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At present, the single stage inverters are popular in integrating large-scale solar farms with distribution networks that demand higher dc bus voltage. The elevated dc potentials would degrade the reliability of the solar panels and inverter modules. In this work, the multiboost solar inverter topologies of three variants are presented for grid-connected applications. Since the proposed topologies aim to achieve higher voltage boost at ac side with reduced dc bus potential, it is required to use asynchronous switching strategies, unlike parallel inverter configurations. Although the proposed topologies are advantageous in-terms of improved reliability of solar panels and inverter modules, but instantaneous characteristic impedance imbalance due to asynchronous switching provokes circulating current within the inverter modules. Since the circulating current is undesirable concerning power quality and thermal aspects, in this work, the method of instantaneous impedance balance is ensured with the specially designed switching algorithm for proposed topologies. The eliminated instantaneous circulating current provides the flexibility of operating all inverter modules with the common dc bus. The proposed high gain boost configurations and switching methodologies are demonstrated on hardware prototype by pumping 2.4-kW power to the grid. [ABSTRACT FROM AUTHOR]

This article proposes a high-gain transformerless three-port converter (TPC) for standalone photovoltaic (PV) systems. The TPC is designed and developed based on a dual-inductor high-gain two-port converter by utilizing one of the buffer capacitors to derive the third part for PV input. A hybrid pulse-frequency modulation scheme unified with a pulsewidth modulation control strategy is adopted, which realizes the maximum power point tracking control, load voltage regulation, and bidirectional energy flow at the battery port. The proposed TPC offers the unique advantages of high voltage gain, continuous battery port current, reduced power semiconductors, lower voltage stresses, common ground shared by all the ports, low-cost gate driver, and small size of the rear-end inductor. The working principle, steady-state characteristics, small-signal models, and the control method, including design conditions, are comprehensively analyzed. The correctness of the theoretical analysis is verified by developing a 300-W experimental prototype, which shows that the maximum efficiency is 97.7%. [ABSTRACT FROM AUTHOR]

This article proposes and implements an optimized omnidirectional wireless power transfer (WPT) system using distributed transmitter coils. Under the consideration of practical WPT applications which involve human safety concerns, such as daily home apparatus or wireless rechargeable medical implants, the proposed system can achieve the shortest charging time within the safe limits of human exposure to radiofrequency electromagnetic energy. Based on the calculation of the magnetic intensity generated by multicoupling WPT systems, a more processable magnetic threshold model is presented and analyzed based on the common standard. A newly developed optimization model of the transmitter currents and accordant control strategy is designed and presented to realize both maximum power tracking and flux suppression at target positions. The double-resonant circuit topology with LCC compensation is adopted to reach the stable and synchronized transmitter currents. The cross-coupling problem in multiinput WPT systems will be solved as well. Full-range magnitude control is realized with a single controller and direct current (dc) power supply. The hybrid frequency pacing technique is adopted for lower switching frequency and higher system efficiency under weak coupling operations. Taking practical wireless rechargeable medical implant as the research object, both simulation and experimental results validate the feasibility and the prospect of the proposed system. [ABSTRACT FROM AUTHOR]

Flexible power point tracking (FPPT) aims to regulate the output power of photovoltaic (PV) systems to a predefined value to enable grid support functionalities, such as virtual-inertia provision. Even though partial shading is a common condition in PV systems, especially in small-scale residential PV systems, the current literature, only investigates FPPT control under uniform shading conditions. This article proposes a novel global FPPT (GFPPT) algorithm to provide two functionalities in PV systems under partial shading conditions: first, constant power control (CPC), in which the PV power is regulated to predefined reference value, and second, power reserve control (PRC), under which a constant power reserve is kept in the PV system under steady state to enable grid support under transients. The conventional global maximum power point tracking (GMPPT) algorithm is also modified to adapt with the proposed GFPPT algorithm. The aim of such modification is to obtain faster dynamics after the detection of any environmental changes. Experimental results under dynamically changing partial shading conditions verify the effectiveness of the proposed algorithm in providing CPC or PRC functionalities in PV systems. [ABSTRACT FROM AUTHOR]

The growing demand for energy and environmental concerns have attracted attention to renewable energy sources. In photovoltaic and fuel cell power generation systems, maximum power point tracking (MPPT) is required to achieve high efficiency. This article proposes an MPPT methodology, exploring the characteristics of an interleaved boost converter with switching cell and switching frequency modulation, enabling the operation without current sensors and with only one voltage sensor. In this converter, the input current is proportional to the input voltage and the switching period, making it a voltage follower, with the advantage of self-balancing current and no output voltage distortion in the input current. This article presents comparisons with other techniques, the mathematical analysis with the nonidealities included, the proposed MPPT principle of operation, and numerous experimental evaluations. The converter is analyzed for both single and combined variations in the irradiance and the temperature, ranging from 0 to 1000 W/m2 and from 0 to 85 °C, with fabricated and real measured scenarios, resulting in a stable operation, high efficiency, and fast response. The MPPT mean efficiency, when evaluated with measured irradiance and temperature variations representing a complete operational day, is 99.30%. The converter has a maximum efficiency of 97.80%. [ABSTRACT FROM AUTHOR]

Intrinsically safe power converters have been highly demanded in many harsh industrial environments, such as gas stations, chemical plants, and mine tunnels, to realize accurate voltage or current regulations with minimum safety risks. Communication among different devices is the key to realizing important operations, such as coordinated control, fault detection, and state update, for intrinsically safe converters. In this article, a capacitor current pulse train (CC-PT) control strategy is designed to increase the dynamic response of dc–dc converter with intrinsic operational safety. An orthogonal frequency-division multiplexing (OFDM) based power and signal synchronous transmission (PSST) method is then proposed. The mathematical models of signal modulation are established, and the intrinsic safety region is drawn in the L–C parameters plane, considering the requirements of electric performance, the inductor disconnection discharging, and output short-circuit tests. Simulations and prototype experiments are conducted and presented to verify the feasibility of the OFDM-based PSST in the CC-PT-controlled buck converter with intrinsically safe parameters. [ABSTRACT FROM AUTHOR]

This article exhibits an output voltage-derivative observer-based output voltage-tracking technique for dc/dc boost converters without current feedback, taking the model-plant mismatches (caused by parameter and load variations) and model nonlinearity into consideration. In contrast to extant passivity-based approaches, the proposed solution includes observers to estimate the output voltage derivative and does not require exact model information, which offers a few features: converter parameter information-free output voltage-derivative observers including the modified disturbance observation algorithm for improving the high-frequency disturbance rejection capability as a replacement of the estimation error integral actions, and the observer-based output voltage and its derivative error stabilizer with a damping adaptation mechanism assigning the desired energy function to the closed-loop system. Experimental verification is provided to demonstrate the practical advantages of the proposed solution using a 3-kW bidirectional converter. [ABSTRACT FROM AUTHOR]

The integrated circuits employed for power management in photovoltaic (PV) energy harvesting applications are required to perform an efficient maximum power point tracking (MPPT) process for maximizing the power production of the PV source during the continuously changing atmospheric conditions. Among the alternative MPPT methods, the perturbation and observation (P&O) technique has the advantages of operational and implementation simplicity. In this article, a novel PV MPPT control system for on-chip implementation of the P&O MPPT method is presented, which, compared to the past-proposed on-chip MPPT systems, has the advantage that it is implemented based on purely digital CMOS circuits without requiring the use of complex circuits, such as multipliers, sample and hold units, or analog-to-digital converters. Therefore, it can be easily implemented on-chip with low design complexity while simultaneously retaining the high-performance features of the P&O MPPT technique. The proposed PV MPPT system has been fabricated using the XFAB XH018 0.18-μm CMOS technology. The experimental results verify the successful operation of the on-chip PV MPPT control unit and its ability to achieve a high MPPT efficiency over a wide range of operating solar irradiation values. [ABSTRACT FROM AUTHOR]

The laser power transfer system is one of the most promising systems in the long-range wireless power transfer field. However, the low efficiency at photovoltaic (PV) receiver limits the performance of an implemented system due to the Gaussian laser beam. Since the irradiance profile of the Gaussian laser beam is not uniform, the PV array exhibits complex output characteristics with multiple peaks, leading that the conventional maximum power point tracking (MPPT) method is not acceptable either on tracking accuracy or on tracking speed. In this article, a simple and rapid voltage-location global MPPT (VL-GMPPT) method is proposed for PV array under Gaussian laser beam condition (GLBC) in terms of reducing the voltage searching range. In order to do so, the mathematical model of PV array's global maximum power point (GMPP) is developed under GLBC. Then, the VL-GMPPT method incorporates voltage-location mechanism to directly move the operating point to the vicinity of GMPP and employs IncCond method to accurately find the GMPP. The experimental and simulation results are shown to verify the proposed GMPPT method. It was found that the proposed method can reduce 90% of tracking time that is consumed by the conventional global searching method. [ABSTRACT FROM AUTHOR]

This article presents a low-overhead energy harvesting and delivery system (EHDS) with pulse frequency modulated (PFM) integrated voltage regulator (IVR) power conversion and self-tuned maximization of system output power. A novel load-inclusive time-based maximum power point tracking (LI-TB-MPPT) is developed to provide centralized tuning of PFM-IVR operation based on both source capabilities and load demand on-the-fly, and a configurable fractional sample and hold circuit provides adaptive harvesting window control. The proposed EHDS enables robust harvesting while relieving the use of high passives, with over two orders of magnitude reduction, at the cost of only slight decrease in end-to-end efficiency compared to prior works. Furthermore, a low-overhead wake-up assist circuit utilizes cold-configuration of harvesting sources for efficient and accelerated cold-start. The proposed EHDS is demonstrated in a 65 nm CMOS process with commercial photovoltaic energy harvesting modules. Using only 1.2 and 1 $\mu$ H of passives, measured results show a peak 74.9% end-to-end efficiency (simulated up to 85% at 47 $\mu$ H) and a fast startup time of 3.8 ms. Up to 15% increase in conversion efficiency against load and input voltage variations is achieved with LI-TB-MPPT. The results demonstrate a compact solution for self-sustained cost-restricted stand-alone systems. [ABSTRACT FROM AUTHOR]

This letter introduces a fully integrated inductive power converter for thermal energy harvesting using the thermoelectric generator (TEG). With a three-step self-start block, the power converter can cold-start from 83 mV. After self-start, the minimum input voltage to sustain the power converter operation is only 6.4 mV. An integrated maximum power point tracking block keeps impedance matching at the TEG output. A novel low-power zero-current switching block realizes accurate switching with little overhead. The proposed power converter is implemented in a 55-nm CMOS process and achieves 81% peak end-to-end efficiency. [ABSTRACT FROM AUTHOR]

To design simple and efficient inductive power transfer (IPT) systems, a minimum number of conversion stages and an effective maximum efficiency tracking (MET) are the primary design criteria. The MET control uses a fast mutual inductance estimation (MIE) algorithm to achieve fast tracking of the maximum efficiency point, especially when the variation of the gap distance and misalignment of the magnetic coupler are significant. The feedback control of the MET-MIE IPT system should be designed without a wireless communication channel to improve stability and robustness. In this article, a novel MET-MIE control strategy is proposed for achieving simplicity and high efficiency in IPT systems. Verifications are provided by simulations and experiments. It is shown that maximum efficiency can be tracked with less than 4% error in MIE under significant variation of the gap distance and misalignment of the magnetic coupler. [ABSTRACT FROM AUTHOR]

The commercialization of renewable energy sources is often obstructed due to the cost of energy storages such as batteries, which are unavoidable due to intermittent nature of these energy sources. Average power density and low cycle life of batteries lead to frequent replacement and put additional economic burden toward the replacement cost at its end-of-life. The battery supercapacitor-hybrid energy storage system (BS-HESS) with efficient energy management system (EMS) has shown the potential to improve the battery life in various applications. Here, we exploit the Pontryagin's minimum principle (PMP) for optimal power-split between battery and supercapacitor in HESS for a stand-alone photovoltaic assisted agricultural feed mill such that the battery life is improved. Also, we employ a new technique called hybrid maximum power point tracking, by introducing an extra term in the performance index, to take care of the effects of partial shading and provide fast response to sudden change in solar irradiance. We verify the effectiveness of the proposed PMP-based EMS via simulation and comparison with conventional methods. Simulation results show that the HESS along with PMP-based EMS can improve the battery cycle life compared to rule-based EMS and battery-only storage. Finally, we implement the proposed PMP-based EMS in hardware prototype to prove its practicality. The results obtained are satisfactory. [ABSTRACT FROM AUTHOR]

Doubly grounded transformerless grid-connected inverters are widely used in the PV application because of no common mode leakage current. A boost converter should be added into the doubly grounded PV inverters under shading condition to have boost function. However, the inverter with boost capability is a two-stage system and all switches are operated at high frequency, which reduce efficiency of the system. In addition, processing power of the boost converter is high. Therefore, a single-stage doubly grounded transformerless PV grid-connected inverter with boost function is proposed. The proposed inverter consists of two boost and one buck converters. A cooperative control method among different periods is proposed to reduce processing power of the boost converter and simplify the two-stage system to a single-stage system in each period. In addition, only one switch is operated at high frequency in each period, so efficiency of the system can be improved. Operating principle of the proposed inverter is illustrated. Control strategy is designed. Filter design guidelines and example are given. Loss calculation of the proposed inverter is given. Simulation and experimental results of the proposed inverter verify the theoretical analysis. Finally, comparison among other inverters and the proposed inverter is provided. [ABSTRACT FROM AUTHOR]

Maximization of solar energy harvest and miniaturization of dc–dc converters are essential for low earth orbit (LEO) CubeSats, which are constrained by volume and weight restrictions. The state-of-the-art electric power system (EPS) architectures utilize several individual dc–dc converters to maximize solar energy harvest but it has a tradeoff with miniaturization as it requires several inductors. The main objective of this article is to propose a single-inductor-based multiport converter topology for the LEO CubeSat's EPS. The proposed topology interfaces the photovoltaic (PV) panels to the energy storage system and a control strategy have been developed to extract maximum solar power from each PV panel under wide varying irradiation conditions of the LEO CubeSat. The proposed topology consists of series-connected half-bridge modules fed by PV panels and their output is supplied to the energy storage system via a boost converter. The principle of operation is introduced followed by steady-state analysis and converter dynamics analysis. The performance of the proposed converter is verified for several case studies with an experimental prototype developed based on 1U CubeSat specifications. [ABSTRACT FROM AUTHOR]

The maximum power point tracking (MPPT) is an essential function of the PV power system to achieve the maximum PV power utilization. Traditionally, the MPPT can be realized by a duty cycle modulated dc–dc converter. However, if the LLC resonant converter is considered for the PV power system, the frequency-modulated MPPT algorithm should be adopted. Several strategies such as the frequency-based perturbation and observation (P&O) method and the center point iteration (CPI) method were proposed for the LLC resonant converter. However, with the conventional P&O method, there will be a tradeoff between the tracking speed and the oscillation phenomenon. Besides, the CPI method is unable to maintain the maximum power output under varying environmental conditions. In view of this, an optimal frequency-modulated hybrid MPPT algorithm is proposed in this article. First, the proposed frequency-modulated impedance-matching (FMIM) method is developed to track an optimal operation point under present environmental conditions. Then, the P&O concept will be utilized to ensure maximum power harvesting from the PV array. On the other hand, the operation point calculated via the FMIM is very close to the real MPP. Therefore, the perturbation amount of the P&O method can be minimized to avoid the oscillation around the maximum power point. Operational principles and thorough mathematical derivations are also developed. Finally, both simulation results and hardware verifications obtained from a 500-W prototype circuit demonstrate the performance and feasibility of the proposed MPPT. [ABSTRACT FROM AUTHOR]

Maximum power point tracking (MPPT) is required in PV power systems for the highest solar energy harvest. This article proposes a self-tuning scheme to improve the MPPT performance in terms of high accuracy and speed. The scheme adopts the reinforcement learning (RL) and Beta parameter for the highest MPPT performance. The tracking speed and accuracy are significantly improved since the RL algorithm is enhanced for high convergence speed, meanwhile, the guiding variable $\beta$ is introduced to constrain the exploration space. Simulation and experimental test are applied to validate the superior performance of the proposed solution following the EN50530 dynamic test procedure. [ABSTRACT FROM AUTHOR]

This article presents a cell-level differential power processing IC to maximize the power yield under partial shading and mismatch condition in series-connected single junction photovoltaic (PV) cells. A 3-MHz bidirectional buck–boost converter is employed to realize voltage equalization technique forcing the PV cells to constantly operate close to their maximum power points. A novel and simple low-power low-area analog control circuit is proposed to maintain the high system efficiency at low and high levels of mismatch by obviating the need for power hungry blocks such as analog to digital converters, digital to analog converters, op-amps, saw-tooth generator, and regulators. The voltage of adjacent PV cells is used to drive the high-side switches through bootstrap supplies eliminating the need for voltage regulators. The performance of the proposed IC, fabricated in 130 nm CMOS process, is validated through simulation and experimental results. The converter is capable of processing mismatch currents up to 4 A while the control circuitry consumes less than 40 mW and a system efficiency above 95% is achieved. [ABSTRACT FROM AUTHOR]

In this article, a voltage track optimizer based maximum power point tracking controller for photovoltaic systems under challenging partial shading conditions is presented. The proposed method aims to optimize the operating voltage track while searching for the global maximum power peak (GMPP). This is achieved by bounding the search area by dynamic lower and upper voltage limits. In addition, an improved skipping mechanism is integrated to avoid scanning the unnecessary areas that do not contain the GMPP by exploiting the critical observations in the P–V and I–V curves. Furthermore, the initial operating voltage is exploited to accelerate the tracking speed. By doing so, the voltage track length is drastically reduced, which results in reducing the tracking time. The performance of the proposed method is evaluated against two recent GMPPT methods, namely improved team game optimization and modified maximum power trapezium through MATLAB/Simulink environment. Besides, the simulation results are verified experimentally via a buck-boost converter. The obtained results prove the superiority of the proposed algorithm against the compared algorithms in terms of voltage track length, tracking speed, and transient energy losses. [ABSTRACT FROM AUTHOR]

The objective of this article is to propose a photovoltaic (PV) power and energy storage system with bidirectional power flow control and hybrid charging strategies. In order to optimize the battery charging performance, five charging strategies, including the constant-current charging, the pulse-ripple-current charging, the sinusoidal-ripple-current charging, the bidirectional pulse-ripple-current, and the bidirectional sinusoidal-ripple-current charging, are adopted. Traditionally, in order to realize these charging strategies, the PV charger should abandon the maximum power point tracking function to maintain the power flow balance. As a result, the output power of the PV array will be decreased. Therefore, bidirectional power flow control strategies are proposed to achieve the maximum PV power utilization as well as to realize the hybrid charging methods. In addition, with the proposed strategies, the bidirectional charging/discharging capability of the battery is able to achieve the maximum PV power utilization. All the proposed strategies can be realized by the digital signal processor without adding any additional circuit, component, and communication mechanism. Theoretical analysis and control principles will also be revealed. Finally, a 5-kW prototype circuit with both simulation and experimental results demonstrate the performance and feasibility of the proposed strategies. [ABSTRACT FROM AUTHOR]

A photovoltaic (PV) energy harvesting chip with novel multiplier-based perturb and observe (P&O) maximum power point tracking (MPPT) circuit for Internet-of-Things applications is proposed, and it can be powered by only a small PV module. The proposed P&O MPPT circuit can accurately detect the maximum power point of the PV module without using a power-hungry microcontroller or inaccurate analog multiplier. Instead, a high-accuracy pulse-based multiplier is proposed. Its input signals are analog, while its output signal is digital. Moreover, a new MPPT controller based on the proposed multiplier is also presented. The chip was fabricated using a 0.18 μm 1P6M mixed-signal CMOS process. According to the measured results, the available power from the chosen PV module is 0.1–3 mW, the maximum tracking efficiency of the proposed MPPT circuit is 99.3%, and the maximum total efficiency of the proposed harvesting chip is 94.7%. [ABSTRACT FROM AUTHOR]

This article presents a rectifierless synchronized switch harvesting on inductor interface with a novel maximum power point tracking (MPPT) technique assistance for piezoelectric energy harvester (PEH). The proposed MPPT solution captures vibration states through an envelope extractor and then adjusts the rectified voltage to achieve the maximum power harvest. The MPPT method tracks the vibration amplitude through an envelope extractor, which no longer disconnects the PEH from the converter to measure its open-circuit voltage. Hence, energy harvesting and maximum power point finding can be achieved simultaneously. Besides, the MPPT solution was implemented through discrete passive analog components with ultralow power consumption, which can achieve the MPPT operation when the harvester was cold started. The experiment confirms the simplicity and efficiency of the proposed MPPT solution for the PEH, and the maximum MPPT efficiency can reach 99.5%. [ABSTRACT FROM AUTHOR]

This article presents a power-efficient hybrid energy-harvesting system that scavenges energy from solar, vibration, and radio frequency (RF) energy sources and converts into regulated output dc voltage courtesy buck–boost dc–dc converter. The proposed architecture incorporates tetra-paths for maintaining high power conversion efficiency (PCE) over extended input power range (−10 to 30 dBm). A time-domain maximum power point tracking technique is proposed for solar energy harvester. A high-efficiency full wave rectifier is designed for triboelectric rectifier. A 5.8-GHz RF-dc converter with adaptive matching is proposed to increase dynamic range of the input power. The chip is implemented in 0.18-µm bipolar-CMOS-DMOS process. The die area of the chip is 2.8 mm × 5.0 mm, including the pads. The solar and triboelectric energy harvesters achieve a measured peak efficiencies of 75.4% and 92.3%, respectively. The high-power 5.8-GHz RF-dc converter achieves measured PCE of 76% at 30 dBm input power. The low-power dual-band RF-dc converter operating at 900 MHz and 2.4 GHz obtains measured peak efficiencies of 73% and 71.9% at 0 dBm input, respectively. The buck–boost dc–dc converter employed in the proposed hybrid energy harvesting system achieves a measured peak PCE of 94.5%. [ABSTRACT FROM AUTHOR]

This letter proposed an analog control strategy for a flyback microinverter, which can calculate the output power by multiplier-less power calculation circuit, while the maximum power point tracking is realized by controlling the maximum duty cycle of the main switch. The proposed analog control method is quite simple with low cost. It is applied with a 100-W single-phase microinverter in a discontinuous conduction mode, and the simulation and experimental results demonstrate its feasibility. [ABSTRACT FROM AUTHOR]

Grid-connected photovoltaic (PV) systems impose challenges like voltage fluctuations, low system inertia, and power quality issues. The need to tackle these challenges led to the introduction of flexible power point tracking (FPPT), where the PV power output is controlled by an energy management system, rather than solely operating the PV systems on the maximum power point. The requirement of fast transient response implies that algorithms such as the one proposed in this article are desirable. The proposed algorithm uses the secant method to achieve significantly improved results in comparison to the existing methods. The method also simplifies the prediction of variations during changes in the environment and power reference, hence, results in reduced oscillation around the set-point and faster convergence. Experimental validation is presented in this article for supporting the claims. The results in terms of accuracy, convergence rate, steady-state oscillations, and cumulative error are bench-marked against one of the most recent FPPT methods. [ABSTRACT FROM AUTHOR]

Differential power processing (DPP) for photovoltaic (PV) systems can achieve high system efficiency and maintain maximum power production even under mismatched conditions. However, DPP converters applied to large-scale systems have challenges of complicated installation and high voltage ratings. The segmented DPP structure is introduced as a modular approach that utilizes groups of bidirectional DPP flyback converters to maximize PV power generation while minimizing converter power loss. Groups of four DPP converters are combined into a segmented DPP unit with maximum power point tracking (MPPT) control to maximize output power of the unit. The segmented DPP system and control algorithm are verified through simulation and hardware experimentation. Simulation results verify the effectiveness of the control algorithm with multiple segmented DPP units interacting with a typical inverter employing MPPT. Experimental results verify that system efficiency of the segmented DPP unit reaches 96.4% in even lighting conditions, reaches 92.7% in severe partial shading conditions, and shows an increase of up to 14.8% in uneven lighting conditions compared to an equivalent series-connected PV system. [ABSTRACT FROM AUTHOR]

An input-independent and output-series modular dc–dc converter with multiple input ports and high voltage conversion ratio can apply well to medium-voltage dc interface of distributed photovoltaics (PV). However, PV power mismatch will result in output voltage imbalance of the submodules (SMs), which is contrary to the standardized multimodule design. In this article, a multiport modular dc–dc converter with low-loss series LC power balancing unit (PBU) is proposed to address this problem. An isolated dc–dc converter is employed as the SM, which consists of full-bridge (FB) circuit on the PV side and half-bridge (HB) circuit on the grid side. Independent maximum power point tracking can be realized by controlling the phase shift between the FB and the HB, while voltage balancing (or power balancing) of SMs can be achieved by regulating the phase shift between adjacent HBs. Only one inductor and one capacitor are used in the PBU and all the switches of SM turn on with zero-voltage switching, which contributes to the low-cost and low-loss characteristic of the converter. Simulations and experiments are carried out to verify the validity of the theory. [ABSTRACT FROM AUTHOR]

The change in environmental conditions and dynamic loading distort the smooth and stable MPPT operation. Conventionally, boost and boost-derived converters are used for MPPT operations, which inherently display right half plane zero (RHPZ). The presence of RHPZ causes a transient undershoot and overshoot in the output voltages. A tradeoff between bandwidth and stability is another issue with such converters. In order to address these issues, a minimum-phase bipolar converter (MPBC) is proposed to facilitate the MPPT operation. The MPBC is derived by combining the Ćuk and SEPIC converters with some circuit modifications in both of them. These circuit modifications eliminate RHPZ from the proposed MPBC. Due to the minimum-phase behavior, the proposed MPBC can achieve high bandwidth with improved phase margin, which is required for the fast and stable MPPT operation. MPBC can operate at the high load current and provides wide operating ranges for the MPPT operation due to its buck and boost capabilities. The transient analysis of the proposed MPBC is carried out to compare its performance with the conventional bipolar converter. A 600-W scaled-down laboratory prototype is developed and implemented using Texas Instrument TMS320F28335 processor to validate the performance of the MPBC for photovoltaic systems. [ABSTRACT FROM AUTHOR]

In this article, a new maximum power point tracking algorithm based on a modified butterfly optimization algorithm has been proposed. The proposed method is capable of differentiating between different partial shading patterns, uniform shading, solar intensity, and load variation conditions with fast convergence speed (CS). Only one dynamic variable is used as a tuning parameter reducing the complexity of the algorithm. The search space skipping method has been proposed to improve the CS. The proposed method is hybridized with a constant impedance method to improve the response time of the system for fast varying load variations. The proposed method has been validated experimentally on the SEPIC converter topology with a sampling time of 0.05 s. The experimental validation proved the average tracking time for different shading patterns is less than 1 s with steady-state efficiency of 99.85% on average. The CS for uniform shading conditions is improved by 47.20%. The response to load variation is also improved by 86.15% and becomes eligible to be utilized for fast varying load variations. Finally, the comparison table based on the MPPT rating has been presented to determine the effectiveness of the proposed method among other popular metaheuristic approaches used for MPPT. [ABSTRACT FROM AUTHOR]

Dynamic performance of maximum power point tracking (MPPT) algorithms is important to ensure high-power output under practical operating conditions. In this article, after reviewing three dynamic test procedures, including stepped operation procedure, day-by-day operation procedure, and EN50530 dynamic test procedure, three typical MPPT algorithms such as the fixed-step-size perturb and observe (P&O), variable-step-size incremental conductance, and hybrid-step-size beta method are evaluated experimentally under the EN50530 dynamic test procedure. Two dynamic EN50530 test sequences are adopted for the performance evaluation to cover different irradiance changing conditions. The PV model for EN50530 dynamic test sequences is built, and the effects of wrong-step changes by using three MPPT algorithms are analyzed systematically. The experimental comparison of three MPPT algorithms in terms of the tracking routines, accumulated energy, and tracking efficiency is presented. The research shows that the 0.5% fixed-step-size P&O may fail to track the MPP due to the tracking drift, whereas the beta algorithm exhibits the highest tracking efficiency under both dynamic sequences. The average tracking efficiency improvement of the beta algorithm compared with other two algorithms are experimentally measured as $\text{24.2}\%$ and $\text{18.8}\%$ , respectively. [ABSTRACT FROM AUTHOR]

The output power of each photovoltaic (PV) module is different in the single-phase cascaded H-bridge (CHB) PV grid-connected inverter due to irradiance intensity, ambient temperature, and aging degree of PV modules. When the PV modules are operating at their respective maximum power points, the corresponding dc-side voltages of the H-bridge units drift due to uneven power distribution, which will cause the maximum power point tracking failure. As a result, the grid current will deteriorate and even the system will become unstable. The power routing control methods based on fundamental voltage reconstruction, third harmonic injection and hybrid pulse width modulation can realize unequal power distribution between H-bridges to ensure the system stable operation. This article summarizes the abovementioned typical power routing control methods, derives the expressions of power routing ranges of different methods, then comprehensively and deeply compares the power routing capabilities of various methods qualitatively and quantitatively. The simulation results of a single-phase seven-level CHB PV grid-connected inverter demonstrate the validity of the theoretical analyses. [ABSTRACT FROM AUTHOR]

This article proposes a portable thermoelectric canteen system used for generating electricity while heating. A new step-shape bottom is designed, helping the canteen to be more evenly heated. The proposed canteen is a medium power and temperature difference (MPTD) system, whose main challenge is to keep system always operate at the maximum power point (MPP) when the temperature changes fast. To tackle this problem, this article proposed a new algorithm structure considered the transient response of the current. When an abnormal change in the current is obtained, $X$ is multiplied with the voltage at time $t$ , helping the operation point to relocate near the MPP quickly. The new algorithm structure can be applied with most existing thermoelectric maximum power point tracking (MPPT) algorithms, increasing the tracking efficiency. Furthermore, this article proposes an MPTD-specialized MPPT algorithm based on the new structure. The new algorithm uses the derivative of the power with respect to voltage and current to multiply the reference step $S$. When the temperature difference is 38  $^\circ$ C, the highest power of 0.7469 V and 70.0667 mW, respectively, can be achieved through the MPTD-specialized method. The tracking efficiency is 42.51% higher compared with the classic perturb & observe (P&O) algorithm. [ABSTRACT FROM AUTHOR]

Partial shading is an important subject for the research community to improve the issues in the field of solar array utilization. Shading decreases the life of photovoltaic array, its output power yield, and also generates several peaks in its P–V characteristic curves. Physical relocation of panels can be used as a practical solution to prevent such problems by altering the location of panels but not its electrical circuit. In this article, a reconfiguration technique for all conventional configurations like, series-parallel, bridge-link, honey comb, and total cross tied connections are proposed to reduce current difference between the rows and to improve the irradiance equalization by dispersing the shade. This article proposes a mathematical Tom-Tom puzzle pattern for $5\times 5$ array to enhance the output parameters. The performance of all configurations is evaluated with artificially generated shading to resemble moving clouds which are incremented progressively in row-wise and diagonal manner. From the extensive analysis of results, it has been found that the proposed reconfigurations show better performance than its respective static configurations. The proposed configuration is also tested in terms of income generated and a comparison with the existing state-of-art methods to show the supremacy of the proposed approach. [ABSTRACT FROM AUTHOR]

In a two-stage single-phase photovoltaic (PV) grid-connected inverter, the second harmonic current (SHC) in the PV panel will affect the maximum power point tracking operation and degrade the energy harvesting efficiency. In order to solve this problem, a flying capacitor clamped (FCC) boost three-level (TL) converter is adopted in this article, and the flying capacitor is employed to compensate the SHC for removing a large electrolytic capacitor. The propagation mechanism of the SHC is analyzed from the perspective of impedance, and a virtual impedance in parallel with the intermediate dc bus is introduced, achieving a perfect SHC compensation performance. The implementation of the virtual parallel impedance is illustrated, and the key parameters design of the FCC boost TL converter is given. A 3-kW two-stage single-phase PV grid-connected inverter is fabricated and tested, and the experimental results verify the validity of the theoretical analysis and the proposed control scheme. [ABSTRACT FROM AUTHOR]

Offshore wind is a rapidly growing renewable energy resource. Harvesting offshore energy requires multimegawatt wind turbines and high efficiency, high power density, and reliable power conversion systems to achieve a competitive levelized cost of electricity. An integrated system utilizing one active and multiple passive rectifiers with a multiport permanent magnet synchronous generator is a promising alternative for an electromechanical power conversion system. Deployment of the integrated systems in offshore wind energy requires maximum power point tracking (MPPT) capability, which is challenging due to the presence of numerous uncontrolled passive rectifiers. This article shows feasibility of MPPT based on a finding that the active-rectifier d-axis current can control the total system output power. The MPPT capability opens up opportunities for the integrated systems in offshore wind applications. [ABSTRACT FROM AUTHOR]

In this article, an adaptive frequency control scheme of a sensorless-receiver inductive wireless power transfer system for battery charging applications is proposed. The mixed-compensation topology is utilized instead of the conventional topologies to deliver power more efficiently. Perturb and observe is proposed to track the optimal operating frequency to achieve maximum transfer efficiency or maximum output power delivery. Moreover, the paper proposes a highly accurate analytical model considering the nonlinear effect of the ac/dc rectifier-stage. Two subsystems are considered: a rectifier based resistive-load, and a rectifier based battery-load. The rectifier based battery-load is represented as a variable ac voltage source. The proposed model is linearized using the first harmonic approximation technique and generalized using the Thévenin's equivalent representation, thus the proposed model can be applied to any compensation topology. Afterward, a systematic approach is developed based on the proposed model to estimate the connected load information including battery voltage based on sender-side measurements only. This results in a smaller size and increased portability of the receiver. A prototype is designed in small-scale with low-power specifications to comply with implantable biomedical applications to demonstrate and validate the proposed model, estimation approach, and frequency tracking experimentally. [ABSTRACT FROM AUTHOR]

This article presents a multicell reconfigurable multi-input multi-output (MR-MIMO) power conversion architecture for multiport applications such as multisource energy router, battery balancer, and photovoltaic optimizer. The MR-MIMO architecture couples a large number of modular dc–ac cells with a single magnetic core which processes multiway bidirectional power flow. The system voltage and current ratings can be linearly extended and reconfigured by connecting the dc–ac cells in series or parallel. The MR-MIMO architecture decouples the voltage rating and current rating of the basic cells, and offers much lower device stress than traditional wide-operation range multiport dc–dc converters. The key contributions of this article include: 1) a multicell reconfigurable 12-winding MIMO converter with high performance across a wide range; 2) a hybrid time-sharing and phase-shift control strategy; and 3) a systematic method of designing multiwinding PCB transformers. The MR-MIMO architecture allows one power converter being used for multiple purposes through software reconfiguration. The work presented in this article proved that it is possible to gain significantly design flexibility in a multicell reconfigurable architecture without sacrificing the efficiency or power density. A 500-W 4-port energy router with 12 modular cells and a 12-winding transformer has been built and tested to verify the effectiveness of the proposed MR-MIMO architecture. The energy router maintains over 95% efficiency across a wide range of input and output voltage options. [ABSTRACT FROM AUTHOR]

Switch-linear hybrid (SLH) envelope tracking (ET) power supply can achieve high efficiency and high tracking bandwidth simultaneously, and it has two typical forms, namely, series-form and parallel-form. In the series-form SLH ET power supply, the switched-mode converter is expected to output a continuous-wave voltage which can track the load voltage accurately to enhance the overall efficiency, and the buck converter with hysteresis voltage control (HVC) can be utilized. However, the output voltage of the buck converter will go over the hysteresis voltage boundaries, degrading the linearity and efficiency of the ET power supply. In this article, the hysteresis voltage prediction control (HVPC) is proposed to mitigate the problem in the HVC for buck converter. Moreover, in order to further increase the efficiency, the multilevel converter (MLC) is adopted instead of the buck converter for reducing the switching frequency and the inductor root-mean-square current, and the corresponding HVPC control strategy is also proposed. A prototype of the series-form SLH ET power supply employing the MLC with HVPC aimed at 5-MHz envelope signal is fabricated in the lab. The measured overall efficiency is 77.5%, a 12% efficiency improvement over that using step-wave switched-mode converter. [ABSTRACT FROM AUTHOR]

This article deals with a photovoltaic-grid integrated system operating an induction motor (IM) coupled to a water pump. A simple dc-link voltage regulation approach is adopted for the power transfer. This system is utilized to primarily feed the induction motor-driven water pump and when water pumping is not desired, the power is delivered to the utility. This system requires two current sensors and two voltage sensors in total for sensing and estimation purpose. Induction motor phase currents are estimated from dc-link current by modified space vector modulation (SVM) technique. The speed estimation in this system is achieved by artificial neural network-based model reference adaptive system with a third-order integrator for flux estimation and is capable of controlling the power flow as per demand. The field-oriented control is used for speed control of an IM-pump. A third-order integrator based unit voltage generation algorithm is used to control the power transfer in both the direction between utility and the IM drive with water pump by regulating dc-link voltage. The appropriateness of the system is justified by simulated results on MATLAB/Simulink platform and test results procured with the help of a developed prototype during varying solar irradiances. [ABSTRACT FROM AUTHOR]

Due to the inherent double-frequency (2f0) ripple in single-stage single-phase photovoltaic grid-connected inverters, the maximum power point tracking (MPPT) will inevitably be affected. To improve the MPPT performances, a passive LC power decoupling circuit with a robust second-order sliding-mode control (SOSMC) is thus proposed in this article. With the passive LC decoupling path, the double-frequency pulsation on the dc link is effectively cancelled out. Thus, the MPPT accuracy is significantly enhanced, and the utilization of a small dc-link capacitor becomes possible. However, resonance between the LC circuit and the main dc-link capacitor may appear, which can be damped through an active damping method. Additionally, the proposed SOSMC ensures good steady-state, dynamic performance (voltage fluctuation and settling time), and the robustness of the dc-link voltage, which is also beneficial to MPPT control in terms of high accuracy and fast dynamics. The systematic design of SOSMC is presented, and a detailed parameter optimization design of LC decoupling circuit is discussed. Experimental tests are performed on a 2.5-kW single-stage single-phase grid-connected inverter, and the results validate the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

To overcome the shortcomings of the conventional continuous control set model predictive current control (CCS-MPCC), such as large overshoot and poor robustness, an extended surface-mounted permanent magnet synchronous motor (SPMSM) model-based multistep error tracking CCS-MPCC (MSET-CCSMPCC) is proposed in this article. First, a traditional CCS-MPCC is derived based on the conventional SPMSM model and its robustness is analyzed by considering the parameter mismatches. Second, an extended SPMSM model is given by incorporating the lumped disturbances into one disturbance part. Third, a sliding mode differentiator improved fast terminal sliding mode disturbance observer is designed to track the disturbances. Fourth, by compensating the extended SPMSM model for the estimated d- and q-axes disturbances, an extended SPMSM model-based CCS-MPCC (EXM-CCSMPCC) is designed. However, the EXM-CCSMPCC has serious step response overshoot. Fifth, an extended SPMSM model-based single step error tracking CCS-MPCC is presented, whose dynamic response and steady-state performances deteriorate when the overshoot is reduced. Finally, an MSET-CCSMPCC is proposed to reduce the overshoot and improve the robustness while maintaining excellent dynamic and steady-state performances. Experiments are implemented on a field-programmable gate array based hardware system to verify the excellent performances of the proposed method. [ABSTRACT FROM AUTHOR]

A major challenge in a photovoltaic (PV) system is to identify the line-to-line faults that occurred under low irradiance conditions, during day-to-night/night-to-day transitions in the presence of blocking diodes. Due to active maximum power point tracker, these faults may not be identified and continue to be hidden even if the system returns to a high irradiance condition, since the magnitude of fault current may be less than the rating of the protection device (fuse). Those uncleared faults may subsequently lead to reduced peak output power, reliability issues, and may even cause fire risks. To address these issues, a method is proposed to identify the pre-existing/undetected faults using the transitory conditions that occur during the preturn on/off condition of the PV inverter (checking mode). From these transitory conditions, the I–V curve of the PV array is exploited without the need for additional components or sensors. Additionally, there is no need to disconnect the PV array from the setup. Moreover, the local minima is tracked, to discriminate the faults and partial shading conditions. The proposed algorithm is tested on a small-scale grid-connected PV system and implemented in LabVIEW. The results demonstrate the efficacy of proposed algorithm in detecting the pre-existing/undetected faults. [ABSTRACT FROM AUTHOR]

An advanced smooth pole tracking technique for a low dropout (LDO) regulator with a ceramic capacitor is presented in this article. Normally, the dominant pole is at the output of an LDO and becomes load dependent, which may cause a loop stability issue during the whole load-current application range. The proposed frequency compensation methodology with adaptive load resistor control of an error amplifier (EA) alleviates the problem and reduces the dependence of equivalent series resistance of an output capacitor. Moreover, combined with this compensation strategy, an ultrafast EA by utilizing a transconductance enhancement technique is proposed to greatly reduce output voltage spikes as well as response time of the LDO during transient. This circuit has been implemented in a 0.18-μm standard CMOS process and occupies an active chip area of 0.017 mm2. Experimental results show that it can deliver 150 mA load current at 200 mV dropout voltage. Good loop stability and transient responses are easily achieved without degrading other important LDO parameters. [ABSTRACT FROM AUTHOR]

We propose a maximum efficiency tracking for a multiple-transmitter system that optimizes both the current ratios of transmitter (Tx) coils and the effective Rx load. It is found that unlike the single-Tx case, the optimal load impedance of multiple-Tx system depends on the current ratios among Tx coils. Meanwhile, the Tx current ratios should be controlled to be the same with magnetic coupling ratios between each Tx and Rx. Hence, we propose a two-step tracking method that first optimizes the Tx current ratios and then optimizes the Rx load impedance. To match the Tx current ratio with the magnetic coupling ratio, it is analyzed that the reflected resistances at every Tx become identical to each other when the Tx coil current ratios are equal to the magnetic coupling ratios. It is also revealed that the reflected resistance at specific Tx is reduced (increased) when its Tx current is increased (reduced) relative to other Tx currents. The proposed feedback equalizes all reflected resistances based on this property. The second step of the proposed tracking is to optimize the Rx load while fixing the Tx current ratios by globally scaling up or down the strengths of whole Tx currents. Maximum of 478 W is delivered at 79% efficiency. The algorithm does not have a limit on the number of Txs except the small standby power consumption. The proposed theoretic analysis and control method enable the first-ever maximum efficiency tracking for multiple-Tx system, where the first step optimizes the relative Tx current ratios and the second step optimizes the load impedance. [ABSTRACT FROM AUTHOR]

Differential power processing (DPP) is regarded as a promising architecture in solving mismatching issues among photovoltaic (PV) submodules. Although conventional total-minimum-power-point (TMPP)-based real-time optimization algorithm by using the distributed submodule-level maximum power point tracking and simultaneously the centralized total-minimum-power tracking shows effectiveness in maximizing the power yield. However, uneven power stress among DPP converters, large oscillations, high additional cost for communication among DPP converters, and complicated implementation hinder the practical application. This article proposed a low-complexity power balancing point-based optimization algorithm to reduce the system cost and size, improve the system efficiency, and realize the standardized modular design for DPP converters. Furthermore, simple submodule-level voltage equalization control is implemented to eliminate expensive communication and relieve the control complexity while guaranteeing high maximum-power-point efficiency. The proposed algorithm can reduce the power rating of DPP converters compared with conventional TMPP-based control, which is beneficial to the improvement of system cost, reliability, and lifetime. Both simulation and experimental results under various scenarios are provided to validate the advantages of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Cascaded H-bridge (CHB) converters characterized with high scalability have been widely used in photovoltaic and energy storage systems. However, the three-phase power and the voltages are often unequal due to various reasons, making the system less efficient. Therefore, the ability to deal with unequal power is necessarily required in CHB. This article proposes three interphase power control methods (PCMs) based on simplified pulsewidth modulation (PWM) strategy to improve the efficiency of the system. A control method with better performance both in dynamic and steady states is adopted to adjust power distribution. The relationship between duration times and dc power is analyzed. On the basis of controlling the interphase power, an inner-phase PCM is proposed by redistributing the duration time of each submodule, to further enhance the power control ability of the system. The simulation and experimental results show that under the condition of balanced or unbalanced voltage, the interphase and inner-phase power can be controlled, which verifies the feasibility and practicability of several modulation strategies proposed in this article. [ABSTRACT FROM AUTHOR]

Most maximum power point trackers (MPPTs) for electromagnetic energy harvesters (EMEHs) are based on resistive matching technology, where the input resistance of the MPPT is made equal to the magnitude of the output impedance of the harvester. This is valid when the output reactance of the EMEH is much smaller than its output resistance. However, some EMEHs, such as permanent magnet generator, have nonnegligible output reactance. The discrepancy between the power extracted by the resistive matching technology and the maximum extractable power will increase as the output reactance increases. Under high excitation frequency and low operating temperature, the effect of the output reactance will become more dominant. In order to deal with such issue, an MPPT that can counteract the effect of the coil inductance and match with the coil resistance is presented. It does not require knowing coil parameters a priori and the harvester will be operated at its true maximum power point. A 7-W prototype for testing the proposed algorithm has been built and evaluated. Its performance is favorably compared with the amount of power extracted with the resistive matching technology. [ABSTRACT FROM AUTHOR]

A novel quasi-two-stage multifunctional inverter (QMFI) for photovoltaic (PV) applications is proposed in this article. With the help of the quasi-two-stage architecture, part of active power can be directly transferred from PV arrays to the grid or load within a single power conversion stage and hence improve the efficiency. In addition to active power transfer, both the realization of maximum power point tracking (MPPT) and compensation of nonactive current (i.e., reactive, harmonic, or unbalanced current) of the QMFI are considered. A mathematical model of the QMFI is presented to guide the control parameter design. Meanwhile, an analysis model based on the rotating frame is proposed to derive the space vector pulsewidth modulation strategy of the QMFI, and also, offer straightforward insight into the influence of nonactive current compensation on quasi-two-stage active power flow. Compared with traditional solutions, the QMFI can realize active power delivery with higher efficiency and also keep functions of achieving MPPT and enhancing power quality. The feasibility and effectiveness of the proposed solution are verified with a 3-kVA prototype. [ABSTRACT FROM AUTHOR]

Optimizing the operational performance of maximum power point trackers during multiple peak partial shading conditions (PSCs) prevails as a major challenge in photovoltaic power generation. Though many of the newly evolved soft computing and heuristic methods are compatible during PSCs, the need for such techniques in uniform irradiation levels is uncertain because most of these algorithms produce extensive oscillations before converging to the global maximum power point (GMPP). On the other hand, adopting conventional perturb and observe (P&O) algorithm is meritorious to reduce the transient power and voltage oscillations. Therefore, this article presents a proficient hybrid tracking technology that provides an adequate tradeoff between conventional P&O and advanced soft computing techniques by accurately detecting shade occurrences. For which, the uniqueness in the operating point conductance of P&O at the leftmost power peak in the P–V curve is utilized. Subsequently, the proposed convention utilizes P&O for two major purposes: to track MPP in uniform irradiance, and to detect PSCs. More importantly, even during PSCs, the detection algorithm is well designed to operate at GMPP with the conventional P&O method itself, and, only for extreme shade cases, flower pollination algorithm is introduced to track GMPP. The pre-eminence of the proposed technology to track GMPP with reduced transient oscillations by discriminating shade occurrences is demonstrated via extensive experimental studies in this article. [ABSTRACT FROM AUTHOR]

In this article, a two-stage maximum power point tracking algorithm is presented to track the global maximum power point of photovoltaic systems in partially shaded conditions. The proposed tracker uses an intelligent sampling procedure based on a fractional open-circuit voltage method and takes initial samples from the power-voltage characteristic of the photovoltaic array. Then, it determines the marginal array power around each sample. Using these marginal powers, the samples that definitely are not in the vicinity of global maximum power point are eliminated, and neighborhood of these samples are not searched in the global search stage. As a result, the search area gets smaller and global maximum power point is found accurately and rapidly. Furthermore, an algorithm is suggested to estimate module voltage at its maximum power point, which is used in the proposed maximum power point tracker. Eventually, several simulations are carried out through MATLAB/Simulink in order to evaluate the performance of the new tracking method and compare it with recently presented methods. Experimental results are also presented to verify the validity of the developed tracker. [ABSTRACT FROM AUTHOR]