Plenary speakers: Power electronics for renewable energy and power systems: Opportunities and challenges

A major driver for the development of power electronics has been microelectronics and motor drive applications. The success and impact of this development can be seen today in the ubiquitous IT infrastructure which we depend upon for virtually every aspect of our life, and the millions of electric vehicles that will eventually displace vehicles based on internal combustion engines. From power system perspective, however, these applications are on the load side and their impacts on the system are not as prefund as power electronics that started to proliferate on the generation and transmission side in recent years due to the rapid development of renewable energy and high-voltage dc (HVDC) trans mission. Compared to electromechanical and electromagnetic energy conversion devices such as generators and transformers that use slow (or no) control and can endure large overvoltage and overcurrent for long time, power electronics employ much faster control but have very limited overloading capabilities. These two fundamental characteristics, determined by semiconductor physics, complement each other at the device and converter level, but each is in conflict with certain aspects of how today's power grid is designed and operated. Namely, fast control creates complex dynamics and resonance problems in the high frequency range that don't exist in traditional power systems, while the need to protect a converter itself can be very detrimental to system transient stability. This talk reviews the technology and application of power electronics in renewable energy generation and HVDC transmission systems, and discusses their impacts on grid stability. System modeling and analysis based on a new small-signal sequence impedance theory is also presented as an effective method for the analysis and mitigation of highfrequency resonance problems that have become a major challenge for the development and operation of HVDC and large-scale renewable energy systems in recent years.