Study On The Digital Inverter Of The Large Power UPS

With the fast development of information technology, digital CVCF-PWM inverters become possible. The performance of the on-line UPS is the best among all kinds of UPS, and it is widely used in many fields. Three-phase inverter of large power on-line UPS, which is widely used in industry, civil and military and so on, is over-all studied in this dissertation. This inverter not only can provide the steady and pure sine wave power with little distortion, but also can solve the unbalanced load. This dissertation chiefly introduces the analysis of this inverter power and the design of hardware and software of this UPS, and the core control chip is TMS320F240 which is produced by TI corp. First of all, the developing state of UPS, the advantage of the DSP technology applied in the UPS, the characteristics of modern invert technology SPWM waveform's control technology are summarized. Based on the circuit structure of three-phase bridge-type inverter applied in the inverter power, the state-space model of different coordinates of the inverter system are analyzed and established. And the effect of the dead time on the fundamental wave is also discussed, and the corresponding software compensation method is presented to solve this problem. Secondly, to control the inverter in UPS, several kinds of repetitive control schemes are discussed step by step, and finally the plug-in repetitive control with the proportional control is proposed and to be applied in the inverter system. Then, the operating principle of on-line UPS is introduced, and the hardware implementation block diagram of the inverter system is provided. Furthermore, the dissertation analyzes and designs the power circuit and the control circuit in details, which is based on TMS320F240 and SA4828 that can provide SPWM waveform and including phase-locked circuit, detection circuit of voltage and correlative circuit and so on. The software design of the inverter system is described. The sequence, the interruption and some important flowcharts are analyzed and their block diagrams are provided in details. At the end of the dissertation, the experiment results of the system are provided. And the results show that the proposed control scheme is valid and can meet the demand of UPS.