Maximum Power Control Research Articles

Advanced Maximum Power Control Algorithm Based on a Hydraulic System for Floating Wave Energy Converters

An integrated analysis is required to evaluate the performance of control algorithms used in power take-off (PTO) systems for floating wave energy converters (FWECs). However, research on PTO systems based on the existing hydraulic device has mainly focused on the input power generation performance rather than on obtaining maximum power through hydraulic device-based electrical load control. The power generation performance is analyzed based on the control variables of the existing torque control algorithm (TCA); however, the amount of power generation for each control variable changes significantly based on the cycle of wave excitation moments. This paper proposes a control algorithm to obtain the maximum power by modeling a hydraulic-device-based integrated FWEC. It also proposes a TCA that can obtain the maximum power regardless of the period of wave excitation moment. The proposed TCA continuously monitors the power generation output and changes the PTO damping coefficient in the direction in which the power generation output can be increased. The proposed TCA increased the output power generation by up to 18% compared to each PTO damping coefficient of the conventional TCA. Thus, the proposed method results in higher power generation regardless of the wave excitation moment cycle and performs better than the existing torque control algorithm.

Compensation of Interpolation Error for Look-Up Table-Based PMSM Control Method in Maximum Power Control

This paper proposes a compensation method for interpolation error of the maximum power control of a PMSM control system that generates current commands through a look-up table. A torque control system using a look-up table created through experiments has superior characteristics, such as control stability and torque accuracy, compared to a system that executes torque control via a linear controller based on modeling. However, it is impossible to generate information on all the currents for the output torque in the table. Therefore, because the data stored in the look-up table have a discrete characteristic, they are linearly interpolated to generate a current command for the torque command. However, the PMSM current trajectory is generally elliptical, which causes an error owing to linear interpolation, reducing the maximum output power. In particular, when the table data are insufficient, such as in the high-speed operation range, the reduced maximum output cannot be ignored. This paper proposes a compensation method for the interpolation error using two feedforward compensators and a PI controller, which was verified through experiments.

Optimal design and analysis of DC–DC converter with maximum power controller for stand-alone PV system

This paper proposes a method for selecting the parameters of the main components of an autonomous photovoltaic (PV) stations to ensure the most efficient conversion and use of solar energy. The main energy characteristics are analyzed and the mathematical models of the components of an autonomous PV system are developed to study the modes of tracking the maximum power point (MPP). The necessary conditions for matching the parameters of the PV and the DC–DC buck converter are evaluated to track the MPP. This paper aims to create an original method and algorithm for calculating and selecting parameters of the main elements of a PV stations. The optimal value of the sampling time of the MPP controller is obtained for different schemes of the PV system . A practical example is considered for selecting the parameters of a DC–DC buck converter and a digital MPP of an autonomous PV station. The simulation of dynamic modes of an autonomous photovoltaic (PV) station is performed in the MATLAB/SIMULINK software package. The simulation results of dynamic operations of the PV system show that the voltage converter and the MPP controller with the selected parameters according to the proposed method provide reliable and effective tracking of the MPP in all different connections of the PV.

구동 인버터 및 하프브릿지를 이용한 전기차 배터리 충전기법

In general, on-board chargers (OBCs) are used to charge the battery of electric vehicles(EVs). However, the OBC has disadvantages such as cost and increase in weight of EVs which can make worse the driving efficiency. This paper proposes an integrated battery charging module by utilizing a three-phase inverter for driving, inductance of the motor and additional half-bridge circuit. In addition, the switching pattern of the proposed module are derived according to the output voltage during charging the battery. A current control method is proposed which can perform maximum effective power control and position control simultaneously. Finally, the proposed module and current control method are validated through simulations and experiments.

Adaptive Control of Wind Turbine Generators for Power Capture Optimization by Using Integral Backstepping Approach During Partial-Load Operation

The paper proposes an effective nonlinear integral backstepping approach strategy (IBS) through the use of a new adaptive power control algorithm for variable-speed wind turbine generators (VS-WTGs) to optimize the power extracted from the WTGs. The suggested approach is applied to one of the most frequently used maximum power control methods called as tip speed ratio (TSR) during partial-load operation considering the effects of the variations in wind velocity profile and unmodeled system dynamics such as external disturbances. The proposed method of control is known to scale-back the mechanical stress at the level of the GT shafts (generator and turbine). Furthermore, the IBS approach is relatively simple, which significantly reduces the online computational time and cost. Some numerical simulation results prove, under different wind speed models, that the proposed AC-TSR-IBS method works well on the level of the improved efficiency and the rapid system response compared to conventional TSR-PI method.

Adaptive Hybrid Generalized Integrator Based SMO for Solar PV Array Fed Encoderless PMSM Driven Water Pump

The encoder influences reliability and cost of permanent magnet synchronous motor (PMSM) operated solar water pump (WP). It is even sensitive to electromagnetic noise and temperature, which thereby reduces its accuracy. To overcome these problems, an encoderless PMSM control by using adaptive hybrid generalized integrator (AHGI) based sliding mode observer (SMO) for the solar WP system is presented in this paper. The widely used low pass filter based SMO produces phase-shift, attenuation and dominant lower order harmonics (DLOH). This decreases the position estimation accuracy. Besides, the need for tracking dynamic system frequency further exacerbates its performance. The developed AHGI structure eliminates these drawbacks and provides an accurate estimate of position over a wide speed range. A harmonic decoupling network, a hybrid generalized integrator and an adaptive frequency tracker constitute AHGI, which respectively performs dominant harmonic signal generation, DLOH elimination and frequency tracking. The improvement in behavior of AHGI over the existing methods is analyzed by transfer functions, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Bode</i> plots and back electromotive force helices. Meanwhile an incremental conductance algorithm for PV array maximum power control is used. The developed structure is experimentally validated on a laboratory prototype and a comparison with the existing methods is also made.

Multi-target charging strategy for smartphones based on laser wireless power transmission and machine vision technology

A novel method of multi-target charging is proposed in this paper, in the context of charging multiple indoor mobile phones simultaneously. Based on the laser wireless power transmission system, combined with machine vision technology, the traditional two-stage circuit is turned into a single-stage type, which realizes longer distance and more convenient charging. This article analyzes the working mode and circuit topology of the dc-dc converter in the multi-target charging mode, and analyzes the positioning and charging strategies for multi-targets based on machine vision. Under the strategy, the output voltage of the photovoltaic panel can be adjusted by modulating the pulsed light, so as to achieve the maximum power control for mobile phone charging. The simulation results are provided in this paper to validate the effectiveness of the proposed approach.

An Improved Transformerless Grid-Connected PV System With Related Control Strategy to Reduce Leakage Current, Extract Maximum Power Point and Control Power

An Improved Transformerless Grid-Connected PV System With Related Control Strategy to Reduce Leakage Current, Extract Maximum Power Point and Control Power

Power Performance Analysis According to the Configuration and Load Control Algorithm of Power Take-Off System for Oscillating Water Column Type Wave Energy Converters

A power take-off (PTO) system for an oscillating water column (OWC) wave energy converter comprises a turbine-generator-power converter. In this study, only the topologies of the power converter that affect the load control algorithm are compared. A power converter for renewable energy is composed of a diode-dc/dc converter and a pulse-width modulation (PWM) converter operating at small and large capacities, respectively. However, selecting a power converter according to the capacity based on the characteristics of the wave energy converter, in which the input energy is highly fluctuating, can significantly reduce the power performance. Thus, to verify load control characteristics according to the topology of the power converter, the turbine-generator-power converter was incorporated in the modeling, and the power performance based on the power converter topology under various wave conditions was analyzed. Further, torque control to obtain the maximum power among load control algorithms was applied under irregular wave conditions, and the power performance and PTO system characteristics according to the torque coefficient were analyzed. The results of this study suggested an increase in the torque coefficient of the maximum power control for the operational stability of the OWC-WEC, and it was confirmed that the RPM characteristics of the PTO system were reduced.

Sensorless Maximum Power Control of a Stand-Alone Squirrel-Cage Induction Generator Driven by a Variable-Speed Wind Turbine

For the cost-effectiveness of variable-speed wind energy conversion systems (WECSs), it is extremely important to extract the maximum available power at different wind speeds within the normal operating range. Furthermore, reduction of the electric generator losses additionally contributes to the efficiency of the WECS, whereas reduction of the number of sensors is beneficial in terms of reliability and cost. This paper presents sensorless control of a stand-alone WECS comprising a squirrel-cage induction generator (IG) and a battery system. An indirect rotor-field-oriented control (IRFOC) algorithm including stray load and iron losses and online tuning of IG’s equivalent resistances and magnetising inductance is adopted for IG control to achieve high level of agreement with the actual machine. Fuzzy-logic-based optimisations of the wind turbine (WT) and IG are implemented to maximise the IG output power. The IG speed, which is required by the IRFOC algorithm, is estimated by using a model-reference-adaptive-system. The estimated IG speed is also utilised for online WT optimisation in combination with the IG torque obtained from the IRFOC equations. The performance of the proposed control strategy has been experimentally evaluated and compared with two competing sensorless control strategies for two 1.5 kW IGs of different efficiency class.

Mutual inductance estimation of multiple input wireless power transfer for charging stationary vehicles in parking spaces

The electric vehicle (EV) is the future of the modern automotive industry. However, the transmission performance of traditional wireless charging is highly influenced by the misalignment error between the transmitter and the receiver. This paper proposes a maximum power control method for the multiple transmitter coil wireless charging system, which can be used to charge stationary EVs freely and effectively in a wider range. An accurate and reliable mutual inductance estimation method is introduced to estimate M relying on the electric information on the transmitter side only without using empirical formulas and additional communication devices between both sides. Then, the paper proposes a control method, which can maximize the output power in a quite wider range. Experiments and simulations prove that the proposed method has a good performance on charging a receiver coil effectively in a wider range; therefore, it is suitable for charging stationary EVs in the parking space.

Grid-aware distributed control of electric vehicle charging stations in active distribution grids

The penetration of electric vehicle (EV) charging stations (CSs), along with the progressive connection of stochastic distributed generation, is increasing the probability of violating the power distribution grid operational constraints and deteriorate the quality of power supply. To this end, the paper proposes a real-time control scheme for allocating power set-points to EV CSs while accounting for the grid operational requirements. In the proposed problem formulation the grid and the power injections are modelled accounting for their unbalanced 3-phase nature, thus enabling to formulate the problem objective and its constraints adopting the sequence decomposition. The EVs’ users need, along with the stochastic nature of other uncontrollable injections (e.g. loads and generation from photovoltaic generation units), are also taken into account. A distributed control scheme, with a minute-scale control horizon, is proposed where local controllers, operating at EV aggregation level, compute EV battery-secure power set-points. These controllers send their set-points to a central controller operating at the grid aggregation level. The central controller solves a scenario-based linearised optimal power flow accounting for grid operational and power quality constraints. Then, it sends back its solution to the respective local controllers. The obtained iterative algorithm is efficiently solved until convergence. We analyse the performance of the proposed control scheme via a simulation ran on the IEEE-34 feeder. Comparisons with two other control algorithms, a grid-unaware local controller and a myopic maximum power controller, are included to benchmark the proposed control scheme.

Design and Performance Analysis of Distributed Equal Angle Spiral Vertical Axis Wind Turbine

Background: The wind turbine is divided into a horizontal axis and a vertical axis depending on the relative positions of the rotating shaft and the ground. The advantage of the choke wind turbine is that the starting torque is large and the starting performance is good. The disadvantage is that the rotation resistance is large, the rotation speed is low, the asymmetric flow occurs when the wind wheel rotates, the lateral thrust is generated, and the wind energy utilization rate is lowered. How to improve the wind energy utilization rate of the resistance wind turbine is an important issue to be solved by the wind power technology. Objective: The nautilus isometric spiral wind turbines studied in this paper have been introduced and analyzed in detail, preparing for the further flow analysis and layout of wind turbines, improving the wind energy utilization rate of wind turbines, introducing patents of other structures and output characteristics of its generator set. Methods: Combined with the flow field analysis of ANSYS CFX software, the numerical simulation of the new wind turbine was carried out, and the aerodynamic performance of the new vertical axis wind turbine was analyzed. The mathematical model and control model of the generator were established by the maximum power control method, and the accuracy of the simulation results was verified by the measured data. Results: The basic parameters of the new wind turbine tip speed ratio, torque coefficient and wind energy utilization coefficient are analyzed. Changes in wind speed, pressure and eddy viscosity were investigated. Three-dimensional distribution results of wake parameters such as wind speed and pressure are obtained. By simulating the natural wind speed, the speed and output current of the generator during normal operation are obtained. Conclusion: By analyzing the wind performance and power generation characteristics of the new wind turbine, the feasibility of the new wind turbine is determined, which provides reference and reference for the optimal design and development of the wind turbine structure.

Research on Modeling of Wind-solar Hybrid Microgrid and Control Strategy of Maximum Power Load

As an important form of receiving renewable energy, microgrids can be a useful supplement to large grids, which can solve the power supply problem of residents in remote mountainous areas, pastoral areas, and islands. Modeling and simulation of energy management for microgrid operation characteristics with wind and solar storage have important practical significance. In this paper, mathematical models of photovoltaic cells and wind power systems are established, simulation models are constructed, and their respective characteristics are simulated and analyzed to verify the correctness of the mathematical models. A simulation model of maximum power point tracking for wind and solar power systems was established based on the respective shortcomings and limitations of independent operation of wind power systems and photovoltaic systems. According to the simulation results, it can be seen that the maximum power control technology used in this system can achieve maximum power tracking for wind power generation systems and photovoltaic power generation systems. The simulation results verify the correctness of the system and the feasibility of the control strategy.

A comprehensive improved coordinated control strategy for a STATCOM integrated HVDC system with enhanced steady/transient state behaviors

As a parallel type of reactive power compensation equipment, a static synchronous compensator (STATCOM) is often used to connect at the weak AC end of the inverter side of the high voltage direct current (HVDC) transmission system. In this paper, an improved coordinated control strategy of a STATCOM is investigated with three main contributions: 1) The operation modes of the STATCOM are analyzed and its steady-state mathematical model is established. The dynamic behaviors of the STATCOM under different operating conditions are studied; 2) A coordinated control strategy of the STATCOM, which takes both the steady-state and transient characteristics of the HVDC system into account, is proposed. The control strategy under steady states includes two control modes: constant AC voltage control and constant reactive power control. The control strategy under transient states also includes two control modes: fast reactive power droop control and active blocking control. Based on the operating conditions of both the HVDC system and the STATCOM, the decision criterion and the switching control of the STATCOM adopting the specific control strategy are proposed; 3) Aiming at the problem of slow reactive power response in the STATCOM using the traditional maximum reactive power control under transient conditions, a fast reactive power droop control strategy is proposed and a turn-off angle negative feedback control is added. This method can provide reactive power compensation more rapidly under transient conditions and mitigate the occurrence of commutation failures for the HVDC system. A simulation model of the STATCOM integrated HVDC system is established in PSCAD/EMTDC. The effectiveness of the proposed improved coordinated control strategy in enhancing the receiving AC system strength and reducing the probability of commutation failures under transient conditions, is verified by the simulation results.

MVMO-Based Identification of Key Input Variables and Design of Decision Trees for Transient Stability Assessment in Power Systems With High Penetration Levels of Wind Power

Unlike synchronous generators, wind turbines cannot directly respond to large disturbances, which may cause transient instability, due to their power electronic-based interface and maximum power control strategy. To effectively monitor the influence of wind turbines, this paper proposes an approach that combines decision trees (DTs), and a newly developed variant of the Mean-Variance Mapping Optimization (MVMO) algorithm, to simultaneously tackle the problem of selecting the key variables that properly reflect the transient stability performance of a system dominated by wind power, and designing the DTs for reliable online assessment of transient stability. The notion of key variables refers to the set of variables that are closely related to the modified power system transient stability performance as a consequence of the replacement of conventional power plants by wind generators. The selection of key variables is formulated as a non-linear optimization problem with weight factors as decision variables and is tackled by MVMO. A weight factor is assigned to each key variable candidate, and its value is considered to reflect the degree of influence of the key variable candidate on the splitting property and estimation accuracy of the DTs. The samples of the key variable candidates and the initialized weight factors are used to build the first group of DTs. Then, MVMO iteratively evolves the weight factors according to its special mapping function with minimizing DTs' estimation error. According to the final list of optimized weight factors, system operators can select a reduced set of variables with the largest weight factors as key variables, depending on the resulting accuracy of the DTs. Meanwhile, DTs built by using key variables are considered as the optimal performance trees for transient stability estimation. In this way, the selection of key variables and the development of DTs are made jointly and automatically, without the interference of the users of the DTs. Test results on the modified IEEE 9 bus system and a synthetic model of a real power system show that the proposed method can correctly identify the set of key variables related to wind turbine dynamics, as well as its ability to provide a reliable estimation of the transient stability margin.

Optimization of harvesting solar cell energy based on MPPT to be applied during the rainy season in the tropics

Energy harvesting systems in solar cells require control to get maximum power, the maximum power control system is maximum power point tracking (MPPT). Energy efficient and effective harvesting is needed to avoid the energy absorbed by the control system. MPPT method with the Perturb and Observe (p&o) algorithm system. P&O method is a change in the value of a certain voltage and looking at the current value, this method is very effective to get the maximum power produced by solar cells. Energy that is absorbed by solar cells during the rainy season is very limited because the intensity and duration of sunlight to the surface of the solar cells is very small, therefore harvesting energy with the MPPT system can produce effective energy.

Анализ режимов и выбор параметров преобразователя напряжения и контроллера максимальной мощности автономной фотоэлектрической станции

Анализ режимов и выбор параметров преобразователя напряжения и контроллера максимальной мощности автономной фотоэлектрической станции

Adaptive Maximum Power Control Based on Optimum Torque Method for Wind Turbine by Using Fuzzy-Logic Adaption Mechanisms during Partial Load Operation

This paper aims to increase the effectiveness of the Maximum Power Control (MPC) strategy by using a new Adaptive Maximum Power Control method (AMPC) for maximizing the power delivered by the Wind Turbine System (WTS) during partial load operation whatever the disturbances caused by variations in wind profile. The AMPC is applied to one of the frequently used Maximum Power Point Tracking (MPPT) methods called as Optimum Torque (OT) MPPT algorithm. Furthermore, the proposed AMPC strategy aims to optimize the wind energy captured by the WTS during partial load operation under rating wind speed, using Fuzzy-Logic as Adaption Mechanisms (AMPC- FLC). Additionally, the performances of the proposed improved OT-MPPT method based on AMPC-FLC are compared to the OT-MPPT method based on Conventional Maximum Power Control (CMPC-PI) under the same conditions. The robustness, dynamic performance, and fast approximation of the optimal value are proved with the numerical simulations under MATLAB/Simulink® software.

Synchronous Buck Converter for Improved Maximum Power Extraction on Small Stand-Alone Wind Power System using Modified perturb and observe (P&amp;O)

To increase the extraction power of a wind power system, the system must work at peak power. This paper presents maximum power extraction and control systems using a modified perturb and observe algorithm (MP&amp;O) to achieve high efficiency maximum power extraction of wind turbines that connected to permanent magnet synchronous generators (PMSG). To get maximum power from PMSG, MP&amp;O controls the duty cycle of synchronous buck based on the output power of the 12 pulses rectifier. The simulation results show that MP&amp;O can work optimally at every change of wind speed. MP&amp;O was also tested and compared with simple P&amp;O in terms of ripples under stable conditions, response speed and ability to obtain maximum energy output. The average efficiency and convergence time achieved by MP&amp;O are 99. 24% and 0. 71s.