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Switching-sequence-based control (SBC) laws when designed based on topological switching behavior can have positive effects on slow- and fast-scale dynamics of a power-electronic system (PES). The slow-scale control can encompass fast PES state regulation and tracking, based on predefined objective, while fast-scale control can address differential-mode (DM) and common-mode (CM) spectral-peak energy associated with PES switching operation. Such control laws may offer enhanced programmability to conventional PES design where bulky electromagnetic interference (EMI) filters have been traditionally used to reduce EMI of switching power converters to meet EMI regulatory standards. An EMI filter is always a less programmable solution since it is usually designed for the worst-case EMI mitigation and usually overkill for a PES operating under reduced load condition. The control scheme outlined in this article offers EMI mitigation across wide operating regions without compromising PES regulation. Moreover, it does so by use of switching sequences that guarantee the reachability of the PES dynamics using an advanced Lyapunov-function-based approach. SBC is a powerful tool to generate control actions for a PES based on multivariate PES state constraints. Hence, contemporary EMI regulatory standards are used as constraints in the SBC formulation to operate the PES under wide operating regime while autonomously mitigating the EMI levels. The work may be of paramount importance for operating the ultra-fast-transition recent wide-bandgap semiconductor devices like GaN–FET and SiC mosfet under higher power with increasing switching frequencies, which is usually desirable for increased power density and reduced switching losses. Here, a hardware Cuk–PES operated with GaN–FETs is fabricated and is used for case illustration. It is shown by experimental results how SBC mitigate DM and CM EMI noise of the PES while maintaining regulation even for the higher order nonminimum phase PES, while reducing sensor requirements using state observer derived from the switching model of the PES.

In a conventional linear-control design of a higher order power-electronic system (PES), the gains of the control laws are typically determined by small-signal analysis of the averaged model of the PES. The closed-loop control of such a PES (driving a pulsating load that periodically shifts the equilibrium) using its small-signal model is often found to be unsatisfactory with regard to the overall stability and performance. To address the challenges in control design for a PES driving such a nonlinear time-varying pulsating load, this paper delineates an optimal switching-sequence-based control (SBC) scheme, which applies stability-bound switching sequence(s) to the PES. A novel method has been formulated to ensure the reachability of the PES dynamics based on its switching sequence in terms of the time horizon of the switching sequence and the allocation of this time among the switching states of the same switching sequence. This is ascertained by modeling the PES and the pulsating load as a nonlinear map and then using this map and multiple Lyapunov functions determined by solving a set of linear-matrix inequalities corresponding to each of the switching states of a given switching sequence. It has been further shown that the knowledge of the stability bounds of a reachable switching sequence helps in reducing the online computation time for optimal SBC associated with solving the optimization problem by reducing the overall search space. Finally, to validate the optimal SBC, an experimental GaN-FET-based 100-kHz Cuk-PES has been fabricated and tested on a pulsating load. The overall SBC is implemented on a low-cost TMS320F28335 DSP, which also implements an observer to preclude the need for plurality of sensors for the higher order Cuk-PES. The overall performance of the SBC is found to be satisfactory under varied dynamical conditions.

GaN-FET-based solar microinverter using a differential-mode inverter (DMI) topology is presented. Key features of the DMI topology and its switching scheme are outlined and how the GaN-FET technology affects the power-stage performance are narrated. Further, summary of the issues with grid connection are elaborated. Next, how the modular DMI can be scaled for three-phase inverter and energy-storage applications are illustrated. Finally, one manifestation of how the energy storage can be integrated using topology emulating the DMI is narrated.

This paper delineates a mechanism to attain decentralized control of a high-frequency distributed power system (HFDPS) based on local observation and/or estimation at the source and load ends. An acceptable dynamic performance of the independent control eliminates/reduces the need for high-speed communication (that typically needs to be high because of HF power transfer) between the source- and load-end controllers. This provides practically complete autonomy for the HFDPS. To verify the dynamic performance of the control scheme, start-up, transient and steady-state results have been provided.

Control of a distributed power system (DPS) is a challenging task and requires unique control formulation as they arise in complex engineering problems. Since DPSs are gaining widespread importance, development of robust control strategies, which encompasses the nonlinear behavior and spatial spread of such networks, commands utmost gravity. Due to the spatial spread of such networks, state observer design based on local state variables plays a role of paramount importance. In this paper, the authors have outlined the design of a non-linear state observer which will aid a distributed control architecture for a single-input multi-output high frequency distributed power system (HFDPS) which incorporates need-based asynchronous power transfer. An adaptive control strategy for independent control of the need-based asynchronous HFDPS will be implemented based on the estimated state variables of the observer. Hence global control objectives are addressed using local sensing and a robust estimator design. Experimental results are portrayed in order to verify the stability and robust dynamic performance of the observer so designed. The nonlinear state observer was designed in the framework of exact formulation based on nonlinear map. Hence the observer encompasses the impact of switching frequency and other fast scale dynamics without any bandwidth limitation.

Differential-mode Cuk inverter (DMCI) represents a class of single-stage inverter with low device count, modular symmetry, and topological simplicity. Recently, discontinuous modulation scheme (DMS) has been proposed for the DMCI. This paper extends the modular nature of the power stage to the control architecture and proposes a transformation-based tracking controller using adaptive control algorithm for the same. A key challenge in designing a controller for DMS-based DMCI is to take into account the inherent converter nonlinearity and startup transient at the start of every line cycle. Experimental results are provided for startup, steady state, load transition, and total harmonic distortion (THD) using GaN-FET based DMCI, which validate the efficacy of the implemented modular transformation-based tracking controller.

Power electronic systems are gaining widespread importance in contemporary world due to the extensive integration of renewable energy resources into grid. As a consequence of grid integration of renewable energy sources, developing robust control methods for inverters have gained paramount importance, since the control scheme that we apply plays an important role in ensuring stability and good performance of the inverters. Taking this into account, we have designed an optimal switching sequence based controller (OSBC) which ensures stability and robustness of a differential-mode inverter (DMI), which is based on Cuk topology. The controller, so designed, responded well to large signal perturbations under varying operating conditions. The control scheme developed provides good steady state and transient response. The control leads to the rapid convergence of the input inductor current to its reference resulting in fast convergence of the output voltage to its reference ass well.