Frequency Analysis And Control Strategy Research Of Water-Photovoltaic Storage Complementary System Containing Full-Power Pumped Storage Unit

The research object of this subject is a hydro-photovoltaic complementary system of Sichuan Power Grid.The demonstration area belongs to the power transmission system,the system load is small,and most of the power needs to be sent to the large power grid.When the demonstration area is connected to the large power grid for power generation,due to the large inertia of the large power grid and strong regulation capability,the frequency stability problem of the system is not prominent;due to the relatively weak connection between the complementary system and the large power grid,the interaction between the demonstration area and the large power grid is relatively weak.The tie line may exit operation unplanned,which leads to isolated grid operation of the power grid in the demonstration area.At this time,the frequency stability of the grid needs to face two main problems:one is the transient frequency transition process of the demonstration area at the moment when the demonstration area turns from the grid-connected state to the off-grid operation;the other is the steady-state and transient frequency stability of isolated network operation after the transition of the transition state.This paper first introduces the characteristics,structure and output characteristics of the hydro-photovoltaic storage complementary system,analyzes the structural framework and operation mode of the complementary system,and builds a hydro-photovoltaic storage complementary combined power generation system model on the PSD-BPA simulation platform.Including the simulation principle and simulation model construction of each module of hydropower unit,photovoltaic power supply and full-power pumped storage unit.Based on the field data in the demonstration area and the actual machine parameters of each power plant,appropriate improvements have been made according to the subject requirements,and the simulation model of the complementary system has been established.Secondly,in order to deal with the transient frequency transition process of the water-photovoltaic storage complementary system from grid-connected state to off-grid operation,an emergency control strategy of high-frequency cut-off is proposed.First,compare the various power supplies in the system from the frequency modulation ability,inertia support,and tolerance frequency fluctuation range.Then it evaluated the influence of the cutting machine arrangement on the stable control of the off-grid frequency,and at the same time,according to the evaluation index of the frequency recovery curve after the high-frequency cutting machine action,based on which judges the pros and cons of the machine cutting plan,and for the most serious high-frequency problems Assess the optimal allocation of the capacity of the three types of units in the total amount of high-frequency cutting machines.Finally,in order to take into account other small power surpluses,the appropriate cut-off sequence of the three types of power sources is determined in combination with the actual system,and the unit arrangement of each round of the high-frequency cut-off is further optimized,which can obtain a preliminary amount of PV frequency modulation capability.The optimization method of the high-frequency cutting machine scheme with the participation of the type of power supply,and the high-frequency cutting scheme for the studied power grid is proposed,and at the same time,the role positioning in the high-frequency cutting machine is pointed out for the regulation effect of the variable-speed pumped storage unit.Finally,with the independent operation of the isolated network as the background,the static safety analysis and transient safety analysis of the complementary system are carried out,and suitable safety and stability control strategies are proposed according to the conclusions of the static and transient analysis.Including the selection of suitable hot standby units through system power flow analysis to balance the system power shortage,exploring the impact of removing different types of loads on system frequency recovery as a basis for low-frequency load shedding,proposing black start strategies to deal with local grid paralysis,and proposing hierarchical frequency modulation control strategies in order to solve the possible load sudden drop failure,at the same time,a brief description of the night operation mode was made,which verified the rapid response of the full-power pumped storage unit to active power under pumping conditions.