  Voltage regulation is critical for power grids. However, it has become a much
more challenging problem as distributed energy resources (DERs) such as
photovoltaic and wind generators are increasingly deployed, causing rapid
voltage fluctuations beyond what can be handled by the traditional voltage
regulation methods. In this paper, motivated by two previously proposed
inverter-based local volt/var control algorithms, we propose a pseudo-gradient
based voltage control algorithm for the distribution network that does not
constrain the allowable control functions and has low implementation
complexity. We characterize the convergence of the proposed voltage control
scheme, and compare it against the two previous algorithms in terms of the
convergence condition as well as the convergence rate.
