Electrical Submersible Pumps: A System Modeling Approach for Power Quality Analysis With Variable Frequency Drives

What is it about?

This article proposes a high-level engineering guide to develop an integrated system model for power quality analysis in electrical submersible pump (ESP) applications with variable frequency drives (VFDs). Such analyses are troublesome in the industry due to the complexity of these systems. In this article, simple steps to perform system integration analyses of such arrangements, including torsional analysis, are developed. A simplified VFD-ESP model suitable for coupled electrical and mechanical analysis in steady state is proposed in all their configurations of practical interest. Such a model can be easily implemented in common simulation software, significantly reducing engineering efforts for implementation and analysis. The focus of the proposed model is the prediction of ESP failures that might result from a poor power quality caused by VFDs. Analytical expressions of different types of harmonics in these systems, as well as their accurate locations in the frequency domain, including their interharmonics and common-mode harmonics, are derived for this purpose. The effectiveness of the proposed model is verified through offline and real-time hybrid simulation results. Finally, a comparison between simulation results obtained using the proposed model and measurements collected on a down-scale laboratory prototype is carried out to demonstrate the accuracy of the suggested modeling approach

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Why is it important?

This article proposes a simple modeling approach to easily investigate VFD PQ issues in ESP systems supplied through a long transmission cable. A simplified VFD-ESP model suitable for coupled electrical and mechanical resonance analysis in steady-state is developed in all their configurations of practical interest. It is an easy-to-use tool for practicing engineers involved in the design, selection, integration, and retrofit of ESP components and systems to understand how VFDs can excite either the electrical resonance modes of a transmission cable or mechanical resonance modes of a rotating shaft in their systems. In this sense, it can help to avoid ESP failures that might result from a poor PQ caused by VFDs. Analytical expressions of different types of harmonics in these systems, including their interharmonics and other types of applicable common-mode harmonics, are derived to support such engineering studies and analyses. Offline and RTHS results both in time and frequency domains, as well as experimental results, have been provided to demonstrate the relevance of the proposed modeling approach

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