Adaptive power capability control scheme for voltage source converter to improve transient stability

Applications of Power Electronic Devices (PED) are rapidly increasing because of their controllability. A Direct Current (DC) transmission system is used for the interconnection of Renewable Energy Sources (RES), and a DC grid research reached the stage of demonstration. Since power electronic devices are controllable, as opposed to conventional ac power facilities, various studies have been carried out on control schemes. Based on fast response speed, the device can affect the stability of the power system by improving the transient stability according to the control method. However, the operation range of converters is limited based on the normal state of the AC system. Therefore, the entire converter capacity cannot be used, and the same standard is applied even in the transient state. In this paper, a novel control scheme is proposed in order to improve the voltage and frequency stability by using the maximum capacity of the converter. The control scheme calculates an Adaptive Power Capability Index (APCI) based on the range of variation of frequency and voltage in the transient state, then applies this index to the controller. In order to verify the new control scheme, a dynamic model is developed and verified in a Transient Stability Analysis (TSA) program. Following the verification of the model, the model is applied to the actual power system data and the power system stability is analyzed.