CN108155824A - The series connection non-isolated inverter of simultaneous selection switching voltage type single-stage multi input - Google Patents

Abstract

The invention relates to a single-stage multi-input non-isolated inverter with series and simultaneous selection switch voltage. The input filter and a common output filter are connected, and each input end of the multi-input single-output high-frequency inverter circuit is connected with the output end of each input filter in one-to-one correspondence. The multi-input single-output high-frequency inverter circuit The output terminal of is connected to the input terminal of the output filter. This inverter has multiple input sources without common ground, simultaneous or time-sharing power supply, non-isolated output and input, shared output filter, simple circuit topology, single-stage power conversion, high power density, high conversion efficiency, and low output voltage ripple. The characteristics of small waves and wide application prospects have laid a key technology for realizing the large-capacity distributed power supply system of multiple new energy joint power supply.

Description

Series simultaneous selection switching voltage type single-stage multi-input non-isolated inverter

technical field

The invention relates to a series-selected switching voltage type single-stage multi-input non-isolated inverter, which 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 a stable and high-quality AC power for AC loads or AC grid connection. Inverters with or without electrical isolation between the output AC load or the AC grid and the input DC power supply are called isolated and non-isolated inverters, respectively. Non-isolated inverters have the characteristics of simple circuit structure, high reliability, large output capacity, and low cost. application value.

New energy sources such as solar energy, wind energy, tidal energy, and geothermal energy (also known as green energy) have the advantages of clean, pollution-free, cheap, reliable, and abundant, so they have broad application prospects. Due to the increasing shortage 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 increasing. more and more people's attention. New energy power generation mainly includes photovoltaic, wind power, fuel cell, hydropower, geothermal and other types, all of which have defects such as unstable power supply, discontinuity, and changes with climate conditions. Therefore, a distributed power supply system that uses multiple new energy sources for joint power supply is required.

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 power generators and other new energy power generation equipment that do not require energy storage through a unidirectional DC converter and connect them in parallel or in series at the output end. Afterwards, it is connected to the DC bus of the public inverter, which aims to ensure that various new energy sources are jointly powered and can work in coordination. The distributed power generation system realizes multiple input sources supplying power to the load at the same time and prioritizing the utilization of energy, which improves the stability and flexibility of the system, but has defects such as two-stage power conversion, low power density, low conversion efficiency, and high cost. Its practicality is largely 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 of the DC converter and the inverter shown in Figures 1 and 2 with a new multi-input inverter with a single-stage circuit structure as shown in Figure 3 The traditional multi-input inverter constitutes a new type of 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 supplying power to the load at the same time or time-sharing within one high-frequency switching cycle, and low cost.

Therefore, it is imminent to actively seek a single-stage multi-input inverter that allows a variety of new energy joint power supply and its new energy distributed power supply system. Utilization will be of great significance.

Contents of the invention

The purpose of the present invention is to provide a multi-input and single-output high-frequency inverter circuit with a combination of multiple new energy sources for power supply, non-common ground for input DC power supplies, and a multi-input and single-output high-frequency inverter circuit. Simultaneous or time-sharing power supply to the load, simple circuit topology, shared output filter, single-stage power conversion, high conversion efficiency, small output voltage ripple, large output capacity, wide application prospects, etc. Multi-input non-isolated inverter.

The technical solution of the present invention lies in: a single-stage multi-input non-isolated inverter with simultaneous selection of switching voltages in series, which is composed of a multi-input single-output high-frequency inverter circuit that combines multiple input filters that do not share ground with a common The output filter connection structure of the multi-input single-output high-frequency inverter circuit is connected one by one to the output end of each input filter, and the output end of the multi-input single-output high-frequency inverter circuit is connected to the above-mentioned The input terminals of the output filter are connected, and the multi-input and single-output high-frequency inverter circuit is composed of output terminals connected in series in the forward direction and simultaneously selecting a power switch circuit, a bidirectional power flow single-input and single-output high-frequency inverter circuit Cascaded in sequence, it is equivalent to a bidirectional power flow single-input single-output high-frequency inverter circuit at any time, and each of the series-connected simultaneous selection power switch circuits is composed of a two-quadrant power switch and a power diode. The source of the power switch is connected to the cathode of the power diode, the drain of the two-quadrant power switch and the anode of the power diode are respectively the positive and negative input terminals of the power switch circuit connected in series and simultaneously, the two-quadrant power The source of the switch and the anode of the power diode are respectively the positive and negative output ends of the power switch circuit connected in series; the output filter is composed of an output filter inductor, or an output filter inductor and an output filter capacitor in sequence Cascaded configuration, or composed of output filter inductors, output filter capacitors, and output filter inductors sequentially cascaded.

The present invention is a multi-input inverter circuit structure formed by cascading the DC converter and the inverter of the traditional multiple new energy joint power supply system, and constructing a new type of single-stage multi-input inverter with simultaneous selection switches in series The circuit structure, the circuit structure and topology family of the single-stage multi-input non-isolated inverter circuit structure and topology family and its energy management control strategy are proposed, that is, the circuit structure is provided by providing a multi-input The single-output high-frequency inverter circuit is formed by connecting multiple input filters with different grounds and a common output filter.

The single-stage multi-input non-isolated inverter of the present invention can invert a plurality of non-commonly grounded and unstable input DC voltages into a stable and high-quality output AC power required by a load, and has multi-input DC power supply does not share ground, multi-input and single-output high-frequency inverter circuits are not isolated, output and input are not isolated, multi-input power supplies power to the load at the same time or time-sharing, circuit topology is simple, shared output filter, single-stage power conversion , high conversion efficiency, small output voltage ripple, large output capacity, and wide application prospects. The overall performance of the single-stage multi-input non-isolated inverter with simultaneous selection of switching voltages in series will be superior to the multi-input inverter formed by cascading two stages of the traditional DC converter and inverter.

Description of drawings

Figure 1, a traditional two-stage new energy distributed power supply system in which the outputs of multiple unidirectional DC converters are connected in parallel.

Figure 2, a traditional two-stage new energy distributed power supply system in which the output terminals of multiple unidirectional DC converters are connected in series.

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

Figure 4, the schematic block diagram of a single-stage multi-input non-isolated inverter with simultaneous selection of switching voltages in series.

Figure 5, the circuit structure diagram of a single-stage multi-input non-isolated inverter with simultaneous selection of switching voltages in series.

Figure 6, the steady-state principle waveform diagram of a single-stage multi-input non-isolated inverter controlled by bipolar SPWM in series and simultaneously selecting switching voltage.

Figure 7, the steady-state principle waveform diagram of a single-stage multi-input non-isolated inverter controlled by unipolar SPWM in series and simultaneously selecting switching voltage.

Figure 8, Circuit topology example 1 of series-selected switching voltage type single-stage multi-input non-isolated inverter——half-bridge circuit schematic diagram Ⅰ.

Figure 9, circuit topology example 2 of a single-stage multi-input non-isolated inverter circuit with simultaneous selection of switching voltages in series——half-bridge circuit schematic diagram II.

Fig. 10, circuit topology example three of series-selected switching voltage type single-stage multi-input non-isolated inverter——half-bridge circuit schematic diagram III.

Fig. 11, circuit topology example 4 of series-selected switching voltage type single-stage multi-input non-isolated inverter——full-bridge circuit schematic diagram Ⅰ.

Fig. 12, circuit topology example 5 of series-selected switching voltage type single-stage multi-input non-isolated inverter five----full bridge circuit schematic diagram Ⅱ.

Fig. 13, circuit topology example six of series-selected switching voltage type single-stage multi-input non-isolated inverter——full-bridge circuit schematic diagram III.

Figure 14, the output voltage and input current instantaneous value feedback bipolar SPWM master-slave power distribution energy management control block diagram of the series and simultaneous selection switch voltage type single-stage multi-input non-isolated inverter.

Figure 15, the waveform diagram of the output voltage and input current instantaneous value feedback bipolar SPWM master-slave power distribution energy management control principle of the single-stage multi-input non-isolated inverter with simultaneous selection of switching voltage in series.

Figure 16, the output voltage and input current instantaneous value feedback unipolar SPWM master-slave power distribution energy management control block diagram of the series and simultaneous selection switch voltage type single-stage multi-input non-isolated inverter.

Figure 17, the waveform diagram of the output voltage and input current instantaneous value feedback unipolar SPWM master-slave power distribution energy management control principle of the single-stage multi-input non-isolated inverter with simultaneous selection of switching voltage in series.

Figure 18, a single-stage multi-input non-isolated independent power supply system with output terminals connected in parallel to a single-stage isolated bidirectional charge-discharge converter in series and simultaneously selecting switching voltages.

Figure 19, the maximum power output energy management control strategy with a single-stage isolated bidirectional charge-discharge converter output voltage independent control loop.

Figure 20, the output voltage u _o and the output filter inductor current i _Lf , i _Lf ′ waveforms of the independent power supply system.

Detailed ways

The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments of the specification.

The series simultaneous selection switch voltage type single-stage multi-input non-isolated inverter is composed of a multi-input single-output high-frequency inverter circuit connecting multiple input filters with different grounds and a common output filter. Each input end of the single-output high-frequency inverter circuit is connected to the output end of each input filter in one-to-one correspondence, and the output end of the multi-input single-output high-frequency inverter circuit is connected to the input end of the output filter , the multi-input single-output high-frequency inverter circuit is composed of a multi-channel series-connected simultaneous selection power switch circuit with output terminals connected in series in the forward direction, and a bidirectional power flow single-input single-output high-frequency inverter circuit is sequentially cascaded, and at any time Equivalent to a bidirectional power flow single-input single-output high-frequency inverter circuit, each of the series-connected simultaneous selection power switch circuits is composed of a two-quadrant power switch and a power diode, and the source of the two-quadrant power switch is connected to the power diode The cathodes are connected, the drain of the two-quadrant power switch and the anode of the power diode are respectively the positive and negative input ends of the power switch circuit connected in series, the source of the two-quadrant power switch and the anode of the power diode The positive and negative polarity output terminals of the power switch circuit are respectively selected in series for the road; the output filter is composed of an output filter inductor, or is composed of an output filter inductor and an output filter capacitor cascaded in sequence, or is composed of an output filter inductor , the output filter capacitor, and the output filter inductor are cascaded in sequence.

The schematic block diagram, circuit structure, and steady-state principle waveforms of bipolar SPWM control and unipolar SPWM control inverters of the single-stage multi-input non-isolated inverter with simultaneous selection of switching voltage in series, as shown in Figures 4, 5, and 6, respectively. , 7 shown. In Figures 4, 5, 6, and 7, U _i1 , U _i2 , ..., U _in are n-channel input DC voltage sources (n is a natural number greater than 1), and Z _L is a single-phase AC load (including passive AC loads and active AC load), u _o and i _o are the single-phase output AC voltage and AC current respectively. The n-input single-output high-frequency inverter circuit is composed of multi-channel series-connected simultaneous selection power switch circuit and bidirectional power flow single-input single-output high-frequency inverter circuit in sequence, in which the output terminals are connected in series in forward direction. The multi-channel series selection power switch circuit is composed of n two-quadrant high-frequency power selection switches S _s1 , S _s2 , ..., S _sn and n selection diodes D _s1 , D that can withstand unidirectional voltage stress and bidirectional current stress. _s2 ,..., D _sn composition (the power selection switches S _s1 , S ₂ ,..., S _sn are turned on at the same time or with a phase difference, and the switching frequency is the same or different, here only the analysis of S _s1 , S _s2 ,..., S _sn using the same Switching frequency and simultaneous open control mode), bidirectional power flow single input single output high frequency inverter circuit is composed of multiple two-quadrant high frequency power switches that can withstand unidirectional voltage stress and bidirectional current stress, MOSFET, IGBT can be used , GTR and other power devices; the output filter in the virtual frame ("A" and "B" terminals are the connection terminals) is composed of output filter inductors, or is composed of output filter inductors and output filter capacitors cascaded in sequence, or is composed of The output filter inductor, output filter capacitor, and output filter inductor are cascaded in sequence. The output inductor and capacitor filters are suitable for passive AC loads, and the output inductor filters or output inductors, capacitors, and inductor filters are suitable for AC grid loads; n The input filter of the line is an LC filter (including filter inductors L _i1 , L _i2 , ..., L _in added with dashed boxes) or a capacitor filter (without filter inductors L _i1 , L _i2 , ..., L _in added with dashed boxes ), when the LC filter is used, the n-way input DC current will be smoother. The n-input single-output high-frequency inverter circuit modulates n-channel input DC voltage sources U _i1 , U _i2 ,..., U _{in into} bipolar two-state or unipolar three-state multi-state whose amplitude varies with the number of input power supplies The level SPWM voltage wave u _AB can obtain high-quality sinusoidal AC voltage u _o on the single-phase AC passive load after passing through the output filter inductor L _f and the output filter capacitor C _f , or through the output filter inductor L _f or the output filter inductor After L _f1 , output filter capacitor C _f , and output filter inductance L _f2 , a high-quality sinusoidal AC current i _o is obtained on the single-phase AC grid, and n input pulse currents of n input single output high frequency inverter circuit pass through the input filter L After _i1 -C _i1 , L _i2 -C _i2 ,..., L _in -C _in or C _i1 , C _i2 ,..., C _in , get smooth in the n-way input DC power supply U _i1 , U _i2 ,..., U _in Input direct currents I _i1 , I _i2 , . . . , I _in . Bipolar two-state multi-level SPWM voltage wave u _AB output +1 state amplitude of the positive half cycle is U _i1 + U _i2 +…+U _in , U _i1 +U _i2 +…+U _in-1 ,…, U The amplitude of _i1 and -1 state is U _i1 +U _i2 +...+U _in , and the output negative half cycle -1 state amplitude is U _i1 +U _i2 +...+U _in , U _i1 +U _i2 +...+U _{in- 1} ,..., U _i1 and +1 state amplitudes are U _i1 +U _i2 +...+U _in ; the +1 state and -1 state amplitudes of unipolar three-state multi-level SPWM voltage wave u _AB are both U _i1 +U _i2 +...+U _in , U _i1 +U _i2 +...+U _in-1 ,..., U _i1 . It needs to be added that the half-bridge circuit only has the bipolar two-state multi-level SPWM voltage wave u _AB shown in Figure 6, but the +1 state amplitude and -1 state amplitude during the positive and negative half cycles of the output voltage Both should be multiplied by 1/2.

The single-stage multi-input non-isolated inverter with simultaneous selection of switching voltages in series is a step-down inverter, and n input sources can supply power to the load either time-sharing or simultaneously. Suppose n-1 input source error amplifier output signals I _1e , I _2e , ..., I _(n-1)e and output voltage error amplifier output signal u _e amplitudes are I _1em , I _2em , I _{(n -1) em} , U _em , the amplitude of the sawtooth carrier signal _uc is U _cm , then the corresponding modulation degree is m ₁ =I _1em /U _cm , m ₂ =I _2em /U _cm ,..., m _n = U _em /U _cm , and there are 0≤m _n , ..., m ₂ , m ₁ ≤1 and m ₁ >m ₂ >... >m _n . The principle of this inverter is equivalent to the superposition of multiple voltage-type single-input inverters at the output voltage, that is, the output voltage u _o and the input DC voltage (U _i1 , U _i2 , ..., U _in ), the modulation degree (m ₁ , m ₂ ,..., m _n ) are u _o ＝m ₁ U _i1 +m ₂ U _i2 +...+m _n U _in (unipolar SPWM control) or u _o ＝(2m ₁ -1 )U _i1 +(m ₂ +m ₁ -1)U _i2 +...+(m _n +m ₁ -1)U _in (bipolar SPWM control). Since there are 0<m ₁ , m ₂ ,..., m _n <1 (unipolar SPWM control) and (2m ₁ -1)+(m ₂ +m ₁ -1)+...+(m _n +m ₁ - 1) <1 (bipolar SPWM control), so u _o <U _i1 +U _i2 +…+U _in , that is, the output voltage u _o is always lower than the sum of the input DC voltage U _i1 +U _i2 +…+U _in ; because the inverter belongs to a single-stage circuit structure, and the n-input single-output high-frequency inverter circuit is provided with a multi-channel series connection in which the output terminal is connected in series in the forward direction and simultaneously selects a power switch circuit, so this type of inverter is called a series connection At the same time, select the switching voltage type (step-down type) single-stage multi-input non-isolated inverter. The n input sources of the inverter supply power to the output AC load at the same time or time-sharing within a high-frequency switching cycle, and the modulation degrees can be the same (m ₁ =m ₂ =...=m _n ) or different (m ₁ ≠ m ₂ ≠...≠m _n ).

The series-selected switching voltage type single-stage multi-input non-isolated inverter described in the present invention shares a multi-input single-output high-frequency inverter circuit and an output filter, and has two stages with the DC converter and the inverter. There is an essential difference in the circuit structure of the traditional multi-input inverter composed of two circuits. Therefore, the inverter of the present invention has novelty and creativity, and has the advantages of simultaneous or time-sharing power supply within one switching cycle of multiple input power sources, simple circuit topology, single-stage power conversion, high conversion efficiency (meaning small energy loss), With the advantages of small output voltage ripple, large output capacity, low cost, and wide application prospects, it is an ideal energy-saving and consumption-reducing single-stage multi-input inverter. of great value.

The embodiments of the circuit topology family of the single-stage multi-input non-isolated inverter circuit with simultaneous selection of switching voltages in series are shown in FIGS. 8 , 9 , 10 , 11 , 12 and 13 . In the circuit shown in Figure 8-13, the multi-channel series-connected simultaneous selection power switch circuit at the output end is composed of n two-quadrant high-frequency power switches and n diodes that can withstand unidirectional voltage stress and bidirectional current stress. The bidirectional power flow single-input single-output high-frequency inverter circuit is composed of multiple two-quadrant high-frequency power switches that can withstand unidirectional voltage stress and bidirectional current stress (the half-bridge circuit shown in Figures 8, 9, and 10 consists of 2 A two-quadrant high-frequency power switch is formed, and the full-bridge circuit shown in Fig. 11, 12, and 13 is composed of four two-quadrant high-frequency power switches). What needs to be added is that the circuit shown in Figure 8-13 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; Figures 8, 9, and 10 The half-bridge circuit is only suitable for the situation where n input power modulation ratios are basically equal; the output filters of the half-bridge circuits I, II, and III shown in Figures 8, 9, and 10 are the output L filter and the output LC filter respectively. 1. Output LCL filter, the output filters of the full bridge circuits I, II and III shown in Figures 11, 12 and 13 are respectively the output L filter, the output LC filter and the output LCL filter. Table 1 shows the power switch voltage stress of the two topological embodiments of the single-stage multi-input non-isolated inverter with the switching voltage selected in series at the same time. The half-bridge circuit is suitable for medium-power high-voltage input inverter occasions, and the full-bridge circuit is suitable for high-power high-voltage input inverter occasions. This circuit topology family is suitable for transforming multiple non-communicating and unstable input DC voltages into a stable and high-quality output AC with the required voltage, and can be used to realize new single-stage multiple new circuits with excellent performance and wide application prospects. Energy distributed power supply system, such as photovoltaic battery 400-500VDC/220V50HzAC or115V400HzAC, large wind power generation 510VDC/220V50HzAC or 115V400HzAC and other multi-input sources supply power to AC loads or AC grids.

Table 1 The power switch voltage stress of the two topological embodiments of the single-stage multi-input non-isolated inverter with simultaneous selection of switching voltage in series

Energy management control strategy is crucial for multiple new energy joint power supply systems. Since there are multiple input sources and corresponding power switch units, it is necessary to control multiple duty cycles, that is, there are multiple control degrees of freedom, which provides the possibility for energy management of various new energy sources. The energy management control strategy of the single-stage multi-input low-frequency link inverter with simultaneous selection of switching voltage in series requires energy management of the input source, MPPT and output voltage (current) control of new energy generation equipment such as photovoltaic cells and wind turbines Three major functions, and sometimes it is necessary 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 single-stage multi-input low-frequency link inverter with simultaneous selection of switching voltages in series adopts two different energy management modes: (1) Energy management mode I--master-slave power distribution mode, the power required by the known load is supplied by the master as much as possible Provided by the 1st, 2nd, ..., n-1 input sources of the equipment, given the input current of the 1st, 2nd, ..., n-1 input sources, it is equivalent to giving the 1st, 2nd, ..., n-1 channels The input power of the input source, the insufficient power required by the load is provided by the nth input source of the power supply equipment, and there is no need to add a battery energy storage device; (2) Energy management mode II—maximum power output mode, the first, second, and second ..., n-channel input sources are output to the load with the maximum power, eliminating the need for battery energy storage equipment, and realizing the full utilization of energy requirements of the grid-connected power generation system. The stability of the output voltage (current) of the power supply system. When the input voltages of n new energy sources are all given, by controlling the input current of the 1st, 2nd, ..., n input sources, it is equivalent to controlling the input power of the 1st, 2nd, ..., n input sources.

Series simultaneous selection of switching voltage type single-stage multi-input non-isolated inverters, adopting output voltage and input current instantaneous value feedback bipolar SPWM, unipolar SPWM master-slave power distribution energy management control strategy to form an independent power supply system; or The input current instantaneous value feedback bipolar SPWM, unipolar SPWM maximum power output energy management control strategy to form a grid-connected power generation system. The output power of the 1st, 2nd, ..., n-1 input sources is fixed and the nth input source supplements the insufficient power required by the load. Output voltage, input current instantaneous value feedback bipolar SPWM, unipolar SPWM master-slave power The distribution energy management control block diagram and the control principle waveform are shown in Figures 14, 15, 16, and 17, respectively. The 1st, 2nd, ..., n-1 input sources are calculated by the maximum power point to obtain the reference current signal I ^* _i1r , I ^* _i2r , ..., I ^* _i(n-1)r , the inverter 1st, 2nd , ..., n-1 input current feedback signals I _i1f , I _i2f , ..., I _i(n-1)f are respectively related to the 1st, 2nd, ..., n-1 reference current signals I _i1r , 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 by the sinusoidal synchronous signal and then passed through the absolute value circuit After 1, 2, ..., n-1, get ︱i _1e ︳, ︳i _2e ︱, ..., ︳i _(n-1)e ︱, the inverter output voltage feedback signal u _of is proportional to the reference sinusoidal voltage u _r The integral regulator is relatively amplified, and the amplified error signal u _e passes through the absolute value circuit n to obtain ︱u _e ︳,︱i _1e ︳, ︳i _2e ︱,...,︳i _(n-1)e ︱, ︱u _e ︳ Respectively intersect with the zigzag carrier u _c and consider the output voltage gating signal to get the control signals u _gss1 , u _gss2 , ..., u _gssn , u _gs1 (u _gs4 ), u _gs2 ( u _gs3 ). When the load power P _o is greater than the sum of the maximum power of the 1st, 2nd, ..., n-1 input sources, the output voltage u _o decreases, and the effective value of the output voltage u _e of the voltage regulator is greater than the threshold comparison level U _t And I _1e , I _2e , ..., I _(n-1)e are all greater than zero, diodes D ₁ , D ₂ , ..., D _n-1 are blocked, and the first, second, ..., n-1 current regulators 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 realize the maximum power output of the 1st, 2, ..., n-1 input sources, and the n-th voltage regulator is used to stabilize the output voltage of the inverter. The n-th input The source supplies power to the load at the same time or time-sharing; when the load power P _o is less than the sum of the maximum power of the 1st, 2nd, ..., n-1 input sources, the output voltage u _o increases, and when the voltage regulator output voltage u _e When the RMS value of V is lower than the threshold comparison level U _t , the diode D _n-1 is turned on, D ₁ , D ₂ ,..., D _n-2 are still blocked, and the hysteresis comparison circuit n+1 outputs a low level. The nth input source stops power supply, the voltage regulator and the current regulator form a double closed-loop control system, the 1st, 2nd, ..., n-1 input sources supply power to the load at the same time or time-sharing within a switching cycle, the current regulator The reference current 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 is reduced (operating at non-maximum point), the output power of the nth 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 ︱u _e ︳ and the error current signal ︱i _1e ︳, ︳i 2e ︳, ︳i _2e ︳, ..., ︳i _{(n-1 ) e} |, thereby changing the modulation degree m ₁ , m ₂ , ..., m _n , so the adjustment and stability of the output voltage and input current (output power) of the inverter can be realized.

When the nth input source in Figure 14-17 is designed as input current feedback to control the input current, the input current instantaneous value feedback bipolar SPWM and unipolar SPWM maximum power output energy management control strategies are formed. The input current feedback signals I _i1f , I _i2f , ..., I _inf of the 1st, 2nd, ..., n channels of the inverter are respectively compared with the reference currents obtained by calculating the maximum power point of the input sources of the 1st, 2nd, ..., n channels The signals I _i1r , I _i2r , ..., I _inr are amplified by proportional integral regulators, and the error amplification signals I _1e , I _2e , ..., I _ne are respectively multiplied by sinusoidal synchronous signals and passed through absolute value circuits 1, 2, ..., n After that, ︱i _1e ︳, ︳i _2e ︱, ..., ︳i _ne ︱, ︱i _1e ︳, ︳i _2e ︱, ..., ︳i _ne ︱ respectively intersect with the saw-tooth carrier u _c and consider the output voltage to select the communication _The control _{signals u gss1 , u gss2} , . The 1st, 2nd, ..., n-channel current regulators work independently, and are all used to realize the maximum power output of their respective input sources, and the n-channel input sources supply power to the load simultaneously within one switching cycle.

The bipolar and unipolar SPWM control principle waveforms shown in Figures 15 and 17 mark a certain high-frequency switching period T _S and the conduction times T _on1 and T _on2 of the first, second, ..., n-way input sources , ..., T _onn and the conduction time T _on of the power switch S ₁ , T _on =T _on1 >T _on2 >...>T _onn , the conduction time T _on changes according to the sinusoidal law within one output voltage cycle. In addition, for the half-bridge circuits Ⅰ, Ⅱ, and Ⅲ shown in Figures 8, 9, and 10, half of the input DC voltage value (U _i1 /2, U _i2 /2, ..., U _in /2) should be substituted into the voltage Calculated in the transmission ratio formula.

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 achieve output voltage stability, that is, connect a A single-stage isolated bidirectional charge-discharge converter is shown in Figure 18. 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 cycloconverter, an output filter (L _f ′, C _f ′ ) are sequentially cascaded, and the cycloconverter is composed of four-quadrant high-frequency power switches capable of withstanding 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 and 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 19. When the load power P _o =U _o I _o is greater than the sum of the maximum power of multiple input sources P _1max +P _2max +...+P _nmax , energy storage devices such as batteries and supercapacitors are charged to 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 belongs to the extreme situation of power supply mode II; when the load power P _o = U _o I _o is less than the maximum of multiple input sources When the power sum is P _1max +P _2max +...+P _nmax , the remaining energy output by multiple input sources will charge the energy storage device through a 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 20. For the output filter capacitors C _f , C _f ′ and the load Z _L , the parallel connection of the output terminals of the single-stage multi-input non-isolated inverter and the single-stage isolated bidirectional charge-discharge converter is equivalent to two Parallel superposition of current sources. From the energy management control strategy shown in Figure 19, it can be seen that the output filter inductor current i _Lf of the single-stage multi-input non-isolated inverter with simultaneous selection of switching voltages in series and the output voltage u _o have the same frequency and phase, and output active power; the charge-discharge converter It is controlled by the intersection of the error amplification signal u _oe of the output voltage u _o and the reference voltage u _oref and the high-frequency carrier to generate a SPWM signal. There is a phase difference θ between the output filter inductor current i _Lf ′ and u _o , and different phases The difference θ means outputting active power with 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 the 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 remaining power output by multiple input sources charges the energy storage device, when θ = 180°, the energy that the load feeds back to the energy storage device is the largest. Therefore, the energy management control strategy can control the magnitude and direction of the power flow 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 , realizing the system in three different power supply Smooth and seamless switching between modes.

Claims (3)

1. A single-stage multi-input non-isolated inverter with simultaneous selection of switching voltages in series, characterized in that: this inverter uses a multi-input single-output high-frequency inverter circuit to filter multiple inputs that are not in common The multi-input single-output high-frequency inverter circuit is connected with a common output filter. Each input end of the multi-input single-output high-frequency inverter circuit is connected with the output end of each input filter in one-to-one correspondence. The output of the multi-input single-output high-frequency inverter circuit end is connected with the input end of the output filter, and the multi-input and single-output high-frequency inverter circuit is composed of multi-channel series connection of the output end in series and simultaneously selects the power switch circuit, bidirectional power flow single-input and single-output high The frequency inverter circuit is cascaded in sequence, which is equivalent to a bidirectional power flow single-input single-output high-frequency inverter circuit at any time, and each of the series-connected simultaneous selection power switch circuits is composed of a two-quadrant power switch and a power diode The source of the two-quadrant power switch is connected to the cathode of the power diode, and the drain of the two-quadrant power switch and the anode of the power diode are respectively the positive and negative input terminals of the power switch circuit connected in series and simultaneously selected. The source of the two-quadrant power switch and the anode of the power diode are respectively the positive and negative output ends of the power switch circuit connected in series; the output filter is composed of an output filter inductor, or an output filter inductor, an output The filter capacitors are sequentially cascaded, or the output filter inductors, the output filter capacitors, and the output filter inductors are sequentially cascaded. 2. The series-connected and simultaneously selected switching voltage type single-stage multi-input non-isolated inverter according to claim 1, characterized in that: the circuit topology of the series-connected simultaneously selected switching voltage type single-stage multi-input non-isolated inverter is Half-bridge and full-bridge circuits. 3. The series-selected switching voltage type single-stage multi-input non-isolated inverter according to claim 1, characterized in that: the output terminals of the series-connected simultaneously selected switching voltage type single-stage multi-input non-isolated inverter are parallel A single-stage isolated bidirectional charge-discharge converter connected to an energy storage device to form an independent power supply system with stable output voltage; the single-stage isolated bidirectional charge-discharge converter consists of an input filter, a high-frequency inverter, a high-frequency A transformer, a cycloconverter, and an output filter are cascaded in sequence, and the cycloconverter is composed of a four-quadrant high-frequency power switch that can withstand bidirectional voltage stress and bidirectional current stress; multiple input sources work at the maximum power output According to the relative magnitude of the load power and the maximum power sum of multiple input sources, the magnitude and direction of the power flow of the single-stage isolated bidirectional charge-discharge converter can be controlled in real time, so as to realize the stability of the system output voltage and the smooth and seamless switching of the charge and discharge of the energy storage device. .