Abstract
When the power source of a voltage source converter (VSC) station at the sending end solely depends on wind power generation, the station is operating in an islanding mode. In this case, the power fluctuation of the wind power will be entirely transmitted to the receiving-end grid. A self-regulation scheme of power fluctuation is proposed in this paper to solve this problem. Firstly, we investigated the short-time variability characteristic of the wind power in a multi-terminal direct-current (MTDC) project in China. Then we designed a virtual frequency (VF) control strategy at the VSC station based on the common constant voltage constant frequency (CVCF) control of VSC station. By cooperating with the primary frequency regulation (PFR) control at the wind farms, the self-regulation of active power pooling at the VSC station was realized. The control parameters of VF and PFR control were carefully settled through the steady-state analysis of the MTDC grid. The self-regulation effect had been demonstrated by a twenty-four-hour simulation. The results showed that the proposed scheme could effectively smoothen the power fluctuation.
Highlights
As the most mature and promising renewable energy source, wind power generation has maintained strong momentum of development in recent years
After analyzing the variability characteristics of wind power in this area, a virtual frequency (VF) control strategy was developed on top of the traditional constant voltage constant frequency (CVCF) control to make the frequency of AC power grid in the islanded system vary with the active power of wind power generation
On the other hand, when P is greater than Pplan, with VF control the frequency of the isolated power system increases by a positive ∆ f and primary frequency regulation (PFR) reacts to reduce the power generation at the wind farms the frequency could decline to some extent
Summary
As the most mature and promising renewable energy source, wind power generation has maintained strong momentum of development in recent years. The voltage source converter (VSC)-based high voltage direct current (HVDC) transmission, compared to the common AC transmission and conventional DC transmission, has unique and irreplaceable advantages in delivering renewable energy [1,2,3,4] It has a high degree of controllability in power delivery. After analyzing the variability characteristics of wind power in this area, a virtual frequency (VF) control strategy was developed on top of the traditional CVCF control to make the frequency of AC power grid in the islanded system vary with the active power of wind power generation This VF control at the VSC station coordinated with the most state-of-the-art primary frequency regulation (PFR) control at the renewable energy station forms our proposed self-regulation scheme for power fluctuation. A twenty-four-hour simulation of the MTDC grid with self-regulation scheme has been run to show the effect of this proposed scheme
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