Martina Calais

Inverters for single-phase grid connected photovoltaic systems-an overview

An overview on developments and a summary of the state-of-the-art of inverter technology in Europe for single-phase grid-connected photovoltaic (PV) systems for power levels up to 5 kW is provided in this paper. The information includes details not only on the topologies commercially available but also on the switching devices employed and the associated switching frequencies, efficiency, price trends and market share. Finally, the paper outlines issues associated with the development of relevant international industry standards affecting PV inverter technology.

Multilevel converters for single-phase grid connected photovoltaic systems-an overview

Multilevel voltage source inverters offer several advantages compared to their conventional counterparts. By synthesising the AC output terminal voltage from several levels of voltages, staircase waveforms can be produced, which approach the sinusoidal waveform with low harmonic distortion, thus reducing filter requirements. The need of several sources on the DC side of the converter makes multilevel technology attractive for photovoltaic applications. This paper provides an overview an different multilevel topologies and investigates their suitability for single-phase grid connected photovoltaic systems. Several transformerless photovoltaic systems incorporating multilevel converters are compared regarding issues such as component count and stress, system power rating and the influence of the photovoltaic array earth capacitance.

String and module integrated inverters for single-phase grid connected photovoltaic systems - a review

This work presents an overview on recent developments and a summary of the state-of-the-art in inverter technology for single-phase grid connected photovoltaic (PV) systems. The information provided includes details on commercially available European string and module integrated PV inverters, their efficiency, price trends and market share. This review is given for inverters for a power level up to 6 kW. Furthermore, the paper deals with the recent developments of new inverter topologies and PV system concepts and discusses possible future trends.

Analysis of multicarrier PWM methods for a single-phase five level inverter

This paper investigates and analyses different multicarrier PWM methods for a single phase five level cascaded inverter. Carrier disposition methods, phase shifted and a hybrid method are discussed with respect to resulting switching frequencies, complexity of implementation, spectrum of the output waveform, and the use of inverter state redundancies to perform additional application specific control tasks, such as power flow control from each DC source. A concept of separating the waveshaping function from the switch selection is explored and selected experimental results are presented.

Multilevel converters for single-phase grid connected photovoltaic systems: an overview

Multilevel voltage source inverters offer several advantages compared to their conventional counterparts. By synthesising the AC output terminal voltage from several levels of DC voltages, staircase waveforms can be produced, which approach the sinusoidal waveform with low harmonic distortion, thus reducing filter requirements. The need of several sources on the DC side of the converter makes multilevel technology attractive for photovoltaic applications. This paper provides an overview on different multilevel topologies and investigates their suitability for single-phase grid connected photovoltaic systems. Several transformerless photovoltaic systems incorporating multilevel converters are compared regarding issues such as component count and stress, system power rating and the influence of the photovoltaic array earth capacitance.

A transformerless five level cascaded inverter based single phase photovoltaic system

This paper describes the current control method and the switching scheme of a cascaded five level inverter based grid connected single phase photovoltaic system. For the current control a dual polarised ramptime zero average current error control method is applied, which provides good current regulation, and a narrow ripple current frequency band. Simulation results which demonstrate the method are presented. The redundant inverter states of the five level cascaded inverter allow for a cyclic switching scheme which minimises the switching frequency, equalises stress evenly on all switches and minimises the voltage ripple on the DC capacitors. Simulation and experimental results of a multi carrier PWM voltage controller showing the effectiveness of the switching scheme are presented.

A cascaded inverter for transformerless single-phase grid-connected photovoltaic systems

The design and control issues associated with the development of a 1.8 kW prototype single-phase grid-connected photovoltaic system incorporating a multilevel cascaded inverter are discussed in this paper. For the current controller a ramptime zero average current error control algorithm combined with an optimised cyclic switching sequence is suggested. Simulation results are presented to demonstrate the suitability of the control method.

A ripple based maximum power point tracking algorithm for a single phase grid connected photovoltaic system

This paper describes a maximum power point tracking algorithm for a single-phase, grid-connected photovoltaic system with a transformerless, diode-clamped inverter. The algorithm is based on the fact that in single-phase systems the instantaneous power oscillates at twice the line frequency. The oscillation of the AC power also causes a ripple of twice the line frequency on the DC voltage and DC power of the photovoltaic array. The described algorithm requires the analysis of the phase relationship between the DC voltage and DC power ripple to determine the maximum power point. To establish a steady state balanced system a secondary DC-voltage controller is applied. Simulation results are presented and compared with the perturb and observe method and show the superiority of the proposed algorithm.

Marketing residential grid-connected PV systems using a Balanced Scorecard as a marketing tool

A strategic analysis of the electricity market in Western Australia yields a market potential for renewable energy in Western Australia. However, from a purely financial viewpoint the installation of grid-connected pv-systems still is not economically viable. In this paper a balanced scorecard (BSC) is developed to capture and visualize other than financial benefits. Therefore, the BSC can be used as a marketing tool to communicate the benefits of a privately owned GCPV system to potential customers.

Increasing Accessibility to Science in Early Childhood Teacher Education Through Collaboration Between Teacher Educators and Science/Engineering Academics

The challenge of better preparing pre-service early childhood teachers to deliver appropriate science learning experiences in the classroom poses complex yet relevant issues. An innovative strategy to solve this problem has been a unique cross-discipline and collaborative approach. The purpose of this innovation was to provide pre-service early childhood teachers with the best possible chance of acquiring the requisite science content to merge with their pedagogical skills and thus increase their confidence to teach science in the classroom. The collaborative approach involved teacher educators and science/engineering academics together developing science resources and implementing them through team-teaching within the pre-service teachers’ science methods course. Data collection from the pre-service teachers included pre- and post-questionnaires, open-ended questions, poster analysis and semi-structured interviews. Across the course, the pre-service teachers’ confidence to teach science increased due to being shown how to teach science to young children, the wide range of ideas and activities presented that could be transferred to the early childhood classroom and increased science content knowledge. Science content knowledge increased due to active participation within the science methods course, access to science/engineering academics to explain concepts and information presented within the new science resources. This collaborative approach to developing and implementing science resources within a science methods course increased pre-service teachers’ accessibility to science and encouraged the teaching of science in the early childhood classroom.