基于CPLEX半连续变量求解发电机组单时段经济调度问题，给定负荷需求，求每台发电机输出P=0或Pmin<=P<=Pmax,使发电成本最小。-Semi-continuous variable based on CPLEX to solve a single period of economic generator scheduling problem, given the load demand, seeking each generator output P = 0 or Pmin