Why are Cining Palace and Shoukang Palace the residence of the Empress Dowager?

Cining Palace has always been the residence of Empress Dowager and Empress Dowager since the completion of the Ming Dynasty. In the Qing Dynasty, there was only one Empress Dowager, that is, sourdrang dowager, Kangxi's grandmother, and then there was no Empress Dowager. The reason is that later generations think that sourdrang dowager's position is too high for others to hold back. Therefore, after the Queen Mother, Taifei began not to live in Cining Palace. Empress Xiao Gongren, the Empress Dowager of Yongzheng Dynasty, also lived in Yonghe Palace. Shoukang Palace was built in Qianlong Dynasty, and then the Empress Dowager Taifei began to live in Shoukang Palace.