Abstract
Photovoltaic (PV) power plant collection and connection to a high voltage direct current (HVDC) grid has many advantages. Compared with the traditional AC collection and grid-connection scheme, it can reduce the power conversion links and improve the system efficiency. As one of the most important devices in the application of a PV HVDC collection and grid-connection system, a high voltage, large capacity, high step-up ratio DC/DC converter is the critical technology. A DC/DC converter scheme based on a boost full bridge isolated power module cascaded in input parallel output series (IPOS) structure is proposed to meet the technical requirements of PV power conversion with high voltage, large capacity, and high step-up ratio. The operation mode of the power module is analyzed, the soft switching method is proposed, and the constraint to realize the soft switching of the power module is deduced. Aiming to resolve the problem of multi-module voltage and current equalization in a cascaded DC/DC converter, a distributed module equalization control strategy is proposed to realize the reliable operation of a power module and converter. A 5 kV/80 kW standard power module is developed, the DC/DC converter experimental platform is built, and the proposed system scheme and control strategy are verified by experiments. Based on a 14-power module input parallel output series connection, a ±30 kV/1 MW PV DC/DC converter is developed, a ±30 kV PV HVDC collection and grid-connection demonstration system is established, and the experimental test is completed to realize the stable operation of the system.
Highlights
The large-scale development and utilization of photovoltaic (PV), wind power, and other renewable energies are important solutions to solve the energy crisis and environmental problems [1]
When the PV power plant receives the power grid power limiting dispatching command, if the current output power of the converter is less than the power limiting dispatching command value, the DC/DC converter will operate in the maximum power point tracking mode according to the current actual output power
Standard power module is lection and grid-connection DC/DC converter, a 5 kV/80 kW standard power module is developed based on the boost full bridge isolated topology, and the experimental test of developed based on the boost full bridge isolated topology, and the experimental test of module is completed
Summary
The large-scale development and utilization of photovoltaic (PV), wind power, and other renewable energies are important solutions to solve the energy crisis and environmental problems [1]. A modular cascaded DC/DC converter is another effective technical scheme to realize high voltage, large capacity, and high step-up ratio, especially the input parallel output series (IPOS) module cascade structure, which is suitable for high power conversion from low voltage to high voltage It can use the existing low voltage power devices and power conversion topology, and facilitates the improvement of system reliability and capacity expansion and meets the technical requirements for PV HVDC collection and grid-connection application [16]. According to the application requirements of PV HVDC collection and grid-connection DC/DC converter, a boost full bridge isolated standard power module-based input parallel output series cascaded converter is proposed and high voltage, large capacity, and high step-up ratio of the PV power conversion are realized. Experimental results and demonstration system test results verified the proposed DC/DC converter and control strategy
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