Interphase power flow control and voltage regulation in distribution systems with high photovoltaic generation

As distribution systems accommodate higher photovoltaic (PV) penetration, traditional voltage controls face increasing challenges in regulating voltages to within voltage tolerance limits. The voltage issues in the quasi-static steady-state include short-and long-duration RMS variations, voltage unbalance, and under/over voltage violation. This research focuses on developing controls and improving the existing voltage regulation techniques to address the voltage issues so that systems can operate safely and efficiently in the presence of high PV penetration. A novel voltage smoothing algorithm utilizing energy storages (ESs) for voltage short-and long-duration RMS variations mitigation is proposed. The algorithm determines the optimal active and reactive power dispatch for achieving the highest voltage smoothing effectiveness while considering battery daily time of use and life. As a result, smaller energy storages can be utilized for voltage smoothing while their lifetimes are not degraded. To mitigate the over/under voltage violation at the load connection points, an iterative placement algorithm for determining the effective grid-edge voltage regulating device deployment locations is proposed. The other aspect of research focuses on developing interphase power flow (IPPF) control for achieving desirable power flow in each phase and between phases, thereby improving system operation and flexibility. An interphase power flow (IPPF) model is proposed for capturing the power flow at the two-connected terminals of single-phase elements. Based on the IPPF model, necessary dynamic and static controls were developed for enabling single-phase elements to achieve a desirable IPPF injection. Finally, an optimal IPPF control was proposed for coordinating resources in microgrids to achieve an optimized power flow. Generation from PVs can be directed to supply loads or charge ESs regardless of their phase connections. The optimal dispatches also ensure that system voltages are appropriate with no over/under voltage violation and low level of voltage unbalance.