A New Analytical Model of VSC for Harmonic Power Flow

With the fast development of new energy grid, VSC (Voltage Source Converter) has a significant impact on harmonic power flow. In this paper, a new harmonic model based on PWM (Pulse Width Modulation) for VSC is proposed by Fourier algorithm. A general harmonic expression of VSC is derived, which can obtain each harmonic component's amplitude and phase of AC voltage by using only three parameters. Those are the DC voltage, the carrier frequency, and the modulation ratio. Meanwhile, the simulation on PSCAD is set up for verification. It proves that results are consistent with acceptable error. After the AC harmonic voltage is obtained, VSC is again equivalent to the harmonic current source injected into power system by Norton's theorems. Finally, the harmonic power flow containing VSC is calculated, according to harmonic injection method. As shown in the case, the model of VSC based on PWM makes harmonic flow simpler, faster, and more efficient.