Research On Method Of Reactive Power Measurement And Its Application

Recently, the use of many inductive and nonlinear loads in power system bring on more and more serious unbalance of reactive power that result in power quality problem, such as voltage deviation and voltage flicker, which affect the safe operation of electrical network. Static var compensator (SVC) and advanced static var generator (ASVG) are primary reactive power compensator, and the reactive power measurement is the key for reactive power compensator, therefore fast and accurate reactive power measurement is the focus in electric measurement.According to reactive power defined by Budeanu, this dissertation develops the simulative experiment equipment of SVC based on system research on reactive power measurement. The main work and innovation of the dissertation are as follows:1. A new algorithm is proposed using wavelet transform and Hilbert transform to calculate the reactive power. Hilbert transform can shift 90°phase for each frequency and has no error in theory. Current and voltage are decomposed by orthogonal wavelet transform, and reactive power in each frequency band can be calculated in time domain. Simulation result shows the highly precision of the algorithm.2. An algorithm of reactive power measurement using wavelet packet is proposed and simulated. Wavelet packet can decompose a signal into low frequency component and high frequency component, which can be further decomposed. Active power and reactive power can be calculated by the decomposition coefficient of current and voltage. Simulation proves the algorithm is useful.3. The method is proposed using BP Artificial neural network (ANN) to compensate nonlinear relation of the fundamental impedance of TCR with trigger angle. ANN is placed between controller and TCR in SVC control system, and the nonlinear relation is compensated by nonlinear map of ANN. Simulation result shows that the compensation effect is very well.4. An iterative algorithm based on an orthogonal characteristic of trigonometric function is proposed to measure fundamental reactive power. Fundamental parameters are calculated by symmetrical and orthogonal characteristic of trigonometric function, and the iterative algorithm can calculate fundamental reactive power fast. Simulation result shows that the precision of the algorithm is high. This algorithm is proved by the simulative experiment equipment of SVC.5. The dissertation presents a method of filtering out the harmonics based on wavelet transform. The low frequency component is obtained by wavelet decomposition of load current. The low frequency component is reconstructed to get fundamental current. Simulation result of ASVG shows the effect of filtering out the harmonics of load current by wavelet is excellent.6. The main circuit, the hardware and software of TMS320LF2407 DSP of the simulative experiment equipment of SVC are designed. The simulative experiment equipment is tested, and the shortest adjust time is 110ms when reactive power changes.