Abstract
Some innovative works have been done to probabilistic power flow (PPF) analysis for hybrid HVAC and LCC-VSC HVDC system in this paper. Firstly, a unified method considering precise model of converters is proposed to solve a general deterministic power flow (DPF) calculation including hybrid LCC (Line Current Converter) and VSC (Voltage Source Converter), the pure VSC-MTDC (Voltage Source Converter-Multiple Terminal Direct Current) and pure LCC system. Meanwhile, with a large amount of renewable energy sources integrated to the main grid through DC grids, it will impose a stochastic impact on the secure operation of such hybrid AC/DC grids. Therefore, it becomes necessary to model the probabilistic uncertainties and analyze their effects on the operation of hybrid AC/DC systems under different control modes. Nevertheless, most power flow analysis methods for hybrid AC/DC system are still deterministic in nature. Therefore, a probabilistic method based on the combination of Nataf transformation and Latin hypercube sampling (LHS) is developed and proposed to solve this complex PPF problem in an efficient manner, which considers correlated various probabilistic uncertainties, e.g. wind speeds, solar radiations and loads following different types of probability distribution. Finally, the effectiveness of the unified DPF method is validated in a modified IEEE 14-bus system, while the proposed PPF is verified in a modified IEEE 118-bus system and the effects of uncertainties on the diverse operation modes of hybrid AC/DC grids are discussed as well.
Highlights
With the increasing worldwide concerns on environmental pollution, global warming, energy and resources crisis, the topics on both smart grid and renewable energy generation have become very attractive most recently [1]
PROBABILISTIC POWER FLOW ANALYSIS FOR HYBRID AC/DC SYSTEM BASED ON Latin hypercube sampling (LHS) AND NATAF TRANSFORMATION In this sub-section, the computational accuracy and effectiveness of the proposed probabilistic power flow (PPF) for hybrid HVAC and LCC-VSC will be evaluated considering the correlation of various random variables subject to the different types of probability distributions
The results above turn out that the errors of all state variables are lower than 5%, which entails the good accuracy and robustness of LHS-1000 with respect to handling various correlation levels for complex hybrid AC/DC system
Summary
With the increasing worldwide concerns on environmental pollution, global warming, energy and resources crisis, the topics on both smart grid and renewable energy generation have become very attractive most recently [1]. Only a few studies have been directed towards the more practical power flow analysis of hybrid AC/DC system incorporating both LCC and VSC. The major contributions cover the followings: 1) A unified deterministic power flow algorithm for hybrid HVAC and LCC-VSC HVDC system with considering coordinated control is proposed in this paper, in which the precise model of converter is considered as well. This facilitates the power flow calculation for various control modes, arbitrary topologies and different types of converter station in such hybrid AC/DC grids.
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