Showing papers on "Power optimizer published in 2014"
TL;DR: A decentralized power sharing method is proposed in order to eliminate the need for any communication between DGs or microgrids and the performance of the proposed power control strategy is validated for different operating conditions, using simulation studies in the PSCAD/EMTDC software environment.
Abstract: Hybrid AC/DC microgrids have been planned for the better interconnection of different distributed generation systems (DG) to the power grid, and exploiting the prominent features of both ac and dc microgrids. Connecting these microgrids requires an interlinking AC/DC converter (IC) with a proper power management and control strategy. During the islanding operation of the hybrid AC/DC microgrid, the IC is intended to take the role of supplier to one microgrid and at the same time acts as a load to the other microgrid and the power management system should be able to share the power demand between the existing AC and dc sources in both microgrids. This paper considers the power flow control and management issues amongst multiple sources dispersed throughout both ac and dc microgrids. The paper proposes a decentralized power sharing method in order to eliminate the need for any communication between DGs or microgrids. This hybrid microgrid architecture allows different ac or dc loads and sources to be flexibly located in order to decrease the required power conversions stages and hence the system cost and efficiency. The performance of the proposed power control strategy is validated for different operating conditions, using simulation studies in the PSCAD/EMTDC software environment.
508 citations
TL;DR: In this paper, the authors proposed a dc-DC-DC converter to realize power quality independence from the utility mains by merging renewable energy sources (RESs) into dedicated dc distribution architectures through corresponding dc-dc converters.
Abstract: Current trends indicate that worldwide electricity distribution networks are experiencing a transformation toward direct current (dc) at both the generation and consumption level. This tendency is powered by the outburst of various electronic loads and, at the same time, the struggle to meet the lofty goals for the sharing of renewable energy sources (RESs) in satisfying total demand. RESs operate either natively at dc or have a dc link in the heart of their power electronic interface, whereas the end-point connection of electronic loads, batteries, and fuel cells is exclusively dc. Therefore, merging these devices into dedicated dc distribution architectures through corresponding dc?dc converters is an attractive option not only in terms of enhancing efficiency because of reduction of conversion steps but also for realizing power quality independence from the utility mains. These kinds of systems generally provide improved reliability in comparison to their alternating current (ac) counterparts since the number of active elements in dc?dc power electronic devices is smaller than in dc-ac converters. Control design in dc systems is also significantly simpler since there are no reactive and harmonic power flows or problems with synchronization.
294 citations
TL;DR: In this paper, a new medium voltage power converter topology using a diode rectifier, three-level boost (TLB) converter, and neutral-point-clamped (NPC) inverter is proposed for a high-power permanent magnet synchronous generator-based wind energy conversion system.
Abstract: In this paper, a new medium voltage power converter topology using a diode rectifier, three-level boost (TLB) converter, and neutral-point-clamped (NPC) inverter is proposed for a high-power permanent magnet synchronous generator-based wind energy conversion system. The generator-side TLB converter performs the maximum power point tracking and balancing of dc-link capacitor voltages, while the grid-side NPC inverter regulates the net dc-bus voltage and reactive power to the grid. A significant improvement in the grid power quality is accomplished as the NPC inverter no longer controls the dc-link neutral point voltage. A model predictive strategy is proposed to control the complete system where the discrete-time models of the proposed power electronic converters are used to predict the future behavior of control variables. These predictions are evaluated using two independent cost functions, and the switching states which minimize these cost functions are selected and applied to the generator- and grid-side converters directly. In order to comply with the high-power application, the switching frequencies of the TLB converter and NPC inverter are minimized and maintained below 1.5 and 1 kHz, respectively. The proposed topology and control strategy are verified through MATLAB simulations on a 3-MW/3000-V/577-A system and dSPACE DS1103-based experiments on 3.6-kW/208-V/10-A prototype.
277 citations
TL;DR: In this article, a fuzzy logic controller (FLC)-based single-ended primary-induction converter (SEPIC) was proposed for maximum power point tracking (MPPT) operation of a photovoltaic (PV) system.
Abstract: This paper presents a fuzzy logic controller (FLC)-based single-ended primary-inductor converter (SEPIC) for maximum power point tracking (MPPT) operation of a photovoltaic (PV) system. The FLC proposed presents that the convergent distribution of the membership function offers faster response than the symmetrically distributed membership functions. The fuzzy controller for the SEPIC MPPT scheme shows high precision in current transition and keeps the voltage without any changes, in the variable-load case, represented in small steady-state error and small overshoot. The proposed scheme ensures optimal use of PV array and proves its efficacy in variable load conditions, unity, and lagging power factor at the inverter output (load) side. The real-time implementation of the MPPT SEPIC converter is done by a digital signal processor (DSP), i.e., TMS320F28335. The performance of the converter is tested in both simulation and experiment at different operating conditions. The performance of the proposed FLC-based MPPT operation of SEPIC converter is compared to that of the conventional proportional-integral (PI)-based SEPIC converter. The results show that the proposed FLC-based MPPT scheme for SEPIC can accurately track the reference signal and transfer power around 4.8% more than the conventional PI-based system.
265 citations
TL;DR: In this paper, the frequency stability challenges at high and ultra-high wind penetrations were examined in the All-Island system (AIS) and the impact of both largest infeed loss and network fault induced wind turbine active power dips was examined.
Abstract: Synchronous island power systems, such as the combined Ireland and Northern Ireland power system, are facing increasing penetrations of renewable generation. As part of a wider suite of studies, performed in conjunction with the transmission system operators (TSOs) of the All-Island system (AIS), the frequency stability challenges at high and ultra-high wind penetrations were examined. The impact of both largest infeed loss and network fault induced wind turbine active power dips was examined: the latter contingency potentially representing a fundamental change in frequency stability risk. A system non-synchronous penetration (SNSP) ratio was defined to help identify system operational limits. A wide range of system conditions were studied, with results showing that measures such as altering ROCOF protection and enabling emulated inertia measures were most effective in reducing the frequency stability risk of a future Ireland system.
253 citations
TL;DR: Different concepts of PV panel integrated DC-DC converters are presented, comparative evaluation is given and the converter design process is shown for the buck-boost converter which is identified as the best suited concept.
Abstract: The strings of photovoltaic panels have a significantly reduced power output when mismatch between the panels occurs, as, e.g., caused by partial shading. With mismatch, either the panel-integrated diodes are bypassing the shaded panels if the string is operated at the current level of the unshaded panels, or some power of the unshaded panels is lost if the string current is reduced to the level of the shaded panels. With the implementation of dc-dc converters on panel level, the maximum available power can be extracted from each panel regardless of any mismatch. In this paper, different concepts of PV panel-integrated dc-dc converters are presented and their suitability for panel integration is evaluated. The buck-boost converter is identified as the most promising concept and an efficiency/power density ( η- ρ) Pareto optimization of this topology is shown. Based on the optimization results, two 275 W converter prototypes with either Silicon MOSFETs with a switching frequency of 100 kHz or gallium nitride FETs with a switching frequency of 400 kHz are designed for an input voltage range of 15 to 45 V and an output voltage range of 10 to 100 V. The theoretical considerations are verified by efficiency measurements which are compared to the characteristics of a commercial panel-integrated converter.
251 citations
TL;DR: In this paper, the problem posed by complex, nonlinear controllers for power system load flows employing multi-terminal voltage source converter (VSC) HVDC systems is addressed.
Abstract: This paper addresses the problem posed by complex, nonlinear controllers for power system load flows employing multi-terminal voltage source converter (VSC) HVDC systems. More realistic dc grid control strategies can thus be carefully considered in power flow analysis of ac/dc grids. Power flow methods for multi-terminal VSC-HVDC (MTDC) systems are analyzed for different types of dc voltage control techniques and the weaknesses of present methods are addressed. As distributed voltage control is likely to be adopted by practical dc grids, a new generalized algorithm is proposed to solve the power flow problems with various nonlinear voltage droops, and the method to incorporate this algorithm with ac power flow models is also developed. With five sets of voltage characteristics implemented, the proposed scheme is applied to a five-terminal test system and shows satisfactory performance. For a range of wind power variations and converter outages, post-contingency behaviors of the system under the five control scenarios are examined. The impact of these controls on the power flow solutions is assessed.
251 citations
TL;DR: In this article, an aggregated model of renewable wind and solar power generation forecast is proposed to support the quantification of the operational reserve for day-ahead and real-time scheduling.
Abstract: Operational controls are designed to support the integration of wind and solar power within microgrids. An aggregated model of renewable wind and solar power generation forecast is proposed to support the quantification of the operational reserve for day-ahead and real-time scheduling. Then, a droop control for power electronic converters connected to battery storage is developed and tested. Compared with the existing droop controls, it is distinguished in that the droop curves are set as a function of the storage state-of-charge (SOC) and can become asymmetric. The adaptation of the slopes ensures that the power output supports the terminal voltage while at the same keeping the SOC within a target range of desired operational reserve. This is shown to maintain the equilibrium of the microgrid's real-time supply and demand. The controls are implemented for the special case of a dc microgrid that is vertically integrated within a high-rise host building of an urban area. Previously untapped wind and solar power are harvested on the roof and sides of a tower, thereby supporting delivery to electric vehicles on the ground. The microgrid vertically integrates with the host building without creating a large footprint.
248 citations
TL;DR: This paper presents an optimization technique base on a Multi-Objective Genetic Algorithm (MOGA) which uses high temporal resolution insolation data taken at 10 seconds data rate instead of more commonly used hourly data rate to determine the baseline system cost necessary to meet the load requirements.
Abstract: Renewable energy sources continues to gain popularity. However, two major limitations exist that prevent widespread adoption: availability of the electricity generated and the cost of the equipment. Distributed generation, (DG) grid-tied photovoltaic-wind hybrid systems with centralized battery back-up, can help mitigate the variability of the renewable energy resource. The downside, however, is the cost of the equipment needed to create such a system. Thus, optimization of generation and storage in light of capital cost and variability mitigation is imperative to the financial feasibility of DC microgrid systems. PV and wind generation are both time dependent and variable but are highly correlated, which make them ideal for a dual-sourced hybrid system. This paper presents an optimization technique base on a Multi-Objective Genetic Algorithm (MOGA) which uses high temporal resolution insolation data taken at 10 seconds data rate instead of more commonly used hourly data rate. The proposed methodology employs a techno-economic approach to determine the system design optimized by considering multiple criteria including size, cost, and availability. The result is the baseline system cost necessary to meet the load requirements and which can also be used to monetize ancillary services that the smart DC microgrid can provide to the utility at the point of common coupling (PCC) such as voltage regulation. The hybrid smart DC microgrid community system optimized using high-temporal resolution data is compared to a system optimized using lower-rate temporal data to examine the effect of the temporal sampling of the renewable energy resource.
225 citations
TL;DR: In this paper, a slidingmode duty-ratio controller (SMDC) is proposed for dc/dc buck converters with constant power loads, which is able to stabilize the dc power systems over the entire operating range in the presence of significant variations in the load power and input voltage.
Abstract: Incorporating a medium-voltage dc (MVDC) integrated power system is a goal for future surface combatants and submarines. In an MVDC shipboard power system, dc/dc converters are commonly employed to supply constant power to electric loads. These constant power loads have a characteristic of negative incremental impedance, which may cause system instability during disturbances if the system is not properly controlled. This paper proposes a sliding-mode duty-ratio controller (SMDC) for dc/dc buck converters with constant power loads. The proposed SMDC is able to stabilize the dc power systems over the entire operating range in the presence of significant variations in the load power and input voltage. The proposed SMDC is validated by both simulation studies in MATLAB/Simulink and experiments for stabilizing a dc/dc buck converter with constant power loads. Simulation studies for an MVDC shipboard power system with constant power loads for different operating conditions with significant variations in the load power and supply voltage are also provided to further demonstrate the effectiveness of the proposed SMDC.
225 citations
TL;DR: In this paper, a control strategy is proposed for a DC-MG to achieve perfect power sharing considering the effects of unequal line resistances, and the state of charge of the batteries is also considered in the power sharing strategy.
Abstract: DC microgrids (DC-MGs) are becoming popular as an effective means to integrate various renewable energy resources. Conventionally, the droop control is adopted as a decentralized control strategy for proper power sharing without using any communication link. However, the conventional droop control often deteriorates due to the effects of unequal line resistances. In this paper, a control strategy is proposed for a DC-MG to achieve perfect power sharing considering the effects of line resistances. The DC-MG under study consists of a photovoltaic system, two energy storage systems, a grid-connected converter system, and dc loads. The control strategy of the converters is addressed under various operation modes. To obtain prolonged and reliable operation of the DC-MG, the state of charge of the batteries is also considered in the power sharing strategy. Simulation and experimental results are provided to verify the effectiveness and validity of the proposed method.
TL;DR: In this article, the authors examined dynamic operation and control strategies for a microgrid hybrid wind-PV (photovoltaic) and fuel cell-based power supply system, which consists of the PV power, wind power, FC power, SVC (static var compensator) and an intelligent power controller.
TL;DR: A novel cascaded boost-buck dc-dc converter is designed to provide the optimal impedance matching in WPT system for various loads including resistive load, ultracapacitors, and batteries.
Abstract: Wireless power transfer (WPT) has attracted an ever increasing interest from both industry and academics over the past few years. Its applications vary from small power devices such as mobile phones and tablets to high power electric vehicles and from small transfer distance of centimeters to large distance of tens of centimeters. In order to achieve a high-efficiency WPT system, each circuit should function at a high efficiency along with the proper impedance matching techniques to minimize the power reflection due to the impedance mismatch. This paper proposes an analysis on the system efficiency to determine the optimal impedance requirement for coils, rectifier, and dc-dc converter. A novel cascaded boost-buck dc-dc converter is designed to provide the optimal impedance matching in WPT system for various loads including resistive load, ultracapacitors, and batteries. The proposed 13.56-MHz WPT system can achieve a total system efficiency over 70% in experiment.
TL;DR: In this article, a model predictive control-based maximum power point tracking (MPPT) and model predictive controller-based droop current regulator is presented to interface PV in smart dc distribution systems.
Abstract: In a dc distribution system, where multiple power sources supply a common bus, current sharing is an important issue. When renewable energy resources are considered, such as photovoltaic (PV), dc/dc converters are needed to decouple the source voltage, which can vary due to operating conditions and maximum power point tracking (MPPT), from the dc bus voltage. Since different sources may have different power delivery capacities that may vary with time, coordination of the interface to the bus is of paramount importance to ensure reliable system operation. Further, since these sources are most likely distributed throughout the system, distributed controls are needed to ensure a robust and fault tolerant control system. This paper presents a model predictive control-based MPPT and model predictive control-based droop current regulator to interface PV in smart dc distribution systems. Back-to-back dc/dc converters control both the input current from the PV module and the droop characteristic of the output current injected into the distribution bus. The predictive controller speeds up both of the control loops, since it predicts and corrects error before the switching signal is applied to the respective converter.
TL;DR: In this paper, an adaptive neuro-fuzzy inference system (ANFIS) based controller for variable-speed operation of a wind turbine was proposed to improve the wind energy available in an erratic wind speed regime.
TL;DR: In this article, a new method has been presented to track the global maximum power point (GMPP) of PV arrays under partial shading conditions, which has the advantages of determining whether partial shading is present, calculating the number of peaks on P-V curves, and predicting the locations of GMPP and LMPP.
Abstract: Maximum power point tracking (MPPT) is an integral part of a system of energy conversion using photovoltaic (PV) arrays. The power-voltage characteristic of PV arrays operating under partial shading conditions exhibits multiple local maximum power points (LMPPs). In this paper, a new method has been presented to track the global maximum power point (GMPP) of PV. Compared with the past proposed global MPPT techniques, the method proposed in this paper has the advantages of determining whether partial shading is present, calculating the number of peaks on P – V curves, and predicting the locations of GMPP and LMPP. The new method can quickly find GMPP, and avoid much energy loss due to blind scan. The experimental results verify that the proposed method guarantees convergence to the global MPP under partial shading conditions.
TL;DR: In this article, the authors proposed a new converter for photovoltaic (PV) water pumping or treatment systems without the use of chemical storage elements, such as batteries, to achieve a more efficient, reliable, maintenance-free, and cheaper solution than the standard ones that use dc motors or lowvoltage synchronous motors.
Abstract: This paper proposes a new converter for photovoltaic (PV) water pumping or treatment systems without the use of chemical storage elements, such as batteries. The converter is designed to drive a three-phase induction motor directly from PV energy. The use of a three-phase induction motor presents a better solution to the commercial dc motor water pumping system. The development is oriented to achieve a more efficient, reliable, maintenance-free, and cheaper solution than the standard ones that use dc motors or low-voltage synchronous motors. The developed system is based on a current-fed multiresonant converter also known as resonant two-inductor boost converter (TIBC) and a full-bridge three-phase voltage source inverter (VSI). The classic topology of the TIBC has features like high voltage gain and low input current ripple. In this paper, it is further improved with the use of a nonisolated recovery snubber along with a hysteresis controller and the use of a constant duty cycle control to improve its efficiency. Experimental results show a peak efficiency of 91% at a rated power of 210 W for the dc/dc converter plus the three-phase VSI and a peak efficiency of 93.64% just for the dc/dc converter. The system is expected to have a high lifetime due to the inexistence of electrolytic capacitors, and the total cost of the converter is below 0.43 U$/Wp. As a result, the system is a promising solution to be used in isolated locations and to deliver water to poor communities.
TL;DR: An integrated control scheme for vehicle-to-grid (V2G) operation in the distribution grid with renewable energy sources and an experimental platform is incorporated into the proposed integrated energy management to demonstrate the instantaneous response of EV battery storage.
Abstract: This paper presents an integrated control scheme for vehicle-to-grid (V2G) operation in the distribution grid with renewable energy sources. A hierarchical framework is proposed for V2G applications, and the mathematical models are built for both smart charging and V2G operation with distribution grid constraints. V2G power is regulated to minimize the total operating cost (TOC) while providing frequency regulation. The simulation results verify the control algorithm in coordinating distributed electric vehicle (EV) aggregations with the varying wind power and daily load. For V2G dynamic regulation, EVs connected in close proximity to wind power generators can locally compensate for the wind fluctuation with fast response and, hence, smooth out the power fluctuation at the bus having wind power generators and EVs. Each individual EV is strategically assigned to implement the simulated control algorithm through a bidirectional converter. An experimental platform is incorporated into the proposed integrated energy management to demonstrate the instantaneous response of EV battery storage.
TL;DR: The proposed multi- inputs non-isolated DC/DC converter with high-voltage transfer gain benefits from various advantages such as reduced semiconductor current stress, no limitation for switching duty cycle and wide control range of different input powers.
Abstract: A new multi-input non-isolated DC/DC converter with high-voltage transfer gain is proposed in this study. The presented converter consists of the conventional buck–boost and boost converters. All the stages except the last stage are buck–boost converters. The last stage is the conventional boost converter. The proposed multi-input high-voltage gain converter benefits from various advantages such as reduced semiconductor current stress, no limitation for switching duty cycle and wide control range of different input powers. The presented converter can even operate when one or some power input fail to provide energy to the load. The steady-state operation and dynamic modelling of the suggested converter are analysed thoroughly. Experimental results are also provided to verify the feasibility of the presented converter.
TL;DR: A predictive control scheme is proposed for the low-voltage ride-through (LVRT) enhancement of direct-driven permanent-magnet-synchronous-generator-based megawatt-level wind turbines to store the surplus energy during the grid voltage dips.
Abstract: In this paper, a predictive control scheme is proposed for the low-voltage ride-through (LVRT) enhancement of direct-driven permanent-magnet-synchronous-generator-based megawatt-level wind turbines. The proposed method uses the turbine-generator rotor inertia to store the surplus energy during the grid voltage dips. The power conversion system is realized using a three-phase diode-bridge rectifier, a three-level-boost converter, and a neutral-point-clamped (NPC) inverter. The wind turbine requirements, such as maximum power point tracking, net dc-bus voltage control, balancing of the dc capacitor voltages, and reactive power generation, are modeled as the reference control variables. The generator- and grid-side cost functions are defined to deal with these control objectives. During each sampling interval, the control goals are achieved based on the minimization of cost functions. The coordination of boost and NPC converters and the exchange of reference control variables during normal and LVRT operation are formulated such that the power converters operate in a safe mode while meeting the grid code requirements. Simulation and experimental results are presented to validate the proposed strategy.
TL;DR: A hybrid microgrid structure for a grid connected microgrid with DC connection at back to back (B2B) converters with fixed power references or decentralized power distribution in AC/DC sides is proposed and validated with simulations in PSCAD.
Abstract: The necessity of an AC or DC microgrid is governed by available micro sources and connected loads. A hybrid structure can ensure a sustainable configuration blending both the forms. In this paper, a hybrid microgrid structure for a grid connected microgrid with DC connection at back to back (B2B) converters is proposed. While a B2B connection between two AC systems could bestow a reliable, isolated and efficient coupling, an extra DC bus connection can facilitate use of the DC micro sources. The DC bus can supply the local DC loads and can also trade part of the power with the AC grids. The voltage support at the DC link (of the B2B converters) can be used for the DC bus formation. Different power management strategies with fixed power references or decentralized power distribution in AC/DC sides are proposed and validated with simulations in PSCAD.
TL;DR: In this paper, the authors proposed a new isolated multiport dc-dc converter for simultaneous power management of multiple renewable energy sources, which can be of different types and capacities, using one controllable switch in each port to which a source is connected.
Abstract: This paper proposes a new isolated multiport dc-dc converter for simultaneous power management of multiple renewable energy sources, which can be of different types and capacities. The proposed dc-dc converter only uses one controllable switch in each port to which a source is connected. Therefore, it has the advantages of simple topology and minimum number of power switches. A general topology of the proposed converter is first introduced. Its principle and operation are then analyzed. The proposed converter is applied for simultaneous maximum power point tracking (MPPT) control of a wind/solar hybrid generation system consisting of one wind turbine generator (WTG) and two different photovoltaic (PV) panels. The experimental results are provided to validate the effectiveness of using the proposed converter to achieve MPPT simultaneously for the WTG and both PV panels.
TL;DR: A new methodology for probabilistic optimal power flow (P-OPF) studies for such problems by modifying the 2PEM, which cannot handle correlated uncertain variables but has been equipped with this ability.
Abstract: As a matter of course, the unprecedented ascending penetration of distributed energy resources (DERs), mainly harvesting renewable energies (REs), is concomitant with environmentally friendly concerns. This type of energy resources are innately uncertain and bring about more uncertainties in the power system, consequently, necessitates probabilistic analyses of the system performance. Moreover, the uncertain parameters may have a considerable level of correlation to each other, in addition to their uncertainties. The two point estimation method (2PEM) is recognized as an appropriate probabilistic method in small scale or even medium scale problems. This paper develops a new methodology for probabilistic optimal power flow (P-OPF) studies for such problems by modifying the 2PEM. The original 2PEM cannot handle correlated uncertain variables but the proposed method has been equipped with this ability. In order to justify the impressiveness of the method, two case studies namely the Wood & Woollenberg 6-bus and the Mathpower 30-bus test systems are examined using the proposed method, then, the obtained results are compared against the Monte Carlo simulation (MCS) results. Comparison of the results justifies the effectiveness of the method in the respected area with regards to both accuracy and execution time criteria.
TL;DR: It is pointed out that when the minimum nonactive power loss is achieved, zero-voltage soft switching can be naturally fulfilled and the optimal phase-shift pair obtained by the proposed method can keep low values of both root mean square (RMS) current and circulating power.
Abstract: Originated from analyzing nonactive power loss, a novel optimization method and modulation solution for bidirectional isolated dual-active-bridge (DAB) dc-dc converters are proposed in order to achieve high efficiency in a wide operating range. A comprehensive nonactive power loss model is developed, including both the nonactive components delivered back to the source and from the load. This paper points out that when the minimum nonactive power loss is achieved, zero-voltage soft switching can be naturally fulfilled. The optimal phase-shift pair obtained by the proposed method can keep low values of both root mean square (RMS) current and circulating power. Rather than using ideal power flow analysis, the nonactive power loss model directly embodies practical nonideal factors, including device voltage drops. Based on the analysis, an extended dual phase shift is proposed, and different operation cases are analyzed with comparison of performance indices. Experimental tests verify the theoretical analysis and show effectiveness of the proposed approach to achieve nonactive power loss minimization and efficiency improvement.
TL;DR: In this paper, an adaptive neuro-fuzzy inference system (ANFIS) based maximum power point tracker for PV module has been presented, where the duty cycle of DC-DC boost converter is modified with the help of the ANFIS reference model, so that maximum power is transferred to load.
Abstract: Solar energy, at the present time is considered as an important source in electricity generation. Electricity from the solar energy can be generated using solar photovoltaic (PV) modules. The maximization of solar power extracted from a PV module is of special concern as its efficiency is very low. The output power of a PV module is highly dependent on the geographical location and weather conditions such as solar irradiation, shading and temperature. To obtain maximum power from PV module, photovoltaic power system usually requires maximum power point tracking (MPPT) controller. In this paper, an adaptive neuro-fuzzy inference system (ANFIS) based maximum power point tracker for PV module has been presented. To extract maximum power, a DC–DC boost converter is connected between the PV module and the load. The duty cycle of DC–DC boost converter is modified with the help of the ANFIS reference model, so that maximum power is transferred to load. Due to the complexity of the tracker mechanism and non-linear nature of photovoltaic system, the artificial intelligence based technique, especially the ANFIS method, is used in this paper. In order to observe the maximum available power of PV module, the ANFIS reference model directly takes in operating temperature and irradiance level as input. The response of proposed ANFIS based control system shows accuracy and fast response. The simulation result reveals that the maximum power point is tracked satisfactorily for varying irradiance and temperature of PV module. Simulation results are provided to validate the concept.
TL;DR: A fully integrated energy harvester that maintains >35% end-to-end efficiency when harvesting from a 0.84 mm 2 solar cell in low light condition of 260 lux, converting 7 nW input power from 250 mV to 4 V is presented.
Abstract: This paper presents a fully integrated energy harvester that maintains >35% end-to-end efficiency when harvesting from a 0.84 mm 2
solar cell in low light condition of 260 lux, converting 7 nW input power from 250 mV to 4 V. Newly proposed self-oscillating switched-capacitor (SC) DC-DC voltage doublers are cascaded to form a complete harvester, with configurable overall conversion ratio from 9× to 23×. In each voltage doubler, the oscillator is completely internalized within the SC network, eliminating clock generation and level shifting power overheads. A single doubler has >70% measured efficiency across 1 nA to 0.35 mA output current ( >10 5
range) with low idle power consumption of 170 pW. In the harvester, each doubler has independent frequency modulation to maintain its optimum conversion efficiency, enabling optimization of harvester overall conversion efficiency. A leakage-based delay element provides energy-efficient frequency control over a wide range, enabling low idle power consumption and a wide load range with optimum conversion efficiency. The harvester delivers 5 nW-5 μW output power with >40% efficiency and has an idle power consumption 3 nW, in test chip fabricated in 0.18 μm CMOS technology.
TL;DR: The essence of the proposed concept lies in the selection of an appropriate power limit for the CPG control to achieve an improved thermal performance and an increased utilization factor of PV inverters, and thus, to cater for a higher penetration level of PV systems with intermittent nature.
Abstract: This letter proposes a hybrid power control concept for grid-connected photovoltaic (PV) inverters. The control strategy is based on either a maximum power point tracking control or a constant power generation (CPG) control depending on the instantaneous available power from the PV panels. The essence of the proposed concept lies in the selection of an appropriate power limit for the CPG control to achieve an improved thermal performance and an increased utilization factor of PV inverters, and thus, to cater for a higher penetration level of PV systems with intermittent nature. A case study on a single-phase PV inverter under yearly operation is presented with analyses of the thermal loading, lifetime, and annual energy yield. It has revealed the trade-off factors to select the power limit and also verified the feasibility and the effectiveness of the proposed control concept.
TL;DR: The superiority of the control technique over the classical tracking methods is analytically demonstrated through the procedure proposed in this paper and the analytical results have been validated by means of both simulations and experiments.
Abstract: In this paper, the procedure for designing a sliding-mode controller for maximum power point tracking photovoltaic (PV) applications is proposed. It is applied to a single-ended primary inductor converter, thus to a fourth-order topology, but it can be extended to a wide class of converters suitable for PV applications. The reachability and existence conditions give rise to a number of design inequalities that add to the classical steady-state conditions in order to have the desired closed-loop converter's performances. The superiority of the control technique over the classical tracking methods is analytically demonstrated through the procedure proposed in this paper. The analytical results have been validated by means of both simulations and experiments.
01 Jan 2014
TL;DR: In this paper, the contribution of wind power providing active power control (APC) can benefit the total power system economics, increase revenue streams, improve the reliability and security of the power system, and provide superior and efficient response while reducing any structural and loading impacts that may reduce the life of the wind turbine or its components.
Abstract: This paper details a comprehensive study undertaken by the National Renewable Energy Laboratory, Electric Power Research Institute, and the University of Colorado to understand how the contribution of wind power providing active power control (APC) can benefit the total power system economics, increase revenue streams, improve the reliability and security of the power system, and provide superior and efficient response while reducing any structural and loading impacts that may reduce the life of the wind turbine or its components. The study includes power system simulations, control simulations, and actual field tests using turbines at NREL's National Wind Technology Center (NWTC). The study focuses on synthetic inertial control, primary frequency control, and automatic generation control, and analyzes timeframes ranging from milliseconds to minutes to the lifetime of wind turbines, locational scope ranging from components of turbines to large wind plants to entire synchronous interconnections, and additional topics ranging from economics to power system engineering to control design.
TL;DR: In this paper, a three-phase dc-ac converter with two-stage zero voltage switching (ZVS) operation for grid-tied PV system is proposed which will reduce cost per watt, improve reliability, and increase scalability of MW-class solar farms through the development of new solar farm system architectures.
Abstract: Module integrated converters (MICs) in single phase have witnessed recent market success due to unique features such as improved energy harvest, improved system efficiency, lower installation costs, plug-and-play operation, and enhanced flexibility and modularity. The MIC sector has grown from a niche market to mainstream, especially in the United States. Assuming further expansion of the MIC market, this paper presents the microinverter concept incorporated in large size photovoltaic (PV) installations such as megawatts (MW)-class solar farms where a three-phase ac connection is employed. A high-efficiency three-phase MIC with two-stage zero voltage switching (ZVS) operation for the grid-tied PV system is proposed which will reduce cost per watt, improve reliability, and increase scalability of MW-class solar farms through the development of new solar farm system architectures. The first stage consists of a high-efficiency full-bridge LLC resonant dc-dc converter which interfaces to the PV panel and produces a dc-link voltage. A center points iteration algorithm developed specifically for LLC resonant topologies is used to track the maximum power point of the PV panel. The second stage is comprised of a three-phase dc-ac inverter circuit which employs a simple soft-switching scheme without adding auxiliary components. The modeling and control strategy of this three-phase dc-ac inverter is described. Because the dc-link capacitor plays such an important role for dual-stage MIC, the capacitance calculation is given under type D voltage dip conditions. A 400-W prototype was built and tested. The overall peak efficiency of the prototype was measured and found to be 96% with 98.2% in the first stage and 98.3% in the second stage.