The traditional balance strategy with a sort method has some disadvantages and can cause different types of deteriorationsin an MMC system, including an increase in the switching frequency and distortions in the currents. However, quantitativeanalyses for these deteriorations are neglected during the design of the balance strategy, which decreases the effect of thestrategy. This paper first develops accurate descriptions for an MMC system and the structure of its balance strategy. Basedon these descriptions, the root cause and quantitative degree of the switching frequency increase are both determined for thefirst time. A quantitative analysis for the degree of the current distortion is obtained as well. Based on the above analysis, astate switcher and balancing-time calculator are proposed and introduced into the balance strategy, which effectively decreasethe magnitudes of these deteriorations. The deteriorations caused by the traditional balance strategy and efficiency of theimproved balance strategy are finally demonstrated via experimental results.