharge loop for energy exchange, at this time the energy storage inductor L 1 releases energy, the energy storage inductor L 2、 L 3 energy storage.

[0033] Mode 6: as shown in Fig. 3(f), the converter works in boost mode, the switching device S 1, S 3, S 5, S 7, S 8 and S 11 conducting, the switching device S 2, S 4, S 6, S 9 and S 10 off, the DC port one and the energy storage inductor L 2, L 3 through the switching device S 1, S 5, S 7, S 8 and S 11 powering the AC port, the DC port one through the DC port two and the switching device S 3 to the energy storage inductor L 1 charging, while filtering capacitor C 1 , filtering capacitor C 2 , the DC port one and the AC port through the switching device S 8 and S 11 forming a charge-discharge loop for energy exchange, at this time the energy storage inductor L 1 energy storage, the energy storage inductor L 2, L 3 releases energy.

[0034] Mode 7: As shown in Fig. 3(g), the converter works in buck mode 2, switch device S2 is on, switch device S5 is off S 1, S 2, S 5, S 7, S 8 and S 11 Switch device S5 is on, DC port one is charged by switch device S2 S 3, S 4, S 6, S 9 and S 10 Switch device S2 is off, DC port two is charged by switch device S5 S 1, S 5, S 7, S 8 and S 11 Switch device S5 is off, AC port is powered by switch device S2, energy storage inductor L1 is charged by switch device S2 L 2 and L 3, energy storage inductor L1 is charged by switch device S5 L 1 S 1 and S 2, filter capacitor C1 is charged by switch device S5 C 1 , filter capacitor C1 is charged by switch device S2 C 2 , DC port one and AC port are connected through switch device S5 S 8 and S 11 A charge and discharge loop is formed to exchange energy, at this time energy storage inductor L1 releases energy, energy storage inductor L2 and L3 store energy L 1 L 2 and L 3

[0035] The converter works in buck mode 1, switch devices S2, S5 and S7 are always on, switch devices S1, S3 and S 8-11 High frequency operation, S1 duty ratio is d 1, from the relationship of S1, S2 and S3, S3 duty ratio is 1- d 1; S8 and S 11 duty ratio is d 4, as shown in the accompanying drawings, let the voltage between ab be DC bus voltage Figure 1 v ab。

[0036] (1) Energy storage inductor value L 2 * = L 3 * = L , switch devices S1, S8, S​11 Conducting time has: (2) Switching device S3, S9, S 10 Conducting time has: (3) From formula (1)-(3), the application of volt-second balance and ampere-second balance principle, has: (4) In step-down mode 1, the gain G1 of the alternating current port and the first direct current port is: (5) Converter works in step-down mode 2, switching device S5, S7, S8 and S 11 Always open, the switching signal relationship of switching device S1, S2 and S3 can be obtained, v ab In a switching cycle, only v dc1 And 0 two values, and the value of the corresponding time is complementary, full-bridge switching device S8 and S 11 Always open, corresponding to d 4=1 in formula (5), so the converter works in step-down mode 2, the gain G2 of the alternating current port and the first direct current port is: (6) Converter works in step-up mode, switching device S2, S3, S4, S5, S6 and S7 high-frequency work, S1, S8 and S 11 Always open, switching device S4, S6 duty ratio is d 3, S4, S6 conducting time has: (7) L 2, L 3 series, the current is equal, so S5, S7 conducting time has: (8) Steady state operation, energy storage inductance L 2 and L 3 volt-second balance across the voltage, filter capacitor C 1 And filter C 2 Charging and discharging ampere-second balance, has: (9) The gain G3 of the alternating current port and the first direct current port is: (10) The switching signal relationship of the switching devices S1, S2 and S3 can be obtained, in all operating modes of the converter, S1 and S2 are simultaneously turned on and S3 is turned on complementarily, when S3 is turned on, the direct current port one charges the energy storage inductor L1 to the direct current port two, when S1 and S2 are simultaneously turned on, the energy storage inductor L1 charges the direct current port two to the direct current port one L 1 to the direct current port two.

[0037] When S3 is turned on, there is (11) When S1 and S2 are simultaneously turned on, there is (12) In the steady state operation, the inductor L1 volt-second balance can be obtained (13) The gain G4 of the direct current port two and the direct current port one is: (14) According to the non-isolated high-gain three-port converter control method with low leakage current characteristics, at the mode switching point of the step-down mode 1 and the step-down mode 2 of the non-isolated high-gain three-port converter with low leakage current characteristics, at this time, the full-bridge switching device S 8 and S 11 The duty cycle d 4 = 1, at the step-down mode 2 and step-up mode switching point, the switching device S1 is always on in the step-down mode 2 v ab There are only two values of v dc1 and 0 in one switching period, and the corresponding time of the values is complementary; in the step-up mode, the switching device S1 is always on, at the mode switching point, d 1 = 1, in the step-down mode 2, the switching device S 5、 S 7 is always on, S 4、 S 6 is always off, and the mode switching point d 3 = 0.

[0038] According to the formula (5), the formula (6) and the formula (10), the gain of the non-isolated high-gain three-port converter with low leakage current characteristics at the step-down mode 1 and the step-down mode 2, the step-down mode 2 and the step-up mode switching point is equal.

[0039] As shown in the accompanying Figure 1 and the accompanying Figure 4 , the direct current port one voltage v dc1 and the direct current port two voltage v dc2With the negative terminal as reference ground (GND), the converter operates in both buck mode 1 and buck mode 2, with the total AC output port voltage... v ac common mode voltage v cm It can be represented as: (15) When the converter operates in buck mode 1, the switching devices of the full-bridge circuit operate at high frequency. At this time, the AC output port voltage of the converter... v ac common mode voltage v tcm It can be represented as: (16)

[0040] From equations (15) and (16), it can be seen that the common-mode voltage is constant when the converter is operating in buck mode 2 and boost mode, and there is no leakage current. When operating in buck mode 1, there is leakage current in the system, but the buck mode 1 is maintained for a very short time, so the overall leakage current of the system is maintained at a low level.

[0041] As attached Figure 5 As shown, according to the control method for the non-isolated high-gain three-port converter with low leakage current characteristics, during operation in modes 1 to 7, the switching devices... S 1. S 2 and S 3. Only two devices are conducting at the same time, or only one device is conducting. S 2 is on, when only S 2 conduction, S The voltage across the terminals is v dc2 , S 3. The voltage across the terminals is v dc1 - v dc2 ,when S 1 and S 3. When closed, S 2. The voltage across the switch is the input voltage. v dc1 Switching devices S 4 and S 6. Switch signals are the same as and are S 5 and S 7. Complementary, when S 4 and S When 6 is on, S 5 and S 7. The voltage across both ends of the switch is the DC port voltage. v dc1 and AC port voltage v achalf of the sum of S 5 and S 7 are on, S 4 and S 6 are both DC port one voltage v dc1 and AC port voltage v ac half of the sum of; switching device S 8 and S 11 the same as and with S 9 and S 10 complementary, when S 8 and S 11 are on, S 9 and S 10 are both AC port voltage v ac , when S 9 and S 10 are on, S 8 and S 11 are both AC port voltage v ac Compared with the conventional Buck-Boost structure-based boost-buck inverter, the switching device voltage stress of the inverter is lower under the same input and output voltages.

[0042] The method can realize stable AC output under photovoltaic voltage fluctuation, eliminate high-frequency common-mode voltage on the AC side, and ignore the leakage current caused by the DC common-mode voltage. In addition, the coupling inductor reduces the volume of the converter, has high power density, is single-stage conversion structure, has high efficiency, low switching device voltage stress, low cost, and can be widely applied to various occasions requiring connection of two DC ports and one AC port for DC-AC conversion.

[0043] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A non-isolated high-gain three-port converter with low leakage current characteristics, characterized in that, Includes DC port one (1), DC port two (2), and AC port (3); the positive terminal of DC port one (1) and the positive terminal of DC port two (2) are electrically connected to switching device one ( S 1 The drain of DC port one (1) is connected to the negative terminal of the switching device three ( S 3 The source and energy storage inductor of the three () L 3 One end of the DC port (2) is connected to the negative terminal of the energy storage inductor ( ). L 1 One end of ) Energy storage inductor 1 ( L 1 The other end of the device is electrically connected to the switching device two. S 2 The source and switching devices of the three () S 3 The drain of the switching device; S 1 The source and switching device two () S 2 The drain of the energy storage inductor is connected to the drain of the inductor. L 2 one end of ); Energy storage inductor 2 ( L 2 The other end of the device is electrically connected to the switching device four ( S 4 The drain and switching device of the fifth () S 5 The source of the switching device; four ( S 4 The source of the filter capacitor is grounded and electrically connected to it. C 1 One end of the filter capacitor () C 1 The other end is electrically connected to the electrical connection switching device five ( S 5 The drain of the switching device (8) S 8 The drain and switching device of ( ) S 10 The drain electrode of ) Energy storage inductor three ( L 3 The other end of the device is electrically connected to the switching device six. S 6 The drain and switching device of 7 () S 7 The source of the switching device (six). S 6 The drain of () is grounded and electrically connected to filter capacitor two () C 2 One end of the filter capacitor is ( ), and the second filter capacitor is ( ) C 2 The other end of the device is electrically connected to the switching device seven. S 7 The source of the switch device (nine) S 9 The source and switching device of eleven ( S 11 The source pole of ) Switching device eight ( S 8 The source and switching device nine () S 9 The drain of the filter coupling inductor is connected to the drain of the filter. L 4a The same-name terminal of the switching device ( ) S 10 The source and switching device of eleven ( S 11 The drain of the filter coupling inductor is connected to the drain of the inductor. L 4b The opposite end of the filter coupling inductor; L 4a The different-named terminals of the filter capacitor are connected to the three ( C 3 One end of the AC port (3) and one end of the AC port (3); filter coupling inductor two ( L 4b The same terminal of the filter capacitor is connected to the three () C 3 The other end of ) and the other end of the communication port (3).

2. The non-isolated high-gain three-port converter with low leakage current characteristics as described in claim 1, characterized in that, The switching device one ( S 1 ) to switching device eleven ( S 11 () can be a MOSFET or an IGBT.

3. The non-isolated high-gain three-port converter with low leakage current characteristics as described in claim 1, characterized in that, The three-port converter operates symmetrically in the negative half-cycle and positive half-cycle modes of the output AC voltage.

4. A non-isolated high-gain three-port converter with low leakage current characteristics as described in any one of claims 1-3, characterized in that, When the output voltage 0 < v ac <( v dc1 - v dc2 When the three-port converter operates in buck mode one, the switching device one ( S 1) 、 Switching device three ( S 3 ), Switching devices eight ( S 8) Switching Device Nine ( S 9) Switching devices (+) S 10 ) and switching device eleven ( S 11 High-frequency operation, switching device two ( S 2 ), Switching Device Five ( S 5 ) and switching device seven ( S 7 ) is turned on, switching device four ( S 4) and switching device six ( S 6) Close; among which v ac The voltage at port (3) is the AC voltage. v dc The voltage at DC port 1 (1) v dc2 The voltage at DC port two (2); when( v dc1 - v dc2 )< v ac < v dc1 At this time, the three-port converter operates in buck mode two. In this mode, switching device one ( S 1) Switching device two ( S 2 ) and switching device three ( S 3 High-frequency operation, switching device four ( S 4) Switching device six ( S 6) Switching Device Nine ( S 9) and switching devices ( ) S 10 ) Close, switch device five ( S 5 ), Switching Devices VII S 7 ), Switching devices eight ( S 8) and switching device eleven ( S 11 ) Conduction; when v ac > v dc1 At this time, the three-port converter operates in boost mode, and the switching device one ( S 1 ) is turned on, switching device two ( S 2) Switching device three (S3), switching device four ( S 4), Switching Device Five ( S 5 ), Switching device six ( S 6) and switching device seven ( S 7 High-frequency operation; Among them, switching device one ( S 1) To switching device eleven ( S 11 The switching frequency during high-frequency operation is: f s The switching cycle is T s , f s and T s The relationship is T s =1 / f s ; When the three-port converter operates in buck mode 1 ， Switching device eight ( S 8) to switching device eleven ( S 11 When the three-port converter operates at high frequency and in a mode other than buck mode 1, the switching device 8 ( S 8) to switching device eleven ( S 11 Low-frequency operation, the switching frequency of low-frequency operation is... v ac frequency f o same.

5. The non-isolated high-gain three-port converter with low leakage current characteristics as described in claim 4, characterized in that, The voltage reduction mode includes mode 1 and mode 2; Mode 1: Switching device one of the three-port converter ( S 1) Switching device two ( S 2) Switching device five ( S 5) Switching Device Seven ( S 7) Switching device eight ( S 8) and switching device eleven ( S 11 ) is turned on, switching device three ( S 3) Switching device four ( S 4) Switching device six ( S 6) Switching Device Nine ( S 9) and switching devices ( ) S 10 ) Close, DC port one (1) via switching device one ( S 1) Switching device five ( S 5) and switching device seven ( S 7) To the energy storage inductor two ( L 2) and energy storage inductor three ( L 3) Charging, through switching device eight ( S 8) and switching device eleven ( S 11 Output to v ac Energy storage inductor one ( L 1) Switching device one ( S 1) and switching device two ( S 2) Charge DC port two (2), and at the same time filter capacitor one ( C 1 ), filter capacitor two ( C 2 DC port 1 (1) and AC port 3 pass through switching device 8 ( S 8) and switching device eleven ( S 11 ) form a charging and discharging circuit to exchange energy. At this time, the energy storage inductor ( L 1) Release energy, energy storage inductor two ( L 2) and energy storage inductor three ( L 3) Energy storage; Mode 2: Switching Device 1 ( S 1) Switching device four ( S 4) Switching device six ( S 6) Switching device eight ( S 8) and switching device eleven ( S 11 ) Close, switch device two ( S 2) Switching device three ( S 3) Switching device five ( S 5) Switching Device Seven ( S 7) Switching Device Nine ( S 9) and switching devices ( ) S 10 ) conduction, energy storage inductor two ( L 2) and energy storage inductor three ( L 3) Switching device two ( S 2) Switching device three ( S 3) Switching device five ( S 5) Switching Device Seven ( S 7) Switching Device Nine ( S 9) and switching devices ( ) S 10 ) transmits energy to the AC port (3), while the filter capacitor (1 ...). C 1 ), filter capacitor two ( C 2 DC port 1 (1) and AC port 3 are connected via switching device 9 ( S 9) and switching devices ( ) S 10 ) form a charging and discharging circuit to exchange energy. At this time, the energy storage inductor ( L 1) Energy storage, energy storage inductor two ( L 2) and energy storage inductor three ( L 3) Release energy.

6. The non-isolated high-gain three-port converter with low leakage current characteristics as described in claim 4, characterized in that, The second voltage reduction mode includes mode 3, mode 4 and mode 7; Mode 3: Switching Device Two ( S 2) Switching device five ( S 5) Switching Device Seven ( S 7) Switching device eight ( S 8) and switching device eleven ( S 11 ) is turned on, switching device one ( S 1) Switching device three ( S 3) Switching device four ( S 4) Switching device six ( S 6) Switching Device Nine ( S 9) and switching devices ( ) S 10 ) Close, DC port one (1) and DC port two (2) are connected via switching device two ( S 2) Switching device five ( S 5) and switching device seven ( S 7) To the energy storage inductor two ( L 2) and energy storage inductor three ( L 3) Charging, while simultaneously filtering capacitor one ( C 1 ), filter capacitor two ( C 2 DC port 1 (1) and AC port 3 are connected via switching device 8 ( S 8) and switching device eleven ( S 11 ) form a charging and discharging circuit to exchange energy. At this time, the energy storage inductor ( L 1) Energy storage, energy storage inductor two ( L 2) and energy storage inductor three ( L 3) Energy storage; Mode 4: Switching Device Two ( S 2) Switching device three ( S 3) Switching device five ( S 5) Switching Device Seven ( S 7) Switching device eight ( S 8) and switching device eleven ( S 11 ) is turned on, switching device one ( S 1) Switching device four ( S 4) Switching device six ( S 6) Switching Device Nine ( S 9) and switching devices ( ) S 10 ) Close, DC port one (1) is connected to the energy storage inductor one via DC port two (2). L 1) Charging, energy storage inductor two ( L 2) and energy storage inductor three ( L 3) Through switching device two ( S 2) Switching device three ( S 3) Switching device five ( S 5) Switching Device Seven ( S 7) Switching device eight ( S 8) and switching device eleven ( S 11 ) supplies power to the AC port voltage, and simultaneously filters capacitor one ( C 1) Filter capacitor two ( C 2) AC port (3) via switching device eight ( S 8) and switching device eleven ( S 11 ) form a charging and discharging circuit to exchange energy. At this time, the energy storage inductor ( L 1) Energy storage, energy storage inductor two ( L 2) and energy storage inductor three ( L 3) Release energy; Mode 7: Switching Device 1 ( S 1): Switching device two ( S 2) Switching device five ( S 5) Switching Device Seven ( S 7) Switching device eight ( S 8) and switching device eleven ( S 11 ) is turned on, switching device three ( S 3) Switching device four ( S 4) Switching device six ( S 6) Switching Device Nine ( S 9) and switching devices ( ) S 10 ) Close, DC port one (1) via switching device one ( S 1) Switching device five ( S 5) Switching Device Seven ( S 7) Switching device eight ( S 8) and switching device eleven ( S 11 ) supplies power to AC port (3) and simultaneously supplies power to energy storage inductor 2 ( L 2) and energy storage inductor three ( L 3) Charging, energy storage inductor one ( L 1) Through switching device one ( S 1) and switching device two ( S 2) Charge DC port two (2), and at the same time filter capacitor one ( C 1 ), filter capacitor two ( C 2 DC port 1 (1) and AC port 3 are connected via switching device 8 ( S 8) and switching device eleven ( S 11 ) form a charging and discharging circuit to exchange energy. At this time, the energy storage inductor ( L 1) Release energy, energy storage inductor two ( L 2) and energy storage inductor three ( L 3) Energy storage.

7. The non-isolated high-gain three-port converter with low leakage current characteristics as described in claim 4, characterized in that, The boost modes include mode 5 and mode 6; Mode 5: Switching Device 1 ( S 1) Switching device two ( S 2) Switching device four ( S 4) Switching device six ( S 6) Switching device eight ( S 8) and switching device eleven ( S 11 ) is turned on, switching device three (S3) and switching device five ( S 5) Switching Device Seven ( S 7) Switching device nine (S9) and switching device ten ( S 10 ) Close, DC port one (1) via switching device four ( S 4) and switching device six ( S 6) To the energy storage inductor two ( L 2) and energy storage inductor three ( L 3) Charging, energy storage inductor one ( L 1) Through switching device one ( S 1) and switching device two ( S 2) Charge DC port two (2), and at the same time filter capacitor one ( C 1) Filter capacitor two ( C 2) DC port one (1) and AC port (3) are connected by switching device nine ( S 9) and switching devices ( ) S 10 ) form a charging and discharging circuit to exchange energy. At this time, the energy storage inductor ( L 1) Release energy, energy storage inductor two ( L 2) Energy storage inductor three ( L 3) Energy storage; Mode 6: Off Device 1 ( S 1) Switching device three ( S 3) Switching device five ( S 5) Switching Device Seven ( S 7) Switching device eight ( S 8) and switching device eleven ( S 11 ) is turned on, switching device two ( S 2) Switching device four ( S 4) Switching device six ( S 6) Switching Device Nine ( S 9) and switching devices ( ) S 10 ) Close, DC port one (1) and energy storage inductor two ( L 2) and energy storage inductor three ( L 3) Switching device 1 ( S 1) Switching device five ( S 5) Switching Device Seven ( S 7) Switching device eight ( S 8) and switching device eleven ( S 11 Power is supplied to AC port (3), DC port one (1) via DC port two (2) and switching device three ( ) S 3) To the energy storage inductor ( L 1) Charging, while simultaneously filtering capacitor one ( C 1 ), filter capacitor two ( C 2 DC port 1 (1) and AC port 3 are connected via switching device 8 ( S 8) and switching device eleven ( S 11 ) form a charging and discharging circuit to exchange energy. At this time, the energy storage inductor ( L 1) Energy storage, energy storage inductor two ( L 2) and energy storage inductor three ( L 3) Release energy.

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