Chris Mi

Eliminate Reactive Power and Increase System Efficiency of Isolated Bidirectional Dual-Active-Bridge DC–DC Converters Using Novel Dual-Phase-Shift Control

This paper proposes a novel dual-phase-shift (DPS) control strategy for a dual-active-bridge isolated bidirectional DC-DC converter. The proposed DPS control consists of a phase shift between the primary and secondary voltages of the isolation transformer, and a phase shift between the gate signals of the diagonal switches of each H-bridge. Simulation on a 600-V/5-kW prototype shows that the DPS control has excellent dynamic and static performance compared to the traditional phase-shift control (single phase shift). In this paper, the concept of ldquoreactive powerrdquo is defined, and the corresponding equations are derived for isolated bidirectional DC-DC converters. It is shown that the reactive power in traditional phase-shift control is inherent, and is the main factor contributing to large peak current and large system loss. The DPS control can eliminate reactive power in isolated bidirectional DC-DC converters. In addition, the DPS control can decrease the peak inrush current and steady-state current, improve system efficiency, increase system power capability (by 33%), and minimize the output capacitance as compared to the traditional phase-shift control. The soft-switching range and the influence of short-time-scale factors, such as deadband and system-level safe operation area, are also discussed in detail. Under certain operation conditions, deadband compensation can be implemented easily in the DPS control without a current sensor.

Modeling and Simulation of Electric and Hybrid Vehicles

This paper discusses the need for modeling and simulation of electric and hybrid vehicles. Different modeling methods such as physics-based Resistive Companion Form technique and Bond Graph method are presented with powertrain component and system modeling examples. The modeling and simulation capabilities of existing tools such as Powertrain System Analysis Toolkit (PSAT), ADvanced VehIcle SimulatOR (ADVISOR), PSIM, and Virtual Test Bed are demonstrated through application examples. Since power electronics is indispensable in hybrid vehicles, the issue of numerical oscillations in dynamic simulations involving power electronics is briefly addressed

Quantitative Comparison of Flux-Switching Permanent-Magnet Motors With Interior Permanent Magnet Motor for EV, HEV, and PHEV Applications

Permanent-magnet (PM) motors with both magnets and armature windings on the stator (stator PM motors) have attracted considerable attention due to their simple structure, robust configuration, high power density, easy heat dissipation, and suitability for high-speed operations. However, current PM motors in industrial, residential, and automotive applications are still dominated by interior permanent-magnet motors (IPM) because the claimed advantages of stator PM motors have not been fully investigated and validated. Hence, this paper will perform a comparative study between a stator-PM motor, namely, a flux switching PM motor (FSPM), and an IPM which has been used in the 2004 Prius hybrid electric vehicle (HEV). For a fair comparison, the two motors are designed at the same phase current, current density, and dimensions including the stator outer diameter and stack length. First, the Prius-IPM is investigated by means of finite-element method (FEM). The FEM results are then verified by experimental results to confirm the validity of the methods used in this study. Second, the FSPM design is optimized and investigated based on the same method used for the Prius-IPM. Third, the electromagnetic performance and the material mass of the two motors are compared. It is concluded that FSPM has more sinusoidal back-EMF hence is more suitable for BLAC control. It also offers the advantage of smaller torque ripple and better mechanical integrity for safer and smoother operations. But the FSPM has disadvantages such as low magnet utilization ratio and high cost. It may not be able to compete with IPM in automotive and other applications where cost constraints are tight.

Three-Level Inverter-Based Shunt Active Power Filter in Three-Phase Three-Wire and Four-Wire Systems

This paper presents a direct current-space-vector control of an active power filter (APF) based on a three-level neutral-point-clamped (NPC) voltage-source inverter. The proposed method indirectly generates the compensation current reference by using an equivalent conductance of the fundamental component using APFs dc-link voltage control. The proposed control can selectively choose harmonic current components by real-time fast Fourier transform to generate the compensation current. The compensation current is represented in a rotating coordinate system with chosen switching states from a switching table implemented in a field-programmable gate array. In addition, a three-phase four-wire APF based on a three-level neutral-point-clamped inverter is also presented. The proposed APF eliminates harmonics in all three phases as well as the neutral current. A three-phase three-wire NPC inverter system can be used as a three-phase four-wire system since the split dc capacitors provide a neutral connection. To regulate and balance the split dc-capacitor voltages, a new control method using a sign cubical hysteresis controller is proposed. The characteristics of the APF system with an LCL-ripple filter are investigated and compared with traditional current control strategies to evaluate the inherent advantages. The simulation and experimental results validated the feasibility of the proposed APF.

Experimental Comparison of Traditional Phase-Shift, Dual-Phase-Shift, and Model-Based Control of Isolated Bidirectional DC–DC Converters

Three different control algorithms, traditional single-phase-shift control, dual-phase-shift control (DPSC), and model-based phase-shift control (MPSC), are implemented in a hardware setup and compared for a full-bridge-based isolated bidirectional dc-dc converter. The differences among their dynamic performance and steady-state operations are quantitatively analyzed. Experimental results showed good agreement with theoretical analysis. MPSC showed the best dynamic performance, while DPSC can eliminate reactive power under light-load conditions.

Modeling of a Complementary and Modular Linear Flux-Switching Permanent Magnet Motor for Urban Rail Transit Applications

In this paper, a complementary and modular linear flux-switching permanent magnet (MLFSPM) motor is investigated, in which both the magnets and armature windings are placed in the short mover, while the long stator consists of iron core only. The proposed MLFSPM motor incorporates the high power density of a linear permanent magnet synchronous motor and the simple structure of a linear induction motor. It is especially suitable for long stator applications such as urban rail transit. The objective of this paper is to build the mathematical model for the purpose of control of this motor. The simulation results by means of finite-element analysis (FEA) verified the theoretical analysis and the effectiveness of this model. Both the analytical model and the FEA results are validated by experiments based on a prototype motor.

Modeling of Eddy-Current Loss of Electrical Machines and Transformers Operated by Pulsewidth-Modulated Inverters

Pulsewidth-modulated (PWM) inverters are used more and more to operate electrical machines and to interface renewable energy systems with the utility grid. However, there are abundant high-frequency harmonics in the output voltage of a PWM inverter, which increase the iron losses and result in derating of the machine or transformer connected to them. Predicting the iron losses caused by the PWM supply is critical for the design of electrical machines and transformers operated by PWM inverters. These losses are primarily attributed to eddy-current loss caused by the PWM supply. In this paper, after analyzing the harmonic components of PWM voltage, we derive the effects of different parameters of PWM switching on the eddy-current loss. We compare the iron losses modeled with the proposed analytical methods on a three-phase transformer, a dc motor, and an induction motor with the results of time-stepping finite-element analysis and experiments. We provide detailed equations for the prediction of iron losses. These equations can be directly applied in the design and control of PWM converters and electric motors to improve energy efficiency in electrical machines and transformers operated from PWM converters.

A Double-Sided LCLC -Compensated Capacitive Power Transfer System for Electric Vehicle Charging

A double-sided LCLC-compensated capacitive power transfer (CPT) system is proposed for the electric vehicle charging application. Two pairs of metal plates are utilized to form two coupling capacitors to transfer power wirelessly. The LCLC-compensated structure can dramatically reduce the voltage stress on the coupling capacitors and maintain unity power factor at both the input and output. A 2.4-kW CPT system is designed with four 610-mm × 610-mm copper plates and an air gap distance of 150 mm. The experimental prototype reaches a dc-dc efficiency of 90.8% at 2.4-kW output power. At 300-mm misalignment case, the output power drops to 2.1 kW with 90.7% efficiency. With a 300-mm air gap distance, the output power drops to 1.6 kW with 89.1% efficiency.

Charge-Depleting Control Strategies and Fuel Optimization of Blended-Mode Plug-In Hybrid Electric Vehicles

This paper investigates the fuel consumption minimization problem of a blended-mode plug-in hybrid electric vehicle (PHEV). A simplified mathematical model of the PHEV was constructed to obtain optimal solutions for depleting the battery to a given final state of charge (SOC) under constant vehicle speed. An optimal power strategy was constructed from theoretical analysis and simulation for constant speed cases and then applied to typical drive-cycle simulations for a middle-size plug-in sport utility vehicle in the Urban Dynamometer Driving Schedule, the U.S. Environmental Protection Agency US06 (Supplemental Federal Test Procedure), and the CR-City drive cycles. Simulation results indicate that the proposed control strategy is more efficient than other strategies of interest. Only the electric system loss characteristics, vehicle power demand, total battery energy, and trip distance are needed to implement the proposed control strategy in a PHEV. It does not rely on the detailed trip information other than the total trip distance. Therefore, it is possible to implement the control strategy in real time if the total trip distance is known before the trip.

Advanced Electro-Thermal Modeling of Lithium-Ion Battery System for Hybrid Electric Vehicle Applications

The successful implementation and commercialization of hybrid electric vehicles (HEV) rely largely on energy storage systems. Lithium-ion batteries offer potential advantages in energy density, power density, and cost for this purpose. One of the challenges imposed by lithium-ion battery is the thermal management. The best operating temperature of lithium-ion battery is from -10degC to 50degC. An effective thermal management system is critical to maintain the health and life span of the battery. A good thermal management system starts with accurate prediction of the thermal conditions of the battery. This paper is aimed to evaluate the thermal management system of a lithium-ion battery pack designed for HEV applications, including estimating the thermal loss of the battery pack based on electric characteristics and experiments; predicting the temperature rise of the battery pack based on the test results of a single cell, and modeling the temperature gradients of the battery pack under different operating conditions.