Showing papers by "Martin Jones published in 2005"

Vector control schemes for series-connected six-phase two-motor drive systems

Abstract: A novel concept for multidrive systems, based on utilisation of multiphase machines, has been introduced recently. It has been shown that, by connecting in series stator windings of the multiphase machines in an appropriate manner, it becomes possible to control all the machines in the group independently using vector control principles, although the whole drive system is supplied from one multiphase voltage source inverter (VSI). The concept has been investigated so far only for true n-phase machines (i.e. machines with spatial displacement between any two consecutive phases equal to 2π/n) and all the available considerations are restricted to the inverter current control in the stationary reference frame. Moreover, all the available proofs of the decoupled dynamic control within these multidrive systems are simulation based. One specific case is discussed in detail; a two-motor series-connected six-phase drive supplied from a six-phase VSI. The two-motor drive system, based on utilisation of a true six-phase machine is considered first and, in addition to inverter current control in the stationary reference frame, inverter current control in the rotating reference frame is also analysed. It is shown that this method of current control requires modifications of the decoupling voltage terms, compared to those valid for a one-motor drive, this being caused by series connection of the two machines. Next, two-motor drives based on utilisation of quasi six-phase machines (with two three-phase stator windings displaced by 30°) are discussed and appropriate connection diagrams are developed. Verification of these schemes is provided by simulation. Finally, an experimental rig, which utilises a true six-phase machine connected in series with a three-phase machine and inverter current control in the stationary reference frame, is described and experimental verification of the decoupled dynamics of the two machines is provided by extensive testing.

Dynamics of a series-connected two-motor five-phase drive system with a single-inverter supply

Abstract: Utilization of multi-phase machines in variable speed drives is nowadays extensively considered for electric ship propulsion, 'more-electric aircraft' and traction applications, including EVs and HEVs. In addition to well-known advantages, use of multi-phase machines enables independent vector control of a certain number of machines that are connected in series in an appropriate manner, with the supply coming from a single voltage source inverter (VSI). The concept was initially proposed for a five-phase series-connected two-motor drive, but is applicable to any system phase number greater than or equal to five. The number of connectable machines is a function of the VSI phase number and detailed theoretical and simulation studies have already been reported for various multi-phase multi-motor drive configurations of this type. However, the available experimental proofs of decoupled dynamic control within series-connected drive systems are currently restricted to the six-phase two-motor drive. The purpose of this paper is to present, for the first time, results of an experimental study on a five-phase two-motor series-connected drive system. A brief overview of the operating principles is provided first This is followed by a description of the experimental rig. The emphasis in the paper is placed on the experimental results, which illustrate dynamics of the vector-controlled two-motor drive during acceleration, deceleration and speed reversal. An experimental proof of the existence of decoupled dynamic control is thus provided.

Vector Control of a Five-Phase Series-Connected Two-Motor Drive Using Synchronous Current Controllers

Abstract: A novel concept for multi-motor drive applications has been developed recently, which enables dynamically decoupled control of all the machines in the group, although a single voltage source inverter is used as the supply. The concept requires utilization of multi-phase machines, whose stator windings have to be connected in series with an appropriate phase transposition, and it has been developed under the assumption that the inverter currents are controlled in the stationary reference frame. This article addresses the possibility of using synchronous current controllers within such a multi-motor drive system in order to realize fully decoupled dynamic control of all machines. The considerations of the article, although restricted to the series-connected two-motor five-phase drive system, can be extended to any other number of phases. It is shown that, in contrast to the situation that arises when current control is performed in the stationary reference frame, current control in the rotating reference fr...

Independent vector control of asymmetrical nine-phase machines by means of series connection

Abstract: The interest in multi-phase machines for high performance applications has been growing in recent years due to their potential advantages over three-phase machines. One of the possibilities of taking advantage of the additional degrees of freedom that exist in multi-phase machines is the series connection of several multi-phase machines, with the supply coming from a single multi-phase inverter. Among the different choices, the quasi nine-phase machine with three sets of three-phase windings spatially displaced by 20 degrees, is particularly attractive for high-power applications. This paper discusses the possibility of connecting a number of such asymmetrical nine-phase machines and explains how independent control can be achieved although a single nine-phase inverter is used as the supply. Mathematical derivations and simulation proof of independent vector control, achievable with this system, are provided for the series connection of three nine-phase machines and a three-phase machine. The existence of the independent control of the machines is fully verified both in torque and speed mode using indirect rotor-flux oriented control principles

Combining Induction and Permanent Magnet Synchronous Machines in a Series-Connected Six-Phase Vector-Controlled Two-Motor Drive

Abstract: It has been shown recently that a number of multi-phase machines can be controlled independently, with the supply coming from a single multi-phase inverter, provided that the stator windings are connected in series in an appropriate manner. One such drive system is a two-motor drive, consisting of a symmetrical six-phase machine connected in series with a three-phase machine. The supply is provided from a six-phase current-controlled voltage source inverter (VSI). This paper examines operation of such a drive system when a six-phase symmetrical induction machine is connected in series with a three-phase permanent magnet synchronous machine (PMSM). Basic operating principles of the drive system are at first reviewed. This is followed by a brief description of the experimental system. An extensive presentation of experimental results, collected from a laboratory setup, is then provided. It is shown that a truly independent and decoupled vector control of the two machines results, although a single supply source is used. The two-motor drive system of the proposed structure is seen as a potentially viable industrial solution for applications requiring one high-power and one low-power machine

Experimental performance evaluation of six-phase series-connected two-motor drive systems

Abstract: It has been shown recently that it is possible to connect in series the stator windings of multi-phase machines in such a way that all the machines in the group can be controlled independently using field orientation principles, although the complete multi-motor drive system is supplied from a single voltage source inverter (VSI) This paper deals with one particular case, a series-connected two-motor six-phase drive system Two configurations are tested experimentally Both include a symmetrical six-phase induction machine, while the second machine is at first a three-phase induction machine and then a permanent magnet synchronous machine (PMSM) Additionally, experimental results obtained with a single six-phase motor drive are included as well, thus enabling a thorough discussion of the dynamic performance of the series-connected two-motor drive systems The operating principles of the drive systems are at first reviewed and a brief description of the experimental rig is then given The emphasis is placed on an extensive presentation of experimental results, collected from the rig in the already mentioned three different configurations An ultimate proof that truly independent and decoupled vector control of the two machines is achieved, although a single supply source is used, is thus provided

Experimental Performance Evaluation ofSix-Phase Series-Connected Two- MotorDriveSystems

Abstract: Ithasbeenshownrecently that itispossible toconnectinseries thestator windings ofmulti-phase machines insuch a way that allthemachines inthegroupcanbecontrolled independently using field orientation principles, although thecomplete multi-motor drive systemissupplied froma single voltage sourceinverter (VSI). This paperdeals with oneparticular case,aseries-connected two-motor six-phase drive system. Twoconfigurations aretested experimentally. Bothinclude asymmetrical sixphaseinduction machine, while thesecond machine isatfirst a three-phase induction machine and then apermanent magnetsynchronous machine (PMSM).Additionally, experimental results obtained witha single six-phase motordrive areincluded aswell, thusenabling a thorough discussion ofthe dynamic performance oftheseries-connected two-motor drive systems. Theoperating principles ofthe drive systems areatfirst reviewed anda brief description oftheexperimental rigisthengiven. The emphasis isplaced on an extensive presentation ofexperimental results, collected fromtheriginthe already mentioned threedifferent configurations. An ultimate proofthattruly independent and decoupled vector control ofthetwomachines isachieved, although a single supply sourceisused, is thusprovided.