This paper proposes a novel decentralized control strategy for multiparallel grid-forming distributed generations (DGs) in an islanded microgrid. Different from most existing droop-based hierarchical control methods, the proposed scheme imposes a fixed system frequency that is independent of the load conditions. Additionally, a proper point of common coupling (PCC) voltage amplitude maintaining and proportional power sharing can be simultaneously achieved when dealing with variations in the load and DGs plug in/off. The transient performance of the system, as well as the power supply reliability, can be improved, as no extra restoration control layer or communications between the inverters are needed. Furthermore, the power sharing ratio among DG units can be changed online without affecting the voltage regulation performance, which enhances the power management flexibility. The PCC voltage regulation and the power sharing performance of the proposed control strategy are ensured via the Lyapunov method. Finally, the effectiveness and practicability of the proposed approach are verified through real-time simulations and hardware experimental tests.

This paper presents the design of a filtered tracking error (FTE)-based robust current controller for three-phase grid- tied inverters interfacing distributed renewable resources (DERs) into the grid. An uncertainty and disturbance modeling based control law is developed for achieving the robustness against non- ideal grid conditions including the grid impedance variations, grid voltage harmonics and fluctuations in grid voltage magnitude (symmetrical/ asymmetrical), frequency and phase. The proposed controller is shown to have superior current tracking performance to directly control the current injected into the grid being pure sinusoidal and three-phase balanced. In addition, high dynamic and tracking performance can be further ensured since all the phase locked loops (PLLs) and multi-loop controllers are eliminated, which also delivers the advantage of a simple implementation. Especially, the system stability is proven by using the Lyapunov function. Both simulation and hardware in the loop (HIL) experimental results of the proposed robust controller, as well as the proportional-integral (PI) controller and the parallel proportional-resonant (PR) controller, are given and compared, which validates the performance and effectiveness of the proposed control strategy.

For an islanded micro-grid with a high penetration of photovoltaic (PV) power generators, the low inertia reserve and the maximum peak power tracking control may increase the difficulty of maintaining the system’s supply–demand balance, and cause frequency instability, especially when the available generation is excessive. This will require changes in the way the PV inverter is controlled. In this paper, a virtual inertia frequency control (VIFC) strategy is proposed to let the two-stage PV inverters emulate inertia and support the system frequency with a timely response (e.g., inertia response), and the required power for inertia emulation is obtained from both the DC-link capacitor and the PV reserved energy. As the rate of the system frequency change can be reduced with the inertia increase, the proposed method can mitigate the frequency contingency event before the superior-level coordination control is enabled for the frequency restoration. The simulation results demonstrate the effectiveness of the proposed method.

A decentralized control scheme based on backstepping design is proposed in this paper for the grid converters of a multi-terminal dc power integration system. With the proposed method, dc bus voltage can be accurately maintained together by several converters through appropriately adjusting their transmitted power according to the power sharing ratio. The system structure is presented and its dynamic model is formulated. The decentralized control laws of the grid converters are developed step by step by designing appropriate Lyapunov functions. The dc bus voltage control and the power sharing performance of the proposed control method are evaluated both under the system normal condition and converter fault condition. Finally, the effectiveness of the proposed scheme is validated through the real-time simulations on NI-PXI platform.

The idea of ‘energy router’ (ER) is put forward as a critical application of the energy Internet (EI), especially in the new generation of electric power system to fulfil the power management and to deal with the integration of massive distributed generations. Furthermore, AC/DC hybrid network becomes a kind of development trend since it can improve the power quality and efficiency compared with adding converters for DC loads. This article proposes a decentralised control method for multi‐port converter (MPC)‐based ERs to achieve flexible power regulation and ‘plug and play’ operation. With the proposed schemes, DC bus voltage can be maintained together by multi‐ER through appropriately adjusting their transmitted power according to the pre‐set power‐sharing ratio. Furthermore, the sharing ratio can be online changed for flexible power regulation. The stability of the system is ensured by Lyapunov method, detailed simulation results are presented to validate the feasibility of the proposed scheme under different operating conditions.