Transmission system overvoltage mitigation through the use of distributed generation (DG) smart inverters

Abstract

The objective of this project is to demonstrate the technical ability and cost-effectiveness of reducing electric transmission system overvoltage violations using distributed generation (DG) smart inverters connected to the electric distribution system. Overvoltage violations are situations when the system exhibits voltage levels outside of the acceptable range set by the American National Standards Institute (ANSI) of 105% of nominal system voltage. The challenge that Atlantic Electric could potentially face from the rapid deployment of DG across its distribution system - driven by new additional renewable energy incentive programs in the US State in which it operates - is the underloading of its high voltage (69kV and 115kV) transmission lines causing overvoltage violations at the ends of the transmission lines. The traditional response to this challenge is to install system upgrades on the transmission system in the form of shunt reactors.

However, these system upgrades are expensive and time-consuming to install, which could de-incentivize and delay the deployment of DG projects. The solution we propose is to utilize the reactive power absorption capability of the DG inverters to absorb excessive reactive power from the transmission system. In this work, we investigate feeders' maximum capability of reactive power absorption through distributed generation (DG) smart inverters by modeling two "representative" Atlantic Electric distribution feeders under different PV deployment scenarios based on the feeders' load and generation levels, among other factors. We then perform a cost-benefit analysis to compare against installing shunt reactors. Our findings show that implementing an inverter-based solution has a range of significant cost-savings of up to $300,000/year when compared with installing shunt reactors on the transmission system.

This arrangement, however, is one that hinges on the utility's ability to review regulatory and commercial with all stakeholders involved.