Robust Droop Control of AC Microgrid Against Nonlinear Characteristic of Inductor

This paper investigates the effect of nonlinear characteristic of filter inductor on power sharing performance of droop-controlled microgrid, and presents a robust droop control strategy to implement proportional reactive power sharing with immunity to nonlinear characteristic of filter inductor. Considering current-dependent soft-saturation natures of filter inductor, time-variant average model of inductor is first established to reveal the nonlinear inductance characteristic. Then, output impedance model of inverters with consideration of nonlinear inductor is derived to analyze the effect of nonlinear inductor on reactive power sharing characteristic. Furthermore, a robust droop control strategy is proposed to mitigate the effect of nonlinear inductor on reactive power sharing and implement proportional reactive power sharing under different load profiles. Simulation and experimental results show that the proposed droop control strategy is able to perform desirable power sharing with a good capability to reject nonlinear characteristic of filter inductor.

[1]  Chih-Wei Hsu,et al.  An Improved Resonant Frequency Based Systematic LCL Filter Design Method for Grid-Connected Inverter , 2017, IEEE Transactions on Industrial Electronics.

[2]  Ju Hyung Kim,et al.  Nonlinear analytical model of an inductance considering saturation and temperature variation , 2017, 2017 IEEE Energy Conversion Congress and Exposition (ECCE).

[3]  Robert Lasseter,et al.  Smart Distribution: Coupled Microgrids , 2011, Proceedings of the IEEE.

[4]  Bangyin Liu,et al.  Current Ripple Analysis and Controller Design for Grid-Connected Converters Considering the Soft-Saturation Nature of the Powder Cores , 2018, IEEE Transactions on Power Electronics.

[5]  Hua Jin,et al.  Control of parallel inverters in distributed AC power systems with consideration of line impedance effect , 2000 .

[6]  Frede Blaabjerg,et al.  Distributed Optimal Control of Reactive Power and Voltage in Islanded Microgrids , 2017, IEEE Transactions on Industry Applications.

[7]  Chao Yang,et al.  An Estimator-Based Distributed Voltage-Predictive Control Strategy for AC Islanded Microgrids , 2015, IEEE Transactions on Power Electronics.

[8]  Yen-Hsiang Huang,et al.  Direct Digital Control of Single-Phase Grid-Connected Inverters With LCL Filter Based on Inductance Estimation Model , 2019, IEEE Transactions on Power Electronics.

[9]  R. Adapa,et al.  Control of parallel connected inverters in stand-alone AC supply systems , 1991, Conference Record of the 1991 IEEE Industry Applications Society Annual Meeting.

[10]  Jin Jiang,et al.  Accurate Reactive Power Sharing in an Islanded Microgrid Using Adaptive Virtual Impedances , 2015, IEEE Transactions on Power Electronics.

[11]  Jian Yang,et al.  A novel quasi-master-slave control frame for PV-storage independent microgrid , 2018 .

[12]  Xiongfei Wang,et al.  Harmonic Instability Assessment Using State-Space Modeling and Participation Analysis in Inverter-Fed Power Systems , 2017, IEEE Transactions on Industrial Electronics.

[13]  Zhe Chen,et al.  Small-Signal Stability Analysis of Inverter-Fed Power Systems Using Component Connection Method , 2017 .

[14]  Frede Blaabjerg,et al.  An Enhanced Islanding Microgrid Reactive Power, Imbalance Power, and Harmonic Power Sharing Scheme , 2015, IEEE Transactions on Power Electronics.

[15]  Moin Hanif,et al.  Modelling powder core inductors for passive filters in inverters using finite element analysis , 2017 .

[16]  Yanbo Wang,et al.  Lifetime-Oriented Droop Control Strategy for AC Islanded Microgrids , 2019, IEEE Transactions on Industry Applications.

[17]  Juan Carlos Balda,et al.  Realization of high-current variable AC filter inductors using silicon iron powder magnetic core , 2017, 2017 IEEE Applied Power Electronics Conference and Exposition (APEC).