Power quality improvement by pre-computed modulated field current for synchronous generators

Although power quality aspects of electrical machines have been extensively studied and investigated for a large number of years, room for improvement still exists in the field of classic, wound-field, synchronous generators. This paper proposes an innovative method of power quality improvement for single-phase synchronous generators in which the usual DC field current is replaced by a calculated current waveform. The optimised field current waveform is designed in such a way that harmonics created by the machine geometry and the winding configuration are significantly reduced

Response to Discussion of “A modular speed-drooped system for high reliability integrated modular motor drives”

The authors appreciate the interest shown in our paper. In the paper under discussion [1], a distributed speed control strategy suitable for multi-three-phase machines with enhanced power sharing capability is presented. The focus of the manuscript is on the power sharing transient controllability achieved by using a sharing regulator based on the droop controller, which was introduced for the first time by Fingas and Lehn [2]. In [1], the authors added the outermost loop in charge of restoring the drooped output speed. The overall control strategy and the design procedure of each loop - current, sharing, and speed - is presented and validated by means of experimental results. Two off-the-shelf three-phase induction machines coupled on the same shaft and controlled by a custom inverter were loaded by a third off-the-shelf three- phase induction machine

Enhanced power sharing transient with droop controllers for multithree-phase synchronous electrical machines

This paper presents a droop-based distributed control strategy for multithree-phase machines that provides augmented controllability during power sharing transients. The proposed strategy is able to mitigate the mutual interactions among different sets of windings without controlling any subspace variable, also offering a modular and redundant design. On the contrary, in a centralized configuration, subspaces would be controlled using the vector space decomposition, but fault tolerance and reliability levels required by the stricter regulations and policies expected in future transportation systems would not be satisfied. The proposed method is analytically compared against the state-of-the-art power sharing technique and equivalent models and control design procedures have been derived and considered in the comparison. Uncontrolled power sharing transients and their effects on mutual couplings among isolated sets of windings have been compared against the proposed regulated ones. Experimental results on a 22-kW nine-phase multithree-phase synchronous machine rig validate the design procedures showing good agreement with the expected performances

A modular speed-drooped system for high reliability integrated modular motor drives

Future transportation challenges include a considerable reduction in pollutant emissions at a time when significant increase in demand is predicted. One of the enabling solutions is the electrification of transport systems as this should lead to improved operability, fuel savings, emission reduction, and maintenance. While state-of-the-art technology has demonstrable benefits there needs to be considerable advancement to meet future transportation affordability and emission targets. Primarily, electrical drives need an improved power density, an increased reliability, and a reduced specific cost. For this reason, integrated modular motor drives (IMMDs) present an attractive solution. Modularity leads to redundancy and easier integration. This paper presents a novel speed-drooped control system applied to motors fed by modular paralleled converters. This control technique allows precise speed regulation and power sharing among different segments showing improved fault tolerance and reliability. The design procedure and the power sharing dynamic have been presented and analyzed by means of MATLAB/Simulink and validated in a 3-kW experimental rig, showing good agreement with the expected performance

Adaptive saturation system for grid-tied inverters in low voltage residential micro-grids

Provision of ancillary services, like power quality improvement is a key to attain higher utilization of multifunctional grid-tied inverter. However, the power quality improvement is mainly limited by the power capacity the grid-tied inverter. This paper explores integration issues of the next-generation intermittent power sources. In particular, two different strategies for enhancing power quality given the residual power capacity of the inverters are developed. One strategy aims to obtain the expected power quality exploiting the dynamic saturation of the inverter rated apparent power and another strategy is based on peak current detection. Both strategies offer the possibility to generate appropriate references for the inner current control loop. The two proposed strategies are compared in performance, and a discussion on their practical implementation for the best performance of the inverters is provided78478915th IEEE International Conference on Environment and Electrical Engineering (EEEIC

Distributed current control for multi-three phase synchronous machines in fault conditions

Among challenges and requirements of on-going electrification process and future transportation systems there is demand for arrangements with both increased fault tolerance and reliability. Next aerospace, power-train and automotive systems exploiting new technologies are delving for new features and functionalities. Multi-three phase arrangements are one of these novel approaches where future implementation of aforementioned applications will benefit from. This paper presents and analyses distributed current control design for asymmetrical split-phase schemes composed by symmetrical three phase sections with even number of phases. The proposed design within the dq0 reference frame in nominal, open and short circuit condition of one three-phase system is compared with the vector space decomposition technique and further validated by mean of Matlab/Simulink ~R simulations

uCube: control platform for power electronics

This paper presents a versatile tool for development, control and testing of power electronics converters. In the last decade, many different expensive off-the-shelf tools for rapid prototyping and testing have been developed and commercialised by few market players. Recently, the increasing diffusion of low cost, Do It Yourself targeted development tools gained market shares previously controlled by conventional players. This trend has been driven by the fact that, despite their lower performances, many of these low cost systems are powerful enough to develop simple power electronics systems for learning and teaching purposes. This paper describes a control platform developed within the University of Nottingham, targeting at the market and application segment in between the expensive off-the-shelf control boards and the low cost emerging systems. The platform is based on the Microzed evaluation board, equipped with the Xilinx Zynq System-on-Chip. Its flexibility, features and performances will be addressed and examples of how they are being experimentally validated on different rigs will be provided

Load characterization and revenue metering under non-sinusoidal and asymmetrical operation

This paper proposes an approach to load characterization and revenue metering, which accounts for the influence of supply deterioration and line impedance. It makes use of the Conservative Power Theory and aims at characterizing the load from the measurements done at the point of common coupling. Despite the inherent limitations of a single-point measurement, the proposed methodology enables evaluation of power terms, which clarify the effects of reactivity, asymmetry and distortion, and attempts to depurate the power consumption accounted to the load from those terms deriving from supply nonidealities

Series Chain-link Modular Multilevel AC/DC Converter (SCC) for HVDC Applications

Introduction of the Modular Multilevel Converter (MMC) has enabled the exploitation of Voltage Source Converters (VSCs) in an increasing number of High Voltage Direct Current (HVdc) applications. Subsequently, some new topologies and solutions have been presented to tailor the MMC concept to specific uses. Particular attention has been paid to reduction of the converter footprint for applications where plant size is a critical economic aspect, for example, in off-shore installations. This paper introduces a new series connected modular multilevel AC/DC converter, the Series Chain-link Converter (SCC), which gives a significant reduction in the required number of submodules (SMs) and a more compact distribution of the energy storage, compared to an MMC. In the paper, the operating principle of the converter and its design are discussed in detail; the sub-module count and energy storage requirement are also given. The basic control loops required for the practical operation of the converter are presented and designed. The SCC concept has been experimentally validated on a small-scale 450V DC, 415V ac, 4.5kVA laboratory prototype, confirming the practical viability of the topology