This paper proposes a multi-objective cost function-based finite control set sliding mode control (SMC) strategy for single-phase split-source inverters (SSI). The single-phase SSI is a fourth order ...system in which the control of four (inductor current and capacitor voltage in DC-side and inductor current and capacitor voltage in AC-side) variables is essential. Moreover, a complex modulation scheme is needed to generate the pulse width modulation signals for the switching devices of SSI. The proposed control strategy is based on a multi-objective cost function finite control set SMC approach. As a consequence of using multi-objective cost function, the control of DC- and AC-side variables can be accomplished simultaneously. Moreover, the use of finite control set eliminates the modulation scheme requirement. Also, the use of multi-objective cost function together with the finite control set simplifies the controller design as the hysteresis band and its tuning requirement are not needed. The robustness of proposed control strategy against parameter variations is investigated and compared with that of the hysteresis band-based SMC and conventional MPC methods. Experimental results are presented to verify the effectiveness of the proposed control strategy.
•Sliding surface functions in sliding mode control are combined in a multi-objective cost function.•The proposed multi-objective formulation offers an easy design process for controlling multiple variables.•The proposed multi-objective cost function finite control set SMC method can be implemented without hysteresis band.•Finite control set concept is integrated with sliding mode control theory for eliminating the complicated modulation requirements.
In this study, Perturb and Observe Maximum Power Point Tracking 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 the Maximum Power Point Tracking (MPPT) algorithm and it is used as the reference for current control operation in the MPC algorithm. Dynamic capability and tracking performance of the proposed control method is validated by simulation and experimentally. The dynamic behaviour of the control algorithm is analysed 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.
Since renewable energy sources such as PV and wind provide intermittent energy generation, this paper presents an advanced DC/DC converter that is able to set its operational mode automatically to ...either multi-input multi-output (MIMO) or single-input multi-output (SIMO) depending on the input source conditions. Power flow is controlled through the auxiliary relays added to a double-layer boost converter. Considering the transient events require fast dynamic response, model predictive control (MPC) is used to achieve the current control processes for both layers. Furthermore, the MPC is modified to adapt itself to changes in the topology. The proposed system is verified by simulations and experimentally. Results show that the proposed mode-changeable converter successfully determines the optimum power route after deciding the best operational mode in accordance with the input source conditions. Furthermore, the control method achieves a powerful and effective control process in both MIMO and SIMO modes.
•A novel multi-port mode changeable DC–DC converter is developed.•Model Predictive Current Control strategy is presented for the converter.•The proposed converter is able to set its operational mode automatically.
In this study, a global fast terminal sliding-mode control (GFTSMC), which offers a faster convergence performance than its counterparts is constructed for managing the state variables of the DC-DC ...buck converters. For the first time in this study, the GFTSMC was designed for power electronics circuits based on hysteresis modulation (HM). The HM technique's variable switching frequency problem is overcome by reusing the GFTSMC structure, which enables the hysteresis band to be changed adaptively, and a fixed switching frequency is obtained. The proposed control scheme uses only one sensor for regulating the output voltage and controlling the switching frequency. Thus, an extremely economical and robust system, which is minimally affected by the negative aspects originating from the sensors, is obtained. Effectiveness of the proposed controller is validated with experimental studies. The experimental results shows that the output voltage and switching frequency are successfully controlled with good dynamic and steady state response. Finally, to validate the experimental feasibility of this paper, a comparison of the proposed method and four existing studies with different control schemes is presented.
In this paper, a modified fast terminal sliding mode control (FTSMC) with a fixed switching frequency is proposed for regulating the output voltage of the DC-DC buck converters. The design steps of ...the proposed FTSMC such as the selection of sliding surface, switching control strategy, existence, robustness, and stability analysis are presented in detail. To overcome the variable switching frequency in FTSMC, a frequency control loop is designed. Moreover, the proposed FTSMC with fixed switching frequency can be implemented by using only one voltage sensor. Hence, the proposed control method not only offers a fast dynamic response and fixed switching frequency but also simplifies the controller design in practical implementation. The effectiveness of the proposed control methods has been investigated by experimental studies. The results reveal that the proposed methods exhibit a good performance under both steady-state and dynamic transients caused by the variations in load resistance, input voltage, and reference voltage. Moreover, the proposed method is compared with four existing methods.
Design and simulation of a new inverter scheme are reported in the paper. The inverter is especially developed for an axial flux permanent synchronous generator (AFPMSG), which can be used for low ...power wind energy systems. The system includes a battery charge unit in addition to the inverter. Initially, the permanent magnet synchronous generator (PMSG) model has been created for MATLAB/Simulink environment. Since frequency and amplitude of the waveforms generated by the PMSG strictly depend on the rotation speed, several tests have been performed under different wind speed regimes. Then, an appropriate inverter model has been designed and connected to the output of the PMSG in order to convert the generated voltage from AC to DC. Thereby, stabilizing voltage and frequency has been assured and the charge of the battery unit has been realized for efficient energy storage. The simulations show that the system designed has lower THD on the current signal according to the similar ones presented in recent literature. Furthermore, the THD value has been much improved (i.e. 0.72%) thanks to the design of an additional filter unit. The proposed system can be implemented to low power wind energy systems.
•A new off-grid converter design has been performed for a new axial flux permanent magnet generator.•The THD rates are found promising with the value of 0.72% by giving a qualified power generation.•The stabilities of frequency and voltage are provided under variable loads.•The converter includes a battery pack to store the electrical energy for the possible usage.
An equal‐weighted cost function‐based weighting factor tuning method for model predictive control (MPC) in power converters is presented here. In conventional MPC methods developed for power ...converters, the use of weighting factors is a necessity to determine the importance of sub‐terms in multi‐objective cost functions. The proposed method is based on equalizing the importance of cost terms by using normalized values rather than the actual values. As a consequence of normalized values, all sub‐terms are transformed into a similar range independent from their actual values. Hence, the weights of cost terms are equalized, leading to the elimination of weighting factor tuning necessity. The proposed equal‐weighted cost function not only offers simplicity in the MPC design but also guarantees the desired controller performance with the dynamically weighted sub‐terms. The proposed control method is validated on a grid‐connected single‐phase three‐level T‐type inverter. Experimental results are carried out to demonstrate the effectiveness of the proposed method under steady‐state and dynamic conditions. Moreover, the comparative results with the conventional MPC are presented. The results reveal that the proposed approach exhibits excellent performance against the variations in the operating point of the inverter.
An effective finite control set model predictive control (FCS‐MPC) is introduced for single‐phase three‐level T‐type rectifiers supplying resistive as well as constant power loads (CPL). The main ...problem of CPL is the negative resistance phenomenon that endangers the rectifier's stability. Hence, the proposed FCS‐MPC method is based on Lyapunov's stability theory such that the stability of the rectifier is guaranteed under all operating points. Unlike the existing FCS‐MPC methods, the cost function design in the proposed control method is formulated on the rectifier's stability. According to Lyapunov's stability theory, the rectifier stays stable provided that the rate of change of Lyapunov function is negative. In this case, the derivative of the Lyapunov function can be used as the cost function without utilizing any weighting factor. Therefore, contrary to the existing FCS‐MPC methods, the weighting factor requirement is eliminated which leads to easiness in the design and implementation of the controller. Experimental results reveal that the proposed control approach exhibits very good performance with undistorted and distorted grid voltage conditions when the rectifier feeds resistive and CPL 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.
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