Dynamic Maximum Power Point Tracking Research Articles

Behavioral modeling of grid-connected photovoltaic inverters: Development and assessment

This paper describes and assesses a behavioral model for grid-connected photovoltaic inverters. The model allows us to simulate the electrical behavior of commercial single-phase and three-phase inverters in accordance with the limits of EN50160 power quality. Regarding power strategies for current inverters, both voltage and current control loops have been explicitly modeled, providing suitable simulations of the injected AC-current waveform under either power dynamics or grid voltage disturbances. Additionally, irradiance oscillations and dynamic Maximum Power Point Tracking performance have been also considered in the proposed solution. Internal inverter variables are not needed to fit the model parameters, being estimated from basic data-sheet information provided by manufacturers and simple AC-collected values from the PV power plants. This characteristic avoids any additional DC-side measurement, being a significant contribution in comparison with previous approaches.The proposed model is assessed using real data collected in Spanish photovoltaic power plants along several years. The obtained results are compared with previous behavioral model approaches and also included in the paper.

The performance of perturb and observe and incremental conductance maximum power point tracking method under dynamic weather conditions

With the rapid growth of photovoltaic (PV) systems, stringent standards are envisaged to ensure the safe and efficient generation of power. Therefore, the performance of maximum power point tracking (MPPT) element in PV system under dynamic environmental conditions is very crucial. Hence, this paper evaluates the performance of perturb and observe (P&O) and incremental conductance (IC) MPPT technique on the basis of European Efficiency Test, EN 50530, which is specifically devised for the dynamic performance of PV system. Both techniques are implemented in direct control structure and buck–boost converter is used as MPPT converter. Experiments are conducted using a custom designed PV array simulator. Results reveal that both methods yield almost equivalent dynamic MPPT efficiency. However, in average, the performance of IC method is found to be slightly better that gives 98.5% efficiency compare to 98.3% in P&O. It is also seen that the performance of IC method is very sensitive to its perturbation size, especially at low insolation levels.

An improved dynamic maximum power point tracking method for PV application

Photovoltaic (PV) system has been regarded as one of the most popular renewable energy sources due to its easy installation and safe operation. As one of the key control algorithms, maximum power point tracking (MPPT) function of PV inverter has been researched widely. Usually, its performance has been evaluated under a fixed environmental condition including irradiance and temperature. However, recently the dynamic MPPT performance under varying irradiance conditions has been paid attention to the PV society. As the European standard EN 50530, which defines the recommended varying irradiance profiles, was released lately, the corresponding researches have been required to improve the dynamic MPPT performance. This paper presents the design and evaluation of the improved dynamic MPPT performance using the modified P&O MPPT method under EN 50530. By using 250kW PV inverter, the performance of the modified P&O method is evaluated and compared with the conventional P&O MPPT methods. The experimental results show that modified P&O method shows higher dynamic MPPT efficiency under EN 50530than the conventional P&O one.

Efficient Energy Harvesting With Electromagnetic Energy Transducers Using Active Low-Voltage Rectification and Maximum Power Point Tracking

This paper reports on efficient interfacing of typical vibration-driven electromagnetic transducers for micro energy harvesting. For this reason, an adaptive charge pump for dynamic maximum power point tracking is compared with a novel active full-wave rectifier design. For efficient ultra-low voltage rectification, the introduced active diode design uses a common-gate stage in conjunction with supply-independent biasing. While this active rectifier offers low voltage drops, low complexity and ultra-low power consumption, the adaptive charge pump allows dynamic maximum power point tracking with implicit voltage up-conversion. Hence, efficient energy harvesting with high-resistive transducers, e.g., electromagnetic generators, becomes possible even at buffer voltage levels far above actual transducer output voltages. Both interfaces are fully-integrated in a standard 0.35 μm twin-well CMOS process. The designs are optimized for sub-mW transducer power levels and wide supply voltage ranges. Thus, these presented transducer interfaces are particularly suitable for compact micro energy harvesting systems, such as wireless sensor nodes or medical implants. The active diode rectifier achieves efficiencies over 90% at a wide range of input voltage amplitudes of 0.48 V up to 3.3 V. The adaptive charge pump can harvest with a total efficiency of close to 50%, but very independent of the actual buffer voltage. This charge pump starts operating at a supply voltage of 0.8 V, and has an input voltage range of 0.5 V-2.5 V . Finally, results of harvesting from an actual electromagnetic generator prototype are presented.

Photovoltaic dynamic MPPT on a moving vehicle

In addition to the conversion efficiency of a photovoltaic panel, the maximum power point tracking (MPPT) method also plays a central role to harvest most energy out of sun. The MPPT unit on a moving vehicle must keep tracking accuracy high in order to compensate rapid change of insolation due to dynamic motion of the vehicle. In this paper, some problems of a PV system associated with a moving vehicle are addressed, and a modified quadratic maximization MPPT algorithm is proposed. Theoretical PV performance is linked to the experimental test followed by the Sandia dynamic test protocol to verify the proposed MPPT method. Finally, experimental result on a model ship is discussed.

An Integrated-Controlled AC/DC Interface for Microscale Wind Power Generation Systems

In this paper, a novel ac/dc interface with an integrated controller is proposed for the microscale wind power generation system (WPGS). The proposed interface is mainly composed of a dynamic maximum power point tracking (MPPT) control and a half-controlled single-stage rectifier with an integrated control. The half-controlled single-stage rectifier is proposed to replace the widely used two-stage converter for improving the current total harmonics distortion (THD) as well as the efficiency. The analytic expressions of the duty ratios for controlling the rectifier are also derived. Moreover, the dynamic response of the wind turbine and the extracted wind power are enhanced by the integrated dynamic MPPT control. Finally, from the experimental results, it can be seen that the current THD is reduced to around 5%, and the total efficiency is increased by about 12%-15% depending on the wind speed variations.

Comparison of direct maximum power point tracking algorithms using EN 50530 dynamic test procedure

Three direct maximum power point tracking (MPPT) algorithms with non-adaptive voltage step are evaluated in the light of their performance for photovoltaic systems under dynamic conditions for a resistive load. A microcontroller-based buck–boost DC–DC converter platform is used to implement and compare the algorithms. Dynamic test procedures from a new standard for inverter efficiency determination EN 50530 were implemented to evaluate dynamic MPPT algorithms’ efficiency and their dependence.Experimental results show that MPPT algorithms’ regulating frequency and regulating voltage step play a crucial role in the dynamic performance of direct algorithms. A range of regulating frequencies and voltage steps were examined. If proper parameter values are chosen, all algorithms perform well and close to each other. Detailed evaluation was performed with determining partial MPPT efficiency under different irradiance slopes. Results show that at least 10 Hz should be used to satisfy the 99% tracking efficiency over all slopes in the range from 0.5 to 100 W/m2/s as specified by EN 50530 standard. Further increase of regulating frequency would result in higher slope efficiency only at dynamic conditions.

On the testing, characterization, and evaluation of PV inverters and dynamic MPPT performance under real varying operating conditions

AbstractThe increasing number of photovoltaic inverters that are coming on to the PV market stresses the need to carry out a dynamic characterization of these elements and their maximum power point tracking (MPPT) algorithms under real operating conditions. In order to make these conditions repeatable at the laboratory, PV array simulators are used. However, actual simulators, including the commercial simulators, recreate only a single or small set of PV array characteristic curves in which quite commonly theoretical calculations are included in order to simulate irradiance and temperature artificial variations. This is far from being a recreation of the real and long dynamic behavior of a PV array or generator. The testing and evaluation of the performance of PV inverters and MPPT algorithms has to be carried out when the PV system moves dynamically according to real operating conditions, including processes such as rapidly changing atmospheric conditions, partial shadows, dawn, and nightfall. This paper tries to contribute to the analysis of this problem by means of an electronic system that both measures the real evolution of the characteristic curves of PV arrays at outdoor operation and then recreates them at the laboratory to test PV inverters. This way the equipment can highlight the different performances of PV inverters and MPPT techniques when they operate under real operating conditions. As an example, two commercial inverters are tested and analyzed under the recreated behavior of a PV generator during 2 singular days that include processes of partial shading and fast irradiance variations. Copyright © 2007 John Wiley & Sons, Ltd.

A novel maximum power fuzzy logic controller for photovoltaic solar energy systems

The maximum power tracking problem and efficient energy utilization of a stand-alone photovoltaic array (PVA) feeding voltage controlled linear and nonlinear loads is studied. A novel and simple on-line fuzzy logic-based dynamic search, detection and tracking controller is developed to ensure maximum power point (MPP) operation under excursions in solar insolation, ambient temperature and electric load variations. A computer simulation model of the PVA renewable utilization scheme including the effects of temperature and solar irradiation changes was developed and fully simulated. The load voltage is controlled by a DC chopper and kept constant at the required rated voltage. A permanent magnet DC motor (PMDC) driving a fan-type load was connected in parallel to an RL passive load. A speed control scheme is also used for the PMDC motor drive so that the drive can be operated at specified speeds. Different controllers have been employed in the unified PVA scheme to control three separate loads at MPP tracking condition namely voltage at load bus and speed of the PMDC motor. The main objective of the paper is to present a novel enhanced, cost-effective MPP detector (MPPD) and dynamic MPP tracking (MPPT) controller for a hybrid mix of electric loads.