Power Electronics Converters

This paper designs two DC-DC converter configurations integrated with solar PV renewable energy resource. Its focuses on comparing two converter topologies: the conventional boost converter and the switched capacitor boost converter. The Perturb and Observe (P&O), Incremental Conductance (INC), Genetic Algorithm (GA), and Particle Swarm Optimization (PSO) algorithms are employed to dynamically enhance the Maximum Power Point Tracking (MPPT) performance for both converters. The simulation results demonstrate that both converter topologies, when integrated with appropriate MPPT algorithms, can effectively harvest maximum power from the solar PV. However, the switched capacitor topology converter exhibits advantages in terms of current capabilities and voltage performance. In addition, combing the switched capacitor boost converter with the GA-MPPT algorithm improved the output voltage profile. The switched capacitor topology demonstrates distinct advantages by exhibiting enhanced current control, enabling improved handling of dynamic load changes and varying irradiance conditions. It shows voltage regulation, resulting in reduced output voltage fluctuations and enhanced stability, thereby optimizing energy extraction. The GA-MPPT simulation demonstrates a substantial increase in maximized output current for the switched capacitor boost configuration (70A) when compared to the conventional type (10A). The validation and implementation of the system models are carried out using MATLAB/Simulink. Full article

In many cases, power inductors are responsible for most of the power loss, volume, and cost if applied to high-frequency power electronics applications. It is desirable to optimize their design by the proper calculation of winding and core loss. It allows faster and cheaper commercial product release, which is the key to being successful in a highly competitive market. This is only possible if existing calculation techniques and technical data given by, e.g., core manufacturers, are verified and correct; otherwise, the inductor optimization process is less precise and requires several iterations to achieve good convergence. This paper addresses existing and proposes improved measurement and calculation techniques with regard to complex permeability, one of the key quantities that define inductor behavior in the frequency domain. This is done through impedance measurement and improved definition of the equivalent inductor model. Moreover, the proposed calculation techniques fulfill the need for the simple, accurate analytical methods required in commercial designs. Full article

Digital low-dropout (DLDO) is widely used for power management in the system-on-chip (SoC) because of its low-voltage operation and process scalability. However, conventional DLDOs suffer from the trade-off between transient response and power consumption of the DLDO and the clock generator. This paper proposes an event-driven self-clocked DLDO regulator. The proposed low quiescent current (I_Q) event-driven adaptive frequency clock generator (EACG) adapts its frequency in different load conditions without a current sensor or complex compensation circuit for stable operation in the entire load range. The proposed DLDO does not need any external clocking signal and can maintain low output ripple and low power consumption in the steady-state. The clock-less transient detector (CLTD), consisting of two clock-independent transient detection paths, uses power more efficiently and improves the transient response significantly without sacrificing the power consumption. This work was fabricated in a 40 nm CMOS process with an 0.3 nF on-chip capacitor. The measurement results show that with the step load current between 1 mA and 60 mA, the proposed DLDO achieves a transient recovery time of 220 ns. The total I_Q of the proposed DLDO is only 26 μA in steady-state, and it achieves stable operation in the entire load range. Full article

The research proposed a novel LED driver with the functions of power-factor correction (PFC) and current balancing. A flyback converter and a Class-D series resonant converter were integrated by sharing an active switch to form a single-stage circuit topology. The flyback converter played the role of a PFC circuit. The component parameters were designed to make the flyback converter to operate at discontinuous-conduction mode (DCM). In this way, the input line current can be sinusoidal, resulting in near unity power factor and low total harmonic distortion in current (THDi). The resonant converter was connected in series with a differential-mode transformer with a turns ratio of 1 to drive four LED strings. The current of the four LED strings will be automatically and evenly balanced by using the 1:1 transformer. This article analyzed the different modes of operation in detail, derived the mathematical equations and designed the parameters of the circuit components. Finally, a 72-W prototype LED driver was implemented and tested. A satisfactory performance has verified the feasibility of the proposed LED driver. Full article

An accurate analysis method for an LLC resonant converter and a time-domain analysis (TDA)-based voltage gain curve derivation algorithm are proposed in this paper. When applied to an LLC resonant converter, the TDA method can obtain high-accuracy current and voltage waveforms by solving nonlinear equations for circuit parameters through operation-mode analysis. An LLC resonant converter operating mode classification algorithm was proposed based on the results of this analysis. The circuit voltage and current values in the steady state were quickly and precisely derived using this algorithm. An accurate power-loss analysis is required to design a high-efficiency converter. Therefore, TDA is a powerful tool for designing an LLC resonant network. The proposed TDA-based LLC resonant converter analysis and voltage gain curve derivation algorithm provides high-accuracy voltage, current value estimation and voltage gain curves for all switching-frequency ranges. The effectiveness of the proposed algorithm is verified using a 500 W LLC resonant converter prototype experiment. Full article

Power factor correction (PFC) can be achieved by a single-ended primary inductor converter (SEPIC) operating in boundary conduction mode (BCM) with conventional constant on-time (COT) control, but it is challenging to achieve low total harmonic distortion (THD) and high-power factor (PF), particularly at high input voltage. A variable on-time (VOT) control strategy for BCM SEPIC PFC converter without input voltage feedforward and multiplier circuits is proposed to realize unity PF in this paper. By using a variable slope sawtooth generator whose slope is controlled by the duty cycle of the main switch to adjust the conduction time of the main power switch of the converter, the proposed VOT control scheme can use a simple and easy-to-implement circuit to enhance the PF and decrease the THD significantly, especially at high input voltage. The simulation model and 100W experimental prototype are built to verify the feasibility of the suggested control method. Simulation and experiment results demonstrated that the novel VOT control scheme remarkably enhances PF and decreases THD without affecting the efficiency by contrast with the conventional COT control. Full article

Multi-output power converters using different architectures can have significant efficiency advantages. This paper proposes a multi-output welding power supply that is based on the middle DC converter distributed architecture. This machine includes two converter groups, and each group comprises a three-phase rectifier unit, a full-bridge converter unit, a HF (high frequency) transformer, a rectifier unit, and a chopper converter unit. Among these units, the three-phase rectifier unit, full-bridge converter unit, HF transformer, and rectifier unit convert three-phase AC voltage into a low voltage, and the chopper converter unit converts the low voltage into the required current. The welding power supply can output four DC and two AC currents. This paper also analyzes the stability of the welding power supply. Finally, a prototype is designed and verified through experiments, and the maximum output of the prototype is 300 A. The experimental results show that the converter can output different DC and AC currents according to the requirement, the multiple outputs are independent of the others, and the output phase and value are independently adjustable. After verification, the proposed multi-output welding power supply can output steady current according to the requirement. Full article

This article addressed the problem of matrix converters (MxC), specifically the investigation of power losses and matrix converter efficiency in a 3 × 5 arrangement. In today’s modern world, efficiency is very important; hence, power loss and efficiency analysis are important throughout the design process of modern semiconductor converters. The ability to evaluate power losses more quickly using the simulation approach can greatly reduce the amount of time necessary for the design, in comparison with numerical analysis. The described model employed contemporary SiC semiconductors, which offer substantial benefits over IGBT transistors. The 3 × 5 converter model was shown, along with a study of power losses in various elements of the converter, such as the power circuit, input filter, and so on. A summary of the simulated findings was offered at the end of the study, along with the benefits and drawbacks of employing SiC semiconductors in bidirectional switches for matrix converters. Full article

The Voltage Source Converter (VSC) is the basis of STATCOMs and other power systems. It is composed of a three-phase inverter in which the activation of the switching devices must be controlled to generate the intended signals. The control technique used to switch the power devices affects the performance of the converter in terms of harmonic distortion mainly. Although some complex modulation techniques have been proposed in the related literature, local controllers opt for simpler methods as they provide robustness and they ease the implementation. In this paper, we propose a simple but effective technique to switch the transistors of a three-phase inverter with a Space Vector Modulation (SVM) supported by a Finite-State Machine (FSM). With this model, the switching technique can be easily implemented in low-cost microcontrollers with reduced memory and computational resources if code optimisation is performed. With an electrical analysis, we have designed a low-pass band filter adequate for the proposed switching technique. In a laboratory prototype, the performance of this proposal is evaluated under static and dynamic conditions. When compared with other control techniques (classical SVM and PWM), we conclude that a similar harmonic distortion is achieved. Full article

The inherent unlimited high switching frequency of the sliding mode controller (SMC) is limited by practical constraints of the hysteresis modulation (HM) technique. The inductor current and output voltage of a converter can be regulated using a combination of HM-SMC. However, HM-SMC results in a variable switching frequency operation, which is not preferred due to Electromagnetic Interference (EMI) issues. In this paper, an interval fuzzy controller is designed and developed as a solution to enable HM-SMC. In addition, a robust sliding surface is proposed, which provides an improved dynamic response. The two proposed controllers’ compatibility with one another has been tested via experiments such as a step change in input voltage, load resistance variation, and finally, a step change in output voltage reference value. The test results validate that while the interval type-2 fuzzy maintains a constant switching frequency with acceptable dynamic responses, it successfully regulates the state variables of the system. A comparison of the performance of the proposed control method with existing techniques in the literature is presented. Full article

Solar photovoltaic simulators are valuable tools for the design and evaluation of several components of photovoltaic systems. They can also be used for several purposes, such as educational objectives regarding operation principles, control strategies, efficiency, maintenance, and other aspects. This paper presents an automated solar photovoltaic simulation system with the capability to generate automated tests considering different parameters of solar photovoltaic panels and different operation conditions. The proposed simulator is composed of three buck-boost DC–DC power converters controlled in such a way that will behave similarly to solar photovoltaic panels. It allows to introduce additional variable loads and maximum power point tracker algorithms similar to real systems. Some converters are controlled by a DSP microcontroller connected to a single programmable logic controller which generates the automated tests. Thus, using the presented solution, it is possible to implement the I-V and P-V characteristic curves of solar photovoltaic panels and evaluate different maximum power point tracker algorithms considering different meteorological conditions and load variations, being a useful tool to teach subjects related to renewable energy sources and related applications. Several simulation results using Matlab/Simulink and experimental results are presented to validate the operation of the proposed solution. Experimental results achieve a ripple between 2% and 5% of the desired average current in MPP conditions. Full article

The stability of a hybrid AC-DC microgrid depends mainly upon the bidirectional interlinking converter (BIC), which is responsible for power transfer, power balance, voltage solidity, frequency and transients sanity. The varying generation from renewable resources, fluctuating loads, and bidirectional power flow from the utility grid, charging station, super-capacitor, and batteries produce various stability issues on hybrid microgrids, like net active-reactive power flow on the AC-bus, frequency oscillations, total harmonic distortion (THD), and voltage variations. Therefore, the control of BIC between AC and DC buses in grid-connected hybrid microgrid power systems is of great importance for the quality/smooth operation of power flow, power sharing and stability of the whole power system. In literature, various control schemes are suggested, like conventional droop control, communication-based control, model predictive control, etc., each addressing different stability issues of hybrid AC-DC microgrids. However, model dependence, single-point-failure (SPF), communication vulnerability, complex computations, and complicated multilayer structures motivated the authors to develop online adaptive neural network (NN) Q-learning-based full recurrent adaptive neurofuzzy nonlinear control paradigms for BIC in a grid-connected hybrid AC-DC microgrid. The proposed strategies successfully ensure the following: (i) frequency stabilization, (ii) THD reduction, (iii) voltage normalization and (iv) negligible net active-reactive power flow on the AC-bus. Three novel adaptive NN Q-learning-based full recurrent adaptive neurofuzzy nonlinear control paradigms are proposed for PQ-control of BIC in a grid-connected hybrid AC-DC microgrid. The control schemes are based on NN Q-learning and full recurrent adaptive neurofuzzy identifiers. Hybrid adaptive full recurrent Legendre wavelet-based Neural Network Q-learning-based full recurrent adaptive NeuroFuzzy control, Hybrid adaptive full recurrent Mexican hat wavelet-based Neural Network Q-learning-based full recurrent adaptive NeuroFuzzy control, and Hybrid adaptive full recurrent Morlet wavelet-based Neural Network Q-learning-based full recurrent adaptive NeuroFuzzy control are modeled and tested for the control of BIC. The controllers differ from each other, based on variants used in the antecedent part (Gaussian membership function and B-Spline membership function), and consequent part (Legendre wavelet, Mexican hat wavelet, and Morlet wavelet) of the full recurrent adaptive neurofuzzy identifiers. The performance of the proposed control schemes was validated for various quality and stability parameters, using a simulation testbench in MATLAB/Simulink. The simulation results were bench-marked against an aPID controller, and each proposed control scheme, for a simulation time of a complete solar day. Full article

With the development of environmental and economic requirements, the light-load efficiency of DC/DC converters is increasingly important. However, many isolated regulated converters still use fixed-frequency control, which has low light-load efficiency. This paper proposes a new digital control method to improve the light-load efficiency under fixed-frequency control. On the one hand, new gate-drive timing control is proposed to achieve the soft-switching of the primary switch. On the other, the software voltage–second balance method realizes the synchronous rectification in the discontinuous conduction mode, which reduces the conduction loss. The diagram and workflow of the proposed control scheme are demonstrated at length. A 100-Watt prototype was designed, and the test results show that synchronous rectification and quasi-zero-voltage-switching are realized in the whole operating range at the light load. The light-load efficiency is 81% to 87%, which improves by 5% to 10% in comparison to the traditional forward converter. The prototype also functions well under the load transient. The proposed control scheme is implemented in one digital controller without additional components, and the circuit is low loss and low cost. Full article

The problem of insufficient regulation ability in isolated microgrid operations in traditional master–slave control is targeted in this research. A hybrid master–slave control strategy is proposed to operate multiple distributed generators (DGs) in a microgrid with alleviated regulation characteristics. Firstly, a virtual synchronous generator control is adopted in the master DG to provide voltage and frequency support for the system; however, the lack of participation of the slave DG control in traditional PQ droop control in the system regulation makes a master DG susceptible to any load variation. The problem is resolved by proposing an improved droop control strategy, which ensures that the slave DG has similar output droop characteristics as the master DG and thus can respond to system load disturbances alongside the master DG. Secondly, virtual coordinate transformation and virtual impedance control are introduced to realize the decoupling and precise distribution of output power of multiple DGs. Finally, a simulation and experimental platform for a multi-DGs parallel system are established to verify the effectiveness of the proposed strategy. Full article

This paper proposes the influence analysis of silicon carbide (SiC) MOSFET’s parasitic output capacitance on a dual active bridge (DAB) converter. Power converters are required for DC grids and energy storage. Because SiC metal-oxide-semiconductor FETs (MOSFETs) have lower on-state resistance and faster reverse recovery time than Si MOSFETs, they can be controlled with lower losses and higher frequencies. MOSFETs have a parasitic capacitance. Because of the output parasitic capacitance, the switch voltage does not rise instantaneously during switching but has a delay. The output parasitic capacitance of the switch depends on its drain-to-source voltage, and this parasitic capacitance affects the output of the DAB converter by delaying the switch voltage. In this paper, in order to analyze the effect of the parasitic capacitance on the DAB converter output, the delay time was calculated through a formula, and this value was compared with a simulated value. In addition, the effect of the parasitic capacitance of the SiC MOSFET on the output of the DAB converter was presented by comparing the actual output voltage with the ideal output voltage and analyzing the effect of the output voltage according to the delay. Full article

Currently, silicon carbide (SiC) MOSFETs are several times higher in cost than the equivalent silicon (Si)-IGBTs; however, the gains in power conversion efficiency, simplification of thermal management, and energy savings in general bring the advantages of lower total cost of ownership. The implementation of discontinuous PWM (DPWM) techniques for controlling the motor drive brings further reductions for the semiconductor switching losses; however, most existing techniques have limited performance on the optimized clamping region, particularly at a low power factor, which is a common operation condition for motor drives employing the widely used $V/f$ control, particularly at partial- or low-load conditions. This paper evaluates the performance of a SiC-based two-level voltage-source inverter (2L-VSI) motor drive operated with generalized carrier-based PWM methods. Theoretical analysis and experimental measurements are conducted in a 2.2 kW heatsink-less 2L-VSI prototype and induction machine, which demonstrates that the minimum switching losses DPWM (MSL-DPWM) is the most favorable solution in practice in terms of the achievable power conversion efficiency and harmonic distortions and also produces the least common-mode current, which is critical in motor drives. Full article

Currently, the design of resonant power converters has only been developed while operating in the steady state, while the design operating in the transient stage has not been considered nor reported. This paper is interested in testing the performance of the resonant circuits operating in the transient stage and finding applications where benefits can be obtained from this form of operation. One application in which it is possible to obtain benefits from designing resonant circuits in the transient state is in the area of frequency multiplication. Usually, to achieve frequency multiplication, it is necessary to resort to complex methods and special devices that increase the complexity of the design and the total cost of the circuit. This paper evaluates the performance of a series RLC resonant circuit operating in the transient stage and with an underdamped response acting as a frequency multiplier, where the oscillation frequency of the current in the resonant tank is “n” number of times the switching frequency of the square voltage source at the input with a duty cycle of D = 50%. To validate the analysis, a circuit was designed to deliver an output power of 30 watts to a resistive load, where the switching frequency of the square voltage source at the input was 500 kHz. Since a multiplier value “n” equal to fifteen was chosen, the current in the resonant tank reached an oscillation frequency of 7.5 MHz. The design methodology was validated by simulations in SPICE, complying with the established design parameters. Full article

This work presents a flexible strategy for RMS current reduction of healthy phases for brushless DC synchronous motors (BLDC) operating in phase opening failure, avoiding motor degradation without reducing its performance and allowing safe shutdown when a phase failure is detected. After the diagnosis of an open-phase failure, a corrective action divided into three steps is proposed. First, the traditional Six-Step operating mode with 120° electric degrees is changed to a new operating mode that uses the two healthy phases at 180° electric degrees to reduce torque loss due to phase failure. Second, a trapezoidal shape (with adjustable angles according to the RMS current level) is imposed as a current reference for the controller to reduce the current level and, consequently, improve the efficiency of the motor. Third, the passband of the speed control loop is reduced to minimize the influence of speed oscillations in controller failure. The experimental results presented show that the mode of operation with the proposed dynamic current reduction strategy allows an approximate reduction of up to 27% in the effective current and up to 41% in the motor temperature variation, compared to the usual failure mode of operation of the BLDC motor without the proposed strategy. The dynamics of change in the trapezium angle allowed a weighting between the current level and the oscillation of the speed, preventing the motor in phase failure from having a high-speed variation. Full article

Power converters generate switching common mode voltage (CMV) through the pulse width modulation (PWM). Several problems occur in the drive systems due to the generated CMV. These problems can be dangerous to the insulation and bearings of the electric machine windings. In recent years, many modulation methods have been developed to reduce the CMV in multiphase machines. Symmetrical nine-phase machines with single-neutral are considered in this paper. In this case, conventional PWM uses eight active vectors of different magnitudes in combination with two zero states in a switching cycle, and this generates maximum CMV. This paper proposes two PWM schemes to reduce the CMV in such a system. The first scheme is called active zero state (AZS). It replaces the zero vectors with suitable opposite active vectors. The second scheme uses ten large active vectors during switching and is called SVM-10L. Compared with conventional strategies, the AZS reduces the peak CMV by 22.2%, and the SVM-10L reduces the peak CMV by 88.8%. Moreover, this paper presents a carrier-based implementation of the proposed schemes to simplify the implementation. The proposed schemes are assessed using simulations and experimental studies for an induction motor load under different case studies. Full article

This paper presents a comparison between piezoelectric filtering and passive LC filtering integrated into an HF class L−Piezo inverter. This L−Piezo inverter is a variant of class φ2 where the filtering of the second harmonic is carried out by a piezoelectric resonator. Piezoelectric filters are well known in the signal domain (RF filtering), but their use in the field of power electronics, as a temporary energy storage element, is rather recent. In power electronics, piezoelectricity has mainly been used as a transformer, in particular, to greatly increase voltages (backlight applications). A class L−Piezo inverter with Lithium Niobate (LNO) piezoelectric resonator is designed for a switching frequency of 10.4 MHz, an input voltage of 30 V, and an output power of 15 W. To compare these two filtering methods, two prototypes are built, one with piezoelectric filtering and one with passive LC filtering. Measurements show a reduction of 60% of the losses in the filter, while the volume of the filter is reduced by a factor of 50. Full article

In this paper, we studied the discontinuous conduction modes (DCMs) of modified versions of the SEPIC, Ćuk, and Zeta converters. The modified versions of these converters were obtained by adding an extra diode to the classical versions of these converters; thus, we obtained converters with multiple DCMs. In the case of the SEPIC and Ćuk converters, the additional diode was added in series with the inductor placed at the input port, thus resembling the connection of a four-diode bridge rectifier at the input (where these converters work as power factor correctors in AC/DC conversion). The 2 diodes of the modified versions of these converters define 4 possible conduction modes: 1 continuous conduction mode (CCM) and 3 DCMs. In this paper, the 4 conduction modes were exhaustively studied, calculating their voltage conversion ratios and the equations of the curves that define the borders between conduction modes in both open- and closed-loop operations. The conduction modes and the straight line that describes the converter operation are represented in a plane called the “k₁k₂ plane”. As in the case of other characteristics exhibited by the SEPIC, Ćuk, and Zeta converters, the conduction modes, the voltage conversion ratios in each conduction mode, and the boundaries between conduction modes, coincide for the three studied converters. Finally, all theoretical predictions resulting from the analysis were verified experimentally through a reconfigurable converter prototype, working as both modified SEPIC and modified Ćuk converters. Full article

In recent years, the penetration of renewable power generations into the electrical grid has substantially increased. Continuous deployment of power electronic-based distributed generations and the reduction of traditional synchronous machines with their essential dynamics in modern power networks are very critical in this change. The use of power electronic inverters leads to the dissociation of sources and loads and lowering the power system inertia. Under power imbalance, this drop causes an elevated rate of change in frequency and frequency divergences, which has a notable impact on the system’s frequency stability. As a result, enhanced control techniques for grid-tied electronic converters are required to secure the power system’s stability and support. The virtual-synchronous generator (VSG) control is used to mimic the dynamics of a rotating synchronous generator and improve the power system’s stability. In this article, the problems of such low-inertia power systems, as well as the VSG technologies, are explored. This research also looks at different control orders and strategies for virtual-synchronous generators (VSG). In addition, the utilization of energy storage and critical matters in VSG and further research recommendations are explained. Full article