Small-signal modelling and stability analysis of grid-following and grid-forming inverters dominated power system

In this paper,the explicit state-space model for a multi-inverter system including grid-following inverter-based generators(IBGs)and grid-forming IBGs is developed by the two-level component connection method(CCM),which modularized inverter control blocks at the primary level and IBGs at the secondary level.Based on the comprehensive state-space model representing full order of system dynamics,eigenvalues of the overall system are thoroughly analyzed,identifying potential adverse impacts of not only grid-following inverters,but also grid forming inverters on the system small-signal stability,with the underlying principle of oscillations also understood.Numerical and simulation results validate effectiveness of the proposed methodology on IEEE benchmarking 39-bus system.

Finite-time economic model predictive control for optimal load dispatch and frequency regulation in interconnected power systems

This paper presents a finite-time economic model predictive control(MPC)algorithm that can be used for frequency regulation and optimal load dispatch in multi-area power systems.Economic MPC can be used in a power system to ensure frequency stability,real-time economic optimization,control of the system and optimal load dispatch from it.A generalized terminal penalty term was used,and the finite-time convergence of the system was guaranteed.The effectiveness of the proposed model predictive control algorithm was verified by simulating a power system,which had two areas connected by an AC tie line.The simulation results demonstrated the effectiveness of the algorithm.

Optimal operation of integrated energy system including power thermal and gas subsystems

As a form of hybrid multi-energy systems,the integrated energy system contains different forms of energy such as power,thermal,and gas which meet the load of various energy forms.Focusing mainly on model building and optimal operation of the integrated energy system,in this paper,the dist-flow method is applied to quickly calculate the power flow and the gas system model is built by the analogy of the power system model.In addition,the piecewise linearization method is applied to solve the quadratic Weymouth gas flow equation,and the alternating direction method of multipliers(ADMM)method is applied to narrow the optimal results of each subsystem at the coupling point.The entire system reaches its optimal operation through multiple iterations.The power-thermal-gas integrated energy system used in the case study includes an IEEE-33 bus power system,a Belgian 20 node natural gas system,and a six node thermal system.Simulation-based calculations and comparison of the results under different scenarios prove that the power-thermal-gas integrated energy system enhances the flexibility and stability of the system as well as reducing system operating costs to some extent.