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When several microgrids are interconnected into microgrid cluster (MGC), the network topology of MGC system would be more complex. Traditional hierarchical control based on droop control tends to make full use of all networks so that the costs of energy exchange could be high. Considering the voltage stability and power sharing of MGC system, a distributed cooperative control method based on network topology optimisation for MGC is proposed to control the power flow of multi‐microgrid system. Specially, preliminary Q‐leaning algorithm is utilised with establishment of new adjacency matrices for the distributed cooperative control to decrease the costs. Moreover, multi‐level controls based on consensus protocol are proposed in the distributed cooperative MGC system to eliminate the necessity of a central controller. The adaptive regulation based on the state of charge among the battery groups will be taken as the first‐level control. The second‐level control including the current controller, voltage controller and power controller is implemented among the DGs and a novel third‐level control based on consensus is applied in eliminating the voltage deviation caused by the first‐level control and the second‐level control. The effectiveness of the proposed method is verified through the simulation by simulink. [ABSTRACT FROM AUTHOR]

A layered management and hybrid control strategy based on hybrid automata and random forest for the microgrid is proposed in this study. It is used to realise energy management and multi‐modal coordinated switching of microgrid system to ensure high security, stability and high efficiency. Management and control strategies are implemented through a three‐layer microgrid architecture based on multi‐agent system theory. An energy management strategy is designed for the microgrid system in the upper layer agent structure. A coordinated control strategy is designed in the middle layer agent structure. A local control strategy is designed into the bottom layer agent structure. In the middle layer coordinated control strategy, the hybrid automata is used to characterise the complex logical features of each underlying unit and trigger the switching of working modes according to the condition change. The random forest algorithm is used to analyse the running state and reduce the number of switching. Finally, the simulation results verify the effectiveness of the proposed control strategy in different scenarios. [ABSTRACT FROM AUTHOR]

The event‐triggered hybrid control is proposed in this study to realise multi‐model switching when the microgrid system is operating in the island mode. The hybrid control includes decentralised control strategy and coordinated control strategy. Firstly, control commands in the hybrid control strategy are triggered by the event triggering mechanism including trigger events and trigger conditions. When a trigger condition is met, the corresponding event is triggered to execute the corresponding control command. Secondly, the microgrid system is divided into an upper control layer and a lower execution layer by using the multi‐agent system theory. For the upper control layer, a coordinated control strategy based on decision tree algorithm is designed, which can not only issue switching control commands to the lower execution layer, but also reduce the number of switching, improve system stability, and enrich the control strategy. For the lower execution layer, a decentralised control strategy is designed to realise distributed operation of the underlying units. Finally, the model of hybrid automata of each unit is established to ensure the smooth switching of working modes of each unit. The simulation results verify the effectiveness of the event‐triggered hybrid control strategy for controlling the microgrid. [ABSTRACT FROM AUTHOR]

In order to fully consume renewable energies and schedule demand‐side resources more hierarchically, a double‐deck optimal schedule model of micro‐grid, which connects to power grids and concludes battery energy storage system (BESS), is proposed. Unlike the original peak‐valley time‐of‐use (TOU) price, in the upper layer optimal schedule, the improved TOU price which takes account into the user's satisfaction can express the adjusted loads accurately and the resulting net loads can be treated as a link between upper and lower layer scheduling. For the reason of having no precise model of BESS, the lower model for the goal of minimising the operation cost is solved by action dependent heuristic dynamic programming algorithm that is not relying on the accurate controlled object model. This algorithm is used to obtain the most optimal performance index function and control strategy by the optimal iterative process, which is based on the back propagation neural network used for evaluating the optimal performance index. Analysis of examples and results has been presented to show the effectiveness of the proposed strategies. [ABSTRACT FROM AUTHOR]

Communication data in the communication network of the islanded micro‐grid can be disturbed in many ways, such as data attack or packet loss. To improve the control effect on the voltages and frequencies obtained by droop control of distributed energy resources (DERs) facing communication data disturbance (CDD), a response hierarchical control strategy is proposed in this study. Based on the concept of the cyber physical system, the control structure is divided into two layers: the cyber layer and physical layer. In the cyber layer, firstly, the effect of the CDD on the micro‐grid system is analysed and then, an event‐triggered data compensation method combining the back‐propagation neural network and extreme learning machine is proposed in this layer to solve the problem of the CDD. In the physical layer, firstly, the droop control is used as the primary control to control the voltages and frequencies of DERs and then, a novel virtual leader‐following consensus control method considering time‐delay is proposed in this layer. Also, it is used to complete the secondary control of the voltage and frequency obtained by primary control. In the end, the simulation results confirm the effectiveness of the proposed hierarchical control strategy under CDD. [ABSTRACT FROM AUTHOR]

In order to improve the control effect on voltage and frequency of each distributed energy resource (DER) and improve the stability of the islanded micro‐grid, a novel hierarchical control strategy combined sliding mode control (SMC) and consensus control is proposed in this study. The control structure is divided into two layers: the physical layer and the cyber layer. In the physical layer, in order to improve the dynamic control effect, an improved droop control based on consensus theory with considering packet loss is proposed in this study. And the control can be completed in finite time by selecting the approximate parameters in the controller; in order to improve the stability of voltage loop and current loop, an improved double closed‐loop structure based on the SMC is proposed. Moreover, the control can also be completed in the finite time. In the cyber layer, an event‐triggered SMC‐virtual leader–following consensus protocol is proposed in this study to solve the problem of channel noise (disturbance). For improving the control effect, the protocol is used to complete the secondary control on voltage and frequency of each DER. Finally, the effectiveness of the novel control strategy is verified by simulation results. [ABSTRACT FROM AUTHOR]

Droop control is a common method in the universal microgrid applications. Conventional droop control is unpractical for low‐voltage microgrid, where the line impedance among distributed generation units (DGs) is mainly resistive to generate the active and reactive power of DG is coupled. Besides, accurate reactive power sharing is not achieved due to the voltage deviation of DGs caused by disparate line impedance in microgrid. An improved droop control based on the virtual power source (VPS) and composite virtual impedance, which is constituted by a negative resistance and a negative inductance, is proposed for low‐voltage microgrid. The virtual negative resistance counteracts the line resistance to decouple power. The reactive power sharing accuracy based on the virtual negative inductance and VPSs control increases through analysing the line and virtual voltage drop. Finally, the fractional‐order PID controller is adopted to control the inverter voltage. The optimal controller parameters are obtained by the differential evolution algorithm. To verify the viability and availability of improved control strategy, simulations are carried out on MATLAB/Simulink. [ABSTRACT FROM AUTHOR]

This study proposes a hierarchical hybrid control strategy to ensure stabilisation performance during the micro‐grid operating mode conversion. Designing the hierarchical hybrid control strategy is divided into two stages. In the first stage, the research focuses on constructing a hybrid control scheme, where besides that the storage I unit needs to implement switching control strategy by means of an upper‐level switching controller, the storage II unit that acts as a master unit also needs to be switched between two kinds of control modes including voltage–frequency droop control and PQ control in response to different micro‐grid operating modes, and other slave distributed generation (DG) units operate in PQ control mode all the time. Moreover, during the operation mode conversion, according to the assessment indexes regarding voltage and frequency, the upper‐level switching controller determines whether and when to send switching commands to the master DG unit. In the second stage, the research focuses on designing the hierarchical control strategies in the PQ control mode and the voltage–frequency droop control mode, as well as designing the upper‐level switching controller to guarantee the stabilisation performance of the micro‐grid during operation mode conversion. In the PQ control mode, all controllers are designed as a fractional order proportional–integral–derivative (FOPID) controller. Finally, the validity of the proposed hybrid control strategy is demonstrated by means of simulation results. [ABSTRACT FROM AUTHOR]

In this Letter, a novel voltage regulation method is proposed for ensuring voltage security in photovoltaic (PV) distribution systems. It is a two‐level regulation to reduce overall voltage deviation (VDE) and voltage difference (VDI). Firstly, evaluation indexes for VDE and VDI are built. Then, in order to reduce VDE, primary regulation by sensitivities‐based power compensation is developed. Furthermore, in order to reduce VDI, secondary regulation by using PI coordinate compensator is built. Compared with other methods, the proposed method can achieve high regulation accuracy. The effectiveness is verified in a PV platform. [ABSTRACT FROM AUTHOR]

In this study, a two‐hierarchical decentralised coordinated control scheme based on the multi‐agent system (MAS) is proposed to improve the security and the stability of the microgrid. The coordinated switching control strategies are constructed in upper level agent to ensure the microgrid security. The making process of the coordinated switching control strategies is regarded as searching the optimal switching operation mode by means of designing constraint violation function and colour Petri‐net, so that the operation mode of the microgrid can be switched during larger power unbalance. The decentralised continuous control is designed by integrating the outer loop droop controller with the inner loop prescribed performance controller in the lower level unit agents to guarantee its unit system stability. Finally, the simulation results demonstrate the effectiveness of the decentralised coordination control based on MAS. [ABSTRACT FROM AUTHOR]

This paper studied the distributed optimal frequency regulation for multiple power generations in an isolated microgrid under limited communication resource. The event-triggered mechanism is introduced in the construction of the regulation algorithm. Each power generation in the microgrid only transmits its own information to its neighbors through a communication network when the event-triggered condition is satisfied, and the communication burden can be reduced significantly. Moreover, Zeno behavior is excluded to make the event-triggered regulation algorithm reasonable and realistic for practical microgrids. The proposed regulation method can restore the frequency and retain the economic efficiency simultaneously when some disturbances occur in isolated microgrids. The experimental result shows the effectiveness of the theoretical method. [ABSTRACT FROM AUTHOR]