Design Of Reactive Power Compensation Controller With Harmonic Consideration

Reactive power is an important factor to the voltage stability and power loss, and with the increasing of power capacity and electrical equipments, the reactive power requirement grows day by day, therefore, to maintaining the normal operation and quality of the power grids, it is an important means that installing reactive power compensation devices which can supply reactive power for electrical equipments in proper position of the power grids.Reactive power compensation device using capacitors is the most widely used device at present. However, with increased harmonic pollution, the harmonic problems of reactive power compensation devices using capacitors have become increasingly prominent. Therefore, after the introduction of the development of reactive power compensation technology and the relevant theories, the paper discusses the harmonic problem of reactive power compensation, including the correction methods of measurement error caused by asynchronous sampling which is generated in harmonic detection by using FFT, and the coping approach of harmonic problems. At the same time, the paper analyzes the Oscillation phenomenon in traditional reactive power compensation devices which take power factor as control variable, as well as the characters of switches for the capacitors. After that, a new intelligent power compensation controller is designed based on ARM7 processor.The controller takes a high-performance 32-bit ARM chip LPC2368 as the core, and use a high precision energy metering IC ATT7022C to measure the parameter of the power grids, and achieve the function of harmonic analysis by processing the original sample data supplied by ATT7022C. The switch used in the system is a novel compound switch, which can inhibit the inrush effectively and communicate with the host by using RS485, which has a strong anti-interference ability. In order to facilitate the operation and menagement, the hardware circuit also include data storage circuits and human-computer interface consists of keyboard and LCD module.In software of the controller, we choose the real-time operate systemμC/OS-II as the platform for application programs, and divide the software into "driver layer- OS layer-application layer". The paper introduces the transplantation of theμC/OS-II in LPC2368, tasks division and scheduling, as well as task modules programming. The capacity of each capacitor in every circuit is equal, and the controller casts or cuts capacitors based on reactive power and principle of "first in first out'", meanwhile, the controller may send an alarm and cut capacitors which are working when the voltage and harmonic is beyond the given scope.Finally, it implements debugging of the system to realize accurate measurement of power system parameters by using ATT7022C, meanwhile, it carries out a test to switching capacitors, the result of the test shows that the reactive power compensation controller designed in this paper can work in accordance with the control rules, and realize the functions anticipated.