Research On Planning Method Of Generation,Transmission,and Energy Storage Systems Considering Frequency Security With Renewable Energy Integration

Under the background of “dual-carbon”,renewable energy represented by wind and solar units replace large-scale synchronous generators,which reduces synchronous inertias and weakens system frequency response-ability.The traditional power system planning methods cannot theoretically adapt to the frequency response requirement in future lowinertia power systems.From the perspective of coordination optimization for generation,transmission,and energy storage(GTE),it is necessary to propose frequency-constrained planning methods of GTE systems for guaranteeing the safe consumption of renewable energy.This paper focuses on the scientific problem of how to realize coordinated planning of multi-area GTE systems with renewable energy integration,which considers the otherness and complementarity of various frequency response modes.It tends to satisfy frequency-security requirements economically in future low-inertia power systems by allocating inertial resources and planning the appropriate topology of the transmission network.The main research work is as follows:(1)Unit commitment method considering frequency-reserve optimization(FRO)allocation is proposed.The formulation of multi-stage primary frequency response power is constructed to reflect various frequency response speeds based on the response-ability of the synchronous and renewable energy units.In view of the maximal rate-of-change-offrequency and nadir frequency,constraints of the least system inertia and optimal frequency reserve are proposed,which are further transformed into mixed-integer second-order cone forms through conditional-selected and second-order cone theory.Based on typical planning scenarios from Gaussian mixture clustering,the frequency-constrained UC model is proposed,which considers both FRO and dynamic renewable deloading strategy.(2)Generation planning method embedded with system comprehensive frequency response is proposed.The system frequency response(SFR)model is constructed in view of the multi-machine coordination response as well as the concise control loop,which is converted into an equivalent single-unit counterpart through the multi-machine equivalence method based on the capacity proportion.The function of frequency deviation in the time domain is further deduced based on the inverse Laplace transformation.The mixed-integer linearization constraint of frequency response power is constructed based on the categorically-minded piecewise linearization method.The generation planning model embedded with system comprehensive frequency response is proposed,which coordinates unit commitment,frequency mode decision,and frequency-reserve optimization.(3)Energy storage planning method considering the characteristic of quick frequency response is proposed.The primary frequency counterpart of battery energy storage(ESs)is formulated from droop control mode.The maximal frequency reserve and electric quantity connected with charging/discharging states are quantified.Considering the thermal state of the boiler,the frequency response model that coordinates ESs with various generators is constructed.A bilevel ESs planning model that considers quick frequency responses is proposed considering FRO.A heuristic optimization-simulation solution strategy based on the L-shape method is proposed,where the frequency-security cut constraint is constructed to solve this bi-level problem.(4)Transmission network planning(TEP)method that coordinates with generation frequency response is proposed with generation-load uncertainty.The adaptive polyhedraluncertainty set is utilized to describe variations of source-load.In allusion to the worst-case of source-load,a two-stage robust load reserve optimization method is proposed.A threelevel frequency-constrained robust TEP model is constructed with limitations of postfrequency power flow constraints.The upper level decides on TEP as well as reserve allocation schemes,which makes network topology coordinate with generation frequency response through limitations of transmission capacity after frequency response.The middle level finds the worst-case scenario considering variations of renewable energy and load demand.The lower level is a re-adjustment problem of generators to satisfy operation constraints under uncertain scenarios.The three-level robust TEP problem is transformed into a bilevel model based on the duality theory,which can be efficiently solved by the column-and-constraint generation algorithm.(5)Joint planning method of generation,transmission,and energy storage systems considering multi-area frequency responses is proposed.Generators consider the regulation ability based on unit commitment to supply multi-type reserves.Optimal transmission switching is employed to change network topologies flexibly.The system regulation ability is enhanced from both sides of generation and network.The tie-line model considering operation mode,reversal times,and power flow deviation is established.To coordinate energy storage planning with generation and transmission systems,the joint planning model of generation,transmission,and energy storage systems considering the systematic regulation ability and multi-area frequency responses is constructed.The proposed method can solve the problem of how to satisfy frequency security through the planning of generation,transmission,and energy storage systems with renewable energy integration.The efficiency of the proposed planning model and method is proved based on the modified IEEE RTS-79 system and the regional network system.The results indicate that the proposed planning method can promote consumption of renewable energy on the premise of frequency security.