Modeling and Control of High-Voltage Direct-Current Transmission Systems: From Theory to Practice and Back
For power systems engineers, this work provides a theoretically grounded modeling and control framework for multi-terminal HVDC systems, addressing practical limitations of PI control.
This paper proposes a unified port-Hamiltonian modeling framework for multi-terminal HVDC systems, proves global asymptotic stabilization via decentralized PI control, identifies intrinsic transient performance limitations of PI passivity-based control, and overcomes them with an outer-loop controller, verified via simulations on a three-terminal benchmark.
The problem of modeling and control of multi-terminal high-voltage direct-current transmission systems is addressed in this paper, which contains five main contributions. First, to propose a unified, physically motivated, modeling framework - based on port-Hamiltonian representations - of the various network topologies used in this application. Second, to prove that the system can be globally asymptotically stabilized with a decentralized PI control, that exploits its passivity properties. Close connections between the proposed PI and the popular Akagi's PQ instantaneous power method are also established. Third, to reveal the transient performance limitations of the proposed controller that, interestingly, is shown to be intrinsic to PI passivity-based control. Fourth, motivated by the latter, an outer-loop that overcomes the aforementioned limitations is proposed. The performance limitation of the PI, and its drastic improvement using outer-loop controls, are verified via simulations on a three-terminals benchmark example. A final contribution is a novel formulation of the power flow equations for the centralized references calculation.