Compared with the internal bracing systems of retaining for the deep foundation pit in the basement of certain mansion in Fuzhou,the advantages of retaining the construction of the foundation pit with the system of a double ring,a double layer and boring grout piles lie in its better stability,less displacement,larger site area and lower project cos t.

A double loop control method has been used,so the output current can accurately follow the programmable reference,and the flux imbalance is avoided.

A novel current feed-forward decoupled control algorithm was proposed,and the double loop control system was designed in detail based on this algorithm.

In order to obtain the grid current tracking and DC bus voltage stabilization, the double loop control is adopted by modulating the sinusoidal PWM; by modulating the Boost duty cycle, PV output voltage is controlled.