Development of new power decoupling and pulse energy modulation technologies for single-phase distributed generation inverters

利用可再生能源的分布式发电系统正日益渗透到主流电力系统中。许多小型分布式发电系统连接到单相电网。这些小型DG系统（光伏、风力系统等）都需要单相并网逆变器。对于单相系统，从分布式能源（光伏、风能）获取的所需恒定功率与向单相电网提供的所需脉动瞬时功率之间存在不匹配。提供恒源功率与脉动电网瞬时功率之差的机制称为“功率解耦”。为了用寿命与DG系统相当的薄膜电容器取代传统的大型且不可靠的电解电容器，需要创新的功率去耦技术。本计画提出利用小型薄膜电容器和有源半导体元件，开发一种新的功率去耦拓扑，并提出一种新的调制概念，称为“脉冲能量调制（PEM）”，用于单相并网逆变器。该技术的发展将导致逆变器直流环节中传统的大型电解电容器被功率半导体器件主动控制的小型薄膜电容器取代，并导致先进的脉冲调制方法，提高逆变器对直流电压变化和电网谐波的抗扰性。这将提高单相并网DG逆变器的可靠性和电能质量。该项目将有四个任务：(1)开发新型逆变器的功率解耦理论和工作原理；(2)开发桥式逆变器的PEM算法；(3)逆变器拓扑和PEM控制的验证；(4)逆变器拓扑和PEM控制的性能评估。在项目的后期阶段，将利用申请专利和技术转让的机会。该项目将为两名博士生和一名博士后提供实践培训。

Distributed generation (DG) systems using renewable energy are increasingly penetrating into mainstream power systems. Many small distributed generation systems are connected to single-phase grids. These small DG systems (PV, wind systems etc.) all require single-phase grid-connected inverters. For single-phase systems, there is a mismatch between the desired constant power drawn from distributed energy resources (PV, wind), and the required pulsating instantaneous power feeding to the single-phase grid. The mechanism which provides the difference between the constant source power and the pulsating grid instantaneous power is referred to as “power decoupling”. Innovative power decoupling technologies are needed to replace traditional large and unreliable electrolytic capacitors with film capacitors with a comparable life-span with DG systems. This project proposes to develop a new power decoupling topology using small film capacitors and active semiconductor devices, and to advance a new modulation concept called “pulse energy modulation (PEM)” for single-phase grid-connected inverters. The developed technologies will lead to the replacement of traditional large electrolytic capacitors in inverter dc link with small film capacitors actively controlled by power semiconductor devices, and lead to advanced pulse modulation methodologies for inverters with enhanced immunity to dc voltage variations and grid harmonics. This will result in increased reliability and enhanced power quality of single-phase grid-connected DG inverters. The project will have four tasks: (1) Develop Power Decoupling Theory and Operating Principles for the New Inverter; (2) Develop PEM Algorithm for Bridge Inverters; (3) Verification of the Proposed Inverter Topology and PEM Control; and (4) Performance Evaluation of the Proposed Inverter Topology and PEM Control. Opportunities for patent filing and technology transfer will be exploited at the latter stage of the project. The project will provide hands on training for two PhD students and one postdoctoral fellow (PDF).