Power management and adaptive control method for a standalone distributed generation system under fault, DC-offset, and dynamic environments

The solar photovoltaic (PV)‐based microgrid is one of the most ideal renewable energy resources. This paper presents a utility grid intertie multi‐PV‐inverter‐based microgrid (MG) control for the solar rooftop application. The main and ancillary voltage source converters (VSCs) DC links are assimilated with PV arrays of independent maximum power point tracking (MPPT) algorithms for the economical and efficacious single‐stage configuration. At the point of common coupling (PCC), parallel VSCs arrangement increases the MG's power rating with distinctive local loads. In normal circumstances, the current control methodology is employed by the main VSC under the grid‐interactive mode. Conversely, in some grid contingency conditions under the isolated mode, its control transfers to the voltage control, which regulates the frequency and the voltage at PCC and acts like a grid‐forming inverter. The ancillary VSC operation is implemented with the current control algorithm. The main VSC supplies the active power towards the grid and accomplishes the load requirement, whereas the ancillary VSC retains its load demand in a grid‐interactive mode and also regulates the load requirement in an islanded mode of operation. The utilization of feed‐forward components for PV arrays powers in the VSCs current control techniques improves the MG dynamic performance. The seamless mode transfer performance of the main VSC is implemented via a power electronics switch. The MATLAB software is used to model a microgrid and its performance is analysed via RT‐LAB in real time through the OPAL‐RT (OP4510) controller for various scenarios, that is, varying solar insolation, load alterations and unbalanced non‐linear loads. The utilization of the modified Kwong's algorithm‐based current control enhances the power quality such as harmonics current elimination and improvement in the power factor. The voltage profile of PCC voltages is enhanced via using a modified Kwong's algorithm‐based filter in the voltage controller. The modified Kwong's algorithm has fast convergence, reduces misadjustments and gives very good performance compared to the least‐mean‐square (LMS) and Kwong's approaches. The total harmonic distortion (THD) of grid currents and PCC voltages THD in an isolated mode is found according to the limits of the IEEE‐519 standard.

This paper presents a three-phase four wire grid interactive multiple solar photovoltaic (PV) and a battery based microgrid system. The DC links for the main voltage source converter (VSC) and the ancillary VSC are interfaced individually, to two solar PV arrays using a different maximum power point (MPP) tracking control i.e. incremental conductance (InC) method, in an inexpensive and effectual single stage topology. These VSCs are interfaced in parallel linkage to the point of common coupling (PCC) with distinct nonlinear loads, to enhance microgrid rating for distributing the active power on grid side and the system is reliable in an islanded mode. In normal situations, the current control is used for the main VSC in the grid intertied mode and at the disconnection from the grid, this system operates with the voltage control. The main VSC's mode transition performance is free from transitory and is obtained by a power electronic switch (PES). At the main VSC DC link, a DC-DC converter with the buck-boost operation is linked in series with the battery, manages the load network demand and sustains the DC link's voltage to MPP. At the PCC, frequency and voltage are regulated via voltage control and gives incessant power to the loads and good quality voltage is provided to the ancillary VSC to perform through the current control. The current control is utilized for power factor correction, harmonics eradication and enhancement of system's dynamics with PV feed-forward part. The microgrid operation is found satisfactory for scenarios like, grid outage, solar irradiance alteration, load unbalance and neutral current compensation and authenticated through simulated results obtained in MATLAB / SIMULINK platform.

Solar Photovoltaic (SPV) offers alternative sources of energy which is in general pollution free, environment friendly, sustainable and unlimited in nature. The concerns of environment due to green house gases and global warming force research communities to develop a smart power system that has capability to integrate Solar Photovoltaic with the power grid. There are many challenges in integrating SPV generation with the grid like efficiency, power quality, stability, cost of the energy conversion, load management, reliability etc. Moreover, power quality problems at distribution level like harmonics, unbalanced supply, unbalanced loads, reactive power, load management etc. affect the operation of grid connected SPV systems. Single stage grid connected PV systems has the advantage of use of a single VSC for MPPT (Maximum Power Point Tracking) and inverter operation. The proposed grid interfaced SPV generating system consists of a SPV array, VSC (Voltage Source Converter), three-phase grid and linear/nonlinear loads. The SPV energy is injected in to the DC bus of VSC during sunshine hours. The DC bus voltage of a three- phase VSC is regulated for MPPT from the PV array. Secondly, this system serves to provide harmonics elimination, load balancing, power factor correction (PFC) and regulating the terminal voltage at the PCC (Point of Common Coupling). In this paper, a SRF (Synchronous Reference Frame) based control of a single stage dual purpose grid connected SPV system is proposed and simulation based on MATLAB and Simpower System Blockset demonstrates the dual purpose of the system.

This paper presents a real-time simulation of a photovoltaic-based distribution static compensator (PV-DSTATCOM) using the Typhoon HIL 604 simulator, demonstrating its effectiveness in reactive power compensation, harmonic mitigation, and active power injection. The system seamlessly transitions between pure DSTATCOM mode, operating during night-time or when PV generation is zero, and PV-DSTATCOM mode, where it injects PV power while enhancing the power quality. A voltage source converter (VSC) regulated by an indirect current control strategy ensures improved power quality at the point of common coupling (PCC). Real-time simulation results under both balanced and unbalanced PCC voltage conditions validate the ability of the PV-DSTATCOM to mitigate power quality disturbances. Notably, the PV-DSTATCOM effectively reduces total harmonic distortion (THD), maintaining levels between 3.03%–5.58% under balanced PCC voltage and 3.95%–5.93% under unbalanced PCC voltage conditions, generally adhering to or remaining near the acceptable limit of IEEE-519 standards across varying solar irradiance levels and non-linear load conditions. Additionally, it maintains a near-unity power factor operation at PCC and stabilizes the DC-link voltage at 900 V (± 5%), ensuring reliable operation.

<p><span lang="EN-US">This work proposes an adaptive filter based on a new least mean sixth control approach with incremental conductance method of MPP for 3-phase grid-incorporated photovoltaic (PV) system. The proposed system comprises a PV array, 3-phase DC to AC converter, maximum power point tracker (MPPT), three-phase electronic load, and a 3-phase grid. The combination of solar PV array and the voltage source converter (VSC) supplies power to the grid. The 3-phase inverter as a distribution static synchronous compensator (D-STATCOM) improves the quality of the system performance in case of zero solar irradiation. D-STATCOM also reduces total harmonic distortion (THD) in grid currents, improves power factor, and maintainsa constant voltage at the point of common coupling (PCC). The system modelling and simulation is achieved on MATLAB/Simulink. The proposed system performance has been found satisfactory and conform to IEEE-519 standards.</span></p>

This work is associated with the renewable energy based microgrid for a standalone operation. The places where the renewable energy sources such as wind, solar, hydro etc. are in abundance can be used to generate electricity by developing microgrid (MG) such as wind- hydro MG. A synchronous reluctance generator (SyRG) is used as a constant speed hydro turbine and a permanent magnet brushless DC generator (PMBLDC) as a variable speed wind turbine. The wind power is converted into electricity and converted into DC power using three phase diode bridge with a boost converter, a maximum power point tracking (MPPT) based perturb and observe (P&O) technique is applied. This power is fed to a battery bank and the consumer loads. The battery bank is attached at DC bus of VSI (Voltage Source Inverter). The SyRG is directly feeding to the AC loads and VSI is connected at the PCC (Point Of Common Coupling). This VSI is also used for the power quality improvements through harmonic suppression of nonlinear loads, voltage regulation during contingencies like load unbalance, reactive power compensation according to the system requirement etc. at PCC. It is capable of providing power balance with various changes. For the appropriate functioning of VSI, a reweighted zero attractor least mean square (RZALMS) control algorithm is applied to generate PWM switching pulses. A MG model is developed in MATLAB/ Simulink environment to simulate the MG performance in normal and dynamic conditions at linear and nonlinear loads.

In this article, a fuzzy logiccontroller (FLC) tuned DC-link controller is presented. This controller is utilized to enhance the power quality characteristic of grid-integrated PV systems with power backup in comparison to the PI controller, without any filter at PCC (point of common coupling). The primary purpose of these controllers is to maintain power to the DC/AC sides by maintaining the DC-link voltage under transient conditions. The proposed system is tested with a non-linear load; hence, the proposed system requires power quality enhancements on PCC. By using both controller power flow control, reactive power compensation and harmonic mitigation is done on PCC, after that grid current becomes sinusoidal. For the power quality improvement, no filter/shunt active power filter (SAPF) is connected to PCC, only proposed inverter current controller improves the power quality at PCC by using these controllers. Using the MPPT (maximum power point tracking) Controller, the maximum power extraction feature is also included in this paper to extract maximum power from the PV module under varying atmospheric circumstances. The power backup unit is also connected with this system, power backup unit includes a battery controller which works as a boost and buck converter according to system requirements, along with a battery. On the MATLAB/Simulink platform, the control scheme and functioning of both controllers are tested, and the results are validated as satisfactory. According to IEEE 519, the grid current THD is below 5% when the suggested control system is implemented.

The extensive use of power electronics devices in power systems, including rectifiers and inverters, presents considerable issues regarding power quality. One problem is the creation of current and voltage harmonics, which result in load waveform distortion, voltage fluctuation, voltage drop, and equipment overheating. Harmonic current sources are prevalent in commercial, institutional, and medical establishments, encompassing computer power supplies, fluorescent lights with electronic ballasts, elevator motors, and electrical devices using switch-mode power supplies. Active power filters (APF) represent the most effective method for harmonic reduction and may be used across many applications. This study employs a digital active power filter to eliminate harmonics from the source current in a grid system characterized by non-linear demand. Nonlinear loads are essential components of every power system. The advent of power electronics has resulted in switching components constituting a substantial portion of electrical demand. These features create discontinuities in lines, exacerbating line losses and diminishing power quality and sine wave integrity. Passive filters effectively eliminate harmonics at specified frequencies within the design. Active filters, conversely, operate in accordance with the prevailing harmonics. This work develops a shunt active power filter that mitigates current harmonics generated by non-linear loads. The active filter includes a voltage source converter (VSC) that functions in conjunction with a DC coupling capacitor. The VCS delivers power at the point of common coupling (PCC). The reference current is obtained by the instantaneous power theory. The instantaneous power theory, or PQ theory, has been enhanced with the FIS control system to optimize DC voltage generation over the DC link capacitor. The fuzzy system substituting the PI controller has a 49-rule base structure organized in a 7x7 configuration for the generation of error signals. A comparative study of DC voltage and total harmonic distortions (THDs) is conducted using MATLAB software and the FFT analysis tool..

Renewable energy source (RES) production has increased nowadays due to the depletion of fossil fuel reserves and the rise in greenhouse emissions. Incorporating RES into the grid may produce additional problems in power quality, system stability, harmonics and reliability owing to their sporadic nature. The RES is capable of operating in both ON and OFF electrical grid modes since ON-grid power systems are linked to the utility grid, while off-grid systems are not. However, because of the environmental variability, it can be challenging to obtain optimal voltage and extract maximum RES power. It is crucial to derive an optimal solution to obtain the maximum power from RES. Therefore, this paper proposes a bat algorithm for tracking (BAT) with a quantum neural network (QNN) for extracting maximum power from a PV panel. The Bat Optimization Algorithm (BOA) is used to select optimal parameters for QNN. The suggested method is designed via MATLAB/Simulink, and various parameters are considered, in which total harmonic distortion (THD) and efficiency analysis of the proposed method with an ant lion optimized cuckoo search (ALO-CS) algorithm are compared. Simulation and hardware implementation results demonstrate superior performance compared to the ALO-CS method. The proposed approach achieves a peak efficiency of 93.6% in simulation and 93.4% in hardware, with convergence times of 0.1[Formula: see text]s and 0.16[Formula: see text]s, respectively. Harmonic distortion is significantly reduced, with THD values of 0.43% in simulation and 0.7% in hardware using a current control technique. These results confirm that the QNN-BOA method provides faster tracking, higher efficiency and better power quality than conventional maximum power point tracking (MPPT) techniques, making it highly suitable for hybrid RES applications.

This paper presents the concept of interconnection of Solar Photovoltaic (SPV) power generating system using Synchronous Reference Frame (SRF) theory based control in indirect current control mode of operation. This proposed theory improves the power factor and voltage at point of common coupling (PCC). Voltage at PCC is maintained through reactive power compensation. The whole power generating system consists of SPV system, dc-dc boost converter, maximum power point tracking (MPPT), voltage source converter (VSC), ripple filter, different types of loads, interfacing inductor and three phase grid. This system eliminates harmonic currents and load balancing is also possible using it. The grid-interconnected SPV system is tested for two modes i.e. unity power factor mode of operation and voltage regulation mode, with load balancing problems of linear loads.

This paper deals with the adaptive estimation of frequency observation (AEFO) based technique for compensating the harmonics component of two-stage grid-connected solar photovoltaic (PV) system. The maximum PV power is extracted using maximum power point tracking (MPPT) algorithm. Moreover, the input DC voltage of the voltage source converter (VSC) is maintained at desired level using a proportional integral (PI) controller. The AEFO control injects the required reactive component, which shapes the balanced grid currents. Moreover, the active power is injected in to the grid, which eliminates the harmonics in the grid currents. Using this controller, the fundamental reference currents are estimated using nonlinear load currents. This system maintains the grid current total harmonic distortion (THD) in accordance to the IEEE 519 standard. The dynamic response is improved by adding the PV feed-forward term with the estimated magnitude of i eα and i eβ current quantities. This control improves the dynamic response when insolation is changed and also provided a good response when switched from PV array to DSTATCOM and vice versa. Moreover, the power quality issues such as load unbalancing, power factor correction and reduced the grid side currents harmonics. Test results has shown the reactive power compensation of balanced and unbalanced nonlinear loads and the steady-state and dynamic performances of the system and PV array to DSTATCOM and vice-versa.

This paper deals with a three-phase two-stage grid tied SPV (solar photo-voltaic) system. The first stage is a boost converter, which serves the purpose of MPPT (maximum power point tracking) and feeding the extracted solar energy to the DC link of the PV inverter, whereas the second stage is a two-level VSC (voltage source converter) serving as PV inverter which feeds power from a boost converter into the grid. The proposed system uses an adaptive DC link voltage which is made adaptive by adjusting reference DC link voltage according to CPI (common point of interconnection) voltage. The adaptive DC link voltage control helps in the reduction of switching power losses. A feed forward term for solar contribution is used to improve the dynamic response. The system is tested considering realistic grid voltage variations for under voltage and over voltage. The performance improvement is verified experimentally. The proposed system is advantageous not only in cases of frequent and sustained under voltage (as in the cases of far radial ends of Indian grid) but also in case of normal voltages at CPI. The THD (total harmonics distortion) of grid current has been found well under the limit of an IEEE-519 standard.

This paper deals with a three phase multifunctional grid connected SECS (Solar Energy Conversion system). A two stage power circuit topology is used in this work, in which the first stage is a boost converter, which serves the purpose of MPPT (Maximum Power Point Tracking) and the second stage is a 4-leg VSC (Voltage Source Converter) which serves the purpose of feeding extracted energy along with power quality improvement in the distribution system. The SECS not only feeds solar PV (Photo-Voltaic) energy into the grid but also serves purpose of grid currents balancing, reactive power compensation, harmonics elimination and neutral current mitigation. A feed-forward term for the solar contribution is used to improve the dynamic response for climatic changes. The PV array voltage is continuously adjusted with the help of boost converter to achieve MPPT whereas the DC link voltage of VSC is kept constant with the help of a PI (Proportional-Integral) controller. A SOGI-Q (Second Order Generalized Integrator - Quadrature) based algorithm is proposed for control of four-leg VSC. The system is modeled and simulated on MATLAB based platform. A wide range of simulation results are shown to demonstrate all features of proposed system. The simulation results show the feasibility of the proposed control algorithm. The THD (Total Harmonics Distortion) of grid current has been found well under IEEE-519 standard.

Over the last decades, the deployment of large solar-based photovoltaic power plants has grown tremendously. The undesirable impact of high integration level of photovoltaic systems has led energy stakeholders to regulate such penetration to avoid this negative impact. One major concern with regard to photovoltaic penetration is the issue of power quality. Poor power quality can be a source of system disturbance and major economic losses. However, the power quality analysis is not widely discussed in the literature, with most of the studies focusing on the harmonic issues as potential power quality problem, but this study shows that there are a number of power quality issues, such as undervoltage, overvoltage, power fluctuation, and power factor. This study presents practical approaches to a grid-connected solar photovoltaic plant with associated control circuits developed in the time-domain. The power quality of a grid-connected solar photovoltaic plant is investigated by an analysis of the inverter output voltage and nominal current for different photovoltaic plant sizes. Also, the effect of different conditions of solar irradiance and ambient temperature on the power quality is analyzed. To identify power quality issues, a photovoltaic plant time-domain model is developed using Power Systems Computer Aided Design software. Various solar photovoltaic plant controls such as maximum power point tracking and modulation signals sinusoidal pulse width modulation and pulse width modulation for direct current-to-direct current boost converter are developed and integrated into the simulation environment. Several case studies are performed taking into account different photovoltaic plant ratings such as 250 kW–3 MW, where the point of common coupling is monitored.

A microgrid is key to an efficient and resilient power grid operation. Thus, in this paper, a robust control scheme is implemented namely a modified frequency locked loop (MFLL), proficient in eliminating the voltage and current fluctuations because of phase/frequency variation. Therefore, enhancing the consistency of the supply across local nonlinear load through a smooth transition from utility-interactive mode to islanded mode. It also achieves accelerated convergence and reduced steady-state error. MFLL is an easy control technique, with only one interfacing voltage source converter, which delivers a stable supply to critical loads during different operating modes. The implemented system has the main advantage of the capability of power-sharing between distributed generation (DG) systems while regulating the voltage at the DC link. It also provides power quality improvement through harmonics suppression; voltage regulation during contingencies like unbalance in load and compensation in reactive power at the common coupling point following the prerequisite of the system. Performance through the implemented control algorithm is brought within MATLAB 15b/Simulink platform and validated through experimental results. Performances are compared with already reported control strategies. Thus, simulated results comparison with existing work presents the competence of the implemented control strategy under dynamic conditions.