Study On Real-Time Harmonics And Reactive Currents Measure In Power System

Firstly, this paper analyses the harm of harmonics and reactive currents in power system. It also points out the significance of eliminating harmonics and compensating reactive currents. To solve the problem, active power filter (APF) is widely used. The key to APF is an accurate and real-time detecting method.p-q theory and ip-iq theory based on instantaneous reactive power theory are used in APF. They both have advantages and disadvantages. p-q-r theory is newly proposed. Compared with the traditional theory, the p-q-r method can be applied in 3-phase 4-wire systems. The shortcomings of the p-q-r method are analyzed. An improved method is proposed. The simulation with MATLAB shows that it is effective.Secondly, a new fan-in transfer vector is proposed. It is based on fan-in vector expression and expanded to use in an unsymmetrical three-phase system. The fan-in transfer vector transfers a three-phase system into a single-phase system. So it simplifies the detecting method for getting positive sequence active component from a three-phase system. In addition, some new fan-in transfer vectors are introduced to reduce the wide of data window. Simulations are carried out to verify the feasibility and correctness of the method.Finally, a measure instrument is built. MSP430F149 is used as hardware platform because of its rich chip-in resources and high-speed performance. An adaptive algorithm of equal-interval synchronous sampling base on fan-in transfer vector is used as software kernel. Some program segments and test results are shown to prove the algorithm is practical.