Research On Frequency Analysis And Control Optimization Strategy Of Regional Power Grid With Large-scale New Energy

With the large-scale integration of new energy sources such as wind power and photovoltaic(PV)power into the grid,The traditional frequency modulation(FM)unit in the regional power grid not only need to meet the FM capacity demand brought by the internal power load change,but also need to meet the additional FM pressure for quickly tracking the intermittent new energy power fluctuation,which threatened the frequency stability of regional power grids and also limited the access ratio of new energy power.Therefore,this paper took Ningxia regional power grid as an example to study the influence of wind power fluctuation on the frequency stability of Ningxia regional power grid through simulation examples from the perspective of regional network frequency stability.And basing on the restriction that the fluctuation of power grid frequency was less than 0.1HZ,an effective strategy for frequency fluctuation control of regional power grid under the background of large-scale new energy power grid-connected is proposed.Firstly,aiming at the local consumption problem of large-scale new energy that Ningxia power grid currently facing,this paper established a regional network frequency control analysis system model with new energy power fluctuations combining the actual power load structure characteristics of the power grid,which considered its main frequency modulation unit—The detailed structure of the thermal power unit and the main control logic,the turbine involved in the FM model and the system structure of the multi-machine grid.The system model founded could truly reflect the actual FM dynamic characteristics of regional power grid while new energy power fluctuates and load suddenly changes,which had laid a foundation for the follow-up research on analysis of frequency stability and control strategy optimization of regional power network in Ningxia by large-scale new energy power fluctuation.Then,based on the source of the disturbance and the measured data of the gr id,the paper analyzed the fluctuation characteristics of the existing new energy power and load on the second and minute time scales.And the equivalent load research method that taking wind and PV power as “negative” load was proposed,following a qualitative analysis of the problems that existing wind and photovoltaic power access might bring to the frequency stability of Ningxia power grid.Besides,combining with the regional network frequency control system model,quantitative simulation was carried out under different load scenarios with the limitation of frequency difference fluctuation.Thus,the wind and PV power mutation domain which caused the frequency difference fluctuation excess of Ningxia power grid was obtained.On this basis,the constraints of limiting the access of large-scale new energy were analyzed from the angle of primary and secondary FM,which set a foundation for the control optimization strategy to improve the network frequency fluctuation.Thirdly,in view of the problem of insufficient traditional FM capacity of Ningxia power grid,the corresponding optimization strategies were proposed on the basis of its original.For fluctuation component of the new energy power with low amplitude and in second scale,the variable-tuning coefficient optimization control strategy with the grid frequency offset as the independent variable and the primary frequency differential feedforward combined with the grid frequency deviation change rate were adopted under the premise of ensuring the safe and stable operation of the generator units,which were used to improving the primary FM capability of grid-connected units.For fluctuation component of the wind and PV power with high amplitude and in minute scale,the new energy power prediction value was introduced into the Automatic generation control(AGC)feedforward channel basing on the influence of the prediction error,so that the secondary FM capability of grid-connected AGC units was enhanced.The effectiveness of the above two optimization strategies was verified by simulation examples.Finally,in order to further suppress the large frequency difference disturbance caused by the new energy power fluctuation,this paper proposed to configure the battery energy storage to participate in the primary FM auxiliary control strategy on the grid side and the auxiliary FM strategy that setting adjustable load of electrolytic aluminum on demand side.The FM performance of the power grid was maximized by means of coordination between the main and the auxiliary,and the effectiveness of the above two auxiliary frequency modulation methods was verified by model simulation.