Maximum Effectiveness of Electrostatic Energy Harvesters When Coupled to Interface Circuits

Accepted versio

Active power losses distribution methods for the modular multilevel converter

Modular Converters such as the MMC have become the new standard in VSC-HVDC applications. Their modularity has brought many industrial advantages but also increased the complexity of their operation. This paper looks at how a range of techniques may alter the balance of power losses between the IGBT modules. These techniques are based on circulating currents at the (i) fundamental frequency and (ii) second harmonic and (iii) DC voltage offset on the converter voltage waveform. Finally, conclusions on the effectiveness and potential drawbacks of these techniques are discussed

Design and Development of a Class EF2 Inverter and Rectifier for Multi-megahertz Wireless Power Transfer Systems

This paper presents the design and implementation of a Class EF2 inverter and Class EF2 rectifier for two -W wireless power transfer (WPT) systems, one operating at 6.78 MHz and the other at 27.12 MHz. It will be shown that the Class EF2 circuits can be designed to have beneficial features for WPT applications such as reduced second-harmonic component and lower total harmonic distortion, higher power-output capability, reduction in magnetic core requirements and operation at higher frequencies in rectification compared to other circuit topologies. A model will first be presented to analyze the circuits and to derive values of its components to achieve optimum switching operation. Additional analysis regarding harmonic content, magnetic core requirements and open-circuit protection will also be performed. The design and implementation process of the two Class-EF2-based WPT systems will be discussed and compared to an equivalent Class-E-based WPT system. Experimental results will be provided to confirm validity of the analysis. A dc-dc efficiency of 75% was achieved with Class-EF2-based systems

Power Management Electronics

Accepted versio

Implementation of a Single Supply Pre-biasing Circuit for Piezoelectric Energy Harvesters

AbstractIncreased output power can be obtained from piezoelectric energy harvesters by using switching circuits that modify the charge on the material at the extremes of cantilever travel. Here we present an implementation of the most efficient of these charge modification techniques, single-supply piezoelectric pre-biasing. We describe practical results from this scheme and circuit details, including power processing components and control circuits. The power circuit current paths are synchronously commutated with MOSFETs, removing inefficient diode voltage drops. The control circuit is implemented using low power discretes. A useful output power of 2.6 mW was achieved after a 400μW reduction required for the control circuitry. This is a factor of 4.3 greater than when the harvester was connected to a passive diode bridge and is greater than can be achieved by other piezoelectric interface circuits using an inductor with the same Q-factor

Power loss and thermal characterization of IGBT modules in the Alternate Arm converter

Power losses in high power HVDC converters are dominated by those that occur within the power electronic devices. This power loss is dissipated as heat at the junction of semiconductor devices. The cooling system ensures that the generated heat is evacuated outside the converter station but temperature management remains critical for the lifetime of the semiconductor devices. This paper presents the results of a study on the temperature profile of the different switches inside a multilevel converter. The steady state junction temperatures are observed through the simulation of a 20 MW Alternate Arm Converter using 1.2kA 3.3 kV IGBT modules. A comparison of the Alternate Arm Converter is made against the case of both the half-bridge and full-bridge Modular Multilevel Converter topologies. Furthermore, the concept of varying the duty-cycle of the two alternative zero-voltage states of the H-bridge modules is introduced. Simulation results demonstrate that it can change the balance of electrical and thermal stress between the two top switches and the two bottom switches of a full-bridge cell. © 2013 IEEE

Control models of Switch Mode Maximum Power Point Tracking Interfaces for Energy Harvesting Devices

Published versio

Load-independent Class EF inverters for inductive wireless power transfer

This paper will present the modelling, analysis and design of a load-independent Class EF inverter. This inverter is able to maintain zero-voltage switching (ZVS) operation and produce a constant output current for any load value without the need for tuning or replacement of components. The load-independent feature of this inverter is beneficial when used as the primary coil driver in multi megahertz high power inductive wireless power transfer (WPT) applications where the distance between the coils and the load are variable. The work here begins with the traditional load-dependent Class EF topology for inversion and then specifies the criteria that are required to be met in order achieve load-independence. The design and development of a 240W load-independent Class EF inverter to drive the primary coil of a 6.78MHz WPT system will be discussed and experimental results will be presented to show the load-independence feature when the distance between the coils of the WPT system changes

Wireless Sensor Node Using a Rotational Energy Harvester with Adaptive Power Conversion

Published versio