Correction of Time-varying PMU Phase Angle Deviation with Unknown Transmission Line Parameters

Phasor measurement units(PMUs)provide useful data for real-time monitoring of the smart grid.However,there may be time-varying deviation in phase angle differences(PADs)between both ends of the transmission line(TL),which may deteriorate application performance based on PMUs.To address that,this paper proposes two robust methods of correcting time-varying PAD deviation with unknown parameters of TL(ParTL).First,the phenomena of time-varying PAD deviation observed from field PMU data are presented.Two general formulations for PAD estimation are then established.To simplify the formulations,estimation of PADs is converted into the optimal problem with a single ParTL as the variable,yielding a linear estimation of PADs.The latter is used by second-order Taylor series expansion to estimate PADs accurately.To reduce the impact of possible abnormal amplitude data in field data,the IGG(Institute of Geodesy&Geophysics,Chinese Academy of Sciences)weighting function is adopted.Results using both simulated and field data verify the effectiveness and robustness of the proposed methods.

Robust Unit Commitment for Large-scale Wind Generation and Run-off-river Hydropower

Increased penetration of large-scale renewable sources such as wind and solar power creates additional constraints for power system maintenance,reliability and security.The intermittent and fluctuation characteristics of renewable energy require robust operation methodologies.Co-optimized scheduling of multiple energy resources is regarded as an efficient way to accommodate renewable energy.As the second largest source of electricity in the world,hydro power is clean and has the merits of ease of regulation,low cost and high flexibility.In this regard,it can play an important role in mitigating the uncertainty of wind power.This paper proposes a robust wind-hydro-thermal unit commitment(UC)model that provides reliable day-ahead unit commitment decisions.The hydro units are operated in longer time scales than the thermal units,so as to capture reservoir operations.The hydro production capability curve is linearized by using variable separation and the piecewise linear(PWL)function,leading to a mixed integer linear programming(MILP)problem that can be solved using mature software such as CPLEX.Numerical tests on an IEEE 39-bus system demonstrate the effectiveness of the proposed model to increase system flexibility in accommodation of uncertain wind power.