Abstract
This paper evaluates application feasibility of a Hybrid Multi-terminal HVDC system and wind-thermal-bundled plants simulated in DIgSLIENT PowerFactory environment. The proposed hybrid MTDC system consists of two line-communicated converters (LCC), which are connected to both wind farms and thermal power plants, and one voltage source converter (VSC) at the grid side. Control strategies for each converter are designed to handle this system under different disturbance conditions. Simulation results show that the wind power fluctuation can be compensated by the thermal-generated power. Results demonstrate the effectiveness of the proposed control strategies of the hybrid MTDC system compared to a conventional MTDC system. The proposed scheme combines advantages of both LCC and VSC HVDC systems and provides a new way to transmit wind power over long distances to the main grid.
Highlights
Over the recent years, worldwide demand for energy has been steadily growing
Author in [11] used a two-terminal hybrid high voltage direct current (HVDC) system, which consists of a pulse width modulated current source converter (PWM-CSC) and a line-communicated converters (LCC) to transfer energy from offshore wind farms to onshore grids
This hybrid MTDC system comprises of two LCC rectifiers at the sending end, which are connected to the wind farms and thermal power plants
Summary
Worldwide demand for energy has been steadily growing. It is expected that by the year 2035, renewable sources of energy would be generating more than 25% of world’s electricity, with a quarter of it being contributed by wind power according to the International Energy Agency (IEA) [1]. Thermal power plants, wind farms and load centers may have large distance between them, high voltage direct current (HVDC) technology, including line-commutated converter HVDC (LCC-HVDC), voltage source convertorHVDC (VSC-HVDC) and hybrid HVDC are preferred [4]. Author in [11] used a two-terminal hybrid HVDC system, which consists of a pulse width modulated current source converter (PWM-CSC) and a LCC to transfer energy from offshore wind farms to onshore grids. Due to the stochastic fluctuation of wind speed, wind farms are regarded as a weak AC system [19] This has considerable impact on the stability of the connected power grids. Transient stability of the power system with bundled transmission of wind and thermal power has been studied taking practical requirements into account specific to the Northwest Grid in China, Control strategies and principles of the proposed system have been presented.
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