Power Quality Improvement of Smart Microgrids

智能微电网是将可再生能源（RESs）整合到公用电网并允许客户参与能源企业的有前途的解决方案。在不久的将来，智能微电网将为客户提供负担得起的电力，并将为依赖无排放能源铺平道路。智能微电网通常分为交流、直流和混合交流/直流，与传统电力系统相比，它们具有若干优势，例如，它们提供更高的可靠性、安全性和效率，允许通过分布式发电（DG）单元利用RESs，减少损失，并且有益于健康、气候和世界经济。尽管它们具有优势，但在有效设计和使用智能微电网方面存在一些技术挑战。一些主要的挑战是公用电网的电能质量（PQ）下降，以及由于RESs和负载变化的间歇性而引起的稳定性问题。此外，配电网中非线性和不平衡负荷的激增给智能微电网带来了许多PQ和稳定性问题。低PQ会给电网和用户带来许多问题，例如，电力损失、敏感设备故障、电力中断、负载性能差、安全问题，并产生巨大的成本。例如，EPRI-CEIDS进行的一项调查显示，由于各种PQ问题，北美经济每年损失超过240亿美元。

Smart microgrids are promising solutions to integrate renewable energy sources (RESs) into the utility grid and allow the customers to participate in the energy enterprise. In the near future, smart microgrids will contribute to affordable electricity for customers, and will pave the path to rely on an emission-free form of energy. Smart microgrids are usually categorized into ac, dc and hybrid ac/dc, and provide several advantages over conventional power systems, e.g., they provide increased reliability, security, efficiency, allow the exploitation of the RESs through distributed generation (DG) units, reduce losses, and are beneficial for health, the climate, and the world economy. Despite their advantages, there exist several technical challenges associated with the efficient design and use of smart microgrids. Some of the main challenges are power quality (PQ) degradation of the utility grid, and stability issues due to the intermittent nature of the RESs and load variations. Moreover, the proliferation of nonlinear and unbalanced loads in distribution networks results in a number of PQ and stability problems for smart microgrids. Poor PQ results in a multitude of problems for both utility grid and consumers, e.g., power losses, malfunction of sensitive equipment, power interruptions, poor performance of the loads, safety issues, and incur huge costs. For example, a survey conducted by EPRI-CEIDS shows that the North American economy loses more than 24 billion dollars per year due to various PQ problems. In this Discovery program, we aim to overcome some of the challenges associated with PQ and stability of ac and hybrid ac/dc microgrids. More specifically, in the proposed research, we will tackle the following tasks: • Proposing high performance robust decentralized controllers for PQ improvement of ac microgrids with electronically- and directly-coupled machine-based DG units, • Developing multifunctional control strategies for grid-connected converter-based DG units in order to compensate for non-integer harmonics, • Proposing robust controllers to improve robust stability and PQ of islanded hybrid ac/dc microgrids in the presence of uncertain nonlinear and/or unbalanced loads, and • Designing nonlinear robust controllers for the interlinking converters of a grid-connected hybrid ac/dc microgrid to guarantee voltage stability and improve PQ. The proposed Discovery program will contribute to the development of renewable energy and smart microgrids technologies. Moreover, through the proposed program, we will contribute to the training of HQP which are in high demand by Canadian industries and academia.