Furkan Akar

A Bidirectional Nonisolated Multi-Input DC–DC Converter for Hybrid Energy Storage Systems in Electric Vehicles

To process the power in hybrid energy systems using a reduced part count, researchers have proposed several multiinput dc-dc power converter topologies to transfer power from different input voltage sources to the output. This paper proposes a novel bidirectional nonisolated multi-input converter (MIC) topology for hybrid systems to be used in electric vehicles composed of energy storage systems (ESSs) with different electrical characteristics. The proposed converter has the ability to control the power of ESSs by allowing active power sharing. The voltage levels of utilized ESSs can be higher or lower than the output voltage. The inductors of the converter are connected to a single switch; therefore, the converter requires only one extra active switch for each input, unlike its counterparts, hence resulting in reduced element count. The proposed MIC topology is compared with its counterparts concerning various parameters. It is analyzed in detail, and then, this analysis is validated by simulation and through a 1-kW prototype based on a battery/ultracapacitor hybrid ESS.

An Energy Management Strategy for a Concept Battery/Ultracapacitor Electric Vehicle With Improved Battery Life

Using multi-input converters (MICs) in hybrid energy storage systems (HESSs) presents several advantages, such as low component count, control simplicity, and fully control of source energies. The power levels of sources in these systems need to be determined wisely by an energy management strategy (EMS). This paper presents an EMS for a battery/ultracapacitor (UC) HESS including a bidirectional MIC for electric vehicles (EVs). Thanks to the fact that energy flow between battery and UC is free in this MIC, the proposed EMS not only regulates the state-of-charge of UC but also smooths the battery power profile by using a fuzzy logic controller and a rate limiter. Therefore, it results in a sustainable HESS with longer battery life. Through a simulation study and an experimental setup including a real EV, the performance of the proposed system is evaluated comprehensively. Then, based on experimental results, battery cycle-life improvement due to the battery/UC hybridization is explored.

Battery/UC hybridization for electric vehicles via a novel double input DC/DC power converter

In this work, for electric vehicles (EVs), a novel double input DC-DC power converter, that enables utilization of a battery and ultra-capacitor (UC) in parallel while increasing the overall performance of electric vehicles and recovering regenerative breaking energy, is introduced. Since UCs have higher power density when compared to batteries, by the use of a UC as a power input, DC bus voltage regulation at transients and peak loads is achieved easily, thus the life of the battery and efficiency of the system are increased. The average value model of the proposed converter is created in MATLAB®, Simulink® and SimPowerSystems® environment, then its dynamic performance is tested under the load determined from the ECE-15 drive cycle.

Current ripple minimization of a PEM fuel cell via an interleaved converter to prolong the stack life

This paper focuses on to prolong the Proton Exchange Membrane (PEM) fuel cell stack life via an interleaved double switch buck-boost converter. PEM fuel cells are environmental friendly energy sources, and widely used in several applications such as electrical vehicles, power plants, back-up power units, thanks to their fast start-up ability, portability, and efficient operation. In the steady-state, the fuel cell current ripple may result in damage to the fuel cell chemical structure, so it is required to extract its power via a power converter that can overcome this issue. Therefore, in this work, a power converter topology and a control method are proposed in order to reduce the converter input current ripple in both buck and boost operation modes with the help of its two input inductors. In addition to that, sharing input current via these inductors decreases input capacitance voltage stresses and average current flowing through the interleaved inductors thus smaller input capacitance and inductors also increase the cost effectiveness of proposed converter. The simulation results indicate that the proposed interleaved buck-boost topology reduces the input current ripple, and leads less settling time hence better dynamic response owing to its interleaved structure.

An optimal maximum torque per ampere strategy for switched reluctance machines

Addressing drawbacks inherent to switched reluctance machines (SRM) could allow its distinctive characteristics to broaden applications from selective, niche industrial roles to various engineering sectors. Phase winding isolation is a contributing factor of advantageous characteristics unique to SRMs when compared to the industry workhorse, pulse width modulation driven induction machines. Specifically, this increases fault tolerance, simplifies the manufacturing winding process, and allows the machine to remain in a locked rotor position safely without concern of faulting, thus contributing to a greater overall robustness. On the contrary SRMs, when compared to other electrical machine types, are most notably criticized for requiring complex control strategies to achieve optimal operation, having greater overall current requirements, operating at higher speeds, and creating greater acoustic noise and torque ripple. Cumulatively, these shortcomings alienate the SRMs commercial and industrial popularity, ultimately limiting its full potential from being exploited. Since SRM torque production is typically non-linear, various techniques have been developed in order to produce the maximum torque per given current excitation, i.e. maximum torque per ampere (MTA). The “balanced commutator” control strategy uses a look-up table to account for the non-linearity of the SRMs torque-angle characteristic, yet does not totally optimize the copper or iron losses, current requirements, or effectively mitigate the torque ripple. A stochastic search technique based on evolutionary algorithms, particle swarm optimization (PSO), allows for MTA profiles to be obtained that optimize the shortcomings inherent to the balanced commutator technique. This work presents a novel MTA SRM control strategy based on the PSO technique. The optimum phases current profiles of a 4-phase, 8/6 pole SRM are obtained such that copper losses and torque ripple are minimized while achieving the desired torque at specific rotor positions. Results are compared against the balanced commutator method.

A computationally intelligent maximum torque per ampere control strategy for switched reluctance machines

While currently occupying only a niche role in industrial applications, the switched reluctance machines (SRM) unique operational characteristics could prove useful for additional engineering sectors given that inherent drawbacks are addressed. Phase winding isolation of SRMs provides greater fault tolerance when compared to the industrial standard, pulse width modulation driven induction machines. Furthermore, they may remain in a locked rotor position safely without concern of faulting and have higher speeds than many other electrical machines, i.e. contributing to greater overall robustness. When compared to other electrical machines, the SRM has higher currents requirements, creates greater acoustic noise and torque ripple, and requires more advanced controls for effective operation. Such drawbacks alienate the SRMs commercial and industrial popularity, ultimately limiting its full potential from being exploited. Since SRM torque production is typically non-linear, various techniques have been developed in order to maximize the torque output per unit current excitation, i.e. maximum torque per ampere (MTA). The “conventional” strategy, while simplistic, assumes a constant excitation over a symmetric period of the machine. This increases copper and iron losses while not effectively mitigating the current requirements or inherent torque ripple. By using particle swarm optimization (PSO), a stochastic search technique based on evolutionary algorithms, phase current MTA profiles may be obtained that optimize such conditions. This work presents a novel MTA SRM control strategy based on the PSO technique that obtains the optimum phase current profiles of a 4-phase, 8/6 pole SRM such that copper losses and torque ripple are minimized while achieving the desired torque at specific rotor positions.

PV/battery hybrid energy system via a double input DC/DC converter for dynamic loads

In this work, the utilization of a Photovoltaic (PV) array and a battery pack in parallel via a double input DC/DC converter including a coupled inductor is reported. The dynamic performance of this proposed hybrid energy system is analyzed in detail through the switching model created in MATLAB^® Simulink^® environment by using PLECS^® power components under different solar irradiance and demanded load levels.

A high-efficiency bidirectional non-isolated multi-input converter

A high-efficiency bidirectional non-isolated converter with multiple input sources is presented in this work. In the proposed converter, the energy from/to the input sources is transferred via the coupled inductors connecting to a switch pair. This topology does not only allow active power sharing, but also results in reduced component count. It also achieves zero-voltage-switching without any extra switching losses hence improving the cost-effectiveness, power density and efficiency.