| With the rapid development of the society, more and more researchers and industrial companies focus on the power supply reliability and power quality. Power electronic devices and technologies are widely used in power system recent years, such as SVC, SVG, the distributed renewable energy technologies, energy storage technologies, and the development of micro-grid concept and smart grid concept. They can make up for the fossil energy crisis and improve the grid reliability and stability.Solid-state transformer, also known as power electronic transformer has been considered as an important part of the future smart grid. Power electronic devices and technology are employed to achieve the function of power transmission and voltage convert with the following advantages, reduction of the effect to customers from the grid such as the unwanted change of the grid voltage amplitude and frequency, prevention of the reactive power and harmonic current generated by the customers from influencing the grid, interfaces for photovoltaic, wind and other new energy power stations and network, convenience of the power flow distribution control in the grid to improve the reliability and efficiency of the power system.Modular cascaded solid-state transformer is consisted of several low-voltage modules with low voltage and current stress of each module.High equivalent switching frequency can be achieved by the combination of low switching frequency modules, leading to a decrease of switching loss and the volume of the LC filter. But there is a lot of difficulties for this topology to achieve voltage and power balance control among different modules. Based on this problem, a single-phase d-q vector control with voltage feed-forward-feed-back control strategy is proposed in this paper to achieve voltage and power balance in each module. A prototype is build up and experimental results confirmed the reliability of the proposed solid state transformer control strategy. |
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