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This paper proposes a novel three-phase rectifier which combines the benefits of diode bridge and PWM rectifier with high efficiency and low THD, making it suitable for high power DC fast charging applications. It targets at achieving high efficiency and control simplicity compared to conventional PWM type rectifier. The operation principle, current compensation method at voltage zero-crossing point and power loss analysis are presented and analyzed. Besides, simulations were performed in Matlab/Simulink and a 60kW prototype using IGBT modules and fast recovery diode bridge rectifier was built and tested. The experiment results manifest the merits of proposed three-phase rectifier with 99.5% peak efficiency and 9.2% THD.

In this paper a novel phase-shift autotransformer is proposed to reduce the required kVA capacity in multi-pulse rectifier applications with utility interface. The structure and operation principle of proposed autotransformer are presented and analyzed in detail. Design criteria of turn ratio, phase-shift angle and equivalent capacity for the proposed autotransformer is illustrated. It can be shown that the proposed method can significantly lower the kVA rating of transformer to 9.38% of output power. Simulations in Matlab/Simulink and experimental results of a 40kW prototype further validate the proposed concept.

Air supply flow directly affects proton exchange membrane fuel cells' (PEMFC) performance, when air supply flow exceeded PEMFC demands, lost of heat energy increased and power consumption of air-compressor increased too, so efficiency of generating current was reduced. Whereas, when air flow was under its demands, FC stack would be damaged with output power of PEMFC increasing in some extant. But in PEMFC running, air supply flow lagged FC stack output power changing, so Elman ANN was proposed to predict it in advance, and the result as given value in air supply control system. It adopted Fuzzy-PID compound control to make air supply flow following output power of PEMFC changing. Simulation results showed that Elman ANN predicted air parameters effectively, and Fuzzy-PID compound controller improved dynamic performance of air supply control system distinctly better than traditional PID controller. It satisfied PEMFC demands in electric vehicles (EV).

In view of the main disadvantages of current cascade multilevel inverter (namely, it requires a lot of independent DC source), propose a new type of cascade multilevel inverter, which reduces the number of DC sources by improving the the utilization rate of DC sources. The new type of inverter is not only simple in structure, but also simple and effective in control algorithm that the simulation results certify that this new type of cascade inverter is feasible.

In order to solve the problem that the existing Rubber-Tyred Gantry (RTG) Crane consumes massive generating/braking energy through resistance, produces plenty of heat , causes excessive fuel consumption and exhaust emission during working, the relation of energy flows of the existing system is analyzed and the value of the improvement of energy saving is confirmed in the paper. Firstly, the constitution and principle of the RTG energy saving system are proposed. In addition, the topology and principle of the bi-directional DC/DC converter are anatomized. Thirdly, after analyzing a model for supercapacitor voltage equalization strategy, a voltage equalization method for RTG energy saving system is proposed, namely active voltage equalization method, and design of active voltage equalization circuit parameters and control strategy are given. Finally, simulation analysis of the series connection of supercapacitors module is performed.

A bidirectional converter for electromechanical brake/the recycling of power generation energy is proposed in this paper. The gain of the converter is high. Since the converter use the technique of passive lossless buffer and synchronous rectification, the main switches achieve the technique of soft switching. Meanwhile the conversation efficiency is high too. Some experimental results and analysis of theory are given to verify the effectiveness of the proposed bidirectional converter.

Aiming at the single-phase current five-level inverter, the thesis analyzes the reasons for unbalanced inductor current, introduces some types of present strategies for balancing the inductor current through current sharing, and points out separately the current sharing principles for these strategies, comparing their advantages and shortcomings and then puts forward a new strategy for hysteresis control. Furthermore, the thesis analyzes the principles of this strategy and takes some stimulation with the same parameters as those of traditional hysteresis control strategies and finally comes up with the results to confirm the conclusion.

Based on a kind of hybrid control photovoltaic grid-connected cascaded inverter proposed by the author, this paper proposes a simple method by which we can confirm the triggering angles of the unit inverter with the step wave overlap control mode, computes the output power of each unit inverter, proposes the operation mode exchange solution to solve the unbalanced output power problem of the cell modules, through the analysis and computation, introduces how to choose and match the photovoltaic cells of various cascaded units. The simulation results show the validity of the proposed method.

This paper proposes a hybrid control method for cascaded inverter with step waveform and instantaneous current control. With this method, one part of the cascaded unit uses step waveform control, and the other part of the cascaded unit uses instantaneous control. The output voltage comes from the two parts in series. This method can decrease the switching time, reduce the switching loss. The structure of the system is very easy. The theory analysis and simulation is done, and the simulation results show the validity of the proposed method.

Besides effectively reducing the voltage stress of switches, the cascaded multilevel inverter could also improve the quality of output waveforms by addition of waveforms. The step waveform addition is a usual method. The addition could reduce the loss of switches, but the introduced angle of flow calculating methods of cascade inverters based on step waveform addition are only suitable for cascaded inverters with the same voltage step. To this situation, an angle of flow calculating method of inverters with the different voltage step is proposed in this paper. The method is very suitable for the application of solar battery cascaded inverters and fuel battery cascaded inverters. The method follows the equal area principle, and the online calculation is realized by some constraint conditions. Finally, the correctness of the method is validated by simulations.

This paper introduces the new PFC integration control chip-UCC28019, provides the PFC circuit based on UCC28019 and the essential circuit parameter computation method. The actual power factor is 0.998 through testing a 350 W prototype, this paper presents the experimental waveforms. The experimental results have proved that the PFC circuit has these characteristics: simple circuit, conveniently to debug, high power factor, complete protection features, reliable and stable work.

A model for supercapacitor voltage equalization strategy is analyzed, and on this basis a supercapacitor voltage equalization method for Rubber Tyred Gantry Crane (RTG) energy saving system is proposed, namely active voltage equalization method based on Buck-Boost converter. The equalizing speed of the proposed method is fast. Firstly, the working principle and process of the voltage equalization circuit is analyzed in detail. In addition, design of active voltage equalization circuit parameters and control strategy are given. Finally, simulation analysis of the series connection of supercapacitors module is performed. Results show that this method for equalizing voltage can avoid over-voltage of each cell and possess practicable and high value for supercapacitor RTG energy saving system.

A novel method (AC-DC-AC) to produce symmetrical four-phase voltage is presented in this paper, The main circuit is the four-bridge topology and the control method is the three-dimensional voltage space vector control. This method has the merits of novel design, high conversion efficiency, good waveform quality and the method is easily to be realized.The power circuit topology of realizing four- phase power transmission is three-phase four-bridge arms inverter. In this paper, firstly, the four-phase inverter mathematical model is analyzed, via the analysis, the phase voltage and line voltage switching function expressions and their conversion matrixes are got, The method of describing four-phase symmetrical sine voltage with three-dimensional space vector is analyzed, four-phase / three-phase coordinate conversion matrix is derived, through the three- dimensional space vector analyses, these are reached: (a) The movement locus of four-phase symmetrical voltage parameters is a ellipse;(b) The control model of four-phase symmetrical voltage may be three-dimensional space vector pulse-width modulation, lastly, these proposed techniques have been verified by simulation and experimental results.