Single-phase independent multi-port independent adjustable photovoltaic inverter system and port control method thereof

Abstract

The invention relates to the field of power electronics, and discloses a single-phase independent multi-port independent adjustable photovoltaic inverter system and a port control method thereof.The inverter can integrate various single-phase independent port modules such as a photovoltaic array, a super capacitor, a battery energy storage unit and a battery system and comprises a first type of port module, a second type of port module, a third type of port module and a fourth type of port module, the first energy storage module comprises a first energy storage unit and a bidirectional power circuit, one end of the first energy storage unit is connected with the cathode of the photovoltaic array, and the other end is connected with the anode of the photovoltaic array through the bidirectional power circuit; the second type port module comprises a second energy storage unit and two power switches, one end of the second energy storage unit is connected with the negative electrode of the photovoltaic array, and the other end of the second energy storage unit is connected with the first bridge arm of the inverter bridge module of the inverter through one power switch and connected with the second bridge arm through the other power switch; the PWM controller independently controls the two types of port modules, so as to realize energy management of the multi-port inverter and reliable operation of the AC power supply system.

Description

Technical Field

[0001] The present invention relates to the field of power electronics, and in particular to a single-phase independent multi-port independently adjustable photovoltaic inverter system and a port control method thereof. Background Art

[0002] The application of distributed energy resources (DERs) can improve the utilization rate of renewable energy. At the same time, the combination of energy storage systems (ESS) and DERs can compensate for the intermittent nature of their power generation. At present, the common two-stage architecture system includes multiple single-input DC-DC converters connected in parallel to the DC bus and a DC-AC converter for the inverter stage. However, this multi-port inverter architecture requires more power devices, resulting in increased system complexity, increased switching energy consumption, and low efficiency, and increased volume and cost.

[0003] The disclosure of the above background technology content is only used to assist in understanding the concept and technical solution of the present application. It does not necessarily belong to the prior art of the present application, nor does it necessarily provide technical guidance. In the absence of clear evidence that the above content has been disclosed before the filing date of the present application, the above background technology should not be used to evaluate the novelty and creativity of the present application. Summary of the invention

[0004] The purpose of the present invention is to provide a multi-port independently adjustable inverter system, which integrates multiple power conversion ports into one inverter, simplifies the structure, improves efficiency, and reduces costs, providing an effective solution for the combination of distributed energy systems and energy storage systems.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: A single-phase independent multi-port independently adjustable photovoltaic inverter system is used to convert the DC power of a DC power supply into AC power. The photovoltaic inverter includes a PWM controller, a power port for connecting a DC power supply, and an inverter bridge module connected in parallel with the power port. The photovoltaic inverter also includes one or more of the following single-phase independent port modules: A first type port module, comprising a first energy storage unit and a bidirectional power circuit, wherein one end of the first energy storage unit is connected to the negative port of the power port, and the other end is connected to the positive port of the power port through the bidirectional power circuit; A second type port module, comprising a second energy storage unit and two power switches, wherein one end of the second energy storage unit is connected to the negative port of the power port, and the other end is connected to the first bridge arm of the inverter bridge module through one of the power switches and to the second bridge arm of the inverter bridge module through the other power switch; The PWM controller independently controls the first type port module and / or the second type port module.

[0006] Further, based on any one of the above technical solutions or a combination of multiple technical solutions, the bidirectional power circuit of the first type of port module includes two power switches connected in series, and the two power switches of the bidirectional power circuit are both provided with diodes in parallel; The series branches of the two power switches of the bidirectional power circuit are arranged in parallel at both ends of the positive and negative electrodes of the power port; Under the control of the PWM controller, the two power switches of the bidirectional power circuit are complementarily turned on.

[0007] Further, based on any one of the technical solutions or a combination of multiple technical solutions mentioned above, the first type port module also includes an inductor and a capacitor, and the capacitor is arranged in parallel at both ends of the first energy storage unit; the connection point between the two power switches of the bidirectional power circuit is connected to one end of the inductor, and the other end of the inductor is connected to the capacitor, and the inductor is not directly connected to the negative port of the power port.

[0008] Further, based on any one of the technical solutions or a combination of multiple technical solutions described above, the first energy storage unit in the first type port module is a supercapacitor, the inductance of the first type port module is a first inductance, and the capacitance of the first type port module is a first capacitance; The two power switches of the first type port module are a first power switch tube and a second power switch tube.

[0009] Further, based on any one of the above technical solutions or a combination of multiple technical solutions, the first energy storage unit in the first type port module is a battery energy storage unit, the inductance of the first type port module is a second inductance, and the capacitance of the first type port module is a second capacitance; The two power switches of the first type port module are a third power switch tube and a fourth power switch tube.

[0010] Further, based on any one of the above technical solutions or a combination of multiple technical solutions, the second energy storage unit of the second type port module is a battery system, and the two power switches of the second type port module are respectively a fifth power switch tube and a sixth power switch tube; The first bridge arm of the inverter bridge module is a series branch of the seventh power switch tube and the eighth power switch tube, and the second bridge arm is a series branch of the ninth power switch tube and the tenth power switch tube; Under the control of the PWM controller, the fifth power switch tube and the sixth power switch tube are complementarily switched on, the seventh power switch tube and the eighth power switch tube are complementarily switched on, and the ninth power switch tube and the tenth power switch tube are complementarily switched on.

[0011] Furthermore, based on any one of the technical solutions or a combination of multiple technical solutions described above, the second type port module also includes a third inductor and a third capacitor, and the third capacitor is arranged in parallel at both ends of the second energy storage unit; the connection point between the fifth power switch tube and the sixth power switch tube is connected to one end of the third inductor, and the other end of the third inductor is connected to the third capacitor, and the third inductor is not directly connected to the negative port of the power port.

[0012] Furthermore, based on any one of the technical solutions or a combination of multiple technical solutions described above, the photovoltaic inverter also includes a fourth capacitor and an LCL filter circuit, the fourth capacitor is connected in parallel at both ends of the inverter bridge module, and the inverter bridge module is configured to be connected to the AC side through the LCL filter circuit.

[0013] Further, based on any one of the technical solutions or a combination of multiple technical solutions mentioned above, different first-type port modules, different second-type port modules, or the first-type port modules and the second-type port modules have independent PWM control.

[0014] According to another aspect of the present invention, the present invention provides a port control method based on the above-mentioned single-phase independent multi-port independently adjustable photovoltaic inverter system, and the first type port module of the photovoltaic inverter is controlled by the following steps: Presetting a reference wave, and presetting a target pulse wave for the first energy storage unit of the first type port module; According to the reference wave and the pulse wave, pulses of two power switches in the bidirectional power circuit of the first type port module are determined.

[0015] Further, based on any one of the above-mentioned technical solutions or a combination of multiple technical solutions, when the target pulse wave is greater than the reference wave, the pulse of one of the two power switches connected to the DC bus is controlled to be a high-level signal, and the pulse of the other power switch is controlled to be a low-level signal; When the target pulse wave is smaller than the reference wave, the pulse of one of the two power switches connected to the DC bus is controlled to be a low level signal, and the pulse of the other power switch is controlled to be a high level signal.

[0016] Further, based on any one of the technical solutions or a combination of multiple technical solutions mentioned above, there are multiple first-type port modules, and a corresponding target pulse wave is independently preset for each first-type port module.

[0017] Further, based on any one of the above-mentioned technical solutions or a combination of multiple technical solutions, the second type port module of the photovoltaic inverter is controlled by the following steps: Collecting the current and voltage of the battery system and the current and voltage of the AC side connected to the output side of the photovoltaic inverter; According to the current and voltage of the battery system and the current, voltage, phase and frequency of the AC side, closed-loop PWM control is performed on the fifth power switch tube, the sixth power switch tube of the second type port module and the seventh power switch tube, the eighth power switch tube, the ninth power switch tube and the tenth power switch tube of the inverter bridge module.

[0018] Further, based on any one of the above-mentioned technical solutions or a combination of multiple technical solutions, the inverter bridge module is configured to be connected to the AC side through the LCL filter circuit; The port control method further includes: Collecting the inverter current at the input side of the LCL filter circuit; According to the inverter current on the input side of the LCL filter circuit, the current and voltage of the battery system, and the current, voltage, phase and frequency on the AC side, closed-loop PWM control is performed on the fifth power switch tube, the sixth power switch tube of the second type port module and the seventh power switch tube, the eighth power switch tube, the ninth power switch tube and the tenth power switch tube of the inverter bridge module.

[0019] The beneficial effects brought by the technical solution provided by the present invention are as follows: a. Provide a single-phase independent multi-port independently adjustable DC / AC inverter system that can integrate photovoltaic arrays, supercapacitors, battery energy storage units and battery systems to perform multi-port energy management and reliable operation of AC power systems; b. The single-phase independent multi-port inverter of the present invention reduces the use of power devices, reduces switching power loss and implementation costs compared to the traditional multi-port inverter architecture; c. The inverter system's multi-port power flow is independently regulated and can execute the maximum power point tracking (MPPT) algorithm on the photovoltaic array to improve the system's conversion efficiency and power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic diagram of a circuit topology of a single-phase independent multi-port independently adjustable photovoltaic inverter system provided by an exemplary embodiment of the present invention; Figure 2 A schematic diagram of generating a switch pulse for a first type port module provided by an exemplary embodiment of the present invention; Figure 3 for Figure 1 Schematic diagram of the charging current flow when the power switch tubes S2 and S4 are turned on and S1 and S3 are turned off in the topology circuit; Figure 4 for Figure 1 Schematic diagram of the discharge current flow when the power switch tubes S1 and S3 are turned on and S2 and S4 are turned off in the topology circuit; Figure 5 A schematic diagram of a closed-loop control hardware structure of a DC-DC controller of a first type port module provided by an exemplary embodiment of the present invention; Figure 6 A schematic diagram of the DC-AC current flow of the SSI subcircuit in the first switching state during charging of the second energy storage unit provided by an exemplary embodiment of the present invention; Figure 7 for Figure 6 Schematic diagram of DC-DC current flow of the SSI subcircuit in the first switching state; Figure 8 A schematic diagram of the DC-AC current flow of the SSI subcircuit in the second switching state during charging of the second energy storage unit provided by an exemplary embodiment of the present invention; Fig. 9 for Figure 8 Schematic diagram of the DC-DC current flow of the SSI sub-circuit in the second switching state; Fig.10 A schematic diagram of the DC-AC current flow of the SSI sub-circuit in the third switching state during charging of the second energy storage unit provided by an exemplary embodiment of the present invention; Fig.11 for Fig.10 Schematic diagram of DC-DC current flow of the SSI sub-circuit in the third switching state; Fig.12 A schematic diagram of the DC-AC current flow of the SSI sub-circuit in the fourth switching state during the charging of the second energy storage unit provided by an exemplary embodiment of the present invention; Fig.13 for Fig.12 A schematic diagram of the DC-DC current flow of the SSI sub-circuit in the fourth switching state; Fig.14A schematic diagram of the DC-AC current flow of the SSI subcircuit in the fifth switching state during charging of the second energy storage unit provided by an exemplary embodiment of the present invention; Fig.15 for Fig.14 Schematic diagram of DC-DC current flow of the SSI sub-circuit in the fifth switching state; Fig.16 A schematic diagram of the DC-AC current flow of the SSI sub-circuit in the sixth switching state during charging of the second energy storage unit provided by an exemplary embodiment of the present invention; Fig.17 for Fig.16 Schematic diagram of DC-DC current flow of the SSI sub-circuit in the sixth switching state; Fig.18 A schematic diagram of the closed-loop control hardware structure of a second type port module provided as an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. 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 creative work should fall within the scope of protection of the present invention.

[0023] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, device, product or equipment that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0024] In one embodiment of the present invention, a single-phase independent multi-port independently adjustable photovoltaic inverter system is provided for converting DC power of a DC power source into AC power, such as Figure 1As shown, the photovoltaic inverter includes a PWM (Pulse Width Modulation) controller, a power port for connecting a photovoltaic DC power source 100, and an inverter bridge module 200 connected in parallel with the power port. The photovoltaic inverter also includes one or more of the following single-phase independent port modules: directly connecting the photovoltaic array of the photovoltaic DC power source 100 to the DC bus, and implementing the MPPT (Maximum power point tracking) algorithm by adjusting the DC bus voltage; no additional power converter is required, thereby reducing the number of passive components and active switches, reducing switching power loss and implementation costs.

[0025] A first type port module includes a first energy storage unit and a bidirectional power circuit, wherein one end of the first energy storage unit is connected to the negative port of the power port, and the other end is connected to the positive port (i.e., the DC bus) of the power port through the bidirectional power circuit, wherein the bidirectional power circuit is used to regulate power flow to ensure the stability of the DC bus voltage.

[0026] The second type port module 600 includes a second energy storage unit and two power switches, wherein one end of the second energy storage unit is connected to the negative port of the power port, and the other end is connected to the first bridge arm of the inverter bridge module 200 through one of the power switches and to the second bridge arm of the inverter bridge module through the other power switch; The PWM controller controls the first type port module and / or the second type port module 600 independently.

[0027] like Figure 1 As shown, the first type of port module can be divided into a super capacitor port module 400 and a battery energy storage unit port module 500 according to the difference of the first energy storage unit: In the supercapacitor port module 400, the first energy storage unit is a supercapacitor, and the bidirectional power circuit includes a first power switch tube S1 and a second power switch tube S2 connected in series, both of which are provided with a freewheeling diode in parallel; the series branch of the first power switch tube S1 and the second power switch tube S2 is arranged in parallel at the positive and negative ends of the power port, specifically, the first power switch tube S1 is connected to the negative port of the power port, and the second power switch tube S2 is connected to the positive port (i.e., the DC bus) of the power port; under the control of the PWM controller, the first power switch tube S1 and the second power switch tube S2 are complementary selected. The supercapacitor port module 400 also includes a first inductor Lsc and a first capacitor Csc, which are adjusted by inductance and capacitance to achieve the required power flow; the first capacitor Csc is connected in parallel at both ends of the supercapacitor, the connection point between the first power switch tube S1 and the second power switch tube S2 is connected to one end of the first inductor Lsc, the other end of the first inductor Lsc is connected to the first capacitor Csc, and the first inductor Lsc is not directly connected to the negative port of the power port.

[0028] Similarly, in the battery energy storage unit port module 500, the first energy storage unit is a battery energy storage unit (BatteryBank), and the bidirectional power circuit includes a third power switch tube S3 and a fourth power switch tube S4 connected in series, both of which are provided with a freewheeling diode in parallel; the series branches of the third power switch tube S3 and the fourth power switch tube S4 are arranged in parallel at the positive and negative ends of the power port, specifically, the third power switch tube S3 is connected to the negative port of the power port, and the fourth power switch tube S4 is connected to the positive port (i.e., the DC bus) of the power port; under the control of the PWM controller, the third power switch tube S3 and the fourth power switch tube S4 are complementarily selected. The battery energy storage unit port module 500 also includes a second inductor L BAT and the second capacitor C BAT , adjusted by inductance and capacitance to achieve the required power flow; the second capacitor C BAT The two ends of the battery energy storage unit are connected in parallel, and the connection point between the third power switch tube S3 and the fourth power switch tube S4 is connected to the second inductor L BAT One end of the second inductor L BAT The other end of the second capacitor C BAT connected, and the second inductor L BAT Do not connect directly to the negative terminal of the power port.

[0029] Continue to see Figure 1 , the second energy storage unit of the second type port module 600 is a battery system (Battery), and the two power switches of the second type port module 600 are a fifth power switch tube S5 and a sixth power switch tube S6; The first bridge arm of the inverter bridge module 200 is a series branch of the seventh power switch tube S7 and the eighth power switch tube S8, and the second bridge arm is a series branch of the ninth power switch tube S9 and the tenth power switch tube S10; Under the control of the PWM controller, the fifth power switch tube S5 and the sixth power switch tube S6 are complementarily switched on, the seventh power switch tube S7 and the eighth power switch tube S8 are complementarily switched on, and the ninth power switch tube S9 and the tenth power switch tube S10 are complementarily switched on. The second type port module 600 further includes a third inductor L EV and the third capacitor C EV , the third capacitor C EV The connection point between the fifth power switch tube S5 and the sixth power switch tube S6 and the third inductor L EV One end of the third inductor L EV The other end of the third capacitor C EV connected, and the third inductor L EV Not directly connected to the negative terminal of the power port.

[0030] In addition, the photovoltaic inverter further includes a fourth capacitor C DC and the LCL filter circuit 300, the fourth capacitor C DC The inverter bridge module 200 is connected in parallel at both ends thereof. The inverter bridge module 200 uses an H-bridge circuit to output a sinusoidal AC signal. The output of the inverter bridge module 200 is connected to the AC side 700 through the LCL filter circuit 300 to reduce harmonics.

[0031] The present invention does not limit the first type of port module to include a supercapacitor port module 400 and a battery energy storage unit port module 500, nor does it limit the number of the second type of port modules 600 to one. The number of supercapacitor port modules 400 / battery energy storage unit port modules 500 can be zero or more, and the number of second type port modules 600 can also be zero or more. Different ports (such as different supercapacitor port modules 400, different battery energy storage unit port modules 500, different second type port modules 600, supercapacitor port module 400 and battery energy storage unit port module 500, supercapacitor port module 400 and second type port module 600, battery energy storage unit port module 500 and second type port module 600) have independent PWM control.

[0032] The method for controlling the first type port module of the photovoltaic inverter is shown in Figure 2-4 and Fig.17 : A reference wave is preset, and a target pulse wave is preset for the first energy storage unit of the first type port module: Figure 2 As shown, taking the triangle wave as an example as the reference wave, the square wave with serial number ① is the target pulse wave of the supercapacitor, and the square wave with serial number ② is the target pulse wave of the battery energy storage unit. According to the reference wave and the target pulse wave with serial number ①, the switching pulses of the first power switch tube S1 and the second power switch tube S2 are determined: Figure 2 As shown, in the stage where the target pulse wave with serial number ① is higher than the reference wave, the enable signal of the second power switch tube S2 connected to the DC bus is high, and the enable signal of the first power switch tube S1 is low; in the stage where the target pulse wave with serial number ① is lower than the reference wave, the enable signal of the second power switch tube S2 is low, and the enable signal of the first power switch tube S1 is high.

[0033] Similarly, according to the reference wave and the target pulse wave with sequence number ②, the switching pulses of the third power switch tube S3 and the fourth power switch tube S4 are determined: Figure 2 As shown, in the stage where the target pulse wave with serial number ② is higher than the reference wave, the enable signal of the fourth power switch tube S4 connected to the DC bus is high, and the enable signal of the third power switch tube S3 is low; in the stage where the target pulse wave with serial number ② is lower than the reference wave, the enable signal of the fourth power switch tube S4 is low, and the enable signal of the third power switch tube S3 is high.

[0034] like Figure 2 As shown, the target pulse waves corresponding to the supercapacitor port module 400 and the battery energy storage unit port module 500 are set independently; when there are multiple supercapacitor port modules 400, the target pulse waves corresponding to each supercapacitor port module 400 are also set independently; when there are multiple battery energy storage unit port modules 500, the target pulse waves corresponding to each battery energy storage unit port module 500 are also set independently.

[0035] When the second power switch tube S2 is turned on and the first power switch tube S1 is turned off, the supercapacitor is in a charging state; similarly, when the fourth power switch tube S4 is turned on and the third power switch tube S3 is turned off, the battery energy storage unit is in a charging state; the charging current paths in both charging states are as follows: Figure 3 shown.

[0036] When the first power switch tube S1 is turned on and the second power switch tube S2 is turned off, the supercapacitor is in a discharging state; similarly, when the third power switch tube S3 is turned on and the fourth power switch tube S4 is turned off, the battery energy storage unit is in a discharging state; the discharge current path in both discharge states is as follows: Figure 4 shown.

[0037] The hardware structure for PWM control of the first type port module is as follows: Figure 5 As shown, where P * sc is the reference power point of the supercapacitor array, Vsc is the voltage of the supercapacitor array, and the two can be used to calculate I * sc is the reference array current of the supercapacitor, Isc is the supercapacitor array current, and the PI controller is based on I * sc and Isc, generate a target pulse wave corresponding to the supercapacitor port module 400, compare it with the reference wave, if the target pulse wave is greater than or equal to the reference wave, control the second power switch tube S2 to turn on, otherwise control the first power switch tube S1 to turn on.

[0038] V DC is the DC bus voltage, V * DC is the DC bus reference voltage, and the PI controller can calculate I * BAT That is, the reference current of the battery energy storage unit, and another PI controller is based on I * BAT and I BAT That is, the current of the battery energy storage unit generates a target pulse wave corresponding to the battery energy storage unit port module 500, which is compared with the reference wave. If the target pulse wave is greater than or equal to the reference wave, the fourth power switch tube S4 is controlled to be turned on, otherwise the third power switch tube S3 is controlled to be turned on.

[0039] The second type of port module of the photovoltaic inverter adopts closed-loop control, such as Fig.18 As shown in the figure, PRController is a proportional resonant controller, PI Controller is a proportional integral controller, MSPWM is a signal generator for generating multiple SPWM (Sinusoidal Pulse Width Modulation) signals, PWMBridge is a PWM controller for the inverter bridge module, PWM EV port is a PWM controller for the battery system port, and Single-phase SSI (Split-source inverter) is Figure 1 The second type port module 600 and the inverter bridge module 200 in the topological structure, the LCL Filter is Figure 1 In the topology of the LCL filter circuit 300, ACLOAD is Figure 1 The AC side of the topology 700. This embodiment adopts a closed-loop real-time control scheme to achieve independent regulation of power flow at each port and can perform a maximum power point tracking (MPPT) algorithm on the photovoltaic array without the need for an additional DC-DC converter.

[0040] Fig.18 The physical meanings of the signals in are as follows: V load is the terminal voltage on the AC side, I load is the current on the AC side, I inv is the inverter current on the input side of the LCL filter circuit, P * EV is the reference power point of the battery system, V EV is the voltage of the battery system, according to P * EV and V EV It can be calculated that I * EV This is the reference current of the battery system. The PI controller is based on I * EV and I EV That is, the current of the battery system, and the regulation index Mdc is calculated; V * αβ As the reference voltage signal, MSPWM * αβ Generate V * αβm That is, the reference voltage value, according to the adjustment index output by the PI controller and V * αβm Generate V * αβref That is, the reference voltage modulation signal, PWM Bridge modulates the signal V according to the reference voltage * αβref Generate PWM control signals for the seventh power switch tube S7 to the tenth power switch tube S10; PWM EV port generates PWM control signals for the fifth power switch tube S5 and the sixth power switch tube S6 according to the pulse signal generated by MSPWM.

[0041] In a specific embodiment, the seventh power switch tube S7 on the first bridge arm is connected to the DC bus, the ninth power switch tube S9 on the second bridge arm is connected to the DC bus, the connection point between the seventh power switch tube S7 and the eighth power switch tube S8 is connected to the sixth power switch tube S6, and the connection point between the ninth power switch tube S9 and the tenth power switch tube S10 is connected to the fifth power switch tube S5. The power tube switch state of the SSI circuit during charging of the battery system is as follows: Figures 6 to 17 : The first state see Figure 6 and Figure 7: Control the fifth power switch tube S5, the eighth power switch tube S8 and the tenth power switch tube S10 to be turned on, while the sixth power switch tube S6, the seventh power switch tube S7 and the ninth power switch tube S9 are turned off. In this state, the current path of the DC-AC conversion is as follows Figure 6 As shown, the current path of DC-DC conversion is as follows Figure 7 As shown, bidirectional power flow of the battery system port is realized; The second state see Figure 8 and Fig. 9 : Control the fifth power switch tube S5, the seventh power switch tube S7 and the ninth power switch tube S9 to be turned on, while the sixth power switch tube S6, the eighth power switch tube S8 and the tenth power switch tube S10 are turned off. In this state, the current path of the DC-AC conversion is as follows Figure 8 As shown, the current path of DC-DC conversion is as follows Fig. 9 As shown, bidirectional power flow of the battery system port is realized; The third state see Fig.10 and Fig.11 : Control the fifth power switch tube S5, the seventh power switch tube S7 and the tenth power switch tube S10 to be turned on, while the sixth power switch tube S6, the eighth power switch tube S8 and the ninth power switch tube S9 are turned off. In this state, the current path of the DC-AC conversion is as follows Fig.10 As shown, the current path of DC-DC conversion is as follows Fig.11 As shown, bidirectional power flow of the battery system port is realized; The fourth state see Fig.12 and Fig.13 : Control the sixth power switch tube S6, the eighth power switch tube S8 and the tenth power switch tube S10 to be turned on, while the fifth power switch tube S5, the seventh power switch tube S7 and the ninth power switch tube S9 are turned off. In this state, the current path of the DC-AC conversion is as follows Fig.12 As shown, the current path of DC-DC conversion is as follows Fig.13 As shown, bidirectional power flow of the battery system port is realized; The fifth state see Fig.14 and Fig.15 : Control the sixth power switch tube S6, the seventh power switch tube S7 and the ninth power switch tube S9 to be turned on, while the fifth power switch tube S5, the eighth power switch tube S8 and the tenth power switch tube S10 are turned off. In this state, the current path of the DC-AC conversion is as follows Fig.14 As shown, the current path of DC-DC conversion is as follows Fig.15 As shown, bidirectional power flow of the battery system port is realized; The sixth state see Fig.16 and Fig.17: Control the sixth power switch tube S6, the eighth power switch tube S8 and the ninth power switch tube S9 to be turned on, while the fifth power switch tube S5, the seventh power switch tube S7 and the tenth power switch tube S10 are turned off. In this state, the current path of the DC-AC conversion is as follows Fig.16 As shown, the current path of DC-DC conversion is as follows Fig.17 As shown, bidirectional power flow is achieved at the battery system port.

[0042] The present invention provides a high-efficiency, low-cost multi-port inverter, which integrates multiple power conversion ports into one inverter, significantly simplifies the structure, improves efficiency, and reduces costs, providing an effective solution for the combination of distributed energy systems and energy storage systems.

[0043] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0044] The above is only a specific implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A single-phase independent multi-port independently adjustable photovoltaic inverter system, used to convert the DC power of a DC power supply into AC power, the photovoltaic inverter includes a PWM controller, a power port for connecting a DC power supply, and an inverter bridge module connected in parallel with the power port, characterized in that: The photovoltaic inverter further includes one or more of the following single-phase independent port modules: A first type port module, comprising a first energy storage unit and a bidirectional power circuit, wherein one end of the first energy storage unit is connected to the negative port of the power port, and the other end is connected to the positive port of the power port through the bidirectional power circuit; A second type port module, comprising a second energy storage unit and two power switches, wherein one end of the second energy storage unit is connected to the negative port of the power port, and the other end is connected to the first bridge arm of the inverter bridge module through one of the power switches and to the second bridge arm of the inverter bridge module through the other power switch; The PWM controller independently controls the first type port module and / or the second type port module.

2. The single-phase independent multi-port independently adjustable photovoltaic inverter system according to claim 1 is characterized in that: The bidirectional power circuit of the first type port module comprises two power switches connected in series, and both power switches of the bidirectional power circuit are provided with a diode in parallel; The series branches of the two power switches of the bidirectional power circuit are arranged in parallel at both ends of the positive and negative electrodes of the power port; Under the control of the PWM controller, the two power switches of the bidirectional power circuit are complementarily turned on.

3. The single-phase independent multi-port independently adjustable photovoltaic inverter system according to claim 2 is characterized in that: The first type port module also includes an inductor and a capacitor, and the capacitor is arranged in parallel at both ends of the first energy storage unit; the connection point between the two power switches of the bidirectional power circuit is connected to one end of the inductor, and the other end of the inductor is connected to the capacitor, and the inductor is not directly connected to the negative port of the power port.

4. The single-phase independent multi-port independently adjustable photovoltaic inverter system according to claim 2 is characterized in that: The first energy storage unit in the first type port module is a supercapacitor, the inductance of the first type port module is a first inductance, and the capacitance of the first type port module is a first capacitance; The two power switches of the first type port module are a first power switch tube and a second power switch tube.

5. The single-phase independent multi-port independently adjustable photovoltaic inverter system according to claim 2, characterized in that: The first energy storage unit in the first type port module is a battery energy storage unit, the inductance of the first type port module is a second inductance, and the capacitance of the first type port module is a second capacitance; The two power switches of the first type port module are a third power switch tube and a fourth power switch tube.

6. The single-phase independent multi-port independently adjustable photovoltaic inverter system according to claim 1, characterized in that: The second energy storage unit of the second type port module is a battery system, and the two power switches of the second type port module are respectively a fifth power switch tube and a sixth power switch tube; The first bridge arm of the inverter bridge module is a series branch of the seventh power switch tube and the eighth power switch tube, and the second bridge arm is a series branch of the ninth power switch tube and the tenth power switch tube; Under the control of the PWM controller, the fifth power switch tube and the sixth power switch tube are complementarily switched on, the seventh power switch tube and the eighth power switch tube are complementarily switched on, and the ninth power switch tube and the tenth power switch tube are complementarily switched on.

7. The single-phase independent multi-port independently adjustable photovoltaic inverter system according to claim 6, characterized in that: The second type port module also includes a third inductor and a third capacitor, and the third capacitor is arranged in parallel at both ends of the second energy storage unit; the connection point between the fifth power switch tube and the sixth power switch tube is connected to one end of the third inductor, and the other end of the third inductor is connected to the third capacitor, and the third inductor is not directly connected to the negative port of the power port.

8. The single-phase independent multi-port independently adjustable photovoltaic inverter system according to claim 1, characterized in that: The photovoltaic inverter further includes a fourth capacitor and an LCL filter circuit. The fourth capacitor is connected in parallel at both ends of the inverter bridge module. The inverter bridge module is configured to be connected to the AC side through the LCL filter circuit.

9. The single-phase independent multi-port independently adjustable photovoltaic inverter system according to any one of claims 1 to 8, characterized in that: Different first-type port modules, different second-type port modules, or the first-type port module and the second-type port module have independent PWM control.

10. A port control method based on a single-phase independent multi-port independently adjustable photovoltaic inverter system according to any one of claims 2 to 5, characterized in that: The first type port module of the photovoltaic inverter is controlled by the following steps: Presetting a reference wave, and presetting a target pulse wave for the first energy storage unit of the first type port module; According to the reference wave and the pulse wave, pulses of two power switches in the bidirectional power circuit of the first type port module are determined.

11. The port control method according to claim 10, characterized in that: When the target pulse wave is greater than the reference wave, the pulse of one of the two power switches connected to the DC bus is controlled to be a high level signal, and the pulse of the other power switch is controlled to be a low level signal; When the target pulse wave is smaller than the reference wave, the pulse of one of the two power switches connected to the DC bus is controlled to be a low level signal, and the pulse of the other power switch is controlled to be a high level signal.

12. The port control method according to claim 10 or 11, characterized in that: There are multiple first-type port modules, and a corresponding target pulse wave is independently preset for each first-type port module.

13. A port control method based on the single-phase independent multi-port independently adjustable photovoltaic inverter system according to claim 6 or 7, characterized in that: The second type port module of the photovoltaic inverter is controlled by the following steps: Collecting the current and voltage of the battery system and the current, voltage, phase and frequency of the AC side connected to the output side of the photovoltaic inverter; According to the current and voltage of the battery system and the current, voltage, phase and frequency of the AC side, closed-loop PWM control is performed on the fifth power switch tube, the sixth power switch tube of the second type port module and the seventh power switch tube, the eighth power switch tube, the ninth power switch tube and the tenth power switch tube of the inverter bridge module.

14. The port control method according to claim 13, characterized in that: The inverter bridge module is configured to be connected to the AC side through the LCL filter circuit; The port control method further includes: Collecting the inverter current at the input side of the LCL filter circuit; According to the inverter current on the input side of the LCL filter circuit, the current and voltage of the battery system, and the current, voltage, phase and frequency on the AC side, closed-loop PWM control is performed on the fifth power switch tube, the sixth power switch tube of the second type port module and the seventh power switch tube, the eighth power switch tube, the ninth power switch tube and the tenth power switch tube of the inverter bridge module.

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