Decentralized VSC-Based Microgrid's General Power Flow

In VSC-based microgrids which employ the frequency/voltage droop control method, the power sharing controllers alter the frequency and magnitude of each VSC output voltage based on the output active and reactive power, respectively. This method employs the variable voltage and frequency instead of physical communication link in order to active and reactive power sharing. Since there is no communication link, and the voltage and frequency are not constant in different load conditions, and no DG is large enough to provide all the demand variations, the PV bus model and slack bus model cannot be employed in these networks. Hence the conventional power flow method is not appropriate to calculate the steady state solution in such microgrids. As a result, previous works in this area in order to obtain the steady state solution perform a time domain simulation, which is very time-consuming process for this purpose. Therefore, developing new methods that calculate the steady state solution in a suitable time is a necessity. This paper presents a new approach to construct power flow equations in these networks without PV and slack bus model. The steady state solution of these equations is calculated, and the operating point is obtained much easier and faster than time domain simulation algorithm. In order to validate the proposed method, the time response of the proposed equations is compared with the time domain simulation results of PSCAD/EMTDC, which is an electromagnetic transient simulation program. The comparison indicates that the results of the proposed method, is very accurate. Moreover, the calculation time of this method outperforms other time domain simulation based method. Copyright (C) 2011 Praise Worthy Prize S.r.l. - All rights reserved.