4.2. SPreNFC Temperature Control PrinciplesIn the negative feedback control, the proportion control is verysimple, and the response speed is quick, but when the proportioncoefficientis small,the resisting ambient disturbance ability will beweak, and when the proportion coefficient is large, constant amplitude will appear for the system delay. So considering the quickresponse quality of the proportion control, a controlled variable isadded on the basis of proportion controlto counteractthe influencecaused by controlled object response lag.Suppose Tstack(k) is the stack measured temperature at kthsampling time, Tset(k) is the optimal temperature under presentload current, so the temperature error at kth time is e(k), namely: