Abstract: In order to suppress the voltage source converter-high voltage direct current (VSC-HVDC) low frequency oscillation and improve its transmission capacity, this paper proposes a control strategy for pole assignment. We use the improved TLS-ESPRIT recognition algorithm to identify the open-loop transfer function of the system. According to the root locus diagram of the open-loop transfer function, we get the open-loop gain interval which makes it stable, and then get the closed-loop root locus poles under a better gain which are desired poles. And then we combine the desired poles with the configured observer poles to obtain a pole assignment controller. The application of the observer controller can not only reduce the work load but also have better robustness. To show the superior effect of the proposed controller, we adopted the classical root locus advance compensation method to design the controller and compared it with the proposed controller. The simulation results in PSCAD/EMTDC show that the effect of the controller designed by the classical root locus method is not obvious, while the proposed pole assignment controller can better restrain low frequency oscillation of VSC-HVDC under the different malfunctions, and therefore has better robustness.

Key words: VSC-HVDC, pole assignment, root locus diagram, low frequency oscillation, robustness