Combination Voltage-Controlled and Current Controlled PWM Inverters for UPS Parallel Operation

Jiann Fuh Chen, Ching Lung Chu

Research output: Contribution to journalArticlepeer-review

318 Citations (Scopus)


In this paper the scheme of combination Voltage Controlled and Current Controlled PWM inverters for parallel operation of 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 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.

Original languageEnglish
Pages (from-to)547-558
Number of pages12
JournalIEEE Transactions on Power Electronics
Issue number5
Publication statusPublished - 1995 Sept

All Science Journal Classification (ASJC) codes

  • Electrical and Electronic Engineering


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