Josef Tlustý

Optimal control of shunt active power filters in multibus industrial power systems for harmonic voltage mitigation

The bus voltage and branch current detection control strategies of the active power filters used in industrial multibus power systems for harmonic voltage mitigation are analyzed and compared in the paper. The effectiveness of both the methods with real control gains is assessed in terms of the harmonic bus voltage mitigation and of the demanded current spectrum injected by the active power filters.

Cooperative Control of Active Power Filters in Power Systems without Mutual Communication

The procedure for calculating controller parameters of the APFs implemented into a multibus industrial power system for harmonic voltage mitigation is presented. The node-voltage-detection control strategy is applied and the basic controller parameters are found under the condition that the demanded THD factors at the buses where the APFs are placed will be obtained. A cooperative control of several APFs without mutual communication is proposed, simulated, and experimentally verified. By tuning the controller gains without considering the power circuit parameters, all APFs used tend to share harmonic load currents approximately equally regardless of the operation modes of the nonlinear loads in different parts of the power system.

Power Control at Grid Connected Converters and Analytical Solution of Steady States

The paper presents a power control technique at grid connected converters under unbalanced voltage conditions. The current positive and negative sequences during grid voltage sags are controlled to ensure a proper exchange of active and reactive powers without power ripples. An analytical solution in a closed form of the B6 and B4 converters working with an optimized half a period switching symmetry is presented. The analytical solution may be applied for the converters connected to highly unbalanced grids and for different grid filter topologies.

Optimized half a period switching symmetry applied at grid connected four-switch converter and analytical solution of steady states

An analytical solution in a closed form of the B4 converter working with a proposed optimized half a period switching symmetry is presented. The proposed switching strategy provides a good current tracking capability and minimum switching frequency. The analytical solution may be applied for the B4 converter connected to highly unbalanced grids. The method enables to analyze quickly B4 converter current responses in steady states for different grid filter topologies.