Impact of Causality on Performance of Phasor Measurement Unit Algorithms

Most of existing phasor measurement units (PMUs) are non-causal PMUs and they compensate for the group delay in PMU applications by shifting time stamps backward, which may result in a high latency that will impair performance of PMU applications. This paper presents causal PMUs to reduce the group delay caused latency without shifting time stamps backward, and studies the impact of causality on performance of PMU algorithms. The paper first analyzes how causal and non-causal PMUs compensate for the group delay caused by digital filters and it is found that causal PMUs normally reduces latency by the group delay while non-causal PMU will not. Then, the impact of causality on performance of PMU algorithms is investigated and analyzed by using the Hydro Quebec Research Institute (IREQ) PMU model and the IEEE PMU model. Finally, the simulation results based on the New England 39-bus test system highlight the difference between the causal method and the non-causal method under fault conditions in realistic multi-machine setups.