Research Of The Power System Generation Dispatch And Control For Large-Scale Variable Renewable Energy Integration

The excessive use of fossil fuels brings about the global warming effect and world-wide air pollution problems.As a result,the development of clean and renewable energy sources in place of fossil fuels becomes a consensus throughout the world.Regarding the electrical industry,wind power and solar photovoltaic(PV)power are the most promising renewable energy sources(apart from hydroelectric power)because of their mature application tech-niques and abundant exploitable reserves.They will play major roles in the future power generations.However,available generation capability of wind and PV power is related to the variable weather conditions,which leads to significant errors in their output forecast and strong variations in their output power.Both of them will become major challenges to the power generation dispatch and control when large-scale variables renewable generations(VRGs)are integrated into the power system.Hence,it is essential to develop new solutions to effectively cope with the forecast error and volatility in wind and PV power.The thesis summaries the status-of-quo of the research in dispatch and control methods for VRGs,based on which it studies the statistical patterns of VRGs,the station-level con-trol method to smooth the output variations of VRGs and the system-level optimal dispatch method to accommodate the uncertainty and volatility of VRGs.The content of the thesis is listed as follows:(1)Regarding the statistical patterns of VRGs,the thesis quantitatively studies the dura-tion time distributions and multi-time-scale output variation distributions of solar PV power to describe its volatility.The results provide important references to determine the output variation ranges of PV power in power system dispatch and to choose the optimal control time interval.The study also reveals that the abovementioned statistics of solar PV power are likely to be multi-modal,because of the joint-disturbances from the solar-earth evolu-tion and regional cloud movements.As a result,hybrid probability density functions are proposed to depict the statistical distributions.(2)Regarding station-level control of renewable power sources,the thesis proposes a novel control method for VRG power plant equipped with energy storage devices.The method aims to smooth’ the multi-time-scale output variations of VRG power according to the requirements of Grid Code.It combines the mathematical optimization technique and a simplified feedback control scheme in order to guarantee both the optimality and calculation speed of the control references.The proposed method can reasonably consider the VRG power forecast and optimize both the state-of-charge(SOC)of energy storage devices and VRG power curtailment.It minimizes the gap between the VRG power variation and Grid Code requirements with limited capacity of energy storage.(3)Regarding system-level power generation dispatch of VRGs,the thesis proposed an asymmetrical linear regulation strategy(ALRS)for automatic generation control(AGC)to cope with deviations from base points of VRGs power induced by their ultra-short-term forecast errors.The proposed strategy guarantees the consistency of decision rules in unit commitment/economic dispatch/AGC in response to the VRG power deviations.A robust unit commitment/economic dispatch method incorporating ALRS is then proposed to safely verified and optimized the regulation factors used in ALRS.The regulation factors can be individually optimized for different VRG power plant and different directions of VRG power deviations in order to fully utilize the output adjustment capability of controllable generators and to flexibly control the power flow distributions in AGC process.(4)Base on the robust dispatch method incorporating ALRS proposed in(3),the the-sis further improved the robust unit commitment method with expanded uncertainty set and sub-time-interval regulation constraints to accommodate the strong volatility of VRG power.The proposed solution can safely optimize the regulation strategy of generator output in re-sponse to the variations of VRG power according to their ramp rate and magnitude.More-over,since the proposed solution does not change the time interval used in unit commitment model,it will not severly increase the calculation burden.And the commitment plan,output adjustment capability and ramp rates of the controllable generators as well as the capacity of transmission lines can be thoroughly verified to meet the regulation requirements in coping with VRG power variations.(5)Carbon capture and storage(CCS)is an essential technique in reducing the CO2 emission of conventional thermal generators,which is predicted to be popularly used in the future power system.According to the operation characteristics of CCS devices,the thesis combines its energy consumption control with the robust dispatch method proposed in(3)and(4).Hence,the adjustment capability of CCS power consumptions can be reasonably utilized to accomodate the forecast error and volatility of VRG power while the CCS device is absorbing the CO2 emission.The proposed method provides an effective solution for the optimal dispatch of CCS devices in the future power system with large-scale VRGs.