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

EDrive-MEC：用于船用能源转换器的全电动传动系统理想地将能量从波浪转换为电能是由PTO和电源调节系统实现的，该系统可以在低速、可变电压和频率下运行时转换多个方向的运动，对较大的力或扭矩做出反应，并且在各种负载下具有高可靠性、可用性和效率。这一要求苛刻的规格的所有方面都直接影响到能源的使用寿命成本，从而影响到设备的经济可行性。目前，已经证明的任何一种PTO技术都不能满足这一波能规格。波浪装置中使用的PTO有两个主要选项：液压和直接驱动。波浪设备开发商一直专注于使用液压作为PTO，无论是高压油还是水(Pelamis，海蓝宝石)。在与我们的工业合作伙伴的讨论中，我们了解到使用液压的唯一原因是其现成的货架，但所有合作伙伴都担心其局限性，包括部分负载效率低；能够控制广泛的频率范围；以及导致潜在的末端停止问题的位移。液压的替代方案是直接驱动，取消了机械接口，但现在发电机必须在低速和高力下运行。直接驱动系统已经在达勒姆和爱丁堡的实验室测试以及瑞典乌普萨拉、阿基米德波浪摆动和俄勒冈州立大学的海试中得到了验证。在每一种情况下，都使用了永磁同步电机，发电机是线性、平面或管状拓扑结构。能量只能从设备的一个方向运动中获取，主要是升力，而设备的喘振、俯仰和升力都是如此。目前形式的直线发电机的使用限制了直接驱动动力输出系统的功能，因为它不允许从一个以上的运动中转换能量。没有考虑提高速度的技术，如谢菲尔德为旋转机械开发的磁性齿轮箱，或者使用内部通过控制产生的弹簧，或外部物理弹簧，如空气弹簧。速度提升使机器设计更加优化，从而缩小了物理尺寸，提高了效率。之前在直接驱动动力输出方面的研究已经证明，这一概念是可行的，但解决方案并没有完全优化，没有针对可靠性进行设计，也没有与WAVE设备的特性相匹配。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，但使用了传统的电力转换器方法。然而，众所周知，风电行业的电力转换器存在可靠性问题，在潮汐行业，开发商使用陆上电力转换器以便于访问。功率转换器内部故障的主要原因是由于风浪变化的性质而导致的连续热循环。因此，有机会研究替代的电源转换器解决方案，例如多电平系统，在这种系统中，电源设备上的压力现在由多个设备分担。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，具有非机械式提速、集成和可靠的灵活电力电子设备，提供对一系列运行制度的自适应控制，并考虑到额定和极端负载条件。E-DRIVE计划通过开发新型集成低速发电机来实现这一目标，该发电机具有速度提高和带有相关控制的功率转换器拓扑结构，以取代液压系统。通过这样做，我们将反映汽车和航空航天领域所有/更多电子系统的发展。

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.