Abstract
Several current control concepts for non-isolated interleaved DC-DC converters are systematically evaluated in terms of their dynamic and steady state performance, based on defined performance evaluation indicators. Various current control structures suitable for multi-phase interleaved systems are studied: i) a conventional PI controller with a single update per switching period, ii) a PI controller with a fast execution rate, equal to the sampling frequency instead of the switching frequency iii) a LQR-based state feedback controller (SFC), iv) a model predictive controller (MPC), and v) an adaptive hybrid controller that consists of a hysteretic controller during transient and a PI controller during steady state. Each of these control structures is optimized based on the same multi-objective optimization routine and a defined cost function. After the optimal controller design for each control structure is identified, the optimized designs are compared to identify the advantages and disadvantages of each structure. Additionally, a high current prototype current source based on a multi-phase interleaved converter with 6 interleaved modules switching at 60kHz is used to verify the most promising control structures, the developed models, and the results presented in this paper. Among the different studied structures, the adaptive hybrid controller is shown to exhibit the best performance to step transients and the MPC shows great potential following arbitrary waveforms, but also striking shortcomings in the presence of measurement noise.
Highlights
High bandwidth and precise current sources with the ability to deliver step-like as well as arbitrary/controllable current waveforms are emerging nowadays, finding a broad spectrum of applications, such as power hardware-in-the-loop (P-HiL) simulations [1]–[3], driving accelerator magnets for medical and fusion energy applications [4]–[7] or testing equipment for HVDC grids [8], [9]
Pareto-front optimizations of the different schemes showed that the adaptive hybrid controller has the ability to perform close to the ideal controller when following step transients
The PI controller with a fast update rate results in an increased performance of at least 10% compared to the conventional PI controller implementation with a single update rate
Summary
High bandwidth and precise current sources with the ability to deliver step-like as well as arbitrary/controllable current waveforms are emerging nowadays, finding a broad spectrum of applications, such as power hardware-in-the-loop (P-HiL) simulations [1]–[3], driving accelerator magnets for medical and fusion energy applications [4]–[7] or testing equipment for HVDC grids [8], [9]. In its conventional form, it suffers from i) switching frequency jittering, that results in imprecise interleaving and increased ripple, ii) inaccurate reference tracking, and iii) imbalanced current sharing between the phases, in the presence of parameter mismatch [21], [22] To overcome these issues, an adaptive hybrid control scheme for interleaved converters is presented in [23], making use of the hysteretic controller during fast transients, and smoothly transitions to a PI controller once the steady state is reached. These advancements enable the use of advanced control schemes coupled with high sampling frequencies and fast processing speeds, without increasing the cost to unacceptable levels These advancements can potentially disrupt the optimization results and reshape the picture of what is achievable, highlighting again the need for a detailed comparative evaluation.
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