CN108054946B - Voltage type single-stage multi-input low-frequency link inverter with built-in parallel time-sharing selection switch - Google Patents

Voltage type single-stage multi-input low-frequency link inverter with built-in parallel time-sharing selection switch Download PDF

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CN108054946B
CN108054946B CN201810019207.1A CN201810019207A CN108054946B CN 108054946 B CN108054946 B CN 108054946B CN 201810019207 A CN201810019207 A CN 201810019207A CN 108054946 B CN108054946 B CN 108054946B
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CN108054946A (en
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陈道炼
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Qingdao University
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Qingdao University
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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
    • H02M7/493—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 the static converters being arranged for operation in parallel
    • H02J3/382—
    • H02J3/387—
    • 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
    • H02M7/501—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
    • 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
    • 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
    • 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
    • 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

Abstract

The invention relates to a voltage type single-stage multi-input low-frequency link inverter with a built-in parallel time-sharing selection switch, which is structurally characterized in that a multi-input single-output high-frequency inverter circuit with a built-in parallel time-sharing selection four-quadrant power switch is formed by connecting a plurality of common-ground input filters and a common output low-frequency isolation variable-voltage filter circuit, each input end of the multi-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 multi-input single-output high-frequency inverter circuit is connected with the input end of the output low-frequency isolation variable-voltage filter circuit. The inverter has the characteristics of common-ground and time-sharing power supply of multiple input sources, low-frequency isolation of output and input, common-output low-frequency voltage transformation and filtering circuit, simple circuit topology, single-stage power conversion, high conversion efficiency, small output voltage ripple, wide application prospect and the like, and lays a key technology for a large-capacity distributed power supply system for realizing combined power supply of multiple new energy sources.

Description

Voltage type single-stage multi-input low-frequency link inverter with built-in parallel time-sharing selection switch
Technical Field
The invention relates to a built-in parallel time-sharing 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 built-in parallel time-sharing selection switch voltage type single-stage multi-input low-frequency link inverter which has the characteristics of multiple new energy sources combined power supply, common ground of input direct-current power supplies, built-in parallel time-sharing selection switches of a multi-input single-output high-frequency inverter circuit, low-frequency isolation between output and input, time-sharing power supply in one switching period of multiple input power supplies, simple circuit topology, shared output low-frequency transformer filter circuits, 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 voltage type single-stage multiple-input low-frequency link inverter with built-in parallel time-sharing selection switch is composed of a multiple-input single-output high-frequency inverter circuit consisting of multiple input filters connected to the same ground and a shared output low-frequency isolation and transformation filter circuit, multiple-input single-output high-frequency inverter circuit with each input end connected to the output end of each input filter, multiple-input single-output high-frequency inverter circuit with its output end connected to the input end of low-frequency transformer or the input end of output filter, multiple-input single-output high-frequency inverter circuit consisting of multiple built-in parallel time-sharing selection four-quadrant power switch bidirectional power flow single-input single-output high-frequency inverter circuit, and one bidirectional power flow single-input single-output high-frequency inverter circuit, the output low-frequency isolation voltage transformation filter circuit is formed by sequentially cascading a low-frequency transformer and an output filter or an output filter inductor, a low-frequency transformer and an output filter capacitor or an output filter and a low-frequency transformer.
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 with a built-in parallel time-sharing selection switch, and provides a voltage type single-stage multi-input low-frequency link inverter circuit structure with a topology family and an energy management control strategy thereof, namely the circuit structure is formed by connecting a plurality of common-ground input filters and a common output low-frequency isolation voltage-transformation filter circuit through a multi-input single-output high-frequency inverter circuit with a built-in parallel time-sharing selection four-quadrant power switch.
The voltage type single-stage multi-input low-frequency link inverter with the built-in parallel time-sharing selection switch can invert a plurality of common-ground unstable input direct-current voltages into stable and high-quality output alternating-current power required by a load, and has the characteristics of common-ground of a multi-input direct-current power supply, no isolation between multi-input single-output high-frequency inverter circuits, low-frequency isolation between output and input, time-sharing power supply within one switching period of the multi-input power supply, simple circuit topology, common output low-frequency transformer filter circuits, single-stage power conversion, high conversion efficiency, small output voltage ripple, large output capacity, wide application prospect and the like. The comprehensive performance of the built-in parallel time-sharing 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 voltage type single-stage multi-input low-frequency link inverter with a built-in parallel time-sharing selection switch.
Fig. 5 is a circuit structure diagram of a voltage type single-stage multi-input low-frequency link inverter with a built-in parallel time-sharing selection switch.
Fig. 6 is a steady-state schematic waveform diagram of a voltage type single-stage multi-input low-frequency link inverter with built-in parallel time-sharing selection switches controlled by a bipolar SPWM.
Fig. 7 is a steady-state schematic waveform diagram of a unipolar SPWM controlled voltage type single-stage multiple-input low-frequency link inverter with built-in parallel time-sharing selection switches.
Fig. 8 is a schematic diagram of a push-pull circuit, which is a circuit topology example of a voltage type single-stage multi-input low-frequency link inverter with a built-in parallel time-sharing selection switch.
Fig. 9 is a schematic diagram of a circuit topology example of a built-in parallel time-sharing 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 voltage type single-stage multi-input low-frequency link inverter with a built-in parallel time-sharing selection switch.
Fig. 11 is a schematic diagram ii of a four-half bridge circuit of a circuit topology example of a voltage type single-stage multiple-input low-frequency link inverter with a built-in parallel time-sharing selection switch.
Fig. 12 is a schematic diagram iii of a five-half bridge circuit of a circuit topology example of a voltage type single-stage multiple-input low-frequency link inverter with a built-in parallel time-sharing selection switch.
Fig. 13 is a six-full bridge circuit schematic diagram i of a circuit topology example of a voltage type single-stage multiple-input low-frequency link inverter with a built-in parallel time-sharing selection switch.
Fig. 14 is a seven-full bridge circuit schematic diagram ii of a circuit topology example of a voltage type single-stage multiple-input low-frequency link inverter with a built-in parallel time-sharing selection switch.
Fig. 15 is a schematic diagram iii of a circuit topology example eight-full bridge type circuit of a voltage type single-stage multiple-input low-frequency link inverter with a built-in parallel time-sharing selection switch.
Fig. 16 is a master-slave power distribution energy management control block diagram of a voltage type single-stage multiple-input low-frequency link inverter with a built-in parallel time-sharing selection switch, in which instantaneous values of output voltage and input current 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 dual-polarity SPWM fed back by instantaneous values of output voltage and input current of a built-in parallel time-sharing 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 single-polarity SPWM feedback by an instantaneous value of output voltage and input current of a built-in parallel time-sharing 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 built-in parallel time-sharing selection switch voltage type single-stage multiple-input low-frequency link inverter.
Fig. 20 shows a built-in parallel time-sharing selective switch voltage type single-stage multiple-input low-frequency link independent power supply system with an output end connected with a single-stage isolation bidirectional charge-discharge converter in parallel.
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 voltage type single-stage multi-input low-frequency link inverter with built-in parallel time-sharing selection switch is formed by connecting a plurality of input filters which are in common with the ground with a common output low-frequency isolation and transformation filter circuit through a multi-input single-output high-frequency inverter circuit, wherein each input end of the multi-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 multi-input single-output high-frequency inverter circuit is connected with the input end of a low-frequency transformer of the output low-frequency isolation and transformation filter circuit or the input end of an output filter inductor which is not connected with a low-frequency transformer or the input end of an output filter, the multi-input single-output high-frequency inverter circuit is formed by a plurality of bidirectional power flow single-input single-output high-frequency inverter circuits which are internally provided with four quadrant power switches which are in, the output low-frequency isolation voltage transformation filter circuit is formed by sequentially cascading a low-frequency transformer and an output filter or an output filter inductor, a low-frequency transformer and an output filter capacitor or an output filter and a low-frequency transformer.
Schematic block diagrams, circuit structures, stable-state principle waveforms of the built-in parallel time-sharing selection switch voltage type single-stage multi-input low-frequency link inverter, bipolar SPWM control inverter and unipolar SPWM control inverter are respectively shown in FIGS. 4, 5, 6 and 7. 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 output AC loads (including single-phase AC passive loads and single-phase AC grid loads), uo、ioRespectively single-phase output alternating voltage and alternating current. The n-input single-output high-frequency inverter circuit is composed of a plurality of built-in bidirectional power flow single-input single-output high-frequency inverter circuits connected in parallel and selecting four-quadrant power switches in a time-sharing manner; the n-input single-output high-frequency inverter circuit is realized by a plurality of four-quadrant high-frequency power switches capable of bearing bidirectional voltage stress and bidirectional current stress and one or more two-quadrant high-frequency power switches capable of bearing unidirectional voltage stress and bidirectional current stress, or only by a plurality of four-quadrant high-frequency power switches capable of bearing bidirectional voltage stress and bidirectional current stress, and power devices such as MOSFET (metal-oxide-semiconductor field effect transistor), IGBT (insulated gate bipolar transistor), GTR (ground turn-to-turn ratio) and the like can be selected; the output low-frequency isolation transformation filter circuit in the virtual frame (the '1' end and the '1' end 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 inductor, the output filter capacitor and the low-frequency transformer, only the circuit diagram of the LC output filter or the output filter capacitor suitable for the passive alternating-current load is drawn in the space diagram, but the circuit diagram of the LCL output filter suitable for the alternating-current power grid load or the electric quantity added with the output filter inductor after the output filter capacitor is not drawnA road map; 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 into multi-level SPWM voltage wave with amplitude changing with input DC voltage, passing through low-frequency transformer T and 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 input pulse currents of n-input single-output high-frequency inverter circuit are input to a 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 and single-polarity three-state multi-level SPWM voltage wave uABThe +1 state amplitude is Ui1N2/N1、Ui2N2/N1、…、UinN2/N1And the-1 state amplitude is UinN2/N1(here, it is designed to pass only the nth input source UinThe energy at the alternating current side is fed back, and the energy at the alternating current side can also be designed to be fed back through any other input source); 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 inductor, an output filter capacitor and a low-frequency transformerTime-lapse, bipolar two-state and unipolar three-state multi-level SPWM voltage wave uABThe +1 state amplitude is Ui1、Ui2、…、UinAnd the-1 state amplitude is Uin(here, it is designed to pass only the nth input source UinThe energy on the alternating current side can be fed back through any other input source).
A voltage type single-stage multi-input low-frequency link inverter with a built-in parallel time-sharing selection switch belongs to a voltage reduction type inverter, and n input sources supply power to a load in a parallel 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. m1、 m2、…、mnLess 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+(m2-m1)Ui2+…+(mn-mn-1)Uin)]N2/N1(unipolar SPWM control) or uo＝[(2m1-1)Ui1+(2m2-2m1-1)Ui2+…+(2mn-2mn-1-1)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-m1)+…+(mn-mn-1) < 1 (unipolar SPWM control) and 0.5 < m1+(m2-m1)+…+(mn-mn-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 multi-path parallel time-sharing selection four-quadrant power switch is positioned in a high-frequency inverter circuit, so the inverter is called a built-in parallel time-sharing selection switch voltage type (voltage reduction type) single-stage multi-input low-frequency link inverter. The n input sources of the inverter can only supply power to the output alternating current load in a time-sharing way in one high-frequency switching period, and the modulation degrees can be the same (m1＝m2＝…＝mn) Or may be different (m)1≠m2≠…≠mn)。
The voltage type single-stage multi-input low-frequency link inverter with the built-in parallel time-sharing selection switch has essential difference from the circuit structure of the traditional multi-input inverter formed by two-stage cascade of a direct current converter and an inverter because the inverter shares a multi-input single-output high-frequency inverter circuit and an output low-frequency isolation variable-voltage filter circuit. Therefore, the inverter provided by the invention has novelty and creativity, and has the advantages of low-frequency isolation of output and input, time-sharing power supply 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 situation of vigorously advocating the construction of energy-saving and conservation society today.
An embodiment of a circuit topology family of a voltage type single-stage multi-input low-frequency link inverter with a built-in parallel time-sharing selection switch is shown in fig. 8, 9, 10, 11, 12, 13, 14 and 15. The push-pull circuit shown in fig. 8 is implemented by 2n four-quadrant high-frequency power switches capable of bearing bidirectional voltage stress and bidirectional current stress, the push-pull forward circuit shown in fig. 9 and the half-bridge circuit shown in fig. 10, 11 and 12 are implemented by 2n four-quadrant high-frequency power switches capable of bearing bidirectional voltage stress and bidirectional current stress and 1 two-quadrant high-frequency power switch capable of bearing unidirectional voltage stress and bidirectional current stress, and the full-bridge circuit shown in fig. 13, 14 and 15 is implemented by 2n four-quadrant high-frequency power switches capable of bearing bidirectional voltage stress and bidirectional current stress and 2 two-quadrant high-frequency power switches capable of bearing unidirectional voltage stress and bidirectional current stress. It should be noted 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 (the input filter capacitance of the half-bridge circuit shown in fig. 10, 11, and 12 is two bridge arm capacitances C)1、C2) The circuit is not given in space when the input filter is a capacitive filter; the circuits shown in fig. 9, 10, 11, 12, 13, 14 and 15 do not need to all adopt four-quadrant high-frequency power switches, and 1 or 2 two-quadrant high-frequency power switches are omitted; the push-pull forward circuit of fig. 9 and the half-bridge circuits of fig. 10, 11 and 12 are only suitable for use where the n input supply voltages 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 and a low-frequency transformer; output low-frequency isolation voltage-transformation filter circuit of full-bridge circuits I, II and III shown in FIGS. 13, 14 and 15The low-frequency transformer, the output filter inductor, the low-frequency transformer, the output filter capacitor, the output filter and the low-frequency transformer are sequentially cascaded to form the low-frequency transformer, the output filter, the low-frequency transformer and the output filter capacitor. The power switch voltage stress of four topological embodiments of the built-in parallel time-sharing selection switch voltage type single-stage multi-input low-frequency link inverter is shown in table 1. In Table 1, Uimax＝max(Ui1，Ui2，…，Uin). 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 common-ground unstable input direct-current voltages into a stable and high-quality output alternating current with a required voltage, and can be used for realizing a novel single-stage multiple 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 24-36-48VDC/220V50HzAC or115V400HzAC, large wind power generation 510VDC/220V50HzAC or115V400HzAC and other multiple input sources for supplying power to alternating current loads or alternating current power grids.
Table 1 built-in parallel time-sharing selection switch voltage type single-stage multiple-input low-frequency link inverter four topology embodiments of power switch voltage stress
Figure BDA0001543007080000071
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 built-in parallel time-sharing 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 voltage type single-stage multi-input low-frequency link inverter with the built-in parallel time-sharing selection switch 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.
A voltage type single-stage multi-input low-frequency link inverter with a built-in parallel time-sharing selection switch adopts a master-slave power distribution energy management control strategy of feeding back bipolar SPWM and unipolar SPWM by output voltage and input current instantaneous values 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. Input current feedback signal I of inverter 1 st, 2 nd, … th and n-1 th pathsi1f、Ii2f、…、Ii(n-1)fRespectively obtaining reference current signals I after maximum power point calculation with the 1 st, 2 nd, … th and n-1 th input sourcesi1r、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 urThe error signal u is amplified and compared by a proportional-integral regulatoreObtaining 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 switchgs11、ugs21、…、ugsn1、ugs12、ugs22、…、ugsn2、ugs′11、ugs′21、…、ugs′n1、ugs′12、ugs′22、…、 ugs′n2、ugs3、ugs4. The 1 st, 2 nd, … th and n-1 th circuit current regulators and the n-1 th circuit voltage regulator work independently respectively, the 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 circuit input sources, the n-1 th circuit voltage regulator is used for realizing the stabilization of the output voltage of the inverter, and the n-1 th circuit input sources jointly supply power to a load. By regulating the reference voltage u as the input voltage or load variesrAnd a reference current ii1r、ii2r、…、ii(n-1)rOr regulating the feedback voltage uofAnd a feedback current ii1f、ii2f、…、ii(n-1)fTo 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 input source in fig. 16-19 is designed as input current feedback to control the input current, the input current transient is formedAnd a time value feedback bipolar SPWM and unipolar SPWM maximum power output energy management control strategy. 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 switchgs11、ugs21、…、ugsn1、ugs12、ugs22、…、ugsn2、ugs′11、ugs′21、…、ugs′n1、ugs′12、ugs′22、…、 ugs′n2、ugs3、ugs4. The 1 st, 2 nd, … th circuit current regulators and the n-th circuit current regulators respectively work independently and are all used for realizing the maximum power output of respective input sources, and the n-th circuit input sources jointly supply power to a load.
The waveform of the bipolar and unipolar SPWM control principle shown in FIGS. 17 and 19 marks the high-frequency switching period TSAnd a certain high frequency switching period TSConduction time T of internal 1 st, 2 nd, … th input sourceon1、Ton2、…、TonnAnd total on-time Ton＝Ton1+Ton2+…+TonnTotal on-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.
To form an independent system capable of fully utilizing energy of multiple input sourcesIn the power supply system, a plurality of input sources should operate in a maximum power output mode and energy storage equipment needs to be configured to achieve the stabilization of output voltage, that is, a single-stage isolation bidirectional charge-discharge converter is connected in parallel to the output end of the 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+…+PnmaxAnd in the time, the residual energy output by the plurality of input sources is used for charging the energy storage equipment through the single-stage isolation bidirectional charging and discharging converter, namely, the 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 voltage type single-stage multi-input low-frequency link inverter and the output end of the single-stage isolation bidirectional charge-discharge converter with the built-in parallel time-sharing selection switch is equivalent to the parallel connection superposition of two current sources. From FIG. 21The shown energy management control strategy shows that the output filter inductive current i of the voltage type single-stage multi-input low-frequency link inverter with the built-in parallel time-sharing selection switchLfAnd 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 different phase differences theta mean 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. A voltage type single-stage multi-input low-frequency link inverter with a built-in parallel time-sharing selection switch is characterized in that: the inverter is formed by sequentially cascading a bidirectional power flow n-input single-output high-frequency inverter circuit and an output low-frequency isolation transformation filter circuit which are internally provided with parallel time-sharing selection switches, each input end of the bidirectional power flow n-input single-output high-frequency inverter circuit which is internally provided with the parallel time-sharing selection switches is respectively cascaded with an input filter, and the n input filtersThe wave filter is grounded, n is the path number of the multi-input source, and n is a natural number more than 1; the bidirectional power flow n input single output high-frequency inverter circuit internally provided with the parallel time-sharing selection switch is composed of n paths of parallel time-sharing selection bidirectional power flow four-quadrant power switch circuits and bidirectional power flow two-quadrant power switches, or is only composed of n paths of parallel time-sharing selection bidirectional power flow four-quadrant power switch circuits, and is equivalent to a bidirectional power flow single input single output high-frequency inverter circuit with only one path of parallel time-sharing selection four-quadrant power switch working at any moment; the n paths of drains on one side of the n paths of parallel time-sharing selection bidirectional power flow four-quadrant power switch circuits are connected with the output ends of the n paths of input filters in a one-to-one correspondence mode, the n paths of drains on the other side of the n paths of parallel time-sharing selection bidirectional power flow four-quadrant power switch circuits are connected into a common drain end in a parallel mode, and each path of parallel time-sharing selection bidirectional power flow four-quadrant power switch circuit is only formed by reversely connecting two quadrant power; the output low-frequency isolation transformation filter circuit is formed by a low-frequency transformer and an output filter, or by an output filter inductor containing a primary side leakage inductor of the low-frequency transformer, the low-frequency transformer and an output filter capacitor, or by sequentially cascading the output filter and the low-frequency transformer; the bidirectional power flow n input single output high-frequency inverter circuit with built-in parallel time-sharing selection switch is of a push-pull type, push-pull forward type, half bridge type and full bridge type structure, the push-pull type circuit is composed of two n paths of parallel time-sharing selection bidirectional power flow four-quadrant power switch circuits, n paths of drains of two non-common drain terminals are respectively connected with the output ends of n paths of input filters in a one-to-one correspondence manner, two common drain terminals are connected with two ends of a primary winding of a low-frequency transformer, a center tap of a primary winding of the low-frequency transformer is connected with a negative end of n paths of input sources, the push-pull forward type circuit is composed of two n paths of parallel time-sharing selection bidirectional power flow four-quadrant power switch circuits, a two-quadrant power switch and a clamping capacitor, the n paths of drains of the two non-common drain terminals are respectively connected with the output ends of the n paths of input filters in a one-to-one correspondence The source and drain of the two-quadrant power switch are respectively connected with the non-end of one primary winding and the end of the other primary winding of the low-frequency transformer and the two-quadrant power switch are connected with each otherThe source electrode is connected with the negative end of n paths of input sources, the two ends of a clamping capacitor are respectively connected with the "·" ends of two primary windings of the low-frequency transformer, the half-bridge circuit is composed of two n paths of parallel time-sharing selection bidirectional power flow four-quadrant power switch circuits, a two-quadrant power switch and two bridge arm capacitors, the n paths of drain electrodes of two non-common drain ends are respectively connected with the output ends of n paths of input filter inductors in a one-to-one correspondence manner, the two common drain ends are respectively connected with the positive end of a left upper bridge arm capacitor and one input end of an output low-frequency isolation transformation filter circuit, the drain electrodes and the source electrodes of the two-quadrant power switches are respectively connected with one input end of the output low-frequency isolation transformation filter circuit and the negative end of the n paths of input sources, the positive end of the left lower bridge arm capacitor and the, The negative polarity end of the capacitor of the left lower bridge arm is connected with the negative polarity end of n paths of input sources, the full-bridge circuit is composed of two n paths of parallel connection time-sharing selection bidirectional power flow four-quadrant power switch circuits and two-quadrant power switches, the n paths of drain electrodes of two non-common drain terminals are correspondingly connected with the output end of the n paths of input filters one by one, the two common drain terminals and the drain electrodes of the two-quadrant power switches are respectively connected with the two input ends of the output low-frequency isolation voltage-transformation filter circuit, and the source electrodes of the two-quadrant power switches are connected with the negative polarity end of the n paths; the n-input single-output high-frequency inverter circuit of the multi-input low-frequency link inverter inputs n paths of source voltage Ui1、Ui2、…、UinModulating to a bipolar two-state or unipolar three-state multi-level SPWM voltage wave with amplitude changing along with input source voltage, outputting a low-frequency isolation voltage-transformation filter circuit, and obtaining high-quality sinusoidal alternating-current voltage or sinusoidal grid-connected current on a single-phase alternating-current load, wherein the + 1-state amplitudes of the bipolar two-state and unipolar three-state multi-level SPWM voltage wave are both Ui1N2/N1、Ui2N2/N1、…、UinN2/N1Or Ui1、Ui2、…、UinThrough the n-th input source UinThe amplitude value of-1 state is U when the energy of the AC side is fed backinN2/N1Or UinThe amplitude of each level of the +1 state and-1 state of the multi-level SPWM voltage wave of the half-bridge circuit is multiplied by a coefficient 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; output voltage u of multi-input low-frequency link inverter controlled by unipolar SPWM and bipolar SPWMoWith multiple input source voltage, low frequency transformer turn ratio, multiple input source modulation degree m1、m2、…、mnThe relationship between each other is uo＝[(m1Ui1+(m2-m1)Ui2+…+(mn-mn-1)Uin)]N2/N1、uo＝[(2m1-1)Ui1+(2m2-2m1-1)Ui2+…+(2mn-2mn-1-1)Uin]N2/N1，0≤m1＜m2＜…＜mn1, only each item of the half-bridge circuit should be multiplied by a coefficient 1/2; voltage stress difference U of n-path parallel time-sharing selection four-quadrant power switch of push-pull circuiti1+Uimax、Ui2+Uimax、…、Uin+UimaxThe voltage stress of the n-path parallel time-sharing selection four-quadrant power switch of the push-pull forward circuit is respectively Ui1+Uimax、Ui2+Uimax、…、Uin+UimaxAnd max | UiN-Ui1∣、max∣UiN-Ui2∣、…、max∣UiN-UinThe voltage stress of the | and two-quadrant power switch is 2UimaxThe voltage stress of n-path parallel time-sharing selection four-quadrant power switch of the half-bridge circuit is max | UiN-Ui1∣、max∣UiN-Ui2∣、…、max∣UiN-Uin| and Ui1、Ui2、…、UinAnd the voltage stress of the two-quadrant power switch is UimaxThe voltage stress of the n-path parallel time-sharing selection four-quadrant power switch and the voltage stress of the two-quadrant power switch of the full-bridge circuit are respectively Ui1、Ui2、…、UinAnd Uimax，Uimax＝max(Ui1，Ui2，…，Uin) N is 1, 2, …, N; 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 sources needing to be put into operation by controlling the on and off of n paths of built-in parallel time-sharing selection four-quadrant power switches according to the size of an alternating current load, wherein the n paths of input sources are U-shaped in a high-frequency switching periodi1、Ui2、…、UinThe power is supplied to the AC load in parallel connection in sequence and time sharing, so that the single-stage low-frequency isolation high-efficiency inversion of n common-ground unstable input DC voltages into stable high-quality sinusoidal AC power required by the AC load is realized.
2. The built-in parallel time-sharing selection switch voltage type single-stage multi-input low-frequency link inverter according to claim 1, characterized in that: the output end of the built-in parallel time-sharing 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 n paths of input source direct current electric energy into alternating current electric energy through the built-in parallel time-sharing selection 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 n input sources, the system works in a power supply mode II that the energy storage device 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 device 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 n input sources, the system works in a power supply mode I that the residual energy output by the n input sources is converted to charge the energy storage device in two stages through a built-in parallel connection time-sharing selection switch voltage type single-stage multiple input low-frequency link inverter and the; for the output alternating current filter capacitor and the alternating current load, the output ends of the built-in parallel connection time-sharing selection switch voltage type single-stage multi-input low-frequency link inverter and the single-stage isolation bidirectional charge-discharge converter are connected in parallel and are equivalent to the parallel connection 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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