In dc microgrid, the cascaded dc system has been extensively employed. However, the negative impedance characteristics of the converter may induce system instability. This article proposes an optimized parallel virtual resistance (PVR) based active damping control to improve the stability of the cascade dc system in the dc microgrid. The advantage of this method is that it not only meets the closed-loop dynamic performance of the source converter (SC), but also meets the stability requirements of matching the input impedance of the load converter. The stability range of PVR under full load and its influence on the output impedance of SC in cascade system are determined. Additionally, a large-signal model is constructed by using state-space averaging method to investigate the open-loop stability in the cascaded dc system. The suggested control stability requirements are investigated by using the Lyapunov indirect approach, and a matching PVR is then adopted to ensure system stability. Finally, the performance of the control strategy is verified by establishing a MATLAB simulation and experiment platform.

In a bipolar DC distribution network, the unbalanced load resistance, line resistance and renewable energy source will cause an unbalanced current for each node of the neutral line and lead to its unbalanced voltage. This is a unique power quality problem of bipolar DC distribution networks, which will increase the power loss in the network and lead to overcurrent protection of the neutral line in serious cases. A voltage balancer can be adopted to suppress the unbalanced voltage and current. However, the existing literature does not consider the consistent application of multiple voltage balancers in a multi-node bipolar DC distribution network. This paper creatively proposes a consensus control topology combining primary control and secondary control in a radial multi-node bipolar DC distribution network with voltage balancers. In this paper, the formulas for the positive and negative current and duty cycle of a bipolar DC distribution network with voltage balancers are derived, and improved voltage balancer modeling based on a consensus algorithm is built. The radial multi-node bipolar DC distribution network is established in MATLAB/Simulink. The simulation results compare the consensus control with the traditional droop control and verify the effectiveness of the new control structure with voltage balancers.

With increasing global concern about climate change and environmental pollution, clean power and zero-carbon transportation technologies have emerged as key solutions to address energy challenges. Electric vehicles (EVs) powered by renewable energy sources (RESs) are pivotal in reducing carbon emissions. However, the issue of power quality in RESs cannot be ignored. This paper first analyzes the effects of load, line resistance, and droop coefficient on voltage deviation coefficient and voltage unbalance factor in a bipolar DC microgrid. Subsequently, this paper proposes a distributed coordinated control of distributed RESs to mitigate the impact of large-scale EV integration on the power system. The proposed control approach ensures high power quality at various nodes while supporting RESs for EV charging. The control strategy adapts to dynamic load conditions, enhancing the integration of RESs. Furthermore, a small signal model is constructed to assess its impact on system stability. Finally, the MATLAB/Simulink and experimental platforms are established to validate the precision of the proposed distributed coordinated control scheme across different situations. This research advances zero-carbon transportation and smart grid development, laying a foundation for intelligent urbanization.

Due to the lack of freedom in power flow (PF) control of the meshed bipolar DC distribution grid, the PF of some lines become uncontrollable. Besides, there is a coupling between the poles due to the unbalanced current and line resistance, which may deteriorate the dynamic performance of the control system. To solve the above problems, this paper proposes an unbalanced PF regulation methodology based on a triple active bridge power flow controller (TAB-PFC) and studies the decoupling control of TAB-PFC. This paper analyzes the influence of receiving-end voltage on positive and negative PF and line losses. The expressions of output voltage and line current of TAB-PFC under constant power control are also derived, and the small-signal model of a meshed bipolar DC distribution grid with TAB-PFC is established. On this basis, the decoupling matrix is introduced between the positive and negative control loops to improve the dynamic performance of the control system. A simulation model of meshed bipolar DC distribution grid with TAB-PFC is established in MATLAB/Simulink, and an experimental platform is built. The simulation and experimental results verify the effectiveness of TAB-PFC in restraining unbalanced PF and the effectiveness of the decoupling matrix.