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This study introduces a distributed secondary control method-based adaptive pinning control for inverter-based distributed generations (DGs) in an isolated microgrid (MG) structure with frequency and voltage compensation and power sharing. Without MG centre controller or energy management system, local DGs’ controllers have no global information of the whole communication network, which is the second smallest eigenvalue of the Laplacian matrix. In practice, the large coupling weight gains are mostly selected. However, a sufficient large coupling weight may cause instability. It is difficult to choose the coupling weight in the fully distributed complex network. To solve the above problems, the authors investigate a pinning control for synchronisation using the local adaptive pinning algorithm on coupling weight gains. The proposed method has the advantage that the consensus controller design is independent of the Laplacian matrix associated with the communication network. And the collective dynamics of the communication network can be adjusted to steady states without global information. However, the adaptive pinning control scheme is not suitable for the multi-disturbance situation, which will accumulate the coupling weight and even cause integral saturation. Therefore, an improved strategy is proposed to adapt to the load changing conditions for islanded MGs.

Multiple nearby isolated microgrids (MGs) can be interconnected to become multi-MGs (MMGs) and meet larger bulk power demands, thus improving reliability/security of MMGs and reducing the power supply investment costs. However, a multi-layer control structure and complex communication network are inevitable, which increase communication delays and complicate the control structure. To solve this problem, this article introduces a distributed secondary control (DSC) based on cluster consensus of inhibitory coupling with a power limit scheme. Compared with an inter-cluster communication coupling structure, the communication channels of the proposed scheme are minimised to simplify network topology, decrease the communication delays and control dimensions. The proposed control strategy reaches multi-valued consensus states for accurate active/reactive power sharing in different MGs. Furthermore, active/reactive power overloading in a MG cluster is discussed under an inhibitory coupling configuration. Based on the power limit scheme, each distributed generator (DG) of the overloaded MG is controlled to generate power within the rated power range for high local autonomy. In addition, an adaptive virtual impedance control is introduced to decrease voltage deviations between DGs. The analytical results are verified by a simulation in MATLAB/Simulink.

Tedious adjustment of the weighting factor restricts the wide application of conventional model predictive torque control (MPTC) for induction motors (IMs) in practice. To solve this problem, this study introduces a new variable R (reactive torque) to control the flux of IM, which is the dual of torque T , with radial orientation and in relation to reactive power. Then, a novel MPTC strategy based on variable R and torque T is proposed and named RT-MPC. Compared with conventional MPTC, RT-MPC uses a pair of variables with the same dimensions and time scales instead of the torque and flux amplitude in MPTC. This approach eliminates the weighting factor of the cost function, unifies the time scales of control variables, and avoids prediction of rotor flux at the ( k + 2) instant. Simulation and experimental results show that RT-MPC can avoid the weighting factor, reduce switching frequency, and reduce control complexity. RT-MPC can also maintain excellent dynamic and steady-state performance similar to conventional MPTC. Hence, the proposed method is expected to be more practical.