Decentralized Primary Frequency Regulation for Hybrid Multi-terminal Direct Current Power Systems Considering Multi-source Enhancement

Hybrid multi-terminal direct current(MTDC)transmission technology has been a research focus,and primary frequency regulation(FR)improvement in the receiving-end system is one of the problems to be solved.This paper presents a decentralized primary FR scheme for hybrid MTDC power systems considering multi-source enhancement to help suppress frequency disturbance in the receiving-end systems.All the converters only need local frequency or DC voltage signal input to respond to system disturbance without communication or a control center,i.e.,a decentralized control scheme.The proposed scheme can activate appropriate power sources to assist in FR in various system disturbance severities with fine-designed thresholds,ensuring sufficient utilization of each power source.To better balance FR performance and FR resource participation,an evaluation index is proposed and the parameter optimization problem is further conducted.Finally,the validity of the proposed scheme is verified by simulations in MATLAB/Simulink.

Scenario-based Unit Commitment Optimization for Power System with Large-scale Wind Power Participating in Primary Frequency Regulation

Continuous increase of wind power penetration brings high randomness to power system,and also leads to serious shortage of primary frequency regulation(PFR)reserve for power system whose reserve capacity is typically provided by conventional units.Considering large-scale wind power participating in PFR,this paper proposes a unit commitment optimization model with respect to coordination of steady state and transient state.In addition to traditional operation costs,losses of wind farm de-loaded operation,environmental benefits and transient frequency safety costs in high-risk stochastic scenarios are also considered in the model.Besides,the model makes full use of interruptible loads on demand side as one of the PFR reserve sources.A selection method for high-risk scenarios is also proposed to improve the calculation efficiency.Finally,this paper proposes an inner-outer iterative optimization method for the model solution.The method is validated by the New England 10-machine system,and the results show that the optimization model can guarantee both the safety of transient frequency and the economy of system operation.

Mechanism of Primary Frequency Regulation for Battery Hybridization in Hydropower Plant

Battery hybridization in hydropower plants is a hydropower flexibility enhancement technology innovation that can potentially expand hydropower’s contributions to the grid,but its fundamental characteristics and influencing mechanisms are still unclear.In this paper,primary frequency regulation(PFR)performance and the mechanism of this new technology are studied.A battery hybridized hydropower plant(BH-HPP)model,based on a field-measured-data-based hydropower plant(HPP)model and a verified battery simplified model,is established.Analysis of system stability and dynamics is undertaken for three different battery control strategies by root locus and participation factor methods.Compared to conventional HPPs,analysis results theoretically reveal BH-HPP can not only accelerate system regulation rapidity but also effectively enlarge HPP stability region during PFR process.Time domain simulation verifies the results and further shows synthetic control has better performance among introduced strategies.Besides,initial design ranges of control parameters considering battery capacity and a renewable energy source scenario case are also discussed.This work could provide theoretical support for flexibility enhancement solutions for hydropower systems.

Frequency-constrained Unit Commitments with Linear Rules Extracted from Simulation Results Considering Regulations from Battery Storage

Heavy renewable penetrations and high-voltage cross-regional transmission systems reduce the inertia and critical frequency stability of power systems after disturbances.Therefore,the power system operators should ensure the frequency nadirs after possible disturbances are within the set restriction,e.g.,0.20 Hz.Traditional methods utilize linearized and simplified control models to quantify the frequency nadirs and achieve frequency-constrained unit commitments(FCUCs).However,the simplified models are hard to depict the frequency responses of practical units after disturbances.Also,they usually neglect the regulations from battery storage.This paper achieves FCUCs with linear rules extracted from massive simulation results.We simulate the frequency responses on typical thermal-hydro-storage systems under diverse unit online conditions.Then,we extract the rules of frequency nadirs after disturbances merely with linear support vector machine to evaluate the frequency stability of power systems.The algorithm holds a high accuracy in a wide range of frequency restrictions.Finally,we apply the rules to three typical cases to show the influences of frequency constraints on unit commitments.

Parameter identification of interconnected power system frequency after trip-out of high voltage transmission line

Accurate modeling and parameters of high voltage （HV） grid are critical for stability research of system frequency. In this paper, simulation modeling of the system frequency was conducted of an interconnected power system with HV transmission lines in China. Based on recorded tripping data of the HV transmission lines, system parameters were identified by using genetic algorithm （GA）. The favorable agreement between simulation results and recorded data verifies the validity of gird models and the accuracy of system parameters. The results of this paper can provide reference for the stability research of HV power grid.