Design and Control of Interleaved T-type Inverter without Damping

Interleaved technique has the advantages of boosting power, canceling current ripple and improving the dynamic response. This paper investigates the design and control of an interleaved three-level T-type inverter with LCL filter without active or passive damping. Through proper design considering digital control delay, the LCL resonance frequency can be placed in self-stabilizing region, such as 1/6 to 1/2 times the sampling frequency. In self-stabilizing region, no damping is required to stabilize the closed-loop grid current. The interleaving ripple cancelation of interleaved T-type inverter is analyzed in detail to develop proper design of LCL filter. It is found that interleaving is easy to realize very small filter capacitance value so that the resonance frequency is increased, which is able to control the inverter working at high control bandwidth without damping. The effectiveness and performance of the proposed design and control are validated by a two-phase interleaved T-type inverter prototype.