Maximum Effectiveness of Electrostatic Energy Harvesters When Coupled to Interface Circuits

Accepted versio

Dynamic thermal rating of a Modular Multilevel Converter HVDC link with overload capacity

© 2015 IEEE.The power rating of Modular Multilevel Converter based HVDC has increased rapidly over the past decade, with individual links in the gigawatt power range now technically feasible and further power increases on the horizon. Such large links may be required to provide ancillary services such as fast frequency response or emergency power re-routing in the event of a system disturbance. Providing such services may require converters to be designed with overload capacity. This paper examines how the thermal aspects of semiconductor devices may impact the operation of such converters and how the exploitation of short-term thermal dynamics may lead to dynamic overload rating

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

The Alternate Arm Converter: A New Hybrid Multilevel Converter With DC-Fault Blocking Capability

This paper explains the working principles, supported by simulation results, of a new converter topology intended for HVDC applications, called the alternate arm converter (AAC). It is a hybrid between the modular multilevel converter, because of the presence of H-bridge cells, and the two-level converter, in the form of director switches in each arm. This converter is able to generate a multilevel ac voltage and since its stacks of cells consist of H-bridge cells instead of half-bridge cells, they are able to generate higher ac voltage than the dc terminal voltage. This allows the AAC to operate at an optimal point, called the “sweet spot,” where the ac and dc energy flows equal. The director switches in the AAC are responsible for alternating the conduction period of each arm, leading to a significant reduction in the number of cells in the stacks. Furthermore, the AAC can keep control of the current in the phase reactor even in case of a dc-side fault and support the ac grid, through a STATCOM mode. Simulation results and loss calculations are presented in this paper in order to support the claimed features of the AAC

Mixed Electromechanical Simulation of Electrostatic Microgenerator Using Custom-Semiconductor Device Models

Published versio

Architectures for vibration-driven micropower generators

Published versio

Energy harvesting from human and machine motion for wireless electronic devices

Published versio

Micro-machined variable capacitors for power generation

Accepted versio

Effective Damping Support through VSC-HVDC Links with Short-Term Overload Capability

Damping service provision through VSC-based HVDC links has been extensively covered in the literature. However, little or no attention has been paid to the available range of active and reactive power modulation when the HVDC link is already operating at rated capacity. In these conditions some overload capability is usually assumed, ignoring the physical constraints imposed by the safe operating area of the IGBT modules in the converter. This paper presents, in a unified framework, the provision of damping support from VSC-HVDC links equipped with additional control for short-term overload capability. The performance of a Model Predictive Control (MPC) damping controller that accounts for the extended P/Q operating area of the converter is analysed. Case studies are presented to show that the extracted short-term overload capability can significantly improve the damping support from VSC-HVDC links. Simulation results also include the impact of damping control action on the junction temperatures of the IGBT modules of the converters, quantifying the effect of this service on the semiconductor temperature dynamics