Management Meeting Progress Report MB2 - 10 May 2018

1. Management Meeting Progress ReportMB2 - 10 May 2018

2. Recruitment Project Manager Keith DEAN (10/2017) 3 RAs recruited (3 years) ShaoshenXUE (11/2017) LirenHUANG (5/2018) Tao WANG (7/2018) 7+3 PhDs recruited (10 in proposal, 12-13 planed, 2-3 to recruit) Yanxin LI (1/10/2014-30/12/2017) Jaime Maravi NIETO (9/2017 (9/2015)) Ximeng WU (9/2017(9/2016)) Luke COWLING (9/2017) Jin XU (9/2017) Dileepkumar KP (9/2017) Yi WEI (10/2017) TianyiLIU (12/2017) SumeetSingh THAKUR (2/2018) Rajesh KUMAR (3/2018)

3. EPSRC PP - PhD Outlines – 2017-2018 Entry PhD Students and Research Associates Unrestricted

4. EPSRC PP - PhD Outlines – 2017 Entry PhD Students and Research Associates Unrestricted

5. Meetings Project management meetings Weekly – Monday every week Technical meetings Weekly (individual) – Monday every week Monthly (EMD team) – last Monday of each month SGRE engineers attend the monthly technical meetings Technical meetings with SGRE engineers Keele visit, 7 March 2018 External meeting ShaoshenXue, Z.Q. Zhu, Dave Stone, Martin Foster, Guangjin Li, Antonio Griffo, 17-19 April 2018, IET Power Electronics, machines and Drives International Conference, PEMD2018, Liverpool, UK

6. EPSRC Prosperity Partnership • Technical Visit to Siemens Keele R&D Centre • 7 March 2018 Prof. Z.Q. ZhuProf. Martin FosterDr Antonio GriffoDr MilijanaOdavicLuke CowlingSumeet ThakurJin XuYi WeiXimeng WuTianyi LiuDr Richard ClarkDr Nick HaywoodDr Paul GodridgeDr Jiaming LiuDr Edward Horseley

7. Management Meeting Progress ReportMB2 - 10 May 2018

8. Sheffield-EMD

9. WP1.1. Development and design optimisation of novel modular balanced multi-3-phase direct-drive PM generators • 1PDRA & 2PhDs ->1PDRA & 3PhDs. (1PDRA on new machine topologies, full-size generators, scalability study, 1PhD on modular multi-3-phase generators, 1PhD on multi-phase generators) • PhD: Dileep Kumar (1/10/2017) - Vernier PM generator • Comparison of 3MW Vernier machines against conventional machines • Optimisation of Vernier machine for different slot-pole number combinations  • Loss and efficiency estimation for laminated and solid rotor Vernier machines • System level cost and efficiency comparison between Vernier and conventional machine drive systems • Finding new topology for Vernier machine to improve PF or cost of the machine • PhD: Rajesh Kumar (1/3/2018) – Transverse flux PM machine • Literature review • Familiarisation with different finite element software • Complete literature review and report • Initial analysis of transverse flux machines • PhD: Yanxin Li (1/10/2014-30/12/2017) – Modular PM generators • Novel modular 3kW PM generators developed & prototyped, as well as experimentally validated • RA: Dr ShaoshenXue(1/12/2017) – Loss in PM generator • 2D/3D modelling of generators • 3D rotor loss analysis of generators • Review of existing 2D+ analytical eddy current prediction methods • Developing a proposed 2.5D method to predict eddy current loss with FE validation

10. 1PDRA & 1PhD ->1PDRA & 3PhDs. (1PDRA on multi-level and multi-3 phase modular converters and PWMs, 1PhD on open-winding machine control) • PhD: Luke Cowling (1/10/2017) – SiCconverter • Development of simulation models for SiC devices switching behaviour • Development of average loss and thermal models of SiC devices • Simulation of various converter topologies  • Efficiency evaluation and comparative analyses of various converter topologies incorporating Si & SiCdevices • Testing of SiC devices to validate thermal and switching models • Investigation into current source converter topologies using SiC devices • Comparison of CSC & VSC converter topologies using Si & SiCdevice • PhD: Jin Xu (1/10/2017) –Control of multi-3-phase converters • Mathematical modelling of dual-three phase machines with different angle displacements • System simulation including both grid and generator sides • Experimental validation of harmonic mitigation using PIR & vector space decomposition • Theoretical and experimental investigation of influence of cogging torque on initial position – a paper drafted • PWM generation strategies to reduce THD and CMV • Parallel converter control strategies to reduce CMV on the generator side WP1.2. Development of novel modular multi-3-phase converters and control strategies

11. 1PDRA & 1PhD ->1PDRA & 3PhDs. (1PDRA on multi-level and multi-3 phase modular converters and PWMs, 1PhD on open-winding machine control) • PhD: SumeetSingh Thakur (1/2/2018) – Novel ac/ac converter • Literature survey completed o   Medium voltage converter for wind turbines o   Modular Multilevel Converter (MMC) topologies for wind turbines o   Detailed literature review of modular multilevel matrix converter • Simulation and understanding of dc to 3-ph ac MMC and 1-ph to 3-ph ac/ac MMC. • Simulation of 3-phase to 3-phase Modular Multilevel Matrix Converter (M3C) with voltage balancing o   Simulation of M3C with grid connection and RL-load o   Simulation of M3C with grid connection and variable frequency generator (sub-scale) • Build and test a H-bridge module • RA: Tao Wang (1/7/2018) – Predictive control • PhD viva in June WP1.2. Development of novel modular multi-3-phase converters and control strategies

12. Lead Partner: DU/Dong, Co-Partner: UoS(EMD); Resource: 1 PhD • Contact: Dr Christopher Crabtree, "CRABTREE C.J." c.j.crabtree@durham.ac.uk • PhD studentship for this work package is being advertised and will be in place from October 2018 WP1.3. Robust power converter design for large scale wind turbine application

13. WP1.4. Parasitic effect and sensitivity studies, including noise and vibration, bearing current and manufacturing tolerances, rotor eccentricities etc. 1PDRA & 2PhDs. (1PDRA on bearing current, 1PhD on tolerance etc, 1PhD on noise) PhD: Jaime Maravi (1/10/2015) – Noise and vibration • Mechanical 3D models of a 3kW 48s52p generator • Modal testing of several structures to validate mechanical models- Aluminium cylinder/ 28-pole rotor/3kW 48s52p generator • Study of the effect of discretizing the force integration path (one pole pitch, half a pole pitch, quarter of a pole pitch) on the vibration response • Investigation of vibration behaviour of external rotor PM generator PhD: Yi Wei (1/10/2017) – Bearing current, common mode voltage • Completed literature review and report • Investigation and simulink implementation of high-frequency lumped induction machine modelling • Investigation of parameters determination methods, including vector fitting  • Familiarising with finite-element tools Implementation of high-frequency distributed parameters machine modelling Estimation of high-frequency parameters analytically and experimentally RA: LirenHuang (1/5/2018) – Manufacturing tolerances & rotor eccentricities

14. 2PhDs. (1PhD on self-sensing at zero/low speed for SPM generator, 1PhD on self-sensing under unbalanced or fault condition) • PhD: XimengWu (1/10/2016) - Self-sensing at zero/low speed for SPM generator • Investigation of rotor initial position detection for a reliable starting • Proposed a new effective method for rotor initial position detection • Experimental validation of the proposed method • Making improvements on the proposed method • 1 paper drafted • Combining proposed initial position detection method and current model based sensorless control technique • Starting performance investigation • PhD: TianyiLiu (1/12/2017) - Self-sensing under unbalanced or fault condition • Literature review report & presentation completed • Conventional fundamental model based sensorless methods validation • Inductance unbalance and variation analysis • Abnormal conditions analysis (parameter unbalance & harmonics, etc) for fundamental model sensorless methods. • Abnormal conditions analysis for high frequency injection methods. WP1.5. Novel self-sensing control techniques for new modular generators

15. All PhDs & RAs. • PhD: Ximeng Wu - self-sensing at zero/low speed for SPM generator • Implemented on dSPACE • Initial position experimentally investigated • PhD: YanxinLi (1/10/2014-30/12/2017) – Modular PM generators • 3kW PM generator prototyped and all findings experimentally validated • PhD: Jin Xu • Experimental investigation of influence of cogging torque on initial position • Others to be carried out WP1.6. Validation of developed generators, converters and control strategies on scaled prototype systems

16. Lead Partner: UoS(EMD)/SWP, Co-Partner: DU; Resource: 2PhDs. (1PhD on fault analysis and condition monitoring, 1PhD on health and lifetime prognosis) • PhD: Jin Xu (1/10/2017) – Control of multi-3-phase converters with asymmetries and faults • Mathematical modelling of dual-three phase machines with different angle displacements • PhD: TianyiLiu (1/12/2017) - Self-sensing under unbalanced or fault condition • Literature review report & presentation completed • Inductance unbalance and variation analysis • Abnormal conditions analysis (parameter unbalance & harmonics, etc) for fundamental model sensorless methods. • Abnormal conditions analysis for high frequency injection methods. WP3.5. Generator and converter fault analyses, including open- and short-circuits, and health and condition monitoring

17. Management Meeting Progress ReportMB2 - 10 May 2018 EPSRC Prosperity Partnership A New Partnership in Offshore Wind EP/R004900/1

18. Performance comparison between conventional and vernier PM machines Analytical modelling of vernier PM machines Torque/power density improvement of vernier PM machines Power factor improvement of vernier PM machines Minimisationof system cost Scalability study • EPSRC PP - PhD Outlines – 2017 Entry WP1.1. Development and design optimisation of novel modular balanced multi-3-phase direct-drive PM generatorsInvestigation on Novel Vernier PM Machines for Wind Power Application Permanent magnet generators offer the highest efficiency and torque/power density, which in turn can reduce the cost of installation etc. For most industrial drives, the cost of inverter/converter with current silicon technologies may be higher than that of the machine. However, this may not be true in the direct-drive (DD) permanent magnet (PM) generator technologies, as due to the low speed, the generator size is large and its cost may be higher than the converter. Therefore, there is a requirement to further investigate high-torque, but low power factor, machine technologies such as transverse flux PM machines and Vernier PM machines. This project will focus on Vernier PM machines for wind power application. Alternative Vernier PM generator technologies will be compared with reference to conventional PM generators, in terms of power factor, power capability, power density, losses and efficiency, reliability, fault tolerance, etc., with the aim to identify the most appropriate generator topology to minimise the overall system cost. The study will make use of finite element and analytical techniques to investigate the influence of key design parameters specific to the developed topologies. Design optimization including multi-physics modeling techniques will be undertaken to maximise the electromagnetic, thermal and mechanical performance of the selected generator topologies.

19. Performance comparison between conventional and Transverse Flux PM machines Lumped circuit modelling of Transverse Flux PM Machines Torque/Power Density Improvement of Transverse Flux PM Machines Power Factor Improvement of Transverse Flux Permanent Magnet Machines Minimisationof System Cost Scalability Study • EPSRC PP - PhD Outlines – 2017 Entry WP1.1. Development and design optimisation of novel modular balanced multi-3-phase direct-drive PM generatorsInvestigation on Novel Transverse Flux Permanent Magnet Machines for Wind Power Application Permanent magnet generators offer the highest efficiency and torque/power density, which in turn can reduce the cost of installation etc. For most industrial drives, the cost of inverter/converter with current silicon technologies may be higher than that of the machine. However, this may not be true in the direct-drive (DD) permanent magnet (PM) generator technologies, as due to the low speed, the generator size is large and its cost may be higher than the converter. Therefore, there is a requirement to further investigate high-torque, but low power factor, machine technologies such as transverse flux PM machines and Vernier PM machines. This project will focus on Transverese Flux PM (TFPM) machines for wind power application. Alternative TFPM generator technologies will be compared with reference to conventional PM generators, in terms of power factor, power capability, power density, losses and efficiency, reliability, fault tolerance, etc., with the aim to identify the most appropriate generator topology to minimise the overall system cost. The study will make use of finite element and analytical techniques to investigate the influence of key design parameters specific to the developed topologies. Design optimization including multi-physics modeling techniques will be undertaken to maximise the electromagnetic, thermal and mechanical performance of the selected generator topologies. .

20. Review of current generator energy conversion systems. Analysis of benefit SiC converter in wind energy conversion Electro-thermal interaction and reliability modelling Optimal system design Prototyping and validation • EPSRC PP - PhD Outlines – 2017 Entry WP1.2. Development of novel modular multi-3-phase converters and control strategiesOptimal design of SiC-based converter for wind power application The majority of current wind turbine converters use 690V two-level converters based on (1.7kV) Si-IGBTs with a typical efficiency of approx. 96% at 3kHz switching frequency. Recent advances in semiconductor manufacturing have made SiC devices commercially available. Despite their benefits in terms of lower losses, higher efficiency, lower sensitivity to temperature, SiC have not gained significant market penetration in cost-sensitive applications. Although currently more expensive than their Si counterpart, it is expected that in the near future, wider availability from a number of suppliers will make them cost competitive with Si-based solutions. The benefits of SiC-based converters are well understood for high-performance high-speed drives e.g. in traction applications. Relatively less clear is the benefit to low voltage, low frequency and cost sensitive applications, such as those in the current wind generation industry. “SiC converters can improve the wind system power conversion efficiency and can reduce the system’s size and cost due to the low-loss, high-frequency, and high-temperature properties of SiC devices, possibly even for one-for-one replacement for Si devices.”

21. Development of control strategies for multiphase and multi-3-phase pm generators with different phase shifts Investigation of PWM strategies for multiphase and multi-3-phase pm generators with different phase shifts Optimal PWM strategies for parallel switching in single and multiphase large direct-drive turbines Comparative study of multiphase and multi-3-phase pm generators • EPSRC PP - PhD Outlines – 2017 Entry WP1.2. Development of novel modular multi-3-phase converters and control strategies Control strategy investigation of multi-3-Phase PM wind power generators considering different phase shifts and asymmetries This project is to develop control strategies and power electronic drives for multi-3-phase PM wind power generators considering different phase shifts and asymmetries. A comparative study of multi-3-phase and parallel 3-phase converters for generators will be carried out. The study will aim to identify the most promising technologies for further detailed study, including those most suitable for high power, low switching frequency operation, with particular focus on low harmonic distortion, low losses, and high efficiency, as well as low acoustic noise and EMC, etc. The investigation will also include pulse-width-modulation (PWM) and control strategies, featuring high performance and high efficiency.

22. Propose control/modulation approaches to achieve a constant-magnitude constant-frequency output voltage (i.e. grid voltage) under a variable-magnitude variable-frequency ac voltage of the generator. • Compare the proposed ac/ac topology (i.e. performance, efficiency and cost) with respect to the conventional two-level two-stage ac-dc-ac Si device based power converter. • Explore advantages of FBMMC modularity and in that reconfigurability and fault ride through capabilities. • Compare the proposed ac/ac topology (i.e. performance, efficiency and cost) with respect to the emerging two-level SiC device based power converter. • Explore the applicability of SiC power devices in the proposed MMC topology. • Include full-scale real-time virtual prototyping using OPAL-RT and small-scale experimental validation. • EPSRC PP - PhD Outlines – 2017 Entry WP1.2. Development of novel modular multi-3-phase converters and control strategiesAn ac/ac power converter for direct-drive PMSG based wind energy systems The project is in the area of modular power electronic converters for integration of offshore wind turbines to the medium voltage grid. It will explore challenges of interfacing a permanent magnet synchronous generator (PMSG) wind turbine to the grid through a double-star modular multilevel converter based on full bridge cells (FBMMC). In particular, the focus will be set on direct ac-to-ac power conversion topologies based on a FBMMC. In this configuration, a power electronic converter is required to convert a variable-magnitude variable-frequency ac voltage of the generator to a constant magnitude constant-frequency grid voltage. The performance of the proposed topology will be analysed with respect to the conventional two-level two-stage ac-dc-ac Si device based power converter. It will explore advantages of FBMMC modularity and in that reconfigurability and fault ride through capabilities. The comparative studies will also be done with respect to a two-level SiC device based power converter topology. Further, the applicability of SiC power devices in the proposed MMC topology will be investigated. The study will include full-scale real-time virtual prototyping using OPAL-RT and small-scale experimental validation..

23. Investigation of high-frequency models of machine Modelling of common-mode Voltage, CM impedance and currents Investigation of alternative modulation strategies for reduced CM voltage. Experimental Validation • EPSRC PP - PhD Outlines – 2017 Entry WP1.4. Parasitic effect and sensitivity studies, including noise and vibration, bearing current and manufacturing tolerances, rotor eccentricities etc.Modelling of high frequency behaviour of machine insulation, common-mode currents & mitigation strategies High-frequency modelling of machine can provide a tool to understand the voltage distribution and the associated stress on different regions of the insulation system (e.g. turn-to-turn / turn-to-ground). Although insulation degradation in low-voltage machines is mostly thermally activated, i.e. LV machines are unlikely to suffer from partial discharge, this might not be the case when fast rise-times (high dv/dt) are generated by fast-switching devices. Therefore, understanding voltage stress is important in the context of quantifying benefits and drawbacks of potential alternative designs e.g. MV or the use of SiC switches. A second aspect of the high-freq. modelling is related to the common mode currents resulting from standard modulation schemes in two-level converters. CM currents are known to be a cause of bearing lifetime reduction. The monitoring of common-mode impedance has also been demonstrated to be an indicator for diagnostic and prognostic of insulation state of health.

24. High speed and low speed sensorless control strategies for pm generators with generator asymmetries Sensorlesscontrol strategies for PM generators with inverter faults Dual 3-phase sensorless control strategies for pm generators with generator asymmetries and/or inverter faults • EPSRC PP - PhD Outlines – 2017 Entry WP1.5. Novel self-sensing control techniques for new modular generatorsFault-tolerant Sensorless Control of PM Wind Power Generators Under Generator Asymmetries and Inverter Faults There is an increasing requirement to reduce the cost of energy production, e.g. for wind energy production. The major aspects include smarter and larger reliable wind power generation systems. Due to their large size, the wind power generators are usually sensorless controlled. However, their large size also means they are manufactured from segments and consequently with inherent asymmetries. The conventional sensorless techniques which assume perfect symmetry may introduce significant errors, which will degrade the output performance and energy production efficiency. Further, during fault conditions, the conventional sensorless techniques will not perform reliably and may cause further unexpected deviations in performance. It is therefore important to develop novel fault-tolerant sensorless techniques for wind power applications. This project will develop novel sensorless techniques for wind power generators which exhibit manufacturing and operating asymmetries, as well as faults such as open-circuits and short-circuits. A dSPACEplatform will be used for both simulation and testing, with experimental validation performed on an existing 3kW prototype.