Research On Power Flow And Optimal Power Flow Model Considering Frequency Characteristics For Interconnected Power Grid

The large-scale interconnection power system and intermittent random renewableenergy grid-connected are the irreversible tendency in the development of powerindustry. The large-scale interconnection of power system and development ofelectricity trading mechanism require higher for interface transmission active powercontrol between interconnection system region, and the intermittent and random powergeneration of renewable energy bring a new challenge, too. At present, the relatedresearch about power flow and optimal power flow model mostly differentiatefrequency adjustment and interface transmission active power constraints, but to theunit is limited to consider primary frequency control.It belongs to deviating regulation,however, the main fast buffer role, is the first line of the frequency control, the tasks ofbalancing active power shortage, restore power grid frequency and adjust the regionalinterface transmission active power still need to rely on secondary frequency regulationto realize finally. So, in this paper, the power flow model and optimal power flowconsidering frequency characteristics in interconnected power grid is studied, the maincontents are as follows:The power flow model considering frequency characteristics for interconnectedpower grid is presented. Based on the power flow equations considering frequencycharacteristics, the interface transmission active power constraint is considered into thismodel, and active power variables is attached to power-balance generator between theinterconnected power systems, and combined with the regional power on-siteadjustment balance principle of interconnection power system, the active controlequation of power-balance generator is established. The regulation power ofpower-balance generator is equal to the sum of area control error (ACE) of which areathose power-balance generators are in, and active power network loss error and plus thesuper short-term power forecasting error, Thereby the power flow model by consideringinterconnection power system frequency characteristics is established. The simulationresults of IEEE118-bus test system verify that the model is effective and necessary.The optimal power flow model considering frequency characteristics forinterconnected power grid is presented. In order to meet requirements of elaboratescheduling in modern interconnection power system, Based on the super short-termpower forecasting, the optimal power flow model for interconnected power grid which takes the minimum active power network loss as the optimization target is established.Relative to traditional optimal power flow, this model considers frequency characteristicof generator unit fully and the influence of frequency and node voltage on load, increasethe frequency quality, interface transmission active power and adjustable power ofgenerator inequality constraints. Using prediction-correction primal-dual interior pointmethod to solve the optimization model, the simulation results of5test systems verifythat the model is effective and necessary.To sum up, in this paper, new methods of power flow calculation and optimalpower flow is presented considering both frequency characteristics and interfacetransmission active power constraint, which provides powerful helpers of power systemanalysis and scheduling decision for new energy grid-connected and gradual growthinterconnection power system.