Large-scale Ultra High Voltage Alternate/direct current hydropower absorption problems

With huge hydropower plants, such as Xiluodu, Xiangjiba, Nuozhadu and Jingping located in the watershed of Jinshajiang, Yalongjiang and Lancangjiang being completed and put into commission, hydropower transmission capacity in China is expanded rapidly. Large-scale hydropower transmission has a direct impact on the rational allocation of electricity resources in national scale, especially on the compromise between absorbing hydropower for sending end power grids and shaving peak load for receiving end power grids. However, owing to the limited regulation and absorption capacity of sending end hydropower plants, existing transmission schedules of hydropower in China are based on own operating requirements or surplus electricity of the sending end power grids. Thus it is vulnerable to "straight line" or "opposite peak shaving" transmission schedules which in turn aggravate pressure to peak shaving load in receiving end power grids. This is in opposite to the absorption and quality peak regulation capability of large-scale hydropower. A new challenge for the coordinating operations is how to utilize load peak and valley difference and the characteristics of different power sources to absorb surplus hydropower from supplying power grids and to shave peak load for receiving power grids, so as to exhibit the complementary roles of inter-basin cascade hydropower stations. The problem involves optimization scheduling methods, compensation mechanism, peak thresholds and coordination strategy among regional power grids, province power grids and plants. The key of the problem is to solve the existing large-scale Ultra High Voltage Alternate Current (UHVAC)/Ultra High Voltage Direct Current (UHVDC) hydropower absorption in China. The purposes are to allocate power resources more rationally, alleviate the pressure of the receiving end power grid from peak shaving, improve the power source structures of Yangtze Delta and Pearl River Delta, reduce the haze pressure in these areas, and effectively safeguard the safety, economy and environmental protection, reliable operation of power grids in China.