Abstract:A shunt active filter is capable of removing harmonic currents from the supply of commercial and industrial sites. This paper presents a novel method for generating the compensating current signal for an active filter that uses a three-level inverter to provide a fast transient response. It is shown that the active filter must be positioned downstream of the power factor correction capacitors for stable operation. A new compensating current technique, based on sinusoidal subtraction, together with the faster response of the three-level inverter produces a shunt active filter system that has superior performance compared to traditional two level systems.

Abstract-The harmonic currents generated by the single-phase rectifier are well known. As the levels of these currents become larger, the use of power conditioners such as shunt active filters to lower the levels is becoming more attractive. In order to analyze the interaction between the condition, ac system, and rectifier it is necessary to have an accurate model of the rectifier. This paper describes a frequency-domain analytical model of the single-phase rectifier. The model includes the dominant frequency transfer mechanisms. These are the direct transfer and that due to the modulation of the switching instants. A small-signal linearized analysis is presented and the behavior predicted is confirmed by perturbation analysis using time-domain simulation. Accurate results are obtained, and the importance of including the switching instant modulation is shown.Index Terms-Frequency-domain analysis, harmonic analysis, power quality, rectifier.

Abstract-This paper deals with observations of events that occur in the power system and could effect power quality at a winery. Power system incidents recorded at the site are presented. The impact of the equipment, which includes large induction motors, power factor correction capacitors and halfwave rectifier induction motor heaters on the supply system is described. The disturbance to equipment operation caused by system events such as sags are also detailed. In order to gauge the effect of the power events at the site the opinions of the customer and the supply company on the power quality were sought. These opinions are reported and in general, the events recorded and described caused little detriment to the customers power quality.

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Abstract-This paper presents the analysis of real power system events recorded at a light industrial site to determine the effect of a shunt active filter on power quality. The shunt active filter is shown to improve power quality by lowering the distortion of the supply voltage in both the transient and steady state. The shunt active filter power rating and other design information are also determined. The performance degradation of the shunt active filter when it has a limited rating is then demonstrated. In one case the voltage distortion is made worse by the active filter. The requirements that various transient events, including capacitor switching and induction motor starts, place on the shunt active filter design are outlined. These requirements are such that the required switching frequencies exceed those attainable with IGBTs and transient ratings dominate the active filter design constraints.

A real-time emulation of a modular multilevel converter with integrated energy storage devices has been carried out. The real-time model is detailed and implemented using MicroLabBox/dSPACE. The system is tested and compared to an experimental prototype of the converter. The main advantage of the proposed real-time system is that it gives higher fidelity for further investigations, specifically in electric vehicle applications where it can be integrated into a real-time emulated electric vehicle. The model can be extended to a higher number of levels as it has no constraints on the number of switches or batteries/cells. Also, it can be integrated in a power hardware in the loop system to decrease the testing time of a product. This is a novel proposal of a real-time emulation of the converter in an electric vehicle application using MicroLabBox/dSPACE.

The modular multilevel converter with embedded batteries is a viable alternative in electric vehicle drive systems. This research investigates integrated charging of the embedded batteries in a three-phase converter from a single-phase source without any additional hardware requirements. Two phases of the converter are connected to the supply while the third converter leg is not connected. In a typical charging of the converter batteries, the batteries with a lower state of charge are prioritised. Then all batteries are balanced at an average global state of charge. This research proposes a new sorting algorithm of the converter batteries with an override capability to bypass any individual submodule if required. This bypassing capability is modulation method independent, thus can be integrated with any modulation method. Simulation results and a real-time emulation of the charging system validate the proposed control method and the override algorithm. In addition, an open-loop switching technique is integrated with a new nearest level control-based measurement method of the battery terminal voltage to estimate its initial state of charge. This measurement facilitates a reduced number of voltage sensors for hardware implementation. This method was simulated and validated by comparing the calculated and the measured values of the battery initial state of charge. Real-time emulation of the system utilising hardware-in-the-loop apparatus was carried out, which confirmed the developed control system functions as expected.

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