Review of System Strength and Inertia Requirements for the National Electricity Market of Australia

Synchronous generators(SGs)are still making major contributions to the re-stabilization of a power system following voltage/frequency disturbances,attributed to their inherent capability of providing system strength and inertia.However,SGs powered by fossil fuels are operating to a lesser extent and scheduled for decommissioning in the National Electricity Market(NEM)of Australia due to the accelerating increase of low bidding priced asynchronous generation of wind and solar,which leads to the reduction and even in some cases,a shortage of system strength and inertia.This paper comprehensively reviews the requirements of system strength and inertia in the NEM from an operational security perspective.Australia is the first country that established the regulation rules of system strength and inertia to accommodate issues of an emerging high penetration level of non-synchronous renewable generation.

Frequency Response of PV Inverters Toward High Renewable Penetrated Distribution Networks

Substantial usage of electronic-based renewable energy resources has completely changed the dynamic behaviours and response time of power networks,which are now fundamentally different from traditional power networks dominated by Synchronous Generators(SGs).This paper evaluates the dynamic response of small-scale Photovoltaic(PV)inverters,which dominate the distribution networks and influence the dynamics of the entire power grid.Recently,some critical events which occurred in Australia have shown that the dynamic responses of small-scale inverters do not always follow the inverter standards.Subsequently,these uncertainties make PV inverters’response unpredictable and have the potential to threaten the security of power networks.The detailed investigation of the dynamic response characteristics of small-scale PV inverters to grid disturbances is lacking in the current literature.This paper presents new findings from experimental testing under extensive network disturbance scenarios.Furthermore,a datadriven method is proposed to accurately describe the dynamics of solar PV subjected to various frequency disturbances.The results provide beneficial insight to the network operators in predicting power system response to extreme disturbances and avoiding potential grid instability issues,which will assist in achieving 100%penetration of power electronics-based renewable energy resources in the future.