Amin Hasanzadeh

A Proportional-Resonant Controller-Based Wireless Control Strategy With a Reduced Number of Sensors for Parallel-Operated UPSs

In this paper, a novel droop method to control the power sharing of parallel uninterruptible-power-supply (UPS) systems is presented. In a clear-cut contrast to the previously reported works, the controller is a proportional-resonant controller which ensures good transient response and steady-state objectives. Furthermore, the need for sensing the output current for the power-sharing control is removed by implementing it in a software routine. This brings a less complicated and less expensive structure in which the number of feedback sensors is reduced from three to two. The droop paralleling strategy is based on the drop in the inverter output frequency and amplitude. The application of proportional-resonant controllers based on internal model principle is also extended to parallel inverters, and its superior performance over the well-known proportional-integral-derivative controller is presented. In order to show the performance of the proposed system, two parallel-connected UPS systems are analyzed, and two types of linear and nonlinear loads are considered. The nonlinear load is compliant with IEC 62040-3 standard for class I UPS. The results show that the reduction of sensors does not result in any error, and the performance of the control system is excellent. To verify the proposed concept, the proposed strategy is implemented within two-625VA UPS systems. Several test results are provided for linear and nonlinear loads which validate the simulations results. The results indicate that the proposed parallel inverter structure offers a better system in terms of the number of feedback sensors, performance, and complication.

Real-Time Emulation of a High-Speed Microturbine Permanent-Magnet Synchronous Generator Using Multiplatform Hardware-in-the-Loop Realization

This paper demonstrates a multiplatform hardware-in-the-loop (HIL) approach to observe the operation of a high-speed permanent-magnet synchronous generator coupled with a microturbine in an all-electric-ship power system. The mathematical model of the gas turbine and the dynamic equations of the high-speed generator are implemented in real time on a field-programmable gate array (FPGA). This real-time simulation interfaces with hardware via a serial peripheral interface to a supervisory digital signal processor (DSP) of a three-phase voltage source inverter. The inverter output load is virtually emulated in the FPGA using received hardware measurements from the DSP. A user input interface is introduced using dSPACE on a personal computer to acquire data and adjust the speed reference of the generator system through a serial communication interface to the DSP. The real-time simulation and HIL experimental setup are validated in a scaled medium voltage dc ship power system.

Comparative Analysis of Bidirectional Three-Level DC–DC Converter for Automotive Applications

In battery/ultracapacitor electric vehicles, a bidirectional dc/dc converter is employed to process the power according to the power references obtained from the energy management controller. The selection of this converter is of critical importance for the overall system efficiency and size. This study proposes using a three-level dc/dc converter and provides a comprehensive comparison with the conventional two-level and interleaved bidirectional buck/boost converters in terms of magnetic component size/weight and overall efficiency. Unlike the comparative studies presented in the literature, where the efficiency comparison of converters is conducted based on given fixed input and output parameters, power references obtained from a wavelet-transform-based energy management strategy with varying energy source voltages and traction power are considered in this paper. The results of the analyses show that a three-level converter exhibits higher overall efficiency and has smaller size inductor. A 1-kW bidirectional three-level dc/dc converter is designed as a proof of concept, which exhibits 93.2% peak efficiency at 200-kHz switching frequency.

A Zero-Voltage-Transition Bidirectional DC/DC Converter

A three-level (TL) bidirectional dc/dc converter is a suitable choice for power electronic systems with a high-voltage dc link, as the voltage stress on the switches is half and inductor current ripple frequency is twice the converters switching frequency. This study proposes a zero-voltage transition (ZVT) TL dc/dc converter to enable operation with higher switching frequency in order to achieve higher power density and enhance efficiency. Two identical ZVT cells, each one composed of two resonant inductors, a capacitor, and an auxiliary switch, are integrated with the conventional TL topology to enable soft switching in all four switches in both buck and boost operation modes. In addition, a variable dead-time control is proposed to increase the effective duty ratio at heavy loads. The proposed soft-switching feature has been demonstrated under different loading conditions. A 650-W prototype is designed and fabricated, which exhibits 95.5% at full load.

Reduced switch NPC-based transformerless PV inverter by developed switching pattern

The neutral point clamped (NPC) topology and its derived topologies are getting more and more widespread in the application of transformerless photovoltaic (PV) inverters as the key elements for integration of power conversion in order to improve efficiency, practicality and reliability of PV systems. The regular, active and Conergy topologies have been proven that they are very suitable due to high efficiency, low leakage current and electromagnetic interference (EMI). This paper discusses a one-switch-reduced NPC-based structure compared with Conergy NPC topology with potential for reduced cost and increased efficiency. In addition, an elegant switching function is presented and implemented here with decreased complexity, with respect to the Conergy topology, via a bidirectional switch (BDS) logic that is independent of the grid current direction. The theoretical discussion, real-time data and experimental results are provided to validate performance of the proposed converter.

Optimal power split and sizing of hybrid energy storage system for electric vehicles

This paper targets the interdependence between sizing and power split optimization of hybrid energy storage systems (HESS) in electric vehicles (EV). In particular, a high energy (HE) density battery and an ultracapacitor (UC) hybrid system is investigated as a benchmark. A convex optimization problem is formulated to optimize the power split between battery and UC offline. Based on the power split optimization result, a HESS sizing optimization problem is developed to minimize the HESS weight and to fulfill the EV specifications of driving range and acceleration time.

Transportation Electrification: Conductive charging of electrified vehicles.

The U.S. transportation sector consumes approximately 14 million barrels of petroleum every day, which is more than the total oil consumption of any other nation in the world. The most prominent sustainable solution to profoundly reduce both oil consumption and greenhouse gas emissions lies in grid-enabled electric vehicles (EVs) These vehicles are propelled either partially or fully by electricity through energy storage systems such as electrochemical batteries, which need to be charged from the grid.

Application of power hardware-in-the-loop for electric vehicles: A case study utilizing switched reluctance machines

This paper presents the application of switched reluctance machines in a power hardware-in-the-loop (PHIL) environment. The switched reluctance machine (SRM) is the subject of PHIL experiments that observe operation of the SRM in a simulated electric vehicle (EV) system. The PHIL setup is used to control the DC-Bus voltage of the SRM and to simulate a driving profile by applying a dynamic load to the SRM. The uniqueness and practicality of using switched reluctance machines in a PHIL environment is emphasized. Preliminary experimental data is presented to reinforce the operability of the PHIL-SRM.

Loss analysis of non-isolated bidirectional DC/DC converters for hybrid energy storage system in EVs

The selection of a bidirectional non-isolated dc-dc converter interfacing the battery and ultracapacitor (UC) in electric vehicles (EVs) is of critical importance for the overall system efficiency. Generally, efficiency comparison of converters is conducted based on given fixed input and output parameters. Such a comparison may not provide fair results for EV applications since energy source voltages and traction power vary dynamically depending on the driving conditions. This paper provides a comprehensive efficiency comparison of three-level, two-level and interleaved bidirectional buck/boost converters through developed loss models considering the dynamic variables in a drive cycle. The results of the analyses show that three-level converter exhibits higher overall efficiency. A 1kW prototype has been designed and developed to serve as a proof of concept.

Comprehensive study of power quality criteria generated by PV converters and their impacts on distribution transformers

This paper investigates the impact of power quality criteria required by photovoltaic (PV) converters on legacy system transformers and its design procedure, since it is often argued that the use of traditional design for transformers in the PV integrated power systems is acceptable. The criteria studied in this paper are voltage amplitude variation (flicker), harmonics, frequency variation, power factor (PF) variation, DC bias, thermal cycling (loading), transients, inrush current, eddy current, and stray loss. Some of these problems will be simulated with a Voltage Source Inverter (VSI) and Current Source Inverter (CSI) which are frequently used in PV integrated power systems as Distributer Generation (DG) by decentralized controlled PV inverters. In this type of power system configuration, transformers may be utilized for isolation and/or filtering or as a part of the feeder facility. On the other hand, if the transformerless PV inverters are used in PV systems, then only the distribution transformers will be affected by the PV converters power quality problems. These issues can reveal or change the allowable penetration level at a specific bus location along the feeder. Furthermore, output voltage of VSI and output current of CSI of PV systems have a faster dynamic response and more distorted output than legacy power system voltage and current outputs. This means that the VSI and CSI need stiff controllers to ensure a suitable power exchange to the utility network, particularly to sensitive equipment like transformers that are designed for legacy unidirectional power transformations with a cleaner voltage and current than that provided by PV inverter based systems.