Kenji Yukihira

Harmonic state estimation in distribution network based on fifth harmonic current characteristic

Reproductive simulation of the measurement data by the harmonic analyze is start point to understand harmonic voltage distortion mechanism, but the method to estimate the harmonics distribution among the many utility customers has not been established. In the last decade, harmonic analysis of Japanese middle voltage customer and low voltage customer has been done, the distribution of the fifth harmonic current can be classified middle voltage customers single phase load, low voltage customers three phase and single phase load named group A and middle voltage three phase load named group B, and the amplitude per load kW has been investigated from sum of each current vector. By the application of this knowledge, there is a possibility to estimate the harmonic distribution with many harmonic source in the distribution network. In this paper, we developed a harmonic state estimation method with limited measurement condition by using the fifth harmonic current phase angle classification model. Numerical experiments are conducted in seven node distribution network to test the proposed method. The results show that the proposed harmonic state estimation by using the fifth harmonic current phase angle classification model approach can reliably identify harmonic distribution in the change of load conditions, background harmonic voltage phase angle and series inductance of shunt capacitors.

Reduction of SVC capacity by flicker control using parallel band-pass filters

Flicker is generally caused by electric arc furnaces. The measure equipment such as SVC etc. is generally used to suppress flicker below the restriction value in power system. If flicker control performance can be improved by new control scheme, flicker is suppressed. However, the capacity increases by compensating for all the frequency components. This paper shows proposed control scheme of a line-commutated SVC for flicker control with SVC capacity reduction. The excellent control performance is achieved by applying the control of a feed-forward (FF) and a feedback (FB) schemes at the same time. In addition, proposed control has efficient extraction method of flicker component by design of parallel band-pass filters for capacity reduction. The design gives priority to specific frequency region with high restrain effect in flicker components. The evaluation of control performance and reduction effect of SVC capacity is verified by numerical simulation.

Utility customer model for fifth harmonic state estimation in combination with fundamental state estimation in distribution network

In the last decade, harmonic analysis of Japanese middle voltage (MV) customer and low voltage (LV) customer has been done, the distribution of the fifth harmonic current can be classified MV customers single phase load, LV customers three phase and single phase load named group A and MV three phase load named group B, and the amplitude per load kW has been investigated from sum of each current vector. By the application of this knowledge, there is a possibility to estimate the harmonic distribution with many harmonic source in the distribution network. In this paper, we demonstrate a harmonic state estimation (HSE) in combination with fundamental state estimation (FSE) method with limited measurement condition by using the fifth harmonic current model of utility customer. Numerical experiments are conducted in seven node distribution network with transient simulation to test the proposed method. The results show that the proposed HSE in combination with FSE by using utility customer model approach can reliably identify harmonic distribution with distributed load conditions, background harmonic voltage and shunt capacitors.