Low-voltage battery hybrid inverter topology system

Abstract

The invention provides a low-voltage battery hybrid inverter topology system, and belongs to the technical field of inverter topology. The low-voltage battery hybrid inverter topology system comprises a photovoltaic assembly, a low-voltage battery, an LLC circuit, a buck-boost circuit, an inverter circuit and a bus assembly. The low-voltage battery is connected to the bus assembly through the LLC circuit, only one-stage LLC circuit is used for charging and discharging of the low-voltage battery, the boost-buck circuit is used for replacing a boost circuit in an existing hybrid inverter topology to control the output power provided by the photovoltaic assembly for the bus assembly, the software and hardware cost is greatly reduced, and the system efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inverter topology, and particularly relates to a low-voltage battery hybrid inverter topology system. BACKGROUND

[0002] Referring to Figure 3 and Figure 4 , the existing hybrid inverter topology uses a BOOST circuit to supply power to the bus in photovoltaic, and the low-voltage battery can be charged and discharged through a BDC circuit. There are many kinds of BDC circuits, including isolated or non-isolated ones. Common ones include BUCK-BOOST circuit or LLC circuit, DAB circuit, etc. If the low-voltage battery adopts LLC circuit, it can realize high efficiency while being isolated. However, the voltage gain range of LLC circuit is relatively narrow, and the bus voltage can only allow a small change when LLC works. If the PV operating voltage is higher than the bus voltage, the BOOST circuit will be bypassed and unable to adjust the PV output power. Sometimes, a BDC is added to support the use requirement of higher open-circuit voltage of PV. SUMMARY

[0003] The present application aims at the deficiency of the prior art and provides a low-voltage battery hybrid inverter topology system.

[0004] The present application provides a low-voltage battery hybrid inverter topology system, which comprises a photovoltaic assembly, a low-voltage battery, an LLC circuit, a boost-buck circuit, an inverter circuit and a bus assembly. The input part of the LLC circuit is connected to the positive and negative poles of the low-voltage battery respectively, the output part of the LLC circuit is connected to the bus assembly, the inverter circuit is connected to the bus assembly, the input part of the boost-buck circuit is connected to the photovoltaic assembly, and the output part of the boost-buck circuit is connected to the bus assembly. The boost-buck circuit is used to control the output power provided by the photovoltaic assembly to the bus assembly.

[0005] Further, the bus assembly comprises a bus capacitor, the output part of the LLC circuit is connected to both ends of the bus capacitor, the inverter circuit is connected to both ends of the bus capacitor respectively, the photovoltaic assembly is connected to the input part of the boost-buck circuit, and the output part of the boost-buck circuit is connected to both ends of the bus capacitor respectively.

[0006] Further, the boost-buck circuit is a BUCK-BOOST circuit.

[0007] Further, the boost-buck circuit comprises a first switch, an inductor and a diode. The positive output end of the photovoltaic assembly is connected to one end of the first switch, the other end of the first switch is connected to one end of the inductor and the negative pole of the diode respectively, the positive pole of the diode is connected to one end of the bus capacitor, and the negative output end of the photovoltaic assembly and the other end of the inductor are connected to the other end of the bus capacitor respectively.

[0008] Further, the photovoltaic assembly is used to charge the inductor when the first switch is closed, and the inductor is used to discharge the bus capacitor when the first switch is opened.

[0009] Further, the first switch is a semiconductor switch.

[0010] Further, when the system meets the first preset condition, the duty cycle of the first switch is equal to the low-voltage battery voltage divided by the sum of the low-voltage battery voltage and the photovoltaic assembly voltage.

[0011] Further, a controller is further included, which controls the first switch to be closed or opened at a preset frequency, so that the bus voltage of the bus capacitor is a first preset value.

[0012] Further, a first connecting line, a second connecting line, a third connecting line and a fourth connecting line are further included, and the bus assembly further includes a first bus connected to one end of the bus capacitor and a second bus connected to the other end of the bus capacitor; the input part of the LLC circuit includes a first input end and a second input end, the output part of the LLC circuit includes a first output end and a second output end, one end of the first connecting line is connected to the positive electrode of the low-voltage battery, and the other end is connected to the first input end, one end of the second connecting line is connected to the negative electrode of the low-voltage battery, and the other end is connected to the first input end, one end of the third connecting line is connected to the first output end, and the other end is connected to the other end of the first bus, one end of the fourth connecting line is connected to the second output end, and the other end is connected to the other end of the second bus.

[0013] Further, the step-up and step-down circuit further includes a fifth connecting line, a sixth connecting line, a seventh connecting line, an eighth connecting line, a ninth connecting line and a tenth connecting line; one end of the fifth connecting line is connected to the negative output end of the photovoltaic assembly, and the other end is connected to the other end of the first bus, one end of the sixth connecting line is connected to the positive output end of the photovoltaic assembly, and the other end is connected to one end of the first switch, one end of the seventh connecting line is connected to the other end of the first switch, and the other end is connected to the negative electrode of the diode, one end of the eighth connecting line is connected to the positive electrode of the diode, and the other end is connected to the other end of the second bus, one end of the ninth connecting line is connected to one end of the inductor, and the other end is connected to the fifth connecting line, and one end of the tenth connecting line is connected to the other end of the inductor, and the other end is connected to the seventh connecting line.

[0014] The low-voltage battery hybrid inverter topology system has the following beneficial effects: The low-voltage battery is connected to the bus assembly through the LLC circuit, and the charging and discharging of the low-voltage battery only uses a first LLC circuit. The step-up and step-down circuit replaces the step-up circuit in the existing hybrid inverter topology to control the output power of the photovoltaic assembly provided to the bus assembly, greatly reducing the software and hardware costs and improving the system efficiency. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In these drawings, similar reference numerals are used to denote similar elements. The drawings described below are some embodiments of the invention, but not all embodiments. Other drawings will be readily available to those skilled in the art based on these drawings without any inventive effort.

[0016] Figure 1 This is a schematic block diagram of a low-voltage battery hybrid inverter topology system according to an embodiment of the present invention; Figure 2 This is a circuit diagram of a low-voltage battery hybrid inverter topology system according to an embodiment of the present invention; Figure 3 This is a first principle block diagram of the prior art; Figure 4 This is a second principle block diagram of the prior art. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0018] Please see Figures 1-2 An embodiment of the present invention provides a low-voltage battery hybrid inverter topology system, comprising a photovoltaic module, a low-voltage battery, an LLC circuit, a buck-boost circuit, an inverter circuit, and a bus assembly. The input of the LLC circuit is connected to the positive and negative terminals of the low-voltage battery, and the output of the LLC circuit is connected to the bus assembly. The inverter circuit is connected to the bus assembly. The input of the buck-boost circuit is connected to the photovoltaic module, and the output of the buck-boost circuit is connected to the bus assembly. The buck-boost circuit is used to control the output power provided by the photovoltaic module to the bus assembly.

[0019] Here, in the existing low-voltage battery hybrid inverter topology system, the low-voltage battery is either charged and discharged through the LLC circuit or charged and discharged through the LLC circuit and the BDC circuit. In the way of charging and discharging the low-voltage battery through the LLC circuit, since the LLC can only allow a small change when working, the corresponding photovoltaic module only supports low open-circuit voltage in this way. In the way of charging and discharging the low-voltage battery through the LLC circuit and the BDC circuit, a one-stage battery charging and discharging circuit is added on the basis of the LLC circuit to control the charging and discharging of the low-voltage battery. In this way, hardware and algorithm support are required, which increases the cost, reduces the efficiency, and makes the control complex. In the present application, while using only one-stage LLC circuit for charging and discharging the low-voltage battery, the boost-buck circuit is innovatively used to replace the traditional boost circuit to control the output power of the photovoltaic module to the bus module, which greatly reduces the hardware and software cost of the system and improves the system efficiency.

[0020] Specifically, referring to Figure 2 、 Figure 3 and Figure 4 , PV represents a photovoltaic module. The low-voltage battery: the voltage is generally below 48V, for example, the 12V lead-acid battery used in traditional fuel vehicles, mainly used for low-power device power supply.

[0021] The bus module can include a bus capacitor; the output of the LLC circuit is connected to the two ends of the bus capacitor respectively, and the inverter circuit is connected to the two ends of the bus capacitor respectively; the photovoltaic module is connected to the input of the boost-buck circuit, and the output of the boost-buck circuit is connected to the two ends of the bus capacitor respectively.

[0022] Specifically, the input of the inverter circuit is connected to the two ends of the bus capacitor respectively, and the output of the inverter circuit is connected to the power grid or the load.

[0023] The boost-buck circuit can be a BUCK-BOOST circuit.

[0024] Specifically, unlike the prior art which controls the output power of the photovoltaic module through the boost circuit, the present application controls the output power of the photovoltaic module through the boost-buck circuit without adding a one-stage battery charging and discharging circuit. Among them, the BUCK-BOOST circuit is only a typical form of the boost-buck circuit, and other boost-buck circuits can also replace the BUCK-BOOST circuit mentioned in the present application to achieve the effect of the present scheme.

[0025] Specifically, the low-voltage battery only needs an LLC circuit to charge and discharge, without the need to increase a BDC circuit, allowing the photovoltaic module to be configured at a higher open-circuit voltage to improve the economy of the system. Unlike the prior art, the photovoltaic module is discharged by a BUCK-BOOST circuit. When the photovoltaic module voltage is higher or lower than the bus voltage, the output power to the bus module can be controlled.

[0026] Specifically, the Buck-Boost circuit belongs to a boost-buck circuit, and its core function is to realize voltage regulation by a single circuit. The Buck-Boost circuit realizes voltage conversion through switch tube switching. When the input voltage is higher or lower than the output voltage, it runs in buck or boost mode, respectively, and only 6 components are needed to complete the buck-boost function. The circuit adjusts the output voltage by controlling the switching frequency and duty cycle, and is suitable for scenarios that require flexible voltage regulation. The efficiency of the Buck-Boost circuit and the mode: buck mode: when the input voltage is higher than the output voltage, the inductor stores energy to achieve buck; boost mode: when the input voltage is lower than the output voltage, the inductor stores energy to achieve boost; buck-boost mode: through dynamic adjustment of switching frequency and inductor current continuity to achieve bidirectional regulation.

[0027] The boost-buck circuit can include a first switch, an inductor, and a diode; the positive output end of the photovoltaic module is connected to one end of the first switch, the other end of the first switch is connected to one end of the inductor and the negative electrode of the diode, respectively, the positive electrode of the diode is connected to one end of the bus capacitor, and the negative output end of the photovoltaic module and the other end of the inductor are respectively connected to the other end of the bus capacitor.

[0028] The photovoltaic module is used to charge the inductor when the first switch is closed, and the inductor is used to discharge the bus capacitor when the first switch is opened.

[0029] The first switch can be a semiconductor switch.

[0030] Specifically, the semiconductor switch is a sensor made of physical, chemical and biological properties of semiconductor materials, mainly used for switch mode converters.

[0031] When the system meets the first preset condition, the duty cycle of the first switch can be equal to the low-voltage battery voltage divided by the sum of the low-voltage battery voltage and the photovoltaic module voltage.

[0032] Specifically, the system meeting the first preset condition can be system stability, so when the system is stable, the duty cycle of the semiconductor switch is: D=Vbat / (Vbat+Vpv), where Vbat represents the low-voltage battery voltage and Vpv represents the photovoltaic module voltage.

[0033] The low-voltage battery hybrid inverter topological system can further comprise a controller configured to control the first switch to be turned on or turned off at a preset frequency, so that the bus voltage of the bus capacitor is a first preset value.

[0034] Specifically, the low-voltage battery is connected to the bus capacitor through an LLC circuit, and the bus voltage is a fixed value. The photovoltaic module is connected to the bus capacitor through a BUCK-BOOST circuit, and the controller controls the first switch to be turned on or turned off in a fixed frequency mode. When the first switch is turned on, the photovoltaic module charges the inductor and stores energy. After the first switch is turned off, the inductor continues to flow to discharge the bus capacitor. The controller can be a PLC controller.

[0035] Specifically, the core mechanism of the BUCK-BOOST circuit for adjusting the output voltage by controlling the switching frequency and duty cycle is as follows: 1. Duty cycle adjusts output voltage: the output voltage is determined by the duty cycle of the switching signal. The specific relationship is: Vout=Vin*(D / 1-D), where D is the duty cycle. When the duty cycle D>50%, the voltage is boosted, and when the duty cycle D<50%, the voltage is reduced. For example, when the input voltage range is wide (such as 8V~16V) and the output voltage needs to be constant 12V, the target voltage can be maintained by adjusting the DD value in real time, which is not affected by input fluctuations; 2. Switching frequency affects ripple and efficiency: the switching frequency determines the charging and discharging speed of the inductor current: high-frequency switching reduces the size of the inductor and the value of the output capacitor, but increases the switching loss; low-frequency switching reduces the loss, but requires a larger inductor to suppress current ripple; the frequency itself does not change the average output voltage, but only optimizes the dynamic response and efficiency of the circuit; 3. Closed-loop control for voltage stabilization: the PWM controller continuously monitors the output voltage and dynamically adjusts the duty cycle to compensate for load changes. At the same time, combined with frequency tuning (such as fixed frequency / variable frequency mode), the efficiency and noise are balanced.

[0036] The low-voltage battery hybrid inverter topological system can further comprise a first connecting line, a second connecting line, a third connecting line, and a fourth connecting line. The bus assembly further comprises a first bus connected to one end of the bus capacitor and a second bus connected to the other end of the bus capacitor. The input part of the LLC circuit comprises a first input end and a second input end, and the output part of the LLC circuit comprises a first output end and a second output end. One end of the first connecting line is connected to the positive electrode of the low-voltage battery, and the other end is connected to the first input end. One end of the second connecting line is connected to the negative electrode of the low-voltage battery, and the other end is connected to the first input end. One end of the third connecting line is connected to the first output end, and the other end is connected to the other end of the first bus. One end of the fourth connecting line is connected to the second output end, and the other end is connected to the other end of the second bus.

[0037] The boost-buck circuit can further comprise a fifth connecting line, a sixth connecting line, a seventh connecting line, an eighth connecting line, a ninth connecting line and a tenth connecting line; one end of the fifth connecting line is connected to the negative output end of the photovoltaic module, and the other end of the fifth connecting line is connected to the other end of the first bus; one end of the sixth connecting line is connected to the positive output end of the photovoltaic module, and the other end of the sixth connecting line is connected to one end of the first switch; one end of the seventh connecting line is connected to the other end of the first switch, and the other end of the seventh connecting line is connected to the negative electrode of the diode; one end of the eighth connecting line is connected to the positive electrode of the diode, and the other end of the eighth connecting line is connected to the other end of the second bus; one end of the ninth connecting line is connected to one end of the inductor, and the other end of the ninth connecting line is connected to the fifth connecting line; and one end of the tenth connecting line is connected to the other end of the inductor, and the other end of the tenth connecting line is connected to the seventh connecting line.

[0038] Specifically, the input part of the inverter circuit comprises a third input end and a fourth input end, and the third input end and the fourth input end are respectively connected to two ends of the bus capacitor. The input part further comprises an eleventh connecting line and a twelfth connecting line, one end of the eleventh connecting line is connected to the third input end, and the other end of the eleventh connecting line is connected to the other end of the first bus; one end of the twelfth connecting line is connected to the fourth input end, and the other end of the twelfth connecting line is connected to the other end of the second bus. The other end of the third connecting line, one end of the fifth connecting line and one end of the ninth connecting line can be connected to the other end of the first bus, and the other end of the fourth connecting line and the other end of the eighth connecting line can be connected to the other end of the second bus.

[0039] Specifically, referring to Figure 2 , the low-voltage battery is connected to the bus capacitor through the LLC circuit, and the bus voltage is a fixed value. The photovoltaic module is connected to the bus capacitor through the BUCK-BOOST circuit. The first switch is controlled in a fixed frequency mode, when the first switch is turned on, the photovoltaic charges the inductor to store energy, and after the first switch is turned off, the inductor continues to flow to discharge the bus capacitor. When the system is stable, the duty cycle of the semiconductor switch is D=Vbat / (Vbat+Vpv), wherein Vbat represents the low-voltage battery voltage, and Vpv represents the photovoltaic module voltage.

[0040] The above-described content can be implemented alone or in various combinations, and these variants are within the protection scope of the present application.

[0041] It should be noted that in the description of the present application, the terms "upper end", "lower end", "bottom end" indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present application is usually placed, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device containing a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without further limitation, the element defined by the statement "includes one" does not exclude the presence of another identical element in the process, method, article or device that includes the element.

[0042] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit it. Although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A low voltage battery hybrid inverter topology system, characterized by: The application relates to a photovoltaic module, a low-voltage battery, an LLC circuit, a boost-buck circuit, an inverter circuit and a bus module, wherein the input of the LLC circuit is connected to the positive and negative poles of the low-voltage battery respectively, the output of the LLC circuit is connected to the bus module, the inverter circuit is connected to the bus module, the input of the boost-buck circuit is connected to the photovoltaic module, and the output of the boost-buck circuit is connected to the bus module; the boost-buck circuit is used to control the output power provided by the photovoltaic module to the bus module.

2. A low voltage battery hybrid inverter topology system as claimed in claim 1 characterized by: The bus module comprises a bus capacitor; the output of the LLC circuit is connected to the two ends of the bus capacitor respectively, and the inverter circuit is connected to the two ends of the bus capacitor respectively; the photovoltaic module is connected to the input of the boost-buck circuit, and the output of the boost-buck circuit is connected to the two ends of the bus capacitor respectively.

3. A low voltage battery hybrid inverter topology system as claimed in claim 2, wherein: The boost-buck circuit is a BUCK-BOOST circuit.

4. A low voltage battery hybrid inverter topology system as claimed in claim 2 or 3, characterized in that: The boost-buck circuit comprises a first switch, an inductor and a diode; the positive output end of the photovoltaic module is connected to one end of the first switch, the other end of the first switch is connected to one end of the inductor and the negative pole of the diode respectively, the positive pole of the diode is connected to one end of the bus capacitor, and the negative output end of the photovoltaic module and the other end of the inductor are connected to the other end of the bus capacitor respectively.

5. A low voltage battery hybrid inverter topology system as claimed in claim 4, wherein: The photovoltaic module is used to charge and store energy in the inductor when the first switch is closed, and the inductor is used to discharge the bus capacitor when the first switch is opened.

6. A low voltage battery hybrid inverter topology system as claimed in claim 4, wherein: The first switch is a semiconductor switch.

7. A low voltage battery hybrid inverter topology system as claimed in claim 5, wherein: When the system meets the first preset condition, the duty cycle of the first switch is equal to the voltage of the low-voltage battery divided by the sum of the voltage of the low-voltage battery and the voltage of the photovoltaic module.

8. A low voltage battery hybrid inverter topology system as claimed in claim 5, wherein: A controller is further comprised, which controls the first switch to be closed or opened at a preset frequency, so that the bus voltage of the bus capacitor is a first preset value.

9. A low voltage battery hybrid inverter topology system as claimed in claim 4, wherein: A first connecting line, a second connecting line, a third connecting line and a fourth connecting line are further comprised, and the bus module further comprises a first bus connected to one end of the bus capacitor and a second bus connected to the other end of the bus capacitor; the input of the LLC circuit comprises a first input end and a second input end, the output of the LLC circuit comprises a first output end and a second output end, one end of the first connecting line is connected to the positive pole of the low-voltage battery, and the other end is connected to the first input end; one end of the second connecting line is connected to the negative pole of the low-voltage battery, and the other end is connected to the first input end; one end of the third connecting line is connected to the first output end, and the other end is connected to the other end of the first bus; and one end of the fourth connecting line is connected to the second output end, and the other end is connected to the other end of the second bus.

10. A low voltage battery hybrid inverter topology system as claimed in claim 9, wherein: The voltage lifting and dropping circuit further comprises a fifth connecting line, a sixth connecting line, a seventh connecting line, an eighth connecting line, a ninth connecting line and a tenth connecting line; one end of the fifth connecting line is connected to the negative output end of the photovoltaic module, and the other end is connected to the other end of the first bus; one end of the sixth connecting line is connected to the positive output end of the photovoltaic module, and the other end is connected to one end of the first switch; one end of the seventh connecting line is connected to the other end of the first switch, and the other end is connected to the negative electrode of the diode; one end of the eighth connecting line is connected to the positive electrode of the diode, and the other end is connected to the other end of the second bus; one end of the ninth connecting line is connected to one end of the inductor, and the other end is connected to the fifth connecting line; and one end of the tenth connecting line is connected to the other end of the inductor, and the other end is connected to the seventh connecting line.

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