Search

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.

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]

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]

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]

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]