Research On Rectifier Technology For Vienna Converter

As the power electronics technology develops, especially for the rapid development of power semiconductor devices and control technology, the power electronic devices are increasingly used in the mining industry and plays an important role in improving the production efficiency as well as product quality, which has become an important foundation for the production of automated equipment.However,due to its strong nonlinear characteristics of a large number of harmonics and reactive power injected to the grid, which are resulted in serious grid "pollution".Therefore, the study of high power factor PWM rectifier device is a major research topic in the field of power electronics applications. In the three-phase rectifier topology, VIENNA rectifier, as a typical three-level topology,is suitable in areas of high-voltage and high-power condition. Compared with traditional two-level structure, it reduces the switch voltage stress and the AC side of the harmonic content; In comparison with the diode clamped three-level structure, only a switch is needed in each leg, avoiding the dangers of the upper and lower bridge arm and simplifying the control links to obtain a wide range of applications. Therefore, from the view of the economic and security considerations, the study of VIENNA rectifier control technology has a great engineering value.The VIENNA rectifier topology is analyzed in this paper, a detailed analysis of its theory in a power frequency cycle is introduced, by utilizing the state space averaging method, the mathematical model and its equivalent circuit are established in three coordinate system.On this basis, the voltage outer current inner double-loop control structure is established using the current decoupling feed forward control strategy. Then theoretical analysis is verified by simulation.For the inherent disadvantages of three-level circuit,an average neutral-point voltage balance control model is proposed based on the SPWM modulation and an averaging technique are used to derive the relationship between the controlled duty cycle and the dc-link neutral-point voltage. An optimal zero-sequence component is found for dc-link voltage balance by using the mathematical derivation. The mathematical relationship related with the the dc-link voltage unbalance and the controlled zero-sequence component is developed.Meanwhile, the neutral-point voltage control block is also given. And the neutral-point of the balance control block diagram is modeled in d-q coordinates. Simulation analysis validates the theoretical result. The proposed SPWM modulation algorithm based on the neutral-point balance control approach is simple and the dc-link neutral-point voltage is easy to regulate.Finally, the control unit and the main power platform are designed based on TMS320F2812. A software program is written in C language.Digital control scheme is achieved based on d-q coordinates, which meets the steady-state and dynamic performances.