Mehrdad Biglarbegian

Development of current measurement techniques for high frequency power converters

Current sensing plays dominant role in power converters, where current information can be used for controlling, monitoring and protection. One of the most challenging goals in modern power electronics converters is to increase switching frequency for the purpose of miniaturization, and improve the performance especially for end-users. Therefore, the need for accurate, lossless, and fast response current sensors is more highlighted. This paper presents a comprehensive review of different current sensing schemes for power electronics applications. The Challenges for implementation of conventional methods for high frequency (>1MHz) and high current converters will be addressed. More specifically, technical issue and hardware difficulties for developing Rogowski-based as well as Hall effect current sensors are discussed and finally, a new technique for improving the performance of Anisotropic Magneto-Resistive (AMR) at 1MHz and 30V with a new technique is shown.

Layout study of contactless magnetoresistor current sensor for high frequency converters

In this paper, we present a new technique to unify and intensify the magnetic fields that results in higher performance of Anisotropic Magneto-Resistive (AMR) current sensors and consequently develop a closed loop controller for 100W synchronous GaN buck converter at 1MHz. The closed loop operation of high switching frequency converters at high power has always been a big challenge due to lack of access to current information. The proposed method that also intensifies the magnetic fields through the sensor, significantly improves the bandwidth limits, and reduces electromagnetic interference (EMI) on AMR sensors, making them applicable for high switching frequency and high current power electronics converters. After verifying uniform distribution concept through simulation, we also implemented a prototype of AMR current sensors onto Printed Circuit Board (PCB) for verification of the concept at high frequency converter. We then present the design procedure and associated challenges of an integrated analogue peak current controller for creating the closed loop operation of a GaN buck converter at high switching frequency.

Design and evaluation of high current PCB embedded inductor for high frequency inverters

This paper describes the design and evaluation of high current toroidal Printed Circuit Board (PCB) embedded inductor applicable for high frequency DC/AC converters (lower than 10MHz). The equivalent circuit model of the inductor is presented and the filtering effectiveness is verified by testing three different geometries with its own characteristics and function through a GaN converter. Besides, the temperature rise analysis is provided for all the prototypes by using finite element methods, and the obtained results are also verified by experiments. The reason behind asymmetric trend of temperature rise for the toroidal PCB embedded inductor is also discussed through both simulation and experiment, and the capability of using a heat sink to lower the temperature increment for different geometries is explained.

Controller robustness analysis of grid-tied AC-stacked PV inverter system considering manufacturing inaccuracies

This paper analyzes the impact of current sensing inaccuracies due to aging and ambient condition variations on robust operation of PV inverter systems. A novel index for analyzing the robustness of grid-tied AC-stacked PV inverter architectures has been used, which provides an opportunity for comprehensive robustness evaluation by considering four major operational characteristics of grid-tied PV inverters as efficiency, Total Harmonic Distortion (THD), Power Factor (PF) compliance, and Maximum Power Point Tracking (MPPT) effectiveness. In addition, a comparative analysis between a single inverter and an AC-stacked inverter configuration is provided to study the impact of AC-stacking on robust operation of grid-tied PV inverters. This paper also proposes a possible state estimation solution for improving the robustness of the system using Kalman filter approach.

Performance study of magnetic field concentration techniques on magnetoresistor/rogowski contactless current sensor

Magnetoresistor/Rogowski coil can be utilized as a wideband contactless current sensor in power electronic converters. However, the magnetic Field detected by these sensing devices varies with frequency due to skin effect. This paper presents an investigation on two Magnetic field Concentration (MCON) techniques using conductive plates and power trace. These MCONs result in a more uniform magnetic Field seen by the sensing elements over the frequency range of interest. Simulation and experimental results are presented to demonstrate the efficacy of the proposed MCONs and their impacts on performance of the sensors.

Thermal storage capacity to enhance network flexibility in Dual Demand Side Management

The global concern for the environment and greater increase in the demand for electricity justifies integration of electrical and thermal units in the future smart grids to improve the system efficiency and reduce costs and emissions. In the distribution networks, micro-Combined Heat and Power unit equipped with a thermal storage system is an excellent candidate to meet the electrical and thermal demands. The aim of this paper is to present agent-based optimal control methodology to obtain higher flexibility for supplier to match the generations and demands. The market-based stochastic model for reducing the overall cost of generation and increasing the financial gain as long as supplying sufficient power to consumers in distribution level is described. The proposed algorithm is able to reach the optimum cost dispatching values according to different user behaviors and statistical data for switching micro-Combined Heat and Power units which are equipped with a thermal storage.

Boundary Conduction Mode Control of a Boost Converter With Active Switch Current-Mirroring Sensing

This letter presents a control scheme to operate a boost converter in boundary conduction mode (BCM). In the proposed method, it is assumed that the zero-current information is not available for controlling the converter operation mode. Therefore, a cursor is identified to detect the converter operation mode, i.e., continuous conduction mode/BCM. Details of the cursor and associated control method will be discussed in this letter. We demonstrate experimentally the effectiveness of the proposed method on a GaN boost converter whose active switch current is monitored through a current-mirroring technique.

Characterization of SenseGaN current-mirroring for power GaN with the virtual grounding in a boost converter

This paper presents an implementation of the SenseGaN current sensing technique using Gallium Nitride (GaN) transistors as a representative of Wide Bandgap (WBG) semiconductors. For effective feedback control, fast over-current protection, and diagnostics-prognostics developments, precise current measurement becomes more important. While the integration and miniaturization of power semiconductors are getting more feasible to operate at higher current as well as switching frequency, most of the available current measurement techniques have some technical challenges such as bandwidth limitations, higher power dissipation, and sensitivity variations. SenseGaN technique along with the integration of semiconductors to monitor the power module current without significant effects on power stage performance and opens a new era for smart devices in future power electronics; however, in practice, implementation of this method has some difficulties that should be addressed during the design process. This paper presents of SenseGaN in WBG-based power converters with Spice simulations and mathematical analysis. Finally, a prototype using power 650V-GaN is successfully tested at 150kHz, and verifies the consistency with the proposed model.

On self-healing of grid-tied PV inverters considering current sensor inaccuracy and aging degradation

Coming with the reliability enhancement and the life extension for the Photovoltaic (PV) inverters modules, diagnostic techniques will be required to derive signature identification. The reliable operation of PV inverter is very crucial to get the highest performance for the long term. A new Smart Inverter Robustness Index (SIRI) is used for verifying the performance and robustness of the grid-tied PV inverter. The index considers the major operational PV characteristics as efficiency, Total Harmonic Distortion (THD), Power Factor (PF) compliance, and Maximum Power Point Tracking (MPPT) effectiveness. The focus of this paper is to examine the impact of sensing inaccuracy and aging degradation over the long term and possible variations on the PV robustness. Since the initial simulation results show the significant reduction of system robustness, a state estimator was applied to modify the current sensor inaccuracy caused by the aging. During severe operation conditions, based on this local state estimation solution, an inverter can execute a corrective action to perform possible self-healing and increase its robustness.