DSP implementation of output voltage reconstruction in CSI based UPS systems

Current source inverter-based uninterruptible power supplies (UPS) require sensing of two or more output voltages and synchronization with the AC input voltage in addition to the DC voltage sensors used for protection purposes. This paper proposes a DSP-based space vector control scheme that requires only information provided by the DC bus sensors. Output voltage estimation is based on AC line voltage reconstruction by means of information available on the DC bus and knowledge of the PWM pattern. In addition to providing low output voltage harmonic distortion, the system minimizes the component count and therefore increases ruggedness. The paper presents the DSP algorithms required for the operation of the system, and experimental results on a 208 V, 60 Hz, 5 kVA prototype inverter