Dynamic Equivalent Method of Motor Loads for Power Systems Based on the Weighted

Dynamic equivalence can not only largely reduce the system size and the computation time but also stress the dominant features of the system [1]-[3]. This paper firstly recommends the basic concept of dynamic equivalent and the status of both domestic and abroad development in this area. The most existing equivalent methods usually only deal with static load models and neglect the dynamic characteristics of loads such as induction motors. In addition, the existing polymerization method which is based on the frequency domain algorithm of induction electric machines parameters takes a long time to equivalent for the large system, then the new method based on the weighted is proposed. Then, the basic steps for dynamic equivalence with the weighted method are introduced as follows. At first, the clustering criterion of motor loads based on time domain simulation is given. The motors with similar dynamic characteristics are classified into one group. Then, the simplication of the buses of motors in same group and network is carried out. Finally, parameters of the equivalent motor are calculated and the equivalent system is thus obtained based on the weighted. This aggregation method is applied to the simple distribution system of 4 generators. Simulation results show that the method can quickly obtain polymerization parameters of generator groups and the aggregation model retains the dynamic performance of the original model with good accuracy, the active and reactive power fitting error is smaller as well.

Developing hierarchical CdS/NiO hollow heterogeneous architectures for boosting photocatalytic hydrogen generation

The hierarchical binary CdS/NiO hollow heterogeneous architectures(HHAs)with p–n heterojunction are constructed by a facile microwave-assisted wet chemical process for high-efficient photocatalytic hydrogen evolution reaction(HER)from water.The as-designed CdS/NiO HHAs are composed of hexagonal n-type CdS nanoparticles with a size in the range of 20–40 nm attaching to cubic p-type NiO hollow microspheres(HMSs)which are aggregates of porous nanoplates with a thickness of about 20 nm.The photocatalytic water splitting over CdS/NiO HHAs is significantly increased under simulated solar irradiation,among which the most active sample of CdS/NiO-3(the mass ratio of CdS to NiO is 1:3)exhibits the fastest photocatalytic HER rate of 1.77 mmol∙g^(−1)∙h^(−1),being 16.2 times than that of pure CdS.The boosted photocatalytic HER could be attributed to the synergistic effect on the proportional p–n heterojunction with special hierarchical hollow and porous morphology,an enhancement of visible light absorption,and an improvement of photoinduced charge separation as well as the photo-stability given by the composite heterojunction.This work shows a viable strategy to design the heterojunction with special morphology for the efficient hydrogen generation by water splitting utilizing solar energy.