This paper presents a load frequency control (LFC) by using distributed energy storage systems (ESSs) and plug-in electric vehicles (PEVs) in a large power system with MW-level distributed PV generation. The ESSs are controlled to mimic virtual inertia. Controls are done in two levels: central and local. An optimal virtual inertia is calculated considering the total PV power variation in a control area. Based on this, central ESS power command is decided and by coordination, this central ESS power command is distributed to the local ESSs to emulate the optimal virtual inertia. PEVs are used for the LFC considering user convenience, availability and state of charge (SOC) of the batteries. Effectiveness of the proposed method to provide LFC is verified by numerical simulation results.
This paper presents a new instantaneous current control to obtain an instantaneously flat torque waveform with smaller torque ripples of switched reluctance motors (SRMs). The proposed current control is based on table lookup. By geometric insights for the machine and finite element method based analysis, ideal current profiles for the flat torque are generated. Some simulation results are presented to demonstrate the validity of the proposed control, which are verified by experiment.
This paper discusses how to improve the efficiency of switched reluctance motors (SRMs) by means of a step-skewed rotor (SSR). The cross-sectional configuration of the tested SRM with SSR, including the size and shape of the salient poles, was nearly identical to that of a conventional SRM. The tested SRM was divided into three stacks, of which only one rotor was skewed. The skewed angle was designed to reduce both the torque ripple and the radial force. Experiments were carried out to confirm the effectiveness of efficiency improvement of the SRM with SSR: a maximum efficiency of more than 90% was achieved. Compared with the efficiency of a conventional SRM, the efficiency of the proposed SRM with SSR was greater by more than 10 percentage points.
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