Study of voltage unbalance in low-voltage electrical networks with microgeneration systems

Abstract

The issues of studying the influence of microgeneration facilities based on renewable energy sources on the quality indicators of electric power are not widely covered in national studies. However, due to the task set by the Government of the Russian Federation to increase the number of renewable energy sources used by active consumers, the relevance of the study is to determine the features of the influence of microgeneration facilities connected to low-voltage distribution electric networks on voltage unbalance to determine further development paths for this energy sector. The purpose of the study is to design a model of a low-voltage distribution electric network with microgeneration facilities and conduct a computational experiment to assess the influence of microgeneration facilities based on renewable energy sources on voltage unbalance, to determine the ways to improve the quality parameters of electric power associated with voltage unbalance. The study uses a simulation approach, applying a method of mathematical modeling implemented using software complexes NEPLAN and Load Profile Generator. The authors have identified the peculiarities of the impact of microgeneration units on positive voltage deviations and have conducted sensitivity analysis of nodes in the modeled network section based on voltage change criteria. The voltage unbalance coefficients in the negative sequence for the most sensitive network node at various levels of microgeneration unit penetration and different ways of their connection and control are determined. The study also has identified the characteristics of voltage change at each phase with different methods of controlling and connecting microgeneration units. The deployment of microgeneration objects affects positive deviations in voltage and voltage unbalance. The main factors of this influence are the following: the method of connection and control of the microgeneration object, voltage unbalance before the deployment of microgeneration objects, the relationship between the instantaneous powers of the consumer load and the microgeneration object, the sensitivity of nodes to changes in voltage criteria, depending on the electrical distance of microgeneration objects from the main substation, feeder parameters, and load. It has been established that the most effective solution to the asymmetry problem is to redistribute the power provided by the microgeneration object among the phases of the power grid.