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Energy storage units (such as battery or ultracapacitor) can help to reduce the power fluctuation in the impedance source network converter applications such as the photovoltaic (PV) and fuel cells systems. Due to the unknown dynamic characteristics of the energy stored impedance network, the unexpected oscillation and inrush currents in dynamic process might threaten the storage device safety. In this article, an energy stored quasi-Z-source converter with the battery is modeled and analyzed including the transient capacitor current. The impact of the network internal resonance on the battery current control loop is mathematically explored. The resulted conflict between the zero steady-state error and bandwidth requirement is revealed. That yields the sacrifice and limitation of the closed-loop dynamic performance in the conventional methods. An active damping technique is then proposed to ensure the extended bandwidth and better dynamic performances under different state of charge (SOC) occasions. The theoretical analysis and performance are both verified by the simulations and experiments. [ABSTRACT FROM AUTHOR]

To improve the performance and integration of the power train of electric vehicles power, a dual three-phase permanent magnet synchronous machine (PMSM) drive is investigated to achieve hybrid energy storage system power management. Two sets of motor windings are connected with ultracapacitors and a battery, respectively, through the inverters. First, the operation modes of the integrated system are studied by modeling and vector diagram analysis. A new control scheme is then established to enhance the regulation for unbalanced winding power distribution. The approach to suppress the motor harmonics current under the unbalanced power operation is also discussed. Finally, a frequency dividing coordinated control is performed for good dynamic response and seamless transient process. Both simulation and experiment results verify the effectiveness of the proposed system and the control strategy. [ABSTRACT FROM PUBLISHER]

An ultracapacitor–battery hybrid energy storage system (HESS) for an electric vehicle (EV) based on a bidirectional quasi-Z-source inverter (qZSI) is proposed in this paper. The buck/boost characteristic in the qZSI enables the HESS incorporated into the traction inverter system. The battery converter can be eliminated and the rated voltages for the battery package and UCs are reduced. The steady power distribution principle is explained under various operation modes. An enhanced frequency dividing coordinated control strategy is established to optimize the dynamic power regulation and the battery current stress in short timescale. Both the simulation and experimental results in time and frequency domain validate the performance of the proposed HESS. [ABSTRACT FROM PUBLISHER]

This paper proposes an ultracapacitor (UC)-battery hybrid energy storage system (HESS) for electric vehicle based on asymmetric bidirectional Z-source topology. Compared with the conventional two-stage design, the HESS can be incorporated into the traction inverter system, leading to better performance and lower cost. The UC energy can be effectively utilized due to the buck/boost characteristic in the Z-source converter; meanwhile, the battery converter gets eliminated in this case. The assumption about the symmetry in the Z-source topology impendence network states for the conventional analysis no longer applies to the proposed HESS configuration. The asymmetric characteristic related with the uneven power distribution of UCs and battery is mathematically excavated in detail. The frequency dividing coordinated control is proposed to exploit the advantages of UCs and battery. The battery peak current estimation is then investigated. Finally, the steady performance and transient response in both traction and regenerative modes are verified by simulation and experimental results. [ABSTRACT FROM PUBLISHER]

In this paper, an inductor–inductor–capacitor (LLC) resonant dc–dc converter design procedure for an onboard lithium-ion battery charger of a plug-in hybrid electric vehicle (PHEV) is presented. Unlike traditional resistive load applications, the characteristic of a battery load is nonlinear and highly related to the charging profiles. Based on the features of an LLC converter and the characteristics of the charging profiles, the design considerations are studied thoroughly. The worst-case conditions for primary-side zero-voltage switching (ZVS) operation are analytically identified based on fundamental harmonic approximation when a constant maximum power (CMP) charging profile is implemented. Then, the worst-case operating point is used as the design targeted point to ensure soft-switching operation globally. To avoid the inaccuracy of fundamental harmonic approximation approach in the below-resonance region, the design constraints are derived based on a specific operation mode analysis. Finally, a step-by-step design methodology is proposed and validated through experiments on a prototype converting 400 V from the input to an output voltage range of 250–450 V at 3.3 kW with a peak efficiency of 98.2%. [ABSTRACT FROM PUBLISHER]