Hybrid Multicarrier Random Space Vector PWM for the Mitigation the Acoustic Noise

The pulse width modulation (PWM) inverter is obvious for any industrial and power sector application. Particularly industrial drives are very keen on the industrial standards. Many modulations approached such a drives objects of DC-link consumption, harmonics suppression in lower and higher order spectrum and noise reduction. The still random PWM is a best candidate for reducing the noises on the PWM operated AC drives. There are various Random PWM (RPWM) methods has been developed and investigated for the PWM inverter fed drive noise reductions, still the shortcomings are existence on these method items of their less randomness and complex digital circuitry. These PWM dealt the spreading harmonics there by decreasing harmonic effects on the system. However, these techniques overlook the effect of acoustic noise and DC -link utilizations Therefore, in this paper mainly deals with to combined RPWM principle in space vector PWM (SVPWM) to generate random PWM generation using asymmetric frequency multi carrier called multicarrier random space vector PWM (MCRSVPWM). The SVM agreements with multicarrier (different fixed frequencies as carrier waves) which are chosen with the aid of a random binary bit generator. The proposed RSVM generated pulses with a randomized triangular carrier (4 ± 1.5 kHz), while the conventional RPWM method contains of the random pulse position with a fixed frequency triangular carrier. The simulation study is performed through MATLAB/Simulink for 3 HP asynchronous induction motor drive. The Experimental validation of proposed MCRSVPWM is tested with 2kW six switch (Power MOSFET – SCH2080KE) inverter power module fed induction motor drive.publishedVersio

Impact of PWM strategies on RMS current of the DC-link Voltage Capacitor of a dual-three phase drive

The major drawback of usual dual three-phase AC machines, when supplied by a Voltage Source Inverter (VSI), is the occurrence of extra harmonic currents which circulate in the stator windings causing additional losses and constraints on the power component. This paper compares dedicated Pulse Width Modulation (PWM) strategies used for controlling a dual three phase Permanent Magnet Synchronous machine supplied by a six-leg VSI. Since the application is intended for low-voltage (48V) mild-hybrid automotive traction, an additional major constraint arises: the compactness of the drive related to the size of the DC-bus capacitor. Thus, the PWM strategy must be chosen by taking into consideration its impact on both, the motor and the RMS value of DC-bus current

PWM Techniques for Control of Dual-Inverter Supplied Six-Phase Drives

Among the different multiphase ac drive solutions, one of the most widely reported in the literature is the six-phase machine. The machines can be realised into two different configurations, symmetrical and asymmetrical. For the symmetrical configuration, the stator winding consists of two sets of three-phase windings that are spatially shifted by 60 degrees where spatial displacement between any two consecutive phases is the same and equal to 60 degrees. For the asymmetrical configuration, the two sets of three-phase windings are spatially shifted by 30 degrees. As a result, the spatial shift between consecutive phases becomes non-equidistant.In this thesis, modulation techniques for both symmetrical and asymmetrical six-phase machines are investigated. The machines are configured in open-end winding configuration where both ends of the stator winding are connected to separate isolated inverters in a topology known as dual-inverter supply. Compared to conventional single-sided supply topology where one end of the winding is connected to an inverter while the other side is star-connected, some additional benefits are offered by the dual-inverter supply topology. First, fault tolerance of the drive is improved, since the supply is realised with two independent inverters. In case one of the inverters is faulted, the other can continue to provide power to the machine. Second, the same phase voltages can be achieved with half the dc-link voltages on the two inverter inputs compared to the single-sided supply, which can be useful in applications such as electric and hybrid electric vehicles and medium sized ships, where the dc voltage levels are limited. Further, due to the nature of the topology, additional diodes and capacitors like in the Neutral Point Clamped (NPC) and Flying Capacitor (FC) VSIs are not required. The latter results in a further advantage - capacitor voltage balancing techniques are not required.Two pulse width modulation (PWM) techniques for control of the dual-inverter supplied six-phase drives are proposed in this thesis. The first is a reference sharing algorithm where the inverters are modulated using reference voltage that is shared equally and unequally between the two modulators. For both symmetrical and asymmetrical six-phase drives, a better performance, in term of total harmonic distortion (THD) of phase voltage is obtained when the reference is shared unequally between the two modulators. The second technique is carrier-based modulation where the modulation of the two inverters is determined by the disposition of the carrier signals. Three variations of carrier signals disposition are investigated namely; the phase disposition (PD-PWM), alternate phase opposition disposition (APOD-PWM) and phase-shifted PWM (PS-PWM). For the symmetrical six-phase drive, the best phase voltage and current THDs are obtained using APOD-PWM while for asymmetrical six-phase drive, the APOD-PWM produces the worst current THD despite having the best voltage THD among the three methods.All the developed modulation techniques are analysed using simulations and experiments undertaken using a laboratory prototypes. The waveforms and spectra of phase voltage and load current obtained from the simulation and experimental works are presented in this thesis together with the THD of both the voltage and current over entire linear modulation range

Multiple Three-Phase Induction Generators for Wind Energy Conversion Systems

During the past decade, there has been a considerable increase in the number of published works on multiphase machines and drives. This increased interest has been largely driven by a need for the so-called green energy, i.e. energy generated from renewable sources such as wind, and also an increased emphasis on greener means for transportation. Some of the advantages multiphase machines offer over three-phase counterparts are better fault tolerance, smaller current and power per phase, and higher frequency torque ripple. This thesis examines use of a multiphase induction generator in wind energy conversion systems (WECS). In particular, multiphase generators that comprise multiple 3-phase winding sets, where each winding set is supplied using an independent 3-phase voltage source inverter (VSI), are studied. It is claimed that these topologies offer advantages in cases where a WECS is connected to a multitude of independent ac or dc microgrids, systems where a single high-voltage dc link is needed or where a simple fault tolerance is achieved when a complete winding set is switched off. All of these examples require an arbitrary power or current sharing between winding sets. In order to achieve arbitrary current and power sharing, the control can be implemented using multi stator (MS) variables, so that the flux and torque producing currents of each winding set can be arbitrarily set. As an alternative, this thesis uses vector space decomposition (VSD) to implement the control, while individual winding set flux/torque producing currents are governed by finding the relationships between MS and VSD variables. This approach has all the advantages of both MS and VSD, i.e. access to individual winding set variables of MS and the ability to implement control in the multiple decoupled two dimensional subspaces of VSD, while heavy cross coupling between winding set variables, a weakness of MS, is avoided. Since the goal of the thesis is to present use of multiphase machines in WECS, modelling and simulation of a simple multiphase WECS in back-to-back configuration has been performed at first. All systems relevant to machine control where considered, such as grid and machine side VSIs, grid filter, indirect rotor field oriented control, current control in both flux/torque producing and non-producing subspaces, low order harmonic elimination, maximum power point tracking control, and voltage oriented control of the grid side VSI. Moreover, various WECS supply topologies were considered where developed current and power sharing would be a necessary requirement. Development of the proposed current sharing control commences with an analysis of multiple 3-phase machine modelling in terms of both MS and VSD variables. Since the actual control is implemented using decoupled VSD variables, VSD modelling has been studied in detail, resulting in an algorithm for creation of the VSD matrix applicable to any symmetrical or asymmetrical multiphase machine with single or multiple neutral points. Developed algorithm always decouples the machine into orthogonal two-dimensional subspaces and zero sequence components while making sure that all odd-order harmonics are uniquely mapped. Harmonic mapping analysis is offered as well. Next, relationship between MS and VSD variables has been developed by mapping MS variables into VSD subspaces. Since VSD matrix creation algorithm is valid for any multiphase machine, relationship between MS and VSD variables is applicable to any multiple 3-phase machine regardless of the configuration (symmetrical/asymmetrical), number of neutral points or machine type (synchronous or induction). Established relationship between MS and VSD has been used to implement current sharing control in decoupled VSD subspaces of the machine. It is shown that in order to achieve arbitrary current sharing it is only necessary to impose currents in flux/torque non-producing subspaces. Hence, total machine’s flux and torque are not affected at all. Besides verification by Matlab simulations, two topologies are experimentally investigated, a parallel machine side converter configuration and the case when a single high voltage dc link is created by cascading dc-links of the machine side VSIs. In the first case the ability of arbitrary current sharing between winding sets is validated, while the second tested topology demonstrates use of the developed control for the purpose of voltage balancing of the cascaded dc links

Development of pulse-width-modulation techniques for multi-phase and multi-leg voltage source inverters

A huge body of work has been published in recent times in the area of multi-phase machines and drives. Many aspects of these drives have been analysed, such as reduction of torque pulsations, increased reliability and fault tolerance, improved power sharing capabilities and possibilities for realisation of series-connected multi-motor drives with supply coming from a single multi-phase voltage source inverter (VSI). Various pulse width modulation (PWM) schemes have been developed for multi-phase machines with concentrated and distributed windings, utilising both carrier-based PWM and space vector PWM (SVPWM) approaches. However, no systematic analysis has been performed in order to determine properties of multi-phase PWM in general, and to establish close correlation between carrier-based PWM and space vertor PWM, for multi-phase VSIs. This thesis presents an analysis and development of multi-phase PWM schemes for sinusoidal output voltage generation with two-level muhi-phase VSIs, which are suitable for multi-phase machines with distributed windings. Therefore, attention is paid to the elimination of low order harmonics. The scope of the thesis has been narrowed down to the continuous PWM schemes and operation in the linear region of the modulation only. Both multi-phase carrier-based PWM and SVPWM schemes are considered, and, in particular, five-phase, seven-phase e-phase systems are addressed in detail. Thus, a strong link between these two different approaches is established, allowing for an easier comparison of the features offered by each method. All PWM schemes are practically implemented in a DSP and experimentally verified through extensive experimentation on the custom-built multi-phase VSI. In addition to the methods of sinusoidal output voltage generation, achieved by means of the synthesis of the reference in only the first plane of the multi-phase system with simultaneous zeroing of voltages in all the other planes

Continuous and discontinuous modulation techniques for multiphase drives: analysis and contributions

Falta palabras clavesThe study of multiphase machines applications is an emergent field of research mainly because of the high reliability they offer for high power applications. Nowadays, they are predominantly supplied from two-level voltage source inverters (VSIs). For the purpose of the inverter control, both carrier-based and space vector pulse width modulation (PWM) techniques have been developed, for various phase numbers, which are capable of generating required sinusoidal output voltages. Both methods are usually a general extension of modulation methods used in the three-phase case. The relationship between continuous carrier-based and space vector PWM has been reported in the scientific literature for the multiphase case, stating analogies and differences. Discontinuous PWM techniques for multiphase inverters have also received some attention as well, but at a lesser extent than the continuous PWM techniques, always in relation to multiphase systems. In this work for filling aforementioned gap, discontinuous modulation methods are first analysed in multiphase drives. The natural consequence of the existence of different PWM strategies is the inherently different behaviour with regard to the performance indicators that can be used to assess the quality of output waveforms. Among these performance indicators, one of the most interesting used in three phase induction machines for the evaluation of switching characteristics and the current ripple are the ux harmonic distortion factor (HDF). However, HDF has been only very recently introduced in the multiphase case, and for asymmetrical six-phase induction machines that can be considered like two three phase machines in the same case. Consequently, there is quite few work in the scientific literature and the multiphase induction machine case in the evaluation of switching characteristics and the current ripple using HDF. Therefore, the extension of HDF for the evaluation of switching characteristics and the current ripple in the multiphase case is studied and analysed like a second main goal of this Thesis. Notice that SVM has been also extended to the multiphase case. However, most scientific literature relates the general case, where linear operation regions are only considered. A third goal of the work is the extension of the operation region of the SVM-multiphase scheme. In this field, non linear operation in the overmodulation region is also considered, guaranteeing a smooth and linear transition characteristic between linear and overmodulation regions, minimizing the unwanted voltage amplitude of low order voltage harmonic components. Then, a simple algorithm is proposed with the ability to minimize xy voltage and current components in any multiphase induction machine with any odd number of phases. Finally, the reduction of Common Mode Voltage (CMV) is an interesting topic in the modulation techniques field because it is known to be the cause of electromagnetic interference (EMI), breakdown of windings insulation, fault activation of current detector circuits and leakage currents problems that can damage the motor bearings. The commonmode voltage issue is also studied in this Thesis, and a SVM method is proposed to minimize its content in the electromechanical system. Major contributions of this dissertation have been published in seven journal and three conferences papers, although related work have been also published in another four journal papers. The main contributions covered in this work are the following: Paper 1: D. Dujic, M. Jones, E. Levi, J. Prieto, F. Barrero, “Switching Ripple Characteristics of Space Vector PWM Schemes for Five-Phase Two-Level Voltage Source Inverters-Part 1: Flux Harmonic Distortion Factors," IEEE Transactions on Industrial Electronics, vol.58, no.7, pp.2789-2798, July 2011. Paper 2: M. Jones, D. Dujic, E. Levi, J. Prieto, F. Barrero, “Switching Ripple Characteristics of Space Vector PWM Schemes for Five-Phase Two-Level Voltage Source Inverters-Part 2: Current Ripple," IEEE Transactions on Industrial Electronics, vol.58, no.7, pp. 2799-2808, July 2011. Paper 3: J. Prieto, M. Jones, F. Barrero, E. Levi, S. Toral, “Comparative Analysis of Discontinuous and Continuous PWM Techniques in VSI-Fed Five-Phase Induction Motor," IEEE Transactions on Industrial Electronics, vol.58, no.12, pp.5324-5335, Dec. 2011. Paper 4: J. Prieto, F. Barrero, E. Levi, S. Toral, M. Jones, M. J. Durán, \Analytical Evaluation of Switching Characteristics in Five-Phase Drives with Discontinuous Space Vector Pulse Width Modulation Techniques", EPE Journal, vol.23, no.2, pp.24-33, Jun. 2013. Paper 5: J. Prieto, E. Levi, F. Barrero, S. Toral, “Output current ripple analysis for asymmetrical six-phase drives using double zero-sequence injection PWM," Proceedings of 37th Annual Conference on IEEE Industrial Electronics Society (IECON 2011), pp.3692-3697, Nov. 2011. Paper 6: M.J. Dur_an, J. Prieto, F. Barrero, J.A. Riveros, H.Guzmán, “Space- Vector PWM With Reduced Common-Mode Voltage for Five-Phase Induction Motor Drives," IEEE Transactions on Industrial Electronics, vol.60, no.10, pp.4159- 4168, Oct. 2013. Paper 7: M.J. Duran, J. Prieto, F. Barrero, “Space Vector PWM With Reduced Common-Mode Voltage for Five-Phase Induction Motor Drives Operating in Overmodulation Zone," IEEE Transactions on Power Electronics, vol.28, no.8, pp.4030-4040, Aug. 2013. Paper 8: J. Prieto, F. Barrero, M. J. Durán, S. Toral, M.A. Perales, \SVM Procedure for n-phase VSI With Low Harmonic Distortion in the Overmodulation Region," IEEE Transactions on Industrial Electronics, vol.61, no.1, pp.92-97, Jan. 2014. Notice that all the proposals were validated using simulation and experimental results, and different five-phase and asymmetrical six-phase induction machines available at the labs of the Liverpool John Moores University and the University of Seville, being the candidate one of the main contributors to the obtained publications.Premio Extraordinario de Doctorado U

An Open-End Winding Four-Level Five-Phase Drive

A four-level five-phase open-end winding (OeW) drive topology is introduced in this paper. The drive comprises a five-phase induction machine with open-end stator windings, supplied using two two-level voltage-source inverters with isolated and unequal dc-link voltages, in the ratio 2 : 1. The topology offers the advantages of a modular structure with fewer semiconductor components and has a greater potential for fault tolerance, as compared with an equivalent single-sided four-level drive. Due to the large number of switching states, development of a suitable space vector pulsewidth-modulation (PWM) method can be challenging. Hence, this paper examines the implementation of two-level-shifted carrier-based PWM methods. The effect of dead time on the drive performance is discussed, and it is shown that simultaneous PWM switching of both inverters can lead to degraded output phase voltage waveforms. Detailed analysis of this phenomenon is presented, a solution is proposed, and the modified modulation techniques are incorporated in an experimental setup, at first in conjunction with V/f control. Once the proof of concept has been provided, full field-oriented control is implemented in this OeW drive topology for the first time; detailed experimental testing is conducted, and results are reported