HIGH POWER DENSITY MODULAR ELECTRIC POWER SYSTEM FOR AEROSPACE APPLICATIONS

摘要

As battery technology has matured, the overwhelming focus has been on increasing energy density while power density remains a primary driver for various niche markets. Flight control surfaces (including aircraft and launch vehicle actuation systems) are a primary example of an application that requires high power density energy storage that could benefit from increased capability. Traditionally these power dense applications have used hydraulics to supply actuation systems but the focus on modernizing to more electric solutions is increasing in order to realize the integration and life cycle cost benefits. The advents of Electro-Mechanical Actuators (EMA) and Electro-Hydrostatic Actuators (EHA) have driven the need to supply electrical power. Due to the unique situations in which these products are used in applications such as flight control actuation systems (FCAS), the duty cycles require both significant power dense maneuvers while maintaining adequate mission energy density. To satisfy the power density need, the common battery oriented approach would be to place multiple strings of batteries in parallel or incur the cost of significantly more expensive power dense batteries. Recently Moog Inc. has developed and filed a patent for a Modular Electric Power System (MEPS™) that satisfies the power dense need of many aerospace applications in a less expensive and lower weight package. The MEPS modular approach allows for an optimized base package that can be used as a scalable building block that is extensible to multiple applications, all with reduced non-recurring costs. This novel solution for increasing the power density of a secondary cell pack is achieved by supplementing several parallel strings of batteries with ultra-capacitors. The ultra-capacitors offer several advantages for the high power density aerospace application because of the large instantaneous discharge capability, high cycle life, fast recharge capability and low cost. The large peak current discharge capability of ultra-capacitors allows the system to attain peak required system performance without oversizing for energy; thus saving weight. Supplementing parallel strings of batteries with ultra-capacitors also increases the life of the batteries. The ultra-capacitor decreases the rate of current discharge from the battery; this increases life while also allowing relaxed requirements on the battery portion. The MEPS offers a unique ability to capture regenerative current; which is a large concern and impediment for implementing battery systems in aerospace motion control systems. This system has the advantage of being a stand-alone energy storage system from the vehicle power bus (if there is one) or being connected to the vehicle power bus and decreasing the power generation/delivery requirement. This flexibility is advantageous because it can provide high power to a motion control system where delivering such high power is taxing to the vehicle power system architecture. Specialized generator systems must be developed and supplied with fuel to account for the multiple FCAS on a vehicle, and they must be sized to meet the total peak power requirement. Putting these MEPS near the FCAS allows for the relaxation of vehicle bus peak power requirements or a stand-alone approach to powering the flight surface all together.