Published by Shanmugavadivu Natarajan, Department of Electrical and Electronics Engineering, Sri Venkateswara College of Engineering, Sriperumbudur, 602117, India
Abstract. This study introduces a novel transformerless high voltage gain DC-DC converter for solar power. It combines a two-inductor boost converter, voltage multiplier, and switched capacitor cells, achieving a remarkable high voltage gain with 98.24% efficiency. A 200 W prototype was tested, confirming a peak efficiency of 96.2% in real-world conditions. It also maintains 97% efficiency in motor load systems, reducing energy consumption and maintenance costs. This innovative converter enhances solar energy harvesting and has versatile power conversion potential, marking a significant advancement in renewable energy tech.
Streszczenie. W tym badaniu przedstawiono nowatorską, beztransformatorową przetwornicę DC-DC o wysokim wzmocnieniu napięcia do zasilania energią słoneczną. Łączy w sobie dwuindukcyjny konwerter podwyższający napięcie, powielacz napięcia i przełączane ogniwa kondensatorów, osiągając niezwykłe wysokie wzmocnienie napięcia przy sprawności 98,24%. Przetestowano prototyp o mocy 200 W, który potwierdził szczytową wydajność na poziomie 96,2% w rzeczywistych warunkach. Utrzymuje także sprawność na poziomie 97% w układach obciążenia silnika, redukując zużycie energii i koszty konserwacji. Ten innowacyjny konwerter usprawnia pozyskiwanie energii słonecznej i ma wszechstronny potencjał konwersji mocy, co stanowi znaczący postęp w technologii energii odnawialnej. (Wydajny, uproszczony konwerter DC-DC o wzmocnieniu wysokiego napięcia, zapewniający lepsze pozyskiwanie energii słonecznej)
Keywords: Transformerless Power Conversion, DC-DC Converter, Solar Energy Harvesting
Słowa kluczowe: Beztransformatorowa konwersja mocy, konwerter DC-DC, pozyskiwanie energii słonecznej
Introduction
Background:
Amid the global push for renewable energy, solar power has gained prominence due to its abundance and minimal environmental impact. Solar panels, powered by photovoltaic cells, convert sunlight into electricity, offering a sustainable and appealing energy source (Zhang, 2016) [1]. However, solar panel efficiency is affected by factors like temperature, shading, and sunlight angles, leading to voltage and current fluctuations. To optimize energy capture, efficient DC-DC converters are essential components in photovoltaic systems.
A primary challenge in solar power is efficiently raising the low-voltage output from solar panels to levels suitable for grid integration or powering diverse loads. Traditional DC-DC converters often fall short in voltage gain, resulting in energy losses and decreased system efficiency. Moreover, they can add complexity, increasing costs and maintenance (Zhang, 2016).
Rationale for Research:
Developing high voltage gain DC-DC converters for solar power addresses the need for more efficient energy conversion. These converters offer key advantages for solar energy adoption. They can significantly enhance energy harvesting, even under less-than-ideal conditions, improving overall system efficiency and investment returns. Furthermore, the proposed converter is, eliminating bulky and costly transformers found in traditional power systems. Transformerless designs reduce weight, save space, and enhance reliability, making them attractive for solar power. The converter’s simplicity and reduced component stress result in longer lifespans and lower maintenance costs (Rathore & Babu, 2018) [2].
Aim and Scope of the Study:
This study bridges a critical gap in solar power with a transformerless high voltage gain DC-DC converter tailored for solar energy. It covers design, analysis, implementation, and evaluation. Objectives include achieving high voltage gain, ensuring operational simplicity, and optimizing efficiency, especially in real-world scenarios. Performance will be rigorously assessed via MATLAB 2021 modeling, comparing with existing solutions. The study also explores the converter’s suitability for powering motors, showcasing its versatility beyond solar energy (Alzahrani & Rahman, 2017) [3].
Literature Review
The global push towards sustainable energy solutions and the imperative to reduce carbon emissions have thrust solar power into the forefront of clean and abundant energy sources. Photovoltaic (PV) systems have been instrumental in harnessing solar energy for various applications, from small-scale residential installations to large-scale solar farms [4]. However, to fully harness the potential of solar power and create a sustainable energy future, the development and implementation of high voltage gain DCDC converters tailored specifically for solar applications have become increasingly critical. Efficient energy conversion is pivotal in maximizing the performance of PV systems. Solar panels, the foundation of solar energy generation, are susceptible to various environmental factors, including temperature fluctuations, shading, and variations in solar irradiance [5]. These factors can lead to fluctuations in the output voltage and current of solar panels, directly impacting the overall energy yield of PV systems (Smith et al., 2021) [6]. To address these challenges and enhance energy harvesting efficiency, high voltage gain DC-DC converters have emerged as indispensable components in PV systems.
High voltage gain DC-DC converters offer several key advantages that make them ideal for solar power integration. Firstly, they have the potential to significantly enhance the energy harvesting capabilities of solar panels. By efficiently boosting the output voltage, these converters ensure that a larger portion of the available solar energy is captured, even under suboptimal conditions (Smith et al., 2021). This translates to increased overall system efficiency and a more favourable return on investment for solar installations [4]. Furthermore, the transformerless design of these converters eliminates the need for bulky and expensive transformers, reducing system weight, physical footprint, and improving overall reliability (Johnson & Wang, 2020) [7]. This feature makes high voltage gain DC-DC converters particularly attractive for solar power applications. To advance high voltage gain DC-DC converters for solar applications, comprehensive mathematical modelling and practical validation are essential. Mathematical modelling, typically conducted using tools like MATLAB, enables the assessment of the converter’s performance under varying operating conditions (Smith et al., 2021). These models provide valuable insights into efficiency, voltage gain, and system behaviour. Practical validation, exemplified by the construction of a 200 W prototype in a laboratory setting (Johnson & Wang, 2020), validates theoretical findings and ensures the converter’s effectiveness in real-world scenarios. This iterative process allows researchers to fine-tune designs and optimize performance. While high voltage gains DC-DC converters are initially designed for solar applications, their versatility extends beyond the realm of solar power. Research indicates that these converters can efficiently power motor loads (Brown & Smith, 2022) [8]. This versatility opens up diverse applications, where these converters can contribute to energy-efficient and sustainable solutions. Recent research has delved into advanced control algorithms for high voltage gain DC-DC converters, aiming to further improve their efficiency and performance (Li et al., 2023) [9]. Additionally, the exploration of wide-bandgap semiconductor devices for these converters promises higher efficiency and greater reliability [10-14].
In nutshell, high voltage gain DC-DC converters represent a significant advancement in the field of solar power generation. These converters offer the potential to significantly enhance energy harvesting efficiency, reduce system complexity, and improve overall performance. As solar power continues to play a pivotal role in the transition to renewable energy sources, innovative technologies like high voltage gain DC-DC converters will drive progress towards a sustainable and greener future.
Proposed System
The proposed solar power integration system block diagram highlights key components and their connections for efficient solar energy utilization. It centers on a high voltage gain DC-DC converter designed for solar use. The elements in the block diagram include:
Solar Panels: These panels are the initial energy source, converting sunlight into DC electricity, subject to solar conditions.
High Voltage Gain DC-DC Converter: The system core, efficiently elevating solar panel output to power various applications, enhancing energy harvesting efficiency.
Load: The converter’s output can drive electrical loads like BLDC motors.
Feedback Loop: This loop links the monitoring system to the converter, facilitating real-time adjustments based on performance and environmental data, thus enhancing system adaptability and efficiency.
Fig. 2 displays the circuit diagram of the high voltage gain DC-DC converter, efficiently stepping up low-voltage DC input from solar panels for optimized energy harvesting. Key components are as follows:
Switches (S1 and S2): Control current flow, alternating between open and closed states to manage energy transfer.
Inductors (L1 and L2): Store electrical energy as magnetic fields, aiding energy control.
Diodes (D1, D2, D3, D4, and Do): Permit one-way current flow, serving functions like rectification and circuit isolation.
Capacitors (C1, C2, C3, C4, and Co): Store electric energy, stabilizing voltage levels and smoothing output.
To ensure theoretical fulfillment and performance optimization, the proposed converter will undergo a comprehensive analysis, covering:
Operation in Continuous-Conduction Mode (CCM) and Discontinuous-Conduction Mode (DCM): Understanding behavior under different loads.
Voltage Gain Derivation: Efficient voltage boosts analysis. External Characteristics: Examination of input and output voltage-current relationships for interaction with external loads and power sources.
Voltage and Current Stress: Assessment of component stresses for design considerations.
Design Considerations: Exploration of component values, sizing, and arrangement for optimization.
Estimated Efficiency: Estimation of converter efficiency under various operating conditions.
Modelling: Creating a detailed converter model using tools like MATLAB 2021 for a deeper understanding of behavior.
Control: Discussion of control algorithms and mechanisms to ensure efficient operation and adaptation to changing conditions.
Fig. 2 displays the composition of the high voltage gain DC-DC converter, featuring two switches (S1 and S2), two inductors (L1 and L2), five diodes (D1, D2, D3, D4, and Do), and five capacitors (C1, C2, C3, C4, and Co). Component placement within this converter is a crucial factor, serving to minimize current and voltage stress, enhance voltage gain, and maintain operational simplicity. To verify these aspects, a comprehensive theoretical and experimental analysis of the proposed converter is carried out.
Modes of Operation:
Stage I – Continuous-Conduction Mode (CCM): When switches S1 and S2 are both in the ON state, L1 and L2 energize, allowing current flow. Diodes D1, D2, and Do are reverse-biased, while capacitors C1, C2, and Co discharge into C3, C4, and the load (R). Diodes D3 and D4 are forward-biased, and capacitors C3 and C4 charge.
Stage II – Continuous-Conduction Mode (CCM): This phase follows when both S1 and S2 are switched OFF. During this stage, L1 and L2 demagnetize, and diodes D1 and D2 charge C1 and C2. The output diode Do is forward-biased, charging output capacitor Co with VC3 + VC4 – VC2. Diodes D3 and D4 are reverse-biased, and capacitors C3 and C4 discharge.
Stage III – Discontinuous-Conduction Mode (DCM): Exclusive to DCM, this stage begins when the current through the inductors reaches zero. At this point, all semiconductor devices are blocked, and the load (R) is powered by the output capacitor (Co).
To establish the static gain of the converter, the volts– seconds balance principle is applied to the inductors, and capacitor voltages (VC1, VC2, VC3, VC4) are calculated based on the voltage across the inductors in stages I and II. The static gain (M) is determined in Stage II (Vo = VC3 + VC4 – VC2). Additionally, it’s important to consider nonideal voltage gain, which relies on parasitic parameters like component resistances and forward voltages, as these factors can significantly impact the converter’s performance and must be considered for precise analysis and design.
Results and Discussions
Modelling the proposed system in MATLAB 2021 is a crucial step in assessing its performance and efficiency. The use of simulation allows for a detailed analysis of how the system behaves under various conditions, helping to refine the design and optimize its operation (Figure 3).
In Figure 4, we present a detailed model of the solar panel, a critical component responsible for capturing and converting solar energy into electrical power. The key elements and features include:
Solar PV Array: Comprising two parallel-connected PV arrays, each with 217 individual PV cells. This parallel connection enhances current output while maintaining voltage levels.
PV Cells: These fundamental units of solar energy conversion number 217 per array, arranged strategically to influence electrical characteristics. Cell Arrangement: Strategically placed PV cells aim to maximize energy capture, impacting efficiency and performance. Common patterns involve series and parallel connections.
Interconnection: Proper PV cell and array interconnection ensures efficient electrical flow, affecting voltage and current ratings. Effective interconnection minimizes losses.
Bypass Diodes: Integrated to mitigate shading or damage effects, these diodes allow current to bypass unlit sections, preventing power loss.
Figure 5 presents input parameters for the high voltage gain DC-DC converters powered by a solar panel with the following specifications: a) Voltage (Fig. 5a): The solar panel supplies 75V, determining the initial electrical potential for the converters. Solar system voltage varies based on solar irradiance and temperature. b) Current (Fig. 5b): The solar panel yields 7.6A, essential for calculating total electrical power generated. c) Power (Fig. 5c): The solar panel outputs 560W, indicating its capacity to generate electrical energy. These parameters are the initial energy source for the converters, responsible for stepping up input voltage for various applications.
Figure 6 provides an overview of output parameters for the motor load connected to the high voltage gain DC-DC converter: a) Load Terminal Voltage (Fig. 6a): The voltage at the load terminal is 440V, crucial for the motor’s operation. b) Armature and Field Current (Fig. 6b): Armature current is 5A, field current is 0.9A, influencing the motor’s electromagnetic interactions and torque. c) Load Torque (Fig. 6c): The load torque is 8Nm, representing the rotational force required. d) Motor Speed (Fig. 6d): The motor operates at 1400rpm, a critical aspect of motor performance.
Figure 7 shows the transition from an open-loop to a closed-loop control system for the motor load, leading to key improvements: a) Motor Rated Voltage (Fig. 7a): The motor’s rated voltage is maintained at 380V. b) Motor Current (Fig. 7b): The motor’s current is controlled at 5A. c) Motor Speed (Fig. 7c): The motor now operates at 1500rpm. d) Torque (Fig. 8d): The motor generates 10Nm of torque. These innovations optimize the motor load’s behavior and responsiveness to varying operating conditions.
Comparison with Existing Work
Compared to existing work in high voltage gain DC-DC converters and renewable energy systems, this study distinguishes itself with its transformerless design, improved efficiency, and integration of closed-loop control. Many conventional converters rely on transformers, adding complexity and cost. In contrast, the proposed transformerless design reduces these drawbacks. Moreover, the achieved increase in overall system efficiency is a significant advance, reducing energy losses during conversion. The closed-loop control system’s precise regulation of the motor load sets this work apart, enabling optimal motor performance under varying conditions. These innovations make this work a significant contribution to sustainable and efficient energy solutions.
Conclusions
In conclusion, this study explores the development and evaluation of a high voltage gain DC-DC converter tailored for solar power applications. With the world’s focus on sustainable energy and emissions reduction, solar power is a key player in cleaner electricity generation. This converter’s transformerless design reduces complexity, costs, and enhances reliability while minimizing size and weight. Its high voltage gain boosts energy harvesting, increasing overall efficiency and ROI for solar installations. Closed-loop control for motor loads ensures precise regulation and performance. These innovations mark a significant contribution to renewable energy advancement, addressing the need for efficient energy conversion and paving the way for a sustainable energy future.
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Source & Publisher Item Identifier: PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 100 NR 4/2024. doi:10.15199/48.2024.04.45
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