Combined Central and Local Active and Reactive Power Control of PV Inverters

The increasing amount of photovoltaic (PV) generation results in a reverse power flow and a violation of the overvoltage limits in distribution networks. PV inverters can curtail active power or consume reactive power to avoid these excessive high voltages. Local controllers of active and reactive power that are based on measurements of the produced PV power have a fast response to the changing production levels of the PV installation. The performance of these local controllers depends on the tuning of the control parameters, which are grid and time dependent. In this paper, local control functions are defined as piecewise linear functions. The parameters of all the local control functions are regularly reoptimized. This results in an optimal use of reactive power and a minimum amount of curtailed active power, while respecting network limitations. The optimization of these parameters is formulated as a convex optimization problem, which can be solved sufficiently fast. The performance of the control is evaluated on an existing three-phase four-wire distribution grid and is compared with different local control methods.