Insufficient damping and inertia are the one of the most tough challenges in the grid-connected power system with high penetration of renewable energy resources. Damping correction loop of virtual synchronous generator (VSG) connected to weak damping and high R/X ratio condition is introduced to solve the issues. First, the scheme of the proposed control is implemented in various system operating conditions, and the small-signal model of the proposed control is established. Subsequently, the influence of the damping correction loop on small-signal stability is demonstrated by Bode diagram analysis, and the interaction between reshaped VSG control and power compensation capacity is clarified in three aspects of damping, inertia and synchronization. Furthermore, the optimal design of additional damping and inertia support is provided to suppress the subsynchronous frequency fluctuation of the system, the proposed control method can be easily implemented by directly inserting it into active power control loop of VSG. Finally, the efficiency of the damping correction loop is verified by experiments, the results indicate that 70% reduction of maximum frequency deviation with the proposed control under 20% active power reference step.

This letter proposes a new perspective for the interactive stability mechanism between frequency and dc voltage in a voltage-source converter-based high-voltage direct current (VSC-HVDC) system with virtual inertia control. The system model is first established, providing a new physical insight into dc voltage and frequency stability. It is found that the frequency instability may be caused by the control loop of virtual inertia or the oscillation transfer of dc voltage. Similarly, the dc voltage oscillation can be induced by the inappropriate design of dc voltage control loop or the transfer of the frequency. The complex oscillation coupling mechanism as well as the oscillation transfer essence is clarified physically. Finally, the correctness as well as the feasibility of the theoretical analysis is verified by the hardware-in-loop experiment.

For a hybrid energy storage system consisting of battery and super‐capacitor (SC) in More Electric Aircraft, a decentralised control strategy, which is based on the virtual impedance droop control, can implement the frequency domain allocation of load power avoiding communication delay and a single point of failure. Although the output voltage deviation and state‐of‐charge (SoC) limitation are solved by existing methods, it still suffers from settling time extending. Secondary voltage controls (SVCs) of virtual‐droop‐controlled for battery and SC are proposed to solve the issue. SVC for the output voltage is designed to compensate for the output voltage deviation in the battery converter based on virtual resistance droop control. SC converter, which is controlled by the SVC for input voltage in virtual capacitance droop control, enforces SC SoC back to the initial value and maintains consistent settling time. In this study, a set of detailed design methods for the controller parameters of SVC are developed not only to regulate the output voltage and SoC recovery but also to keep the same settling time. The results of the simulation and experiment validate the effectiveness of the proposed SVC and design method.

In aircraft, the high dc component and even harmonics in the input current of the front-end Vienna rectifier during faults can easily trigger the generator to protect and interrupt the power supply. However, existing fault-tolerance control (FTC) methods cannot effectively reduce them. In this article, first, the impact of an open-circuit fault of a switch on the voltage vector is analyzed. The reason why existing FTC methods fail to improve the half-wave symmetry of input current (HWSIC) is also revealed. Then, a FTC method for improving the HWSIC is proposed. In this method, for areas affected by the fault, the offset voltages injected into the reference voltages are derived in detail. This involves accurately synthesizing the reference voltage vector (RVV) by replacing the infeasible vector with the redundant vector and approximately synthesizing RVV with only two available vectors. For areas unaffected by the fault, the offset voltages injected into the reference voltages are also discussed to achieve a completely symmetrical synthesis style of RVV in the positive and negative half-cycles of the current. As a result, good HWSIC can be obtained. Additionally, the total harmonic distortion of the input current and the ripple of the dc output voltage are reduced. Finally, the effectiveness of the proposed FTC method is verified through experiments.