CN108023496B - Series simultaneous selection switch voltage type single-stage multi-input low-frequency link inverter - Google Patents
Series simultaneous selection switch voltage type single-stage multi-input low-frequency link inverter Download PDFInfo
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- 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
- H02M7/501—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 sinusoidal output voltages being obtained by the combination of several pulse-voltages having different amplitude and width
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- H02J3/382—
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- H02J3/387—
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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
- H02M7/538—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 push-pull configuration
- H02M7/53803—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 push-pull configuration with automatic control of output voltage or current
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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
- H02M7/53871—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 automatic control of output voltage or current
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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
- H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
- H02M1/007—Plural converter units in cascade
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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
- H02M1/0083—Converters characterised by their input or output configuration
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Abstract
The invention relates to a series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter, which is formed by connecting a plurality of input filters which are not in common with a common output low-frequency isolation transformation filter circuit by a multiple-input single-output high-frequency inverter circuit with a series simultaneous selection power switch, wherein each input end of the multiple-input single-output high-frequency inverter circuit is correspondingly connected with the output end of each input filter one by one, and the output end of the multiple-input single-output high-frequency inverter circuit is connected with the input end of the output low-frequency isolation transformation filter circuit. The inverter has the characteristics of multiple input sources which are not in common ground, power supply at the same time or in a time-sharing manner, low-frequency isolation between output and input, shared output low-frequency voltage transformation and filtering circuit, simple circuit topology, single-stage power transformation, high transformation efficiency, small output voltage ripple, wide application prospect and the like, and lays a key technology for realizing a large-capacity distributed power supply system for jointly supplying power by multiple new energy sources.
Description
Technical Field
The invention relates to a series simultaneous selection switch voltage type single-stage multi-input low-frequency link inverter, belonging to the power electronic conversion technology.
Background
The inverter is a static converter which applies a power semiconductor device to convert unstable and poor direct current electric energy into stable and good alternating current electric energy, and is used for alternating current loads or realizes alternating current grid connection. The inverter with low-frequency electric isolation or high-frequency electric isolation between the output alternating current load or alternating current power grid and the input direct current power supply is respectively called as a low-frequency link inverter and a high-frequency link inverter. The electrical isolation element plays a major role in the inverter: (1) the electrical isolation between the output and the input of the inverter is realized, and the safety reliability and the electromagnetic compatibility of the operation of the inverter are improved; (2) the matching between the output voltage and the input voltage of the inverter is realized, namely the technical effect that the output voltage of the inverter is higher than, equal to or lower than the input voltage is realized, and the application range of the inverter is greatly widened. Therefore, the inverter has an important application value in secondary power conversion using a dc generator, a battery, a photovoltaic cell, a fuel cell, or the like as a main dc power source.
The new energy sources (also called green energy sources) such as solar energy, wind energy, tidal energy, geothermal energy and the like have the advantages of cleanness, no pollution, low price, reliability, richness and the like, thereby having wide application prospect. Due to the increasing shortage of traditional fossil energy (non-renewable energy) such as petroleum, coal and natural gas, serious environmental pollution, global warming, nuclear waste generated by nuclear energy production, environmental pollution and the like, the development and utilization of new energy are receiving more and more attention. The new energy power generation mainly comprises photovoltaic, wind power, fuel cells, water power, geothermal energy and the like, and all the types have the defects of unstable and discontinuous power supply, change along with climatic conditions and the like, so that a distributed power supply system adopting various new energy sources for combined power supply is needed.
A traditional new energy distributed power supply system is shown in figures 1 and 2. The system generally adopts a plurality of single-input direct-current converters to convert electric energy of new energy power generation equipment which does not need energy storage, such as photovoltaic cells, fuel cells, wind driven generators and the like, through one unidirectional direct-current converter respectively, and the output ends of the new energy power generation equipment are connected to a direct-current bus of a common inverter in parallel or in series, so that the combined power supply of various new energy sources is ensured, and the coordinated work can be realized. The distributed power generation system realizes the priority utilization of the power supplied by a plurality of input sources to the load and the energy, improves the stability and the flexibility of the system, but has the defects of two-stage power conversion, low power density, low conversion efficiency, high cost and the like, and the practicability of the distributed power generation system is limited by a great degree.
In order to simplify the circuit structure and reduce the number of power conversion stages, a novel single-stage new energy distributed power supply system needs to be formed by replacing the conventional multi-input inverter with a direct-current converter and an inverter two-stage cascade circuit structure shown in fig. 1 and 2 by the novel multi-input inverter with a single-stage circuit structure shown in fig. 3. The single-stage multi-input inverter allows for multiple new energy inputs, and the nature, magnitude and characteristics of the input sources may be the same or may vary widely. The novel single-stage new energy distributed power supply system has the advantages of simple circuit structure, single-stage power conversion, low cost and the like, and a plurality of input sources simultaneously or in time-sharing mode supply power to a load in one high-frequency switching period.
Therefore, the active search for a single-stage multi-input inverter allowing multiple new energy sources to supply power jointly and a new energy source distributed power supply system thereof is urgent, and the active search has a very important significance for improving the stability and flexibility of the system and realizing the prior utilization or the full utilization of the new energy sources.
Disclosure of Invention
The invention aims to provide a series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter which has the characteristics of multiple new energy sources combined power supply, non-common ground of input direct-current power supplies, a series simultaneous selection switch arranged on a multiple-input single-output high-frequency inverter circuit, low-frequency isolation between output and input, simultaneous or time-sharing power supply of multiple input power supplies to a load, simple circuit topology, a common output low-frequency voltage transformation filter circuit, single-stage power conversion, high conversion efficiency, small output voltage ripple, large output capacity, wide application prospect and the like.
The technical scheme of the invention is as follows: a series connection simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter is formed by connecting a plurality of input filters which are not in common with each other and a shared output low-frequency isolation transformation filter circuit through a multiple-input single-output high-frequency inverter circuit, wherein each input end of the multiple-input single-output high-frequency inverter circuit is correspondingly connected with the output end of each input filter, the output end of the multiple-input single-output high-frequency inverter circuit is connected with the input end of a low-frequency transformer of the output low-frequency isolation transformation filter circuit or the input end of an output filter inductor which is not connected with the low-frequency transformer or the input end of an output filter, the multiple-input single-output high-frequency inverter circuit is formed by sequentially cascading a plurality of paths of series connection simultaneous selection power switch circuits and a bidirectional power flow single-input single-output high-frequency inverter circuit which are in series connection in the output end in the forward direction, and is, each series simultaneous selection power switch circuit is composed of a two-quadrant power switch and a power diode, the source electrode of the two-quadrant power switch is connected with the cathode of the power diode, the drain electrode of the two-quadrant power switch and the anode of the power diode are respectively the positive and negative polarity input ends of the series simultaneous selection power switch circuit, the source electrode of the two-quadrant power switch and the anode of the power diode are respectively the positive and negative polarity output ends of the series simultaneous selection power switch circuit, and the output low-frequency isolation voltage-transformation filter circuit is composed of a low-frequency transformer, an output filter or an output filter inductor, a low-frequency transformer, an output filter capacitor or an output filter and a low-frequency transformer which are sequentially cascaded.
The invention relates to a multi-input inverter circuit structure formed by cascading a direct current converter and an inverter of a traditional multi-new-energy combined power supply system in two stages, which is constructed into a novel single-stage multi-input inverter circuit structure connected in series with a simultaneous selection switch, and provides a series simultaneous selection switch voltage type single-stage multi-input low-frequency link inverter circuit structure, a topology family and an energy management control strategy thereof.
The series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter can invert a plurality of non-common-ground and unstable input direct-current voltages into stable and high-quality output alternating-current power required by a load, and has the characteristics of non-common-ground of multiple-input direct-current power supplies, no isolation between multiple-input single-output high-frequency inverter circuits, low-frequency isolation of output and input, simultaneous or time-sharing power supply of the multiple-input power supplies to the load, simple circuit topology, common output low-frequency voltage transformation filter circuits, single-stage power transformation, high transformation efficiency, small output voltage ripple, large output capacity, wide application prospect and the like. The comprehensive performance of the series simultaneous selection switch voltage type single-stage multi-input low-frequency link inverter is superior to that of a multi-input inverter formed by two-stage cascading of a traditional direct current converter and an inverter.
Drawings
Fig. 1 shows a conventional two-stage new energy distributed power supply system with a plurality of unidirectional dc converters connected in parallel at output terminals.
Fig. 2 shows a conventional two-stage new energy distributed power supply system with a plurality of unidirectional dc converters connected in series at output terminals.
Fig. 3 is a schematic block diagram of a novel single-stage multiple-input inverter.
Fig. 4 is a schematic block diagram of a series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter.
Fig. 5 is a circuit diagram of a series simultaneous selection switching voltage type single-stage multiple-input low-frequency link inverter.
Fig. 6 is a steady-state schematic waveform diagram of a bipolar SPWM-controlled series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter.
Fig. 7 is a steady-state schematic waveform diagram of a unipolar SPWM-controlled series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter.
Fig. 8 is a schematic diagram of a push-pull circuit, which is an example of a circuit topology of a series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter.
Fig. 9 is a schematic diagram of a circuit topology example of a series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter, i.e., a push-pull forward circuit.
Fig. 10 is a schematic diagram of a three-half bridge circuit of a circuit topology example of a series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter.
Fig. 11 is a schematic diagram ii of a four-half bridge circuit of a circuit topology example of a series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter.
Fig. 12 is a schematic diagram iii of a five-half bridge circuit of a circuit topology example of a series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter.
Fig. 13 is a schematic diagram of a six-full bridge circuit of a circuit topology example of a series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter.
Fig. 14 is a seven-full bridge circuit schematic diagram ii of a circuit topology example of a series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter.
Fig. 15 is a schematic diagram iii of a full-bridge circuit according to an example of a circuit topology of a series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter circuit.
Fig. 16 is a master-slave power distribution energy management control block diagram of a series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter, in which the output voltage and input current instantaneous values are fed back to a bipolar SPWM.
Fig. 17 is a waveform diagram of a master-slave power distribution energy management control principle of a bipolar SPWM fed back by instantaneous values of output voltage and input current of a series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter.
Fig. 18 is a block diagram of a master-slave power distribution energy management control of a unipolar SPWM fed back by instantaneous values of output voltage and input current of a series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter.
Fig. 19 is a waveform diagram of the output voltage and input current instantaneous value feedback unipolar SPWM master-slave power distribution energy management control principle of the series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter.
Fig. 20 shows a series simultaneous selection switch voltage type single-stage multiple-input low-frequency link independent power supply system with an output connected in parallel with a single-stage isolated bidirectional charge-discharge converter.
Fig. 21, maximum power output energy management control strategy with single stage isolated bidirectional charge-discharge converter output voltage independent control loop.
FIG. 22, output voltage u of independent power supply systemoAnd outputting the filtered inductor current iLf、iLf' waveform.
Detailed Description
The technical solution of the present invention is further described below with reference to the drawings and examples of the specification.
A series connection simultaneous selection switch voltage type single-stage multiple-input and multiple-output low-frequency link inverter is formed by connecting a multiple-input single-output high-frequency inverter circuit with a plurality of input filters which are not in common with the ground and a common output low-frequency isolation transformation filter circuit, wherein each input end of the multiple-input single-output high-frequency inverter circuit is correspondingly connected with the output end of each input filter one by one, the output end of the multiple-input single-output high-frequency inverter circuit is connected with the input end of a low-frequency transformer of the output low-frequency isolation transformation filter circuit or the input end of an output filter inductor which is not connected with the low-frequency transformer or the input end of an output filter, the multiple-input single-output high-frequency inverter circuit is formed by sequentially cascading a plurality of series connection simultaneous selection power switch circuits and a bidirectional power flow single-input single-output high-frequency inverter circuit which are sequentially connected in series with the output, each series simultaneous selection power switch circuit is composed of a two-quadrant power switch and a power diode, the source electrode of the two-quadrant power switch is connected with the cathode of the power diode, the drain electrode of the two-quadrant power switch and the anode of the power diode are respectively the positive and negative polarity input ends of the series simultaneous selection power switch circuit, the source electrode of the two-quadrant power switch and the anode of the power diode are respectively the positive and negative polarity output ends of the series simultaneous selection power switch circuit, and the output low-frequency isolation voltage-transformation filter circuit is composed of a low-frequency transformer, an output filter or an output filter inductor, a low-frequency transformer, an output filter capacitor or an output filter and a low-frequency transformer which are sequentially cascaded.
Schematic block diagrams, circuit structures, and stable-state principle waveforms of the series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter, the bipolar SPWM control inverter, and the unipolar SPWM control inverter are shown in fig. 4, 5, 6, and 7, respectively. In FIGS. 4, 5, 6 and 7, Ui1、Ui2、…、UinInputting a DC voltage source (n is a natural number greater than 1) for n paths, ZLFor single-phase AC loads (both passive and active), uo、ioRespectively single-phase output alternating voltage and alternating current. The n-input single-output high-frequency inverter circuit is formed by sequentially cascading a plurality of paths of series-connected simultaneous selection power switch circuits with output ends in forward series and a bidirectional power flow single-input single-output high-frequency inverter circuit, wherein the plurality of paths of series-connected simultaneous selection power switch circuits with output ends in forward series are formed by n two-quadrant high-frequency power selection switches S capable of bearing unidirectional voltage stress and bidirectional current stresss1、Ss2、…、SsnAnd n selection diodes Ds1、Ds2、…、DsnConstitution (Power selection switch Ss1、Ss2、…、SsnSimultaneous switching-on or switching-on with phase difference, with identical or different switching frequencies, where only S is analyseds1、Ss2、…、SsnThe control mode that the two-way power flow single-input single-output high-frequency inverter circuit adopts the same switching frequency and is simultaneously switched on) is formed by a plurality of two-quadrant high-frequency power switches capable of bearing unidirectional voltage stress and bidirectional current stress, and power devices such as an MOSFET (metal oxide semiconductor field effect transistor), an IGBT (insulated gate bipolar transistor), a GTR (GTR) and the like can be selected; the output low-frequency isolation transformation filter circuit in the virtual frame (the end of '1' and the end of '1' are connected ends) is formed by sequentially cascading a low-frequency transformer and an output filter, or is formed by sequentially cascading an output filter inductor, a low-frequency transformer and an output filter capacitor (the primary side leakage inductance of the low-frequency transformer can be absorbed and utilized by the output filter inductor or can be completely used as the output filter inductor), or is formed by sequentially cascading the output filter and the low-frequency transformer, and only the circuit diagram of an LC output filter or an output filter capacitor suitable for a passive alternating-current load is drawn in a space diagram, but the circuit diagram of an LCL output filter suitable for an alternating-current power grid load or the circuit diagram of the output filter inductor added after the output filter capacitor is not drawn; the n-path input filter is an LC filter (filter inductor L with an added virtual frame)i1、Li2、…、Lin) Or a capacitor filter (filter inductor L without adding a virtual frame)i1、Li2、…、Lin) When an LC filter is adopted, the n input direct current paths are smoother. The n-input single-output high-frequency inverter circuit inputs n paths of direct-current voltage sources Ui1、Ui2、…、UinModulating to bipolar two-state or unipolar three-state multi-level SPWM voltage wave u with amplitude changing along with number of input power suppliesABPassing through a low-frequency transformer T and an output filter Lf-CfOr via an output filter inductor LfLow frequency transformer T, output filter capacitor CfOr via an output filter inductor LfAn output filter capacitor CfObtaining high-quality sine alternating-current voltage u on single-phase alternating-current passive load or single-phase alternating-current power grid after low-frequency transformer ToOr sinusoidal alternating current ioN inputN input pulse currents of single-output high-frequency inverter circuit pass through input filter Li1-Ci1、Li2-Ci2、…、Lin-CinOr Ci1、Ci2、…、CinThen inputting a direct current power supply U in n pathsi1、Ui2、…、UinTo obtain a smooth input direct current Ii1、Ii2、…、Iin. It should be added that when the output low-frequency isolation voltage transformation filter circuit is formed by sequentially cascading a low-frequency transformer and an output filter, the dual-polarity two-state multi-level SPWM voltage wave uABThe amplitude of the +1 state of the positive half cycle is output as (U)i1+Ui2+…+Uin)N2/N1、(Ui1+Ui2+…+Uin-1)N2/N1、…、Ui1N2/N1And-1 state amplitude of (U)i1+Ui2+…+Uin)N2/N1The output negative half cycle-1 state amplitude is (U)i1+Ui2+…+Uin)N2/N1、(Ui1+Ui2+…+Uin-1)N2/N1、…、Ui1N2/N1And +1 state amplitude of (U)i1+Ui2+…+Uin)N2/N1(ii) a Unipolar three-state multi-level SPWM voltage wave uABThe amplitudes of the +1 state and the-1 state are both (U)i1+Ui2+…+Uin)N2/N1、(Ui1+Ui2+…+Uin-1)N2/N1、…、Ui1N2/N1(ii) a When N is present2/N1When 1, the multi-level SPWM voltage wave uABThe amplitude expression is that when the output low-frequency isolation voltage transformation filter circuit is formed by sequentially cascading an output filter inductor, a low-frequency transformer, an output filter capacitor or an output filter and a low-frequency transformer, the voltage wave u of the SPWM is bipolar two-state and unipolar three-state multi-levelABThe corresponding amplitude. For a half-bridge circuit, the dual polarity two-state multi-level SPWM voltage wave u shown in FIG. 6ABThe +1 state amplitude and the-1 state amplitude at the positive and negative half cycles of the output voltage are multiplied by1/2。
The series simultaneous selection switch voltage type single-stage multi-input low-frequency link inverter belongs to a step-down inverter, and n input sources can supply power to a load at the same time and in a time-sharing manner. Let n-1 output signals I of the input source error amplifier1e、I2e、…、I(n-1)eAnd the output signal u of the output voltage error amplifiereHas an amplitude of I1em、I2em、I(n-1)em、UemSaw-tooth carrier signal ucHas an amplitude of UcmThen the corresponding modulation degree is m1＝I1em/Ucm、m2＝I2em/Ucm、…、mn＝Uem/UcmAnd has 0. ltoreq. mn、…、m2、m1Less than or equal to 1 and m1＞m2＞…＞mn. The principle of the inverter is equivalent to the superposition of voltages at the output end of a plurality of voltage type single-input inverters, namely the output voltage uoAnd input direct current voltage (U)i1、Ui2、…、Uin) Turn ratio N of low frequency transformer2/N1Degree of modulation (m)1、m2、…、mn) The relationship between is uo＝[(m1Ui1+m2Ui2+…+mnUin)]N2/N1(unipolar SPWM control) or uo＝[(2m1-1)Ui1+(m2+m1-1)Ui2+…+(mn+m1-1)Uin]N2/N1(bipolar SPWM control). For a suitable modulation degree m1、m2、…、mnAnd the turn ratio N of the low-frequency transformer2/N1，uoCan be more than, equal to or less than the sum U of the input direct current voltagesi1+Ui2+…+UinThe low-frequency transformer in the inverter not only improves the safety reliability and the electromagnetic compatibility of the operation of the inverter, but also plays a role in matching the output voltage with the input voltage, namely, the output voltage of the inverter is higher than, equal to or lower than the sum U of the input direct-current voltagesi1+Ui2+…+UinThe application range of the method is greatly widened. Due to the existence of 0 < m1、m2、…、mn< 1 (unipolar SPWM control) and (2 m)1-1)+(m2+m1-1)+…+(mn+m1-1) < 1 (bipolar SPWM control), so uo＜(Ui1+Ui2+…+Uin)N2/N1I.e. the output voltage uoIs always lower than the input DC voltage (U)i1、Ui2、…、Uin) Turn ratio N of low-frequency transformer2/N1Sum of products (U)i1+Ui2+…+Uin)N2/N1(ii) a The inverter belongs to a single-stage circuit structure, the working frequency of a transformer of the inverter is equal to the frequency of output voltage, and the n-input single-output high-frequency inverter circuit is provided with a plurality of paths of series simultaneous selection power switch circuits with output ends connected in series in a forward direction, so that the inverter is called a series simultaneous selection switch voltage type (voltage reduction type) single-stage multi-input low-frequency link inverter. The n input sources of the inverter supply power to the output alternating current load simultaneously or in a time-sharing manner in a high-frequency switching period, and the modulation degrees can be the same (m1＝m2＝…＝mn) Or may be different (m)1≠m2≠…≠mn)。
The series simultaneous selection switch voltage type single-stage multi-input low-frequency link inverter provided by the invention shares a multi-input single-output high-frequency inverter circuit and an output low-frequency isolation transformation filter circuit, and is essentially different from the circuit structure of the traditional multi-input inverter formed by two-stage cascade connection of a direct current converter and an inverter. Therefore, the inverter has novelty and creativity, and has the advantages of low-frequency isolation of output and input, simultaneous or time-sharing power supply within one switching period of a multi-input power supply, simple circuit topology, single-stage power conversion, high conversion efficiency (meaning small energy loss), flexible input voltage preparation, small output voltage ripple, large output capacity, low cost, wide application prospect and the like, is an ideal energy-saving and consumption-reducing single-stage multi-input inverter, and has important value in the modern times of vigorously advocating the construction of energy-saving and conservation-oriented society.
Series simultaneous selection switching voltage type single-stage multiple-input low-frequency link inverter circuit topology family embodiments are shown in fig. 8, 9, 10, 11, 12, 13, 14 and 15. In the circuits shown in fig. 8-15, the multi-path series simultaneous selection power switch circuits with output terminals connected in series in the forward direction are each composed of n two-quadrant high-frequency power switches and n diodes, the bidirectional power flow single-input single-output high-frequency inverter circuit is composed of a plurality of two-quadrant high-frequency power switches capable of bearing unidirectional voltage stress and bidirectional current stress (the push-pull, push-pull forward and half-bridge circuits shown in fig. 8, 9, 10, 11 and 12 are each composed of 2 two-quadrant high-frequency power switches, and the full-bridge circuits shown in fig. 13, 14 and 15 are each composed of 4 two-quadrant high-frequency power switches). It should be added that, the circuits shown in fig. 8, 9, 10, 11, 12, 13, 14, and 15 show the case where the input filter is an LC filter, and are limited to the case where the input filter is not a capacitive filter; the push-pull forward circuit of fig. 9 and the half-bridge circuits of fig. 10, 11 and 12 are only suitable for the case where the modulation ratios of the n input power sources are substantially equal; the output low-frequency isolation voltage-transformation filter circuits of the half-bridge circuits i, ii, and iii shown in fig. 10, 11, and 12 are respectively formed by sequentially cascading a low-frequency transformer and an output filter, an output filter inductor and a low-frequency transformer and an output filter capacitor, and an output filter inductor and an output filter capacitor and a low-frequency transformer; the output low-frequency isolation voltage transformation filter circuits of the full-bridge circuits i, ii, and iii shown in fig. 13, 14, and 15 are respectively formed by sequentially cascading a low-frequency transformer and an output filter, an output filter inductor and a low-frequency transformer and an output filter capacitor, and an output filter inductor and an output filter capacitor and a low-frequency transformer. The power switch voltage stresses of the four topology embodiments of the series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter are shown in table 1. The push-pull and push-pull forward circuits are suitable for high-power low-voltage input inversion occasions, the half-bridge circuit is suitable for medium-power high-voltage input inversion occasions, and the full-bridge circuit is suitable for high-power high-voltage input inversion occasions. The circuit topology family is suitable for converting a plurality of non-common-ground unstable input direct-current voltages into output alternating-current power with required voltage and stable and high quality, and can be used for realizing a novel single-stage multi-new-energy distributed power supply system with excellent performance and wide application prospect, such as photovoltaic cells 40-60VDC/220V50HzAC or115V400HzAC, 10kw proton exchange membrane fuel cells 85-120V/220V50HzAC or115V400HzAC, medium and small-sized users wind power generation 24-36-48VDC/220V50HzAC or115V400HzAC, large-scale wind power generation 510VDC/220V50 Hzor AC115V 400HzAC and the like, to supply power to alternating-current loads or alternating-current power grids.
Table 1 power switch voltage stress of four topology embodiments of series simultaneous selective switch voltage type single-stage multiple-input low-frequency link inverter
The energy management control strategy is crucial to various new energy combined power supply systems. Due to the presence of multiple input sources and corresponding power switching units, multiple duty cycles need to be controlled, i.e. there are multiple degrees of freedom of control, which provides the possibility for energy management of multiple new energy sources. An energy management control strategy of a series simultaneous selection switch voltage type single-stage multi-input low-frequency link inverter needs to have three functions of energy management of an input source, MPPT (maximum power point tracking) and output voltage (current) control of new energy power generation equipment such as a photovoltaic cell and a wind driven generator, and sometimes, the charging and discharging control of a storage battery and smooth and seamless switching of a system under different power supply modes need to be considered. The series simultaneous selection switch voltage type single-stage multi-input low-frequency link inverter adopts two different energy management modes: (1) in the energy management mode I, namely a master-slave power distribution mode, the power required by a load is known to be provided by the 1 st, 2 nd, … th and n-1 st input sources of the master power supply equipment as much as possible, the input current of the 1 st, 2 nd, … th and n-1 st input sources is given, which is equivalent to the input power of the 1 st, 2 nd, … th and n-1 st input sources, the insufficient power required by the load is provided by the nth input source of the slave power supply equipment, and a storage battery energy storage device does not need to be added; (2) in the energy management mode II, namely the maximum power output mode, the 1 st input source, the 2 nd input source, the … th input source and the n th input source are all output to a load with the maximum power, storage battery energy storage equipment is omitted, the requirement of a grid-connected power generation system on the full utilization of energy is met, and if an output end is connected with a storage battery charging and discharging device in parallel, the stability of the output voltage (current) of an independent power supply system can be realized. When the input voltage of the n paths of new energy sources is given, the input current of the 1 st, 2 nd, … th and n paths of input sources is controlled, so that the input power of the 1 st, 2 nd, … th and n paths of input sources is controlled.
The method comprises the steps that a switching voltage type single-stage multi-input low-frequency link inverter is connected in series and simultaneously selected, and an output voltage and input current instantaneous value feedback bipolar SPWM and unipolar SPWM master-slave power distribution energy management control strategy is adopted to form an independent power supply system; or the maximum power output energy management control strategy of the bipolar SPWM and the unipolar SPWM is fed back by the input current instantaneous value to form a grid-connected power generation system. The 1 st, 2 nd, … th and n-1 st input sources output power is fixed, and the nth input sources supplement the output voltage and input current instantaneous value of the insufficient power needed by the load, and the bipolar SPWM and unipolar SPWM master-slave power distribution energy management control block diagram and the control principle waveform are respectively shown in FIGS. 16, 17, 18 and 19. The 1 st, 2 nd, … th and n-1 th input sources are calculated by the maximum power point to obtain a reference current signal I＊ i1r、I＊ i2r、…、I＊ i(n-1)rInput current feedback signal I of inverter circuit 1, 2, … and n-1i1f、Ii2f、…、Ii(n-1)fReference current signal I with No. 1, No. 2, No. … and No. n-1i1r、Ii2r、…、Ii(n-1)rThe error signal I is amplified by comparison of a proportional-integral regulator1e、I2e、…、I(n-1)eRespectively multiplied by sine synchronous signals, and then the obtained result is an | i through absolute value circuits 1, 2, … and n-11e︳、︳i2e︱、…、︳i(n-1)e| the inverter outputs a voltage feedback signal uofWith reference sinusoidal voltage urAmplified by comparison with proportional-integral regulatorError signal ueObtaining an agent u after passing through an absolute value circuit ne︳,︱i1e︳、︳i2e︱、…、︳i(n-1)e︱、︱ueThe data/power ratio and the sawtooth-shaped carrier wave ucThe output voltage gating signal is processed by a proper combinational logic circuit to obtain a control signal u of the power switchgss1、ugss2、…、ugssn、ugs1(ugs4)、ugs2(ugs3). When the load power PoWhen the output voltage is larger than the sum of the maximum powers of the 1 st, 2 nd, … th and n-1 th input sourcesoReducing, the voltage regulator output voltage ueIs greater than the threshold comparison level UtAnd I1e、I2e、…、I(n-1)eAre all greater than zero, diode D1、D2、…、Dn-1Blocking, the 1 st, 2 nd, … th, n-1 th current regulators and the nth voltage regulator work independently, i.e. Ii1r＝I＊ i1r、Ii2r＝I＊ i2r、…、Ii(n-1)r＝I＊ i(n-1)rThe 1 st, 2 nd, … th and n-1 th circuit current regulators are used for realizing the maximum power output of the 1 st, 2 nd, … th and n-1 th input sources, the nth circuit voltage regulator is used for realizing the stability of the output voltage of the inverter, and the n-th input sources supply power to the load at the same time or in a time-sharing manner; when the load power PoWhen the output voltage is less than the sum of the maximum powers of the 1 st, 2 nd, … th and n-1 th input sourcesoIncrease when the voltage regulator output voltage ueIs reduced to a threshold comparison level UtWhen following, diode Dn-1On, D1、D2、…、Dn-2When the input voltage is still blocked, the hysteresis comparison circuit n +1 outputs low level, the nth input source stops supplying power, the voltage regulator and the current regulator form a double closed loop control system, the 1 st, 2 nd, … th and n-1 th input sources simultaneously or time-divisionally supply power to a load in a switching period, and the reference current I of the current regulatori(n-1)rDecrease, i.e. Ii(n-1)r＜I＊ i(n-1)rThe output power of the (n-1) th input source is reduced (the input source works at a non-maximum working point), and the output power of the (n) th input sourceReduced to zero, the output voltage u of the inverteroAnd tends to be stable. By regulating the reference voltage u as the input voltage or load variesrOr the feedback voltage uofTo change error voltage signal | ueA/d and error current signal | i1e︳、︳i2e︱、…、︳i(n-1)e| thereby changing the degree of modulation m1、m2、…、mnTherefore, the regulation and stabilization of the output voltage and the input current (output power) of the inverter can be realized.
When the nth path input source in fig. 16-19 is designed as input current feedback to control the input current, a maximum power output energy management control strategy of input current instantaneous value feedback bipolar SPWM and unipolar SPWM is formed. Input current feedback signal I of inverter 1 st, 2 nd, … th and n th pathsi1f、Ii2f、…、IinfRespectively obtaining reference current signals I after maximum power point calculation with the 1 st, 2 nd, … th and n-th input sourcesi1r、Ii2r、…、IinrComparing and amplifying by a proportional-integral regulator, and amplifying an error signal I1e、I2e、…、IneMultiplying the sine synchronous signal respectively by absolute value circuits 1, 2, … and n to obtain an | i1e︳、︳i2e︱、…、︳ine︱，︱i1e︳、︳i2e︱、…、︳ine| respectively associated with sawtooth-shaped carrier wave ucThe output voltage gating signal is processed by a proper combinational logic circuit to obtain a control signal u of the power switchgss1、ugss2、…、ugssn、ugs1(ugs4)、ugs2(ugs3). The 1 st, 2 nd, … th and n-way current regulators respectively work independently and are all used for realizing the maximum power output of respective input sources, and the n-way input sources simultaneously supply power to a load in one switching period.
The waveform of the bipolar and unipolar SPWM control principle shown in FIGS. 17 and 19 marks a certain high-frequency switching period TSAnd the conduction time T of the 1 st, 2 nd, … th input sourceon1、Ton2、…、TonnAnd a power switch S1On-time ofTon，Ton＝Ton1＞Ton2＞…＞TonnOn time TonThe variation in the output voltage period is sinusoidal. In addition, for the half-bridge circuits I, II, III shown in FIGS. 10, 11, 12, half the value of the input DC voltage (U) should be usedi1/2、Ui2/2、…、UinAnd/2) substituting into the voltage transfer ratio for calculation.
In order to form an independent power supply system capable of fully utilizing energy of multiple input sources, multiple input sources should operate in a maximum power output mode and energy storage equipment needs to be configured to achieve stabilization of output voltage, that is, a single-stage isolation bidirectional charge-discharge converter is connected in parallel to an output end of an inverter, as shown in fig. 20. The single-stage isolation bidirectional charge-discharge converter consists of an input filter (L)i、CiOr Ci) High-frequency inverter, high-frequency transformer, cycle converter, output filter (L)f′、Cf') is cascaded in sequence, and the cycle converter is composed of four-quadrant high-frequency power switches capable of bearing bidirectional voltage stress and bidirectional current stress. The single-stage isolation bidirectional charge-discharge converter is respectively equivalent to a single-stage high-frequency link DC-AC converter and a single-stage high-frequency link AC-DC converter when energy is transmitted in the forward direction (energy storage equipment is discharged) and transmitted in the reverse direction (energy storage equipment is charged).
The independent power supply system adopts a maximum power output energy management control strategy with a single-stage isolated bidirectional charge-discharge converter output voltage independent control loop, as shown in fig. 21. When the load power Po＝UoIoGreater than the sum P of the maximum powers of the plurality of input sources1max+P2max+…+PnmaxWhen the power supply is started, energy storage equipment such as a storage battery, a super capacitor and the like provides needed insufficient power to a load through a single-stage isolation bidirectional charge-discharge converter, namely a power supply mode II, and the energy storage equipment independently provides power to the load, namely a power supply mode III, and belongs to the extreme situation of the power supply mode II; when the load power Po＝UoIoLess than the sum P of the maximum powers of the plurality of input sources1max+P2max+…+PnmaxTime, output from multiple input sourcesThe residual energy is charged to the energy storage equipment through a single-stage isolation bidirectional charging and discharging converter, namely a power supply mode I. Using the band elimination load as an example, the power flow direction control of the single-stage isolated bidirectional charge-discharge converter is discussed, as shown in fig. 22. For output filter capacitor Cf、Cf' and load ZLIn other words, the parallel connection of the output ends of the series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverter and the single-stage isolation bidirectional charge-discharge converter is equivalent to the parallel superposition of two current sources. As can be seen from the energy management control strategy shown in fig. 21, the output filter inductor current i of the series simultaneous selection switch voltage type single-stage multiple-input low-frequency link inverterLfAnd the output voltage uoThe same frequency and the same phase are adopted, and active power is output; the charging and discharging converter is controlled by the output voltage uoAnd a reference voltage uorefError amplified signal uoeIntercepting with high frequency carrier to generate SPWM signal for control, outputting filter inductor current iLf' and uoThere is a phase difference theta between them, and a different phase difference theta means that active power with different magnitude and direction is output. When P is presento＝P1max+P2max+…+PnmaxWhen theta is equal to 90 degrees, the active power output by the charge-discharge converter is zero, and the charge-discharge converter is in an idle state; when P is presento>P1max+P2max+…+PnmaxWhen u is turned onoThe theta is reduced to be less than 90 degrees, the charging and discharging converter outputs active power, and the energy storage equipment discharges to the load, namely the energy storage equipment provides insufficient power required by the load; when P is presento＜P1max+P2max+…+PnmaxWhen u is turned onoAnd increasing theta to be more than 90 degrees, outputting negative active power by the charging and discharging converter, feeding energy back to the energy storage device by the load, namely charging the energy storage device by residual power output by the plurality of input sources, and feeding the energy back to the energy storage device by the load to be the maximum when the theta is 180 degrees. Thus, the energy management control strategy can be based on PoAnd P1max+P2max+…+PnmaxThe relative size of the single-stage isolation bidirectional charge-discharge converter controls the power flow size and direction of the single-stage isolation bidirectional charge-discharge converter in real time, and smooth and seamless switching of the system under three different power supply modes is realized.
Claims (2)
1. The utility model provides a series connection is selected switch voltage type single-stage multiple input low frequency link inverter simultaneously which characterized in that: the inverter is formed by sequentially cascading a bidirectional power flow n-input single-output series simultaneous selection power switch circuit, a bidirectional power flow single-input single-output high-frequency inverter circuit and an output low-frequency isolation voltage transformation filter circuit, wherein each input end of the bidirectional power flow n-input single-output series simultaneous selection power switch circuit is cascaded with one input filter, the n input filters are not isolated and have no common end, n is the number of multiple input sources, and n is a natural number greater than 1; the bidirectional power flow n input single output series simultaneous selection power switch circuit is formed by connecting n paths of series simultaneous selection power switch circuits in series in a forward direction by using the positive and negative polarity output ends of each path, each path of series simultaneous selection power switch circuit is formed by a two-quadrant power selection switch capable of bearing unidirectional voltage stress and bidirectional current stress and a power selection diode, the source electrode of the two-quadrant power selection switch is connected with the cathode of the power selection diode, the drain electrode of the two-quadrant power selection switch and the anode of the power selection diode are respectively the positive and negative polarity input ends of the path of series simultaneous selection power switch circuit, and the source electrode of the two-quadrant power selection switch and the anode of the power selection diode are respectively the positive and negative polarity output ends of the path of series simultaneous selection power switch circuit; the output low-frequency isolation transformation filter circuit is formed by sequentially cascading a low-frequency transformer, an output filter or an output filter inductor containing a primary side leakage inductor of the low-frequency transformer, an output filter capacitor or the output filter and the low-frequency transformer; the bidirectional power flow single-input single-output high-frequency inverter circuit is a push-pull type, push-pull forward type, half-bridge type or full-bridge type circuit, the push-pull type circuit is composed of two quadrant high-frequency power switches bearing unidirectional voltage stress and bidirectional current stress, the source electrodes of the two quadrant high-frequency power switches are connected with the negative output end of the series simultaneous selection power switch circuit, the drain electrodes of the two quadrant high-frequency power switches are respectively connected with two ends of a primary winding of a low-frequency transformer, a center tap of the primary winding of the low-frequency transformer is connected with the series simultaneous selection power switch circuitThe positive polarity output end of the circuit is connected, the push-pull forward circuit is composed of two quadrant high frequency power switches bearing unidirectional voltage stress bidirectional current stress and a clamping capacitor, the drain and the source of one quadrant high frequency power switch are respectively connected with the non-inverse end of one primary winding of the low frequency transformer and the inverse end of the other primary winding, the drain is connected with the positive polarity output end of the series connection simultaneous selection power switch circuit, the drain and the source of the other quadrant high frequency power switch are respectively connected with the inverse end of one primary winding of the low frequency transformer and the non-inverse end of the other primary winding, the source is connected with the negative polarity output end of the series connection simultaneous selection power switch circuit, the two ends of the clamping capacitor are respectively connected with the inverse end of the two primary windings of the low frequency transformer, the half-bridge circuit is composed of two capacitors of a left bridge arm and two quadrant high frequency power switches bearing unidirectional voltage stress bidirectional current stress of a right bridge arm, and the upper left bridge arm is The full-bridge type transformer low-frequency transformer high-frequency power supply comprises a low-frequency transformer primary winding, a full-bridge type circuit, a left upper bridge arm, a right lower bridge arm, a left upper bridge arm switch, a right lower bridge arm switch, a left lower bridge arm switch, a right lower bridge arm switch, a left upper bridge arm switch, a right lower bridge arm switch, a left upper bridge arm switch, a right lower bridge arm switch, a left lower bridge arm switch, a right upper bridge arm switch, a right lower bridge arm switch, a left lower bridge, The source electrode of the right upper bridge arm switch and the drain electrode of the right lower bridge arm switch are connected with the other end of the primary winding of the low-frequency transformer; the bidirectional power flow n input single output series connection simultaneous selection power switch circuit and the bidirectional power flow single input single output high frequency inverter circuit of the multi-input low frequency link inverter input N paths into the direct current voltage source Ui1、Ui2、…、UinModulating the voltage wave into a bipolar two-state or bipolar three-state multi-level SPWM voltage wave with the level amplitude changing along with the number of input power supplies, obtaining high-quality sinusoidal alternating voltage or grid-connected sinusoidal current on a single-phase alternating current load after the voltage wave passes through an output low-frequency isolation voltage-transformation filter circuit, and outputting the + 1-state amplitude of the positive half cycle of the bipolar two-state multi-level SPWM voltage wave (U)i1+Ui2+…+Uin)N2/N1、(Ui1+Ui2+…+Uin-1)N2/N1、…、Ui1N2/N1Or Ui1+Ui2+…+Uin、Ui1+Ui2+…+Uin-1、…、Ui1The amplitude of the-1 state of the positive half cycle is output as (U)i1+Ui2+…+Uin)N2/N1Or Ui1+Ui2+…+UinThe output negative half cycle of-1 state amplitude is (U)i1+Ui2+…+Uin)N2/N1、(Ui1+Ui2+…+Uin-1)N2/N1、…、Ui1N2/N1Or Ui1+Ui2+…+Uin、Ui1+Ui2+…+Uin-1、…、Ui1The amplitude of the +1 state of the output negative half cycle is (U)i1+Ui2+…+Uin)N2/N1Or Ui1+Ui2+…+UinThe +1 state and-1 state amplitudes of the unipolar three-state multi-level SPWM voltage wave are both (U)i1+Ui2+…+Uin)N2/N1、(Ui1+Ui2+…+Uin-1)N2/N1、…、Ui1N2/N1Or Ui1+Ui2+…+Uin、Ui1+Ui2+…+Uin-1、…、Ui1The amplitudes of the +1 state and-1 state of the positive and negative half cycles of the voltage wave of the half-bridge circuit bipolar two-state multi-level SPWM are multiplied by 1/2, N1、N2The number of turns of a primary winding and the number of turns of a secondary winding of the low-frequency transformer are respectively; the voltage stress of the 1 st, 2 nd, … th power selection switch and the n-way power selection diode is U respectivelyi1、Ui2、…、UinThe voltage stress of the two-quadrant power switch of the push-pull type and push-pull forward type, half-bridge type and full-bridge type high-frequency inverter circuits is 2 (U)i1+Ui2+…+Uin)、Ui1+Ui2+…+Uin(ii) a The independent power supply system formed by the multi-input low-frequency link inverter adopts a master-slave power distribution energy management control strategy of output voltage and input current values of output power of a 1 st input source, a 2 nd input source, an … th input source and n-1 st input source which are fixed and insufficient power required by a supplementary load of the nth input source, and feeds back bipolar SPWM or unipolar SPWM, and the grid-connected power generation system formed by the multi-input low-frequency link inverter adopts a maximum power output energy management control strategy of the bipolar SPWM or unipolar SPWM according to the feedback of the input current values of the 1 st input source, the 2 nd input source, the … th input source and; the multi-input low-frequency link inverter determines the number of input source circuits needing to be put into operation by controlling n circuits to be connected in series and simultaneously selecting the on-off of the power switch according to the size of an alternating current load, wherein the n circuits of input sources are U-shaped within a high-frequency switching periodi1+Ui2+…+Uin、Ui1+Ui2+…+Uin-1、…、Ui1The serial connection in sequence supplies power to the AC load at the same time, thus realizing the single-stage low-frequency isolation high-efficiency inversion of n input DC voltages which are unstable in the non-common ground into stable and high-quality sinusoidal AC power required by the AC load.
2. The series simultaneous selective switching voltage mode single-stage multiple-input low-frequency link inverter of claim 1, wherein: the output end of the series simultaneous selection switch voltage type single-stage multi-input low-frequency link inverter is connected with a single-stage isolation bidirectional charge-discharge converter of the energy storage device in parallel, so that an independent power supply system which can fully utilize n paths of input source energy and has stable output voltage is formed; the single-stage isolation bidirectional charge-discharge converter is formed by sequentially cascading an input direct current filter, a high-frequency inverter, a high-frequency transformer, a cycle converter and an output alternating current filter, wherein the cycle converter is formed by a four-quadrant high-frequency power switch capable of bearing bidirectional voltage stress and bidirectional current stress, the energy storage equipment is discharged by directly inverting the direct current electric energy of the energy storage equipment into alternating current load electric energy in a single stage through the single-stage isolation bidirectional charge-discharge converter, the single-stage isolation bidirectional charge-discharge converter is equivalent to a single-stage voltage type high-frequency link DC-AC converter at the moment, the energy storage equipment is charged by firstly inverting the n-path input source direct current electric energy into alternating current electric energy through the series connection and simultaneously selecting a switch voltage type single-stage multiple-input low-frequency link inverter and then rectifying and converting the alternating current electric energy into the direct, At the moment, the single-stage isolation bidirectional charge-discharge converter is equivalent to a single-stage current type high-frequency link AC-DC converter; the independent power supply system adopts a maximum power output energy management control strategy of n input sources with a single-stage isolation bidirectional charge-discharge converter output voltage independent control loop, the n input sources all work in a maximum power output mode, the power flow size and direction of the single-stage isolation bidirectional charge-discharge converter are controlled in real time according to the relative size of the sum of alternating current load power and the maximum power of the n input sources, and the smooth seamless switching of the output voltage of the system and the charge and discharge of energy storage equipment is realized; when the AC load power is greater than the sum of the maximum powers of the n input sources, the system works in a power supply mode II that the energy storage equipment inverts the DC single-stage into AC power through a single-stage isolation bidirectional charge-discharge converter to provide the needed insufficient power for the AC load, a power supply mode III that the energy storage equipment supplies power for the AC load independently belongs to the extreme situation of the power supply mode II, and when the AC load power is less than the sum of the maximum powers of the n input sources, the system works in a power supply mode I that the residual energy output by the n input sources simultaneously selects a switch voltage type single-stage multi-input low-frequency link inverter and the single-stage isolation bidirectional charge-discharge converter to charge the energy storage equipment; for the output alternating current filter capacitor and the alternating current load, the output ends of the switch voltage type single-stage multi-input low-frequency link inverter and the single-stage isolation bidirectional charge-discharge converter are connected in series and simultaneously selected and connected in parallel, which is equivalent to the parallel superposition of two alternating current sources; the method comprises the steps that 1, 2, … and n paths of input source output currents are subjected to error amplification with 1, 2, … and n paths of input source maximum power point reference currents respectively, 1, 2, … and n paths of error amplification signals are multiplied by sinusoidal synchronous signals and then are intersected with the same high-frequency carrier signal respectively to generate 1, 2, … and n paths of signal control n input inverters, the n input inverters output alternating current filter inductive currents which are in the same frequency and the same phase as output voltages and output active power, and the difference theta between the output alternating current filter inductive currents of a charge-discharge converter controlled by the error amplification signals of the system output voltages and the reference voltages and the high-frequency carrier signals is intersected with the high-frequency carrier signals to generate SPWM signals, wherein the difference theta between the output alternating current filter inductive currents and the system output voltages is different in size and direction, and the difference theta means that; when the alternating current load power is equal to the sum of the maximum powers of the n input sources, theta is equal to 90 degrees, the active power output by the charging and discharging converter is zero, when the alternating current load power is larger than the sum of the maximum powers of the n input sources, the output voltage is reduced, theta is smaller than 90 degrees, the charging and discharging converter outputs active power, namely insufficient power required by the alternating current load is provided by the energy storage device, when the alternating current load power is smaller than the sum of the maximum powers of the n input sources, the output voltage is increased, theta is larger than 90 degrees, and the charging and discharging converter outputs negative active power, namely residual power output by the n input sources to.
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Application publication date: 20180511 Assignee: Shenzhen Growatt New Energy Technology Co.,Ltd. Assignor: QINGDAO University Contract record no.: X2023980033813 Denomination of invention: Series Simultaneous Selection Switching Voltage Type Single Stage Multiple Input Low Frequency Link Inverter Granted publication date: 20201013 License type: Common License Record date: 20230320 |