中文摘要：

在单相电力变换系统中,大容量电解电容常用于消除交流侧与直流侧瞬时功率不平衡所产生的直流侧二次纹波电流以及交流侧低次谐波引起的直流侧谐波电流。然而电解电容的使用会直接降低系统工作效率,缩短使用寿命,给单相电力变换系统带来不良影响。针对该问题,文中首先将直流侧谐波（由交流侧基波和谐波引起的直流侧谐波成分）抑制的本质归纳为脉动功率的减弱、转移和就地补偿,基于此分析提出将脉动功率控制在交流侧,通过控制交流侧串联交流电容瞬时功率直接就地补偿而不在直流侧补偿的直接脉动功率控制思路,并总结出适用于交流侧直接脉动功率控制的电路结构特征。基于该电路结构推导出补偿多次谐波引起的交流侧脉动功率的控制函数,提出适用于多模块串联结构的无电解电容单相电力变换器（整流和逆变）直接脉动功率控制策略。该方法在不增加硬件成本的条件下保证电能质量,同时在交流侧对脉动功率进行直接就地补偿,缩短了脉动功率流通路径,提高了系统的效率。通过实验验证了所提方法的有效性。

英文摘要：

In a single-phase power conversion system, bulky Electrolytic-capacitors（E-caps） are always used in voltage source converters at the DC-link to buffer the twice fundamental frequency pulsation power introduced by instantaneous unbalanced power between the AC and DC sides, and mitigate the harmonics from the AC side. However, the E-cap will cause harmful effects on the system, such as reducing the efficiency and shorting the lifetime of system. The E-cap free methods were identified as three types： reducing unbalance power, channeling new flowing path for the unbalanced power and compensating the unbalanced power inside of the converters. Based on this category, a directly pulsation power control strategy with differential structure was proposed, restraining the unbalanced power at the AC side by self-support, instead of transferring the unbalanced power to extra reliable energy storage components. Control functions for different kinds of harmonics were derived. Moreover, the control strategy for several modules in series for higher power was presented in this paper. The proposed directly pulsation power control strategy for single-phase converters（including rectifiers and inverters） could compensate the unbalanced power without extra hardware, reduce the flowing path of the pulsation power and improve the efficiency of the system. Experimental results are shown to verify the accuracy of the theoretical analysis.