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Voltage balancing topology adopting bidirectional buck-boost and series LC and control method

A voltage equalization and voltage technology, applied in control/regulation systems, photovoltaic power generation, electrical components, etc., can solve the problems of increased switching loss, unbalanced output voltage, limited voltage regulation effect, etc., to reduce device loss and reduce device cost. Effect

Active Publication Date: 2020-12-04
WUHAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Because the output is connected in series, when the output power of the photovoltaic array is inconsistent, the voltage on the output capacitor is not equal, and the voltage on the output capacitor of the module with higher output power is higher, which is not conducive to the modular design of the cascaded system; When the voltage is too high, the photovoltaic array will deviate from its maximum power point voltage, making the output power drop
[0003] In order to solve the problem of unbalanced output voltage caused by power mismatch, in the prior art, a two-stage conversion topology based on the IIOS structure is proposed, and the voltage regulation capability of the converter is improved by adding a DC MMC stage. However, due to the limitation of the duty cycle, When the photovoltaic power mismatch is serious, the voltage regulation effect is limited; the voltage regulation capability of the converter can also be improved by using a quasi-Z source network, and the adverse effects of power mismatch can be reduced, but a large number of passive components are added; some technologies have proposed A buck-boost voltage balancer using the switched inductance method, adding a buck-boost voltage balancer between every two photovoltaic sub-modules to deal with unbalanced power between adjacent modules, suitable for modular level connected system, but too many switching devices are used, and N photovoltaic modules are cascaded, and 2N-2 switching tubes are required, which not only increases the cost, but also increases the switching loss

Method used

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  • Voltage balancing topology adopting bidirectional buck-boost and series LC and control method
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  • Voltage balancing topology adopting bidirectional buck-boost and series LC and control method

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Embodiment 1

[0043] This embodiment is voltage equalization within the group, which can be the 1st, 2nd, or 3, 4, 2k-1, 2k photovoltaic sub-modules, where 1≤k≤N / 2; duty cycle control is performed within the group.

[0044] Figure 2 shows the output voltage v of the 2k-1th photovoltaic sub-module, taking the kth group as an example. 2k-1 Greater than the output voltage v of the 2kth photovoltaic sub-module 2k The working principle diagram of voltage equalization within the group in the case of Figure 2a shown, when the switch S in the kth buck-boost unit 1,k When turned on, the current flows from the 2k-1 photovoltaic sub-module output capacitor C 2k-1 The positive electrode flows out and passes through the switch S 1,k and the group inductance L B,k , flows into C 2k-1 The negative pole of the 2k-1st photovoltaic sub-module output capacitor C 2k-1 Inductance L B,k Charge; Figure 2b shown, when the switch S in the kth buck-boost unit 2,k When turned on, the inductor current I LB...

Embodiment 2

[0046] This embodiment is voltage equalization between groups, such as groups 1 and 2, groups 2, 3, groups 3 and 4, group k, and group k+1, where 1≤k≤N / 2-1, and between groups is Phase shift control;

[0047] The principle of voltage balance between groups is analyzed by taking a system with a total of 4 photovoltaic sub-modules in the k and k+1 groups as an example. The sum of the voltages of the modules. image 3 Shown are the driving signal waveforms of the IGBT modules of the buck-boost cells of the kth group and the k+1th group and the voltage and current waveforms of the inter-group inductance. The drive signal of the k-th buck-boost unit is g S1,k and g S2,k , the two signals are complementarily turned on, and there is a dead zone between the signals, the k+1 group buck-boost unit drive signal is g S1,k+1 and g S2,k+1 , the two signals are complementarily turned on, and there is also a dead zone between the signals. T S is the switching period of the IGBT module,...

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Abstract

The invention discloses a voltage balancing topology adopting bidirectional buck-boost and series LC and a control method. The voltage balancing topology comprises N isolated photovoltaic sub-modules,a voltage balancing module, a grid-connected inductor and a medium-voltage direct-current bus, the voltage equalization module is composed of N switching tubes, N / 2 intra-group inductors, N / 2-1 inter-group inductors and N / 2-1 inter-group capacitors, and each isolated photovoltaic sub-module is composed of a photovoltaic cell panel, a DC / DC converter and an output equivalent capacitor. Aiming at aphotovoltaic direct-current boosting collection system adopting an input independent and output series (IIOS) structure, the output voltage of each module is balanced when the power of a photovoltaicarray is mismatched, and MPPT (maximum power point tracking) is ensured not to fail. Meanwhile, the voltage balancing module adopts fewer switching tube devices, so that the cost is reduced, ZVS of all switching tubes is realized, and the efficiency of photovoltaic direct-current boost collection and conversion under the working condition of unbalanced photovoltaic input power is improved.

Description

technical field [0001] The invention relates to the technical field of distributed photovoltaics connected to a power grid, in particular to a voltage equalization topology and a control method using bidirectional buck-boost and series LC. Background technique [0002] The integration of distributed photovoltaics into the medium-voltage direct current (MVDC) grid has become one of the research hotspots in the field of new energy. The use of input independent output series (IIOS) cascaded DC / DC converters can achieve high voltage gain while ensuring high conversion efficiency. Because the outputs are connected in series, when the output power of the photovoltaic array is inconsistent, the voltages on the output capacitors are also not equal. The higher the output power, the higher the voltage on the output capacitors of the module, which is not conducive to the modular design of the cascade system; When the voltage is too high, the PV array will deviate from its maximum powe...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M3/158H02J3/38
CPCH02J3/381H02M3/1582H02J2300/22H02M1/0058H02M1/007Y02B70/10Y02E10/56
Inventor 刘飞庄一展刘舟扬黄艳辉查晓明
Owner WUHAN UNIV