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In the last decade, high performance multi-core processor designs have followed an increase in number of cores, interfaces, heterogeneity and System-on-chip (SoC) complexity. HPC applications also require tailored chip designs with specific operating points and performance indexes. In this scenario, an advanced and configurable Power Controller System (PCS) is necessary to meet power and thermal constraints, without the necessity of static ultra-conservative margins on the operating points. In this paper, we propose an open-source PCS design, based on a parallel ultra-low power microcontroller with RISC-V cores, and an open-source software environment based on a Real-time operating system (RTOS) with a configurable Powerthermal control algorithm. Considering a 1ms control interval, the overhead of the RTOS is about 6% of the cycles in the nominal case. The control algorithm is able to limit temperature and power consumption within given bounds, while maximizing performance. The PCS is able to control up to 76 different cores/computing units with headroom for larger core counts.

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In this brief, a plug-in unit is presented to manage control voltage saturation and maximum current limit in shunt active filters (SAFs), where unconstrained control algorithms are already defined. The proposed unit extends the operating region of such devices, i.e., under large transients and overload conditions, with performance guarantees. Therefore, improved robustness, availability, and composability of SAFs are obtained. The solution is composed of two parts. An antiwindup (AW) unit is defined to deal with control input saturation by modifying the current references through a suitably designed additional dynamics. In addition, a current saturation strategy is formulated. Again the current reference is modified, accounting for the limitations of the system, augmented with the AW scheme. The approach is valid for any kind of unconstrained controller adopted to steer SAFs. Here, results are presented considering an internal-model-based current controller. Simulation and experimental tests confirm the effectiveness of the method.

In this chapter some results related to Shunt Active Filters (SAFs) and obtained by the authors and some coauthors are reported. SAFs are complex power electronics equipments adopted to compensate for current harmonic pollution in electric mains, due to nonlinear loads. By using a proper "floating" capacitor as energy reservoir, the SAF purpose is to inject in the line grid currents canceling the polluting harmonics. Control algorithms play a key role for such devices and, in general, in many power electronics applications. Moreover, systems theory is crucial, since it is the mathematical tool that enables a deep understanding of the involved dynamics of such systems, allowing a correct dimensioning, beside an effective control. As a matter of facts, current injection objective can be straightforwardly formulated as an output tracking control problem. In this fashion, the structural and insidious marginally-stable internal/zero dynamics of SAFs can be immediately highlighted and characterized in terms of sizing and control issues. For what concerns the control design strictly, time-scale separation among output and internal dynamics can be effectively exploited to split the control design in different stages that can be later aggregated, by using singular perturbation analysis. In addition, for robust asymptotic output tracking the Internal Model Principle is adopted.In authors' opinion, SAF case is an illustrative example of common issues in dimensioning and control of complex power electronics equipments, hence the proposed design approach can be generalized for such class of systems (e.g. large-power electric drives; generators and converters, particularly for renewable energies; Uninterruptible Power Supplies, UPS, and power supplies for special applications as particle accelerators). Remarkable the role of "system theory approach" in enlightening crucial sizing issues, this fact strongly testifies how relevant the "control viewpoint" is in all the fields of engineering, particularly when complex dynamic behavior is requested.The presented chapter has been invited for possible publication (after a review process) in the book "Robust Control / Book 1", by INTECH (www.intechweb.org).

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