Maximum Power Point Tracking Circuit Research Articles

Effect of DC-DC voltage step-up converter impedance on thermoelectric energy harvester system design strategy

Conventional thermoelectric energy harvester design strategies often focus on improving the material property thermoelectric figure of merit (ZT); however, enhanced performance through improved materials cannot be achieved without optimized integration of subcomponents. The low voltage output from a thermoelectric module makes it challenging to design a practically usable wearable energy harvester. In addition to consideration of effective heat dissipation along with matching module geometry, a voltage needs to be boosted at a usable voltage value to utilize produced power. Using a DC to DC voltage step-up converter adds additional design complexity as the power cannot be harnessed at maximum power point of thermoelectric module due to input impedance requirement of the power conditioning circuit. Moreover, additional power loss occurs due to inherent voltage conversion inefficiency, which also depends on the harvesting voltage value. A recent design framework on wearable thermoelectric energy harvester assumed that a Maximum Power Point Tracking (MPPT) boost converter can be utilized for thermoelectric energy harvester systems, however it is unable to accurately determine the maximum power point during operation because of the transient nature of thermoelectric systems. Additionally, an MPPT circuit consumes power and adds complexity to the system design, which may not economically justify the use of such a circuit. This work proposes an encompassing thermoelectric system design framework for small scale energy harvesting using only state-of-the-art commercial products. Particularly, thermoelectric module geometry design is examined with the incorporation of a DC to DC voltage step-up converter without the use of MPPT. The framework can provide guidance for further development of subcomponents and materials, as well as system integration. An operational wearable energy harvester system was built using off-the-shelf components and demonstrated a usable power output which provides experimental evidence for the proposed design strategy.

Photovoltaic Energy Harvester With Fractional Open-Circuit Voltage Based Maximum Power Point Tracking Circuit

A photovoltaic (PV) energy harvester is proposed, and it adopts the fractional open-circuit voltage method to track the maximal power point of PV cells. The proposed harvester was designed and fabricated by using a 0.18- ${\mu }\text{m}$ 1P6M mixed-signal process. The input voltage of the proposed harvester may range from 0.5 to 1.1 V, and its measured peak total efficiency is 93.4%. The proposed harvester is suitable for Internet-of-Things applications, and the maximal duty cycle it can afford for a device with a 5-mA load and 20-ms activation time is 50%.

A Behavioral Model for Solar Cells With Transient Irradiation and Temperature Assessment

The time to market of maximum power point tracking circuits for solar cells depends on the time of transient simulations. But, the traditional tools use a nonlinear resistor model for the solar cells. The question is if it is possible to use another nonlinear relationship to improve the convergence features. This paper presents a new method for modeling a solar cell, considering temperature and irradiation changes and an improved convergence performance. In this model, the solar cell's current-voltage (I-V) characteristics for three irradiation and two temperature conditions are required, showing a feasible procedure. The proposed model is fitted to three commercial solar cells exhibiting a maximum average error of 2.51 percent. It is tested in a transient analysis converging to the expected values in a maximum power point tracking circuit.

A Sub-10 mV Power Converter With Fully Integrated Self-Start, MPPT, and ZCS Control for Thermoelectric Energy Harvesting

An inductive power converter for thermoelectric generator (TEG) is presented in this paper. A novel redundant inverter ring oscillator is proposed to self-oscillate in a very low supply voltage down to 45 mV. An additional self-start assist circuit with a differential clock booster and an exponential charge pump is implemented in the power converter to achieve lower self-start voltage. Boundary continuous-conduction mode, zero current switch (ZCS), and maximum power point tracking (MPPT) features have been incorporated into the power converter. Selective turn-ON dynamical-comparators have been used in ZCS and MPPT circuits to save power and achieve minimum operating supply voltage. Fabricated in 65-nm CMOS process, the chip can self-start at 210 mV. After self-start, only 7-mV input voltage is needed to sustain the power converter operation. With a TEG open circuit voltage of 80 mV and internal resistance of $5~\Omega $ , the chip can provide a maximum output power of $229~\mu \text{W}$ with end-to-end efficiency of 71.5%.

A New Robust Analog Maximum Power Point Tracker for a PV Battery Charger

Maximum power point tracking (MPPT) is an inevitable part of new controller design for PV connected voltage converters used to extract energy. To simplify the implementation of the algorithm, in this paper, an analog circuit for MPPT of a PV battery charger is proposed which works in a full range condition with constant switching frequency. Besides this, a new robust controller parameter is introduced. As discussed in the paper, conventional MPPT algorithms provide PV current or voltage reference value as output controller parameter, which fast climate changes may cause system instability. Here, a new variable is defined to eliminate the problem and improve the stability of the system. To compare the presented circuit with a conventional system, perturb and observe MPPT algorithm which is well-known in PV systems is implemented on the same system. The proposed system is also compared with a recently developed current-mode system. Simulation results for both simulations are presented and compared which demonstrate performance and effectiveness of the proposed analog MPPT circuit.

A novel MPPT circuit with 99.1% tracking accuracy for energy harvesting

A novel maximum power point tracking (MPPT) circuit based on Buck–Boost converter is presented for micro-power energy harvesting, which efficiently improves the power efficiency and robustness of system. The proposed MPPT uses the low-power analog multiplier and multi-outputs self-powered common-gate comparator to track the input power, and simplifies data calculation and structure greatly. The fast dynamic switching circuit and digital control circuit are introduced to enhance the adaptability and flexibility of system. The performance of whole converter was validated by the simulation results in a 65-nm CMOS process. The minimum starting voltage is 0.15 V. The peak output power is 40.5 µW, with a power loss of 14.1 µW. The peak power efficiency and peak tracking efficiency are 92.1 and 99.1%, respectively. The proposed MPPT has the advantages such as low power, high efficiency, fast tracking speed, simple structure.

Maximum Power Point Tracking Control of a Thermoelectric Generation System Using the Extremum Seeking Control Method

This study proposes and implements maximum power Point Tracking (MPPT) control on thermoelectric generation system using an extremum seeking control (ESC) algorithm. The MPPT is applied to guarantee maximum power extraction from the TEG system. The work has been carried out through modelling of thermoelectric generator/dc-dc converter system using Matlab/Simulink. The effectiveness of ESC technique has been assessed by comparing the results with those of the Perturb and Observe (P&O) MPPT method under the same operating conditions. Results indicate that ESC MPPT method extracts more power than the P&O technique, where the output power of ESC technique is higher than that of P&O by 0.47 W or 6.1% at a hot side temperature of 200 °C. It is also noted that the ESC MPPT based model is almost fourfold faster than the P&O method. This is attributed to smaller MPPT circuit of ESC compared to that of P&O, hence we conclude that the ESC MPPT method outperforms the P&O technique.

Energy management strategy to simplify the hardware structure of wireless sensor nodes

Maximum power point tracking (MPPT) circuits in photovoltaic (PV) cell-based wireless sensor nodes often make the systems complex and costly. This paper proposes a novel energy management strategy for PV cell-based systems to remove their MPPT circuit without reducing their working efficiency. By modeling the non-MPPT system, energy storage in different situations is calculated. The key factors to improve the working efficiency of the system, such as operating voltage and number of PV cells in series, are also analyzed. A design is proposed to maximize the working efficiency. Another model for systems including MPPT circuits is also proposed for comparison. Simulation analysis shows that during the monitoring period, the total active time of the non-MPPT system can be as long as that of the system with MPPT circuits. Experimental tests confirm the validity of the proposed energy strategy. More importantly, the number of electronic components in the non-MPPT system’s power module is only approximately 1/5 of that of the other system. This strategy provides a possible approach for practical wireless sensor nodes that are small in size and have low cost.

A MPPT Circuit With 25 $\mu\text{W}$ Power Consumption and 99.7% Tracking Efficiency for PV Systems

A Maximum Power Point Tracking (MPPT) circuit for a 0.7-W photovoltaic (PV) system is proposed. The circuit employs a modified hill-climbing algorithm based on a 3-points comparison instead of the traditional 2-points comparison. The adopted algorithm simplifies the detection of the Maximum Power Point (MPP) and enables the implementation of a periodic sleep-mode to reduce the overall power consumption without compromising effective tracking of irradiance variations. Moreover, to achieve high MPP tracking efficiency, a low-power linear analog multiplier is implemented to accurately compute the instantaneous power of the PV source from its sensed voltage and current levels. This power-metering function is realized in the analog domain to eliminate the need for data converters and to minimize the MPPT circuit's power consumption. A complete design of the proposed circuit is implemented in 0.18-μm BiCMOS process in less than 1.55 mm 2 and consumes less than 25 μW with the digital core running at 500 kHz and a measured peak MPP tracking efficiency of 99.7%.

Fully-Integrated High-Conversion-Ratio Dual-Output Voltage Boost Converter With MPPT for Low-Voltage Energy Harvesting

This paper proposes a fully-integrated high-conversion-ratio dual-output voltage boost converter (VBC) with maximum power point tracking (MPPT) circuits for low-voltage energy harvesting. The VBC consists of two voltage generators that generate $V_{\mathrm { OUT1}}$ and $V_{\mathrm { OUT2}}$ . $V_{\mathrm { OUT1}}$ and $V_{\mathrm { OUT2}}$ are three and nine times higher than the harvester’s output $V_{\mathrm { IN}}$ , respectively. $V_{\mathrm { OUT1}}$ is used as a supply voltage for on-chip application circuits while $V_{\mathrm { OUT2}}$ is used as the charging voltage for a Li-ion secondary battery. The VBC achieves a high voltage conversion ratio (max. $\times \,\,9$ ) and a high power conversion efficiency. The MPPT circuits control the operating frequencies of the CPs to extract maximum power at each output. The measurement results demonstrated that the circuit converted a 0.59 V input to a 1.41 V output with 75.8% efficiency when the output powers of $V_{\mathrm { OUT1}}$ and $V_{\mathrm { OUT2}}$ were 396 and $0~\mu \text {W}$ , respectively, and a 0.62 V input to a 4.54 V output with 49.1% efficiency when the output powers were 0 and $114~\mu \text {W}$ , respectively.

A current-based simple analog MPPT circuit for PV systems

A new single pilot-sensor maximum power point tracking (MPPT) system, consisting of a buck type DC/DC converter, was developed. It is controlled by an analog-based unit. The main difference between the proposed MPPT system and other systems is that the short circuit current of the pilot-PV module in our system is used to control the DC/DC converter. The circuit of the proposed system does not utilize an expensive digital signal processor nor a microcontroller; hence, the cost and the complexity of the system are reduced.

Microwatt power consumption maximum power point tracking circuit using an analogue differentiator for piezoelectric energy harvesting

A maximum power point tracking (MPPT) scheme by tracking the open-circuit voltage from a piezoelectric energy harvester using a differentiator is presented in this paper. The MPPT controller is implemented by using a low-power analogue differentiator and comparators without the need of a sensing circuitry and a power hungry controller. This proposed MPPT circuit is used to control a buck converter which serves as a power management module in conjunction with a full-wave bridge diode rectifier. Performance of this MPPT control scheme is verified by using the prototyped circuit to track the maximum power point of a macro-fiber composite (MFC) as the piezoelectric energy harvester. The MFC was bonded on a composite material and the whole specimen was subjected to various strain levels at frequency from 10 to 100 Hz. Experimental results showed that the implemented full analogue MPPT controller has a tracking efficiency between 81% and 98.66% independent of the load, and consumes an average power of 3.187 μW at 3 V during operation.

Capacitor charging method for I–V curve tracer and MPPT in photovoltaic systems

The capacitor charging method can be used in Photovoltaic (PV) systems for two typical applications: a very simple and cheap way (1) to trace the I–V curve of a PV generator of whatever size and (2) to track the Maximum Power Point (MPP), especially when the partial shading occurs. The problem is the correct sizing of the capacitor in order to achieve accurate, uniform and smooth results. In the first application a simplified calculation to design quickly the capacitor is carried out. This is done only as a function of the main characteristics of the PV array and the most important datasheet parameters of the PV modules. Then, the setup of I–V curve tracers at module, string and array levels is presented: these tracers are useful in the detection of underperformance of PV systems. In the second application a MPPT (MPP Tracker) circuit based on capacitor charging is designed and simulated in partial shading conditions. In these conditions the Power–Voltage (P–V) curve of a PV array is characterized by the presence of multiple maxima for the bypass diode action. The PV array is isolated from the load for a negligibly short period and is connected to an external capacitor. During the charging time, the proposed circuit tracks the global MPP. This circuit is easy to implement and shortens the duration needed for scanning the P–V curve of the array.

최대전력점추적방법과 외부저항 제어 알고리즘을 이용한 미생물연료 전지의 전력생산 최대화

A microbial fuel cell (MFC) and bioelectrochemical systems are novel bioprocesses which employ exoelectrogenic biofilm on electrode as a biocatalyst for electricity generation and various useful chemical production. Previous reports show that electrogenic biofilms of MFCs are time varying systems and dynamically interactive with the electrically conductive media (carbon paper as terminal electron acceptor). It has been reported that maximum power point tracking (MPPT) method can automatically control load by algorithm so that increase power generation and columbic efficiency. In this study, we developed logic based control strategy for external load resistance by using <TEX>$LabVIEW^{TM}$</TEX> which increases the power production with using flat-plate MFCs and MPPT circuit board. The flat-plate MFCs inoculated with anaerobic digester sludge were stabilized with fixed external resistance from <TEX>$1000{\Omega}$</TEX> to <TEX>$100{\Omega}$</TEX>. Automatic load control with MPPT started load from <TEX>$52{\Omega}$</TEX> during 120 hours of operation. MPPT control strategy increased approximately 2.7 times of power production and power density (1.95 mW and <TEX>$13.02mW/m^3$</TEX>) compared to the initial values before application of MPPT (0.72 mW and <TEX>$4.79mW/m^3$</TEX>).

Voltage control of stand-alone wind and solar energy system

In this paper wind and solar based stand-alone hybrid energy system is presented for the remote area power system applications. The wind, solar, battery, fuel cell and dump load (i.e., aqua-electrolyzer) are connected to the common dc bus. An ac load is connected to dc bus through a pulse width modulation (PWM) based inverter. Ac voltage at load bus can be maintained at rated value by regulating dc-link voltage (Vdc) at its reference value and by controlling modulation index of PWM inverter. Novel control algorithms are developed to maintain Vdc at its reference voltage irrespective of variations in wind speed, solar irradiance and load. Along with the regulation of Vdc, dc–dc converter (connected between battery and dc-link) acts as a maximum power point tracker (MPPT) for photovoltaic (PV) array. Hence an extra dedicated MPPT circuit is not required to extract maximum power from PV. Control technique for the PWM inverter has been developed to make the line voltages balanced at the point of common coupling (PCC) when the load is unbalanced. Hence, efforts are made to supply quality voltage to the consumers through the stand-alone power system. Detailed modeling of various components of stand-alone system is presented. Extensive simulation results using Matlab/SIMULINK established that the performance of the controllers is quite satisfactory under balanced as well as unbalanced load conditions. Moreover, results with real time digital simulator (RTDS) are presented.

A Single Stage Photovoltaic Inverter With Common Power Factor Control and Maximum Power Point Tracking Circuit

This paper presents a unique approach towards the reduction of steps employed in conversion of power produced by a photovoltaic energy system. When a Photovoltaic system feeds an ac load, the power conditioning system of a Photovoltaic energy conversion system consists of a boost converter at the first stage to boost up the direct current (dc) supply, and an inverter to convert this boosted supply to alternating current (ac) at the second stage. But in this conventional system, losses happen at both the stage which makes the whole system to have low efficiency. The proposed approach in this paper has only one stage conversion. In this single step conversion the direct current supply is boosted and converted to alternating current with the help of a single inverter circuit. This process of power conditioning is carried out with respect to the load connected as well to the maximum power with respect to the variant irradiation and temperature condition. The load connected to the system is tested under varying environmental conditions of the photovoltaic system. Nature of output power from the system is studied by varying the irradiation and temperature of the photovoltaic array.

A Low-Power Photovoltaic Maximum Power Point Tracking Circuit for WSNs

Currently, most wireless sensor networks (WSNs) are powered by batteries. When energy stored in batteries is exhausted, the life of the WSNs goes to the end. The concept of energy harvesting provides a practical solution to the problem of the energy limitation. In this article, the feasibility and performance of a simple and low-cost analog solar energy harvesting circuit with the function of maximum power point tracking (MPPT) are investigated. The technique provided is based on the approximately linear relationship between the maximum power point (MPP) voltage and the open-circuit voltage of a solar panel under different irradiation levels. Several experiments have been carried out regarding the accuracy and efficiency of MPPT as well as the working process of the circuit. Results show that the maximum power point with different loads can be effectively tracked by the self-powered MPPT circuit, and in the meantime, a stable output voltage can be generated. The efficiency of energy conversion is guaranteed by a commercial off-the-shelf DC-DC chip. The detailed description of the circuit design and the comprehensive analysis of the circuit performance will provide a useful guide for the future applications.

An Energy-Efficient Fast Maximum Power Point Tracking Circuit in an 800-μW Photovoltaic Energy Harvester

An energy-efficient maximum power point tracking (MPPT) circuit with a fast-tracking time for use with 800-μW PV energy harvesters is presented in this paper. The proposed MPPT circuit uses a successive approximation register MPPT algorithm, which has a power down mode and a fast tracking time, to achieve low power consumption and energy savings. The prototype MPPT circuit, which consists of analog-based circuits, has been implemented and fabricated in a 0.35-μm BCDiMOS process. The MPPT core occupies an area of 3 mm2 and consumes 4.6 μW of power. The tracking time is reduced by 69.4% and the stored energy is increased by 31.4% as compared to the conventional hill climbing-based MPPT algorithm under indoor conditions.

A 1-mW Solar-Energy-Harvesting Circuit Using an Adaptive MPPT With a SAR and a Counter

This brief presents an energy-harvesting system that uses an adaptive maximum power point tracking (MPPT) circuit for 1-mW solar-powered wireless sensor networks. The proposed MPPT circuit exploits a successive approximation register and a counter to solve the tradeoff problem between a fast transient response and a small steady-state oscillation with low-power consumption. The proposed energy-harvesting circuit is fabricated using a 0.35-μm CMOS process. The MPPT circuit reduces the transient response time by 76.6%, dissipates only 110 μW , and shows MPPT efficiency of 99.6%.

Design and Implementation of a MPPT circuit for a Solar UAV

This paper presents a maximum power point tracking (MPPT) circuit for an Unmanned Air Vehicle. The design of the MPPT is proposed utilizing a boost-converter topology. The power of the photovoltaic cells is monitored by a closed-loop microcontroller based control system, and the PWM signal of the boost converter continuously adjusted to extract maximum power. The MPPT is used to charge the Lithium-ion Polymer battery and feed the electrical load of the unmanned aircraft.