Converter Output Research Articles

A simplified consensus-based distributed secondary control for battery energy storage systems in DC microgrids

DC microgrids have become a promising solution for efficient and reliable integration of renewable energy sources (RESs), battery energy storage systems (BESSs) and loads. To simultaneously achieve average voltage regulation, accurate current-sharing and state-of-charge (SoC) balance, at least two state variables need to be transmitted between neighboring BESS nodes in conventional distributed secondary control. In this paper, a simplified consensus-based distributed secondary control for BESSs in DC microgrids is proposed with only one virtually defined state variable being transmitted, where a cascaded control framework consisting of an SoC controller and a voltage controller is used to regulate DC bus voltages. This virtual state variable combines BESS SoC and its converter output current, there is no need to change the control law when BESSs switch between charging/discharging modes. Once SoCs are balanced, SoC controller works as a current controller. With the proposed control strategy, the number of transmitted state variables and the complexity of controller design are significantly reduced. Stability and steady-state analysis are also conducted to confirm the effectiveness of the proposed control strategy. Finally, Simulink simulation and hardware-in-loop tests are presented to validate the proposed control strategy.

The design of a hybrid DC/DC converter for LED lighting system using a single switch

A novel hybrid Luo-Cuk converter designed for LED lighting systems combines elements from both Luo and Cuk topologies. By integrating the input branch of both topologies, the converter, employing a single switch, can generate two distinct types of outputs simultaneously. One output follows a Luo-type, while the other adopts a Cuk-type . Through a series connection of the outputs from Luo and Cuk topologies, the voltage gain of the converter has been notably enhanced. The converter's output can be effectively regulated using a single controller. To validate the consistency between the topology's performance and theoretical analysis, simulation and prototype results have been provided.

Near Spurious-Free Thickness Shear Mode Lithium Niobate Resonator for Piezoelectric Power Conversion.

Piezoelectric power converters, where acoustic resonators replace the inductors as energy storage elements, promise much higher power density and higher efficiency compared to conventional circuits. Recently, lithium niobate (LiNbO3) piezoelectric resonators have been integrated within power converter circuits, showing good conversion efficiency, thanks to their high quality factor (Q) and electromechanical coupling (kt2). However, the converter output power range is limited by large spurious modes near resonance. This work reports a near-spurious-free LiNbO3 thickness shear (TS) resonator, demonstrating high Q of 3500 and kt2 of 45% at 5.94 MHz, with a fractional suppressed region of 35%. First, we identify the best LiNbO3 crystal orientation for efficient TS resonators. Then, we propose a novel acoustic design without busbars for spurious suppression, which is extensively simulated, fabricated, and characterized. Further analysis is done to identify existing spurious modes in our proposed design, specifically the effect of dicing on our TS resonator design. Upon optimization, LiNbO3 TS resonators could potentially empower a new design space for low-loss and compact power converters.

High gain novel two input two output buck-boost converter for electric vehicle applications

ABSTRACT With the advancements in electric vehicles in the market, it is necessary to rephrase the converter for effective gain. The proposed Two Input – Two Output (TITO) converter accepts input from two sources: Battery and Solar PV panel included with non-isolated buck, boost, and buck-boost DC–DC converters. Also, the proposed TITO converter topology uses only three switches when compared to conventional multiport converters where the number of semiconductor switches is higher. The conventional converter has a higher number of components, whereas the proposed converter has a reduced number of conduction components as well as switching semiconductors. As a result, there is a reduction in energy lost. The proposed topology is designed and simulated in MATLAB Simulink and observed with a lower ripple voltage during buck, boost and buck-boost mode. Experimental setup results are also obtained from a prototype of the proposed converter, which confirms the theoretical considerations and effectiveness of the proposed topology.

Performance of a SWRO membrane under variable flow conditions arising from wave powered desalination

A wave-powered desalination unit couples a wave energy converter and reverse osmosis (RO) membrane to produce fresh water from pressurized seawater. Although renewable energy technologies have been increasingly used for desalination, the concept of direct wave-powered desalination system is still at an early stage of development. One of the challenges with direct wave-powered desalination is that while reverse osmosis (RO) membranes are typically designed to operate at a constant feed flow and pressure, wave energy converter outputs in the form of hydraulic pressures and flows are typically highly variable. In this work, a RO membrane is investigated under variable feed flow conditions to determine the potential impact of such operation on membrane performance. The feed flow and pressure are varied using both a traditional sinusoidal profile and a rectified sinusoidal profile - a case more representative for wave-powered desalination. The permeate recovery and permeate salinity for both cases are compared with the equivalent time-averaged steady-state conditions. For purely sinusoidal flow, the performance of the RO membrane was similar to the equivalent steady-state flow conditions. For rectified sinusoidal flow, there is a marginal increase in permeate recovery, while a significant increase in permeate salinity is observed. In addition, a membrane integrity test was carried out after both sets of varying flow conditions. A significant change in membrane performance was detected after the test with the rectified sinusoidal flow.

Pi And Fuzzy Logic Controlled Multiple Lift-Push-Pull Switched Capacitor Luo Converter

This study shows a simulation using PI and fuzzy logic controllers for a newly constructed elementary P/O push-pull switched capacitor Luo converter circuit. This incorporates both voltage lift and switched-capacitor technology. Power electronic converters' dynamic behavior becomes quite non-linear due to their time-varying and switching nature. Fuzzy logic controllers can be utilized as feedforward controllers for power electronic converters because conventional controllers are unable to provide high dynamic performance. By taking repeated measurements of the converter output voltage at specific points during a conduction period, the Control algorithm is created in this study to ensure tracking of the reference voltage and rejection of system disturbances. The main aim is a simulation of PI and Fuzzy logic controls using MATLAB/ Simulink software to evaluate the controller’s performances. The simulation results show Fuzzy controller performs effectively for the preferred converter.

Performance analysis of digitally controlled nonlinear systems considering time delay issues

In this paper, a comprehensive investigation into discretization, effective sample time selection considering delays in the system, and time and frequency domain analysis of a DC-DC buck converter, which plays a vital role in photovoltaic (PV) systems, is conducted to enhance the understanding of their dynamic behavior, optimize control algorithms, improve system efficiency, and ensure reliable power conversion in photovoltaic applications. To effectively address the non-linear behavior and enhance digital control of a buck converter by selecting the best sample time, several approaches can be employed. These include accurate modeling and identification of non-linear elements, development of advanced control algorithms that account for non-linearities, implementation of adaptive control techniques, and utilization of feedback mechanisms to compensate for deviations from linearity. By considering and mitigating the non-linear behavior, digital control systems can achieve improved accuracy, stability, and transient behavior in regulating the buck converter's output waveforms (voltage or current). The results of the study demonstrated that the trapezoidal integration method which is also known as bilinear approximation, or Tustin's approach outperformed other commonly used discretization methods, such as first-order hold (FOH), zero-order hold (ZOH), impulse response matching (impulse invariant), and matched pole-zero (MPZ) technique, in dual-domain (both time and frequency) analysis. The key finding highlighting the superiority of the bilinear approximation was its ability to achieve the closest match in the frequency domain bridging the continuous-time and discrete systems. This finding emphasizes the significance of the bilinear approach in preserving the frequency characteristics of the original continuous-time system during discretization. By employing this method, the discrete system closely approximated the behavior of its continuous-time counterpart, ensuring accurate frequency-domain representation.

A novel single switch controlled efficient coupled inductor-based DC-DC boost converter

Pollution is <span>one of the most hazard facing in the world. Day by day pollutions has been increased in the society due to population growth, industries, constructions, and transportation. As per the world health organization (WHO) survey, 45% of the air pollution is due to transportation because they lay on internal combustion engine (ICE) based engines. To avoid carbon footprints, green transportation should be encouraged for further generations. In recent days many electric vehicles (EV’s) are found in the market but facing some issues like battery blasts, storage limitations and lack of charging infrastructure. Out of these issues, mainly my focus is on developing a compact, efficient, simple, medium gain coupled inductor-based DC-DC boost converter is proposed which is helpful for fast charging system. In this paper, coupled inductor (CI) and switched coupled inductor (SCI) based converters are designed and analysed with mathematical approach. The outputs of both CI and SCI converters are verified and compared with simulation results and as well CI based converter is developed with hardware prototype and verified hardware and simulation results in terms of gain, elements and efficient.</span>

A Two-Degree-of-Freedom PID Integral Super-Twisting Controller Based on Atom Search Optimizer Applied to DC-DC Interleaved Converters for Fuel Cell Applications

This paper focuses on the real-time implementation of an optimal high-performance control applied to an interleaved nonisolated DC/DC converter designed for fuel cell applications. Three-phase interleaved boost converters are utilized to minimize input current undulation, increase efficiency, and provide a high output voltage in order to ensure the performance of the FC stack. The proposed control strategy contains an outer loop that generates the reference current based on a two-degree-of-freedom PID controller. This controller provides a robust setpoint tracking and disturbance rejection, which improves the system’s response and efficiency. A fast inner regulation loop based on a super-twisting integral sliding mode (STISM) algorithm is developed to achieve a fixed converter output voltage, equitable phase current sharing, and fast regulation against load disturbances in failure operation. The STISM algorithm exhibits a rapid convergence property of the sliding mode and effectively avoids the chattering phenomena frequently observed in conventional sliding modes. The proposed controller’s gains are determined using the atom search optimization algorithm, which ensures exceptional reliability and a high degree of robustness and stability of the controllers under a variety of operational conditions. This method is inspired from the behavior of atoms and their electrons during the excitation process leading to a one-of-a-kind optimization technique which contributes to the controller’s reliability. Using Matlab-Simulink simulation tools, the efficacy and performance of the designed control have first been evaluated and assessed and compared with other optimization algorithms, and then with a dual loop based on a PID controller. Then, they have been verified by real-time hardware implementation on a 1.2 KW prototype FC converter driven by the dSPACE-1104 card under a variety of tests. The suggested approach offers impressive experimental results in dynamic and steady states.

Design and analysis of multiple input single output converter for hybrid renewable energy system with energy storage capability

This paper proposes the design and analysis of a multiple-input-single-output (MISO) DC-DC converter suitable for a hybrid renewable energy system with energy storage capability. The converter design and control strategy validated in this research can be used to regulate the output dc voltage obtained from multiple-source renewable energy systems. The design is realized using a non-isolated double boost converter as it can handle bidirectional power flow at the storage port and has other advantages like compact structure, reduced number of components, and double boosting capability. The converter can also work without transformers, enabling the input renewable energy sources to operate individually. An inverted decoupler control strategy is adopted in the design of this novel converter. Mathematical models were developed to obtain the decoupler matrix, and the proposed control strategy is utilized to analyze the output. Simulations were performed on MISO converters with load and reference variations and is validated with the prototype. The current ripple percentage at the dual source side is found to be reduced by 2.6%. Also, the rise time, settling time, and percent overshoot of the output voltage were reduced by 0.03 s, 45 ms, and 3.6%, respectively. The performance of the proposed MISO converter is validated on a 50 W hardware prototype. The results validate the MISO converter's superior dynamic performance, output voltage regulation and reduced dual source ripple current, all of which are in agreement to the results of the simulation. A comprehensive comparison with the traditional controller is also conducted to further illustrate the advantages of the proposed inverted decoupler. The inverted decoupler validated in this work can be effectively used in hybrid renewable energy systems with energy storage capability, as it is found to be immune to the disturbances from the source end.

Concept of Condition Monitoring for AC-DC Converter Output Capacitors via Discriminative Features

This paper discusses recent research on the condition mon- itoring (CM) approach for aluminium electrolytic capacitors (AEC) used in power electronics equipment such as switched- mode power supplies (SMPS). Capacitors are identified as the most critical component with the highest percentage of failure in AEC. CM offers a better paradigm for AEC due to its long- lasting ability (endurance). This study proposes accelerated life testing through electrical stress and long-term frequency testing for the AEC component. An experiment test bench was set up to monitor the critical electrical parameters such as dissipation factor (D), equivalent series resistance (ESR), capacitance (Cp), and impedance (Z), which serve as health indicators (HI) for the evaluation of the AECs. Time-domain features were extracted from the measured data, and the best features were selected using the correlation-based technique. This research contributes to developing a cost-effective CM approach for AECs used in power electronics equipment, which can reduce downtime and maintenance costs.

MPPT Novel Controller Based on Passivity for the PV Solar Panel-Boost Power Converter Combination

This article deals with the MPPT controller based on passivity, which calculates through a dynamic average model between the PV solar panel and the boost power converter under uniform irradiance conditions. The MPPT algorithm is a linear controller based on the exact tracking error dynamics passive output feedback (ETEDPOF) controller design methodology. The algorithm includes suitable adaptive feedforward pre-compensation, which explicitly depends on the precisely estimated resistance of the boost converter. The MPP reaches by regulating the voltage and current of the boost converter to hold the PV maximum power in the system's input capacitor. The controller desired references such as the inductor current, the output voltage, and the average input control are in terms of the PV maximum power nominal values, which remain always fixed. A reduced-order extended state observer (RESO) develops to estimate the boost converter's output resistance, adapting to the controller's desired references. Simulation and experimental results demonstrate the effectiveness, stability, and robustness of the MPPT algorithm based on passivity as compared to the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Incremental Conductance</i> (IC) algorithm, under sudden output resistor changes, high irradiance, and high temperature in the solar panels.

Coordinated Frequency and Voltage Optimal Control of Wind Farm With Nonlinear Power Constraints

In the high-voltage direct current transmission system, if converter blocking occurs at the sending-end converter station, a serious power imbalance takes place in the sending-end grid, which causes severe over-frequency and over-voltage problems. To address this issue, a double-layer coordinated optimal control strategy based on model predictive control (MPC) is proposed in this article. By cooperatively regulating the active and reactive power of the wind farm at the sending end, it achieves coordinated frequency and voltage control. On the basis of MPC and moving horizon estimation, the upper-layer controller computes the optimal active and reactive power references of the wind farm. Subsequently, the optimized power references are fed into the lower-layer wind farm local controller for execution. A key feature of this strategy lies in its handling of nonlinear power constraints. Specifically, for a wind farm, coordinated frequency and voltage regulation faces a critical challenge of coupled nonlinear power constraints, which are formed by the coupled relationship between the active and reactive power outputs of the power converters. To overcome this challenge, the double description method is introduced to approximate and linearize the coupled nonlinear power constraints. Simulation results verify the effectiveness of the proposed strategy.

Nature of transient currents and voltages in the power chain for a Highly Segmented Fast Detector run by Low Voltage Power Supply

Supplying power at low voltage to the front-end electronics of very fast and highly segmented detectors, typical in the experiments at the Large Hadron Collider, involves several issues, including transient currents and voltages. This study investigates a power chain that involves long cables, DC-DC converters, and input filters. Due to the presence of a common ground close to the input of the DC-DC converter, the power chain can run with a lower value of the input supply. It is seen that the capacitor in the input filter plays a significant role in the process of voltage growth at the input of the DC-DC converter. The effects of the ramp during turning ON and OFF the input supply have been studied thoroughly. It is observed that the voltage/current spikes are reduced due to the application of the ramp. It is also observed that the current/voltage, both at the input and the output of the DC-DC converter, goes through some intermediate oscillations due to the existence of threshold voltage for the converters. The choice of the ramp is critical in reducing spikes and should be incorporated into the power supply.

A 500-kHz ZVS Class-E Type DC–DC Converter With Two Anti-Series mosfets Topology

Power converters powered by batteries have been widely used in many applications, such as outdoor emergency lighting, electric motorcycle charger, unmanned aerial vehicle supply and so on. This paper presents a 500 kHz zero-voltage-switching (ZVS) Class E type DC-DC converter with two anti-series MOSFETs used for battery-powered applications. The low-side MOSFET is adopted as the main switch to realize the working operation of traditional Class E resonant converter, while the high-side anti-series MOSFET is used to implement the regulation of the converter output voltage based on pulse width modulation (PWM). Both active switches are ZVS operated so that a high efficiency can be achieved. By changing the high-side MOSFET duty cycle, the ac voltage of the resonant tank is also changed to regulate the output voltage consequently. The control method is simple, and the operating frequency is constant, which is beneficial for the design of the resonant components. A 100-W prototype is built to verify the validity of the proposed control method for which a 94.85% efficiency has been achieved.

An 8nA-512μA Current-to-Digital Converter With Mixed-Signal Coarse-Fine Subrange Normalization

This brief presents a current to digital convertor (CDC) with low power, wide dynamic range and fast conversion speed. Proposed coarse converter extends the maximum input current range, and achieves fast conversion speed with the input adaptive control scheme. Capacitive transimpedance amplifier (CTIA) based fine converter digitizes the residue current and achieves fine resolution. Proposed mixed-signal coarse-fine subrange normalization technique enables seamless processing of the final converter output. The proposed CDC implemented in 0.18 μm CMOS process converts input current up to 512 μA with 7.8125nA resolution and 400 μs conversion time. Power consumption is 79.4 μW.

Selective Harmonic Mitigation: Limitations of Classical Control Strategies and Benefits of Model Predictive Control

Selective harmonic mitigation pulsewidth modulation (SHMPWM) combined with model predictive control (MPC) is a promising approach for grid-connected power converters. SHMPWM can guarantee grid code compliance in steady state, e.g. grid harmonic injection, with a reduced output converter filter, while MPC improves dynamic response and allows grid code compliance in the event of grid transients. This paper presents a survey of the MPC strategies already published in the literature developed for their use with SHMPWM. The existing strategies fall into two categories: direct model predictive control with an implicit selective harmonic mitigation modulator, and direct model predictive control based on finite control set (FCS-MPC). One representative control strategy of each group is compared to each other and to the performance of classical proportional- integral (PI) controllers combined with SHMPWM. The goal is to identify the potential benefits of MPC for grid-connected power converters, and determine the main advantages and limitations of the two selected state-of-the-art control strategies. Their performance is assessed through Hardware-in-the-Loop (HIL) experimental results in terms of real-time implementation, harmonic content grid code compliance, dynamic response and performance under grid transients.

Design of the Adaptive Neuro-Fuzzy Inference System (ANFIS) and a Genetic Algorithm Controller for Solar Photovoltaic Systems Using the Boost Converter

The Adaptive Neuro-Fuzzy Inference System (ANFIS) and an integrated offline Genetic Algorithm (GA) are proposed in this research. The ANFIS and GA technologies are employed to find the optimum point for maximum capacity in any environmental condition. Furthermore, a genetic algorithm is used to optimize data, and optimized values are used to train ANFIS. The power from the PV source is routed via the standard PI-controlled boost converter, and its working point always follows the MPPT point. When the ambient temperature and illuminance vary, the power may rapidly achieve a new maximum value thanks to the GA-ANFIS-MPPT P&amp;O algorithm, which permits adaptive adjustment of the perturbation step. The new algorithm also reduces oscillation over the whole working point of the MPPT and enhances the boost converter's output voltage quality. The adaptive GA-ANFIS-MPPT P&amp;O algorithm's benefit is validated by simulation on MATLAB has a module string, one parallel string, and a 250W PV panel. According to simulation results, the proposed GA-ANFIS-based MPPT can consistently and efficiently monitor the maximum power point of PV modules across various weather conditions

Direct Synthesis scheme based PID controller design for Boost Converter

This study's aim is to provide an introduction toa specific methodology for optimizing the design of a boost converter. The main goal of this optimization is to determine the best inductor and capacitor parameter values in order to reduce output voltage ripple, maximize efficiency, and minimize output voltage deviation. In addition, a PID control approach is employed to regulate the boost converter's output voltage using the Direct Synthesis tuning method. The simulation's outcomes indicate that the proposed approach significantly enhances the performance of the boost converter and attains maximum efficiency. This methodology and control strategy can be applied to various boost converter applications to achieve stable and optimal performance.

Fault-tolerant strategies in MMC-based high power magnet supply for particle accelerator

Many particle accelerators require to supply chains of magnets with high quality, high magnitude, cycling currents. To do this, the power converters need to provide high output voltages, reaching in some cases tens of kilovolts. Additionally, converters are required to store the magnet energy during de-magnetization cycles. For such application, Full-bridge Modular Multilevel Converters (FB-MMC) could be used given their capacity to store energy and their inherent reliability. In this sense, one of the most interesting features of the proposed topology is the possibility of bypassing one or several submodules in the event of a fault or malfunction. By doing this, it is possible to ride-through the failure of a component and avoid the interruption of the accelerator operation.However, when the number of submodules is small, this operation could lead to an excessive charge of the healthy cells, increasing the risk of secondary failures. Besides, undesired harmonic content could appear on the output current, degrading the operation of the accelerator. It is then necessary to implement strategies that allow to remove a faulty cell without significantly impacting the operation of the remaining ones and of the converter itself.Accordingly, the purpose of this article is to investigate several of these strategies and assess them. By means of detailed computer simulations, the behaviour of the converter during normal and submodule fault conditions is analysed. Then, several fault-tolerant strategies are described, verified and compared with the aid of simulation tools. The results show the effectiveness of the analysed strategies in avoiding the overvoltage on the healthy submodules after a cell bypass and the little impact of this operation on the quality of the converter output current.