Distributed Generation and Its Impact on Power Quality in Low-Voltage Distribution Networks

Abstract

This chapter is dedicated to review and investigate present approaches to power quality assessment in low-voltage (LV) networks with distributed generation (DG). Two comple‐ mentary approaches are considered: firstly, origin of the emission limits requirement for the DG is searched in general electromagnetic compatibility (EMC) conditions used for the equipment and adopted to DG; secondly, rules and regulation of integration with a power system network is used in order to estimate the possible influence of DG on power quality in point of common coupling (PCC). An example of the regulation is control of reactive power consumption in function of active power generation known as cosφ (P) characteristic. This chapter constitutes the attitude that complementary approach brings improvement to the decision about the possible impact of DG in a power sys‐ tem network. It was shown that a combined approach allows to define a proposition of the limits of particular power quality parameters associated with the investigated node of LV network characterized by apparent short circuit power in the PCC (SkPCC). This combi‐ nation brings desirable effect of criterion, making for integration of DG with LV net‐ works. Mentioned attitude was investigated using a real case study of a photovoltaic (PV) system consisting of three independent one-phase subsystems. Estimated influence of the investigated PV on power quality parameters in the PCC was verified using real meas‐ urement. The measurement procedure allows to verify the real influence of the investi‐ gate DG on power quality in the PCC, however, the task in not easy due to problems of separation of the searched influence from the measurement background. One of the pro‐ posed approach is to affiliate changes of investigated power quality parameters with ac‐ tivities of the investigated DG, e.g., energy production. As it was presented in the case of influence of the investigated PV static voltage changes or total harmonic distortion in cur‐ rent in the PCC, a correlation index can be also implemented in order to classify the force of the common influence.