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This study presents a H∞ mixed-sensitivity robust control design to improve the overall damping performance of lowfrequency oscillations for power systems with doubly fed induction generator-based (DFIG) wind power generation. The supplementary damping controller is designed in the linear matrix inequality framework which allows the placement of the closed-loop poles inside a pre-defined region for improved stability. The damping signal is implemented at the reactive power modulation of the rotor-side converter of the DFIG wind turbine (DFIG-WT). The damping contribution of the power oscillator damper is compared with that provided by the power system stabiliser (PSS) of the synchronous generator (SG). State-space system analysis and time-domain simulations show the capability of DFIG-WT to enhance the overall damping of the oscillatory modes even if PSSs are not installed at SG s. Also, the designed controller shows a robust performance to wind speed variations. The performance evaluation is based on the revised two-area four machines system and the revised New England 39-bus system. [ABSTRACT FROM AUTHOR]

Hybrid micro‐grids are one of the most viable solutions to the present day problem of integration of renewable energy into existing power systems. With various options available for implementation of hybrid micro‐grids, the stability of such systems has to be ensured before they can be implemented. Further, conventional micro‐grid operational studies do not take into consideration the constraints set by the grid codes. This study analyses three types of interconnections, possible for implementation of hybrid micro‐grids, taking into consideration the transient stability and grid code constraints. The hybrid micro‐grid considered comprises a synchronous diesel generator and an inverter‐based distributed generation. The results and analysis are conducted by time‐domain simulations using MATLAB/Simulink software. The results provide the actual operational limits of possible micro‐grid interconnections under the set of given constraints. [ABSTRACT FROM AUTHOR]

Integration of dynamic grid support is required for distributed power systems that are interconnected with medium voltage grids. This study proposes a comprehensive control solution to enhance fault ride through (FRT) capability for utility‐scale photovoltaic (PV) power plants. Based on positive and negative sequence control schemes and PV characteristics, the approach alleviates dc‐bus double‐line‐frequency ripples, reduces voltage stress on inverter power switches and DC‐link capacitors, and minimises undesirable low‐order voltage and current harmonics that are presented on the ac side. The study proposes a new feature to achieve superior FRT performance by using the overload capability of grid‐tied inverters. A weak electric grid is used for the test case including a wind turbine induction generator, diesel engine driven synchronous generators and various loads. A comprehensive simulation verified the capability of the proposed control schemes for mitigating the voltage dip, enhancing the voltage response and further improving the stability of interconnected distributed generation in reaction to severe unbalanced voltage conditions because of asymmetrical grid faults. [ABSTRACT FROM AUTHOR]