All Electrical Drive Train for Marine Energy Converters (EDRIVE-MEC)

EDRIVE-MEC：船舶能源转换器的全电驱动系统理想地通过PTO和动力调节系统将波浪能转换为电能，该系统可以在多个方向上转换运动，在低速、可变电压和频率下运行时对大的力或扭矩做出反应，在各种负载下具有高可靠性、可用性和效率。这一苛刻规范的所有方面都直接影响到能源的寿命成本，从而影响到设备的经济可行性。目前，没有一种已被证明的PTO技术能够满足波浪能的这一规格。波浪装置中使用的PTO有两种主要选择：液压和直接驱动。波浪设备开发人员一直专注于使用液压作为PTO，无论是高压油还是水（Pelamis，Aquamarine）。在与我们的工业合作伙伴的讨论中，我们了解到使用液压系统的唯一原因是由于其现成可用，但所有合作伙伴都担心其局限性，包括部分负载下的低效率;在广泛频率范围内的控制能力;以及导致潜在终端停止问题的位移。液压的替代方案是直接驱动，其中机械接口被消除，但现在发电机必须以低速和高力运行。直接驱动系统已经通过达勒姆和爱丁堡的实验室测试，以及瑞典乌普萨拉、阿基米德波浪摇摆和俄勒冈州州立大学的海上试验得到了证明。在这些情况中的每一种情况下，使用永磁同步电机，并且发电机具有线性平面或管状拓扑结构。能量只能从装置在一个方向上的运动中取出，主要是升沉，而装置会纵荡和纵摇以及升沉。使用当前形式的线性发电机限制了直接驱动动力输出系统的功能，因为它不允许从多于一个运动转换能量。还没有考虑到速度增强技术，例如在谢菲尔德为旋转机械开发的磁性齿轮箱，或者使用通过控制内部产生的弹簧，或者使用外部物理弹簧，例如空气弹簧。速度的提高使得机器设计更加优化，从而减小了物理尺寸并提高了效率。以前在直接驱动动力输出方面的工作已经证明了这个概念是可行的，但是解决方案并没有完全优化，设计的可靠性或与波浪装置的特性相匹配。与发电机一样，开发人员已经证明了将直接驱动系统连接到电网的概念，但使用传统的功率转换器方法。然而，众所周知，风力行业中的功率转换器存在可靠性问题，并且在潮汐领域，开发人员使用陆上功率转换器以便于访问。功率转换器内的故障的主要原因是由于风和波浪的可变性质引起的连续热循环。因此，有机会研究替代电源转换器解决方案，例如多电平系统，其中功率器件上的应力现在由多个器件分担。该项目的主要目标是在与我们的工业合作伙伴的讨论中制定的：开发一种集成的电力输出系统，该系统具有非机械速度增强，集成和可靠的灵活电力电子设备，在一系列操作制度下提供自适应控制，考虑到标称和极端负载条件。E-DRIVE建议通过开发具有速度增强功能的新型集成低速发电机和具有相关控制的功率转换器拓扑来实现这一目标，以取代液压系统。在此过程中，我们将反映汽车和航空航天领域所有/更多电气系统的发展。

EDRIVE-MEC: All Electric Drive Train for Marine Energy ConvertersConversion of energy from wave into electricity is ideally performed by a PTO and power conditioning system that can convert motion in multiple directions, react large forces or torques whilst operating at low velocity, variable voltage and frequency, with high reliability, availability and efficiency over a wide range of loads. All aspects of this demanding specification contribute directly to the Life Time Cost of Energy and hence economic feasibility of devices. At present no single PTO technology that has been demonstrated is able to meet this specification for wave energy. The two main options for the PTO used in a wave device: hydraulics and direct drive. Wave device developers have focussed on using hydraulics as the PTO, whether it be high pressure oil or water (Pelamis, Aquamarine). In discussions with our industrial partners we learnt that the only reason for using hydraulics was due its availability off the shelf, but all partners were concerned about the limitations including, low efficiency at part load; ability to control over a wide range of frequencies; and displacement leading to potential end-stop problems. The alternative to hydraulics is direct drive, in which the mechanical interface is eliminated, but now the generator has to operate at low velocity and high force. Direct drive systems have been proven through lab tests at Durham and Edinburgh, and through sea trials by Uppsala in Sweden, Archimedes Wave Swing and Oregon State University. In each of these cases a permanent magnet synchronous machine has been used and the generator has been of a linear planar or tubular topology. Energy can only be taken out of the device from motion in one direction, principally heave, whereas devices surge and pitch as well as heave. The use of linear generators in their current form has constrained the functionality of direct drive power take off systems, as it has not allowed energy to be converted from more than one motion. No consideration has been given to speed enhancing techniques, such as magnetic gear boxes, as developed at Sheffield for rotary machines, or the use of springs, either internally produced through control, or external physical springs, such as air springs. Speed enhancing allows a more optimised machine design, resulting in a reduction in physical size and an increase in efficiency. Previous work in direct drive power take off has proved the concept will work, but solutions are not fully optimised, designed for reliability or matched to the characteristics of the wave device. As with the generator, developers have proved the concept of connecting direct drive systems to the grid, but making use of conventional power converter approaches. However, it is well known that there is a reliability issue with power converters in the wind industry, and in the tidal sector developers use an onshore power converter for easy access. The main cause of faults within the power converter is the continuous thermal cycling due to the variable nature of wind and wave. There is therefore an opportunity to investigate alternative power converter solutions, such as multi-level systems, where the stress on the power devices are now shared across a number of devices. The main aim of the project has been formulated in discussions with our industrial partners: develop an integrated electrical power take off system with non-mechanical speed enhancement, integrated and reliable flexible power electronics, providing adaptive control over a range of operating regimes, taking into account nominal and extreme load conditions. E-DRIVE proposes to fulfil this aim through the development of novel integrated low speed generators with speed enhancement and power converter topologies with associated control to replace hydraulic systems. In doing so we will mirror developments in all/more electric systems in automotive and aerospace.