Use of system oscillation to locate the MPP of PV panels

This letter proposes the use of system oscillation in a perturbation-based maximum power point (MPP) tracker to locate the MPP of photovoltaic (PV) panels. Instead of using an explicit perturbation source, the tracker controller is designed to make the overall system self-oscillate, so that the duty cycle of the main switch in the power conversion stage (PCS) is inherently modulated with a small-amplitude variation at a predefined frequency around the required steady-state value. The tracking mechanism is based on comparing the ac component (due to the variation of the duty cycle) and the average value of the input voltage of the PCS to determine the quiescent duty cycle. The proposed technique does not approximate the panel characteristics and can globally locate the MPP under wide insolation conditions. The tracking capability has been verified experimentally with a 10-W PV panel in a controlled setup. Performances at the steady state and during the large-signal change of the insolation level have been studied.     

A novel maximum power point tracker for PV panels using switching frequency modulation

A novel technique for efficiently extracting maximum power from photovoltaic (PV) panels is presented. The power conversion stage, which is connected between a PV panel and a load or bus, is a SEPIC or Cuk converter or their derived circuits operating in discontinuous inductor-current or capacitor-voltage mode. A method of locating the maximum power point (MPP) is based on injecting a small-signal sinusoidal perturbation into the switching frequency and comparing the AC component and the average value of the panel terminal voltage. Apart from not requiring any sophisticated digital computation of the panel power, the proposed technique does not approximate the panel characteristics and can globally locate the MPP under wide insolation conditions. The tracking capability has been verified experimentally with a 10 W solar panel under a controlled experimental setup. Performances under the steady state and in the large-signal change of the insolation level will are given.     

Neural-network-based maximum-power-point tracking of coupled-inductor interleaved-boost-converter-supplied PV system using fuzzy controller

The photovoltaic (PV) generator exhibits a nonlinear V-I characteristic and its maximum power (MP) point varies with solar insolation. In this paper, a feedforward MP-point tracking scheme is developed for the coupled-inductor interleaved-boost-converter-fed PV system using a fuzzy controller. The proposed converter has lower switch current stress and improved efficiency over the noncoupled converter system. For a given solar insolation, the tracking algorithm changes the duty ratio of the converter such that the solar cell array voltage equals the voltage corresponding to the MP point. This is done by the feedforward loop, which generates an error signal by comparing the instantaneous array voltage and reference voltage corresponding to the MP point. Depending on the error and change of error signals, the fuzzy controller generates a control signal for the pulsewidth-modulation generator which in turn adjusts the duty ratio of the converter. The reference voltage corresponding to the MP point for the feedforward loop is obtained by an offline trained neural network. Experimental data are used for offline training of the neural network, which employs a backpropagation algorithm. The proposed peak power tracking effectiveness is demonstrated through simulation and experimental results. Tracking performance of the proposed controller is also compared with the conventional proportional-plus-integral-controller-based system. These studies reveal that the fuzzy controller results in better tracking performance.     

CMOS integrated MPP tracker with analog power measurement at the PV converter input

An integrated converter controller with maximum power point (MPP) regulation in 0.35 μm CMOS for photovoltaic (PV) applications is reported. The implemented MPP tracker bases on a perturb and observe algorithm and acquires the information concerning the power flow via an analog processing circuit which is connected at the switched mode converter input respectively the output of the attached PV string of nine cells. There the solar cell current is measured via a very low-ohmic shunt resistor of 1 mΩ and analogously multiplied with the cell voltage. As output the fabricated test chip directly generates a 530 kHz PWM signal for the external switched mode converter. Measurements show that under similar conditions analog MPP tracking of the converter input power improves the robustness with respect to settling times of the power path compared to those topologies at which the power is measured at the converter output. Between 0.4 and 7.5 A photocurrent the chip achieves tracking efficiencies better than 99.5 % while the power consumption is only 750 μW and a very low chip area demand of 0.043 mm² for the MPP tracking core is achieved.     

A comparative study of maximum-power-point trackers for photovoltaic panels using switching-frequency modulation scheme

A comparative study of the maximum power point trackers using a switching-frequency modulation scheme (SFMS) for photovoltaic panels is presented. Some commonly used dc/dc converters, which are applied for the power conversion stage of those trackers, will be examined. Method of locating the maximum power point (MPP) is based on injecting a small-signal sinusoidal perturbation into the switching frequency of the converter and comparing the ac component and the average value of the panel's terminal voltage. Apart from not requiring sophisticated computation of the panel power, this SFMS does not approximate the panel characteristics and can globally locate the MPP under wide insolation conditions. Tracking capability of the converters under investigation will be compared, using a 10-W solar panel with a controlled experimental setup. Theoretical predictions will be verified with experimental results. Operating characteristics at steady state and in large-signal change of the insolation (incident solar radiation) level will be studied.     

A PSO‐based maximum power point tracking for photovoltaic systems under environmental and partially shaded conditions

To increase the efficiency of photovoltaic (PV) systems, maximum power point (MPP) tracking of the solar arrays is needed. Solar arrays output power depends on the solar irradiance and temperature. Also the mismatch phenomenon caused by partial shade will affect the output power of solar systems and lead to the incorrect operation of conventional MPP tracker. Under partially shaded conditions, the solar array power–current characteristic has multiple maximum. This paper presents a maximum power point tracking (MPPT) with particle swarm optimization method for PV systems under partially shaded condition. The performance of the proposed method is compared with perturb and observe (P&O), improved P&O, voltage‐based maximum power point tracking and current‐based maximum power point tracking algorithms, especially, under partially shaded condition. Simulation results confirm that proposed MPPT algorithm with high accuracy can track the peak power point under different insolation, temperature and partially shaded conditions, and it has the best performance in comparison with four mentioned MPPT algorithms. Also under rapidly changing atmospheric conditions, the P&O algorithm is diverged. Copyright © 2013 John Wiley & Sons, Ltd.     

Steady-state analysis and design of a buck zero-current-switchingresonant DC/DC converter

An analytic basis is provided for a buck high-efficiency high-frequency zero-current-switching resonant DC/DC power converter. The current and voltage waveforms are derived for the steady-state operation. Design equations are then introduced for the switch duty cycle, maximum switching frequency, DC transfer function, peak currents and voltages, output power, and power conversion capability. Finally, the design procedure is presented along with the advantages and disadvantages of the converter, which are discussed in detail     

Novel ZVS DC-DC converter with low current ripple for light rail transit

This paper develops and studies a three-level zero-voltage turn-on converter for providing auxiliary power system in a DC light rail vehicle. The proposed converter includes a three-level circuit and a half-bridge circuit sharing the same power switches on the high voltage side in order to reduce switch counts and distribute total power into two circuits. The Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) with a low voltage rating and a turn-on resistance are adopted in the developed converter in order to decrease conduction losses on power switches. On the secondary side, two inductors and four rectifier diodes are employed to reduce output ripple current and transformer secondary winding turns. A duty cycle control based on the phase-shift pulse-width modulation is used to regulate the output voltage and achieve the wide range of zero-voltage turn-on. Experimental results with a prototype with a 760 V input and a 48V/30A output are provided to verify the feasibility and effectiveness of the developed converter.     

Maximum Power Point Tracking Controller for Thermoelectric Generators with Peak Gain Control of Boost DC–DC Converters

An analog maximum power point tracking (MPPT) circuit for a thermoelectric generator (TEG) is proposed. We show that the peak point of the voltage conversion gain of a boost DC?CDC converter with an input voltage source having an internal resistor is the maximum power point of the TEG. The key characteristic of the proposed MPPT controller is that the duty ratio of the input clock pulse to the boost DC?CDC converter shifts toward the maximum power point of the TEG by seeking the peak gain point of the boost DC?CDC converters. The proposed MPPT technique provides a simple and useful analog MPPT solution, without employing digital microcontroller units.     

基于电流控制的光伏太阳能充电器系统研究

提出一种基于电流控制的最大功率点跟踪方法用于光伏太阳能充电器,以DC/DC变换器中的Boost电路作为开关充电器,系统由一个光伏电池模块、一个基于Boost变换器开关电池充电器和电池组成.采用光伏电池输出电流控制实现系统的最大功率点跟踪,调整占空比,从而使太阳电池阵列输出功率最大,以输出稳定的电压对蓄电池进行充电,可以提高蓄电池使用寿命,有效地提高独立光伏系统的综合效率,降低整个系统的成本.     

Single switch dual output DC-DC converter performance

The performance of the single-switch dual-output DC-DC converter is evaluated. This converter regulates two independent DC outputs supplied from a single DC voltage source using a power semiconductor switch. Two discrete proportional feedback control loops regulate the duration of on switching and off switching. The duty cycle of the switch controls one output voltage, supplied from a low-pass filter, while the switching frequency regulates the other output voltage, supplied from a higher-frequency bandpass filter. The control algorithm is implemented with an Intel 8096 microcontroller. The experimental data demonstrate the actual circuit performance and confirm the simulation results. Both experiments and simulation show that an increase in the load current on the 12 V output results in an increase in the duty cycle, whereas an increase in the load current on the 5 V output results in a change in the switching frequency. The experimental prototype demonstrates operation over a load current range from about 40% to 100% with a ±25% variation in the 24 V input. Full load currents are 12 A and 2.5 A on the 12 V and 5 V outputs, respectively. The switching frequency ranged from approximately 29 kHz to 264 kHz, and the duty cycle ranged from 0.35 to 0.72     

IOT Based Augmented Perturb-and-Observe Soft Switching Boost Converters for Photovoltaic Power Systems in Smart Cities

This paper focuses on IOT based soft switching boost converter based solar energy applications for smart cities and making cities smarter and greener around the globe. It presents one of the applications of the Internet of Things to design and implementation of a highly efficient boost converter used for powering the Arduino and the Bluetooth device for controlling the switching of the led and buzzer by using smart city applications. The soft switching boost converter is essential to maximize the low-level voltage obtained from the solar board to the enhanced voltage conversion ratio for the efficient electric power generation. In this paper, the three separate methodologies of DC–DC boost converters with additional resonant/snubber circuit and resistive load associated with solar panel modules proposed with maximum power point tracking (MPPT) control. The MPPT is obtained by modified augmented perturb and observe algorithm. IoT helps Smart City(SC) systems to support various network functions throughout the generation, transmission, distribution and consumption of energy by incorporating IoT devices (such as sensors, actuators and smart meters), as well as by providing the connectivity, automation and tracking for such devices. It is utilized to extract the most extreme power from solar panel by controlling the duty ratio of the suggested soft switching based boost converter. In this paper a smart IOT system is used to control and monitoring the effect of reference power variations, parameter values to the voltage control to the converter. The solar panel, boost converter and the MPPT is modeled using MATLAB/SIMULINK environment and reach the power transfer efficiency up to 97%.     

A robust low quiescent current power receiver for inductive power transmission in bio implants

In this paper, a robust low quiescent current complementary metal-oxide semiconductor (CMOS) power receiver for wireless power transmission is presented. This power receiver consists of three main parts including rectifier, switch capacitor DC–DC converter and low-dropout regulator (LDO) without output capacitor. The switch capacitor DC–DC converter has variable conversion ratios and synchronous controller that lets the DC–DC converter to switch among five different conversion ratios to prevent output voltage drop and LDO regulator efficiency reduction. For all ranges of output current (0–10 mA), the voltage regulator is compensated and is stable. Voltage regulator stabilisation does not need the off-chip capacitor. In addition, a novel adaptive biasing frequency compensation method for low dropout voltage regulator is proposed in this paper. This method provides essential minimum current for compensation and reduces the quiescent current more effectively. The power receiver was designed in a 180-nm industrial CMOS technology, and the voltage range of the input is from 0.8 to 2 V, while the voltage range of the output is from 1.2 to 1.75 V, with a maximum load current of 10 mA, the unregulated efficiency of 79.2%, and the regulated efficiency of 64.4%.     

Adaptive duty ratio modulation technique in switching DC–DC converter operating in discontinuous conduction mode

Adaptive duty ratio (ADR) modulation technique in switching DC–DC converter operating in discontinuous conduction mode is proposed in this paper. The proposed ADR modulation technique can regulate the output voltage of the DC–DC converter by generating a series of duty ratios with very simple circuit architecture. The duty ratio is approximately proportional to the square root of the voltage difference between the regulated output voltage and the reference voltage at the beginning of the switching cycle at the light load. As a result, the proposed ADR modulation technique can achieve smaller ripple than the conventional pulse skip modulation over the whole load range. Moreover, the compromise between the light-load ripple and the output power range in the design stage in previous works is solved in the ADR modulation technique. Theoretical analysis, simulation and experimental results are presented to show the operation principle and the advantage of the proposed ADR modulation technique.     

High efficiency,high switching speed,AlGaAs/GaAs P-HEMT DC–DC converter for integrated power amplifier modules

This paper presents a high efficiency, high switching frequency DC–DC buck converter in AlGaAs/GaAs technology, targeting integrated power amplifier modules for wireless communications. The switch mode, inductor load DC–DC converter adopts an interleaved structure with negatively coupled inductors. Analysis of the effect of negative coupling on the steady state and transient response of the converter is given. The coupling factor is selected to achieve a maximum power efficiency under a given duty cycle with a minimum penalty on the current ripple performance. The DC–DC converter is implemented in 0.5 μm GaAs p-HEMT process and occupies 2 × 2.1 mm² without the output network. An 8.7 nH filter inductor is implemented in 65 μm thick top copper metal layer, and flip chip bonded to the DC–DC converter board. The integrated inductor achieves a quality factor of 26 at 150 MHz. The proposed converter converts 4.5 V input to 3.3 V output for 1 A load current under 150 MHz switching frequency with a measured power efficiency of 84%, which is one of the highest efficiencies reported to date for similar current/voltage ratings.     

Frequency tunable low ripple and fast response on-chip DC–DC converter for DVFS

Dynamic voltage and frequency scaling (DVFS) is an efficient method to reduce the power consumption in system on-chip. To support DVFS, multiple supply voltages are generated based on different work load frequencies and currents using on-chip DC–DC voltage converter. In this paper a frequency tunable multiple output voltage switched capacitor based dc–dc converter is presented. An analog to digital converter and phase controller is used in the feedback to change the switching frequency and duty cycle of the converter. An input voltage of 1.8 V is converted to 0.6 and 0.8 V for low and high signal frequency respectively. The proposed 2-phase switched capacitor architecture with gain setting of 1:2 is designed with the 90 nm technology. An output ripple of 45 mV is observed and the maximum transient response time of the converter is 17.3 ns (= 58 MHz).     

A new modulation strategy for a buck-boost input AC/DC converter

This paper presents a novel modulation strategy for a power factor corrected (PFC), isolated AC/DC converter derived from the integration of a nonisolated, two switch buck-boost AC/DC converter with an isolated dual active bridge DC/DC converter (2SBBDAB). This strategy, termed discontinuous leading/trailing edge (DLTE) modulation, serves to maximize the duty cycle of the input switch while keeping the current in the buck-boost inductor discontinuous. Hence, the crest factors of the currents in the switching devices are minimized, the input switch is turned on at zero current and the zero-voltage switching ranges of the bridge switches are unaffected by the integration. A conventional isolated, PFC AC/DC converter typically consists of a boost converter cascaded with a forward converter. The ratings required of the power switching devices of the 2SBBDAB employing the DLTE modulation strategy are similar to those required of the conventional design for wide line voltage operation. However, the 2SBBDAB converter has higher line voltage surge immunity than that of the conventional design and, unlike the conventional design, it has inherent inrush current limiting. The DLTE modulation strategy may be applied to the family of converters composed of the two switch buck-boost integrated with half and full-bridge forward converters     

Power budgeting of a multiple-input buck-boost converter

The use of a multiple-input buck-boost converter for budgeting power between different energy sources is discussed. It is shown mathematically that the idealized converter can accommodate arbitrary power commands for each input source while maintaining a prescribed output voltage. Power budgeting is demonstrated experimentally for a real converter under various circumstances, including a two-input (solar and line-powered) system. A closed-loop control example involving simultaneous tracking of output voltage and set-point tracking of the solar array shows that an autonomous system is realizable.     

基于双并联Boost电路的光伏系统最大功率点跟踪控制方法

光伏电池的输出功率取决于外界环境（温度和光照条件）和负载状况,需采用最大功率点跟踪（MPPT）电路,才能使光伏电池始终输出最大功率,从而充分发挥光伏器件的光电转换效能.在比较了常用光伏发电系统控制的优缺点后,依据MPPT控制算法的基本工作原理,主电路采用双并联Boost电路,具有电压提升功能,并且能够提高DC-DC环节的额定功率和减小直流母线电压的纹波.针对传统扰动观察法存在的振荡和误判问题,提出了一种新型的基于双并联Boost电路的改进扰动观察法最大功率跟踪策略.在Matlab/Simulink下进行了建模与仿真,仿真结果表明,当外界环境发生变化时,系统能快速准确跟踪此变化,避免算法误判现象的发生,通过改变当前的负载阻抗,使之与光伏电池的输出阻抗等值相匹配采满足最大功率输出的要求,使系统始终工作在最大功率点处,并且在最大功率点处具有很好的稳态性能.最后通过实验验证了该算法的有效性.     

Development of a microcontroller-based, photovoltaic maximum powerpoint tracking control system

Maximum power point tracking (MPPT) is used in photovoltaic (PV) systems to maximize the photovoltaic array output power, irrespective of the temperature and irradiation conditions and of the load electrical characteristics. A new MPPT system has been developed, consisting of a buck-type DC/DC converter, which is controlled by a microcontroller-based unit. The main difference between the method used in the proposed MPPT system and other techniques used in the past is that the PV array output power is used to directly control the DC/DC converter, thus reducing the complexity of the system. The resulting system has high-efficiency, lower-cost and can be easily modified to handle more energy sources (e.g., wind-generators). The experimental results show that the use of the proposed MPPT control increases the PV output power by as much as 15% compared to the case where the DC/DC converter duty cycle is set such that the PV array produces the maximum power at 1 kW/m² and 25°C