A Simple Self-Tuning Resonant Control Approach for Power Converters Connected to Micro-Grids With Distorted Voltage Conditions

Abstract

Over the last few decades, the consolidated goal of reducing greenhouse gasses has increased the relevance of renewable energy research, electromobility, energy storage, and distributed generation, micro-grids, among others. Micro-grids, systems working in islanding mode, are particular cases where some disadvantages are present due to the wide variations which may appear across their electrical quantities. Variations on the voltage amplitude and the frequency are intrinsic in the operation of weak grids, because they have low inertia and therefore the load must be able to cope with these variations, otherwise loads may trip electrical system protection. Particularly, on power electronic drives, these frequency deviations will lead to increased system nonlinearities, entailing a more critical controller design. To overcome these issues, this paper presents an implementation of a resonant controller with self-tuned gains. The strategy imposes a constant sampling time which allows these controllers to be used in variable frequency environments. In addition, the computational capacity required for the digital board is also considered. The simulated and experimental results provided demonstrate the good performance of this proposal. INDEX TERMS Resonant control, variable frequency environment, micro-grids. I. INTRODUCTION A. Research gap Power Generation has gained popularity in recent years due to the need to generate electric power in alternate directions and from varying kinds of sources. [1], [2]. However, power management for these systems results in a difficult task, as some sources may be working at the maximum power point of injection regardless of the actual power consumption, for example, renewable energies. Therefore, power generation and power consumption may differ, resulting in the global system being out of balance [3]. This problem becomes critical when power systems are small micro-grids, which are usually noted as being low inertia systems. In these cases, ineffective power management leads to variations on the voltage amplitude, mainly associated to the reactive power, and frequency variations, due to active power regulation. In addition, weak grid systems will feature these issues when large loads are either connected or disconnected, making the voltage vary in amplitude and frequency, which are typical occurrences in aircraft and ship power systems [4]-[6]. Electric devices connected to these kinds of sources should be robust under these variations, thus helping to hold the system stability and avoid tripping the inbuilt protections.

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Power Converter Resonant Control for an Unbalanced and Non-Constant Frequency Supply

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