Abstract
The progressive electrification of railways involves an increasing number of power electronic converters connected to the railway catenary, which may compromise its stability. Both the converter for traction and the converter for auxiliary power systems (APS) behave as constant power loads (CPL) and interact negatively with the catenary impedance producing voltage instability. This article applies quantitative feedback theory (QFT) to design an ac voltage controller for the APS converter that shapes the dc input admittance of the converter by performing only ac side-control without a dc-side feedback loop. The QFT enables to design a low order controller that satisfies multiple performance specifications in systems with high uncertainty as is the case of the train system. The proposed control guarantees catenary stability while ensuring ac output voltage reference tracking and providing robustness to unmodeled uncertainties. As an additional contribution, the article presents an algorithm for including input admittance specifications in the QFT design process. The proposed control has been evaluated on an experimental platform that recreates the train system. Experimental results show that the controlled system meets railway standards and correctly shapes the specified dc input impedance.
Highlights
R AIL is one of the most sustainable modes of transport thanks to its growing electrification and the increasingly use of renewable energy sources [1]
The train is equipped with converters for traction and converters to supply auxiliary systems. These converters are connected to an ac or dc catenary at a point of common connection (PCC)
This article proposes a voltage control for the auxiliary converter based on the use of the Quantitative Feedback Theory (QFT) [33] to shape the dc input admittance/impedance of the converter
Summary
R AIL is one of the most sustainable modes of transport thanks to its growing electrification and the increasingly use of renewable energy sources [1]. This article proposes a voltage control for the auxiliary converter based on the use of the Quantitative Feedback Theory (QFT) [33] to shape the dc input admittance/impedance of the converter. The main contribution of the proposed control is to shape the dc input admittance of the auxiliary converter to guarantee catenary stability, while ensuring perfect reference tracking of the ac output voltage and offering robustness to non-modeled uncertainties. A thorough search of the relevant literature yielded no related literature on shaping the dc input impedance by performing only ac-side control with no dcside feedback loop Another contribution of the article is to propose an algorithm to include input admittance specifications in the QFT design process.
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