CN108199603B - Multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter - Google Patents

Abstract

The invention relates to a multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter. The input filter is connected with a common output filter circuit, and each input end of the combined multi-input single-output isolated bidirectional flyback DC chopper is connected with the output end of each input filter in a one-to-one correspondence, and the output end is connected to the output end. connected to the filter circuit. This inverter has multiple input source electrical isolation, time-sharing power supply, output and input electrical isolation, simple circuit topology, single-stage power conversion, high power density, high conversion efficiency, high reliability when the load is short-circuited, and small output capacity. The characteristics of wide application prospects and other characteristics have laid a key technology for realizing a small-capacity distributed power supply system with multiple new energy combined power supply.

Description

Multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter

technical field

The multi-winding time-sharing power supply isolation flyback DC chopper type single-stage multi-input inverter involved in the invention belongs to the power electronic conversion technology.

Background technique

The inverter is a static converter device that uses power semiconductor devices to convert an unstable and inferior DC power into stable, high-quality AC power for use by AC loads or to achieve AC grid connection. Inverters with low-frequency electrical isolation or high-frequency electrical isolation between the output AC load or the AC grid and the input DC power supply are called low-frequency link and high-frequency link inverters respectively. The electrical isolation element mainly plays the following roles in the inverter: (1) realizes the electrical isolation between the output and input of the inverter, and improves the safety, reliability and electromagnetic compatibility of the inverter operation; (2) realizes the The matching between the output voltage of the inverter and the input voltage is achieved, that is, the technical effect that the output voltage of the inverter is higher than, equal to or lower than the input voltage is realized, and its application scope has been greatly broadened; (3) When the transformer or storage When the working frequency of the energy transformer is above 20kHz, its volume and weight are greatly reduced, and the audio noise is also eliminated. Therefore, the inverter has important application value in secondary electric energy conversion occasions with DC generators, batteries, photovoltaic cells and fuel cells as the main DC power sources.

New energy (also called green energy) such as solar energy, wind energy, tidal energy and geothermal energy has the advantages of clean, non-polluting, cheap, reliable and abundant, so it has a wide range of application prospects. Due to the increasing tension of traditional fossil energy (non-renewable energy) such as oil, coal and natural gas, serious environmental pollution, global warming, and the production of nuclear energy will produce nuclear waste and pollute the environment, the development and utilization of new energy is increasingly more and more attention. New energy power generation mainly includes photovoltaics, wind power, fuel cells, hydropower, geothermal and other types, all of which have shortcomings such as unstable, discontinuous, and climatic changes in power supply.

The traditional new energy distributed power supply system is shown in Figures 1 and 2. The system usually uses multiple single-input DC converters to convert photovoltaic cells, fuel cells, wind turbines, and other new energy power generation equipment that do not require energy storage through a one-way DC converter respectively. It is then connected to the DC bus of the public inverter to ensure that various new energy sources are jointly supplied and can work in harmony. The distributed generation system realizes the simultaneous supply of power to the load and the preferential utilization of energy from multiple input sources, which improves the stability and flexibility of the system, but has the defects of two-stage power conversion, low power density, low conversion efficiency, and high cost. Its usefulness is greatly limited.

In order to simplify the circuit structure and reduce the number of power conversion stages, it is necessary to replace the two-stage cascaded circuit structure with a DC converter and an inverter shown in Figures 1 and 2 with a new multi-input inverter with a single-stage circuit structure shown in Figure 3 The traditional multi-input inverter constitutes a new single-stage new energy distributed power supply system. Single-stage multi-input inverters allow a variety of new energy inputs, and the nature, amplitude and characteristics of the input sources can be the same or very different. The new single-stage new energy distributed power supply system has the advantages of simple circuit structure, single-stage power conversion, multiple input sources supply power to the load at the same time or time-sharing within a high-frequency switching cycle, and low cost.

Therefore, it is extremely urgent to actively seek a class of single-stage multi-input inverters and their new energy distributed power supply systems that allow a variety of new energy sources to jointly supply power. Utilization will be of great significance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a multi-input and single-output energy storage transformer with a multi-input single-output energy storage transformer, a combined multi-input single-output isolated bidirectional flyback DC chopper, and a multi-input single-output energy storage transformer with multiple new energy combined power supply, mutual isolation of input DC power sources, and mutual isolation of input DC power sources. The multi-winding time-sharing power supply isolation has the characteristics of electrical isolation, multiple input power supply time-sharing power supply to the load, simple circuit topology, single-stage power conversion, high conversion efficiency, high reliability when the load is short-circuited, small output capacity, and wide application prospects. Flyback DC chopper type single-stage multi-input inverter.

The technical scheme of the present invention is: a multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter, which is composed of a combined multi-input single-output isolated bidirectional flyback DC chopper The isolated input filter is connected with a common output filter circuit. The output end of the multi-input single-output isolated bidirectional flyback DC chopper is connected with the output filter circuit; the combined multi-input single-output isolated bidirectional flyback DC chopper is composed of two identical, respectively outputting low-frequency positive half cycles Each input terminal of the multi-input single-output isolated bidirectional flyback DC chopper with low-frequency negative half-cycle unipolar pulse width modulation current wave is formed in reverse series with each input terminal corresponding to the parallel output terminal, and two multi-input single-output isolated bidirectional The two non-series output terminals of the flyback DC chopper are the output terminals of the combined multi-input single-output isolated bidirectional flyback DC chopper; each of the multi-input single-output isolated bidirectional flyback DC choppers is a A high-frequency rectifier composed of a multi-input single-output energy storage transformer that converts multiple mutually isolated bidirectional power flow single-input single-output high-frequency inverter circuits and a shared rectifier and polarity selection with two-quadrant high-frequency power switches Connection structure, each input end of the multi-input single-output energy storage transformer is connected with the output end of each high-frequency inverter circuit in a one-to-one correspondence, and the output end of the multi-input single-output energy storage transformer is connected with the input end of the high-frequency rectifier. The input end of each of the high-frequency inverter circuits is the input end of the combined multi-input single-output isolated bidirectional flyback DC chopper, and each of the high-frequency inverter circuits The circuits are all composed of four-quadrant high-frequency power switches and two-quadrant high-frequency power switches or only four-quadrant high-frequency power switches. constitute.

The invention is a multi-input inverter circuit structure formed by cascading the DC converter and the inverter of the traditional multiple new energy combined power supply system in two stages, and constructs a new single-stage multi-input inverter with multi-winding time-sharing power supply. The circuit structure of the multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter circuit structure and topology family and its energy management control strategy are proposed. The single output isolated bidirectional flyback DC chopper is formed by connecting multiple mutually isolated input filters and a common output filter circuit.

The multi-winding time-sharing power supply isolation flyback DC chopper type single-stage multi-input inverter of the present invention can invert multiple mutually isolated and unstable input DC voltages into stable and high-quality output AC power required by a load, It has multi-input DC power mutual isolation, output and input electrical isolation, multi-input power supply time-sharing power supply to the load, simple circuit topology, single-stage power conversion, high conversion efficiency, wide input voltage variation range, high reliability under load overload and short circuit , small output capacity, wide application prospects and so on. The comprehensive performance of the multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter will be superior to the traditional multi-input inverter composed of two-stage cascaded DC converters and inverters.

Description of drawings

Figure 1, a traditional two-stage new energy distributed power supply system with parallel output terminals of multiple unidirectional DC converters.

Figure 2, a traditional two-stage new energy distributed power supply system with multiple unidirectional DC converter outputs connected in series.

Figure 3, the principle block diagram of the new single-stage multi-input inverter.

Figure 4, the principle block diagram of the multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter.

Figure 5, the circuit structure diagram of the multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter.

Figure 6, the steady-state principle waveform diagram of the single-stage multi-input inverter of the single-stage multi-input inverter controlled by the SPWM control of the multi-winding time-sharing power supply isolated by the instantaneous value of the output voltage.

Figure 7, Multi-winding time-sharing power supply isolated flyback DC chopper type circuit topology example 1 ---- single-tube flyback DC chopper circuit schematic diagram.

Figure 8, Multi-winding time-sharing power supply isolated flyback DC chopper circuit topology example 2 ---- double-tube flyback DC chopper circuit schematic diagram.

Figure 9, multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter circuit topology example 3-parallel interleaved single-tube flyback DC chopper circuit schematic diagram.

Figure 10, Multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter circuit topology example IV - Schematic diagram of the parallel interleaved double-tube flyback DC chopper type circuit.

Figure 11, the multi-winding time-sharing power supply single-tube and double-tube isolated flyback DC chopper type single-stage multi-input inverter output voltage, input current instantaneous value SPWM master-slave power distribution energy management control block diagram.

Figure 12. The waveform diagram of the SPWM master-slave power distribution energy management control principle of the output voltage and input current instantaneous value of the single-tube and double-tube isolated flyback DC chopper type single-stage multi-input inverter for multi-winding time-sharing power supply.

Figure 13, multi-winding time-sharing power supply parallel staggered single-tube and parallel staggered double-tube isolated flyback DC chopper single-stage multi-input inverter output voltage, input current instantaneous value SPWM master-slave power distribution energy management control block diagram .

Figure 14. Multi-winding time-sharing power supply parallel staggered single-tube and parallel staggered double-tube isolated flyback DC chopper single-stage multi-input inverter output voltage, input current instantaneous value SPWM master-slave power distribution energy management control principle Waveform diagram.

Figure 15, a multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input independent power supply system with an output end connected to a single-stage isolated bidirectional charge-discharge converter.

Figure 16. Maximum power output energy management control strategy with a single-stage isolated bidirectional charge-discharge converter output voltage independent control loop.

Figure 17 shows the waveforms of the output voltage u _o , the output current i _Lf and the output filter inductance i _Lf ' of the independent power supply system.

Detailed ways

The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments of the specification.

The multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter is composed of a combined multi-input single-output isolated bidirectional flyback DC chopper to connect multiple mutually isolated input filters and a common The output filter circuit is connected and formed. Each input end of the combined multi-input and single-output isolated bidirectional flyback DC chopper is connected to the output end of each input filter in a one-to-one correspondence. The combined multi-input and single-output isolated bidirectional flyback DC The output end of the chopper is connected with the output filter circuit; the combined multi-input single-output isolated bidirectional flyback DC chopper is composed of two identical unipolar pulse widths that respectively output a low-frequency positive half-cycle and a low-frequency negative half-cycle Each input terminal of the multi-input single-output isolated bidirectional flyback DC chopper for modulating the current wave is composed of one-to-one corresponding parallel output terminals in reverse series, and the two multi-input single-output isolated bidirectional flyback DC choppers are not connected in series The two output terminals are the output terminals of the combined multi-input single-output isolated bidirectional flyback DC chopper; each of the multi-input single-output isolated bidirectional flyback DC chopper is composed of a multi-input single-output energy storage The multi-input single-output high-frequency inverter circuit and a common high-frequency rectifier composed of a two-quadrant high-frequency power switch for rectification and polarity selection are connected to form a multi-input single-output high-frequency power transformer. Each input end of the energy storage transformer is connected with the output end of each high-frequency inverter circuit in a one-to-one correspondence, and the output end of the multi-input single-output energy storage transformer is connected with the input end of the high-frequency rectifier; The input end of the frequency inverter circuit is each input end of the combined multi-input single-output isolated bidirectional flyback DC chopper, and each of the high-frequency inverter circuits is composed of a four-quadrant high-frequency power switch. It is composed of two-quadrant high-frequency power switches or only four-quadrant high-frequency power switches.

和-U_i1N₂/N₁₁、-U_i2N₂/N₂₁、…、-U_inN₂/N_n1，单极性三态多电平SPWM电流波i_N111(i_N211)、i_N121(i_N221)、…、i_N1n1(i_N2n1)的上升斜率分别为U_i1/L₁₁、U_i2/L₂₁、…、U_in/L_n1，单极性三态单电平SPWM电流波i_o1、i_o2的下降斜率为-u_o/L₂。The principle block diagram, circuit structure, and steady-state principle waveform of SPWM control of instantaneous value of output voltage of multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter are shown in Figures 4, 5, and 6 respectively. In Figures 4, 5, and 6, U _i1 , U _i2 , ..., U _in are n input DC voltage sources (n is a natural number greater than 1), Z _L is a single-phase output AC load, u _o , i _o are respectively Single-phase output AC voltage (including AC grid voltage) and AC current. The combined multi-input single-output isolated bidirectional flyback DC chopper consists of two identical multi-input single-output isolated bidirectional inverters that output low-frequency positive half-cycle and low-frequency negative half-cycle unipolar pulse width modulated current waves i _o1 and i _o2 respectively. Each input end of the excitation DC chopper corresponds to the parallel output end in reverse series, and the two output ends of the two multi-input single-output isolated bidirectional flyback DC chopper are not connected in series. The combined multi-input single-output The output of the isolated bidirectional flyback DC chopper, two identical multi-input single-output isolated bidirectional flyback DC choppers are respectively connected by a multi-input single-output energy storage transformer to multiple mutually isolated bidirectional power flows. The single-input single-output high-frequency inverter circuit is connected with a high-frequency rectifier composed of a two-quadrant high-frequency power switch for rectification and polarity selection. The output energy storage transformer, a common rectifier and polarity selection are composed of high-frequency rectifiers cascaded in sequence, which is equivalent to a bidirectional power flow single input single output isolated bidirectional flyback DC chopper at any time. Two identical multi-input single-output isolated bidirectional flyback DC choppers work alternately for half a low-frequency cycle within a low-frequency output voltage cycle, that is, when one DC chopper works to output i _o1 of the low-frequency positive half cycle, while the other DC The chopper stops working and the two-quadrant power switch for polarity selection is turned on, i _o2 = 0 and u _o2 = 0, after the output filter, the positive half cycle of the sinusoidal alternating current u _O and i _O is output; on the contrary, when a DC chopper The chopper works to output i _o2 of the negative half cycle of low frequency, and the other DC chopper stops working and the polarity selection uses a two-quadrant power switch to turn on, i _o1 =0 and u _o1 =0, after the output filter, the sinusoidal alternating current is output Negative half cycle of u _O , i _O . Each of the single-input single-output high-frequency inverter circuits is composed of a four-quadrant high-frequency power switch and a two-quadrant high-frequency power switch, or only four-quadrant high-frequency power switches. The high-frequency rectifier for sex selection is composed of two-quadrant high-frequency power switches, and power devices such as MOSFET, IGBT, and GTR can be selected. The output filter circuit is composed of a filter capacitor or a cascade of filter capacitors and filter inductors in sequence. The figure shows the output capacitor filter suitable for passive AC load and the output capacitor inductor filter suitable for AC grid load. The circuit diagram of this case; the n-channel input filters are LC filters (including filter _inductors L _i1 , L _i2 , _{. i2} , ..., L _in ), the n-channel input DC current will be smoother when the LC filter is used. The n-channel high-frequency inverter circuits _in each multi-input single-output isolated bidirectional flyback DC chopper respectively modulate the input DC voltage sources U _i1 , U _i2 , . Unipolar three-state multi-slope SPWM current wave i _N111 +i _N121 +…+i _N1n1 , i _N211 +i _N221 +…+i _N2n1 , isolated by energy storage transformers T ₁ , T ₂ and rectified into amplitude by high frequency rectifier The unipolar, three-state, and single-slope SPWM current waves i _o1 and i _o2 whose values are distributed according to the sinusoidal envelope can obtain high-quality sinusoidal AC voltage u _o on the single-phase AC passive load or single-phase AC power grid after outputting the filter capacitor. Or sinusoidal alternating current i _o , each n input pulse current of single-output isolated bidirectional flyback DC chopper passes through input filters L _i1 -C _i1 , L _i2 -C _i2 , ..., L _in -C _{in Or after C i1 , C i2 , .} Assuming that the effective value of the output sinusoidal voltage is U _o , the number of turns of the primary winding of the energy storage transformer is N ₁₁₁ =N ₂₁₁ =N ₁₁ , N ₁₂₁ =N ₂₂₁ =N ₂₁ ,...,N _1n1 =N _2n1 =N _n1 , _The number of _turns of the secondary winding is N ₁₂ =N ₂₂ =N ₂ , the inductances of the primary winding are L ₁₁ , L ₂₁ , . The amplitudes of the SPWM voltage waves u ₁₂ and u ₂₂ are

And -U _i1 N ₂ /N ₁₁ , -U _i2 N ₂ /N ₂₁ , ..., -U _in N ₂ /N _n1 , unipolar three-state multi-level SPWM current wave i _N111 (i _N211 ), i _N121 (i _N221 ), ..., i _N1n1 (i _N2n1 ), the rising slopes are U _i1 /L ₁₁ , U _i2 /L ₂₁ , ..., U _in /L _n1 , respectively, the unipolar three-state single-level SPWM current wave i The descending slopes of _o1 and i _o2 are -u _o /L ₂ .

Multi-winding time-sharing power supply isolation flyback DC chopper type single-stage multi-input inverter is a buck-boost inverter, and n input sources supply power to the load in a time-sharing manner. The superposition of the magnetic flux produced in the transformer or the current increment produced by the primary inductance of the energy storage transformer. Let the power selection switches S ₁₁₁ (S ₁₁₁ ′, S ₁₁₂ , S ₁₁₂ ′, S ₂₁₁ , S ₂₁₁ ′, S ₂₁₂ , S ₂₁₂ ′), S ₁₂₁ (S ₁₂₁ ′, S ₁₂₂ , S ₁₂₂ ′, S ₂₂₁ , The duty ratios of S ₂₂₁ ′, S ₂₂₂ , S ₂₂₂ ′), ..., S _1n1 (S _1n1 ′, S _1n2 , S _1n2 ′, S _2n1 , S _2n1 ′, S _2n2 , S _2n2 ′) are respectively d ₁ , d ₂ , ..., d _n , according to the increase of the magnetic flux in a high-frequency switching cycle when the high-frequency energy storage transformer is in steady state is approximately equal to the decrease of the magnetic flux, the output voltage uo and the input DC voltage (U _i1 , U _i2 , ..., U _in ), energy storage transformer turns ratio (N ₂ /N ₁₁ , N ₂ /N ₂₁ , ..., N ₂ /N _n1 ), duty cycle (d ₁ , d ₂ , ..., d _n ), that is, u _o =(d ₁ U _i1 N ₂ /N ₁₁ +d ₂ U _i2 N ₂ /N ₂₁ +…+d _n U _in N ₂ /N _n1 )/(1-d ₁ -d ₂ -…-d _n ). For appropriate duty cycles (d ₁ , d ₂ , ..., _dn ) and storage transformer turns ratios (N ₂ /N ₁₁ , N ₂ /N ₂₁ , ..., N ₂ /N _n1 ), u _o can be Greater than, equal to or less than the sum of the input DC voltages U _i1 +U _i2 +…+U _in , the energy storage transformer in the inverter not only improves the safety, reliability and electromagnetic compatibility of the inverter operation, but is more important It plays the role of matching the output voltage and the input voltage, that is, the technical effect that the output voltage of the inverter is higher than, equal to or lower than the sum of the input DC voltage U _i1 +U _i2 +…+U _in , its application The range has been greatly broadened. When 0.5<d ₁ +d ₂ +...+d _n <1 or 0<d ₁ +d ₂ +...+d _n <0.5, there are respectively u _o >U _i1 N ₂ /N ₁₁ +U _i2 N ₂ / N ₂₁ +…+U _in N ₂ /N _n1 or u _o <U _i1 N ₂ /N ₁₁ +U _i2 N ₂ /N ₂₁ +…+U _in N ₂ /N _n1 , that is, the output voltage u _o is higher than or _Below the sum of the products of the input DC voltage (U _i1 , U _i2 , . . . , U _in ) and the energy storage transformer turns ratio ₍ N ₂ /N ₁₁ , N ₂ /N ₂₁ , . _i1 N ₂ /N ₁₁ +U _i2 N ₂ /N ₂₁ +…+U _in N ₂ /N _n1 ; since the inverter belongs to a single-stage circuit structure, the output and the input are isolated by an energy storage transformer, and the combined type is more Input single output isolated bidirectional flyback DC chopper is equipped with multi-input single output energy storage transformer, so this type of inverter is called multi-winding time-sharing power supply isolated flyback DC chopper type (buck-boost type) single stage multi-input inverter. The energy storage transformer has two working modes: high frequency magnetic reset and low frequency magnetic reset. The former is that the energy storage transformer realizes the magnetic flux reset in a high frequency switching cycle. In order to avoid the reverse flow of power, it can only work in the critical CCM mode and Adopt PFM control strategy, no audio noise, it belongs to high frequency inverter; the latter is an energy storage transformer that realizes magnetic flux reset within an output low frequency cycle, works in CCM mode and constant frequency SPWM control strategy, has audio noise, Does not belong to the high frequency link inverter. The n input sources of the inverter supply power to the output AC load in time-sharing, and the duty cycle may be the same (d ₁ =d ₂ =...=d _n ) or different (d ₁ ≠d ₂ ≠...≠d _n ) .

The multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter of the present invention shares a combined multi-input single-output isolated bidirectional flyback DC chopper and an output filter circuit, which is compatible with the DC There is an essential difference in the circuit structure of the traditional multi-input inverter composed of two-stage cascaded converters and inverters. Therefore, the inverter of the present invention is novel and creative, and has the advantages of electrical isolation of output and input, time-sharing power supply of multiple input power sources, simple circuit topology, single-stage power conversion, large step-up and step-down ratio, and wide input voltage variation range. , Flexible input voltage configuration, high conversion efficiency (meaning low energy loss), high reliability under load overload and short circuit, small output capacity, low cost, wide application prospects, etc. It is an ideal energy-saving and consumption-reducing single-stage Multi-input inverters have more important value in today's vigorous advocacy of building an energy-saving and economical society.

Examples of circuit topology families of multi-winding time-sharing power supply isolation flyback DC chopper type single-stage multi-input inverters are shown in Figures 7, 8, 9, and 10. In the circuit shown in Figure 7-10, each single-input single-output high-frequency inverter circuit consists of 1-2 four-quadrant high-frequency power switches and 1-2 two-quadrant high-frequency power switches (some circuits also include power diodes) or are only composed of 1-2 four-quadrant high-frequency power switches, and a common high-frequency rectifier for rectification and polarity selection is realized by multiple two-quadrant high-frequency power switches, combined with multi-input and single-output isolation. Two multi-input single-output isolated bidirectional flyback DC choppers in the bidirectional flyback DC chopper alternately work for half a low frequency output cycle. To be precise, the single-tube flyback DC chopper circuit shown in Figure 7 is composed of 2n four-quadrant high-frequency power switches that can withstand bidirectional voltage stress and bidirectional current stress, and 4 four-quadrant high-frequency power switches that can withstand unidirectional voltage stress and bidirectional current stress. The two-quadrant high-frequency power switch for stress is realized; the double-tube flyback DC chopper type circuit shown in Figure 8 is composed of 2n four-quadrant high-frequency power switches that can withstand bidirectional voltage stress and bidirectional current stress, and 2n+4 It is realized by a two-quadrant high-frequency power switch and 4n diodes that can withstand unidirectional voltage stress and bidirectional current stress. A four-quadrant high-frequency power switch with bidirectional current stress and six two-quadrant high-frequency power switches that can withstand unidirectional voltage stress and bidirectional current stress are realized; the parallel interleaved double-tube flyback DC chopper circuit shown in Figure 10 is realized by 4n four-quadrant high-frequency power switches that can withstand bidirectional voltage stress and bidirectional current stress, 4n+6 two-quadrant high-frequency power switches that can withstand unidirectional voltage stress and bidirectional current stress, and 8n diodes. It should be supplemented that the circuit shown in Figure 7-10 shows the case where the input filter is an LC filter, and the circuit when the input filter is a capacitor filter is not given due to space limitations; the circuit shown in Figure 7-10 is only The circuit diagram of the output capacitor filter suitable for passive AC load is drawn, but the circuit diagram of the output capacitor inductor filter suitable for the AC grid load is not drawn. Table 1 shows the power switch voltage stress of the multi-winding time-sharing power supply isolation flyback DC chopper type single-stage multi-input inverter topology embodiment. In Table 1, U _N2max =max(U _i1 N ₂ /N ₁₁ , U _i2 N ₂ /N ₂₁ , . . . , U _in N ₂ /N _n1 ), and U _o is the effective value of the output sinusoidal voltage u _o . Single-tube and parallel staggered single-tube circuits are suitable for low-power and low-voltage input inverter applications, and double-tube and parallel-interleaved double-tube circuits are suitable for low-power high-voltage input inverter applications. This circuit topology family is suitable for converting multiple isolated and unstable input DC voltages into a stable and high-quality output AC power with the required voltage, which can be used to realize new single-stage multiple new energy sources with excellent performance and wide application prospects Distributed power supply system, such as photovoltaic cell 40-60VDC/220V50HzAC or 115V400HzAC, proton exchange membrane fuel cell 85-120V/220V50HzACor115V400HzAC, small and medium-sized household wind power 24-36-48VDC/220V50HzAC or 115V400HzAC, large wind power 510VDC/220V50HzAC or 115V400HzAC and other multi-input sources supply power to the AC load or AC grid.

Table 1 Voltage stress of power switch in a topology example of a multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter

Energy management and control strategies are crucial for a variety of new energy combined power supply systems. Since there are multiple input sources and corresponding power switch units, multiple duty ratios need to be controlled, that is, there are multiple control degrees of freedom, which provides the possibility for energy management of multiple new energy sources. The energy management control strategy of the multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter needs to have the energy management of the input source, the MPPT and output voltage of new energy power generation equipment such as photovoltaic cells and wind turbines. (Current) control the three major functions, and sometimes also need to consider the charge and discharge control of the battery and the smooth and seamless switching of the system under different power supply modes. The multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter adopts two different energy management modes: (1) Energy management mode I--master-slave power distribution mode, the known load required power is fully It may be provided by the 1st, 2nd, ..., n-1 input sources of the main power supply equipment. Given the input current of the 1st, 2nd, ..., n-1th input sources, it is equivalent to the given 1st, 2nd, ..., The input power of n-1 input sources, the insufficient power required by the load is provided by the nth input source from the power supply equipment, and there is no need to add battery energy storage equipment; (2) Energy management mode II - maximum power output mode, the first 1, 2, ..., n input sources all output the maximum power to the load, eliminating the need for battery energy storage equipment, and realizing the full utilization of energy by the grid-connected power generation system. If a battery charger/discharger is connected in parallel at the output end It can also realize the stability of the output voltage (current) of the independent power supply system. When the input voltages of the n new energy sources are all given, by controlling the input current of the first, second, ..., n input sources, it is equivalent to controlling the input power of the first, second, ..., n input sources.

The energy management control strategy of this type of inverter is discussed by taking the energy storage transformer to realize the magnetic flux reset in an output low frequency cycle, work in CCM mode and adopt the constant frequency SPWM control strategy as an example. Multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter adopts the SPWM master-slave power distribution energy management control strategy of the instantaneous value of output voltage and input current to form an independent power supply system; or adopts the instantaneous value of input current SPWM maximum power output energy management control strategy to form a grid-connected power generation system. The output voltage and the instantaneous value of the input current SPWM master-slave power distribution energy management control block diagram and control principle waveform , as shown in Figures 11, 12, 13, and 14, respectively. Figures 11 and 12 show the control schemes for single-pipe and double-pipe circuit topologies, and Figures 13 and 14 show the control schemes for parallel-interleaved single-pipe and parallel-interleaved double-pipe circuit topologies, which are very similar in nature. The basic idea of the control scheme is that the n-channel high-frequency inverter circuits in each multi-input single-output isolated bidirectional flyback DC chopper modulate the input DC voltage sources U _i1 , U _i2 , . . . , U _in into amplitudes respectively. Unipolar tri-state multi-slope SPWM current wave i _N111 +i _N121 +…+i _N1n1 , i _N211 +i _N221 +…+i _N2n1 , 1st, 2nd,…,n-1 The conduction time of the power switch of the high-frequency inverter circuit is obtained according to the product of the error current and the reference sinusoidal synchronization signal and the sawtooth wave intersection (to achieve the maximum power output of the 1st, 2nd, ..., n-1 input sources) , the on-time of the n-th selective power switch is obtained according to the magnitude of the error voltage and the sawtooth wave intersection (to realize the complement of the n-th input source power), the on-time of the n-th high-frequency inverter circuit power switch T _on1 , _{The sum of T on2 , .} The unipolar, three-state, and single-slope SPWM current waves i _o1 and i _o2 distributed according to the sinusoidal envelope can be filtered to obtain high-quality sinusoidal AC voltage u _o or sinusoidal AC current i _o ; it is realized by adjusting the output voltage error signal. To stabilize the inverter output voltage, this control strategy is suitable for the circuit shown in Figure 7-10. The reference current signals I ^* _i1r , I ^* _i2r , ..., I ^* _i(n-1)r are obtained after the 1st, 2nd, ..., n-1 input sources are calculated by the maximum power point. The inverter's 1st, 2nd The input current feedback signals I _i1f , I _i2f , ... , I _i(n-1)f of the , ..., n-1 channels are respectively connected with the reference current signals I _i1r , I i2r , I _i2r , ..., I _i(n-1)r are amplified by the proportional-integral regulator, and the amplified error signals I _1e , I _2e , ..., I _(n-1)e are respectively multiplied with the reference sinusoidal synchronization signal to obtain i _1e , i _2e , . . . , i _{(n-1)e and} the inverted signal _{-i 1e} , -i _2e , . ur is compared and amplified by the proportional-integral regulator to obtain the voltage error amplification signal ue, _{i 1e} , i _2e , ..., i _{(n-1)e , ue} , -i _1e , -i _2e , ..., -i _{(n -1) e} and -u _e are compared with the unipolar sawtooth carrier u _c respectively. Considering the output voltage polarity selection signal and through appropriate combinational logic circuits, the single-tube and double-tube types shown in Figures 7 and 8 are obtained. Power switch control signals of circuit topology u _gs111 (u _gs′111 ), u _gs121 (u _gs′121 ), …, u _gs1n1 (u _gs′1n1 ), u _gs211 (u _gs′211 ), u _gs221 (u _{gs '221} ), ..., _ugs2n1 ( _ugs'2n1 ), _ugs13 , _ugs23 , _ugs15 , _ugs25 or power switch control of the parallel interleaved single-tube and parallel-interleaved dual-tube circuit topologies shown in Figures 9 and 10 Signals u _gs111 (u _gs′111 ), u _gs121 (u _gs′121 ), …, u _gs1n1 (u _gs′1n1 ), u _gs112 (u _gs′112 ), u _gs122 (u _gs′122 ), …, u _gs1n2 (u _gs′1n2 ), u _gs211 (u _gs′211 ), u _gs221 (u _gs′221 ), …, u _gs2n1 (u _gs′2n1 ), u _gs212 (u _gs′212 ), u _gs222 ( _ugs'222 ), ..., _ugs2n2 ( _ugs'2n2 ), _ugs13 , _ugs14 , _ugs15 , _ugs23 , _ugs24 , _ugs25 . When the load power P _o is greater than the sum of the maximum powers of the 1st, 2, ..., n-1 input sources, the output voltage u _o decreases, and the effective value of the output voltage _ue of the voltage regulator is greater than the threshold comparison level U _{t And I 1e , I 2e} , . Work independently with the n-th voltage regulator, that is, I _i1r =I ^* _i1r , I _i2r =I ^* _i2r ,..., I _i(n-1)r =I ^* _i(n-1)r , the first, 2, ..., n-1 current regulators are used to achieve the maximum power output of the 1st, 2, ..., n-1 input sources, the nth voltage regulator is used to stabilize the output voltage of the inverter, and the nth input The source supplies power to the load in a time-sharing manner; when the load power P _o is less than the sum of the maximum powers of the 1st, 2nd, ..., n-1 input sources, the output voltage u _o increases, and when the output voltage u _e of the voltage regulator is effective When the value drops below the threshold comparison level U _t , the diode D _n-1 is turned on, D ₁ , D ₂ , ..., D _n-2 are still blocked, the hysteresis comparator circuit n+1 outputs a low level, and the nth The power supply of the 1st, 2nd, ..., n-1 input sources is time-shared to the load in one switching cycle, and the reference current of the current regulator I _i(n-1)r decreases, that is, I _i(n-1)r <I ^* _i(n-1)r , the output power of the n-1th input source decreases (working at a non-maximum operating point), and the The output power of the n-channel input source drops to zero, and the output voltage u _o of the inverter tends to be stable. When the input voltage or load changes, the error voltage signal ue and the error current signal _{i 1e} , i _2e , . . . , i _(n-1)e are changed by adjusting the reference voltage ur or the feedback voltage _{u of} to change the duty The ratio of d ₁ , d ₂ , ..., _dn , can realize the regulation and stabilization of the inverter's output voltage and input current (output power).

When the nth input source in Fig. 11-14 is designed as the input current feedback to control the input current, it constitutes the SPWM maximum power output energy management control strategy of the instantaneous value of the input current. The 1st, 2nd, ..., n-channel current regulators work independently, and are used to achieve the maximum power output of their respective input sources, and the n-channel input sources supply power to the load in a time-sharing manner.

The control principle waveforms shown in Figures 12 and 14 indicate the high-frequency switching period T _S and the on-time T _on1 , T _on2 , ... of the first, second, ..., n input sources in a certain high-frequency switching period T _S , T _onn and the total on-time of the inverter switch T _on =T _on1 +T _on2 +...+T _onn , the total on-time T _on of the inverter switch varies according to a sinusoidal law in one output voltage cycle.

When the energy is forwarded from the input DC power supply side to the output AC load side, the n turns ratio of the energy storage transformer of the double-tube type and the parallel interleaved double-tube circuit must satisfy

In order to form an independent power supply system that can make full use of the energy of multiple input sources, multiple input sources should work in the maximum power output mode and need to be equipped with energy storage devices to stabilize the output voltage, that is, connect one in parallel at the output end of the inverter. A single-stage isolated bidirectional charge-discharge converter, as shown in Figure 15. The single-stage isolated bidirectional charge-discharge converter consists of an input filter (L _i , C _i or C _i ), a high-frequency inverter, a high-frequency transformer, a cyclic converter, and an output filter (L _f ′, C _f ′). ) are cascaded in sequence, and the cycloconverter is composed of four-quadrant high-frequency power switches that can withstand bidirectional voltage stress and bidirectional current stress. The single-stage isolated bidirectional charge-discharge converter is equivalent to a single-stage high-frequency link DC-AC converter and a single-stage high-frequency link DC-AC converter when the energy is transferred forward (discharging the energy storage device) and in the reverse direction (charging the energy storage device). A single stage high frequency link AC-DC converter.

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 Figure 16. When the load power P _o =U _o I _o is greater than the sum of the maximum powers of multiple input sources P _1max +P _2max +...+P _nmax , the energy storage devices such as batteries and supercapacitors pass the single-stage isolation bidirectional charge-discharge converter to the The load provides the required insufficient power—power supply mode II, the energy storage device supplies power to the load alone—power supply mode III, which is an extreme case of power supply mode II; when the load power P _o =U _o I _o is less than the maximum value of multiple input sources When the sum of power is P _1max +P _2max +...+P _nmax , the residual energy output by multiple input sources charges the energy storage device through the single-stage isolated bidirectional charge-discharge converter - power supply mode I. Taking a resistive load as an example, the power flow control of a single-stage isolated bidirectional charge-discharge converter is discussed, as shown in Figure 17. For the output filter capacitors C _f , C _f ′ and the load Z _L , the output terminals of the multi-winding time-sharing power supply isolated flyback DC chopper single-stage multi-input inverter and the single-stage isolated bidirectional charge-discharge converter are connected in parallel Equivalent to the parallel superposition of two current sources. It can be seen from the energy management control strategy shown in Figure 16 that the fundamental component of the output current i _Lf of the multi-winding time-sharing power supply isolated flyback DC chopper type single-stage multi-input inverter is at the same frequency and phase as the output voltage u _o , and the output active power The charge and discharge converter is controlled by the SPWM signal generated by the output voltage u _o and the error amplification signal u _o of the reference voltage u _oref and the high frequency carrier. The output filter inductor current i _Lf ′ and u _o There is a phase difference θ between them, and different phase differences θ mean output active power of different magnitudes and directions. When P _o =P _1max +P _2max +...+P _nmax , θ=90°, the active power output by the charge-discharge converter is zero, and it is in a no-load state; when P _o >P _1max +P _2max +...+P When _nmax , u _o decreases, θ<90°, the charge-discharge converter outputs active power, and the energy storage device discharges the load, that is, the energy storage device provides insufficient power required by the load; when P _o <P _1max +P _2max + When ...+P _nmax , u _o increases, θ > 90°, the charge-discharge converter outputs negative active power, and the load feeds back energy to the energy storage device, that is, the residual power output by multiple input sources charges the energy storage device, when θ When =180°, the energy returned by the load to the energy storage device is the largest. Therefore, the energy management control strategy can control the power flow size and direction of the single-stage isolated bidirectional charge-discharge converter in real time according to the relative size of P _o and P _1max +P _2max +…+P _nmax , and realize the system in three different power supply. Smooth and seamless switching between modes.

Claims (2)

1. A multi-winding time-sharing power supply isolation flyback direct current chopper type single-stage multi-input inverter is characterized in that: the inverter is formed by sequentially cascading n paths of mutually isolated input direct current filters, a combined n-input single-output isolated bidirectional flyback direct current chopper and an output alternating current filter circuit, wherein each path of input end of the combined n-input single-output isolated bidirectional flyback direct current chopper is correspondingly connected with the output end of each path of input direct current filter one by one, n is the number of paths of multiple input sources, and n is a natural number greater than 1; the combined n-input single-output isolation bidirectional flyback direct current chopper comprises two same low-frequency positive half cycles and two same low-frequency low half cycles which are respectively outputEach path of input end of the n-input single-output isolation bidirectional flyback direct current chopper of the frequency negative half-cycle unipolar sine pulse width modulation current wave is correspondingly connected in parallel and the output ends of the n-input single-output isolation bidirectional flyback direct current chopper are connected in series in a reverse mode, and the two output ends of the two n-input single-output isolation bidirectional flyback direct current choppers which are not connected in series in a reverse mode are the output ends of the combined n-input single-output isolation bidirectional flyback direct current chopper; the two isolated bidirectional flyback direct current choppers work in turn for a half low-frequency period in a low-frequency output voltage period, when one direct current chopper works to output unipolar pulse width modulation current waves of a low-frequency positive half period, the other direct current chopper stops working, the polarity selection is conducted by the two-quadrant power switch, the positive half period of the sinusoidal alternating current is obtained after the output filter circuit, when one direct current chopper works to output unipolar pulse width modulation current waves of a low-frequency negative half period, the other direct current chopper stops working, the polarity selection is conducted by the two-quadrant power switch, and the negative half period of the sinusoidal alternating current is obtained after the output filter circuit; each n-input single-output isolation bidirectional flyback direct current chopper is formed by sequentially cascading n paths of mutually isolated bidirectional power flow single-input single-output high-frequency inverter circuits, n-input single-output energy storage type transformers and bidirectional power flow high-frequency rectifiers, wherein the output end of each path of bidirectional power flow single-input single-output high-frequency inverter circuit is correspondingly connected with each path of input end of the n-input single-output energy storage type transformers one by one, and the input end of each path of bidirectional power flow single-input single-output high-frequency inverter circuit is each path of input end of the combined n-input single-output isolation bidirectional flyback direct current chopper; the output alternating current filter circuit is formed by an alternating current filter capacitor or formed by sequentially cascading an alternating current filter capacitor and an alternating current filter inductor; each n-input single-output isolation bidirectional flyback direct current chopper circuit is in a single-tube type, double-tube type, parallel-interleaved single-tube type and parallel-interleaved double-tube type topology, each single-tube type high-frequency inverter circuit is composed of a four-quadrant high-frequency power switch bearing bidirectional voltage stress and bidirectional current stress, two drain electrodes of the single-tube type high-frequency inverter circuit are respectively connected with a non-negative end of a primary winding of the energy storage type transformer and a negative end of an input direct current source of the energy storage type transformer, and the negative end of the primary winding of the energy storage type transformer is connected with an output positive end of an input direct current filter of the energy storage type transformerThe left bridge arm of each double-tube high-frequency inverter circuit is composed of a four-quadrant high-frequency power switch bearing bidirectional voltage stress and bidirectional current stress and a high-frequency power diode, the right bridge arm is composed of a two-quadrant high-frequency power switch bearing unidirectional voltage stress and bidirectional current stress and a high-frequency power diode, a drain electrode of the left upper bridge arm switch and a cathode of the right upper bridge arm diode are both connected with an output positive-polarity end of the input direct-current filter of the circuit, the other drain electrode of the left upper bridge arm switch and a cathode of the left lower bridge arm diode are both connected with a negative-polarity end of the input direct-current source of the circuit, an anode of the left lower bridge arm diode and a source electrode of the right lower bridge arm switch are both connected with a non-negative-polarity end of the original winding of the circuit of the energy-storage transformer, the bidirectional power flow high-frequency rectifier of the single-tube circuit and the double-tube circuit consists of a two-quadrant high-frequency rectifier switch bearing unidirectional voltage stress and bidirectional current stress and a two-quadrant polarity selection switch bearing unidirectional voltage stress and bidirectional current stress, the drains of the rectifier switch and the polarity selection switch are connected to be used as the non-serial output ends of the two isolated bidirectional flyback DC choppers, the source of the rectifier switch is connected with the non-inverse end of the secondary winding of the energy storage transformer, the source of the polarity selection switch is connected with the inverse-inverse end of the secondary winding of the energy storage transformer to be used as the inverse-serial output ends of the two isolated bidirectional flyback DC choppers, the parallel staggered single-tube circuit consists of two identical single-tube circuits with parallel primary sides and parallel secondary sides and sharing one polarity selection switch, the parallel staggered double-tube circuit consists of two identical double-tube circuits with parallel primary sides, The secondary sides are connected in parallel and share one polarity selection switch, and the four-quadrant high-frequency power switch is formed by connecting two quadrant high-frequency power switches with two source electrodes connected together in a reverse series manner; n high-frequency inverter circuits in each multi-input single-output isolation bidirectional flyback direct-current chopper respectively input n direct-current voltage sources U_i1、U_i2、…、U_inThe modulated level amplitude is distributed according to the sine envelope curve and the rising slope is U_i1/L₁₁、U_i2/L₂₁、…、U_in/L_n1The single-polarity three-state multi-slope SPWM current wave is rectified into level amplitude distributed according to a sinusoidal envelope curve and with a falling slope of-u by an energy storage type transformer isolation converter and a high-frequency rectifier_o/L₂The single-polarity three-state single-slope SPWM current wave obtains sinusoidal alternating voltage or grid-connected sinusoidal current L on the single-phase alternating current load after passing through the output filter circuit₁₁、L₂₁、…、L_n1Inductances, L, of n primary windings of the energy-storing transformer respectively₂Inductance u for secondary winding of energy-storage transformer_oTo output a sinusoidal voltage transient; the working principle of the inverter is equivalent to the superposition of magnetic fluxes generated by a plurality of input sources in the energy storage type transformer or current increment generated by a primary side inductor of the energy storage type transformer, namely output voltage u_oThe turn ratio N of the multi-input direct-current voltage source and the energy storage type transformer₂/N₁₁、N₂/N₂₁、…、N₂/N_n1Duty ratio d of multi-channel input source₁、d₂、…、d_nThe relationship between is u_o＝(d₁U_i1N₂/N₁₁+d₂U_i2N₂/N₂₁+…+d_nU_inN₂/N_n1)/(1-d₁-d₂-…-d_n) (ii) a The voltage stress of the n-path high-frequency inverter switches of the single-tube type circuit and the parallel staggered single-tube type circuit is respectively

The voltage stress of the n-path high-frequency inverter switch and the n-path high-frequency inverter diode of the double-tube type and parallel staggered double-tube type circuit are respectively U_i1、U_i2、…、U_inThe voltage stress of the two-quadrant high-frequency rectifier switch and the two-quadrant polarity selection switch of the single-tube type, double-tube type, parallel staggered single-tube type and parallel staggered double-tube type circuits are respectively

U_N2max＝max(U_i1N₂/N₁₁、U_i2N₂/N₂₁、…、U_inN₂/N_n1)，U_oOutputting a sine voltage effective value; an independent power supply system formed by the inverter adopts a master-slave power distribution energy management control strategy of output voltage and input current instantaneous values SPWM of insufficient power required by the 1 st, 2 nd, … th and n-1 st input source output power fixing and the nth input source supplementary load, and a grid-connected power generation system formed by the inverter adopts a management control strategy of SPWM maximum power output energy output by feeding back the input current instantaneous values of the 1 st, 2 nd, … th and n th input sources; the n turn ratios of the double-tube type and parallel staggered double-tube type circuit energy storage transformer must meet the requirements

The inverter determines the number of input sources needing to be put into operation by controlling the on-off of n paths of bidirectional power flow single-input single-output high-frequency inverter circuits in each n-input single-output isolation bidirectional flyback direct-current chopper according to the positive half cycle and the negative half cycle of the output voltage and the size of an alternating-current load, wherein the n paths of input sources are U-shaped in one high-frequency switching period_i1、U_i2、…、U_inThe power is supplied to the AC load in parallel in sequence and time sharing, so that n input DC voltages which are mutually isolated and unstable are efficiently inverted into sinusoidal AC power required by the AC load in a single-stage isolation manner.

2. The multi-winding time-sharing power supply isolation flyback dc-chopper type single-stage multi-input inverter of claim 1, wherein: the output end of the multi-winding time-sharing power supply isolation flyback direct current chopper type single-stage multi-input inverter is connected with a single-stage isolation bidirectional charge and discharge converter of the energy storage device in parallel, so that an independent power supply system which can fully utilize the energy of the n input sources 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, and the single-stage isolation bidirectional charge-discharge converter is respectively equivalent to a single-stage voltage type high-frequency link DC-AC converter and a single-stage current type high-frequency link AC-DC converter when the energy storage equipment is discharged and charged; the independent power supply system adopts a management control strategy of the maximum power output energy 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 the 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 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 in which the energy storage device provides required insufficient power to the load through the single-stage isolation bidirectional charge-discharge converter, a power supply mode III in which the energy storage device supplies power to the load independently belongs to the extreme situation of the power supply mode II, and when the 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 in which the residual energy output by the n input sources charges the energy storage device through the single-stage isolation bidirectional charge-discharge converter; for the output alternating current filter capacitor and the alternating current load, the parallel connection of the output ends of the multi-winding time-sharing power supply isolation flyback direct current chopper type single-stage multi-input inverter and the single-stage isolation bidirectional charge-discharge converter is 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 the active power, namely the 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 the negative active power, namely the residual power output by the.

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