Title :
Combination voltage-controlled and current-controlled PWM inverters for UPS parallel operation
Author :
Chen, Jiann-Fuh ; Chu, Ching-Lung
Author_Institution :
Dept. of Electr. Eng., Nat. Cheng Kung Univ., Tainan, Taiwan
fDate :
9/1/1995 12:00:00 AM
Abstract :
In this paper, a scheme of combination of voltage-controlled and current-controlled PWM inverters for parallel operation of a single-phase uninterruptible power supply (UPS) is proposed. The voltage-controlled PWM inverter (VCPI) unit as a master is developed to keep a constant sinusoidal wave output voltage. The current-controlled PWM inverter (CCPI) units are operated as slave controlled to track the distributive current. The power distribution center (PDC) performs the function of distributing the output current of each active unit. In this proposed scheme of parallel operation, each of the units can be designed as nearly independent, and the CCPI units do not need a PLL circuit for synchronization. As a result, the parallel operation of UPS is easy to implement and to expand system capacity. For the purpose of illustration, the system, including three single-phase units which operate in parallel, is analyzed and experimental results are given
Keywords :
PWM invertors; circuit testing; control system analysis; control system synthesis; electric current control; equivalent circuits; network analysis; network synthesis; uninterruptible power supplies; voltage control; UPS parallel operation; constant sinusoidal wave output voltage; current-controlled PWM inverters; distributive current tracking; power distribution center; single-phase uninterruptible power supply; synchronization; voltage-controlled PWM inverters; Circuits; Frequency synchronization; Master-slave; Phase locked loops; Power distribution; Power generation; Power supplies; Pulse width modulation inverters; Uninterruptible power systems; Voltage control;
Journal_Title :
Power Electronics, IEEE Transactions on