Advanced Materials Research Vols. 953-954

Abstract: This paper investigates the “Vehicle-charging mode” and the “Battery-changing mode” of the electric vehicles. Firstly, it analyzes the vehicle-charging time, the battery-changing time and the charging power under two modes. Secondly, this paper searches into different sorts of charging and sets up three scenarios based on the differences: scenario1, disorderly; scenario2, continuous; scenario 3, off-peak. Thirdly, this paper considers the combination of generator sets that reaches the requirements of electric vehicle charging based on the characteristics of different sorts of charging, concerns the increased fuel costs, O&M costs and start cost generated along, and draws conclusions with the comparison of the elements.

Abstract: The plug-in electric vehicles (PEVs) would exert inevitable impact on distribution system operation due to the spatial and temporal stochastic nature of the charging load. Based on the probability distributions of battery charging start time and the initial state-of-charge (SOC), the spatial and temporal charging loads of PEVs are analyzed on load nature and charging behaviors among different functional distribution areas. Taking IEEE 33-bus distribution system as an example, the Monte Carlo method is adopted to simulate charging load under different charging strategies and charging places for assess the impact on network loss and nodal voltage using standard load flow calculations. The results show that the choice of control strategies can improve the impacts of PEVs charging on distribution grid; a well-developed public charging infrastructure could reduce the stress on the residential distribution systems; optimal assignment of PEVs charging in residential area and industrial or commercial areas would provide a reference for charging infrastructure construction.

Abstract: The use of clean alternative fuel and new combustion mode is one of the most effective methods of further reduction of NO_x and smoke emissions at diesel engine. High thermal efficiency and ultra-low NO_x and PM emission of engine in HCCI combustion mode can be realized at low and medium load. However, some problems such as hard control of ignition timing and narrow operating range still exist.For the sake of expanding the operating range of HCCI (Homogeneous Charge Compression Ignition) engines and explore the scientific methods to realize the ultra-low emission with DME (Dimethyl Ether) as alternative fuel. Experimental Research on the characteristics of PCCI-DI (Partial Premixed Charge Compression Ignition – Direct Injection) combustion is carried out on a single cylinder and naturally aspirated direct injection diesel engine. Results indicate that PCCI-DI DME engine has lower peak cylinder pressure and lesser rise rate of pressure. The engine also shows up an obvious two-stage heat-release characteristic. Compared with HCCI DME engine, peak value of two heat-releases reduces, the position of the first peak almost has no change and the position of the second peak shifts to the position later than TDC (Top Dead Center).

Abstract: Performance test of the engine fueled with DME-methanol blends was conducted on a 4102BQ diesel engine. The results show that: by increasing the fuel pump plunger diameter, delaying injection timing, and reducing nozzle-opening pressure, the rated power of the engine, fueled with DM90 blends (Mass ratio of DME and methanol is 9:1), descended 13.97% relative to the original diesel engine, but the soot emissions did not appeared in all test conditions. In full load condition, NO_x emissions declined by 55.1%, CO emissions fell by 65.8%, but HC emissions increased by 21.6%.

Abstract: To further study the performance of the engine fueled with DME-diesel blends, the indicator diagrams of a two-cylinder four-stroke engine are recorded at 1700r/min and 2300r/min under different load, the heat release rate and the rate of pressure rise are calculated. The results show that: when fueled the engine with D20 blend (Mass ratio of DME and diesel oil is 2:10) and optimizing the fuel supply advance angle, the maximum cylinder pressure decreases by 10% averagely and its corresponding crank angle delays 2°CA, the maximum rate of pressure rise is relatively lowers about 20%, the beginning of heat release delays，but combustion duration do not extend, and the centroid of heat release curves is closer to TDC (Top Dead Center), maximum combustion temperature drops 70-90K. These results indicate that the mechanical efficiency will be improved and, NO_x emissions and mechanical noise will be reduced when an engine fueled with DME-diesel blends.

Abstract: In this study, simulation model on combustion process of a diesel engine was developed and the results were validated by experiments. Then the compression ignition was switched into PCCI (Premixed Charge Compression Ignition) in order to understand the effects of individual parameters on PCCI combustion and provide the reference for the further studies of testing and simulation. The results illustrate that the lower compression ratio extends the ignition delay and enhances fuel-air mixing and improves PCCI combustion. In addition, the oxygen concentration in cylinder is highly diluted as the EGR (Exhaust Gas Recirculation) rate increases and the NOx (Oxides of nitrogen) emissions are effectively depressed as EGR rate over 30%. Moreover, the reduction of main injection fuel quantity results in a decrease reactivity and peak heat release rate in combustion.

Abstract: This paper presents a Monte Carlo-based method used in modeling electrical load occurring from electric vehicle battery charging and assessing its impact on the distribution system in case of an extensive residential use of electric vehicles. The state of charge and starting time are parameters considered stochastic in nature. As such they can be appropriately represented by a standard distribution function. In this paper a case study is demonstrated using a 22-kV distribution network located in an urban service area of the Provincial Electricity Authority (PEA). Based on the PEA’s typical daily load profile, a new load profile which includes the effect of electric vehicle charging is developed. The expected impact on the line overload and quality standard of voltage caused by electric vehicle charging can be forecasted. Results of the study are applicable for system planning to accommodate an expansion in the network capacity due to the growth in electric vehicle number.

Abstract: In connection with the increasing fuel costs and decreasing incomes during the crisis electric vehicles are becoming more and more popular with drivers. With mass growth of using the electrical vehicles a possibility of transmission congestion can take place. While charging the vehicle by means of residential distribution there is a risk of facing electric power supply degradation and local accident conditions in grids. One of the basic current problems is that of the load curve irregularity, i.e. the existence of the peak hours and minimums in demand of the electric power. In its turn the load curve irregularity can cause unacceptable frequency oscillations in power systems. The development of charging station systems will lead to the increasing of the morning and evening demand of the electric power. It requires key investments in generators designing and improving the distribution networks, which in its turn will cause limitations in the number of charging stations and the electric vehicles expansion. Cost differentiation depending upon charging duration time can become an incentive to use charging stations during the periods of the minimum electric power consumption. A possibility of the electric vehicles usage as a means of smoothing the electric power consumption daily schedule is shown in the article. The evaluation of rationality of the electric vehicles integration as a power component in the network was made as well.

Abstract: In some low velocity electric vehicle system, Brushless DC motor is used for the main traction motor. However, the low-velocity stability should be guaranteed, especially with the suddenly-changing load, the velocity response should be more quick and the overshoot should be small, all of above can make the vehicle more comfortable. The traction system is controlled by a current loop and a velocity loop, so a new method is proposed, that PI control strategy is in the current loop and the active disturbance rejection controller is in the velocity loop to restrain the bad effect results from suddenly-changing load. This active disturbance rejection controller is composed of a tracking differentiator, an extended state observer, a nonlinear state error feedback controller, and etc. The parameters of the controller are optimally designed, and the simulation results show that this control strategy can effectively restrain the suddenly-changing load and improve the vehicle’s low velocity performance.

Abstract: With the popularity of electric vehicles, the impact of charging power on the original grid load is increasingly prominent. Electric vehicles can realize the benign interaction with power grid through the V2G technology. The mathematical model is solved with genetic algorithm in this paper based on the objective function as the minimization of daily charging cost. Constraint conditions such as maximum charge and discharge power limits and state of charge are considered. By analyzing the charge and discharge control of single car and the influence of electric vehicles’ charge and discharge on power grid, it is concluded that charge and discharge control strategy proposed in this paper can optimize the operation of the power grid and realize win-win situation of the user and the power grid with the time-of-use electricity pricing mechanism.