Summary
The advantage of grid‐to‐vehicle power over vehicle to grid is that the existing power grid infrastructure and technology are able to support its operation. In this paper, a regulation operation framework for grid‐to‐vehicle–based plug‐in electric vehicle (PEV) aggregator is proposed. Based on that, PEVs can provide regulation services during charging. The objective function consider the influence of regulation services on the energy of battery charging for PEVs and the constraint of systems for battery charging power of PEVs, achieving the maximum aggregator earnings. A regulation algorithm is proposed for the aggregator to schedule PEVs. The algorithm considers the constraint of PEVs battery capacity and reduces the communication traffic between the aggregator and the PEVs. Simulation results indicate that the optimal scheduling can not only increase the earnings of the aggregator but also reduce the charging cost of PEV owners on the basis of meeting the charging requirements of PEVs.
In this study, a direct torque control (DTC) strategy based on a novel switching table for induction motor drives fed by the eight-switch three-phase inverter (ESTPI), which is the post-fault reconfigured topology for the three-level neutral-pointclamped inverter with the open-circuit fault occurring in a leg, is proposed to reduce the torque ripple and suppress the dc-link capacitor voltages offset. The influence of each basic voltage vector provided by the ESTPI on the stator flux, the electromagnetic torque and the dc-link capacitor voltages is analysed in detail, and the causes of the torque ripple and the capacitor voltages offset are also revealed. To suppress the dc-link capacitor voltages offset, a hysteresis comparator is added to regulate the dc-link capacitor voltages. Based on that, an optimised switching table to achieve not only torque ripple reduction but also dc-link capacitor voltages offset suppression is proposed. The feasibility and the effectiveness of the proposed DTC strategy are verified by simulations and experimental results.
During the operation of power capacitor, leakage, expansion and other abnormal phenomena may occur due to overvoltage, tide, thermal degradation and harmonic overload. Failure to monitor the performance and state of power capacitors in time may lead to power accidents, which will affect the safe operation of power system. Therefore, the monitoring method of performance of power capacitor was studied in this paper. Firstly, the defects and shortcomings of the existing monitoring methods were pointed out based on the analysis of the characteristics of power capacitors. Then the dielectric loss tangent was selected as the characteristic parameter to measure the performance, and the detection principle was proposed. After that, the distributed on-line monitoring system based on WiFi wireless communication was designed against the operating environment of power capacitors in substation, which included the overall scheme, the local signal detection terminal taking DSP as the main control unit and the centralized human-computer interaction designed in LabVIEW. Finally, the design system was tested. The results show that the measurement error of characteristic parameter is less than 10%, and the accuracy of state discrimination is 100%, so the design system have advanced technique and functionality. In addition, higher monitoring efficiency can be achieved because the performance of multiple power capacitors can be monitored at the same time by the distributed monitoring. Therefore, the system has high practical and popularization value.
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