Maximum Power Point Tracking Function Research Articles

Synchronous Dual-Switch Ultrahigh Step-Up DC–DC Converter Based on Coupled Inductor and Voltage Multiplier for Photovoltaic Systems

In this article, an ultrahigh step-up quadratic boost converter is proposed for photovoltaic systems. By integrating with a coupled inductor and a voltage multiplier, the voltage gain can be improved significantly without high turns ratio and the voltage stress across the power switches are alleviated. Thus, low on-resistance of the power switches are available to enhance efficiency. Common ground structure of quadratic boost and synchronous operation of the two switches facilitate the control. Also, the continuous input current promotes the maximum power point tracking (MPPT). Detailed description of the operation principles and steady-state analysis of this converter in CCM and DCM are presented. A 250W rated laboratory prototype is fabricated and verified, demonstrating a maximum efficiency of 96.5%. Moreover, the dynamic response is tested to prove the stability of the proposed converter. Finally, a simulation is built to evaluate the feasibility of MPPT function.

Self-sustained and self-wakeup wireless vibration sensors by electromagnetic-piezoelectric-triboelectric hybrid energy harvesting

Self-sustained wireless sensing nodes (WSN) with energy harvesting, low power consumption, and intelligent sensing are the key devices in artificial intelligence of things (AIoT) area. This paper designs a tri-hybrid generator with electromagnetic-piezoelectric-triboelectric units integrated into one vibration energy harvesting structure. The tri-hybrid generator has three functions with electromagnetic unit for power supply with 13.1 mW, two piezoelectric units as the accelerometer for amplitude and frequency sensing with broadband decoupling function, triboelectric unit for triggering the self-wakeup WSN. The tri-hybrid generator structure is simulated and optimized by theory and finite element modeling, and the performance is tested in a vibration platform. To achieve self-sustained WSN, this study designs the power management circuit with maximum power point tracking and undervoltage lock function, combining periodic wake-up with overload self-wakeup to decrease 94.2% WSN power consumption. Self-sustained WSN is realized in the laboratory and verified on the vehicle engine. Finally, the application of wireless vibration sensing is verified on the vehicle engine. This work has a wide range of applications in vibration scenarios and hopefully promotes the development of AIoT.

Exploiting Photovoltaic Sources to Regulate Bus Voltage for DC Microgrids

DC microgrids are highly compatible with photovoltaic (PV) generation because of their direct-current properties. However, with the increasing integration of PV sources into DC microgrids, traditional maximum power point tracking (MPPT) algorithms may cause problems such as overvoltage and power fluctuation, which makes it challenging to keep the stability of the DC-bus voltage due to the intermittent and stochastic nature of PVs. Consequently, in order to reduce the investment and maintenance costs of storage systems, innovative control methods are required for PVs to provide DC-bus voltage regulation services. In this paper, a novel active power control (APC) strategy, based on characteristic curve fitting, is proposed to flexibly regulate the PV output power. The transient process performance and robustness of the system are improved with the proposed APC strategy. Based on it, a V-P droop mechanism is designed to provide voltage regulating (DVR) service for the DC microgrid. The overall control strategy unifies the DVR function with the traditional MPPT function in the same control structure; thus, the PV source either works in the MPPT mode if the DC-bus is at its nominal value, or it works in the DVR mode if the DC-bus exceeds it. Switching between MPPT and DVR is autonomous, and it is fully decentralized, which improves the PV generation efficiency as well as ensures generation fairness among different parallel PV sources. Case studies including a real-world project analysis are carried out to validate the feasibility and effectiveness of the proposed strategy.

Independent MPPT and voltage regulation of dual input DC - DC converter with a voltage multiplier cell

ABSTRACT A dual input boost DC–DC converter (DIBC) with combined voltage multiplier cell, the larger duty ratio (greater than 0.5), and the overlapping switching signal are required to obtain high voltage gain. This paper investigates the independent maximum power point tracking (MPPT) implementation on two solar photovoltaic (PV) energy sources along with the output voltage regulation of the DIBC during load and input voltage disturbances. For maximal power extraction, a single ended primary-inductance converter (SEPIC) is designed at each input, one with the perturb and observe (P and O) approach and the other with the incremental conductance algorithm. The small-signal transfer function model is used to design the voltage regulator. The MPPT algorithms for maximum power extraction as well as the inner current-loop and outer voltage-loop control approach have been implemented simultaneously. Duty ratio of the DIBC MOSFETs as a function of the converter output voltage and duty ratio of the SEPIC MOSFET as a function of MPPT are used to generate the switching signals. An experimental two 100W PV sources are developed using real-time solar simulator with the 200 W DIBC and controller is designed using XILINX SPARTAN-6 FPGA board. MATLAB simulation and experimental results ensure the active current sharing among the sources, reference output voltage (156.6 V) tracking, voltage regulation (below 5%) under different scenarios, and independent MPPT simultaneously.

Studying and analyzing the performance of photovoltaic system by using fuzzy logic controller

The main objective of this paper is to implement a circuit-based simulation model of a photovoltaic (PV) cell in order to investigate the electrical behavior of the practical cell with respect to some changes in weather parameters such as irradiation and temperature. The research focuses on using a simulation model to achieve the maximum power of solar energy by using the maximum power point tracking (MPPT) controller. The circuit simulation model consists mainly of three subsystems: PV cells: DC/DC converter; and MPPT controller-based logic fuzzy control. Dynamic analysis of the system is carried out and the results are recorded. The maximum power control function is achieved with the appropriate power control of the power inverter. Fuzzy logic controller has been used to perform MPPT functions to get maximum power from the PV panel. The proposed circuit was implemented in MATLAB/Simulink and the results show that the output sequence is non-linear and almost constant current to the open circuit voltage and the power has maximum motion to voltage for certain environmental conditions.

Unified control scheme for a dual-stage grid-connected PV system with mode change

This paper proposes a unified control scheme for a dual-stage grid-connected PV system to achieve both the maximum power point tracking (MPPT) mode and the droop mode of operation with mode change. The DC-bus voltage regulation is achieved through the DC–DC converter control, and different modes of operation and the MPPT function are implemented in the DC–AC converter control, where three digital switches are designed to achieve seamless mode change. To enhance system stability and flexibility, a droop coefficient self-tuning algorithm is proposed to handle the scenario with insufficient solar irradiation in the droop mode. The effectiveness of the proposed methods is validated through both experimental and simulation studies.

Development of a Thermal Energy Harvesting Converter with Multiple Inputs and an Isolated Output

In this paper, an isolated multi-input single-output (MISO) converter is developed and applied to a thermoelectric energy conversion system to harvest thermal energy. The thermoelectric generators have individual maximum power point tracking functions. Furthermore, such a converter has a high step-up voltage conversion ratio. In addition, the presented converter is imposed on the thermoelectric energy conversion system with the three-point weighting strategy adopted to realize the maximum power point tracking (MPPT). In this paper, the basic principles of this converter are first described and analyzed, and finally some simulated and experimental results are offered to verify the feasibility and effectiveness of such a thermal energy harvesting system.

Design of a highly integrated wireless power transfer system

A highly integrated wireless power transfer (WPT) system with maximum power point tracking (MPPT) function and output voltage regulation function is presented in this article. One common method to achieve the MPPT function or voltage regulation function is to use the dc–dc converter. However, this method normally increases the volume and weight of the whole system. By utilizing the inner space of the receiving coil and a compact circuit layout, the proposed WPT system can be fully integrated within a low profile and small area. The receiving coils, rectification, filter, dc–dc converter, and control circuits are all integrated on one substrate, and the size of the circuit part is only 5 cm × 5 cm. By using the ground of the circuit as a shield, the interference of electromagnetic field to electronic components is reduced. Finally, the designed WPT system is implemented, fabricated, and validated by the experimental results.

Bidirectional Power Flow Control and Hybrid Charging Strategies for Three-Phase PV Power and Energy Storage Systems

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.

Optimum Parametric Identification of a Stand-Alone Photovoltaic System with Battery Storage and Optimization Controller Using Averaging Approach

The dimensioning of photovoltaic systems is the major concern of researchers and power industry practitioners. This aims to improve energy efficiency and protect the conversion units by a consistent assessment of power conditioning circuits and interconnections for the PV application. In this context, this paper sets out to fulfill detailed modeling and control steps of a standalone photovoltaic (PV) power system with energy storage, according to practical specifications of the load, PV generation unit, and battery pack. The main goal is to estimate all unknown parameters, as the diode ideality factor and revers saturation current, the controller, and the PV link. The PV link interfacing the PV source circuit to the PV-side converter (PVSC) provides a filtering function to maintain a steady voltage at the link. The charge controller used in the PV-side converter is a DC/DC buck converter. It transfers the PV power to the battery and supplies the load. Using pulse- width modulation (PWM) technical, of which the switching duty cycle is the control-input variable; the PVSC power-conditioning circuit is permanently controlled by the maximum power point tracking (MPPT) algorithm to achieve the maximum energy. The battery pack voltage is properly maintained by the charge controller and specified to match the load voltage rating, to avoid a high ratio of voltage conversion. A method is proposed to integrate both the MPPT function and the battery cycle charge. The PV generator output and the power conditioning circuits, mainly constructed from switching- mode power converters, are nonlinear. An averaged model is then derived for dynamic analysis and controller synthesis, using the state-space averaging and linearization method. A PV array of nine PV modules configured into three strings is used in this application to demonstrate the effectiveness of modeling, design, control, and simulation. Simulation model for the controller and power interface is built and developed in short term, using the fundamental blocks of Matlab Simulink.

Application of solar heating system in high-tech enterprises under the photovoltaic industry chain

This article designs a simple experimental training platform for high-tech enterprises to charge solar photovoltaic power generation lead-acid batteries. The platform comprises photovoltaic panels, charge controllers, valve-regulated lead batteries, and varistor box loads, indicating that the solar photovoltaic industry is high-tech, the scope and significance of application in technology companies. On this basis, the article replaces the first-order derivation with approximate gradient calculation and proposes a variable-step voltage disturbance observation method to realize the maximum power point tracking of solar photovoltaic power generation. The simple experimental training platform for high-tech solar photovoltaic power generation lead-acid batteries uses STM8S105 single-chip micro-computer as the controller core while adopting the Buck DC step-down chopper primary circuit, combined with the lead-acid battery four-stage charging method, for system hardware and software design. The experimental test shows that the experimental training platform has maximum power point tracking function, low cost, simple structure, good performance, easy operation, and maintenance, and can meet high-tech enterprises? experimental training requirements.

A Wind Turbine Emulator Using Field-Oriented Induction Motor

This paper proposes a Wind Turbine Emulator (WTE) using an Indirect Field Oriented (IFO) Induction Motor (IM). The IM drive can be controlled as a conventional prime mover in speed mode, or a wind turbine in torque-speed mode via robust observed torque control. This paper presents key issues for establishing a high-performance IFO IM drive. Further, this study develops a wind turbine load Interior Permanent-Magnet Synchronous Generator (IPMSG) followed by a three-phase Vienna Switch-Mode Rectifier (SMR). It receives mechanical driven power from the WTE and establishes a 400V DC-link for the DC micro-grid. The good generating characteristics are achieved through proper controls of both the IPMSG and SMR. Various wind turbine torque-speed and power-speed characteristic curves under different wind speeds can be emulated by the developed WTE. The designed results are verified by simulations. The measured results indicate that the errors are within 1.5% and 1.0%, respectively, for the torque and the power compared to the designed ones. The maximum power point tracking (MPPT) function with good performance for the PMSG with Vienna SMR is achieved using the perturb and observation (P&O) approach. The dynamic and steady-state operating characteristics of the developed whole turbine emulator driven PMSG system are assessed experimentally.

An Adaptive Model-Based MPPT Technique with Drift-Avoidance for Grid-Connected PV Systems

In this article, a modified control structure for a single-stage three phase grid-connected photovoltaic (PV) system is presented. In the proposed system, the maximum power point tracking (MPPT) function is developed using a new adaptive model-based technique, in which the maximum power point (MPP) voltage can be precisely located based on the characteristics of the PV source. By doing so, the drift problem associated with the traditional perturb and observe (P&O) technique can be easily solved. Moreover, the inverter control is accomplished using a predictive dead-beat function, which directly estimates the required reference voltages from the commanded reference currents. Then, the reference voltages are applied to a space vector pulse width modulator (SVPWM) for switching state generation. Furthermore, the proposed inverter control avoids the conventional and known cascaded loop structure of the voltage oriented control (VOC) method by elimination of the outer PI controller, and hence the overall control strategy is simplified. The proposed system is compared with different MPPT techniques, including the conventional P&O method and other techniques intended for drift avoidance. The evaluation of the suggested control methodology depends on various radiation profiles created in MATLAB. The proposed technique succeeds at capturing the maximum available power from the PV source with no drift in comparison with other methods.

A Hybrid Photovoltaic-Fuel Cell-Based Single-Stage Grid Integration With Lyapunov Control Scheme

This article presents a single-stage hybrid photovoltaic (PV)-fuel cell (FC)-based grid-integrated system with Lyapunov function-based controller design to obtain optimal power extraction from hybrid renewable sources without maximum power point tracking (MPPT) application. The proposed Lyapunov controller performs MPPT function, improves power quality, and forces inverter to inject sinusoidal current to the utility grid. In this proposed approach, the higher switching frequency has been reduced by employing LCL filter inclusion compared to the two-stage hybrid power system. This proposed single-stage system has low cost and improved power quality at the point of common coupling and employed controller injects stable power to the utility grid. In this article, a hybrid overall distributed-particle swarm optimization-based MPPT is employed with FCs and integrated CUK converter. The effectiveness of the employed Lyapunov function-based controller has been tested with dSPACE (DS1104) real-time platform for single-stage hybrid grid-connected power system under varying operating conditions that have high efficiency, reduced harmonic distortion in grid current with the simpler employed power converter. Experimental responses confirm the effectiveness of the proposed controller, which transfers the hybrid power from PV and FC to the utility grid through a single stage.

Performance of ACO-MPPT and Constant Voltage Method for Street Lighting Charging System

Electricity consumption continues to increase every year. Alternative energy source such as solar panel have been easily developed and do not cause pollution. By utilizing the sun's rays on its surface, solar panels can produce electricity depending on the level of surface temperature and the conditions of the intensity of solar radiation. Most street lighting electrical systems with conventional solar panels have minimal output power due to not having the Maximum Power Point Tracking (MPPT) function. In addition, the absence of a charging function results in an uncontrolled voltage magnitude affecting the parameters of electrical energy (accumulators), especially when the accumulator's State of Charge (SOC) approaches the full charging limit. Therefore, a system of street lighting is used which is capable of carrying out MPPT functions and charging functions with an electrical system that uses a CUK type DC-DC Converter. Ant Colony Optimization (ACO) algorithm as MPPT control, and the Constant Voltage (CV) method as charging control with measurements, SOC uses the coulomb counting method. The performance has proven to optimize a 200 Watt-peak solar panel power output up to 18.92 Watts, maintain a voltage value with a maximum error difference of 2% only, which can read the battery SOC accurately.

Development of Sustainable Nanogrid Road Lighting Systems

This paper presents the integration of a solar system into road lighting systems based on a nanogrid concept, the traditional road lighting system improvement employing light-emitting diode technologies and solar energy systems. The power quality of the proposed nanogrid road lighting system is studied and analyzed in different modes, namely, stand-alone and grid-connected, using an experimental test set. Additionally, the road lighting equipment and power quality control regulation for the grid-connected system are studied in accordance with the IEC 61000-3-2 (2018) Class C standard. The economic assessment of the proposed road lighting systems is compared with a conventional solar farm system installation in terms of discounted payback period, net present value, and internal rate of return. The results indicate that the system can effectively charge the batteries with a maximum power point based on the maximum power point tracking function and supply the road lighting system through the power from the batteries. In the grid-connected operation, the electrical energy harvested from the solar system can be sent to the electrical grid with the maximum power point. The integration of a solar system into the road lighting system based on the nanogrid concept offers remarkable economic performance in investments. Furthermore, it provides a greater economic feasibility than investing in a solar farm system, as the former is free of land costs.

Module-Integrated Converter Based on Cascaded Quasi-Z-Source Inverter With Differential Power Processing Capability for Photovoltaic Panels Under Partial Shading

Conventional microinverter or module-integrated converter (MIC)-based photovoltaic (PV) systems are prone to be complex and costly because each MIC requires not only a boost converter to bridge a huge voltage gap between a PV panel and grid but also desirably a differential power processing (DPP) converter to preclude partial shading issues. This paper proposes a novel MIC based on cascaded quasi-Z-source inverters (qZSIs) with DPP capability. A traditional qZSI and voltage multiplier (VM)-based DPP converter are integrated into a single unit with sharing active switches and magnetic components, achieving system- and circuit-level simplifications. In addition, a novel control strategy utilizing two control freedoms of shoot-through duty cycle $d_{st}$ and modulation index M to simultaneously perform maximum power point tracking (MPPT) and DPP function, respectively, is also presented. A 150 W prototype for a standard PV panel consisting of three substrings is built, and experimental tests are performed emulating partial shading conditions. The results demonstrate that the proposed integrated qZSI could perform MPPT with satisfactory preventing partial shading issues while generating ac voltage at the inverter output.

Design of Sub-Gigahertz Reconfigurable RF Energy Harvester From −22 to 4 dBm With 99.8% Peak MPPT Power Efficiency

To overcome the low-efficiency and limited working range of the existing RF energy harvesting (EH) systems for the wireless Internet-of-Things (IoT) sensors, a novel reconfigurable system is proposed with integrated hill-climbing, maximum power point tracking (MPPT) function for wide input power from −22 to 4 dBm. A conceptual linear model with high accuracy is also proposed to analyze the rectifier efficiency for MPPT operations. The rectifier with off-chip matching is designed with a patch antenna at 915-MHz the industrial, scientific and medical (ISM) band. To further improve the end-to-end efficiency, the harvested power is used to power up the circuit block in system on a chip (SoC) directly, avoiding additional conversion loss. Our proposed reconfigurable 12-stage rectifier with matching network achieves −18.1-dBm sensitivity for 1- $\text{M}\Omega $ loading and 36% peak efficiency at 1 dBm. The proposed MPPT function can detect and determine the optimal rectifier stage for loading from 10 $\text{K}\Omega $ to 1 $\text{M}\Omega $ . The measured MPPT accuracy is over 87% from −22 to 4 dBm compared to external tuning conditions. The minimum stand-by power is 20 nW at 0.5 V and the overall MPPT power efficiency is over 72% with a peak value of 99.8% including dissipated power. Measurements also show the system can achieve self-startup and self-sustained functions with a 10- $\mu \text{F}$ external capacitor buffer.

Coordination Control of Microgrid using Sliding Mode Controller

Traditional power generation and consumption are undergoing major transformation. One of the tendencies is to integrate microgrid into the distribution network with high penetration of renewable energy resources. A synchronous generator and a PV farm supply power to the system’s AC and DC sides, respectively. A DC/DC boost converter with a maximum power point tracking (MPPT) function is implemented to maximize the energy generation from the PV farm. In the existing system a model predictive power and voltage control (MPPVC) method is developed for the AC/DC interlinking converter this has a drawback in smooth grid synchronization. But in the proposed system a sliding mode controller is used to link the AC bus with the DC bus while regulating the system voltage and frequency and it ensures smooth power transfer between the DC and AC sub grids. Meanwhile, smooth grid synchronization and connection can be achieved. Proposed constant frequency sliding mode control retains the advantages of good dynamic response as in hysteresis control, better reference tracking switching frequency and less sensitivity to parameter variations and non liner loads. From the Simulation results it is verified that the proposed topology is coordinated for power management in both AC and DC sides under critical loads with high efficiency, reliability, and robustness under both grid-connected and islanding modes.

Photovoltaic Module and Submodule Level Power Electronics and Control

The nine papers in this special section focus on photovoltaic module and sub-module level power electronics. Grid connected photovoltaic energy systems have experienced an explosive growth over the last decade, with a cumulative installed capacity surpassing the 400 GW milestone as of 2017. Among PV system configurations, distributed module-level converter architectures can lead to a higher energy yield by mitigating partial shading, persistent shading (soiling, snow, bird droppings, and fallen leaves), mismatch, and aging, through a higher maximum power point tracking (MPPT) efficiency. Also, distributed electronics might be the key for implementing diagnostic and prognostic actions at a module level. Among these configurations, microinverters (also known as ac-module inverter), which connect a single PV module to the grid, and PV power optimizers, which are dc–dc converters performing the MPPT function at a module level, have attracted the academic and industrial interest in the last decade. So much so, that both microinverters and dc–dc power optimizers are commercialized by tens of companies around the world, with a great variety of circuit topologies, which comprise combinations of one or more power stages, interleaved converters, resonant converters, topologies with and without isolation, etc.