This paper presents a design strategy for LCC/S compensation network based stationary wireless charging system to obtain both constant voltage and constant current characteristics without the need of ...additional electronic components compared with the conventional approaches while maintaining input zero phase angle (ZPA) condition as well as soft-switching for a wide range of load variations. The proposed concept is validated by both theoretical analyses and simulation results.
This paper proposes a design and control method for double sided LCC compensation network based wireless charging to obtain both constant voltage (CV) and multiple constant current (CC) ...characteristics which is suitable for stationary charging system without the need of additional electronic components requirement while maintaining input zero phase angle (ZPA) condition for a wide range of load variations. Proper control strategies are also presented to realize soft switching of power switches. The validity of the proposed concept is demonstrated by both theoretical analysis and computer simulations. Experimental results verify the feasibility of the proposed system.
Temperature is a crucial variable to evaluate and measure the energy consumption and efficiency of the Air Conditioning & Mechanical Ventilation System (ACMVS) in the buildings. To ensure the ...performance and efficiency of the ACMVS, an experimental study of long-term reliability for temperature monitoring to ensure the accuracy of temperature sensor measurement is carried out in this paper. Four experiments were conducted for the influence of temperature measurement under different operating conditions in the ACMVS, which are insertion depth, humidity, tube vibration, and water mixing. Finally, the drift of two types of temperature sensors (RTD and Thermistor) commonly used in industry are compared under the condition of long-term reliability measurement. The results showed that the non-waterproof thermistor installed on the open thermocouple sleeve at least 2/3 of the pipe where the temperature sensor is inserted at 10D away from the water mixing point could provide the best temperature reading.
With the development of power electronics, renewable energy resources like wind and solar continue to gain worldwide popularity in order to release the environmental pressure. To achieve the optimal ...performance throughout the project lifetime, this paper proposes a long-term planning model for the microgrid extension project in a small island, which takes the operational life, salvage value and the inflation rate into account. Based on the proposed model, a multi-step optimization method is then developed to enhance the computational efficiency while minimizing the microgrid net present cost (NPC) as much as possible. With the proposed model and method, a long-term optimization scheme can be designed for the microgrid extension of islands. Comparisons between the integrated optimization method and the proposed method have been made. Simulation results demonstrate that the proposed technique is effective.
As a promising topology, modular multilevel converters (MMCs) are widely deployed for high voltage direct current (HVDC) systems. To directly calculate the equilibrium point of MMC-HVDC, this paper ...establishes the system model considering the dynamics of the capacitor voltages, the output current and the circulating current. The established model is then analyzed to exhibit the interactions between the state and the control variables. Without simulations, a trust-region algorithm is proposed to determine the equilibrium point of the MMC-HVDC system, which decreases the time cost compared with the simulation. For the verification of developed method, an MMC-HVDC system is tested. The results demonstrate that the derived model and the proposed algorithm can provide accurate equilibrium point with high efficiency. On the basis of the developed algorithm, the model and parameter impacts are also analyzed.
The utilization of distributed generators, renewable energy, and energy storages boosts the microgrid development. Among various microgrids, the building microgrid (BM) tightly related with our daily ...life is also experiencing the improvement. One of the most obvious changes for the BM is the penetration of DC sources and DC loads, which forms the hybrid AC/DC BM. Because of the relatively small space and people density, the arc hazard should be paid more attention for buildings. In the meantime, the development of hybrid AC/DC BM will make the arc analysis more complicated, in which the AC and DC sections are closely interlinked. As the core interlinking part, the interlinking AC/DC buses are important to the safety guarantee of the hybrid AC/DC BM, which requires the main concern in the arc analysis. For the safety maintenance, this work firstly analyzes the hybrid AC/DC BM. Based on the arc current and the incident energy, an arc analysis flow is then designed for the interlinking AC/DC buses. Through the respective analysis for the interlinking AC and DC buses, a linear relationship is detected between the AC/DC loads and the arc current as well as the incident energy. By comparisons between the interlinking AC bus and DC bus, the qualitative and quantitative results are also illustrated for their arc differences. With the larger value, the increasing ratio of DC arc current could be employed as the detection signal. As larger loads cause larger arc current and incident energy, distributed loads are preferred to aggregated loads.
Aiming at the faults pass-through between the distribution network and the AC-DC hybrid micro-grid (HMG), this paper proposes a concept of the series compensation link (SCL) which has been inserted ...between a distribution network and a AC-DC HMG to compensate HMG voltage and limit excessive fault current as well. The basic structure and operation modes of the SCL are introduced firstly. Then, based on deriving the mathematical models of the SCL in abc-three-phase coordinate frame and in dq synchronous rotation coordinate frame, a compound compensation and current limiting strategy is designed. A series compensation transformer (SCT) is designed. Finally, the effectiveness of the SCL and its control strategy have been verified by simulations.
In hybrid micro grid, the bidirectional AC/DC power converter (BIC) is required to guarantee voltage stability and power balance of AC and DC sub-grid. Based on analyzing the main circuit of BIC, ...this paper proposes a control strategy that not only realizes the function of bidirectional power conversion but also suppresses harmonic current. This control strategy combines the harmonic current detection algorithm based on Fryze-Buchholz-Depenbrock power theory and bidirectional power converting method. The control command for controlling the BIC to suppress the harmonic current is obtained by the proposed control strategy. Finally, the validity and practicability of the control strategy are verified by simulations.
This paper presents an integrated series-parallel microgrid(MG), where a few distributed generation(DG) units in series type are used to form a DG string, then DG strings supply power to the common ...load in parallel type. With this structure, low-voltage devices could be integrated into MG without DC-DC boost converters. It provides a more flexible and efficient way to form higher voltage level MG. But it is difficult to find a decentralized control method to achieve power balance for this integrated system because of the difference between power transmission characteristics of parallel and series converter system. For this proposed MG in island mode, a unified distributed control strategy is proposed. With low bandwidth communication, accurate power sharing can be realized by exchanging information between the first converters connected to the bus of adjacent DG strings and between adjacent converters inside each DG string. Because the central controller is not used, the communication pressure of the system is reduced and the reliability is guaranteed. Simulation test has verified the feasibility and validity of the proposed control strategy.
This paper proposes a system-wide optimal coordinated operation method for a multi-energy microgrid (MEMG), which takes both electric power flow and district heat network (DHN) constraints into ...consideration. The studied MEMG contains the renewable power generators (photovoltaic cells and wind turbines), electric boilers, combined heat and power (CHP) plants as well as battery storages. To exploit the potential of DHN for storing/releasing heat energy and improving the system dispatch flexibility, the coupling property of electrical and heat network, dispatch constraints, hydraulic balance and dynamic heat loss are investigated. Subsequently, the proposed operation model is formulated as a mixed integer linear programming (MILP) problem which can be solved by some commercial solvers. Three different cases for a comprehensive 33-eletrical-bus, 11-heat-node based test system are carried out to verify the effectiveness of the proposed model. Simulation results demonstrate that the proposed method contributes to an efficient operation and cost-saving energy management.
