Mingye Zhang

Optimal Voltage Control of PJM Smart Transmission Grid: Study, Implementation, and Evaluation

PJM Interconnection operates the largest synchronized transmission system in North America, where one of the great challenges is being able to meet the system-wide voltage control performance requirements both pre- and post-contingency. Based on a characteristic analysis of the contingencies distribution, a practical method using an iteration scheme between the optimal power flow (OPF) and a contingency assessment (CA) is proposed to develop a control strategy, so that the calculated optimal voltage schedule solutions are better not only for pre-contingency system conditions, also for the post-contingency (N-1) system conditions. At step T, a CA considering all contingencies is carried out and those that may lead to the maximized voltage violations are saved as active contingencies for step T+1. At the same time, another CA, considering only the current active contingencies, is computed in parallel using a trial OPF result as input. According to the post-contingency indices, the new voltage constraints will be compressed and the final OPF is called again to calculate the optimal strategies. The detailed architecture of the PJM optimal voltage control (OVC) system is presented in this paper. The system has completed four-months of online operation, and the results have been evaluated using third-party software. It has been proven that the OVC system presented here will greatly improve both the pre- and post-contingency performance. The PJM OVC is a typical application of a smart transmission grid. Phase III of this study is currently under way.

Study of system-wide Automatic Voltage Control on PJM system

The feasibility and potential benefits of the system-wide Automatic Voltage Control (AVC) in PJM system are studied in this paper. A test AVC system with a hierarchical structure is adopted for simulation study, which is based on eight typical real-time snapshots from the solutions of state estimator in the PJMs Energy Management System (EMS). For each snapshot, the control action simulation is executed in a recursive way by power flow (PF) calculation until the result is no longer changed. Simulation results on adaptive zone division, tertiary voltage control and secondary voltage control are presented here, and comparison of transmission losses and reactive power reserve for all the eight cases before and after AVC are carried out. About 1% reduction of transmission system loss, which means saving energy more than 100 million kWh/year and saving money more than

Voltage control practices and tools used for system voltage control of PJM

10 million/year, and about 1% increase of system MVAR reserve can be achieved in PJM system thanks to AVC. The research results are evaluated by existing CA (Contingency Assessment) tool with 4745 contingencies, which prove that the performance indices in security after AVC is improved significantly than that before AVC. The Phase II of PJMs AVC project, online implementation of AVC at PJM control center, is ongoing now.

A sensitivity based simplified model for security constrained optimal power flow

PJM has developed a pilot program of on-line (real time) voltage control in which a system wide Optimal Voltage Control (OVC) demonstration system has been implemented and run on-line parallel with PJM existing system at PJM control center since Jan. 2010. The pilot program was for nine months. The OVC system consists of Data I/O Management, Control Strategy Calculation, Operation Log Management and Control Process Dispatch. It is interfaced with PJM EMS system, automatically receives real-time snapshot from PJM EMS periodically, and calculates optimal voltage schedules for each generator, LTC and switchable shunt in the PJM system. The practices, experiences and results of the pilot program are presented in this panel paper. Significant potential benefits can be achieved with OVC techniques in both aspects of security and economy: (1) average reduction of transmission system loss is about 1.19%, which means energy savings of more than 220 million kWh/year and monetary savings of more than

Safely and economically coordinated automatic voltage control method based on cooperative game theory

17 million/year; (2) Average increase of system VAR reserve is about 1.08%; (3) Improvement on system security for pre-contingency and post-contingency is significant, including improvement on these security indices in voltage limits violations, and voltage stability limits violations.