A variety of power generation complementary can reduce the large power fluctuation in the electrical power system caused by large-scale new energy power connected into grid. The quick power generation such as hydropower, gas power, and fuel power are the most suitable complementary power. However, they are very short in China; meanwhile the coal-fired power with slow rate of power change is dominant. Consequently, the coal-fired power has to increase its load change range and speed so as to undertake the job of power complementation in the electric power system. This paper proposes a method to improve the load change capacity for the water cooled power plants through controlling the cooling water flow. Then the CCWCS (condenser cooling water control system) is put forward to execute this method on the premise of unit safety. CCWCS can also reduce the coal consumption in steady turbine load conditions. Based on the modeling of condenser, variable speed pump for the condenser cooling water and the characteristics of turbine power output to condenser pressure, the paper presents the relationship between the cooling water flow and turbine power output. Finally, a case study on a 600,000 kW unit proves the feasibility of our idea. (C) 2013 Elsevier Ltd. All rights reserved.