Research And Design Of Reactive Power Compensator For The Impact Load

Due to nonlinear nature of the impact loads plus application of the power electronic converters in the control systems, heavy harmonics will be injected into distribution systems together with reducing power factor. The harmonics may cause inevitable vibration and overheating of the operational motors, resulting in low efficiency and short longevity of the machinery. In addition, the impact loads may also cause voltage or frequency fluctuations in the grids, consequently, malfunction of the relay protection equipments may happen and there lowers the reliability of power supply. Reactive power and harmonics compensation present the major methodology to address the above mentioned arduous issues and have sighted a lot of effective on-site installations of these technologies. It renders practical significance to develop reactive power compensator specifically to counteract the impact loads in an accurate and smart way.The characteristics and effects of the impact loads are summarized with recurring to a broad category of literatures. In order to overcome the two principal problems for reactive power compensation, namely accuracy and speediness, several key aspects including detection algorithm, control strategy and prototype realization in the compensator design are studied in details, by which a TSC-based compensator with harmonics suppressing function is selected for practical design and development..Design of the TSC-based compensator oriented for impact loads is implemented based on the above theoretical analysis, and the effect of impact loads on concrete design of the control system falls into the main concerns. In the design of the control system, the instantaneous power theory is utilized to achieve accurate and fast detection of the reactive power, and reactive power control with voltage modifications is adopted as control strategy to avoid the defects of power factor control strategy while accelerating the calculation speed. The capacitors are arranged in groups to extend their life-span, and the employment of thyristors can achieve smooth plugging in or out of the capacitors bank within an exact given time without any surge currents or overvoltages. The proposed design is verified with Matlab-based simulations. Finally, a prototype design of the control system is developed and tested in the laboratory. In the device high speed 32bits fixed-point digital signal processor DSP2812 is employed as the key controller that incorporates fast data acquisition, calculation and generation of the control signals. In the meantime, the pretreatment circuits, the frequency trace module as well as the isolation and drive module are also developed along with the central controller. The program is coded in mixed assembling language and C language as to compromise the readability and the executing speed of the coded program. The composed program is debugged in the CCS environment, which presents an smart way to realize intuitive monitoring of the operational process and graphic display of the obtained data. Laboratory tests of the device's performance are carried out based on a prescheduled test scheme. The test results show that, the designed device can operate effectively within a designated scope of the impact loads, with a reaction time of less than a power cycle, and accurate, fast and reliable tracking and compensation of the reactive impact power is achieved smoothly.