Harmonic power flow of VSC-HVDC based AC/DC power systems

•We investigate the harmonic distortion problem of VSC-HVDC based AC/DC power systems.•The conventional harmonic power flow (HPF) algorithm is modified to include VSC-HVDC subsystems.•A new and simple harmonic model of VSCs called the real harmonic coupling matrix (RHCM) is established.•Newton's method is adopted to simultaneously solve the AC and DC system harmonics and fundamental power flow.•The effect of VSC harmonics on fundamental power flow is studied, so is the effect of different VSC-HVDC operating conditions on harmonics.

This paper extends the traditional harmonic power flow (HPF) to include voltage source converter (VSC) based HVDC. First, a new harmonic model of VSCs, called the real harmonic coupling matrix (RHCM), is developed. The real-valued model is simple in form and easy to calculate. The nonlinear relationship between harmonics and VSC control variables is analytically represented. Then, the model is used to integrate VSC-HVDC into the rectangular-form HPF. Newton's method is adopted to simultaneously solve the AC and DC system harmonics and fundamental power flow. The algorithm is validated by time-domain simulation and tested on a 10-bus AC/DC power system. The effect of VSC harmonics on fundamental power flow is investigated, so is the effect of different operating conditions on harmonics. The results demonstrate that the proposed HPF makes a very useful tool in the harmonic analysis of VSC-HVDC based AC/DC power systems.