Comparison between PI and PR current controllers in grid connected PV inverters

This paper presents a comparison between Proportional Integral (PI) and Proportional Resonant (PR) current controllers used in Grid Connected Photovoltaic (PV) Inverters. Both simulation and experimental results will be presented. A 3kW Grid- Connected PV Inverter was designed and constructed for this research.peer-reviewe

Design of PR current control with selective harmonic compensators using Matlab

This paper presents a procedure to design a Proportional Resonant (PR) current controller with additional PR selective harmonic compensators for Grid Connected Photovoltaic (PV) Inverters. The design of the PR current control and the harmonic compensators will be carried out using Matlab. Testing was carried out on a 3kW Grid- Connected PV Inverter which was designed and constructed for this research. Both simulation and experimental results will be presented.peer-reviewe

Single-phase microgrid with seamless transition capabilities between modes of operation

Microgrids are an effective way to increase the penetration of DG into the grid. They are capable of operating either in grid-connected or in islanded mode thereby increasing the supply reliability for the end user. This paper focuses on achieving seamless transitions from islanded to grid-connected and vice versa for a single phase microgrid made up from voltage controlled voltage source inverters (VC-VSIs) and current controlled voltage source inverters (CC-VSIs) working together in both modes of operation. The primary control structures for the VC-VSIs and CC-VSIs is considered together with the secondary control loops that are used to synchronize the microgrid as a single unit to the grid. Simulation results are given that show the seamless transitions between the two modes without any disconnection times for the CC-VSIs and VC-VSIs connected to the microgrid.peer-reviewe

Reactive power sharing and voltage harmonic distortion compensation of droop controlled single phase islanded microgrids

When paralleling multiple inverters that are capable of operating as an island, the inverters typically employ the droop control scheme. Traditional droop control enables the decentralized regulation of the local voltage and frequency of the microgrid by the inverters. The droop method also enables the inverters to share the real and reactive power required by the loads. This paper focuses on some of the limitations of parallel islanded single phase inverters using droop control. Algorithms with the aim to address the following limitations in islanded operation were proposed: reactive power sharing and reduction of the voltage harmonic distortion at the point of common coupling (PCC). Experimental results were then presented to show the suitability of the proposed algorithms in achieving reactive power sharing and in improving the voltage harmonic distortion at the PCC.peer-reviewe

Control of a doubly fed induction machine in a wind energy conversion system

This paper presents research done on the closed-loop control of the Doubly Fed Induction Machine (DFIM) applied to a Wind Energy Conversion System (WECS). Basic generator configurations used in wind energy systems, mainly fixed-speed and adjustable speed generators are discussed. A suitable Stator Flux Oriented (SFO) control topology for the DFIM is shown with which it is possible to control the stator active and reactive power. The control system designed was implemented on an experimental rig which emulates the behaviour of a practical WECS. A brief overview of sensorless algorithms is also presented; these algorithms are used to provide rotor speed/position estimates in the absence of a speed sensor. Practical results in both sensored and sensorless operation are shown including measurements for rotor currents, stator active/reactive power and rotor speed/position estimates.Alternative Technologies Ltd., Energy Investment Ltd, JMV Vibro Blocks Ltd., Solar Engineering Ltd. and Solar Solutions Ltd.peer-reviewe

Design of a high efficiency wide input range isolated Cuk Dc-Dc converter for grid connected regenerative active loads

The objective of this research is to build a regenerative active load unit with a very wide input voltage range in order to support a wide variety of dc supply equipment such as dc power supplies and batteries. These are usually tested by active or passive load units (resistive loads) for long periods of time to detect early failures and reliability issues. The power drawn from the devices under test are dissipated into heat by the resistive loads. The system being proposed in this paper will consist of a grid connected inverter and an efficient wide input voltage range dc-dc converter. This system will allow the energy drawn from the devices under test to be fed back to the grid. The only energy consumed corresponds to the losses within the system. The aim of the project is concerned with the construction of a 1kW regenerative active load unit. The dc-dc converter, irrespective of the input voltage will feed power at a constant voltage of 200V to the grid connected inverter. An input voltage ranging from 35V up to 400V will be supported by the regenerative active load unit with a handling power of 1kW throughout the whole range. This paper shall present the results obtained during the testing of the 1kW regenerative active load unit.peer-reviewe

Modeling of an EMC test-bench for conducted emissions in solid state applications

In the area of EMC performance of electric motor drives, research is mainly focused on the EMC performance of inverter based drives. However, in most instances the soft starter is still an appropriate choice for motor control especially when accurate speed control of the load is not a specific requirement. The EMI generation of these converters has not been given the required importance, with only a few publications regarding this issue available in the last decades. A simulation model that considers the operation of solid state devices in an EMC conducted emission measurement laboratory environment was developed. The model was implemented in MATLAB® and Simulink® using a time domain approach. Models for the LISN, EMI receiver, power cables, thyristor power modules and induction motor load were developed and implemented. These models were developed so as to reflect the actual physics of the components and, where possible, model parameters were obtained through analysis of the geometry of the system through simplifications of the surrounding environment. The simulation was then used to gain insight on the EMI generation mechanisms of the solid state system.non peer-reviewe