Research On The Multi-time Scale Rolling Scheduling Method For Combined Heat And Power System

CHP(combined heat and power) units as well as wind power units coexist in the “Three North” area with large proportion, which brings a lot of difficulties to power grid dispatching. Due to the “power subject to heat” constrain of CHP units as well as the properties including obvious anti-peaking operation and volatility of wind power, the existing combined heat and power scheduling has some problems,such as seriously wind power abandoning and large deviation between scheduling plan and load demand, etc. Aiming at these problems, the solution of curtailed wind power accommodation based on electric boiler for distributed daily peak-load regulation at secondary heat supply network is put forward. Besides, the multi-time scale rolling scheduling is extended to the combined heat and power system containing wind power units, CHP units and electric boiler, and a set of scheduling strategies which apply to special power structure of “Three North” area are formed.At first, the relationships between electrical load, thermal load and wind power output are studied. The solution of curtailed wind power accommodation by installing an electric boiler in the secondary heat supply network for distributed daily peak-load regulation is proposed by referring to the characteristics of peak-load regulation of power grid and heat supply network, and the mechanism of the scheme to improve wind power accommodation is analyzed.Secondly, a prediction method to detect abandoned wind power is proposed combined with the forecast of electrical load, thermal load and wind power output.Meanwhile, the two start-stop operation strategies named Threshold Start-stop Strategy and Abandoned Wind Start-stop Strategy are put forward based on the operation characteristic that electric boiler only start at the peak of the thermal load.The influence of these two start-stop strategies on economy and wind power accommodation rate of combined heat and power scheduling is analyzed by simulation.Next, an optimal day-ahead scheduling model for combined heat and power system which regardless of wind power cost, considers electric boiler for distributed daily peak-load regulation at secondary heat supply network, and uses minimum of total coal consumption as object function is constructed, based on fuel cost functions of power-only unit and CHP unit as well as electric and heat transfer function of electric boiler. The improved particle swarm optimization is proposed to improve the proportion of feasible solutions through self-adjustment of the particle,which can accelerate the searching speed of the algorithm.Finally, the multi-time scale rolling scheduling method for combined heat and power system is studied, and the daily scheduling plan of combined heat and power system is divided into the day-ahead scheduling plan, the rolling scheduling plan and the real-time scheduling plan. The model of scheduling plan with each time scale is established, the coordination strategies of scheduling plans with different time scales are researched, and the overall implementing flow of the multi-time scale rolling scheduling is planed.Research results show that the distributed daily peak-load regulation plan with electric boiler at secondary heat supply network can reduce thermal load peak value and forced power output determined by the heat of CHP units while increasing the valley value of electrical load. In this way, more reserve of power grid is left to enhance wind power accommodation and coal consumption of the whole system is reduced. After using the multi-time scale rolling scheduling, the real-time scheduling scheme can effectively track the load curve and further improve the wind power accommodation through being corrected by rolling scheduling and being adjusted by real-time scheduling.