Direct current (DC) microgrid is characterised by attractive features such as high efficiency, reduced cost and needless for synchronisation. The control and operation of the DC mirogrid become significantly important with the high penetration of distributed energy resources. Therefore, development of an advanced platform for testing control and operation of the DC microgrid has attracted more and more attention nowadays. This study proposes a hardware‐in‐the‐loop (HIL) simulation system as a new method to develop and test control algorithms and operation strategies for the DC microgrid. The proposed HIL simulation system is composed of a RT‐LAB for real‐time simulation, an actual controller under test, a cRIO for coordination control and the DC microgrid management system for optimal operation. Both the actual controller of key research objects and coordination control with different time scales can be tested in the proposed HIL simulation system. Hence, the platform is designed for flexibility and universality. Moreover, configuration and communication of the HIL simulation system are illustrated in this study. Finally, simulation tests are carried out to show the validation of the proposed HIL simulation platform.

Distributed generators using power electronic converter interface have no inherent inertial response similar to that from the rotating mass of conventional synchronous generators. Virtual synchronous generator (VSG) emulates the behavior of the synchronous generator including system inertia to improve system dynamic performance. Unlike a real synchronous generator, using VSG with proper design, the equivalent inertia of the distributed generator can be controlled in a wider range. In this paper, a flexible virtual synchronous generator (FVSG) control strategy is proposed, with adaptive inertia contributing to a fast and smooth inertial response. The frequency change rate is designed as an adaptive inertia coefficient to flexibly accommodate system inertia with frequency fluctuation rate. Compared with the conventional VSG control, based on fixed inertia coefficient, both inertia support and oscillation suppression are achieved in the proposed control scheme. Moreover, the principles of control parameters design are analyzed in details. Thus, the dynamic response of the system frequency can be substantially improved by the FVSG. Both Matlab/Simulink simulations and prototype tests are implemented to validate the proposed FVSG control strategy on improving system dynamic frequency performance.

Permanent magnet synchronous generators (PMSGs) equipped with back‐to‐back grid‐forming converters have the ability to form a 100% renewable energy power grid. Black‐start is the key capability of grid‐forming converters when restoring the system from a blackout. It is necessary for a grid‐forming converter of the PMSG to operate in black‐start and grid‐connected active support modes. This paper investigates an improved damping adaptive grid‐forming (DA‐GFM) control method for PMSG wind turbines to suppress system frequency fluctuations and achieve a smooth black start. The proposed DA‐GFM control introduces the frequency variations and natural constant function to adaptively adjust its damping coefficient in the dynamic operating progress. The implementations and effects of the proposed DA‐GFM control method on the grid‐forming converter are theoretically evaluated. Additionally, the detailed black‐start operation process is completely studied through a microgrid system with two PMSG wind turbines and energy storages. Compared with the conventional grid‐forming control, the proposed control scheme can not only suppress frequency fluctuations better, but also achieve a smooth forming power grid process. Finally, experiment tests on a controller‐level hardware‐in‐the‐loop simulation platform are carried out to validate the proposed control strategy for achieving a smooth black start.

A three-phase isolated ac–dc–dc power supply is widely used in the industrial field due to its attractive features, such as high-power density, modularity for easy expansion and electrical isolation. In high-power application scenarios, it can be realized by multiple ac–dc–dc modules with input-parallel output-parallel mode. However, it has the problems of slow output voltage response and large ripple in some special applications, such as electrophoresis and electroplating. This article investigates an improved adaptive linear active disturbance rejection control with flexible adjustment capability of the bandwidth parameter value for the high-power dc supply to improve the output voltage response speed. To reduce the dc supply ripple, a control strategy is designed for a single module to adaptively adjust the duty cycle compensation according to the output feedback value. When multiple modules are connected in parallel, a hierarchical delay current sharing control strategy for centralized controllers is proposed to make the peaks and valleys of different modules offset each other. Finally, the proposed method is verified by designing a 42 V/12 000 A high-power dc supply, and the results demonstrate that the proposed method is effective in improving the system output voltage response speed and reducing the voltage ripple, which has significant practical engineering application value.

One of the main capabilities of grid‐forming converters is the ability to operate in both islanded and grid‐connected modes. The grid‐forming converters work autonomously and behave as an AC voltage source when they are isolated from the bulk power system. In a grid‐connected mode, it is necessary for them to offer a set of grid‐forming capabilities for enhancing system inertia and strength. A grid‐forming converter may experience significant fluctuations in voltage, current, and frequency when the transition occurs. This paper investigates an improved adaptive model predictive control (AMPC) method for grid‐forming converters to achieve a smooth transition from islanded to grid‐connected mode and balance the contradiction between frequency stability and response speed. The AMPC method uses the angular frequency and phase angle as the performance indicators and introduces the angular frequency variations to adaptively adjust its weight coefficient in the objective function. The implementations and effects of the proposed AMPC method on the grid‐forming converter are theoretically evaluated. Compared to the conventional control, the proposed control scheme can not only suppress voltage, current, and frequency fluctuations, but also achieve a smooth transition. Additionally, the frequency control strategy in the islanded mode is improved for better independent operation. Finally, experiment tests on a controller‐level hardware‐in‐the‐loop simulation platform are carried out to validate the proposed control strategy for achieving a smooth transition.

Virtual synchronous generator (VSG) control for increasing inverter‐based sources is characterized by attractive features such as supporting virtual inertia, flexible design, and enhancing frequency stability. However, the performance and status of each VSG unit lead to differences in the inertial support capabilities. This paper investigates a cooperative adaptive inertial control method for multiple photovoltaic and energy storage units (PV‐ESUs) to improve system inertia distribution capability during transient events. The frequency discrimination of power disturbances is realized through filters, and the operating ranges of different types of energy storage devices are determined. For the coordination problem with each VSG unit under low‐frequency disturbance. The coordination controller, which regulates virtual inertia values by using technique for order preference by similarity to ideal solution (TOPSIS) evaluation algorithm, is proposed to adaptively adjust the inertial output capability of each VSG unit and provide optimized dynamic frequency support to the grid. The state of charge (SOC) of energy storage, converter adjustable capacity, the maximum adjustable output power of the system per unit time, and other influence factors are considered as actual multiple operation constraints. Finally, the effectiveness and engineering application value of the proposed control strategy is verified by the hardware‐in‐the‐loop (HIL) experimental test platform.