This paper presents a study to estimate the composition of an electric load, i.e. to determine the amount of each load class by the direct measurements of the total electric current waveform from instrument reading. Kalman filter algorithm is applied to estimate the electric load composition on a consumer side of a distributed power system. The electric load supplied from the different voltage level by using a non-ideal delta-wye transformer is also studied with consideration of the practical environment for a distributed power system.

In this paper, a realization of an imaginary resistor using an ideal transformer is proposed. In the same fashion as the conventional method, a signal path is divided into a real signal path and an imaginary path. We name circuits which constitute a real signal path and an imaginary signal path, a real circuit and an imaginary circuit, respectively. An imaginary resistor is converted into an ideal transformer embedded between the imaginary circuit and the real circuit. The imaginary circuit becomes a dual circuit of the real circuit. This filter consists of terminating resistors, inductors, capacitors and ideal transformers. This prototype circuit is simulated by using operational amplifiers. A 3rd-order complex Chebyshev bandpass filter is designed and its frequency response is measured. Finally, the sensitivity property of the proposed filter is evaluated by a computer simulation.