This paper reviews the current status and implementation of battery chargers, charging power levels, and infrastructure for plug-in electric vehicles and hybrids. Charger systems are categorized into off-board and on-board types with unidirectional or bidirectional power flow. Unidirectional charging limits hardware requirements and simplifies interconnection issues. Bidirectional charging supports battery energy injection back to the grid. Typical on-board chargers restrict power because of weight, space, and cost constraints. They can be integrated with the electric drive to avoid these problems. The availability of charging infrastructure reduces on-board energy storage requirements and costs. On-board charger systems can be conductive or inductive. An off-board charger can be designed for high charging rates and is less constrained by size and weight. Level 1 (convenience), Level 2 (primary), and Level 3 (fast) power levels are discussed. Future aspects such as roadbed charging are presented. Various power level chargers and infrastructure configurations are presented, compared, and evaluated based on amount of power, charging time and location, cost, equipment, and other factors.

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Review of Battery Charger Topologies, Charging Power Levels, and Infrastructure for Plug-In Electric and Hybrid Vehicles

An improved circulating current control method by applying a digital plug-in repetitive controller is discussed for harmonic elimination of a carrier-phase-shift pulse-width-modulation (CPS-PWM)-based modular multilevel converter (MMC) in this paper. The performance of the controller is analyzed in detail based on an improved circulating current control model with the consideration of the submodule voltage disturbance. It is shown that the proposed control method has the merits of simplicity, versatility, and better performance of circulating harmonic current elimination than the traditional proportional integral controller. The stability analysis of the proposed method are also discussed in the paper as well as the design principles. Finally, the experimental results including the steady-state performance and the transient response are given, which validates the feasibility and excellent performance of the proposed control scheme.

Circulating Harmonic Current Elimination of a CPS-PWM-Based Modular Multilevel Converter With a Plug-In Repetitive Controller

The voltage gain of traditional boost converter is limited due to the high current ripple, high voltage stress across active switch and diode, and low efficiency associated with large duty ratio operation. High voltage gain is required in applications, such as the renewable energy power systems with low input voltage. A high step-up voltage gain active-network converter with switched-capacitor technique is proposed in this paper. The proposed converter can achieve high voltage gain without extremely high duty ratio. In addition, the voltage stress of the active switches and output diodes is low. Therefore, low voltage components can be adopted to reduce the conduction loss and cost. The operating principle and steady-state analysis are discussed in detail. A prototype with 20-40-V input voltage, 200-V output voltage, and 200-W output power has been established in the laboratory. Experimental results are given to verify the analysis and advantages of the proposed converter.

A Switched-Capacitor-Based Active-Network Converter With High Voltage Gain

In this paper, a multilevel voltage-source converter system is proposed for high-voltage, high-power applications such as back-to-back interconnection of power systems, large induction motor drives, and electrical traction drives. Multilevel voltage-source converters have a voltage unbalance problem in the DC capacitors. The problem may be solved by use of additional voltage regulators or separate DC sources. However, these solutions are found not to be practicable for most applications. The proposed converter system can solve the voltage unbalance problem of the conventional multilevel voltage-source converters, without using any additional voltage balance circuits or separate voltage sources. The mechanism of the voltage unbalance problem is analyzed theoretically in this paper. The voltage unbalance problem of multilevel converters in the DC capacitors has been solved by the proposed internal connections of the AC/DC and DC/AC converters. The validity of the new converter system is demonstrated by simulation and experiment. >

A multilevel voltage-source converter system with balanced DC voltages

In this paper, a space vector pulsewidth modulation (PWM) (SVPWM) algorithm is proposed, which is in α'β' frame with dc-link capacitor voltage equalization for diode-clamped multilevel converters (DCMCs). The α'β' frame is a coordinate system similar to the αβ frame. In this frame, some original complex calculations are substituted by integer additions, integer subtractions, truncations, etc. It brings the time and area efficiency to fixed-point digital realization, particularly for the application in a field-programmable gate array. Meanwhile, a minimum energy property of multiple dc-link capacitors is applied as the basic principle for voltage equalization based on a capacitor current prediction algorithm. By evaluating the redundant vectors in each pulse dwelling period, the balancing algorithm chooses an optimal vector, generates the optimal PWM signals, and sustains the voltage stability. After that, an arbitrary multilevel SVPWM intellectual property core is designed and analyzed in the α'β' frame. At the end of this paper, a five-level DCMC-based static synchronous compensator is built and tested. The experimental results verify the balancing algorithm and the system steady-state and dynamic performances.

Multilevel SVPWM With DC-Link Capacitor Voltage Balancing Control for Diode-Clamped Multilevel Converter Based STATCOM

The novel multilevel circuit topologies are proposed in this paper. They are called multilevel circuit topologies based on switched-capacitor and diode-clamped converters (MCT-BSD). The topology structure and the operation principle, including the working states' transitions of the diode-clamped part, the voltages balancing mechanism of the dc link capacitors, and the pulse width modulated carrier control strategy are given. The switched-capacitor circuits contribute not only to balancing the voltages of capacitors but also to boosting the output voltage with a certain input dc voltage. The validity of the MCT-BSD is verified by simulations and experiments. The results show that balancing the voltages of capacitors, boosting the output voltages, and operating under the three-phase condition are all realized effectively in the MCT-BSD. The simulations also show the generalization of the MCT-BSD for n-level topologies.

Multilevel Circuit Topologies Based on the Switched-Capacitor Converter and Diode-Clamped Converter

An improved pulse width modulation (PWM) control method for three-phase hybrid-clamped multilevel inverters (HCMLI) is proposed in this paper. It can significantly reduce the surge currents through the DC link capacitors by changing the relative phase of the three-phase PWM carriers. The surge currents increase the capacitor losses and decrease the capacitor life, thus increasing the cost and reducing the reliability of inverters. The operating principle of the hybrid-clamped multilevel inverter, the generation mechanism of the surge currents, and the principle of the improved PWM method are given. The simulated and experimental results show that compared with the general PWM method, the improved PWM method can effectively reduce the voltage ripples on the DC link capacitors, consequently decreasing the surge currents through them.

An improved PWM control method to reduce surge current through capacitors in hybrid-clamped multilevel inverter

A three-phase PWM AC-DC converter with high power factor (PF) using hybrid-clamped five-level topology is researched in this paper. The mathematical model and control strategy are analyzed. In addition, a novel method to determine ac-side inductance according to required current ripple is proposed. Simulation and experimental results show the dc-link capacitor voltages imbalance extensively existing in multilevel converters can be solved, and the power factor correction is realized on the grid side.

http://ieeexplore.ieee.org/iel5/6014782/6020091/06020310.pdf

Cheng Tan

Papers

Multilevel Circuit Topologies Based on the Switched-Capacitor Converter and Diode-Clamped Converter

An improved PWM control method to reduce surge current through capacitors in hybrid-clamped multilevel inverter

Research on three-phase PWM hybrid-clamped five-level AC-DC converter with high power factor