Topology of a Bidirectional Converter for Energy Interaction between Electric Vehicles and the Grid

Self Cite

A novel, fully decentralized strategy to coordinate charge operation of electric vehicles is proposed in this paper. Based on stochastic switching control of on-board chargers, this strategy ensures high-efficiency charging, reduces load variations to the grid during charging periods, achieves charge completion with high probability, and accomplishes approximate "valley-filling". Further improvements on the core strategy, including individualized power management, adaptive strategies, and battery support systems, are introduced to further reduce power fluctuation variances and to guarantee charge completion. Stochastic analysis is performed to establish the main properties of the strategies and to quantitatively show the performance improvements. Compared with the existing decentralized charging strategies, the strategies proposed in this paper can be implemented without any information exchange between grid operators and electric vehicles (EVs), resulting in a communications cost reduction. Additionally, it is shown that by using stochastic charging rules, a grid-supporting battery system with a very small energy capacity can achieve substantial reduction of EV load fluctuations with high confidence. An extensive set of simulations and case studies with real-world data are used to demonstrate the benefits of the proposed strategies.

Section: Efficiency Analysis Of On-board Chargersmentioning

confidence: 99%

Decentralized Electric Vehicle Charging Strategies for Reduced Load Variation and Guaranteed Charge Completion in Regional Distribution Grids

Zhang

et al. 2017

Self Cite

“…In the high-voltage side of the converter, the both in-series capacitors C o1 and C o2 supply power to output. Stage 8 [t 7 , t 8 ]: After the time t = t 7 , switches S 2 and S 4 are in on state but S 1 , S 3 , S 5 , and S 6 are in off state. The equivalent circuit is illustrated in Figure 3h.…”

Section: Step-up Modementioning

confidence: 99%

“…Stage 8 [t 7 , t 8 ]: In Stage 8, the body diode D S5 is in forward bias, which provides a ZVS condition for S 5 . The green dashed line in Figure 5h shows this current path.…”

Section: Step-down Modementioning

confidence: 99%

Isolated DC-DC Converter for Bidirectional Power Flow Controlling with Soft-Switching Feature and High Step-Up/Down Voltage Conversion

Shen

Tsai

2017

Abstract:In this paper, a novel isolated bidirectional DC-DC converter is proposed, which is able to accomplish high step-up/down voltage conversion. Therefore, it is suitable for hybrid electric vehicle, fuel cell vehicle, energy backup system, and grid-system applications. The proposed converter incorporates a coupled inductor to behave forward-and-flyback energy conversion for high voltage ratio and provide galvanic isolation. The energy stored in the leakage inductor of the coupled inductor can be recycled without the use of additional snubber mechanism or clamped circuit. No matter in step-up or step-down mode, all power switches can operate with soft switching. Moreover, there is a inherit feature that metal-oxide-semiconductor field-effect transistors (MOSFETs) with smaller on-state resistance can be adopted because of lower voltage endurance at primary side. Operation principle, voltage ratio derivation, and inductor design are thoroughly described in this paper. In addition, a 1-kW prototype is implemented to validate the feasibility and correctness of the converter. Experimental results indicate that the peak efficiencies in step-up and step-down modes can be up to 95.4% and 93.6%, respectively.

“…Harmonic distortion will occur in the voltage and current on the AC (Alternating Current) side of the charging station because of the coupling between the rectifier and the power grid. The existing literature on this topic has mainly employed experimental testing [2,5] and simulation analysis [14,15]. However, the former method is only applicable to charging facilities under experimental conditions.…”

Section: Introductionmentioning

confidence: 99%

“…The increasing installation of nonlinear charging infrastructure in the form of charging stations will produce substantial harmonic pollution in the grid [2][3][4], which may result in some serious consequences (e.g., the increased losses and voltage fluctuations in the network, heating problems and efficiency losses of the electric equipment, the power supply interruptions, or even large scale blackouts) [3,5,6]. These efficiency losses of the power supply infrastructure will also affect the life cycle of alternative electric vehicles, which is important for the choice of the alternative technologies with different pathways [7,8].…”

Section: Introductionmentioning

confidence: 99%

Capacity Calculation of Shunt Active Power Filters for Electric Vehicle Charging Stations Based on Harmonic Parameter Estimation and Analytical Modeling

Zhou

Wang

et al. 2014

Abstract:The influence of electric vehicle charging stations on power grid harmonics is becoming increasingly significant as their presence continues to grow. This paper studies the operational principles of the charging current in the continuous and discontinuous modes for a three-phase uncontrolled rectification charger with a passive power factor correction link, which is affected by the charging power. A parameter estimation method is proposed for the equivalent circuit of the charger by using the measured characteristic AC (Alternating Current) voltage and current data combined with the charging circuit constraints in the conduction process, and this method is verified using an experimental platform. The sensitivity of the current harmonics to the changes in the parameters is analyzed. An analytical harmonic model of the charging station is created by separating the chargers into groups by type. Then, the harmonic current amplification caused by the shunt active power filter is researched, and the analytical formula for the overload factor is derived to further correct the capacity of the shunt active power filter. Finally, this method is validated through a field test of a charging station.