Analysis and synchronization controller design of dual-port gridforming voltage-source converters for different operation modes

Grid-tie voltage source converters(VSCs)can operate in three distinct modes:AC-dominant,DC-dominant,and balanced,depending on the placement of the stiff voltage sources.The distinct operation modes of the VSCs traditionally demand different synchronization control techniques,leading to heterogeneous VSCs.It is challenging for the power system to accommodate and coordinate heterogeneous VSCs.A promising universal synchronization control technique for VSCs is the DC-link voltage synchronization control(DVSC)based on a lead compensator(LC).The LC DVSC stabilizes both the DC and AC voltages of a VSC while achieving synchronization with the AC grid.This results in a dual-port grid-forming(DGFM)characteristic for the VSC.However,there has been very limited study on the stability and synchronization controller design of the VSCs with the LC DVSC operating in various modes.To bridge this gap,the paper presents a quantitative analysis on the stability and steady-state performance of the LC DVSC in all three operation modes of the DGFM VSC.Based on the analysis,the paper provides step-by-step design guidelines for the LC DVSC.Furthermore,the paper uncovers an instability issue related to the LC DVSC when the DGFM VSC operates in the balanced mode.To tackle the instability issue,a virtual resistance control is proposed and integrated with the LC DVSC.Simulation results validate the analysis and demonstrate the effectiveness of the DGFM VSC with the LC DVSC designed using the proposed guidelines in all three operation modes.Overall,the paper demonstrates the feasibility of employing the DGFM VSC with the LC DVSC for all three possible operation modes,which can help overcome the challenges associated with accommodating and coordinating heterogeneous VSCs in the power system.

Transitioning from heterogeneous VSC to homogeneous VSC based power systems:Leveraging dual-port grid-forming VSCs

Original reference:iEnergy,3(1):46-58,2024 Grid-tie voltage source converters(VSCs)can operate in three distinct modes:AC-dominant,DC-dominant,and balanced,depending on the placement of the stiff voltage sources,as shown in Figure 1.The distinct operation modes of VSCs typically require different synchronization control techniques.For instance,the grid-following(GFL)control,which utilizes a phase-locked loop to track the AC grid phase and frequency,can be employed for VSCs operating in the AC-dominant mode and the balanced mode.On the other hand,the grid-forming(GFM)control is uti-lized for VSCs operating in the DC-dominant mode and the bal-anced mode.Therefore,neither GFM control nor GFL control can serve as a universal synchronization control technique for VSCs to operate in all of the three modes.While the combination of the GFL VSCs and the GFM VSCs can handle applications that require the VSCs to operate in all of the three modes,effectively accommodating and coordinating the heterogeneous GFL and GFM VSCs remains challenging for power systems.

Prognostic Condition Monitoring for Wind Turbine Drivetrains via Generator Current Analysis

Maintenance costs account for a significant portion of the total cost of electricity generated by wind turbines.Currently in the wind power industry,maintenance is mainly performed on regular schedules or when significant damage occurs in a wind turbine making it inoperable,instead of being determined by the actual condition of the wind turbine.Among the total maintenance costs,approximately 25%~35%is related to regularly scheduled preventive maintenance and 65%~75%to unscheduled corrective maintenance.To reduce the failure rate and level and maintenance costs and improve the availability,reliability,safety,and lifespans of wind turbines,it is desirable to perform condition-based predictive maintenance for wind turbines,which will require a high-fidelity online prognostic condition monitoring system(CMS)for fault diagnosis and prognosis and remaining useful life(RUL)prediction of wind turbines.Most of the existing wind turbine CMSs are based on vibration monitoring and have no or limited capability in fault prognosis and RUL prediction.Compared to vibration monitoring,the prognostic condition monitoring techniques based on generator current signal analysis proposed recently have significant advantages in terms of cost,hardware complexity,implementation,and reliability.This paper discusses the principles and challenges of using generator current signals for prognostic condition monitoring of wind turbine drivetrains and presents an overview of recent advancements in this area.