Admittance Compensation in Current Loop Control for a Grid-Tie LCL Fuel Cell Inverter

• Published in: IEEE transactions on power electronics Vol. 23; no. 4; pp. 1716 - 1723
• Main Authors: PARK, Sung-Yeul, CHEN, Chien-Liang, LAI, Jih-Sheng, MOON, Seung-Ryul
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.07.2008; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Admittance; Admittance compensation; Applied sciences; Circuit stability; Circuits; Commands; Compensation; Control systems; Design engineering; Direct energy conversion and energy accumulation; Electric power; Electrical engineering. Electrical power engineering; Electrical impedance; Electrical machines; Electrical power engineering; Electricity; Electrochemical conversion: primary and secondary batteries, fuel cells; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics; Electronics; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Filters; Frequency; Fuel cells; fuel-cell power conditioning system; Inverters; LCL filter; proportional-resonant compensator; Prototypes; Regulation and control; Simulation; single-phase grid-tie inverter; Testing; Transfer functions; Virtual prototyping; Stability margin; Prototype; Admittance compensation; Control synthesis; Load flow; proportional-resonant compensator; Power flow; fuel-cell power conditioning system; Transfer function; Fuel cell; Fundamental frequency; Inverter; LCL filter; Power circuit; Connection; Frequency domain method; Power electronics; Phase reversal; Experimental study; Failures; Steady state; Phase shifter; Current control; single-phase grid-tie inverter; Time domain method; System simulation; Gain
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2008.924828

Current loop transfer function of a single-phase grid-tie inverter has been systematically derived with representations of conventional transfer function format using admittance terms for controller design and loop compensation. The power circuit adopts the LCL type filter to allow universal output that can be operated in both standalone and grid-tie modes. The proposed admittance compensation along with a quasi-proportional-resonant controller is designed to achieve high gain at the fundamental frequency while maintaining enough stability margins. The entire current loop controller and admittance compensation have been simulated and tested with a 5-kW fuel cell prototype. Without the admittance path compensation, simulation results indicate that the system cannot start up smoothly and the zero current command cannot be tracked very well. At first simulation cycle, the power flow erratically fed back to the inverter that may cause catastrophe failure. With admittance path compensation, the time-domain current steady-state error can be easily reduced with the loop gain design in frequency-domain. Simulation and experimental results show that the inverter is capable of both standalone and grid-tie connection mode operations and smooth power flow control even with zero current command.