With the increasing penetration of renewable energy, the integration of power electronic equipment has fundamentally re-shaped the dynamic characteristics of modern power grids. Due to the lack of support from the main grid, islanded microgrids (MGs) are prone to losing synchronization stability under large signal disturbances. Existing stability studies often focus on single-inverter systems, which have limited performance in multi-inverter scenarios due to the extended computational burden. Therefore, this paper proposes a method for evaluating the large signal stability of MGs composed of grid-forming (GFM) inverters based on the networked oscillator model. Firstly, the equivalent oscillator model of the GFM inverter is established to accurately characterize both the inherent and interactive dynamics of a single GFM inverter, thereby enabling the construction of a networked oscillator model for islanded MGs with a general topological structure. The large signal stability analysis of the system is then carried out analytically, and the frequency stability domain is explicitly derived. Finally, the effectiveness of the proposed method is verified through time-domain simulation and Controller Hardware-in-the-Loop (C-HIL) experiments.

Virtual Power Plants (VPPs) have gained prominence as an effective approach to enhance renewable energy utilization and optimize power market mechanisms in recent years. To address the inherent uncertainties of renewable energy generation and improve the economic performance of VPPs in electricity markets, this paper proposes a two-stage economic dispatch model that explicitly incorporates renewable energy output forecasting errors. The day-ahead stage employs a data-driven chance-constrained approach to handle renewable uncertainties, ensuring reliable day-ahead scheduling. The real-time stage compensates for deviations between actual and scheduled generation outputs. The proposed coordinated two-stage optimization achieves optimal day-ahead bidding strategies that enhance VPP profitability and reduce real-time power deviations, as validated through case studies.

Distributed electric propulsion (DEP) has been proven to be the next-generation propulsion technology for full-electric aircraft and all-electric aircraft. To take advantage of the redundancy of the DEP system, the distributed control method and its related performance have been extensively studied. However, due to the characteristics of the distributed structure, faults of a single agent could propagate through the communication links, making the whole system fail. This paper proposes a fault-tolerant control method to stabilize the DEP system when an inverter single-phase open-circuit fault occurs. The proposed method adopts a distributed structure and could effectively depress the fluctuation of the rotation speed of each thruster without additional requirements for the increase in hardware amount and computational performance. Controller-hardware-in-the-loop (C-HIL) experiments have been conducted, and the corresponding results validate the effectiveness of the proposed control method.

This article studies how to solve the energy management (EM) problem while balancing economy and security. Firstly, a defense scheme is developed to relieve the negative effects of denial-of-service (DoS) attacks. Secondly, a secure predefined-time distributed EM algorithm via the time-base generator (TBG) is devised which can be suitable for directed graphs, and sensitive information is decomposed into two dynamic variables for key information privacy preservation. Thirdly, a dynamic event-triggered (DET) mechanism is proposed to economize communication resources. By constructing the Lyapunov energy function, it is proven that the convergence time of the devised distributed algorithm can be predefined by users independent of initial conditions. Zeno behavior is proven to be avoided, which exhibits the effectiveness of the DET approach. At last, the simulations are given to show the validity and advancement of the designed secure distributed algorithm.Note to Practitioners—With the deep integration of the cyber layer and physical layer in microgrids, the microgrid system is facing the threat of attacks. This article considers a typical cyber attack, a DoS attack, and the privacy-preserving problem. For solving the EM problem considering cyber security, a DoS attack defense scheme and a novel state decomposition mechanism have been proposed. After a DoS attack occurs, the microgrid system has an urgent need for EM fast recovery, while frequent information exchange can lead to unnecessary communication bandwidth occupation. Hence, a predefined-time distributed optimization approach based on the DET method is devised to achieve fast EM after DoS attacks and relieve the communication burden. The article adopts the TBG function to design dynamic gain which allows practitioners to flexibly adjust the convergence speed of the EM algorithm in practical applications.

This paper proposes a novel motor synchronization method for unmanned aerial vehicles with distributed electric propulsion system (DEP-UAV). Compared with conventional aircraft with a single motor, propeller management in DEP-UAV is more delicate and represents unique challenges. Specifically, motors with asynchronous rotating speed would generate asymmetric thrusts along the DEP-UAV, which could result in undesired moment imbalance on the aircraft. A model-based distributed control algorithm is developed, which synchronizes the rotating speed of multiple motors to the desired value. The proposed method runs on a sparse communication network, which avoids the system's single-point-of-failure; additionally, the control gains are customized regarding each motor's mechanical characteristics, which ensures the system's dynamic performance without introducing excessive computational cost. The convergence of the proposed method has been analytically proved and its dynamic performance has been validated using a Controller Hardware-in-the-Loop (C-HIL) testbed for DEP-UAV application.

The increasing penetration of grid-forming inverters has significantly complicated the operating characteristics of modern power grids, which calls for reduced-order models that preserves the system's main responses for large-scale analysis. This paper presents a model reduction approach to study the dynamic responses of inverter-dominated networked microgrids (MGs) under disturbance. Coherency-based aggregation technique is used to identify the study area and external area. The study area is modeled in detail while the external area is successively simplified. Specifically, the reduced-order model of the external area is first simplified by developing reduced-order models of inverter and network; it is then further simplified using linear truncation. To replicate the interactions between the two areas, the external area is aggregated into a controllable voltage source whose operating states are collaboratively determined by the states from both areas. The developed reduced-order model represents a closed-loop simulation that combines both linear model reduction for reduced system dimensions and detailed nonlinear model for better accuracy. At last, the performance of the developed model reduction approach is validated using time-domain simulation.

Dynamic microgrids (MG)have shown great potential in distribution system restoration as they could be frequently and actively reconfigured as per request from system operator. MGs usually have smaller inertia compared to conventional power systems thus require more delicate controller for operation safety. In addition, most distribution systems have unbalanced configurations which requires dedicated regulations on system operation states in both positive and negative sequence. This paper proposes a distributed secondary control strategy for unbalanced dynamic MGs operation. System frequency and voltage regulation are constantly enabled, along with voltage unbalance (VU)mitigation on critical load buses. The proposed control strategy provides automatic management of DGs within the same MG and seamless system transition as reconfiguration is requested. Detailed controller designs for both positive and negative sequence regulations are presented. Small-signal stability analysis of the proposed controller is derived and its dynamic performances are validated using MATLAB/Simulink.

Inductor filter is widely used in grid-tied inverters. If an inverter with inductor filter operates in weak grid condition, voltage measurement error may exist due to the voltage sensor delay and the voltage drop on grid impedance. This can further lead to errors in the phase lock loop (PLL) and even system instability. In this paper, we analyze the voltage measurement error in weak grid condition in detail. All the essential elements in the measurement chain are considered. Analysis shows large DC offset and harmonic components may exist in the sampled voltage. To improve the PLL performance in weak grid condition, a PLL with extra DC offset and 2nd order harmonic rejection capability is presented. Further, the inverter current controller is designed considering grid impedance and grid harmonics. Experiments are performed to verify the presented method.