中文摘要：

四象限级联型变频器功率单元 H 桥的瞬时输出功率以2倍和4倍频率脉动，使得直流母线产生2次和4次纹波电压。单个功率单元输入端PWM整流器采用前馈控制策略能有效抑制母线电压波动，且总的并网电流无低次谐波。从功率单元的数学模型出发，推导出输入输出的瞬时有功功率，提出了基于瞬时 abc 理论的瞬时有功电流前馈控制来抑制直流母线电压波动，同时建立了基于Kalman滤波的负载电流估计模型。最后通过功率单元实验测试，验证了控制策略的可行性。

英文摘要：

The instantaneous output power of the power cell H-bridge in four-quadrant cascade converter pulsates at twice and quadruple the output frequency, generating the second and fourth harmonic DC bus voltage. Using feed-forward control scheme in PWM rectifier of single power cell can effectively restrain DC bus voltage ripple and make the total grid-connected current without low-order harmonics. From the mathematical model of power cell, the instantaneous active power is derived. Based on instantaneous abc theory, instantaneous active current feed-forward control have been proposed to restrain the DC bus voltage ripple. Moreover, load current estimation model based on Kalman theory is established. Finally, the experimental results are given to prove the effectiveness of the proposed control scheme.