This paper presents an indirect sliding mode control (SMC) for single-ended primary-inductor converters (SEPIC). Unlike the conventional SMC methods, the proposed SMC method employs a sliding surface function based on the input current error only. The use of such sliding surface function not only simplifies the implementation, but also reduces the cost of implementation. It is shown that the output voltage control can be achieved indirectly. The input current reference is generated by proportional-integral (PI) regulator. The existence condition and region of the closed-loop system are determined for all possibilities of the PI gains. The performance of the proposed SMC method is investigated on a laboratory prototype converter, operated in buck and boost modes, in terms of the voltage regulation ability under abrupt changes in the input voltage and load resistance. The experimental results are presented and discussed.

In this study, Perturb and Observe Maximum Power Point Tracking (P&O MPPT) algorithm and Model Predictive Control (MPC) algorithm are combined to improve the dynamic performance of the control structure of boost converters used in renewable energy systems. For this purpose, a digital control method that does not need any comparator is developed. The maximum power point current value is determined from MPPT algorithm and it is used as the reference for current control operation in MPC algorithm. Dynamic capability and tracking performance of the proposed control method is validated by simulation and experimentally. The dynamic behavior of the control algorithm is analyzed by carrying out step change tests. Results show that the control method has excellent dynamic performance thanks to its feature of reference tracking in only one switching period. Furthermore, overshoots and undershoots are successfully eliminated.

This paper presents a model predictive control (MPC) method for DC-DC single-ended primary-inductor converters (SEPIC) with auto-tuning weighting factor capability. The conventional MPC requires retuning of the weighting factor when the operating condition of the converter is changed. The effect of this change is observed as inability of the controller in maintaining the switching frequency constant. The weighting factor avoids excessive switching frequency in the DC-DC converters. Based on the relation between the inductor current ripple and switching frequency, an auto-tuning weighting factor based MPC is proposed. The effect of the weighting factor on the switching frequency is investigated. The proposed MPC eliminates the need for retuning the weighting factor when the operating point of the converter is changed. The proposed control strategy is verified experimentally under input voltage, load, and parameter variations. The results obtained from conventional and proposed MPC methods are compared. It is shown that the proposed MPC method controls the average switching frequency when the operating mode of the converter is changed. Furthermore, parameter mismatch results are presented for both conventional and proposed MPC methods.

In this paper, a multi-input multi-output (MIMO) sliding mode control (SMC) methodology with constant switching frequency for single-phase quasi-Z-source inverters (qZSI) is proposed. The mathematical model of the entire system is derived in state-space form. The proposed SMC is capable of controlling both dc and ac sides of the system concurrently. Unlike the existing methods, the proposed control does not require proportional-integral (PI) controller in the dc-side. Furthermore, it offers several advantages such as simple implementation, reduced gain requirement, robustness against system parameters, and zero steady-state error in the load voltage. The fixed switching frequency is attained by altering the sliding manifold behavior inside a boundary layer. The power balance equation is used to generate the dc side inductor current reference. The feasibility of the proposed control method is investigated experimentally when qZSI feeds linear and nonlinear loads.

This paper introduces an adaptive super-twisting sliding mode control (ASTSMC) approach for controlling a dual active bridge (DAB) converter with an extended phase shift (EPS) modulation. The conventional single-phase shift (SPS) modulation-based DAB converter is known to be inefficient. Hence, an optimization algorithm based on the Lagrange multiplier method (LMM) is proposed to minimize both backflow power and inductor current stress simultaneously. Unlike the conventional schemes that use an offline optimization (OFFO) method to derive the phase shift ratios, this paper proposes an online optimization method and an ASTSMC method for generating the inner and outer phase shift ratio respectively. Initially, a generalized average modeling (GAM) for the DAB converter under EPS modulation is derived, and then the proposed ASTSMC is introduced according to this model. The conventional STSMC with constant gains suffers from low performance under disturbances such as load current perturbations, input voltage variations, and output voltage reference variations. Additionally, it requires an overestimated gain under steady-state conditions. To address these issues, a variable gain-based STSMC scheme is proposed to enhance the performance of the converter under all operating conditions. The effectiveness of the proposed method is verified through simulation and experimental results, which are compared with the results of the conventional STSMC method.

This article presents a new exponential reaching law (ERL) approach for the sliding mode control. Contrary to the existing reaching law methods, the proposed ERL does not employ a sign function and yields a faster reaching time. An expression of reaching time in terms of reaching law gains is derived analytically. The article will show that the reaching time to the sliding surface is very small provided that the gains are selected properly. The stability of the proposed reaching law will be proven. The proposed reaching law with sliding mode control is employed to control a 5-kW three-phase multilevel multifunction converter. It is shown that the system can operate as a rectifier, as a shunt active power filter (SAPF) or as a combination of both rectifier and SAPF simultaneously. Experimental results corresponding to each operation mode are presented to confirm the efficacy of the proposed reaching law under fast-changing nonlinear load currents.