Congestion Management, Total Transfer Capability Improvement and Short-Term Adequacy Evaluation in Deregulated Power Systems – Prospering and Surviving in the Competitive World

Abstract

While two objectives of deregulation are to reduce service interruptions and achieve lower energy costs, deregulation has actually introduced new problems in both areas.

Since the transmission network was built in the last century, mainly for the regulated power systems, with mostly local power transfers, the increased long distance power transfer introduced by free energy trading has made congestion happen more frequently. When congestion happens, service interruptions occur and higher energy costs arise.

We approach the issue from the viewpoints of both planning and online operations. Accordingly, we develop a reactive online remedying method that uses Flexible AC Transmission (FACTS) devices to eliminate congestion with minimum transaction curtailment to maintain market force. We also develop a proactive preventive method for offline planning, such as in the day-ahead market, which uses FACTS devices to maximize the Total Transfer Capability so that more transactions can be scheduled without causing congestion in the system. Optimal Power Flow is used for both methods with FACTS devices treated as control variables so that they can be adjusted to the best FACTS parameters to minimize the transaction curtailment or maximize the Total Transfer Capability. We demonstrate that FACTS devices are very effective for both situations.

Since the installation of FACTS devices involves heavy infrastructure investment, an effective pricing method needs to be in place to encourage this investment by guaranteeing sufficient return. This research uses a novel pricing scheme to charge for both utilizing the FACTS devices and having the FACTS devices operating at their limits. The owners of the FACTS devices will then be able to recover their investment.

With the above control method and the pricing method, we can make better use of the existing transmission network and relieve congestion. However, deregulation may also degrade system reliability since the generation companies are not obligated to sell into the market and market participation is driven by market forces instead.

We use the market share based short-term adequacy analysis method to address generation resource adequacy issues. The market share based method uses the market share time series for the generation companies to reflect their market behavior in the new environment. Multiple regression modeling, a tool of time series analysis, is used to model involved factors. We demonstrate how the market share based short-term adequacy analysis method can capture the adequacy problems that the traditional method cannot. In addition, it can also help to remedy the adequacy problems, which can in turn reduce service interruption and thus the energy price.