Novel IIOS converter with low-loss LC-PBU

Abstract

Disclosed is a novel IIOS converter with a low loss LC-PBU. The novel IIOS converter comprises a plurality of isolated photovoltaic submodules (SM), wherein each photovoltaic submodule comprising a photovoltaic cell panel and a DC / DC converter. A primary side of the converter adopts a full-bridge circuit, a secondary side of the converter adopts a half-bridge circuit, and independent MPPT controlof each photovoltaic sub-module can be realized by controlling a phase shift angle between the full-bridge circuit and the half-bridge circuit. In order to solve the problem of power mismatch, a powerbalancing unit (PBU) is connected between every two adjacent photovoltaic sub-modules, when the output power of the photovoltaic sub-modules is unbalanced, power transmission of the adjacent photovoltaic sub-modules is achieved by controlling the phase shift angle between the adjacent half bridges so as to balance the voltage of the output side of each isolated photovoltaic sub-module. therefore,each sub-module can operate normally; and meanwhile, all switches of the converter can realize soft switching, so that the switching loss is reduced. Due to device multiplexing, the half-bridge circuit participates in MPPT control and power balance control, so that the investment of devices such as a switching tube is reduced, the topological structure is simplified, and the cost is reduced.

Description

technical field [0001] The invention relates to the technical field of photovoltaic multi-port DC converters, in particular to a photovoltaic multi-port DC grid-connected system with uneven power of photovoltaic cells. Background technique [0002] Compared with AC distributed systems, DC distributed systems have less loss and better stability. MVDC access to distributed photovoltaic systems has become one of the hotspots in the field of new energy research. In this system, the insulation voltage of photovoltaic panels generally does not exceed 1kV, while the voltage level of the medium-voltage bus is much higher. Therefore, in addition to the independent MPPT control of each photovoltaic array, the photovoltaic DC-DC converter also needs to achieve a high boost ratio. Cascading multiple isolated sub-modules is a good choice to achieve a high boost ratio. Suitable topology types include IPOS-type and IIOS-type. The IPOS topology requires independent MPPT control with the...

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Problems solved by technology

Therefore, a method similar to sorting voltage equalization in MMC or dual voltage (bus voltage and sub-module voltage) regulation in IPOS system cannot be directly applied to IIOS system

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