Abstract
In a multiterminal DC (MTDC) system with a large number of different types of energy storage devices, the AC terminals and the energy storage devices need to cooperate to maintain the stability of the DC bus voltage. Due to the difference in the dynamic and static power capability of each energy storage unit, the dynamic and static power should be distributed separately. To solve the above problems, an adaptive droop control strategy based on the dynamic and static power decoupling is proposed in this paper. The impact of the virtual impedance values on the dynamic and static power flows between the DC voltage regulating terminals operating with the RC droop method is analyzed. Through optimized virtual capacitance and adaptive virtual resistance, the dynamic power and static power can be distributed according to the PCS capacity and the available charge–discharge battery capacity, respectively. In addition, a simple secondary control method is adopted to compensate the static deviation of the DC bus voltage. Finally, a six-terminal MTDC system model is established in Matlab/Simulink, and the simulation results verify the feasibility and effectiveness of the proposed control strategy.
Highlights
A multiterminal DC (MTDC) system has become a research hotspot because of its advantages such as easy access of energy storage devices, strong power regulation ability, easy realization of power flow reversal, flexible transmission mode, and reliable power supply (Zheng et al, 2020a; Zheng et al, 2020b)
For an MTDC system with high-capacity energy storage, this paper proposes an improved RC droop control with adaptive virtual resistance, which improves the dynamic and static power distribution performance and the system extendibility
In order to verify the effectiveness of the proposed control strategy, a six-terminal MTDC system with high-capacity energy storage is built in Matlab/Simulink as shown in Figures 3, 6, respectively
Summary
A multiterminal DC (MTDC) system has become a research hotspot because of its advantages such as easy access of energy storage devices, strong power regulation ability, easy realization of power flow reversal, flexible transmission mode, and reliable power supply (Zheng et al, 2020a; Zheng et al, 2020b). For an MTDC system with high-capacity energy storage, this paper proposes an improved RC droop control with adaptive virtual resistance, which improves the dynamic and static power distribution performance and the system extendibility. 2) The upper RC droop control strategy generates voltage regulation commands of each unified voltage source model, separates the system disturbance power into dynamic and static components, and distributes them reasonably among regulation terminals. Because the capacitance is equivalent to the open circuit, the resistance determines the static current distribution of each unit In this way, the dynamic and static decoupling separation of disturbance power can be realized, and it is distributed according to the design parameters of virtual RC. By using the adaptive strategy proposed in this paper, precise Ri_DC can be obtained and better static power distribution performance can be achieved
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