No abstract

In this study, the equation for the reactive and harmonic power compensation of a shunt active power filter (APF) system has been derived by studying the power exchange mechanism and power tetrahedron phasor diagram. The switching dynamics of a voltage source inverter (VSI)-based three-phase, three-wire (three-leg /half-bridge) shunt APF system with hysteresis band current control has been studied and verified by simulation. The relation between the design parameters and their effects on the active losses has also been identified. Detailed calculation and extensive simulation have been performed for a three-phase, three-wire shunt APF implemented in a 400V L-L distribution system, as an example, to study the effects of design parameter selection and their role in active power loss calculation. Simulated and calculated results are presented for the important design parameters for different switching frequencies together with their associated losses and kVA ratings. The procedure can be followed to design the parameters for other topologies, such as three-phase, four-wire or single-phase systems.

Abstract. This paper presents a technical review of power quality problems associated with the renewable based distributed generation systems and how custom power devices (CPD) such as STATCOM, DVR and UPQC play an important role in power quality improvement. IEEE and IEC standards for grid connected renewable energy systems are one of the critical points of interest for the selection of custom power devices. PV and wind energy systems integration issues and associated PQ problems are discussed. The role of CPDs in enhancing the integration of renewables and providing quality power through custom power park are described.

No abstract

No abstract

The increased penetration of photovoltaic (PV) distributed generation (DG) often connected to grid through dc -ac interface has made islanding detection an important and challenging issue for power engineers. Several methods based on passive and active detection schemes have been proposed in the literature. Although passive schemes have a large nondetection zone (NDZ), concern has been raised about active methods because of their degrading effect on power quality. Therefore each grid-connected PV systems needs to be EN50438 compliant to ensure proper interface and power quality standard. This study proposes a db4 wavelet-based passive islanding detection scheme with almost zero NDZ for dc -ac inverter interfaced grid-connected PV DGs. The key idea is to utilise spectral changes in the higher frequency components of voltage at the point of common coupling, which occur after an islanding condition. The effectiveness of the proposed method is tested in simulation of a PV DG system and validated experimentally with an actual 7.5-kW grid-connected inverter system using the dSpace DS1104 DSP. The designed detection algorithm has been computationally less burden on the DSP.

This paper focuses on the modeling of mechanical and structural vibrations in wind turbines due to the occurrence of electrical faults and an effective means of suppressing the vibrations with flexible alternating current transmission systems (FACTS) devices. A detailed model describing the dynamic interaction between the mechanical and the electrical subsystems of the turbine is presented. The model captures the effect of grid faults on the mechanical vibrations of drivetrain, flexible rotor blades and tower. Numerical investigation reveals that electrical disturbances have a significant impact on the mechanical/structural vibrations. In fact, the occurrence of severe vibrations due to voltage sags may compromise safe operation of the overall plant. The application of FACTS devices is then considered to suppress the effect of electrical fault-induced vibrations. The performance comparison of static synchronous compensator and unified power quality conditioner devices in improving the mechanical/structural response has been carried out. A fault scenario compliant with Irish grid code has been simulated. Simulation results show that FACTS devices are successfully able to mitigate vibrations due to electrical faults, and they can be conveniently applied to stabilize the generator shaft speed, drivetrain oscillations, edgewise blade vibrations and tower responses. Further, superior performances of the unified power quality conditioner as compared with static synchronous compensator are also observed under certain conditions with increased fault duration.

No abstract