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Railway static power conditioner(RPC) can effectively overcome the shortcomings of traditional conditioner which has poor negative sequence and harmonic compensation effect, it provides a new way to control the power quality of high-speed railway. However, the traditional two-level RPC device occupies a large area, and it will also encounter direct current bias magnetic problem, which distorts the voltage of the system and the excitation current distorts to form peak waves. At this time, the harmonic content increases dramatically and the reactive power loss of the transformer increases. In this paper, the MMC topology and RPC structure are combined to form the MMC-RPC topology, which is directly connected to the traction power supply arm, eliminating such deficiencies as large floor area, large loss and distortion of output current waveform of the booster transformer. At the same time, this paper also studied the capacitor voltage equalization control and circulation suppression strategy of MMC-RPC topology. Finally, the MMC-RPC topology simulation model is built to verify the feasibility and effectiveness of the topology structure and control strategy.

Scratch is a popular programming platform with plenty of learning resources. However, it is quite difficult for users to find suitable resources. In this paper, in order to provide the resources which the users require, we propose a Scratch Recommendation Framework Adaptive to User Interest Drifts (SRFA-UID). First, a user interest drifts model is designed, which adopts the time decay factor and the weights of operation behaviors to track users' dynamic interest. Then, on the basis of users' current and historical interest, we calculate their combined user similarity. Next, we present a novel two-hop-algorithm to update users' friend community. Considering the preferences of the whole friend community, the Computational Thinking (CT) skills of users and the impact factors of items, we put forward a recommendation function to obtain items that are related to users. For an item, the function can calculate its F value to determine if we can recommend it to the users. Experimental results show that SRFA-UID performs better than other state-of-the-art methods in the Scratch dataset.

There are some disadvantages in mechanism tap-changers, 10KV no-contact tap-changer on-load voltage regulator is proposed. The compensated principle is used to regulate output voltage and the switch process is completed by SCR. So it has fast dynamic response and low harmonic content, and produces no electric arc in the switching process. At the same time, the advanced compensation technology of combined winding and the optimized topology are adopted to make more compensation series and higher precision of voltage regulation. Based on the principle and topology, the power flow is analyzed in detail, and the inner nature of its operation is further expounded. The experimental results show that the topology is feasible and the theoretical analysis is correct.

In dealing with the parameter design and the investment optimization of hybrid active power filter, we comprehensively consider the price, the reactive power compensation and the filter effect in a new mixed algorithm of genetic theory and particle swarm optimization. On this basis, the multi-objective mathematical model of capacity assignment is created and the penalty function theory is applied; and then, the multi-objective design is converted into a single-objective design, making the capacity assignment simple and flexible. Secondly, simulation analysis is carried on the power systems computer aided design/electromagnetic transients including DC(PSCAD/EMTDC); the results demonstrate that the cost performance of the hybrid active power filter is improved by using the proposed method. Finally, experimental results and comparison analysis are presented to confirm the above-mentioned method.