Mehdi Ferdowsi

Double-Tiered Switched-Capacitor Battery Charge Equalization Technique

The automobile industry is progressing toward hybrid, plug-in hybrid, and fully electric vehicles in their future car models. The energy storage unit is one of the most important blocks in the power train of future electric-drive vehicles. Batteries and/or ultracapacitors are the most prominent storage systems utilized so far. Hence, their reliability during the lifetime of the vehicle is of great importance. Charge equalization of series-connected batteries or ultracapacitors is essential due to the capacity imbalances stemming from manufacturing, ensuing driving environment, and operational usage. Double-tiered capacitive charge shuttling technique is introduced and applied to a battery system in order to balance the battery-cell voltages. Parameters in the system are varied, and their effects on the performance of the system are determined. Results are compared to a single-tiered approach. MATLAB simulation shows a substantial improvement in charge transport using the new topology. Experimental results verifying simulation are presented.

Aggregated Impact of Plug-in Hybrid Electric Vehicles on Electricity Demand Profile

Greenhouse gas emissions, air pollution in urban areas, and dependence on fossil fuels are among the challenges threatening the sustainable development of the transportation sector. Plug-in hybrid electric vehicle (PHEV) technology is one of the most promising solutions to tackle the situation. While PHEVs partially rely on electricity from the power grid, they raise concerns about their negative impacts on power generation, transmission, and distribution installations. On the other hand, they have the potential to be used as a distributed energy storage system for the grid. Therefore, they can pave the way for a more sustainable power grid in which renewable resources are widely employed. Positive and negative impacts of PHEVs on the power grid cannot be thoroughly examined unless extensive data on the utilization of each individual PHEV are available. For instance, in order to estimate the aggregated impact of PHEVs on the electricity demand profile, one needs to know 1) when each PHEV would begin its charging process, 2) how much electrical energy it would require, and 3) how much power would be needed. This paper extracts and analyzes the data that are available through national household travel surveys (NHTS). Three charging scenarios are considered in order to obtain various PHEV charging load profiles (PCLPs). Further, the characteristics of each developed PCLP are studied. Finally, the effects of three suggested policies on the derived PCLPs are examined.

Review of multiple input DC-DC converters for electric and hybrid vehicles

Batteries, ultra capacitors, fuel cells, and solar arrays are widely used in electric and hybrid vehicles (EVs/HVs) as an electric power source or an energy storage unit. In the structure of the electric power system of modern EVs/HVs, more than one of these units may be employed to improve the performance and efficiency; hence utilization of a multi-input DC-DC converter is inevitable to obtain a regulated bus DC voltage. In this paper, a review of multiple input DC-DC power electronic converters (MI-PEC) devoted to combine the power flow from several on-board energy sources of an EV/HV is presented. Several multi-input DC-DC converters based on various topologies are studied and analyzed. The operating modes of each topology is presented and compared with other topologies.

Fault Detection and Mitigation in Multilevel Converter STATCOMs

Many static synchronous compensators (STATCOMs) utilize multilevel converters due to the following: 1) lower harmonic injection into the power system; 2) decreased stress on the electronic components due to decreased voltages; and 3) lower switching losses. One disadvantage, however, is the increased likelihood of a switch failure due to the increased number of switches in a multilevel converter. A single switch failure, however, does not necessarily force an (2n + 1)-level STATCOM offline. Even with a reduced number of switches, a STATCOM can still provide a significant range of control by removing the module of the faulted switch and continuing with (2n - 1) levels. This paper introduces an approach to detect the existence of the faulted switch, identify which switch is faulty, and reconfigure the STATCOM. This approach is illustrated on an eleven-level STATCOM and the effect on the dynamic performance and the total harmonic distortion (THD) is analyzed.

Utilization and effect of plug-in hybrid electric vehicles in the United States power grid

Plug-in hybrid electric vehicles (PHEVs) are uniquely capable of providing both transportation and battery storage interconnection to the electric power grid. This ability allows PHEVs the possibility of serving the power grid in the capacity of a mobile energy storage unit, providing the grid with additional stability, reliability, cost-effectiveness, and efficiency. Additionally, with the higher fuel efficiency of PHEVs, the transportation and power generation sectors can collectively reduce their ecologically harmful emissions and increase their reliance on environmentally friendly energy sources. These concepts are still new and under development; in this paper, the viability of the PHEV as a mobile energy storage unit connected to the power grid is examined from a power system perspective, involving an examination of practicality, reliability, short- and long-term economics, and alternative energy storage units.

Double-Input DC–DC Power Electronic Converters for Electric-Drive Vehicles—Topology Exploration and Synthesis Using a Single-Pole Triple-Throw Switch

Hybridizing energy systems using storage devices has gained popularity in transportation and distributed electric power generation applications. Traditionally, several independent power electronic converters (PECs) were utilized in such practices. Due to their reduced part count, double-input (DI) PECs prove to be a promising choice in hybridizing energy systems. A few topologies for multi-input converters have been reported in the literature; however, there is no systematic approach to synthesize them. Furthermore, all possible topologies are not completely explored, and it is difficult to derive new converters from existing topologies. Therefore, in this paper, a systematic approach to derive DI converters by using a single-pole triple-throw switch as a building block is presented.

Single-phase bidirectional AC-DC converters for plug-in hybrid electric vehicle applications

Plug-in hybrid electric vehicles (PHEVs) are specialized hybrid electric vehicles that have the potential to obtain enough energy for average daily commuting from batteries. These batteries would be charged from the power grid and would thus allow for a reduction in the overall petroleum consumption. To implement the plug-in function, a single phase bidirectional AC-DC converter interfacing with the grid is essential. The implementation of a bidirectional AC-DC converter can allow for battery recharge from the grid, battery energy injection to the AC grid, and battery energy for AC power stabilization. In this paper, the basic requirements and specifications for PHEV bidirectional AC-DC converter designs are presented. Generally, there are two types of topologies used for PHEVs: an independent topology and a combination topology that utilizes the drive motorpsilas inverter. Evaluations of the two converter topologies are analyzed in detail. The combination topology analysis is emphasized because it has more advantages in PHEVs, in respect to savings in cost, volume and weight.

Pulse Train control technique for flyback converter

Pulse Train/spl trade/ control technique is introduced and applied to flyback converter operating in discontinuous conduction mode (DCM). In contrast to the conventional pulse width modulation (PWM) control scheme, the principal idea of Pulse Train is to achieve output voltage regulation using high and low power pulses. The proposed technique is applicable to any converter operating in DCM. However, this work mainly focuses on flyback topology. In this paper, the main mathematical concept of the new control algorithm is introduced and simulations as well as experimental results are presented.

New Double Input DC-DC Converters for Automotive Applications

The energy storage unit is one of the most important subsystems in the structure of hybrid electric vehicles since it directly impacts the performance, fuel economy, cost, and weight of the vehicle. New structures for the energy storage unit, which utilize both batteries and ultracapacitors, are widely under investigation. In order to fully utilize the advantages of each energy storage device, employment of multi-input power converters is inevitable. In this paper, two new double input converters are introduced. Their different operating modes are analyzed and their voltage transfer ratios are derived. Simulation results are used to verify the expected operational characteristics

Investigation on Capacitor Voltage Regulation in Cascaded H-Bridge Multilevel Converters With Fundamental Frequency Switching

Multilevel power electronic converters have gained popularity in high-power applications due to their lower switch voltage stress and modularity. Cascaded H-bridge converters are a promising breed of multilevel converters which generally require several separate dc voltage sources. By utilizing the redundant switching states, it is possible to replace the separate dc voltage sources with capacitors and keep only the one with the highest voltage level. Redundancy in the charge and discharge modes of the capacitors is assumed to be adequate for their voltage regulation. However, the effects of the output current of the converter as well as the time duration of the redundant switching states have been neglected. In this paper, the impacts of the connected load to the cascaded H-bridge converter as well as the switching angles on the voltage regulation of the capacitors are studied. This paper proves that voltage regulation is only attainable in a much limited operating conditions that it was originally reported. In addition, based on the analysis of the converter, a simplified formula is found which can be used to find those modulation indices that regulate the voltage of the capacitor. This formula can be used in harmonic minimization problems while capacitor voltage regulation is ensured. Simulation and laboratory results are provided to confirm the analysis.