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Partial shading conditions can cause low output power, hotspots, and a reduced lifespan in photovoltaic arrays. Interconnection (IC) and differential power processing (DPP) can be used to mitigate these effects. When individually applied to an array, these techniques can significantly increase the generated power. A few authors studied the combined use of these schemes under specific conditions such as large-scale arrays or a complex combination of several techniques, making it difficult to identify the individual contribution of each technique. Here, we aimed to determine whether the combined use of a switching-inductor DPP circuit and a total-cross-tied interconnection scheme presents better performance than each standalone technique, using a small-scale photovoltaic array. An array was tested using IC, DPP, and a combination of both techniques, and the array was subjected to 13 shading patterns and two irradiance levels. The performance in each case was assessed using maximum output power, performance ratio, mismatch power loss, and power enhancement indicators. The results showed that a standalone differential power processing circuit presents better performance than when it is combined with an interconnection. The DPP showed performance ratio values of up to 97%, mismatch power losses lower than 36.9%, and a power enhancement of up to 95.9%. The standalone interconnection shows the worst performance among the three techniques. [ABSTRACT FROM AUTHOR]

In the current landscape of renewable energy systems, optimizing the performance of power electronic converters is crucial for ensuring reliability. Within the realm of direct current (DC)–DC power converter systems, the differential power processing (DPP) converter holds promise. However, realizing its full potential requires meticulous system design, especially in response to varying solar irradiation levels. Poor design can result in performance degradation, leading to system damage and voltage instability due to sudden irradiation fluctuations. To address these challenges, this study investigates the performance optimization of a DPP converter enhanced with a modified switched inductor, tailored for solar photovoltaic applications. To overcome traditional control strategy limitations, we propose an innovative enhanced fuzzy logic controller (E-FLC). This controller's strength lies in its dynamic adaptability, achieved through variable duty cycle control, input parameters, membership functions, and output responses. This paper emphasizes methodological precision, particularly in applying the E-FLC to the modified switched inductor. The use of this controller significantly improves both steady-state and transient response performance compared to traditional switched inductors. It rigorously analyzes the responses of the DPP converter under steady-state and transient conditions, with and without the modified switched inductor. This analytical approach sheds light on a critical yet often overlooked aspect of photovoltaic systems. The core innovation driving this research is the adoption of the E-FLC, which outperforms the commonly used proportional–integral (PI) controller in steady-state performance and transient response characteristics. This paper goes beyond conventional converter optimization studies by introducing a holistic approach encompassing system dynamics, control strategy innovation, and performance evaluation. The proposed E-FLC represents a methodological breakthrough and a substantial improvement in converter efficiency and reliability. As renewable energy continues to reshape the global energy landscape, this research sets a new standard for harnessing the true capabilities of power electronic converters in solar photovoltaic systems. [ABSTRACT FROM AUTHOR]

Partial shading is a prevalent phenomenon with a substantial impact on PV system performance. Various techniques, such as maximum power tracking (MPPT), PV module interconnection, and power electronics-based schemes, have been employed to address these challenges at both the module level and the submodule level. Existing methods face limitations related to the cost of hardware and the complexity of control systems. These limitations hinder the widespread application of current solutions. Also, Module-level techniques though simple and economical provide limited granularity. The choice between these techniques involves a trade-off between complexity, cost, adaptability, and the specific characteristics of the PV system and its operating environment.This paper presents a new hybrid submodule-level partial shading mitigation scheme based on TCT interconnection and differential power processing. The proposed system, emphasizing its role in enhancing overall PV system performance offers a cost-effective, and easy-to-control solution. To compare and validate the performance of proposed hybrid architecture, a practically installed single-phase grid tied central inverter 3 kW residential PV system is considered. This practical PV system is modified to hybrid architecture and the performance parameters such as power generation, mismatch power loss, fill factor, power conversion efficiency and power improvement calculated for different operating conditions. The results show that the modified conventional PV system mitigate the mismatch issue effectively and improves the output performance for any operating condition

Photovoltaic power generation has received widespread attention for its cleanliness and efficiency. However, due to many reasons like uneven aging and partial shading, power mismatch can easily occur while photovoltaic submodules in series working, resulting in "hot spot" and reducing the utilization rate and service life of photovoltaic cells. In order to deepen students' understanding of photovoltaic cell models and the characteristic caused by series mismatch, as well as how to solve this problem, this paper developed a distributed maximum power point tracking (DMPPT) experimental platform based on a multi-port DC converter for photovoltaic cells. Firstly, the series mismatch characteristics of photovoltaic cells is modeled and analyzed. Then, the voltage equalization strategy of multi-port DC converter for photovoltaic cells was analyzed and studied. Finally, a 36 V/200 W DMPPT experimental platform based on a multi-port Buck-Boost DC converter was developed, and the steady-state waveform of the system was obtained and compared with the method of using bypass diodes. Through this experimental platform and this experimental case, students can have a more in-depth understanding of the PV cell model and its mismatch features, as well as how to use multi-port converters to realize DMPPT of PV cells, master the modeling method of PV cells, and cultivate the practical ability of discovering problems, solving problems, and verifying through simulation. [ABSTRACT FROM AUTHOR]

Partial shading conditions can cause low output power, hotspots, and a reduced lifespan in photovoltaic arrays. Interconnection (IC) and differential power processing (DPP) can be used to mitigate these effects. When individually applied to an array, these techniques can significantly increase the generated power. A few authors studied the combined use of these schemes under specific conditions such as large-scale arrays or a complex combination of several techniques, making it difficult to identify the individual contribution of each technique. Here, we aimed to determine whether the combined use of a switching-inductor DPP circuit and a total-cross-tied interconnection scheme presents better performance than each standalone technique, using a small-scale photovoltaic array. An array was tested using IC, DPP, and a combination of both techniques, and the array was subjected to 13 shading patterns and two irradiance levels. The performance in each case was assessed using maximum output power, performance ratio, mismatch power loss, and power enhancement indicators. The results showed that a standalone differential power processing circuit presents better performance than when it is combined with an interconnection. The DPP showed performance ratio values of up to 97%, mismatch power losses lower than 36.9%, and a power enhancement of up to 95.9%. The standalone interconnection shows the worst performance among the three techniques.

In recent years, in order to improve the fuel efficiency of electric vehicles, a lot of research has been conducted to adopt photovoltaic (PV) systems to electric vehicles. In addition, various Differential Power Processing (DPP) converters that can mitigate power imbalance among submodules in PV systems are being studied and developed. However, most conventional DPP converters suffer from large volume, low-price competitiveness, and low efficiency. Therefore, in this paper proposes a novel DPP converter. The proposed DPP converter can significantly reduce the volume of converter by integrating multiple transformers into single transformer. Moreover, because of the active clamp structure, it is possible to eliminate secondary side circuits. Furthermore, more than 95% efficiency under 10-60% load and maximum 96.654% efficiency about 20% load were achieved. Thus, the proposed DPP converter can achieve high power density, high price competitiveness, as well as high efficiency. To support the validity of the proposed converter, a prototype of the proposed DPP converter was built, and experiments were proceeded with 8V input and 60W/30V output specifications.

In the face of the increasing depletion of non-renewable energy sources and increasingly serious environmental problems, the development of green and environmentally friendly renewable energy sources cannot be delayed. Because of the far-reaching development potential of solar energy, solar power has become an important research object for power development. The available solar energy in space is several times greater than that on Earth. Solar energy from space can be collected by a space solar power station (SSPS) and transmitted to the ground by wireless power transfer. In the full-chain ground-based validation system of SSPS-OMEGA, the spherical concentrator is used, and the light intensity distribution on the solar receiver is non-uniform. The non-uniform light intensity makes the output current of each photovoltaic (PV) cell on the solar receiver greatly different, and causes power losses, known as the mismatch problem. This paper proposes a simple, efficient and easy-to-implement method to optimize the structure of PV arrays to reduce the effect of non-uniform light on the output performance of each PV cell, which is beneficial to the topology of PV arrays and also effectively improves the layout rate. Then, a differential power processing (DPP) converter with a simple structure and easy control is designed to further deal with the power mismatch problem between series-connected PV modules. Finally, a simulation circuit model and a physical hardware model of the differential power processing PV system are built and used in the full-chain ground-based validation system of SSPS-OMEGA. The results demonstrate that the influence of non-uniform lighting on PV cells is effectively reduced, the output power of PV modules connected in series under non-uniform light distribution is substantially increased, and the photoelectric conversion efficiency is significantly improved. [ABSTRACT FROM AUTHOR]

With the growing interest in owning electric vehicles due to increased environmental awareness and uncertain energy security together with the development of Li-ion batteries, quietness, and trouble-free operation, it is urgent to develop charging stations that are fast enough to supply the vehicles with energy conveniently, as in case of conventional petrol stations. The main reason that hinders the spread of fast charging stations is the installation cost, comprising the infrastructure and converter costs. In this article, a multiport DC-DC converter with differential power processing stages is proposed for Electric Vehicle (EV) fast charging stations, which results in a considerable reduction in the cost of using converters while achieving high efficiency. The proposed topology consists of two paths for the power flow (outer and inner loops) for EV battery charging with main and auxiliary DC-DC converters in the outer loop; all the ports are connected in series with the main supply, where the bulk power is being transferred. The main DC-DC converter injects a series voltage to control the power in the outer loop. The auxiliary DC-DC converters are rated at a fractional power that controls the partial power supplied to each port through the inner loops. Thanks to the fractional power processed by the auxiliary converter with the remaining power fed to the battery through the main converter, the proposed architecture enables simultaneous charging of multiple electric vehicles with better efficiency, lower cost, and the capability of providing a fault tolerance feature. A PWM control scheme for the converters to achieve bi-directional power flow in the partially rated DC-DC converters is discussed for the proposed system. Moreover, a practical down-scaled hardware prototype is designed to validate the functionality, control scheme, and effectiveness of the proposed topology in different case studies being investigated. The efficiency of the proposed converter is compared to the conventional configuration. [ABSTRACT FROM AUTHOR]

Solar photovoltaic (PV) systems continue to be the most prevalent renewable energy resource despite the presence of numerous limitations. A power discrepancy between PV modules on a large scale may result in power dissipation throughout the entire PV system. This particular paper proposes an efficient multi-port converter for distributed maximum power point tracking operation (D-MPPT) for a solar PV system. The operation details of the proposed multi-port converter along with analytical waveforms are presented in this paper. To implement the D-MPPT approach in the proposed multi-port converter, a detailed analysis of mathematical modeling of solar PV systems with a mismatch of PV power and voltage stabilization approach is done. In addition, the proposed approach eliminates the need for additional current sensors and semiconductor components to overcome the effect of mismatched power in the PV system. To validate this, the prototype has been built and integrated with the real environment of the solar PV system. To verify the operation, a detailed simulation study and experimental investigation have been carried out and presented in this paper which reveals that the proposed system offers 24% improved power extraction compared to the centralized converter and MPPT method under partially shaded conditions. After a detailed investigation and discussion of measured results and analysis, it is concluded that the proposed multi-port DC-DC converter is the most suitable solution for solar PV applications.

In the face of the increasing depletion of non-renewable energy sources and increasingly serious environmental problems, the development of green and environmentally friendly renewable energy sources cannot be delayed. Because of the far-reaching development potential of solar energy, solar power has become an important research object for power development. The available solar energy in space is several times greater than that on Earth. Solar energy from space can be collected by a space solar power station (SSPS) and transmitted to the ground by wireless power transfer. In the full-chain ground-based validation system of SSPS-OMEGA, the spherical concentrator is used, and the light intensity distribution on the solar receiver is non-uniform. The non-uniform light intensity makes the output current of each photovoltaic (PV) cell on the solar receiver greatly different, and causes power losses, known as the mismatch problem. This paper proposes a simple, efficient and easy-to-implement method to optimize the structure of PV arrays to reduce the effect of non-uniform light on the output performance of each PV cell, which is beneficial to the topology of PV arrays and also effectively improves the layout rate. Then, a differential power processing (DPP) converter with a simple structure and easy control is designed to further deal with the power mismatch problem between series-connected PV modules. Finally, a simulation circuit model and a physical hardware model of the differential power processing PV system are built and used in the full-chain ground-based validation system of SSPS-OMEGA. The results demonstrate that the influence of non-uniform lighting on PV cells is effectively reduced, the output power of PV modules connected in series under non-uniform light distribution is substantially increased, and the photoelectric conversion efficiency is significantly improved.

Series-stacked architectures have been successfully deployed for data center applications at substantially higher efficiencies than conventional power delivery architectures. In the series-stacked architectures, servers are series-connected electrically to reduce the high step-down conversion stage of voltage utilized in the conventional architectures. Differential power processing converters are, therefore, used to regulate the servers’ voltages and compensate for the unpredicted mismatch between servers’ currents. The main contribution of this paper comprises novel control approaches based on PI controllers purposeful for the two architectures that have reported the highest reliability and efficiency in differential power processing namely: server-to-bus and server-to-virtual bus. Both systems employ a dual active bridge (DAB) converter to accommodate the fluctuating loads of each server. Unlike hysteresis current/voltage control commonly employed in the available literature, the proposed control approaches offer less complexity, lower harmonics, and higher immunity towards the noise, thus no need for high-quality sensors to successfully achieve voltage balance and/or optimal string current flow. Moreover, a comparative study has been structured between the investigated series-stacked architectures under the proposed PI control approaches showing the merits and the demerits of each architecture. The proposed controllers have been validated based on simulations and experimentally.

• A mathematical analysis of the mismatch in photovoltaic strings is proposed. • The diverted current accumulation phenomenon is assessed in detail. • It is proven that the shading position influences energy harvesting. Differential power processing (DPP) architectures have been emerging as a promising strategy for mitigating the harmful effects of the photovoltaic (PV) string mismatches. In this strategy, DPP converters are connected in parallel with the PV string to improve the energy harvesting. However, in some situations, the position, intensity of shading, and the length of the string negatively influence the performance of such architectures. In this context, this work presents a novel mathematical approach that enables analyzing the effect of such aspects in the output power and efficiency of the PV-to-PV architecture. The set of derived equations allows determining the values of the currents flowing through the DPP converters that compose the PV-to-PV architecture. An important aspect is validated by the mathematical analysis, proving that the shading position on the PV-to-PV architecture directly impacts the phenomenon known as diverted current accumulation. To the best of the authors' knowledge, this issue has not yet been assessed in the literature. Besides, this study is of major importance because it influences the losses in the power converters of the DPP structure. The assessment of various shading positions on the PV-to-PV architecture reveals that, in specific positions, the currents that flow through the converters are significantly reduced. For the set of situations analyzed, an improved energy harvesting from the PV-to-PV architecture and efficiency over 95% are verified. [ABSTRACT FROM AUTHOR]

This article presents a cell-level differential power processing IC to maximize the power yield under partial shading and mismatch condition in series-connected single junction photovoltaic (PV) cells. A 3-MHz bidirectional buck–boost converter is employed to realize voltage equalization technique forcing the PV cells to constantly operate close to their maximum power points. A novel and simple low-power low-area analog control circuit is proposed to maintain the high system efficiency at low and high levels of mismatch by obviating the need for power hungry blocks such as analog to digital converters, digital to analog converters, op-amps, saw-tooth generator, and regulators. The voltage of adjacent PV cells is used to drive the high-side switches through bootstrap supplies eliminating the need for voltage regulators. The performance of the proposed IC, fabricated in 130 nm CMOS process, is validated through simulation and experimental results. The converter is capable of processing mismatch currents up to 4 A while the control circuitry consumes less than 40 mW and a system efficiency above 95% is achieved. [ABSTRACT FROM AUTHOR]

Solar energy is one of the most promising energy types, but photovoltaic (PV) mismatches have several negative effects. Finding an efficient and low-cost method to reduce or eliminate the power loss caused by the mismatch in PV power generation systems is necessary. In this paper, we propose a PV submodule-distributed maximum power point tracking (DMPPT) scheme based on a multi-port DC converter. In-depth analysis and research are performed on the PV model and mismatch characteristics, the PV module voltage equalization (VE) strategy, and implementation with the multi-port buck–boost converter. We discuss the trade-off between true DMPPT and VE on control overhead and tracking accuracy, and a detailed derivation is created to illustrate the differences between them. The VE can reduce the cost and complexity of the system at the expense of a small PV energy capture. The proposed implementation reduces the number of semiconductor components and current sensors, which is conducive to the integrated design of the hardware. A prototype based on a multi-port buck–boost converter for a 36 V/200 W PV module was designed and built. The feasibility and progress of the proposed scheme were verified through experiments. [ABSTRACT FROM AUTHOR]

The number of data centers worldwide has been growing exponentially to serve a multitude of aspects of modern life. The major challenges that face data centers operators are the rising electricity bills, growing carbon footprints, and unexpected power outages. An effective approach to tackle such problems is to investigate the implementation of efficient power supplies that offers the rack voltage levels required to power servers. Recently, the differential power processing (DPP) concept proved to potentially offer less number of cascaded stepping down stages by connecting the servers in series and introducing a DPP converter to supply or withdraw current mismatch in the series connection. DPP system can replace the conventional two-stage power electronics converter with an efficiently designed converter. Thus, the series stacking power delivery architecture is proposed with efficient Gallium Nitride (GaN) based power electronics converters to reduce the system size and losses. The introduced review in this paper aims to give the reader a comprehensive understanding of DPP implementation for data centers in terms of the possible series stacking architecture, converter types and switch types. The advantages and disadvantages of each architecture are discussed along with the most commonly employed DPP converters in various applications. Further investigation on the cost-effectiveness and commercialization of GaN-based series stacking architecture still needs further investigation and deployment.

The wind turbine startup and shutdown procedures for electrical subsystems are straightforward for wind turbines featuring full-scale power electronic converters and have not required significant attentions from the research community. However, for offshore wind farms featuring series-connected dc collection systems and differential power processing capabilities, the controllable wind turbine power converters might not be rated in such a way that a full-scale output power difference can be handled within a series string. As startup and shutdown procedures can require a transition from zero to full power, a more elaborate design is required to ensure that wind turbines can still start and stop reliably under all conditions, without compromising advantages in reduced wind turbine converter ratings with differential power processing capabilities. In this paper, the startup and shutdown procedures for a series-dc wind farm featuring diode-bridge rectifiers and partial power processing converters as wind turbine converters, are investigated and constraints on converter ratings are evaluated.

Due to the increasing throughput of high-performance integrated circuits, the power consumption of recent high-performance computing systems has grown significantly, leading to greater on-chip current demand. The large current flowing within the power delivery system produces challenging issues, such as electromigration, low power efficiency, and thermal hot spots. To reduce on-chip current demand, voltage stacking has become a topic of growing interest within the industrial and academic communities. The challenges of power delivery for on-chip voltage stacked systems are, however, significant. The power delivery system connects individual stacks and stacks to converters. Challenges include cross-core current paths. A tile-based power delivery design methodology is proposed for high current, voltage stacked systems. The tile-based power delivery system provides net separation, low parasitic impedance, and a scalable design process. The tile shape eases the design and characterization of the parasitic impedance, making this methodology effective for early stage exploration of the power delivery system within voltage stacked structures. [ABSTRACT FROM AUTHOR]

Partial shading is a serious problem limiting the efficiency of photovoltaic (PV) systems. Differential power processing (DPP) architectures have been proposed to mitigate mismatch power losses caused by partial shading. However, maximum power point tracking (MPPT) for DPP converters is still an area of research. Instead of employing heuristic techniques, the proposed method is deterministic that can uniquely determine the respective maximum power points (MPPs) for the DPP Converters relying on the PV mathematical model and provided incident irradiances. The irradiances of the submodules are estimated using captured images obtained by an optical camera. Unlike the existing methods in literature which either produce fast transient response or accurate steady state tracking, the proposed method provides both fast transient response and accurate steady state output without oscillations. Moreover, the proposed approach does not need communication between converters or current sensing for the MPPT. The effectiveness of the proposed method is validated both by Simulink simulations and experimentally. [ABSTRACT FROM AUTHOR]

Series-stacked architectures have been successfully deployed for data center applications at substantially higher efficiencies than conventional power delivery architectures. In the series-stacked architectures, servers are series-connected electrically to reduce the high step-down conversion stage of voltage utilized in the conventional architectures. Differential power processing converters are, therefore, used to regulate the servers' voltages and compensate for the unpredicted mismatch between servers' currents. The main contribution of this paper comprises novel control approaches based on PI controllers purposeful for the two architectures that have reported the highest reliability and efficiency in differential power processing namely: server-to-bus and server-to-virtual bus. Both systems employ a dual active bridge (DAB) converter to accommodate the fluctuating loads of each server. Unlike hysteresis current/voltage control commonly employed in the available literature, the proposed control approaches offer less complexity, lower harmonics, and higher immunity towards the noise, thus no need for high-quality sensors to successfully achieve voltage balance and/or optimal string current flow. Moreover, a comparative study has been structured between the investigated series-stacked architectures under the proposed PI control approaches showing the merits and the demerits of each architecture. The proposed controllers have been validated based on simulations and experimentally. [ABSTRACT FROM AUTHOR]

Differential power processing (DPP) is regarded as a promising architecture in solving mismatching issues among photovoltaic (PV) submodules. Although conventional total-minimum-power-point (TMPP)-based real-time optimization algorithm by using the distributed submodule-level maximum power point tracking and simultaneously the centralized total-minimum-power tracking shows effectiveness in maximizing the power yield. However, uneven power stress among DPP converters, large oscillations, high additional cost for communication among DPP converters, and complicated implementation hinder the practical application. This article proposed a low-complexity power balancing point-based optimization algorithm to reduce the system cost and size, improve the system efficiency, and realize the standardized modular design for DPP converters. Furthermore, simple submodule-level voltage equalization control is implemented to eliminate expensive communication and relieve the control complexity while guaranteeing high maximum-power-point efficiency. The proposed algorithm can reduce the power rating of DPP converters compared with conventional TMPP-based control, which is beneficial to the improvement of system cost, reliability, and lifetime. Both simulation and experimental results under various scenarios are provided to validate the advantages of the proposed algorithm. [ABSTRACT FROM AUTHOR]

The number of data centers worldwide has been growing exponentially to serve a multitude of aspects of modern life. The major challenges that face data centers operators are the rising electricity bills, growing carbon footprints, and unexpected power outages. An effective approach to tackle such problems is to investigate the implementation of efficient power supplies that offers the rack voltage levels required to power servers. Recently, the differential power processing (DPP) concept proved to potentially offer less number of cascaded stepping down stages by connecting the servers in series and introducing a DPP converter to supply or withdraw current mismatch in the series connection. DPP system can replace the conventional two-stage power electronics converter with an efficiently designed converter. Thus, the series stacking power delivery architecture is proposed with efficient Gallium Nitride (GaN) based power electronics converters to reduce the system size and losses. The introduced review in this paper aims to give the reader a comprehensive understanding of DPP implementation for data centers in terms of the possible series stacking architecture, converter types and switch types. The advantages and disadvantages of each architecture are discussed along with the most commonly employed DPP converters in various applications. Further investigation on the cost-effectiveness and commercialization of GaN-based series stacking architecture still needs further investigation and deployment. [ABSTRACT FROM AUTHOR]

By a rearrangement of the traditional supply-converter-load system connection, partial-power-processing-based converters can be used to achieve a reduction in size and cost, increase in system efficiency and lower device power rating. The concept is promising for different applications such as photovoltaic arrays, electric vehicles and electrolysis. For photovoltaic applications, it can drive each cell in the array to its maximum power point with a relatively smaller converter; for electric-vehicle applications, both an onboard charger with reduced weight and improved efficiency as well as a fast charger station handling higher power can be considered. By showing different examples of partial-power-processing application for energy-conversion and storage units and systems, this paper discusses key limitations of partial-power-processing and related improvements from different perspectives to show the potential in future power electronic systems. [ABSTRACT FROM AUTHOR]

• A topology capable of dealing with permanent mismatch is introduced. • High efficiency results owing to the operation under zero-current condition. • Design flexibility allows its application to any even number of modules. Differential power processing (DPP) architectures are a prominent solution for mitigating undesirable issues caused by mismatch that often occurs in photovoltaic (PV) strings. In this scenario, the association of DPP converters in parallel with PV strings is a common approach for enhancing energy harvesting. However, most topologies presented so far focus on temporary mismatch caused by partial shading conditions only, with little attention given to permanent mismatch due to the connection of modules with distinct ratings. Given the above, this article presents a novel DPP topology capable of handling both temporary and permanent mismatch in PV strings. Important advantages include lower component count; reduced voltage stresses on the active switches; operation under zero-current switching (ZCS) condition, with a direct impact on the converter efficiency; and greater design flexibility in terms of a modular solution that can be implemented at the PV module level. Experimental tests on a string composed of six modules are presented and the results are thoroughly discussed to validate the theoretical assumptions. It is effectively demonstrated that the architecture allows for increasing the power extracted from the string under two severe operating conditions. [ABSTRACT FROM AUTHOR]

Partial shading brings many serious problems in the solar photovoltaic system (SPV) such as the significant reduction in power harvest, hot spots, and the emergence of the multiple maximum power points (MPPs). This paper presents a bidirectional flyback converter (BFC) based isolated-port differential power processing (DPP) architecture at the submodule level. Bidirectional flyback converters (BFCs) are designed for submodules with both discontinuous condition mode (DCM) and continuous condition model (CCM) modes for light-load and heavy-load conditions to improve the efficiency. The voltage equalization with open-loop control is adopted for each BFC, this control method keeps the voltage in primary and secondary of the BFCs equal and it does not require additional voltage or current sensors. It’s simple, easy-to-implement and well suited for low-cost integrated hardware scheme. Both simulation and experimental results for an isolated-port DPP regulated 72-cells photovoltaic (PV) module under various partial shading scenarios were provided. It shows that this structure can distinctly mitigate the energy loss in a PV system, increase output power harvest, and achieve high efficiency under partial shading condition. The measured efficiency with the isolated-port DPP structure was 90.23% under severe shading condition. The measured output power improvement under severe mismatch condition was high up to 43.1%. [ABSTRACT FROM AUTHOR]

Solar photovoltaic (PV) power is a widely used to supply power to the electric grid but can also be used in lower-power emerging applications, like in wearables or the internet of things. One fundamental challenge of using PV power in flexible wearable applications is that individual PV modules point at various angles, thus receiving different light intensities. Using a series configuration for the PV modules greatly decreases power utilization under uneven irradiance conditions. Parallel differential power processing (DPP) converters are employed to address this power reduction problem, while maintaining individual PV control and maximizing output power. Two parallel DPP configurations, with and without a front-end converter, are analyzed and compared for a target battery-charging application. The DPP system without a front-end converter shows consistently high performance and operates properly over a wider range of lighting conditions. Maximum power point tracking (MPPT) algorithms are also examined for parallel DPP systems. When the MPPT parameters are properly calibrated, simulation results indicate that voltage-offset resistive control is the most effective at maximizing PV power under unbalanced lighting conditions.

The Differential Power Processing (DPP) converter is a promising multi-module photovoltaic inverter architecture recently proposed for photovoltaic systems. In this paper, a DPP converter architecture, in which each PV-panel has its own DPP converter in shunt, performs distributed maximum power point tracking (DMPPT) control. It maintains a high energy conversion efficiency, even under partial shading conditions. The system architecture only deals with the power differences among the PV panels, which reduces the power capacity of the converters. Therefore, the DPP systems can easily overcome the conventional disadvantages of PCS such as centralized, string, and module integrated converter (MIC) topologies. Among the various types of the DPP systems, the feed-forward method has been selected for both its voltage balancing and power transfer to a modified H-bridge inverter that needs charge balancing of the input capacitors. The modified H-bridge multi-level inverter had some advantages such as a low part count and cost competitiveness when compared to conventional multi-level inverters. Therefore, it is frequently used in photovoltaic (PV) power conditioning system (PCS). However, its simplified switching network draws input current asymmetrically. Therefore, input capacitors in series suffer from a problem due to a charge imbalance. This paper validates the operating principle and feasibility of the proposed topology through the simulation and experimental results. They show that the input-capacitor voltages maintain the voltage balance with the PV MPPT control operating with a 140-W hardware prototype. [ABSTRACT FROM AUTHOR]

Differential power processing (DPP) systems are a promising architecture for future photovoltaic (PV) power systems that achieve high system efficiency through processing a faction of the full PV power, while achieving distributed local maximum power point tracking (MPPT). In the PV-to-bus DPP architecture, the power processed through the DPP converters depends on the string current, which must be controlled to minimize the power processed through the DPP converters. A real-time least power point tracking (LPPT) method is proposed to minimize power stress on PV DPP converters. Mathematical analysis shows the uniqueness of the least power point for the total power processed through the system. The perturb-and-observe LPPT method is presented that enables the DPP converters to maintain optimal operating conditions, while reducing the total power loss and converter stress. This work validates through simulation and experimentation that LPPT in the string-level converter successfully operates with MPPT in the DPP converters to maximize output power for the PV-to-bus architecture. Hardware prototypes were developed and tested at 140 and 300 W, and the LPPT control algorithm showed effective operation under steady-state operation and an irradiance step change. Peak system efficiency achieved with a 140-W prototype DPP system employing LPPT is 95.7%. [ABSTRACT FROM PUBLISHER]

This paper describes photovoltaic (PV) module architectures with parallel-connected submodule-integrated dc–dc converters (subMICs) that improve efficiency of energy capture in the presence of partial shading or other mismatch conditions. The subMICs are bidirectional isolated dc–dc converters capable of injecting or subtracting currents to balance the module substring voltages. When no mismatches are present, the subMICs are simply shut down, resulting in zero insertion losses. It is shown that the objective of minimum subMIC power processing can be solved as a linear programming problem. A simple close-to-optimal distributed control approach is presented that allows autonomous subMIC control without the need for a central controller or any communication among the subMICs. Furthermore, the proposed control approach is well suited for an isolated-port architecture, which yields additional practical advantages including reduced subMIC power and voltage ratings. The architectures and the control approach are validated by simulations and experimental results using three bidirectional flyback subMICs attached to a standard 180-W, 72-cell PV module, yielding greater than 98% module-level power processing efficiency for a mismatch less than 25%. [ABSTRACT FROM AUTHOR]

Conventional energy conversion architectures in photovoltaic (PV) systems are often forced to tradeoff conversion efficiency and power production. This paper introduces an energy conversion approach that enables each PV element to operate at its maximum power point (MPP) while processing only a small fraction of the total power produced. This is accomplished by providing only the mismatch in the MPP current of a set of series-connected PV elements. Differential power processing increases overall conversion efficiency and overcomes the challenges associated with unmatched MPPs (due to partial shading, damage, manufacturing tolerances, etc.). Several differential power processing architectures are analyzed and compared with Monte Carlo simulations. Local control of the differential converters enables distributed protection and monitoring. Reliability analysis shows significantly increased overall system reliability. Simulation and experimental results are included to demonstrate the benefits of this approach at both the panel and subpanel level. [ABSTRACT FROM AUTHOR]

This paper introduces an approach to dc power delivery that reduces power loss by minimizing redundant energy conversion. Existing power distribution techniques tend to increase the number of cascaded conversion stages, which limits overall efficiency. Differential power processing enables independent load regulation, while processing only a small portion of the total load power. Bulk power conversion occurs once. Load voltage domains are connected in series, and differential converters act as controllable current sources to regulate intermediate nodes. This enables independent, low supply voltages, which can reduce system energy consumption, especially in digital circuits and solid-state lighting. Since differential voltage regulators process a fraction of the load power, decreased size, cost, and conversion losses are attainable. Under balanced load conditions, secondary differential converters do not process any power. This paper analyzes several differential power delivery architectures that can be applied to homogenous and heterogeneous loads at various levels: chip, board, blade, etc. A variety of operating conditions for a test system with four series voltage domains are examined in simulation and verified with experimental hardware. Results in a reference application show a 7–8% decrease in input power and 6–7 percentage points increase in overall conversion efficiency as compared to a conventional cascaded approach. [ABSTRACT FROM AUTHOR]

Solar photovoltaic (PV) power is a widely used to supply power to the electric grid but can also be used in lower-power emerging applications, like in wearables or the internet of things. One fundamental challenge of using PV power in flexible wearable applications is that individual PV modules point at various angles, thus receiving different light intensities. Using a series configuration for the PV modules greatly decreases power utilization under uneven irradiance conditions. Parallel differential power processing (DPP) converters are employed to address this power reduction problem, while maintaining individual PV control and maximizing output power. Two parallel DPP configurations, with and without a front-end converter, are analyzed and compared for a target battery-charging application. The DPP system without a front-end converter shows consistently high performance and operates properly over a wider range of lighting conditions. Maximum power point tracking (MPPT) algorithms are also examined for parallel DPP systems. When the MPPT parameters are properly calibrated, simulation results indicate that voltage-offset resistive control is the most effective at maximizing PV power under unbalanced lighting conditions. [ABSTRACT FROM AUTHOR]