| Nowadays the Flexible AC Transmission System (FACTS) is one of the advanced technology in electric power engineering and the Unified Power Flow Controller (UPFC), a versatile device in FACTS family, can control the load flow of transmission line and the bus voltage rapidly and flexibly .The thesis aims at the study of UPFC and some thorough analysis and study is conducted to the modeling running mechanism, restraining the harmonics of UPFC. At the same time, in order to decrease the harmonics of the SPWM voltage wave and to improve the quality of voltage wave, an improved equal area algorithm to boost SPWM wave has been proved. We also study the application of this algorithm in UPFC by DSP. The main achievements of this treatise are as follows: An improved equal area algorithm is proved by analyzed the intrinsic methods based on the SPWM .In the improved equal area algorithm, the geometry center of sampling period is regarded as the rectangular pulse center of SPWM wave and the harmonics analyses of the algorithm have been done .The analyses results show that the harmonics of this algorithm is decreased obviously and the quality of wave is improved obviously. Utilizing its highly speed operational capability in TMS320F240 DSP chip, we put forward the new hardware mode to eliminate the harmonic wave of inverter in real time. Testing the new hardware method DSP-based in laboratory, the emulation conclusion shows that the control using the new hardware mode can improve the accuracy of the invert output and ideal voltage wave can be output.The new hardware method DSP-based possess characteristics as follows: the fabric of this device is simple and its arithmetic is prone to realize. Accordingly, the output voltage of UPFC in the hardware device is consecutive and regulative and its control system in UPFC suffices real time control request. This device reduces harmonics content of output voltage in circuit and establishes foundation to improve performance of UPFC. |
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