Recently, the Zhuhai Power Supply Bureau of Guangdong Power Grid completed the commissioning of a ±10 kV compact economical medium-voltage DC solid-state transformer demonstration project at Erjingwan Wetland Park in the Hengqin Guangdong-Macao Deep Cooperation Zone. The equipment has officially gone into operation under load. This project is a core demonstration achievement of China Southern Power Grid’s key science and technology project, achieving multiple technical breakthroughs in new circuit structures, control algorithms, and silicon carbide semiconductor device applications.
As distributed photovoltaics, energy storage systems, and high-power electric vehicle charging stations increase in cities, power grids are accelerating their transition to hybrid AC-DC operation modes. DC solid-state transformers have become key equipment for building new power systems. Traditional transformers mainly rely on iron cores and coils to achieve voltage step-up and step-down, only capable of simple power transmission without flexible control. Solid-state transformers, also known as power electronic transformers, can be understood as “smart power routers” for the grid. They not only transform voltage and isolate circuits, but also flexibly dispatch electrical energy, support bidirectional power transmission, and can quickly implement protection and disconnection during faults.
However, solid-state transformers still face industry challenges of large size and high costs in the process of moving toward scaled urban application. DC transformers on the market previously required significant floor space and high investment, making large-scale urban deployment difficult. Addressing this pain point, the Zhuhai Power Supply Bureau targeted “small size and high cost-effectiveness,” conquering multiple technical challenges including new circuit structures, control algorithms, and silicon carbide semiconductor device applications, and developed a 1 MW capacity ±10 kV medium-voltage DC solid-state transformer. One end of the equipment connects to the ±10 kV medium-voltage DC grid, while the other end outputs ±375 V DC, with the entire unit achieving a maximum operating efficiency of 98.5%.
In terms of miniaturization and cost reduction, the equipment innovatively adopts a three-level circuit structure. Under the same 1 MW power conditions, the number of modules is halved compared to traditional solutions, with both equipment volume and manufacturing costs decreased by over 30%. This solved the industry problem of DC distribution equipment being both large and expensive. In terms of fault protection, relying on its own circuit design, the equipment can quickly suppress fault current during short-circuit faults without requiring additional expensive DC circuit breakers; even if individual modules fail, it can continue operating without shutdown, with fault handling response speed reaching within 0.1 milliseconds.
In terms of device application, the equipment is equipped with third-generation semiconductors, adopts silicon carbide device parallel technology to achieve current distribution equilibrium between devices, operates with soft switching throughout, has low energy loss, and operates at noise levels below 65 decibels, balancing energy-saving effects with on-site environmental requirements.
Source:Bjx Power Grid