CN102088252B - Inverter without transformer realized by switched capacitor and applications of inverter - Google Patents
Inverter without transformer realized by switched capacitor and applications of inverter Download PDFInfo
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- 239000003990 capacitor Substances 0.000 title claims abstract description 62
- 238000010248 power generation Methods 0.000 claims abstract description 8
- 239000004065 semiconductor Substances 0.000 claims description 5
- 230000005669 field effect Effects 0.000 claims description 4
- 229910044991 metal oxide Inorganic materials 0.000 claims description 4
- 150000004706 metal oxides Chemical class 0.000 claims description 4
- 230000007935 neutral effect Effects 0.000 claims description 3
- 230000000295 complement effect Effects 0.000 description 8
- 238000000034 method Methods 0.000 description 8
- 238000010586 diagram Methods 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 3
- 230000001360 synchronised effect Effects 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 230000001965 increasing effect Effects 0.000 description 2
- 230000001939 inductive effect Effects 0.000 description 2
- 230000003071 parasitic effect Effects 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
- H02M7/42—Conversion of DC power input into AC power output without possibility of reversal
- H02M7/44—Conversion of DC power input into AC power output without possibility of reversal by static converters
- H02M7/48—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
- H02M7/42—Conversion of DC power input into AC power output without possibility of reversal
- H02M7/44—Conversion of DC power input into AC power output without possibility of reversal by static converters
- H02M7/48—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
- H02M7/4837—Flying capacitor converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0095—Hybrid converter topologies, e.g. NPC mixed with flying capacitor, thyristor converter mixed with MMC or charge pump mixed with buck
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
- H02M7/42—Conversion of DC power input into AC power output without possibility of reversal
- H02M7/44—Conversion of DC power input into AC power output without possibility of reversal by static converters
- H02M7/48—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
- H02M7/5388—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with asymmetrical configuration of switches
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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Abstract
本发明公开了一种开关电容实现无变压器型逆变器，包括：二个电容，五个功率开关和滤波器；第一电容的二端分别与第一功率开关的漏极、滤波器的第二输入端相连；第一功率开关的源极与第二功率开关的漏极、第二电容的第一端和第四功率开关的漏极相连，第二功率开关的源极与第一电容的第二端和第三功率开关的漏极相连，第三功率开关的源极与第二电容的第二端和第五功率开关的源极相连，第五功率开关的漏极与第四功率开关的源极和滤波器的第一输入端相连。本发明还公开了其在光伏并网发电系统中的应用，本发明的逆变器结构简单，能够有效抑制无变压器型光伏并网系统中的对地漏电流。
The invention discloses a switched capacitor to realize a transformerless inverter, which comprises: two capacitors, five power switches and a filter; the two terminals of the first capacitor are respectively connected with the drain of the first power switch and the second The two input terminals are connected; the source of the first power switch is connected to the drain of the second power switch, the first terminal of the second capacitor is connected to the drain of the fourth power switch, and the source of the second power switch is connected to the drain of the first capacitor. The second end is connected to the drain of the third power switch, the source of the third power switch is connected to the second end of the second capacitor and the source of the fifth power switch, and the drain of the fifth power switch is connected to the fourth power switch The source of the filter is connected to the first input terminal of the filter. The invention also discloses its application in a photovoltaic grid-connected power generation system. The inverter of the invention has a simple structure and can effectively suppress the ground leakage current in a transformerless photovoltaic grid-connected system.
Description
技术领域 technical field
本发明涉及电力电子技术直流-交流变换器领域，具体说，涉及一种无变压器型逆变器及其在光伏并网发电系统中的应用。The invention relates to the field of DC-AC converters of power electronics technology, in particular to a transformerless inverter and its application in photovoltaic grid-connected power generation systems.
背景技术 Background technique
近年来，能源的短缺和环境的污染已经成为世界的焦点，可再生能源的发展和应用受到世界各国的广泛关注。太阳能清洁、广泛并且储量巨大，是较为理想的可再生能源之一。In recent years, energy shortage and environmental pollution have become the focus of the world, and the development and application of renewable energy have attracted widespread attention from all over the world. Solar energy is clean, extensive and has huge reserves, which is one of the ideal renewable energy sources.
光伏并网发电是利用太阳能的重要形式之一。光伏电池产生的直流电经逆变器转换成交流电后输送给电网。根据逆变器中变压器的配置不同，可将其分为带工频变压器型、带高频变压器型和无变压器型。工频变压器体积庞大，成本高，安装不方便。高频变压器尽管体积和重量大大减小，但往往需要增加一级功率变换器，导致系统复杂度提高，效率降低。无变压器型逆变器由于其系统结构简单，效率高，体积小，成本低等优点，在世界范围内得到了快速的发展。Photovoltaic grid-connected power generation is one of the important forms of utilizing solar energy. The direct current generated by the photovoltaic cell is converted into alternating current by the inverter and sent to the grid. According to the configuration of the transformer in the inverter, it can be divided into a type with power frequency transformer, a type with high frequency transformer and a type without transformer. Power frequency transformers are bulky, costly and inconvenient to install. Although the size and weight of high-frequency transformers are greatly reduced, it often requires an additional stage of power converter, resulting in increased system complexity and reduced efficiency. Due to its simple system structure, high efficiency, small size, and low cost, the transformerless inverter has been rapidly developed in the world.
然而，在无变压器型光伏并网发电系统中，光伏电池与大地之间存在不可避免的寄生电容，可能导致对地漏电流出现。对地漏电流将降低电能质量，并可能引起电磁兼容和安全问题，因此需要得到抑制。However, in the transformerless photovoltaic grid-connected power generation system, there is an inevitable parasitic capacitance between the photovoltaic cell and the ground, which may cause leakage current to the ground. Ground leakage currents will degrade power quality and may cause EMC and safety issues, so they need to be suppressed.
当前，一般采用双极性调制的全桥逆变器和半桥逆变器来解决共模电流问题。但是这两种解决方案各有其不足之处。双极性调制的全桥逆变器输出电压为两电平，需要较大的输出滤波电感以抑制开关纹波，从而增加了系统的体积、成本和损耗。半桥电路要求其直流侧输入电压的大小是全桥逆变器的两倍，相应增加了前级直流输入源串联的数量或者提高了前级DC/DC升压电路的升压比例以及设计难度。Currently, full-bridge inverters and half-bridge inverters with bipolar modulation are generally used to solve the common-mode current problem. But both solutions have their drawbacks. The output voltage of the full-bridge inverter with bipolar modulation is two levels, and a large output filter inductor is required to suppress the switching ripple, thus increasing the size, cost and loss of the system. The half-bridge circuit requires its DC side input voltage to be twice that of the full-bridge inverter, which increases the number of DC input sources connected in series or increases the boost ratio and design difficulty of the previous DC/DC boost circuit. .
发明内容 Contents of the invention
本发明提供一种结构简单、能够有效抑制无变压器型光伏并网系统中的对地漏电流、需要的直流输入电压与全桥逆变器相同并且支持三电平输出的开关电容实现无变压器型逆变器以及该开关电容实现无变压器型逆变器在光伏并网发电系统中的应用。The invention provides a switched capacitor with simple structure, capable of effectively suppressing the ground leakage current in a transformerless photovoltaic grid-connected system, requiring the same DC input voltage as a full-bridge inverter, and supporting three-level output to realize a transformerless inverter. The transformer and the switched capacitor realize the application of the transformerless inverter in the photovoltaic grid-connected power generation system.
一种开关电容实现无变压器型逆变器，其内部电路包括：第一电容，第二电容，第一功率开关，第二功率开关，第三功率开关，第四功率开关，第五功率开关和滤波器；第一电容的第一端与第一功率开关的的漏极相连，第一功率开关的的源极与第二功率开关的漏极、第二电容的第一端和第四功率开关的漏极相连，第二功率开关的源极与第一电容的第二端和第三功率开关的漏极相连，第三功率开关的源极与第二电容的第二端和第五功率开关的源极相连，第五功率开关的漏极与第四功率开关的源极相连，第五功率开关的漏极与滤波器的第一输入端相连，第一电容的第二端与滤波器的第二输入端相连。A switched capacitor realizes a transformerless inverter, and its internal circuit includes: a first capacitor, a second capacitor, a first power switch, a second power switch, a third power switch, a fourth power switch, a fifth power switch and Filter; the first end of the first capacitor is connected to the drain of the first power switch, the source of the first power switch is connected to the drain of the second power switch, the first end of the second capacitor is connected to the fourth power switch The drain of the second power switch is connected to the second end of the first capacitor and the drain of the third power switch, the source of the third power switch is connected to the second end of the second capacitor and the fifth power switch connected to the source of the fifth power switch, the drain of the fifth power switch is connected to the source of the fourth power switch, the drain of the fifth power switch is connected to the first input terminal of the filter, and the second terminal of the first capacitor is connected to the connected to the second input.
所述的滤波器为电感型滤波器、电感-电容型滤波器或电感-电容-电感型滤波器。The filter is an inductance filter, an inductance-capacitance filter or an inductance-capacitance-inductance filter.
所述功率开关由独立功率晶体管和独立二极管反并联后构成，或由其内部自带反并二极管的功率晶体管构成。The power switch is composed of an independent power transistor and an independent diode connected in antiparallel, or a power transistor with an internal antiparallel diode.
所述的功率晶体管为功率金属氧化物半导体场效应晶体管、绝缘栅双极晶体管或其他全控型功率半导体器件。The power transistor is a power metal oxide semiconductor field effect transistor, an insulated gate bipolar transistor or other fully controlled power semiconductor devices.
本发明的开关电容实现无变压器型逆变器具有两种调制方式：单极性脉冲宽度调制和倍频式脉冲宽度调制。The switched capacitor realized transformerless inverter of the present invention has two modulation modes: unipolar pulse width modulation and frequency multiplication pulse width modulation.
采用单极性脉冲宽度调制方式时，当工频(例如50Hz)调制波处于正半周期时，第一功率开关和第三功率开关导通，第二功率开关关断，第四功率开关和第五功率开关做互补的高频开关动作；当工频调制波处于负半周期时，第四功率开关关断，第五功率开关导通，第一功率开关和第三功率开关做同步的高频开关动作，第一功率开关和第二功率开关做互补的高频开关动作。When using unipolar pulse width modulation, when the power frequency (for example, 50Hz) modulation wave is in the positive half cycle, the first power switch and the third power switch are turned on, the second power switch is turned off, the fourth power switch and the The five power switches perform complementary high-frequency switching actions; when the power frequency modulation wave is in the negative half cycle, the fourth power switch is turned off, the fifth power switch is turned on, and the first power switch and the third power switch perform synchronous high-frequency Switching action, the first power switch and the second power switch perform complementary high-frequency switching action.
采用倍频式脉冲宽度调制方式时，第一功率开关、第二功率开关、第三功率开关、第四功率开关和第五功率开关均以高频周期进行开关动作，但第一功率开关、第二功率开关和第三功率开关的工频调制波与第四功率开关和第五功率开关的工频调制波相位相反。When frequency multiplication pulse width modulation is used, the first power switch, the second power switch, the third power switch, the fourth power switch and the fifth power switch all perform switching actions at high frequency cycles, but the first power switch, the second power switch The power frequency modulation waves of the second power switch and the third power switch are opposite in phase to the power frequency modulation waves of the fourth power switch and the fifth power switch.
不论采用上述任何一种调制方式，所有功率开关的控制信号都满足以下关系：第一功率开关和第三功率开关的控制信号时序相同，第一功率开关和第二功率开关的控制信号时序互补并有共同关断的死区时间，第四功率开关和第五功率开关的控制信号时序互补并有共同关断的死区时间。Regardless of any of the above-mentioned modulation methods, the control signals of all power switches satisfy the following relationship: the control signal timings of the first power switch and the third power switch are the same, and the timing sequences of the control signals of the first power switch and the second power switch are complementary and parallel. There is a common turn-off dead time, and the timing sequences of the control signals of the fourth power switch and the fifth power switch are complementary and have a common turn-off dead time.
所述的单极性脉冲宽度调制方式使逆变器能够输出三电平，从而减小滤波电感；所述的倍频式脉冲宽度调制方式可在所述的单极性脉冲宽度调制方式基础上在单个功率开关的工作频率不变的前提下将逆变器输出电压的等效开关频率提高一倍，从而使得输出电感进一步减小，进而降低成本，减小体积和重量并减少滤波电感上产生的铜损和磁损。The unipolar pulse width modulation method enables the inverter to output three levels, thereby reducing the filter inductance; the frequency multiplication pulse width modulation method can be based on the unipolar pulse width modulation method On the premise that the operating frequency of a single power switch remains unchanged, the equivalent switching frequency of the inverter output voltage is doubled, so that the output inductance is further reduced, thereby reducing costs, reducing volume and weight, and reducing the generation of filter inductance. copper loss and magnetic loss.
本发明的开关电容实现无变压器型逆变器可适用于独立型逆变器和并网型逆变器系统，并特别适合应用在光伏并网发电系统中。The transformerless inverter implemented by switched capacitors of the present invention is applicable to independent inverters and grid-connected inverter systems, and is particularly suitable for application in photovoltaic grid-connected power generation systems.
本发明的开关电容实现无变压器型逆变器应用于光伏并网发电系统时，直流电源的正极与第一电容的第一端相连，直流电源的负极与第一电容的第二端相连，电网的火线与滤波器的第一输出端相连，电网的零线与滤波器的第二输出端相连；然后分别向第一功率开关、第二功率开关、第三功率开关、第四功率开关和第五功率开关的控制端输入所述的单极性脉冲宽度调制或倍频式脉冲宽度调制信号，控制所对应开关管的开通和关断，实现直流电源上的直流电能转换成交流电能输送至电网。由于光伏电池极板与大地间的寄生电容被输电导线短路，对地漏电流被完全消除。When the switched capacitor of the present invention implements a transformerless inverter and is applied to a photovoltaic grid-connected power generation system, the positive pole of the DC power supply is connected to the first terminal of the first capacitor, the negative pole of the DC power supply is connected to the second terminal of the first capacitor, and the power grid The live wire of the power grid is connected to the first output end of the filter, and the neutral wire of the power grid is connected to the second output end of the filter; The control terminal of the five-power switch inputs the unipolar pulse width modulation or frequency multiplication pulse width modulation signal to control the opening and closing of the corresponding switching tube, so as to realize the conversion of DC power on the DC power supply into AC power and transmit it to the power grid . Since the parasitic capacitance between the photovoltaic cell plate and the ground is short-circuited by the power transmission wire, the leakage current to the ground is completely eliminated.
本发明的开关电容实现无变压器型逆变器需要的直流输入电压与全桥逆变器相同，相比于半桥电路或中点箝位半桥电路，仅需要一半的直流输入电压，从而减少了前级直流输入源串联的数量或者降低了前级DC/DC升压电路的升压比例。The switching capacitor of the present invention realizes that the DC input voltage required by the transformerless inverter is the same as that of the full-bridge inverter. Compared with the half-bridge circuit or the mid-point clamped half-bridge circuit, only half of the DC input voltage is required, thereby reducing The number of series connection of the previous DC input sources or the boost ratio of the previous DC/DC boost circuit are reduced.
本发明的开关电容实现无变压器型逆变器结构简单，能够有效抑制无变压器型光伏并网系统中的对地漏电流、需要的直流输入电压与全桥逆变器相同且支持三电平输出。The switching capacitor of the present invention realizes a transformerless inverter with a simple structure, can effectively suppress ground leakage current in a transformerless photovoltaic grid-connected system, requires the same DC input voltage as a full-bridge inverter, and supports three-level output.
附图说明 Description of drawings
图1是本发明开关电容实现无变压器型逆变器的电路示意图。Fig. 1 is a schematic circuit diagram of a transformerless inverter realized by switching capacitors according to the present invention.
图2a-图2c是本发明开关电容实现无变压器型逆变器中三种滤波器结构的示意图。Fig. 2a-Fig. 2c are schematic diagrams of three filter structures in a transformerless inverter realized by switched capacitors according to the present invention.
图3是本发明采用单极性脉宽调制方式的波形示意图。Fig. 3 is a schematic diagram of waveforms in the present invention using unipolar pulse width modulation.
图4是本发明采用倍频式脉宽调制方式的波形示意图。Fig. 4 is a schematic diagram of the waveforms of the present invention adopting the frequency doubling pulse width modulation method.
图5a-图5d是本发明开关电容实现无变压器型逆变器的四种工作模式示意图。Fig. 5a-Fig. 5d are schematic diagrams of four working modes of switching capacitors to realize transformerless inverter according to the present invention.
具体实施方式 Detailed ways
参见附图1，本发明的开关电容实现无变压器型逆变器包括第一电容C1，第二电容C2，第一功率开关S1，第二功率开关S2，第三功率开关S3，第四功率开关S4，第五功率开关S5和滤波器F。Referring to accompanying
本实施例所述的功率开关S1-S5由功率晶体管T1-T5和反并二极管D1-D5分别并联组成，功率晶体管的漏极或集电极与反并二极管的阴极相连构成功率开关的漏极，功率晶体管的源极或发射极与反并二极管的阳极相连构成功率开关的源极。The power switches S 1 -S 5 described in this embodiment are composed of power transistors T 1 -T 5 and anti-parallel diodes D 1 -D 5 respectively connected in parallel, and the drains or collectors of the power transistors are connected to the cathodes of the anti-parallel diodes The drain of the power switch, the source or emitter of the power transistor and the anode of the anti-parallel diode are connected to form the source of the power switch.
第一电容C1的第一端与第一功率开关S1的漏极相连，第一功率开关S1的源极与第二功率开关S2的漏极、第二电容C2的第一端和第四功率开关S4的漏极相连，第二功率开关S2的源极与第一电容C1的第二端和第三功率开关S3的漏极相连，第三功率开关S3的源极与第二电容C2的第二端和第五功率开关S5的源极相连，第五功率开关S5的漏极与第四功率开关S4的源极相连，第五功率开关S5的漏极与滤波器F的第一输入端相连，第一电容C1的第二端与滤波器F的第二输入端相连。图中Vdc为直流侧输入电压，iac为交流侧输出电流。The first end of the first capacitor C1 is connected to the drain of the first power switch S1 , the source of the first power switch S1 is connected to the drain of the second power switch S2 , and the first end of the second capacitor C2 It is connected to the drain of the fourth power switch S4 , the source of the second power switch S2 is connected to the second terminal of the first capacitor C1 and the drain of the third power switch S3 , and the drain of the third power switch S3 The source is connected to the second terminal of the second capacitor C2 and the source of the fifth power switch S5 , the drain of the fifth power switch S5 is connected to the source of the fourth power switch S4 , and the fifth power switch S The drain of C1 is connected to the first input terminal of the filter F, and the second terminal of the first capacitor C1 is connected to the second input terminal of the filter F. In the figure, V dc is the input voltage of the direct current side, and i ac is the output current of the alternating current side.
将直流电源和电网接入所述的逆变器，其中直流电源的正极与第一电容C1的第一端相连，直流电源的负极与第一电容C1的第二端相连，电网的火线与滤波器F的第一输出端相连，电网的零线与滤波器F的第二输出端相连；然后通过驱动电路分别向第一功率开关S1、第二功率开关S2、第三功率开关S3、第四功率开关S4和第五功率开关S5的控制端输入控制信号，控制所对应开关管的开通和关断，实现直流电源上的直流电能转换成交流电能输送电网，同时保证不因逆变器工作产生对地漏电流。Connect the DC power supply and the grid to the inverter, wherein the positive pole of the DC power supply is connected to the first end of the first capacitor C1 , the negative pole of the DC power supply is connected to the second end of the first capacitor C1 , and the live wire of the grid It is connected to the first output end of the filter F, and the neutral line of the power grid is connected to the second output end of the filter F; and then the first power switch S1 , the second power switch S2 , and the third power switch S 3 , the control terminals of the fourth power switch S 4 and the fifth power switch S 5 input control signals to control the opening and closing of the corresponding switching tubes, so as to realize the conversion of DC power on the DC power supply into AC power for transmission to the grid, while ensuring There is no leakage current to ground due to the operation of the inverter.
图2a-图2c具体给出了滤波器F的三种不同的组成方式。Figures 2a-2c specifically show three different composition methods of the filter F.
图2a给出了电感型滤波器。其中滤波电感Lf的第一端与滤波器F的第一输入端相连，滤波电感Lf的第二端与滤波器F的第一输出端相连，滤波器F的第二输入端和第二输出端则直接相连。Figure 2a shows an inductive filter. Wherein the first end of the filter inductance L f is connected to the first input end of the filter F, the second end of the filter inductance L f is connected to the first output end of the filter F, the second input end of the filter F is connected to the second The output is directly connected.
图2b给出了电感-电容型滤波器。其中滤波电感Lf的第一端与滤波器F的第一输入端相连，滤波电感Lf的第二端与滤波器F的第一输出端相连，滤波电容Cf的第一端和第二端分别与滤波器F的第一输出端和第二输出端相连，滤波器F的第二输入端和第二输出端则直接相连。Figure 2b shows the inductance - capacitance filter. Wherein the first end of the filter inductor L f is connected to the first input end of the filter F, the second end of the filter inductor L f is connected to the first output end of the filter F, the first end of the filter capacitor C f is connected to the second The terminals are connected to the first output terminal and the second output terminal of the filter F respectively, and the second input terminal and the second output terminal of the filter F are directly connected.
图2c给出了电感-电容-电感型滤波器。其中第一滤波电感Lf1的第一端与滤波器F的第一输入端相连，第一滤波电感Lf1的第二端与第二滤波电感Lf2的第一端和滤波电容Cf的第一端相连，第二滤波电感Lf2的第二端与滤波器F的第一输出端相连，滤波电容Cf的第二端与滤波器F的第二输出端相连，滤波器F的第二输入端和第二输出端则直接相连。Figure 2c shows an inductor-capacitor-inductor filter. Wherein the first end of the first filter inductor L f1 is connected to the first input end of the filter F, the second end of the first filter inductor L f1 is connected to the first end of the second filter inductor L f2 and the first end of the filter capacitor C f One end is connected, the second end of the second filter inductor L f2 is connected to the first output end of the filter F, the second end of the filter capacitor C f is connected to the second output end of the filter F, and the second end of the filter F The input terminal is directly connected to the second output terminal.
本发明的开关电容实现无变压器型逆变器具有两种调制方式：单极性脉冲宽度调制和倍频式脉冲宽度调制。The switched capacitor realized transformerless inverter of the present invention has two modulation modes: unipolar pulse width modulation and frequency multiplication pulse width modulation.
附图3是采用单极性脉宽调制方式的波形示意图，其中uc是高频(例如20kHz)载波，ug是工频(例如50Hz)调制波。当工频调制波ug处于正半周期时，第一功率开关S1和第三功率开关S3导通，第二功率开关S2关断，第四功率开关S4和第五功率开关S5做互补的高频开关动作；当工频调制波ug处于负半周期时，第四功率开关S4关断，第五功率开关S5导通，第一功率开关S1和第三功率开关S3做同步的高频开关动作，第一功率开关S1和第二功率开关S2做互补的高频开关动作。Accompanying
附图4是采用倍频式脉宽调制方式的波形图，其中uc是高频(例如20kHz)载波，ug1和ug2是相位相反的工频(例如50Hz)调制波。第一功率开关S1和第三功率开关S3做同步的高频开关动作，第一功率开关S1和第二功率开关S2做互补的高频开关动作，第一功率开关S1、第二功率开关S2和第三功率开关S3的调制波为ug1；第四功率开关S4和第五功率开关S5做互补的高频开关动作，调制波为ug2。
参见附图5a-附图5d，本发明的无变压器型逆变器在整个工作过程中，最多存在4种工作模式。Referring to accompanying drawings 5a-5d, the transformerless inverter of the present invention has at most 4 working modes during the whole working process.
在工作模式1时(参见附图5a)，第一功率开关S1、第三功率开关S3和第四功率开关S4处于导通状态，第二功率开关S2和第五功率开关S5处于关断状态，逆变器输出正电平，同时第二电容C2被充电直至其两端电压与直流输入电压相同。In working mode 1 (see accompanying drawing 5a), the first power switch S 1 , the third power switch S 3 and the fourth power switch S 4 are in the conduction state, and the second power switch S 2 and the fifth power switch S 5 In the off state, the inverter outputs a positive level, and at the same time, the second capacitor C2 is charged until the voltage at its two ends is equal to the DC input voltage.
在工作模式2时(参见附图5b)，第一功率开关S1、第三功率开关S3和第五功率开关S5处于导通状态，第二功率开关S2和第四功率开关S4处于关断状态，逆变器输出零电平，同时第二电容C2被充电直至其两端电压与直流输入电压相同。In working mode 2 (see accompanying drawing 5b), the first power switch S 1 , the third power switch S 3 and the fifth power switch S 5 are in the conduction state, and the second power switch S 2 and the fourth power switch S 4 In the off state, the inverter outputs zero level, and at the same time, the second capacitor C2 is charged until the voltage at its two ends is equal to the DC input voltage.
在工作模式3时(参见附图5c)，第二功率开关S2和第五功率开关S5处于导通状态，第一功率开关S1、第三功率开关S3和第四功率开关S4处于关断状态，由于在第二电容C2在工作模式1和工作模式2时已被充电，并且其电压在一个开关周期内近似保持不变，逆变器输出负电平。In working mode 3 (see accompanying drawing 5c), the second power switch S 2 and the fifth power switch S 5 are in the conduction state, the first power switch S 1 , the third power switch S 3 and the fourth power switch S 4 In the off state, since the second capacitor C2 has been charged in working
在工作模式4时(参见附图5d)，第二功率开关S2和第四功率开关S4处于导通状态，第一功率开关S1、第三功率开关S3和第五功率开关S5处于关断状态，逆变器输出零电平。In working mode 4 (see accompanying drawing 5d), the second power switch S 2 and the fourth power switch S 4 are in the conduction state, and the first power switch S 1 , the third power switch S 3 and the fifth power switch S 5 In the off state, the inverter outputs zero level.
当所有功率开关依照单极性脉冲宽度调试或倍频脉冲宽度调试给出的控制信号工作时，逆变器不断在上述四种工作模式间切换，从而实现直流电能向交流电能的转换。When all power switches work according to the control signals given by unipolar pulse width debugging or multiplied pulse width debugging, the inverter continuously switches between the above four operating modes, thereby realizing the conversion of DC power to AC power.
本实施例所述的功率开关可以由其内部自带反并二极管的开关晶体管构成，也可以由独立开关晶体管和独立二极管反并联后构成；所述开关晶体管可以是功率金属氧化物硅场效应晶体管(Metal Oxide SemiconductorField-effect Transistor，MOSFET)或绝缘双极晶体管(Insulated Gate BipolarTransistor，IGBT)等全控型功率半导体器件；所述滤波器F为电感型滤波器，也可由电感-电容型滤波器或电感-电容-电感型滤波器替代；本实施例所述的无变压器型逆变器结构，既适用于并网型逆变器也适用于独立型逆变器结构或其他无变压器型逆变场合。The power switch described in this embodiment can be composed of a switching transistor with its own anti-parallel diode inside, or can be composed of an independent switching transistor and an independent diode after anti-parallel connection; the switching transistor can be a power metal oxide silicon field effect transistor (Metal Oxide Semiconductor Field-effect Transistor, MOSFET) or insulated bipolar transistor (Insulated Gate Bipolar Transistor, IGBT) and other fully controlled power semiconductor devices; the filter F is an inductive filter, and can also be composed of an inductive-capacitive filter or The inductance-capacitance-inductance filter is replaced; the transformerless inverter structure described in this embodiment is suitable for both grid-connected inverters and independent inverter structures or other transformerless inverters .
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