A novel transformerless active voltage quality regulator

In order to solve Power quality problems such as voltage sag, low voltage and harmonics in power grid, a novel topology without transformer based on single-phase Vienna rectifier and three-level half-bridge is proposed. Compared with Dysc structure and H bridge structure, it solves the harmonic pollution problem on rectifier side, reduces the number of switching devices, Eliminates the problem of rectifier bridge arm straight-through, and reduces the complexity of control and cost of equipment. In the aspect of inverter control, The feedforward strategy of output voltage is applied, which eliminates the influence of load characteristics on control performance, and improves the system response speed and robustness of the system. At the same time, taking full advantage of the small modulation degree of the equipment, the method of instant refresh is adopted in the DSP, which eliminates the influence of control delay, greatly improves the open-loop gain of the system, improves the response speed, steady-state control effect and robustness of the system. The developed 10KA equipment verifies the correctness and effectiveness of the new topology and control method.