In this chapter, we study the impact of various AGC implementations on frequency stability and long-term performance of system frequency. We provide an analogy between the discrete AGC and a dynamic real-time electric market model (market-based AGC). Such an analogy then allows studying the impact of Market-based Automatic Generation Control (MAGC)-induced imbalances on the dynamic behavior of power systems. Finally, the chapter studies the effect of “memory” of market participants on short-term frequency quality. The memory effect is represented by employing proper mathematical tools from the theory of fractional calculus.