Passivity-based control of an asymmetric nine-level inverter for harmonic current mitigation

In this study is approached the design problem of a control law for an asymmetric nine-level multilevel cascade inverter when it is implemented as active filter for harmonic current mitigation purposes. Two are the main features of the proposed controller, namely, its structure is defined considering at a fundamental level the precise establishment, in terms of mathematical expressions, of the steady-state converter behaviour required to achieve the control objective and its stabilisation properties, that render this desired steady-state behaviour attractive (asymptotically stable), are obtained by exploiting the energy-dissipation (passivity) properties of the circuit. These features lead to a simple controller structure that is easy to tune. The stability, high performance and robustness properties of the presented control scheme are experimentally evaluated.