Control Issues in Robust High-efficiency Energy Conversion with Application to Renewable Energy Systems

现代可再生能源系统(RES)在演变过程中面临两个主要挑战：(1)能够生产可靠和经济的能源的基础科学和技术；(2)可靠和最佳地将能源转化为可用形式的能源处理技术。尽管电子技术在过去的几十年里已经完善了，但它必须重新设计和调整，以适应新的挑战。为此，控制、通信和计算技术以及新的电力电子转换器和设备在现代可再生能源中将变得越来越重要。一个特别重要的领域是对间歇电源、负载和储能设备的稳定和稳健控制。特别是，开关功率转换器本质上是非线性的，受到严格的输入/状态限制，并受到各种不确定性的影响。现有的控制方法大多采用线性化的稳态模型，忽略了上述约束，或者不能用来设计间歇能源所需的鲁棒控制器。RES能量转换器的另一个共同特点是存在一个最优功率运行点，它依赖于可用的输入功率和负载条件。为了最大限度地利用这种转换器，功率处理阶段必须以更可靠和准确的方式自主跟踪最优点。此外，可再生能源系统往往具有固有的非线性特征，具有显著的参数和动态不确定性。因此，基于线性化的设计方法可能由于忽略了非线性效应而不能充分发挥反馈系统的优点。

Modern renewable energy systems (RES) face two main challenges in their evolution: (1) Fundamental sciences and technologies to produce reliable and economical energy sources; and (2) Energy processing technologies for reliable and optimal conversion of energy into usable forms. Although the electronics technology has been perfected in the past decades, it has to be redesigned and adapted to match new challenges. To this end, control, communication, and computing technologies, along with new power electronics converters and devices are expected to become increasingly important in modern RES. An area of particular importance is stable and robust control of intermittent power sources, loads, and energy storage devices. In particular, switching power converters are intrinsically nonlinear, subject to strict input/state constraints, and suffer from various uncertainties. Most existing control methods utilize linearized steady state models that neglect the above constraints or cannot be used to design robust controllers required by intermittent energy sources. Another common feature of RES energy converters is the existence of an optimal power operating point, which is dependable on the available input power and load conditions. To maximally utilize such converters, the power processing stage has to autonomously track the optimal point in a reliable and accurate manner. Furthermore, renewable energy systems often have inherently nonlinear characteristics with significant parametric and dynamic uncertainties. Hence, design methods based on linearization may fail to provide the full benefits of feedback systems due to neglecting nonlinear effects.