Development of Steady-State Voltage Control Techniques Applied to Microgrids

This paper presents two new steady-state voltage control methodologies for microgrids. The main idea is to use the power factor angle of photovoltaic (PV) inverters to develop two control schemes, a primary one for local voltage control at the interconnection point and a secondary one for voltage control through the coordinated adjustment of several PV generation units. Mathematically, the proposal is based on a set of non-linear equations that represent the equations of the grid, the PV system model, and the proposed control schemes. These equations form a generalized and expanded power flow problem, which can be solved efficiently by the traditional Newton-Raphson method. Complementarity conditions and sigmoid functions are used to treat the inverter limits, carried out automatically and simultaneously with the problem's solution. Computational simulations carried out on a small-scale tutorial system and the IEEE 38-bus system demonstrate the effectiveness of the methodologies. In addition, the performance of the secondary control scheme was evaluated under different load, irradiance, and temperature conditions, considering a time horizon of 7 days (168 hours). The results indicate that the developed control has great potential to improve the voltage profile of microgrids.