Affection And Counter-measurements Of Harmonics On Power Energy Metering

With the development of power electronic technology, many kinds of nonlinearity loads appeared numerously. The voltages and currents of power systems distorted for their nonlinearity, impact, and imbalance. Generally, the manufactured watthour meters can only maintain the accuracy in a narrow ranges when the voltages and currents are purely sine, balance in the three phase and their frequency are near the nominal frequency. The accuracy will be affected when the voltages and currents are polluted. With the development of electrical market, the accuracy of energy metering is increasing. However, a search of current research showed that there was no work done on some aspects of metering error of IWHMs that should be considered as follow:There was no method of considering both harmonic power and harmonic current affection in IWHMs.When calculating the error due to harmonic power, the parameters were very difficult to obtain and varied with the amplitudes and phases of currents.Estimating the registration error through the data from common power quality devices that were utilized extensively in power systems was difficult.The fact that the reported watthour was the sum of the fundamental energy and some proportion of the harmonic energy was prone to be misunderstood.Moreover, the influence of harmonics to PT and CT was not considered. The main counter-measurement was to meter each order harmonic energy respectively. But the harmonic energies were ordinally few, even the harmonic pollutions were serious. So the counter-measurement could not encourage compensating harmonics. The follow aspects are studied in this paper:(1)A theory and experiment based analysis is applied. The results show that the defference between the summation of registrations of an induction watthour meter with one order harmonic energy and its registration with all the harmonic energies may reach 4.71%. The least squares method(LMS) is firstly applied to analyzed the experiment data, the error contributions are due to amplitudes and phase angels. To a harmonic order reported powers, their errors contribution from amplitude and phase angle remain constant when the amplitude and phase of currents varied. The affection of reported fundamental power(energy) of IWHMs from harmonics is firstly analyzed and ideal results are obtained. Moreover, SVM method is applied successfully to analyze the test data.(2)This paper analyzes the phase-shift errors of common used varhour meters through sequence component analysis. The frequency response tests and harmonic reactive power tests are done to induction varhour meter and solid-state meter. The test data are analyzed by least square method. The analysis show that the error contribution of varhour meter's registration in the presence of harmonics are due to amplitude effects and phase effects through analysis of theory and experiments: the phase contribution will be large to both induction varhour meter and solid-state meter and may cause metering errors of double harmonic apparent power, the amplitude is decreased with increasing harmonic order and that of the induction varhour is decreased more dramatically.(3)The affection of PT and CT is firstly analyzed, results show that they may cause considerably energy metering error in the presence of harmonics.(4)The counter-measurements are proposed and a typical design of watthour meter is presented.Some contributions of research from two aspects of experiment analysis and simulation analysis on influence and counter-measurements of harmonics to energy metering have been implemented in this paper. The research is helpful to the fair of energy metering and will be applied widely.