Maximum Power Transfer Tracking Research Articles

Load Effect Analysis and Maximum Power Transfer Tracking of CPT System

Owing to the flexibility of coupling structure, low standing losses and low Electromagnetic Interference (EMI), capacitive power transfer (CPT) has drawn much attention as one of the new wireless power transfer (WPT) technologies. However, to date, the load effect on the system performance has not been analyzed comprehensively, and the CPT system is usually fully tuned (tank network resonant frequency fully tuned to the fundamental components of the nominal switching frequency), which is challenging to maintain practically. Based on these considerations, this paper first provides a detailed analysis of how the load can affect the performance of a CPT system. An optimal load resistance is shown to exist for a CPT system with a non-fully/partially tuned LCC tank (tank network resonant frequency is designed to be lower than the fundamental components of the switching frequency). By dynamically transforming the load to its optimal value, the system can transfer maximum power to the load while maintaining zero voltage switching (ZVS) operation. Then, a controlled buck-boost converter based on perturbation and observation algorithm is introduced to the system to obtain the optimal equivalent resistance against the actual load variations via tracking the maximum power transfer point. The final prototype has demonstrated that a maximum power of 10 W is obtained, with an end-to-end power efficiency of about 70% over a wide range of load variations from $5~\Omega $ to 1 $\text{k}\Omega $ .

Impedance-Matching Range Extension Method for Maximum Power Transfer Tracking in IPT System

Maximum power transfer is an important index for an inductive power transfer (IPT) system to make full use of its power transfer capability, and such a capability is usually realized by impedance matching. Traditionally, impedance matching is implemented by placing a power electronics converter such as a dc–dc converter at the secondary side of an IPT system. However, the power electronics converter and its operation mode directly affect its impedance-matching range, which is very limited if a traditional power converter only operates at continuous conduction mode (CCM). To extend the impedance-matching range, this paper proposes a novel impedance matching method based on combined CCM and discontinuous conduction mode (DCM) operation of an impedance matching converter. The impedance-matching range is fully analyzed for CCM and DCM operation, respectively, by taking variation of coupling coefficient into consideration. The analysis results show that the impedance-matching range can be extended by more than double that of the traditional impedance matching method. In addition, a maximum power transfer tracking method is developed using the proposed impedance-matching range extension method, and the experimental results have verified the feasibility of the tracking method.

A Maximum Power Transfer Tracking Method for WPT Systems with Coupling Coefficient Identification Considering Two-Value Problem

Maximum power transfer tracking (MPTT) is meant to track the maximum power point during the system operation of wireless power transfer (WPT) systems. Traditionally, MPTT is achieved by impedance matching at the secondary side when the load resistance is varied. However, due to a loosely coupling characteristic, the variation of coupling coefficient will certainly affect the performance of impedance matching, therefore MPTT will fail accordingly. This paper presents an identification method of coupling coefficient for MPTT in WPT systems. Especially, the two-value issue during the identification is considered. The identification approach is easy to implement because it does not require additional circuit. Furthermore, MPTT is easy to realize because only two easily measured DC parameters are needed. The detailed identification procedure corresponding to the two-value issue and the maximum power transfer tracking process are presented, and both the simulation analysis and experimental results verified the identification method and MPTT.

Small scale wind energy harvesting with maximum power tracking

It is well-known that energy harvesting from wind can be used to power remote monitoring systems. There are several studies that use wind energy in small-scale systems, mainly with wind turbine vertical axis. However, there are very few studies with actual implementations of small wind turbines. This paper compares the performance of horizontal and vertical axis wind turbines for energy harvesting on wireless sensor network applications. The problem with the use of wind energy is that most of the time the wind speed is very low, especially at urban areas. Therefore, this work includes a study on the wind speed distribution in an urban environment and proposes a controller to maximize the energy transfer to the storage systems. The generated power is evaluated by simulation and experimentally for different load and wind conditions. The results demonstrate the increase in efficiency of wind generators that use maximum power transfer tracking, even at low wind speeds.

Maximum Power Transfer Tracking for Ultralow-Power Electromagnetic Energy Harvesters

This paper describes the design and operation of power conditioning system with maximum power transfer tracking (MPTT) for low-power electromagnetic energy harvesters. The system is fully autonomous, starts up from zero stored energy, and actively rectifies and boosts the harvester voltage. The power conditioning system is able to operate the harvester at the maximum power point against varying excitation and load conditions, resulting in significantly increased power generation when the load current waveform has a high peak-to-mean ratio. First, the paper sets out the argument for MPTT, alongside the discussion on the dynamic effects of varying electrical damping on the mechanical structure. With sources featuring stored energy, such as a resonant harvester, maximum power point control can become unstable in certain conditions, and thus, a method to determine the maximum rate of change of electrical damping is presented. The complete power conditioning circuit is tested with an electromagnetic energy harvester that generates 600 mV rms ac output at 870 μW under optimum load conditions, at 3.75 m·s-2 excitation. The digital MPTT control circuit is shown to successfully track the optimum operating conditions, responding to changes in both excitation and the load conditions. At 2 V dc output, the total current consumption of the combined ancillary and control circuits is just 22 μA. The power conditioning system is capable of transferring up to 70% of the potentially extractable power to the energy storage.

Design and Performance Analysis of Supercapacitor Charging Circuits for Wireless Sensor Nodes

Micro-solar energy harvesting systems have achieved efficient operations through maximum power point tracking (MPPT) and maximum power transfer tracking (MPTT) techniques. However, they may have chargers with relatively high power thresholds, below which they have 0% efficiency. As a result, these harvesters either require much larger panels than necessary, or they fail to sustain extended periods of poor weather. To address this problem, we propose to generalize MPTT to MCZT, for Maximum Charging Zone Tracking, to expand the zones of effective charging. To cover the wide dynamic range of solar irradiation, we propose a programmable charge pump driven by a direct digital synthesizer (DDS). In addition, we dynamically reconfigure the topology of multiple supercapacitors to maximize charging efficiency and minimize voltage-dependent leakage. Experimental results from simulation and measurement show that under the high solar irradiance of 1000 W/m2, our MPTT part achieves 40%-50% faster charging time than one without MPTT; and under low solar irradiation of 300 W/m2, the boost-up operation of our system enables fully charging the supercapacitors, thereby extending the harvesting time zone from 10:00 am-07:10 pm to 8:20 am-8:00 pm even on a sunny day, all with an MPTT overhead of 1.5 mW.

Research and development of maximum power transfer tracking system for solar cell unit by matching impedance

Employing the theorem that matching impedance produces maximum power transfer, the current study develops a low-cost and highly efficient “maximum power point tracker for a solar cell unit,” for the purpose of allowing a solar cell to achieve optimal power transfer under different solar intensities and temperatures. Circuit control takes a single-chip microprocessor as the core and the booster circuit design undergoes the solar cell charging operation even though the solar cell output voltage is lower than the rated storage battery voltage. Experiments conducted in this study prove that the tracker this study develops effectively enhances the utilization efficiency of a solar cell. When a solar cell is at an output voltage above 30% of the rated voltage, it can charge a storage battery. When it reaches above 80% of the rated voltage, its power conversion efficiency can reach above 85%. The charge and discharge management mechanism of the device also avoids excessive charge and discharge of the storage battery, and extends storage battery longevity.