An Active Compensation Strategy for the Low-Voltage Network in Case of Harmonic Current-Producing Loads

In this paper, a strategy for compensating reactive and harmonic currents produced by non-linear loads, when being connected to the low-voltage side of the power system, is investigated. The loads in the low-voltage network can be classified, from the harmonics point of view, into a harmonic current producing type, a harmonic voltage producing type and a harmonic sensitive type. In spite of its associated problems, the compensation in the low-voltage network seems more reliable, economical, effective and straightforward. In general, these problems arise due to the interaction between the load and the power network parameters. The idea here stems from the fact that when applying a pollution treatment for a river, it is not the optimum solution (for all cases) to establish a treatment station across the river. The reliable alternative is to purify those outlets discharging into the river in an individual manner. The proposed strategy will be presented and demonstrated through analysis, design and practical simulation. The flexibility of the technique makes it suitable even to be applied to a small scale loads e.g. a production-line in a factory. It is amazing to deal with the instantaneous reactive power (q) as a time-signal to extract the reference reactive current, without introducing low-pass or high-pass filters into the forward control path. On the other hand, the characterization of loads according to the classification mentioned above is strongly recommended. It will be seen that this task can be done using a shunt active power filter