Differential Power Processing Converters Research Articles

Performance analysis of optimized differential power processing converter with switched inductor using enhanced fuzzy logic control for solar photovoltaic systems

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.

A Modular Differential Power Processing Converter Design with Simplified Voltage Equalization for Photovoltaic Systems

Partial shading in series-connected photovoltaic (PV) systems poses a significant challenge as it considerably restricts the system’s output power and has a notable impact on the overall efficiency. Differential power processing (DPP) has emerged as a widely employed solution to mitigate this effect. However, implementing DPP architectures introduces challenges such as system cost, reliability, control implementation, and modularity. This research proposes a simplified voltage equalization (VE) algorithm, executed on a low-cost and modular DPP architecture using bi-directional flyback converters. Notably, under light and moderate partial shading conditions, the PV system’s output power exhibits a significant increase compared to the traditional string configuration with bypass diodes. To further optimize the system performance, a methodology adapted to the VE algorithm is suggested, minimizing the processed power while increasing overall efficiency. The proposed solutions have undergone rigorous testing through simulations and experiments. The results validate that, under moderate shading conditions, the system efficiency reaches approximately 90%.

Differential power processing architecture to increase energy harvesting of photovoltaic systems under permanent mismatch

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.

Coupling Analysis of Differential Power Processing-Based PV System and Its Decoupling Implementation of Synchronous MPPT Control

Differential power processing (DPP) is considered to be a highly competitive architecture for photovoltaic (PV) applications due to its characteristics, such as high energy efficiency and mitigation of mismatch issues. However, the complexity of coupling between DPP converters poses challenges in terms of maximum power point tracking (MPPT) in DPP-based PV systems. To address the disadvantage of the asynchronous MPPT commonly used in existing DPP topologies, which is inefficient and difficult to extend to large-scale systems, this paper presents a method that makes the application of synchronous MPPT in DPP topology feasible based on a simple and easy partial decoupling method. The innovation of the proposed decoupling method is that the dominant part of the system coupling is obtained by decomposition of the control system, to facilitate more targeted decoupling and reduce the difficulty and complexity of decoupling. Unlike other decoupling methods, the proposed approach does not become more complex with an increase in the size of the system, and thus has good scalability. In addition, the efficiency of MPPT is improved, as synchronous MPPT control can significantly reduce the MPPT time of the PV system. The results of simulations and experiments validate the effectiveness of the proposed decoupling method and the high performance of synchronous MPPT in DPP-based PV systems.

Module-to-Panel Modular Differential Power Processing Converter With Isolated DC Bus for Photovoltaic Systems Under Partial Shading

The occurrence of partial shading is known to significantly reduce the energy yield of photovoltaic (PV) panels. Differential power processing (DPP) converters can prevent negative influences of partial shading at a substring level. For PV strings comprising numerous series-connected panels, however, conventional DPP converters face various issues, such as increased converter count, poor extendibility, and cumulative power conversion loss. This article proposes a modular DPP converter with an isolated dc bus for PV strings. The proposed DPP converter is the integration of panel- and module-level DPP converters. Four panels are grouped as a module having a DPP converter, and each DPP converter can handle four panels. PV systems can be scalable with no need to redesign the DPP converter as all modules are connected through the isolated dc bus. The isolated dc bus allows the direct power transfer from unshaded high-voltage modules to shaded low-voltage ones, reducing the cumulative power conversion loss. A field testing for a three-module PV string was performed using a prototype for a four-panel 1-kW module. The experimental results demonstrated 5.6% energy yield enhancement by the proposed DPP converter.

Differential Power Processing Converter With Active Clamp Structure and Integrated Planar Transformer for Power Generation Optimization of Multiple Photovoltaic Submodules

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.

Fault Tolerant Modular Differential Power Processing Converter for Photovoltaic Systems

This paper proposes a fault tolerant modular differential power processing (DPP) converter for photovoltaic (PV) systems under partial shading conditions. The proposed DPP converter can be derived by integrating panel-level and module-level DPP converters, reducing the total switch count, and achieving a simplified circuit. The modular design of the proposed converter allows PV systems to be flexibly scaled up without redesigning converters. Furthermore, series-resonant tanks in the proposed DPP converter exhibit constant-current–constant-voltage characteristics that realize the inherent fault tolerance against short-circuit and open-circuit fault of PV panels. The prototype for a 1.5-kW PV system consisting of two modules, each comprising four panels connected in series, was built and tested. In addition to the fault tolerance, the energy yield enhancement of 19.6% was experimentally demonstrated.

Integrated differential power processing converters for PV systems

Nowadays the growth of Module Integrated Converters (MIC) concept is increasing. This concept was developed for PV applications to improve the efficiency of the converters. In this paper we propose a submodule MPP tracking algorithm to track the maximum power from the partially shaded cells. Generally, PV module have three submodules. Each submodule is formed by series connection of two strings. Here we take a different P&O algorithm for each submodule to track maximum power from the all three submodules. Each submodule will have their own DC-DC converter. In DC stage, DC-DC converters are connected in three configurations to serve sufficient energy to inverter for single phase grid connected systems.

Analysis and Design of Series Voltage Compensator for Differential Power Processing

Differential power processing (DPP) has been proven effective in many applications. This article explores a series voltage compensator (SVC) architecture for voltage regulation of DPP systems. An SVC is connected in series between the input dc bus and the DPP system to compensate for the voltage difference. It only processes a fraction of the overall power. The inclusion of an SVC changes the power flow of the DPP system and changes the loss distribution. We theoretically investigated the SVC power rating and the additional power conversion stress that SVC brings to the DPP converter. Accordingly, we identified the operation range where an SVC is more attractive than a conventional DPP pre-regulation converter that has to process the full power. Our analysis provides insights into system design and control strategy of SVC-DPP topologies. To validate the principles of SVC, a buck SVC is designed and applied to a ten-port DPP converter. The buck SVC can efficiently convert an input voltage ranging from 50 V to 65 V into a regulated 50 V for the DPP system. The size of the SVC is only 20% of the DPP converter, and the peak efficiency of the SVC-DPP system achieves 98.8%.

Differential Power Processing Converter with an Integrated Transformer and Secondary Switch for Power Generation Optimization of Multiple Photovoltaic Submodules

In recent years, to increase the fuel efficiency of environment-friendly vehicles, a large volume of research is ongoing regarding applying photovoltaic (PV) systems. However, in PV systems, a power imbalance between submodules is common due to shading or pollution, and this degrades the power generation efficiency of the system. To solve this problem, various differential power processing (DPP) converters have been developed. In order to adopt the DPP converter to environment-friendly vehicles, the DPP converter must have a small volume, high efficiency, and high price competitiveness. In this regard, we propose a DPP converter with a single multi-winding transformer by integrating multiple transformers and secondary sides of the conventional flyback DPP converter. Since the proposed DPP converter can be applied to battery balancing circuits as well as photovoltaic systems, the proposed circuit is a valuable converter. In the PV system, the maximum output power of each submodule is 60 W, and the total PV system is 240 W by connecting four submodules in series. To verify the validity of the proposed DPP converter, a prototype with 8 V input and 60 W/30 V output specification was built and tested, and the effectiveness of the proposed converter is supported by the experimental results.

Panel-to-Substring PWM Differential Power Processing Converter and Its Maximum Power Point Tracking Technique for Solar Roof of Plug-In Electric Vehicles

In photovoltaic (PV) panels comprising multiple substrings, a mismatch in substring characteristics is known to reduce energy yield significantly. Substring characteristics in solar roofs of plug-in hybrid vehicles (PHVs) are always mismatched to some extent due to the curved surface of the panel. This paper proposes a PWM differential power processing (DPP) converter based on a panel-to-substring power redistribution architecture and its dual maximum power point tracking (MPPT) control technique for PHEVs’ solar roofs. Depending on the degree of characteristic mismatch, the proposed DPP converter adjusts its output current to maximize the energy yield of the panel. With the proposed dual MPPT control, a duty cycle <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d_{DPP}$ </tex-math></inline-formula> of the DPP converter is manipulated to optimize the panel characteristic while an external boost converter manipulates its duty cycle <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D_{boost}$ </tex-math></inline-formula> to track an MPP of the panel. A prototype for 180-W solar roofs comprising seven substrings was built, and laboratory testing was performed using solar array simulators to emulate characteristic mismatch conditions. Thanks to the dual MPPT control technique, the proposed DPP converter operated with the optimal <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d_{DPP}$ </tex-math></inline-formula> while the external boost converter tracked the MPP by manipulating <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D_{boost}$ </tex-math></inline-formula> , realizing the enhanced energy yield.

Switched Capacitor-Based Modular Differential Power Processing Architecture for Large-Scale Photovoltaic Systems Under Partial Shading

Differential power processing (DPP) converters have been developed for photovoltaic (PV) panels to preclude energy yield reduction due to partial shading. In large-scale PV systems comprising numerous series-connected panels, DPP converters with good modularity are preferable because the number of series-connected panels varies depending on applications. This paper proposes a switched capacitor converter (SCC)-based modular DPP architecture for large-scale PV systems. Four panels are grouped as a module, each having a panel-level DPP converter, and modules are connected in series to form a string. The design of the panel-level DPP converter is fixed while the system can be arbitrarily extended by stacking modules, achieving good modularity. Adjacent panel-level DPP converters are dc-coupled, by which modules can be connected using long cables, mitigating installation limitations. The experimental results of the laboratory and field testing demonstrated the enhanced power generation by 10%20%, depending on shading conditions.

Power-Rating Balance Control and Reliability Enhancement in Mismatched Photovoltaic Differential Power Processing Systems

With the increase of the component number, the power stress distribution among differential power processing (DPP) converters, control implementation, system cost, and reliability become the most challenging issues for a practical photovoltaic (PV) DPP system. This article introduces an improved power-rating balance (IPRB) control for the PV-to-bus based DPP architecture that ensures each PV submodule operate at its true maximum power point (MPP) while achieving more balanced power stress distribution and higher reliability. Specifically, a submodule-level finite-state-machine-based MPP tracking is implemented to guarantee always maximum power yield, whereas a string-level power-rating balancing (PRB) control is adopted to balance the unit-maximum proceeded power by DPP converters based on the built power flow model with respect to the string current. A comprehensive comparison of advanced control strategies for PV-to-bus DPP architectures, including least power point tracking, voltage equalization (VE) based PRB control, and the proposed IPRB, has been carried out with the mission-profile-based reliability assessment under different partial shading scenarios. Component-failure-rate-based reliability analysis shows that the PV-to-bus DPP architecture with the proposed IPRB control can significantly improve the system reliability. Main simulation and experimental evaluations are carried out to verify the effectiveness of the proposed control.

Analysis of the PV-to-PV architecture with a bidirectional Buck-Boost converter under shading conditions

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.

Fault-tolerant strategy without redundant switches for PV systems based on differential power processing converters

Considering the failure risk and cost-effectiveness of photovoltaic (PV) systems with high granularity maximum power point tracking (MPPT), a fault-tolerant strategy without redundant switches is proposed for the PV system based on differential power processing (DPP) converters. This fault-tolerant strategy optimizes the output power of the PV system under different converter fault conditions by adjusting the coordinated operation of the DPP converter and the centralized converter. Compared to previous methods, in the case of hardware cost advantage, the proposed fault-tolerant strategy achieves the stable operation of the PV system after the converter failure and completes the targeted power optimization of all PV modules. The PV system with the proposed fault-tolerant strategy operates in three modes: distributed MPPT (DMPPT) mode, the coexistence of DMPPT and centralized MPPT (CMPPT) mode, and CMPPT mode. The PV system operates in the DMPPT mode when no switch failure occurs in the DPP converter. In the latter two post-fault operating modes, this paper proposes a simple fault-tolerant method to remove the faulty DPP converter and adjust the MPPT coverage of the centralized converter to recover the power loss caused by the fault. The experimental results validate the proposed fault-tolerant strategy.

Energy Yield Enhancement by Switched Capacitor Converter-Based Differential Power Processing Converter Utilizing Diffusion Capacitance of Curved Photovoltaic Panels

Energy Yield Enhancement by Switched Capacitor Converter-Based Differential Power Processing Converter Utilizing Diffusion Capacitance of Curved Photovoltaic Panels

A Simple Mismatch Mitigating Partial Power Processing Converter for Solar PV Modules

Partial shading affects the energy harvested from photovoltaic (PV) modules, leading to a mismatch in PV systems and causing energy losses. For this purpose, differential power processing (DPP) converters are the emerging power electronic-based topologies used to address the mismatch issues. Normally, PV modules are connected in series and DPP converters are used to extract the power from these PV modules by only processing the fraction of power called mismatched power. In this work, a switched-capacitor-inductor (SCL)-based DPP converter is presented, which mitigates the non-ideal conditions in solar PV systems. A proposed SCL-based DPP technique utilizes a simple control strategy to extract the maximum power from the partially shaded PV modules by only processing a fraction of the power. Furthermore, an operational principle and loss analysis for the proposed converter is presented. The proposed topology is examined and compared with the traditional bypass diode technique through simulations and experimental tests. The efficiency of the proposed DPP is validated by the experiment and simulation. The results demonstrate the performance in terms of higher energy yield without bypassing the low-producing PV module by using a simple control. The results indicate that achieved efficiency is higher than 98% under severe mismatch (higher than 50%).

Panel-to-Substring Differential Power Processing Converter With Embedded Electrical Diagnosis Capability for Photovoltaic Panels Under Partial Shading

Various kinds of differential power processing (DPP) converters have been developed to improve the energy yield of partially-shaded photovoltaic (PV) panels by precluding partial shading issues, such as the reduction in power generation and the occurrence of multiple maximum power points. Meanwhile, PV systems require fault diagnosis tools to detect premature deterioration and malfunctions that lead to a reduction in power generation of the system as a whole and, in the worst case, hazardous situations, such as a fire. This article proposes a novel DPP converter as well as an electrical diagnosis technique using the DPP converter. The proposed DPP converter not only addresses the partial shading issues but also provides the electrical diagnosis capability. In the diagnosis mode, the DPP converter injects ac currents to a panel, and an ac impedance of the panel can be calculated from the voltage response to the injected ac currents. The detailed operation analysis and experimental verification tests using a prototype were performed. The results demonstrated the improved power yield from partially shaded PV panels and the electrical diagnosis capability of the proposed DPP converter.

Analysis, Design, and Implementation of a Differential Power Processing DMPPT With Multiple Buck–Boost Choppers for Photovoltaic Module

Submodule mismatch has become the major cause of losses in the photovoltaic (PV) power generation system, which has been an important factor restricting the development of PV technology. Differential power processing (DPP) architecture is increasingly employed in PV distributed MPPT (DMPPT) due to its low processed power. In order to improve the PV utilization efficiency, minimize the power loss and reduce the system cost, a novel scheme based on DPP is introduced in this article. The proposed DPP converter is composed of multiple buck-boost choppers, and a multidimensional perturb and observe (MPO) algorithm is proposed to achieve true DMPPT through correcting the voltage of each submodule to its voltage at the maximum power point by using a single current sensor. A prototype with multiple buck-boost choppers for 36 V/200 W PV module is designed and built to verify the operating principle and evaluate the performance of the proposed DPP converter and DMPPT strategy, and the experimental results show that the prototype is low-cost and effectively improves system efficiency.

Segmented Differential Power Processing Converter Unit and Control Algorithm for Photovoltaic Systems

Differential power processing (DPP) for photovoltaic (PV) systems can achieve high system efficiency and maintain maximum power production even under mismatched conditions. However, DPP converters applied to large-scale systems have challenges of complicated installation and high voltage ratings. The segmented DPP structure is introduced as a modular approach that utilizes groups of bidirectional DPP flyback converters to maximize PV power generation while minimizing converter power loss. Groups of four DPP converters are combined into a segmented DPP unit with maximum power point tracking (MPPT) control to maximize output power of the unit. The segmented DPP system and control algorithm are verified through simulation and hardware experimentation. Simulation results verify the effectiveness of the control algorithm with multiple segmented DPP units interacting with a typical inverter employing MPPT. Experimental results verify that system efficiency of the segmented DPP unit reaches 96.4% in even lighting conditions, reaches 92.7% in severe partial shading conditions, and shows an increase of up to 14.8% in uneven lighting conditions compared to an equivalent series-connected PV system.