Selection Of Switching Frequency Research Articles

Improved Variable Switching Frequency Control for Capacitor Voltage Ripple Regulation in Multilevel Flying Capacitor Converter

For multi-level flying capacitor (FC) converter in dc-ac applications, variable switching frequency (VSF) control is an attractive solution to regulate the FC voltage ripple compared with the constant switching frequency (CSF) control. However, it is shown that the existing VSF control presents a higher switching loss in the three-phase operation when the identical switching frequency is applied to three phase-legs to reduce the complexity of VSF control implementation. To reduce the device switching losses in three-phase operation, this letter proposes a new strategy for the switching frequency selection, which allows each phase-leg to select its switching frequency individually. The control complexity of the proposed method is also reduced and is very similar to CSF control. The experiment result is also shown to verify the proposed variable switching frequency control strategy.

Electrothermal-Control Co-Design of an All Silicon Carbide 2×250 kW Dual Inverter for Heavy-Duty Traction Applications

This article presents the design and demonstration of an all silicon carbide (SiC) 2×250 kW dual inverter for heavy-duty traction applications. Through the use of a formal electrothermal-control co-design approach, the maximum power density of the proposed inverter system is 60 kW/L, which is accomplished by. More specifically, to analyze the thermal performance of the inverter, a lumped thermal model is developed based on the characteristics of the power modules and the cold plate. To analyze the complicated interaction between the power losses and module junction temperatures, a closed-loop iterative estimation scheme is proposed to estimate the inverter power loss and module junction temperature. Based on the proposed thermal model and estimation scheme, a detailed optimization procedure on the selection of switching frequency and dc-link capacitor is presented to maximize power density. Furthermore, design optimization of the busbar was conducted to minimize the stray inductance, thus reducing the voltage overshoot during switching transients. Comprehensive experimental studies were performed on a physical converter prototype built based on the optimization results, which validate both the effectiveness of the presented design approach.

Analysis, Design, and Comparison of V2V Chargers for Flexible Grid Integration

This study proposes a flexible, compact, efficient, and cost effective electric vehicle-to-electric vehicle charge sharing solution that will lead to faster and wider customer adoption of electric vehicles (EVs) as an alternative to current grid-to-vehicle charging methodologies. The energy will be transferred between EVs using a bidirectional dc-dc converter in a conductive way, which can take place at parking lots of workplaces, campuses, or residential premises and highways. The proposed design provides compact infrastructure, wide input and output voltage ranges with bidirectional buck-boost operation, and fast power transfer compared to Level 2 charging stations. A complete design comparison between Si and SiC based converters has been carried out based on the available power modules and magnetic cores. The comparison demonstrates the effect of switching frequency and switch selection on the size of passive components, the converter efficiency, and the power density of the converter. The developed study evaluated three different bidirectional dc-dc converter topologies and validated the developed prototype with experimental results.

Adaptive Switching Frequency Selection Based on Two-Step Efficiency Optimization for Grid-Connected Inverters

A two-step efficiency optimization of a three-phase voltage source inverter with series R damped LCL filter is proposed. The first optimization step aims to find the optimal parameters of the series R damped LCL filter at rated load conditions. The objective function of step-one is to minimize the values of the passive elements of the filter-stage. Afterward, the magnetic cores of inductors are thoroughly designed using soft magnetic powder materials. This design is proposed to specify the smallest core-size required based on the value of the inductance found in step-one of the optimization. The second optimization step aims to optimally select the switching frequency of the inverter-stage considering load variations. This optimization is based on the optimized filter-stage parameters. The proposed objective function of step-two aims to minimize the power losses in the inverter-stage and filter-stage while limiting the harmonic-levels at the point of common coupling. Detailed loss-formulation including filter-stage core and copper losses is thoroughly presented. Teaching-learning-based optimization algorithm is adopted to perform the optimization problem. Experiment and simulation are done to justify the proposed optimization procedure.

Inductor‐based auxiliary circuit‐assisted ZVS in full‐bridge dc–dc converter for EV applications

This study proposes an efficient soft-switched full-bridge DC/DC converter (FBDC) topology operated with modified pulse width modulation (MPWM) for electric vehicle (EV) battery chargers, as the role of DC/DC converter is more prominent in on-board charging. The proposed auxiliary circuit offers zero voltage switching (ZVS) turn-on to all the active switches of the converter during full battery charging range. In consequence, the losses associated with the proposed FBDC are minimal and offer maximum efficiency as compared to available benchmark topologies operated with different gating schemes. The size of magnetic elements used in the proposed topology also reduced as to conventional FBDC operating with trailing edge pulse width modulation and phase shifted modulation gating techniques. A detailed designing and analysis of the MPWM operated ZVS FBDC is presented. Besides, the rationale behind the selection of switching frequency in order to ensure wide-range ZVS is detailed. Further the proposed topology is compared with the other competent topologies for proving its significant merits. Simulation of the proposed configuration is performed at 3.3 kW. Following which, the experimental results obtained from a laboratory prototype of 500 W, 80 kHz validating the operability and feasibility of the proposed converter are presented.

Switching Frequency Selection Technique for Model Predictive Control based Multilevel Inverter

Switching Frequency Selection Technique for Model Predictive Control based Multilevel Inverter

Three-Step Switching Frequency Selection Criteria for Symmetrical CLLC-Type DC Transformer in Hybrid AC/DC Microgrid

In a hybrid ac/dc microgrid, the symmetrical CLLC-type dc transformer (CLLC-DCT) generally operates at the resonant frequency with the simple and low-cost semi-regulated open-loop scheme to ensure the power transmission (PT). However, more than one resonant frequency may exist, and they feature different characteristics for DCT. Meanwhile, the practical resonant frequencies are varying with temperature and power, which will degrade the PT ability if the switching frequency selection is not considered. Therefore, a switching frequency selection criteria (SFSC) approach is put forward for the symmetrical CLLC-DCT. For convenience, the active PT ratio (APTR) is employed as evaluation index of SFSC. First of all, the number and accurate values of resonant frequency are achieved in Step I. Then, in Step II, the optimal resonant frequency is determined as APTR-based criterion. In Step III, the parameter-variation-based criterion is presented to determine switching frequency. Finally, the experimental results verify that the semiregulated DCT based on the proposed approach not only improves efficiency, but also achieves the approximate PT ability with the relatively high-cost closed-loop controlled DCT.

Sensorless PMSM Drive Implementation by Introduction of Maximum Efficiency Characteristics in Reference Current Generation

This paper presents the efficiency improvement in a speed closed-loop controlled permanent magnet synchronous machine (PMSM) sensorless drive. The drive efficiency can be improved by minimizing the inverter and the PMSM losses. These can be influenced by proper selection of DC-bus voltage and switching frequency of the inverter. The direct (d-) and quadrature (q-) axis current references generation methods, discussed in this paper, further improve the efficiency of the drive. Besides zero d-axis current reference control, the maximum torque per ampere (MTPA) characteristic is normally applied to generate the d- and q-axis current references in vector controlled PMSM drives. It assures control with maximum torque per unit of current but cannot assure maximum efficiency. In order to improve efficiency of the PMSM drive, this paper proposes the generation of d- and q-axis current references based on maximum efficiency (ME) characteristic. In the case study, the MTPA and ME characteristics are theoretically evaluated and determined experimentally by measurements on discussed PMSM drive. The obtained characteristics are applied for the d- and q-axis current references generation in the speed closed-loop vector controlled PMSM drive. The measured drive efficiency clearly shows that the use of ME characteristic instead of MTPA characteristic or zero d-axis current in the current references generation improves the efficiency of PMSM drive realizations with position sensor and without it—sensorless control.

Three-Step Switching Frequency Selection Criteria for the Generalized CLLC-Type DC Transformer in Hybrid AC–DC Microgrid

For hybrid ac–dc microgrids, the widely applied high-frequency dc transformer (DCT) is usually scheduled to operate at resonant frequency with 50% duty-cycle-based semiregulated control to ensure the power transmission (PT), improve its power-density, and simplify the system-level control. However, for a real DCT, it may exist more than one resonant frequency that exhibit totally different features, which may seriously degrade the PT ability if the inappropriate switching frequency is selected. Meanwhile, the actual values of the DCT inductances and capacitances are also changing with the power, temperature, etc., which may lead to the practical resonant frequency's variation. Thus, how to select the suitable switching frequency to guarantee the PT ability against the parameter variation becomes a challenge. In this paper, three-step switching frequency selection criteria (SFSC) are proposed. A generalized CLLC -type DCT (GCLLC-DCT) model is extracted to make the proposed approach available for the LLC -, CLL -, symmetric CLLC -, and asymmetric CLLC -type topologies. For convenience, the definition of the active power transmission ratio (APTR) is introduced to help evaluate the PT ability. First, the number, value, and impact variables of the resonant frequency are derived and analyzed in Step I as the preliminary. Afterward, the optimum resonant frequency is confirmed for the GCLLC-DCT as the criterion based on the APTR in Step II. At last, the criterion in Step III is given to finally determine the switching frequency against the parameter variations. The proposed SFSC method is also validated by the experiments.

A Batteryless Energy Harvesting Storage System for Implantable Medical Devices Demonstrated In Situ

We report a wireless energy harvesting and telemetry storage system in 180 nm CMOS technology, demonstrated in situ in rat carcass. The implantable device has dimensions 13 mm × 15 mm and stores 87.5 mJ, providing a self-powering time of 8.5 s transmitting through tissue. We utilize an all-solid-state flexible supercapacitor of breakdown voltage 0.8 V and capacitance 400 mF to harvest incoming wireless power, followed by a boost converter CMOS that drives an active wireless transmitter at 1.5 V at 2.4 GHz in the industrial, scientific, and medical (ISM) band. The DC/DC converter component and switching frequency selection were guided by genetic algorithm analysis and use digital feedback to control the pulse width modulation (PWM), which slowly modifies the duty cycle to control output voltage fluctuations. This implantable medical device system presents the roadmap for batteryless energy harvesting in vivo and in clinical environments, exhibiting the highest operating storage density of 450 μJ/mm2 reported to date.

Online Optimal Switching Frequency Selection for Grid-Connected Voltage Source Inverters

Enhancing the performance of the voltage source inverters (VSIs) without changing the hardware structure has recently acquired an increased amount of interest. In this study, an optimization algorithm, enhancing the quality of the output power and the efficiency of three-phase grid connected VSIs is proposed. Towards that end, the proposed algorithm varies the switching frequency (fsw) to maintain the best balance between switching losses of the insulated-gate-bipolar-transistor (IGBT) power module as well as the output power quality under all loading conditions, including the ambient temperature effect. Since there is a contradiction with these two measures in relation to the switching frequency, the theory of multi-objective optimization is employed. The proposed algorithm is executed on the platform of Altera® DE2-115 field-programmable-gate-array (FPGA) in which the optimal value of the switching frequency is determined online without the need for heavy offline calculations and/or lookup tables. With adopting the proposed algorithm, there is an improvement in the VSI efficiency without degrading the output power quality. Therefore, the proposed algorithm enhances the lifetime of the IGBT power module because of reduced variations in the module’s junction temperature. An experimental prototype is built, and experimental tests are conducted for the verification of the viability of the proposed algorithm.

Efficiency Analysis of a Ladder Multilevel Converter with the Use of the Equivalent Continuous Model

This study analyzes a ladder multilevel converter (double ladder topology) with the use of a new averaging modeling technique. This technique introduces an analytical method to compute for the switching losses and is used to conduct an in-depth analysis of the influence of the switching frequency and parasitic resistance of components on converter efficiency. The obtained results enable the selection of switches and switching frequency to minimize losses. Moreover, simulation results and experimental measurements validate the analytical calculations.

An automatic load-adaptive switching frequency selection technique for improving the light-load efficiency of a buck converter

A load-adaptive automatic switching frequency selection scheme is proposed to improve the power efficiency of a switching buck converter at light load condition. The buck converter operates in the continuous-conduction mode for heavy loading and the switching frequency is fixed at its maximum value. For light loading, the buck converter operates in the discontinuous-conduction mode and its switching frequency is automatically selected among a pre-defined set of frequencies according to the amount of the load current. The load current can be sensed indirectly by monitoring the on-time of power transistor because it is a function of the load current. With the proposed load-adaptive automatic switching frequency selection circuit, the power efficiency of a buck converter implemented in a 0.35-μm 2P4M BCDMOS technology is improved by 24.0-% when the load current load is 10-mA.

CONTROL AND DESIGN ASPECTS OF POWER ELECTRONICS CONVERTERS USING PSPICE

In order to understand the functionality and design aspects of power converters, circuit simulation software PSpice has become an industry standard. In a Power Electronics course the students are required to understand the operating principles of a variety of static power converters using different control techniques to achieve the desired input-output characteristics.This paper presents PSpice-based design projects that can be used as pre-Lab exercises in a Laboratory course accompanying a lecture course in Power Electronics. The students can be made to implement their design in the laboratory with actual hardware components. The transition from design to simulation and finally to experimental verification will aid to strengthen their understanding of the operation, control, and design aspects of power converters. The design projects are geared towards bringing out the importance of power quality and cost issues that are relevant to state of the art circuit design.The design examples in the paper will start with a set of design guidelines and input-output requirements of a given power converter system. The design will involve selection of the proper control algorithm, switching frequency, and input-output filter values to meet the design goals. The following are the basic converter systems that will be covered in the various design projects: single phase and three phase rectifier, single phase and three phase inverters, buck and boost converter.