MPPT Mode Research Articles

Response surface methodology optimization of characteristics of biodiesel powered diesel engine and its effective integration to autonomous microgrid

An optimum diesel engine load condition with higher thermal efficiency and energy management has been the foremost challenge in the renewable energy research field. Modern trends involve nano additives for obtaining high performing biodiesel blends. Considering the above-mentioned factors, an experimental study along with statistical analysis has been performed with variation of compression ratio (16, 17.5 & 18), ZrO2 nano additive (50, 100 & 150 ppm) and load (50, 75 & 100 %). The optimization was accomplished by diminishing the BSFC, NOx, HC, CO, and increasing the BTE, CO2 using the approach of desirability. From the obtained results, the optimum operating conditions of the engine were found to be 75 % load, 18:1 compression ratio, and 150 ppm ZrO2 nano additive. The actual values at optimized conditions are obtained as BSFC (0.27 kg/kWh), BTE (33.37 %), CO (0.71 %), CO2 (8.69 %), NOx (1270 ppm), HC (62 %) and Smoke (25.20 %) with error less than 5 %. It has been observed that the BSFC of the proposed biodiesel-diesel blend is lower than that of pure diesel in all levels of power output. The biodiesel fuelled diesel engine is integrated as backup power in autonomous microgrid with main power as solar PV system operated at MPPT mode. A hybrid power system based on solar PV and biodiesel generator set up is the better alternative to emission-intensive fossil fuel and intermittent renewable.

Coordinated control of wind-storage combined with primary frequency regulation and variable coefficient based on wind speed and SOC

The increase of wind power penetration rate will cause the power system to face the problems of lower inertia level and insufficient primary frequency regulation capability, which will seriously affect the system frequency security. Wind turbine generally operate in MPPT mode, and the primary frequency regulation capability is realized through additional control, but when the wind turbine uses the kinetic energy of the rotor to participate in the primary frequency regulation of the system, it will cause a secondary drop in the system frequency. Participating in the primary frequency regulation of the system with the energy storage auxiliary wind turbine can further reduce the depth of the system frequency drop and improve the secondary drop of the system frequency. However, after the energy storage participates in the system frequency regulation, the State of Charge (SOC) will decrease, which will affect the frequency regulation capability of the subsequent energy storage. In view of the above problems, a control strategy of wind and storage participating in the primary frequency regulation of the power system is proposed considering the energy storage recovery strategy. During the primary frequency regulation, the joint output of the wind turbine using virtual inertia control and the Energy storage battery using droop control can effectively suppress the system frequency drop; During frequency regulation, the Energy storage battery is charged using a recovery strategy to ensure that the SOC of the Energy storage battery is in the state of maximum frequency regulation capacity. The three-machine and nine-node model of the wind and storage system is built through RTLAB. The real-time simulation verifies that the joint output of the wind and storage system under the step disturbance increases the minimum value of the power grid frequency drop and increases the minimum value of the frequency secondary drop. It can also be used under continuous disturbances. Realize the recovery of energy storage SOC.

An improved control for a stand-alone WEC system involving a Vienna rectifier with battery energy storage management

This study focused on efficiency improving, the power flow management and control problem of the standalone wind energy conversion system. Specifically, the system under study consists of a Permanent Magnet Synchronous Generator (PMSM) driving by wind turbine, Vienna rectifier, a Li-ion battery and a DC load. Battery life is vulnerable to fluctuations due to the intermittent nature of the wind, as well as to the demand for energy charging, which reduce considerably battery state of health (SOH) and consequently charging capacity. To overcome these shortcomings, a nonlinear battery charge controller is used to regulate the current supplied to the battery and to the load, and thus guarantee best charging performances. Based on the wind power, the load demand and the battery state of charge (SOC), three operating modes are considered. Specifically, MPPT mode, Constant Current (CC) charging mode and Constant Voltage (CV) charging mode. We also design a new energy management method to protect the energy storage system and increase its lifetime. This algorithm ensure a smooth switching between three controllers designed to provide the three operating modes. The high performances and the efficiency of the proposed controller and management algorithm are highlighted using several MATLAB/SIMULINK simulations.

Performance improvement through nonlinear control design and power management of a grid-connected wind-battery hybrid energy storage system

This paper presents a study on the application of nonlinear control and optimal power management techniques in a grid-connected wind energy conversion system with battery storage. The objective is to efficiently supply power to a load while considering performance constraints. The energy system under investigation comprises a wind turbine, battery, AC-grid, and load. Power is delivered to the load through various converters and a DC-link. However, the intermittent nature of wind energy and frequent load fluctuations can negatively impact the battery's lifetime and charging performance. To address these challenges, a nonlinear controller and a novel energy management system are designed. The energy management system generates multiple energy flow scenarios to achieve equilibrium in energy distribution between the load and energy sources. This equilibrium aims to minimize overall system costs, ensure DC-grid stability, and enhance power quality. Two distinct operation modes are identified: i) MPPT mode, which utilizes an optimizer to maximize power extraction, and ii) adaptive power point tracking (APPT) mode, which considers demand-driven production and the state of charge (SOC) of the storage system. The convergence of the closed-loop control is formally analyzed, and simulation results confirm the improved performance of the proposed multi-criteria design for energy management.

Centralized Energy Management Scheme for Grid Connected DC Microgrid

Energy management in DC microgrid is complex and challenging due to the stochastic nature of renewable energy sources and load demand. Coping with the deficit power, peak demand, and power converter control operations are a few major concerns. The photovoltaic (PV) system and battery energy storage system (BESS) utilization need special attention for the reliable and efficient operation of the DC microgrid. Hence, this article proposes the centralized energy management scheme (CEMS) in the DC microgrid to address the abovementioned challenges. The CEMS coordinates among the various physical layer components and computational layer (i.e., control layer) of the DC microgrid. It utilizes the multioptimization for energy management during the peak and <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> -peak load demand, optimal usage of PV-BESS, and performs the optimal load shedding operation. Furthermore, an optimal utilization of the PV-BESS problem is formulated and solved using linear programming to avoid excess usage of AC grid power. In deficit PV power, the optimal load shedding operation is formulated as mixed-integer linear programming problem to ensure the DC bus voltage regulation and power balance. The proposed CEMS demonstrates the effective operation of the PV system in maximum power point tracking, <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> -MPPT mode (i.e., voltage control), and BESS's charging/discharging operation. It is showcased that the hierarchical control structure of CEMS improves the performance, efficiency, and reliability of the DC microgrid operation. Hence, a 48 V and 1.2 kW PV-BESS-based DC microgrid system is developed to show the efficacy of the proposed algorithm under different scenarios in MATLAB/Simulink. The real-time simulator results of the developed system, obtained using OPAL-RT OP4510, confirmed the effectiveness and reliability of the proposed scheme.

Flexible Power Point Tracking Using a Neural Network for Power Reserve Control in a Grid-Connected PV System

Renewable energy penetration in the global energy sector is in a state of steady growth. A major criterion imposed by the regulatory boards in the wake of electronic-driven power systems is frequency regulation capability. As more rooftop PV systems are under installation, the inertia response of the power utility system is descending. The PV systems are not equipped inherently with inertial or governor control for unseen frequency deviation scenarios. In the proposed method, inertial and droop frequency control is implemented by creating the necessary power reserve by the derated operation of the PV system. While, traditionally, PV systems operate in normal MPPT mode, a derated PV system follows a flexible power point tracking (FPPT) algorithm for creating virtual energy storage. The point of operation for the FPPT of the PV is determined by using a neural network block set available in MATLAB. For the verification of the controller, it is applied to a PV array in a modified IEEE-13 bus system modeled in the MATLAB/Simulink platform. The simulation results prove that when the proposed control is applied to the test network with renewable energy penetration, there is an improved system inertia response.

Design and Implementation MPPT-CPG for Constant Power Battery Charger

The power produced by photovoltaic is very dependent on irradiation conditions and temperature so that the power can be low or high. The load cannot work if the power is low, but it harms the load if the power is too high. Two modes are used for this system, they are MPPT and CPG mode. When PV power is less than limit power (Plimit), then it works on MPPT mode. The MPPT finds maximum power, then if PV power reaches Plimit or more, it works on CPG mode. During CPG mode, SEPIC converter output power is maintained constant at Plimit so the battery can be charged using the Constant Power Method. The Algorithm used for each mode is the variable Step Size Climbing. The Variable Step Size Hill-Climbing on MPPT performs maximum power according to irradiation conditions. Variables Step Size Hill-Climbing on CPG stabilizes the output power value of SEPIC being constant to charge the battery using the power constant method by keeping the power as constant as its limit power, voltage and current electricity bring into line with charge conditions. The results of the hardware integrated test for MPPT-CPG, the Variable Step Size Hill Climbing algorithm can search for the maximum power point (MPP) generated by PV and can produce an output power of 27.97 W in average.

An Integrated Power Control Module for Photovoltaic Sources in DC Microgrid System

Photovoltaic (PV) arrays are highly compatible with DC microgrids as they are DC sources. However, the uncontrolled penetration of PV power in a DC grid will lead to overvoltage problems. This paper proposes an Integrated Power Control (IPC) Module for multiple PV sources in a DC grid which allows PV sources to deliver maximum power in MPPT mode and also works as a voltage controller to maintain DC bus voltage in droop mode. Thus, the IPC module integrates MPPT and DC bus voltage regulation in a single controller, reducing the complexity of the system and avoiding the need for the controller to switch between MPPT and droop mode as in conventional methods. Further, during unequal shading conditions between the multiple PV sources, the proposed IPC module effectively shares the power and operating the PV sources to deliver the available power to the DC bus. Thereby, the total efficiency of the system is increased. The IPC module is implemented in simulation for multiple PV sources on a DC grid, and maximum power tracking and power-flow management are verified. The prototype hardware setup is developed, and the results are presented to demonstrate the simple and cost benefited IPC module.

A Novel Approach on the Advancement in Polymer Phase Change Material in Solar Energy

A wide interest has been shown in the application of solar energy in recent times. This motivated the researchers to make a development in the approach of solar energy, but there are different technologies like MPPT, CPG, and grid mode that have been used to maintain a constant temperature. Among these, phase change material has been used to regulate the temperature in the system. Solar energy is becoming an essential approach for increasing the efficiency of thermal energy conversion and utilizing polymeric step change composites, which have attracted extremely large interest in recent years due to their advantages of high energy density and powerful energy output stability. A plethora of reviews and reports have been published to compile the diverse range of PCMs made available for various applications. PCMs are created by improving thermophysical thermodynamic stability, latent heat, and heat capacity. Furthermore, the possible applications of polymer phase PCMs in a variety of fields, such as energy storage devices, thermal corrective action, and temperature-controlled drug carriers, are detailed. In this paper, a novel approach on the advancement of nanoconfined phase change material is defined along with the application of the solar energy system.

Multi-objective control strategy of PV conversion system with storage energy management

This paper proposes an advanced control scheme for a hybrid renewable energy system based on a PV conversion system and Li-ion Battery. This strategy ensures three operating modes are handled by a suitable algorithm based specifically on battery State of Charge (SoC): (i) MPPT mode: used when the system is controlled to operate in its Maximum Power point. (ii) CC mode ensures fast battery charging. For this, the current sunk to the battery is controlled to its maximal value. (iii) CV mode: The battery is almost charged, one switch to this mode to preserve the battery by regulating the DC bus voltage to its nominal value. The stability of the nonlinear controller, based on Backstepping and sliding mode, is demonstrated using appropriate Lyapunov functions. Several simulations are used to validate the effectiveness of the controller.

Improved Super Twisting Based High Order Direct Power Sliding Mode Control of a Connected DFIG Variable Speed Wind Turbine

This work presents the theoretical and practical comparison of linear and nonlinear control laws for the direct power control of a grid-connected double fed induction generator (DFIG), based wind energy conversion system (WECS) under different operating modes. We will show the improvement brought by the super twisting based high order sliding mode control to mitigate the chattering phenomenon, due to the high switching frequency. It will also avoid the hyperlink of the controller settings to the system’s mathematical model and will reduce the sensibility to external disturbances. The overall structure of the proposed control requires the use of the DFIG simplified model with field-oriented control (FOC). This last allows an instantaneous decoupled control of the DFIG stator active and reactive power by acting on dq rotor currents (Iqr , Idr ) respectively. In the preliminary tests, a comparative study is conducted to verify the superior performance of the proposed WECS control scheme during various operating modes including the maximum power point tracking MPPT mode. The study reveals the effectiveness of each implemented control law with its advantages and drawbacks.

Harnessing Maximum Power from PV Module using DC-DC Converter

Solar energy is one of the most potent sources of energy. In the wake of depleting fossil fuel energy sources and growing environmental concerns, world is in a relentless drive towards utilizing natural resources like sun efficiently. The aim of the project is to make the solar module work in MPPT mode (Maximum Power Point Tracking) Mode. At this condition, the system is able to extract maximum power from the module without affecting the PV module. MPPT control here is obtained using boost converter. Applying PWM with proper controlling algorithm will vary the duty ratio of the converter such that system will run in MPP mode.

Multi-Mode Operation and Control of a Z-Source Virtual Synchronous Generator in PV Systems

The increasing penetration of power electronics-based distributed energy resources (DERs) displacing conventional synchronous generators is rapidly changing the dynamics of large-scale power systems. As the result, the electric grid loses inertia, voltage support, and oscillation damping needed to provide ancillary services such as frequency and voltage regulation. This paper presents the multi-mode operation of a Z-source virtual synchronous generator (ZVSG). The converter is a Z-source inverter capable of emulating the virtual inertia to increase its stability margin and track its frequency. The added inertia will protect the system by improving the rate of change of frequency. This converter is also capable of operating under normal and grid fault conditions while providing needed grid ancillary services. In normal operation mode, the ZVSG is working in MPPT mode where the maximum power generated from the PV panels is fed into the grid. During grid faults, a low voltage ride through control method is implemented where the system provides reactive power to reestablish the grid voltage based on the grid codes and requirements. The proposed system operation is successfully validated experimentally in the OPAL-RT real-time simulator.

An Adaptive Current Limiting Controller for a Wireless Power Transmission System Energized by a PV Generator

The use of a wireless power transmission system (WPTS) in modern applications, such as consumer electronics, renewable energy sources (RESs) and electric vehicles (EVs), can significantly increase the safety and convenience of the power supply. However, low efficiency is a major hurdle to the use of a WPTS in these applications. In this article, an adaptive virtual impedance controller (AVIC) is presented to enhance the wireless power transfer (WPT) efficiency of a photovoltaic generator (PVG) to the load. In the proposed controller, a unique method is employed to adaptively estimate the coefficient of coupling and resonant frequency of the WPTS coils as a function of the distance between the coils. Moreover, a modified incremental conductance (IC) based maximum power tracking (MIC-MPPT) technique is presented to operate the PVG at MPPT mode. The proposed MIC-MPPT is tested via a hardware prototype and the controller validation is carried out in the MATLAB/SIMULINK environment under various uncertainties, such as intermittent irradiance, variable load, and the distance between transmitter (Tx) and receiver (Rx) coils. Finally, a comparative analysis between the proposed controller and the conventional non-adaptive and adaptive resonant frequency controller is presented which confirms the superiority of the proposed controller.

Adaptive Robust SMC-Based AGC Auxiliary Service Control for ESS-Integrated PV/Wind Station

Power source structure has developed significantly because of the increasing share of renewable energy sources (RESs) in the power system. RESs bring inevitable impacts on power system frequency, voltage regulation, and power system stability. The conventional automatic generation control (AGC) loops which relay only on the synchronous generating units cannot meet the requirements of these new circumstances. This paper presents an ESS-integrated PV/wind station topology and its control structure for AGC auxiliary service in order to provide existing RESs the additional functionality of AGC auxiliary service without changing their control strategies conceived for MPPT mode. The shifting operation modes and external disturbances make ESSs in an ESS-integrated PV/wind station inherently nonlinear and time variable. Therefore, an adaptive robust sliding-mode control (ARSMC) system is proposed. The ARSMC colligates the advantages of adaptive control and SMC contains state feedback term, robust control term, and adaptive compensation term. The strictly logical and rigorous proof using Lyapunov stability analysis indicates the ARSMC system is insensitive to parametric uncertainties and external disturbances; meanwhile, it guarantees fast response speed and high control precision. The case studies on NI-PXI platform validate the effectiveness of the proposed approach.

Integration of sub-gradient based coordinate for multiple renewable generators in microgrid

Microgrids and smart grids are the future of the conventional grids. It will be an immense need to integrate the Distributed Generators (DGs) with smart grids and microgrids. DGs are mostly the solar energy, wind energy and small hydel power. These DGs has several advantages as high penetration of power will reduce the power loss, reduce the voltage drop and maintain the terminal voltage. These DGs are difficult to integrate with the microgrids in islanded mode as these causes severe fluctuation which disturbs the supply–demand balance. Renewable generators (RGs) working in MPPT mode cause high fluctuations when the RGs are working on islanded mode and generating more power than demand. Therefore, a control system is required to manage this issue and to maintain the balance of the system. Sub-gradient based distributed coordination technique is utilized for the control of renewable generators in which the supply–demand balance is maintained by coordinating the system with the utilization level. Simulation results will exhibit the operation of the controlled microgrid, its integrated DGs and will prove the efficiency and the effectiveness of the proposed methodology.

Power Quality and Capability Enhancement of a Wind-Solar-Battery Hybrid Power System

The Adrar site located in the south of Algeria, presents the most important windy and sunny site in Algeria that can be exploited. In this context for the exploitation of the two complimentary sources of this site (wind and sun) based on the meteorological data, the present paper focuses on the study of a Hybrid System (HS) based on an interconnection between a Wind Energy Conversion System (WECS) and a Photovoltaic System (PVS) which is planted in the DC-link bus of the back-to-back converter feeding the Double Feed Induction Generator (DFIG) rotor of the WECS. The objective of using this proposed coupling topology is to exploit the two available complementary renewable sources in the same time, to enhance the exploitation rate of the un-resized WECS back-to-back converter which remains at low power in the weak wind case or in the synchronism case and to eliminate the PVS inverter. Consequently the overall cost of the HS can be reduced. On the other side, to solve the energy quality problem; a modified MPPT mode control technique is proposed and compared with two other conventional techniques, the first one uses the PVS to offset only the WECS power rapid fluctuations and the second one uses a Battery Storage Unit (BSU) to ensure the produced energy smoothing. This BSU plays also an interesting role to store the surplus of energy when the maximum power level of the WECS converter is reached in case of wind and/or irradiation abundances.

A High-Performance Shade-Tolerant MPPT Based on Current-Mode Control

This paper proposes a high-performance shade-tolerant maximum power point tracking (STMPPT) technique for dc-dc converter stage of photovoltaic (PV) applications. The average current-mode control (ACMC) is utilized to regulate the PV array current using two feedback control loops. The current-mode control is a superior scheme in control of dc-dc power electronic converters. The proposed STMPPT technique operates in two modes. The ACMC with the perturb and observe (P&O) MPPT algorithm functions in a local MPPT mode under normal irradiance condition. When the PV array is likely to be partially shaded, a global MPPT subroutine effectively scans the PV profile to optimize the PV system operation. This is achieved by implementing simple innovations to the ACMC-based P&O algorithm. The innovations benefit from useful observations of I-V characteristics. The idea behind using the I-V characteristics is to significantly reduce the search space, make the algorithm independent of shading conditions and PV array configuration, and inherently recognize the occurrence of partial shading conditions. The proposed STMPPT technique enables very fast and reliable tracking of global maximum power point. In addition, it can stably work under dynamic environmental change without losing correct sense of tracking direction. Its simplicity and independency would offer a viable solution for PV converter products. Simulation and experimental performance assessments are presented under different operating conditions that could happen in outdoor PV installations.

A Control Strategy for a Three-Phase Grid Connected PV System under Grid Faults

This paper proposes a Low-Voltage Ride-Through control strategy for a three-phase grid-connected photovoltaic (PV) system. At two stages, the topology is considered for the grid-tied system fed by a photovoltaic generator with a boost converter followed by a three-phase voltage source inverter. A flexible control strategy is built for the proposed system. It accomplishes the PV converter operations under the normal operating mode and under grid faults (symmetrical and asymmetrical grid voltage sag). The boost converter is controlled via an incremental conductance maximum power point tracking technique to maximize the PV generator power extraction. In the case of voltage sag, the implemented control strategy provides a switch between MPPT mode and non-MPPT mode to ensure the protection of the power converters. Theoretical modeling and simulation studies were performed, and significant results are extracted and presented to prove the effectiveness of the proposed control algorithm.

A Control Strategy for Reliable Power Output From a Stand-alone WRIG With Battery-Supported DC Link

This paper proposes a versatile control strategy for a standalone wound rotor induction generator (WRIG) with back-to-back converters supported by a battery at dc-link. The principal feature of the study is the operation of the generator as a commanded current source, to supply only sinusoidal current as desired, and the operation of battery fed Front End Converter (FEC) as a constant voltage source, which adapts to varying load conditions. Further, in implementing this feature, in a significant deviation from conventional approaches, to Rotor Side Converter (RSC) and FEC are redefined with a view to achieve versatility and reliability in stand-alone operation. In particular, the RSC is employed to track the maximum power (instead of load voltage and frequency control), whereas the FEC maintains a constant load voltage and frequency. It is revealed that there are multiple benefits of the proposed strategy such as inherent load balancing; capability to support critical loads solely by battery through the FEC as in an uninterruptible power supply (UPS), especially at low wind speeds; compensating unbalanced or harmonic load currents via FEC (as in an active power filter); and smooth transition between the MPPT mode and the UPS mode by synchronization. Simulation results of a 2-MW wind turbine, along with test results of a 2.3-kW laboratory setup, validate the proposed strategy.