An Integrated High-Quality Cooperative Control Strategy of DC Microgrids
Zhang Hao1, Li Yu1, Yin Yafei1, Li Zhen1,2, Zhang Zhenbin1,2
1. School of Electrical Engineering Shandong University Jinan 250061 China; 2. Shenzhen Research Institute of Shandong University Shenzhen 518047 China
Abstract The cooperative control of DC microgrids based on consensus algorithm can make each distributed generation to achieve voltage regulation and power sharing by capacity, which only required key operating information of neighboring units. But most of the existing control strategies have the following problems: (1) Each distributed node needs to obtain the voltage and current information of neighboring nodes from the communication network, which requires higher communication bandwidth. (2)The complex coupling of two PI controllers which are used to achieve the control objectives of voltage and power respectively makes the setting of controller parameters tedious. (3) The voltage observer based on classical consensus algorithm need to follow the initialization conditions strictly and cannot guarantee the plug and play characteristics of the system. Therefore, to address these issues, this paper proposes an integrated high-quality cooperative control strategy of DC microgrids. Firstly, the voltage and current regulators are integrated, which can achieve control goals more simply and drop out the need for current information of neighboring units. Secondly, the improved consensus algorithm is adopted to make the system robust to the measurement noise and initialization conditions. Thirdly, considering the contradiction between system instability under high open-loop gain and poor control performance under low open-loop gain, a hyperbolic tangent-proportional nonlinear controller is proposed to enlarge the parameter selection range and improve the control quality of the system. Finally, a global model of the DC microgrid considering the cyber network is established in the form of a state-space-model. The input-to-state stability analysis is carried out. Meanwhile the influence of controller parameters on system stability is illustrated in the round. The hardware-in-the-loop (HiL) experiment verifies the control effect of the proposed method and the performance of the proposed method under various working conditions, including communication failure, the plug and play characteristics, local load changes, different communication network topologies. The results show that the proposed cooperative control strategy can realize accurate voltage regulation and power sharing within 0.3 s. In the face of bus load or local load changes, it shows good transient performance and steady state accuracy. Meanwhile, because of the proposed hyperbolic tangent-proportional nonlinear control, the initial shock of system adjustment has been effectively suppressed and the steady-state accuracy of the system has been effectively improved. The voltage observer with consensus algorithm can greatly reduce the influence of measurement noise and doesn't require strict initialization. When any node enters or exits the system, the system can still redistribute power automatically and accurately. In addition, the proposed method is resilient to communication failure and different communication network topologies. All the above results show the superiority of the proposed method. The conclusion of this paper can be drawn as follows: (1) The proposed voltage observer with improved consensus algorithm is robust to measurement noise and initialization conditions, which can improve the quality of control and guarantee the plug and play capacity. (2) The proposed cooperative control strategy can realize accurately voltage regulation and power sharing. Compared with the classic control method, it can reduce communication traffic half in theory. (3) The proposed hyperbolic tangent-proportional nonlinear controller can alleviate the contradiction between control quality and system stability. It is simple and effective to improve the control quality.
Zhang Hao,Li Yu,Yin Yafei等. An Integrated High-Quality Cooperative Control Strategy of DC Microgrids[J]. Transactions of China Electrotechnical Society, 2023, 38(23): 6345-6358.
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2023, Vol. 38 
