Study On Peak-shaving Flexibility Of Gas Turbine Power Generation System Coupled With Offshore Hydraulic Energy Storage

As a peak-shaving unit,gas turbine plays an indispensable and important role in power grid load regulation.Facing the demand for deep peak shaving of power grids under the background of newable energy consumption,adopting an advanced peak regulation method to balance the peak-valley difference of generating unit and increasing the peak shaving range and economy has become an indispensable part in the development of gas turbine power plant systems.However,due to the influence of external load fluctuations,the gas turbine of power station usually operates under variable operating conditions,leading to low operating efficiency of the unit.Moreover,the peak load regulation capacity is limited by the design parameters of the unit,load control strategies and equipment life,so it is difficult to match the demand side load in real time and flexibly in a wide range.Therefore,improving the flexibility of gas turbine peak regulation under different external loads and reducing energy consumption have become the key problems to be solved urgently in gas turbine peak regulation technology.Based on this,an offshore hydraulic energy storage coupled gas turbine power generation system was proposed.Mathematical modeling and solving of a 11 410k W gas turbine and energy storage system was carried out respectively to obtain the operating characteristic curves of pump turbine under all operating conditions.The influence of different output load ratios of gas turbines on the performance of the coupling system was analyzed and compared with the operation performance of conventional gas turbines.At the same time,the multi-objective optimization calculation of the system is carried out,and the economic problems of the system are analyzed.The research shows that the optimal operating efficiency of the pump turbine is 72.88%when the head is 235～245 m under the designed filling and drainage flow rate.The peak shaving depth of the coupled system reaches 81.54%,increasing by 11.54%compared to the reference gas turbine system.The output power and operating efficiency of the coupled system increase first and then decrease with the rise of the demand load,and reach a peak at 9336.98 k W and 25.98%at relative demand load of 0.52.Under delay-step demand load,the daily average efficiency of the system is comparatively higher than that of reference gas turbines.The relative efficiency increases with the decrease of the peak-to-valley ratio or increase of the valley charge frequency.the relative efficiency of the system is as high as14.9%when the peak-to-valley ratio is 4 and the valley-load frequency is 0.5.The optimization results show that when the peak-to-valley ratio is greater than 3 and the valley-load frequency is greater than 0.375,the minimum design capacity of gas turbine and energy storage device is 7553.57k W and 1843k W,respectively.When the peak-to-valley ratio is less than 3.8,the peak adjustment depth of the system can reach 100%.The economic analysis results show that,at a given natural gas price,there are critical values of valley-load frequency,peak-to-valley ratio and peak-to-valley price ratio,which makes the coupled system more economical than conventional gas turbine.For example,when the natural gas price is 2.5 yuan/m~3and the valley-load frequency is 0.5,the peak-to-valley ratio of the external load must be higher than 3.875 to make the coupling system economical.Moreover,the critical value of the peak-to-valley ratio increases with the increase of the valley load frequency.