Search

For high-power grid-connected voltage source converters (VSC), weight reduction of the LCL filter is one of the main concerns, where a LCL filter can weigh hundreds of kilograms. It is a multidomain optimization issue to find the minimum weight of a LCL filter considering pulse-width modulation (PWM) method, control bandwidth, filter design, and magnetic components with given constraints, such as harmonic standards, semiconductor power losses, and cooling conditions. The comprehensive design procedure and analytical limits of a LCL filter for a 690-V/1.2-MW VSC is provided. In addition, a prototype system of 400 V/40 kW has been built to verify the design methodology and to investigate the impact of different PWM methods on the LCL filter. [ABSTRACT FROM AUTHOR]

Industrial applications of medium-voltage drives impose increasingly stringent performance requirements, particularly with regard to harmonic distortions of the phase currents of the controlled electrical machine. An established method to achieve very low current distortions during steady-state operation is to employ offline calculated optimized pulse patterns (OPP). Achieving high dynamic performance, however, proves to be very difficult in a system operated by OPPs. In this paper, we propose a method that combines the optimal steady-state performance of OPPs with the very fast dynamics of trajectory tracking control. A constrained optimal control problem with a receding horizon policy, i.e., model predictive control (MPC), is formulated and solved. Results show that the combination of MPC with OPPs satisfies both the strict steady-state as well as the dynamic performance requirements imposed by the most demanding industrial applications. The estimation of the fundamental components of the machine variables separately from their respective harmonic components is not required. As a result, complicated structures such as observers can be avoided, contrary to state-of-the-art methods. A further advantage of the MPC method is the use of a receding horizon policy, which provides feedback and a high degree of robustness. [ABSTRACT FROM AUTHOR]