Στην παρούσα διπλωματική εργασία προσομοιώθηκε μέσω του προγράμματος Simulink ένα φωτοβολταϊκό σύστημα το οποίο αποτελούνταν από ένα φωτοβολταϊκό πλαίσιο των 60W, έναν DC/DC μετατροπέα Buck-Boost και ένα φορτίο. Στη συνέχεια εφαρμόσθηκαν τέσσερις διαφορετικές μέθοδοι ελέγχου στο φωτοβολταϊκό σύστημα με στόχο να λειτουργεί στο σημείο απόδοσης μέγιστης ισχύος (MPP) και συγκρίναμε τα αποτελέσματα της κάθε μια μεθόδου. Οι μέθοδοι που εφαρμόσθηκαν ήταν η μέθοδος Ανοιχτού Κυκλώματος (Open Voltage Method), η μέθοδος Διαταραχής και Παρατήρησης (Perturb and Observe Method), η μέθοδος Διαφορικής Αγωγιμότητας (Incremental Conductance) και προτείναμε και μια βελτιωμένη μέθοδο Διαταραχής και Παρατήρησης (Improved Perturb and Observe Method). / In this diploma thesis a photovoltaic system was simulated with the program Simulink. The photovoltaic system consisted of a photovoltaic panel of 60W, a buck-boost DC/DC converter and a load. Then four different control methods where applied so that the photovoltaic system would operate at the maximum power point (MPP) and the results of each control method were compared. The control methods which were applied were the Open Voltage Method, the Perturb and Observe Method, the Incremental Conductance Method and we proposed an improved Perturb and Observe Method.

Recently, photovoltaic (PV) generation is becoming increasingly popular in industrial applications. As a renewable and alternative source of energy they feature superior characteristics such as being clean and silent along with less maintenance problems compared to other sources of the energy. In PV generation, employing a Maximum Power Point Tracking (MPPT) method is essential to obtain the maximum available solar energy. Among several proposed MPPT techniques, the Perturbation and Observation (P&O) and Model Predictive Control (MPC) methods are adopted in this work. The components of the MPPT control system which are P&O and MPC algorithms, PV module and high gain DC-DC boost converter are simulated in MATLAB Simulink. They are evaluated theoretically under rapidly and slowly changing of solar irradiation and temperature and their performance is shown by the simulation results, finally a comprehensive comparison is presented.

abstract: A single solar cell provides close to 0.5 V output at its maximum power point, which is very low for any electronic circuit to operate. To get rid of this problem, traditionally multiple solar cells are connected in series to get higher voltage. The disadvantage of this approach is the efficiency loss for partial shading or mismatch. Even as low as 6-7% of shading can result in more than 90% power loss. Therefore, Maximum Power Point Tracking (MPPT) at single solar cell level is the most efficient way to extract power from solar cell. Power Management IC (MPIC) used to extract power from single solar cell, needs to start at 0.3 V input. MPPT circuitry should be implemented with minimal power and area overhead. To start the PMIC at 0.3 V, a switch capacitor charge pump is utilized as an auxiliary start up circuit for generating a regulated 1.8 V auxiliary supply from 0.3 V input. The auxiliary supply powers up a MPPT converter followed by a regulated converter. At the start up both the converters operate at 100 kHz clock with 80% duty cycle and system output voltage starts rising. When the system output crosses 2.7 V, the auxiliary start up circuit is turned off and the supply voltage for both the converters is derived from the system output itself. In steady-state condition the system output is regulated to 3.0 V. A fully integrated analog MPPT technique is proposed to extract maximum power from the solar cell. This technique does not require Analog to Digital Converter (ADC) and Digital Signal Processor (DSP), thus reduces area and power overhead. The proposed MPPT techniques includes a switch capacitor based power sensor which senses current of boost converter without using any sense resistor. A complete system is designed which starts from 0.3 V solar cell voltage and provides regulated 3.0 V system output. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2015

This diploma thesis deals with the tracking of the maximum power point for photovoltaic panels and the methods used to achieve it. On this basis, two methods were designed and programmed and subsequently tested on three types of photovoltaic panels. In conclusion methods were appraised.

A module-level DC optimization proof of concept architecture is proposed to increase the efficiency of photovoltaic (PV) strings by minimizing the negative effects of shading caused by intermittent cloud cover while reducing cloud induced fast frequency fluctuations. The decentralized inverter approach combines the benefits of string and micro-inverter technology. This device can be affixed to pre-existing or new systems and operates in compliance with IEEE 1547 and California rule 21 standards by operating in maximum power point tracking (MPPT) or curtailment mode whenever necessary. The modular level device encapsulates three individual processes: an optimization engine to determine minimum power requirements, a fuzzy logic controller (FLC) to eliminate the effect of passing cloud cover, and a voltage regulation stage to monitor and appropriately adjust the output voltage of the device. Ramp rate reduction was accomplished using adaptive fuzzy logic control with a heuristic rule base inference engine. The modular design can be affixed to grid connected or islanded systems allowing for operation in regulated and variable load conditions. Matlab/Simulink 2019a was used to design and simulate the proof of concept model to verify the resiliency to partial shading, reduction of ramp rates during passing cloud coverage, and optimal output voltage for each panel while maintaining a constant DC link voltage of 120 V. This proof of concept has been successfully validated therefore further testing will be performed for various irradiance conditions.

Solar power is becoming ever more popular in a variety of applications. It is particularly attractive because of its abundance, renewability, and environment friendliness. Solar powered spacecraft systems have ever-expanding loads with stringent power regulation specifications. Moreover, they require a light and compact design of their power system. These constraints make the optimization of power harvest from solar arrays a critical task. Florida Power Electronics Center (FPEC) at UCF set to develop a modular fault-tolerant power system architecture for space applications. This architecture provides a number of very attractive features including Maximum Power Point Tracking (MPPT) and uniform power stress distribution across the system. MPPT is a control technique that leads the system to operate its solar sources at the point where they provide maximum power. This point constantly moves following changes in ambient operating conditions. A digital controller is setup to locate it in real time while optimizing other operating parameters. This control scheme can increase the energy yield of the system by up to 45%, and thus significantly reduces the size and weight of the designed system. The modularity of the system makes it easy to prototype and expand. It boosts its reliability and allows on-line reconfiguration and maintenance, thus reducing down-time upon faults. This thesis targets the analysis and optimization of this architecture. A new modeling technique is introduced for MPPT in practical environments, and a novel digital power stress distribution scheme is proposed in order to properly distribute peak and thermal stress and improve reliability. A 2kW four-channel prototype of the system was built and tested. Experimental results confirm the theoretical improvements, and promise great success in the field.

No description available.

The proposed energy harvesting circuit system is designed for indoor solar environment especially for factories where the light energy is abundant and stable. The designed circuits are intended to power wireless sensor nodes (WSNs) or other computing unit such as microcontrollers or DSPs to provide a power solution for Internet of Things (IoTs). The proposed circuit can extract maximum power from the PV panel by utilizing the maximum power point tracking (MPPT) technique. The power stage is a synchronous dual-input dual-output non-inverting buck-boost converter operating in discontinuous conduction mode (DCM) and constant on-time pulse skipping modulation (COT-PSM) to achieve voltage regulation and maximum power delivery to the load. Battery is used as secondary input also as secondary output to achieve a longer lifecycle, a fast load response time and support higher load conditions. The proposed MPPT technique doesn't require any current sensor or computing units. Fully digitalized simple circuits are used to achieve sampling, store, and comparing tasks to save power. The whole circuits including power stage and control circuits are designed and will fabricate in TSMC BCDMOS 180 nm process. The circuits are verified through schematic level simulations and post-layout simulations. The results are validated to prove the proposed circuit and control scheme work in a manner. / Master of Science / With the growing energy demands, the efficient energy conversion systems caught great attentions. Especially, in the era of Internet of Things, powering those wireless devices can be extremely difficult. Nowadays, lots of devices such as consumer electronics, wireless sensor nodes, computing and mission system etc. are still powered by the batteries. Regular changing the batteries of those devices can be inconvenient or expensive. Energy harvesting provides a good solution to this issue because there are lots of ambient energy source is available. To design an energy efficient energy harvesting circuit system can help extend the device lifecycle per charging cycle. Even with some specific energy source which power scale is high enough, meanwhile the load doesn’t require too much power, the devices can be power-independent or standalone. In this work, the proposed circuit targets for indoor solar energy harvesting via solar panel. The target powering devices are wireless sensor nodes (WSNs). Meanwhile, WSNs can monitor the temperature, humidity, pressure, noise level etc. The proposed circuit design combines the power stage and control circuit on an integrated chip (IC), only few components are off-chip. It provides a very compact, endurable, and economical solution to the current IoT powering issue.

This dissertation aims to present detailed analysis of the small scale wind energy conversion system (WECS) design and implementation. The dissertation will focus on implementing a hardware prototype to be used for testing different control strategies applied to small scale WECSs. Novel control algorithms will be proposed to the WECS and will be verified experimentally in details. The wind turbine aerodynamics are presented and mathematical modeling is derived which is used then to build wind simulator using motor generator (MG) set. The motor is torque controlled based on the turbine mathematical model and the generator is controlled using the power electronic conversion circuits. The power converter consists of a three phase diode bridge followed by a boost converter. The small signal modeling for the motor, generator, and power converter are presented in details to help building the needed controllers. The main objectives of the small scale WECS controller are discussed. This dissertation focuses on two main regions of wind turbine operation: the maximum power point tracking (MPPT) region operation and the stall region operation. In this dissertation, the concept of MPPT is investigated, and a review of the most common MPPT algorithms is presented. The advantages and disadvantaged of each method will be clearly outlined. The practical implementation limitation will be also considered. Then, a MPPT algorithm for small scale wind energy conversion systems will be proposed to solve the common drawback of the conventional methods. The proposed algorithm uses the dc current as the perturbing variable and the dc link voltage is considered as a degree of freedom that will be utilized to enhance the performance of the proposed algorithm. The algorithm detects sudden wind speed changes indirectly through the dc link voltage slope. The voltage slope is also used to enhance the tracking speed of the algorithm and to prevent the generator from stalling under rapid wind speed slow down conditions. The proposed method uses two modes of operation: A perturb and observe (PandO) mode with adaptive step size under slow wind speed fluctuation conditions, and a prediction mode employed under fast wind speed change conditions. The dc link capacitor voltage slope reflects the acceleration information of the generator which is then used to predict the next step size and direction of the current command. The proposed algorithm shows enhanced stability and fast tracking capability under both high and low rate of change wind speed conditions and is verified using a 1.5-kW prototype hardware setup. This dissertation deals also with the WECS control design under over power and over speed conditions. The main job of the controller is to maintain MPPT while the wind speed is below rated value and to limit the electrical power and mechanical speed to be within the system ratings when the wind speed is above the rated value. The concept of stall region and stall control is introduced and a stability analysis for the overall system is derived and presented. Various stall region control techniques are investigated and a new stall controller is proposed and implemented. Two main stall control strategies are discussed in details and implemented: the constant power stall control and the constant speed stall control. The WECS is expected to work optimally under different wind speed conditions. The system should be designed to handle both MPPT control and stall region control at the same time. Thus, the control transition between the two modes of operation is of vital interest. In this dissertation, the light will be shed on the control transition optimization and stabilization between different operating modes. All controllers under different wind speed conditions and the transition controller are designed to be blind to the system parameters pre knowledge and all are mechanical sensorless, which highlight the advantage and cost effectiveness of the proposed control strategy. The proposed control method is experimentally validated using the WECS prototype developed. Finally, the proposed control strategies in different regions of operation will be successfully applied to a battery charger application, where the constraints of the wind energy battery charger control system will be analyzed and a stable and robust control law will be proposed to deal with different operating scenarios. / Ph. D.

The proposed vibration energy harvesting IC harvests energy from a piezoelectric transducer (PZT) to provide power for a wireless sensor node (WSN). With a traditional rectification stage, a two-path three-switch dual-input dual-output architecture is adopted to extract power and regulate the output voltage for the load with one stage. The power stage is controlled with a new maximum power point tracking (MPPT) algorithm, which integrates both fraction open circuit voltage (FOCV) and perturb and observe (PandO). The proposed algorithm was able to extract maximum power from a transducer due to high accuracy on the maxim power point (MPP) and low power dissipation. The proposed circuit is implemented in TSMC 180 nm BCD technology and the post-layout simulation verifies the functionality of the proposed design. The simulation results show that the circuit operates under the maximum power point to extract maximum power from a PZT. / Master of Science / The battery life has always been problematic ever since electronic devices exist. As semiconductor technology advances, more transistors could fit in the same area. Resultantly, portable, and mobile devices become more powerful but usually dissipate more power. Unfortunately, the development of the batteries has not been improved significantly. So, it is necessary to charge portable and mobile devices often or replace batteries frequently. In some applications where a device is hard to reach once installed, charging or replacing the battery is difficult. Under these circumstances, energy harvesting from ambient sources is an effective alternative. There are many types of sources of energy widely available in the environment such as vibration, thermal, solar, RF and etc. Solar energy harvesting is the most popular owing to high power density. However, sunlight is unavailable during night time. Vibration energy, although the power density is lower compared with solar, is a viable solution when solar is not a good source of energy. The proposed work utilizes abundant vibration energy at factories to power wireless sensor nodes (WSNs), which can monitor the temperature, light intensity, pressure, etc.