Ling Zhibin

Power factor correction of a 400 kW winding rotor induction motor

A way of power factor correction of high power winding rotor induction motor is proposed. By using a voltage source with series connection to the rotor of induction motor, the unity power factor can be obtained. A single phase to three phases cycloconverter to realize this voltage source is designed. PSPICE simulation is performed to confirm the correction operation of control strategy. A prototype of a 400 kW induction motor was developed, the results confirm the validity of the analysis. The power factor of induction motor reaches 0.97.

Grounding faults of cascade battery energy storage system

Grounding faults are inevitable when cascade battery energy storage system (CBESS) is in operation, so the detection and protection are very important in the practical application. The possible grounding fault types of the 10kV CBESS and the detection protection method were analyzed. It could be known that single point grounding fault in CBESS could be detected by monitoring CBESS neutral voltage, and there is no overcurrent in circuit. When two points grounding fault or multi-point grounding fault occurred, the faults could be detected by overcurrent protection or short circuit protection of power unit, and the cascaded battery energy storage system should stop operation.

Design of 2MW/10kV cascaded power conversion system

Cascaded power conversion system was used in battery energy storage system. It can be connected to medium-voltage grid directly and expanded to larger capacity easily. Without 50Hz booster transformer, medium voltage cascaded power conversion system can reduce power loss. In 2011, the China Southern Power Grid launched the project of 2MW/10kV battery energy storage system. In this paper, the design requirement of the cascaded power conversion system, main circuit topology and power unit topology were described. Then parameters of key part were designed, and power loss was analyzed. Besides, a prototype was built to verify the feasibility of the design.

Unified algorithm of single-phase active AC-DC converters and its applications

This paper discusses a novel boost single-phase active AC-DC converters, named low-end semi-controlled bridge AC-DC converter. By analysis, its topology and principle can be derived from the conventional single-phase power factor corrector (PFC). But it has also some differences, such as power device positions, inductor type, input voltage waveform detection and induction current detection, so its design is also different. The converter is implemented by employing two current detection approaches, i.e., current transformer detection and shunt resistor detection. Consequently, it can provide a steady DC output voltage with a low voltage ripple, approximately unitary input power factor and 2.5 kW output power. The experimental results show validity of the theoretical analysis.