Search

With the deepening of electricity market reform in China, the competition in the electricity retail market becomes increasingly intense. Electricity retailers (ERs) need to explore new business models to enhance their competitiveness in the retail market. Meanwhile, with the improvement of industrial production and people's living standards, more and more nonlinear electrical equipment have been put into use, leading to severe harmonic pollution problems. Harmonic pollution causes loss of electricity, resulting in the economic loss of customers, especially for large industrial customers. In the above contexts, this paper proposes a novel business model that incorporates harmonic control as a value-added service into electricity retail contracts for utility-owned ERs. Both utility-owned ERs and customers can benefit from the designed business model. For customers, it helps them to improve the power quality while saving the electricity cost. For ERs, it helps them to cultivate the customer loyalty and improve the customer satisfaction. A case study is performed to demonstrate the effectiveness of the proposed business model. [ABSTRACT FROM AUTHOR]

In this paper, a special control solution called virtual voltage source (VVS) is developed for no-load tests of induction machines. This concept is applied to a 2 × 27 MVA high-power machine test bench where the test bench is requested to precisely characterize, e.g., 3 MW machines at no-load currents. The developed VVS thoroughly solves the stability issue of induction machines at low-speed ranges. A set of optimizations is presented here that systematically improves the voltage precision of the test bench. Experimental results prove that the proposed concept achieves 0.08–0.12% voltage unbalance, less than 3% current unbalance, with less than 0.3% harmonic-voltage-factor, and verified by more than 100 induction machines. [ABSTRACT FROM AUTHOR]

With the rapid development of China high-speed railway, the low frequency oscillation (LFO) of electrical quantities appears more often recently and leads to some severe problems of train operation. To improve the traction line-side converter control and suppress the phenomenon economically and effectively, a model-based predictive direct power control (MPDPC) approach is proposed in this paper. The approach adopts a discrete-time model of traction line-side converter in d–q reference frame to predict the future values of the input active and reactive power. The optimal switching state is selected by minimizing a cost function of power to evaluate the power errors at the next sampling time. Through the theoretical analysis and simulations, the performance of MPDPC is compared with traditional transient direct current control (TDCC) that is widely adopted in China Railway High-Speed 3 electric-multiple-unit. The real-time online simulations based on Real-Time Laboratory (RT-LAB) are also realized to further validate the results. Moreover, two vehicle-grid cascade simulation systems are constructed, and the LFO suppressing capability of MPDPC and TDCC is compared. Finally, the steady-state characteristic, dynamic characteristic, and LFO suppressing capability of MPDPC are demonstrated through the analysis of key performance indexes. [ABSTRACT FROM AUTHOR]

With the increasing demand of electricity, the development of the urban power grid has drawn a lot of attention in China. In order to focus on the analysis of an urban power grid, the remaining part of the large-scale power grid used is to be reduced. The accuracy of the equivalence is key to urban power grid research. In this paper, a multistep dynamic equivalent method based on district dividing is proposed. Based on the electrical distance, voltage level, and geographic location, the external system is divided into outer layer, inner layer, and buffer subsystem. Each district is separately reduced by different methods. The proposed technique is illustrated by a real large-scale power grid in the south of China. [ABSTRACT FROM PUBLISHER]

Due to the growing demand on renewable energy, photovoltaic (PV) generation systems have increased considerably in recent years. However, the power output of PV systems is affected by different weather conditions. Accurate forecasting of PV power output is important for system reliability and promoting large-scale PV deployment. This paper proposes algorithms to forecast power output of PV systems based upon weather classification and support vector machines (SVM). In the process, the weather conditions are divided into four types which are clear sky, cloudy day, foggy day, and rainy day. In this paper, a one-day-ahead PV power output forecasting model for a single station is derived based on the weather forecasting data, actual historical power output data, and the principle of SVM. After applying it into a PV station in China (the capability is 20 kW), results show the proposed forecasting model for grid-connected PV systems is effective and promising. [ABSTRACT FROM PUBLISHER]

Reliable emergency power supply is essential to fire services installations. However, the extent of reliability and availability of standby generators in Hong Kong buildings are a query so far. This paper presents a generator reliability survey in Hong Kong. The results regarding fault events, reliability, and availability of standby generators are shown by means of analysis of their fault/failure records. Recommendations on reliable operation of standby generators are also provided in the paper. [ABSTRACT FROM AUTHOR]