Grid Synchronization Research Articles

Design of Z source converter with the genetic-based chicken swarm algorithm for closed loop control of PV integrated grid

A single-phase grid coupled PV system with a switched Z-source boost converter is analysed on the basis of closed-loop control using a novel hybrid algorithm. As PV results in low-voltage DC, it is vital to step up this low-voltage DC and so a suitable DC-DC converter is needed. A switched Z-source boost converter is utilized for the step-up process as this converter uses minimum passive components, thereby reducing the cost with improved power density. Control of the converter is carried out by a closed loop control using a PI controller tuned with a novel genetic-based chicken swarm (GBCS) algorithm which combines the merits of both genetic and chicken swarm able to deal with complex problems, simple with fast convergence. The output of the converter is then given to the grid through a single-phase VSI in which DC–AC conversion takes place. While connecting PV to the grid, another factor to be taken care of is grid synchronization which is accomplished by a PI controller in which the actual and reference power are analogized. The proposed control scheme is simulated in a MATLAB environment and the outcomes are observed. The grid current THD of 1.6% and reactive power compensation is accomplished.

Extensive assessment of virtual synchronous generators in intentional island mode

Virtual Synchronous Generators (VSGs) are considered one of the most effective cutting-edge technologies for seamlessly integrating Renewable Energy Systems (RESs) into power grids. While various VSG control schemes have been proposed and analysed for different technical aspects, not many experimental demonstrations have been published about VSGs operating in Intentional Island Mode (IIM). Inversely, the IIM has become increasingly attractive, nowadays, to energize those remote areas of the world where entire districts are served by a small number of RESs operating off-grid. In this scenario, the main objective of this paper is to present an extensive performance assessment of the VSG operating in IIM. Different working conditions are considered, with special focus on: black start capability, grid-connected-to-IIM transition, grid reconnection, feeding of non-linear and asymmetric local loads, load sharing between multiple VSGs operating in parallel. In order to achieve this objective, an improved structure of VSG is implemented on 8kVA three-phase converters and significant experimental results are presented. Algorithms for black start capability and grid synchronization are illustrated in detail as well. Meaningful information is provided for engineers involved in activity of designing and testing islanded VSGs.

D-estimation method for grid synchronization of single-phase power converters: analysis, linear modeling, tuning, and comparison with SOGI-PLL

D-estimation method for grid synchronization of single-phase power converters: analysis, linear modeling, tuning, and comparison with SOGI-PLL

A novel DC‐link voltage synchronous control with enhanced inertial capability for full‐scale power conversion wind turbine generators

AbstractThe new power system is characterized by high penetration of renewable energy sources and a high proportion of power electronics (namely, double‐high). The grid‐forming control is an effective method to improve the grid‐connected stability of wind turbine generators (WTGs) in the “double‐high” grid. The control method based on the DC‐link voltage can effectively realize the grid‐forming control for WTGs. However, there is a disadvantage that the DC‐link voltage cannot be maintained at the given value. To address this, the grid synchronization mechanism of DC‐link voltage is explored and the specific implementation of a novel DC‐link voltage synchronous control applicable to full‐scale power conversion WTGs is proposed. Then, the boundary of the inertial coefficient is probed through the state‐space method. And a compensation control is proposed to enlarge the inertial response capability based on the mechanism of damping characteristics. Finally, the PSCAD/EMTDC simulation and RTLAB hardware‐in‐loop experiment show that the synchronization frequency can accurately map the grid frequency changes in real‐time under the premise that the DC‐link voltage remains constant. In addition, the inertial coefficient can be increased by more than five times with the compensation strategy, which can enhance the support capability of the WTGs to the power grid.

A flexible energy management for distributed energy supplied smart home in microgrid connection with grid‐connection/islanding mode functionality

AbstractIn this study, a flexible control approach is presented for smart home with DES system in microgrid connection. The smart home with DES has operation capability under GC‐Mode and I‐Mode functions with the proposed control algorithm. The control algorithm is also developed in terms of international standards IEEE 929 and IEC 61727 for grid connection requirements. Additionally, a PLL‐less control algorithm is embedded in the proposed control algorithm for the active/reactive power management and the grid synchronization. Thus, slow dynamic response and calculation burden issues in controller is avoided and the power flow capability of the grid‐connected DES in smart home is enhanced. Furthermore, the coordinate transformation is fulfilled for the power flow control in the control loop via the generation of cosine and sinus functions. Besides, the mathematical formulations of the proposed control algorithm are presented in detail. To show the effectiveness of the proposed control algorithm, a smart home with a photovoltaic DES model is designed and constructed in a simulation environment. The proposed control method is tested under various operation cases such as dynamic environmental conditions, GC‐Mode/I‐Mode, reactive power support and voltage variations. The proposed method shows efficient performance under applications of the different operation situations. Moreover, the international requirements are satisfied for GC‐Mode and I‐Mode transitions.

Advanced PLL structures for grid synchronization in distributed generation

The actual grid code requirements include specific demands for grid connected wind power generation facilities. The Transmission System Operators are specially concerned about the Low Voltage Ride Through requirements which are becoming more restrictive in terms of the admissible disconnection conditions, but also in the active/reactive power that wind farms should inject to the network under fault conditions to support the grid. Solutions based on the installation of STATCOMs and DVRs, as well as on advanced control functionalities for the existing power converters of wind power plants, have contributed to enhance their response under faulty and distorted scenarios, and hence to fulfill these requirements. However, in order to achieve satisfactory results with such systems it is necessary to count on accurate and fast grid voltage synchronization algorithms, able to work under unbalanced and distorted conditions. This paper analyzes the synchronization capability of three advanced synchronization systems: the DDSRF-PLL, the DSOGI-PLL and the 3phEPLL, designed to work under such conditions. In the following the different algorithms will be presented and discretized and finally their performance, as well as its computational cost, will be tested in an experimental setup controlled by a means of a TMS28335 floating point DSP.

Seamless disconnection and reconnection transients for Micro-Grids

The increasing penetration of generation power plants based on renewable energies in the electrical networks has boosted the number of systems connected to the grid. In this scenario the micro-grid, providing advanced functionalities to improve the stability and operation of the network, have become very popular. In this paper a control strategy for the micro-grid management is presented. The proposed system improves the performance of micro-grids and its interaction with the main network, or also with other micro-grids, under grid voltage transients. This technique gives rise to a simple and robust control scheme to ensure the appropriate micro-grid disconnection from the main grid. In the following, the control algorithm for the intelligent connection agent will be shown, and the grid synchronization system, as well as the voltage and current control loops will be detailed. Finally simulation results obtained using the MATLAB/Simulink & Psim platform will be presented and discussed

Power Quality Acquire of Intelligent Controller based Superior Gain Re-Lift Luo Converter Intended for PV Linked Microgrid Integration

Power converters-based renewable energy sources such as photovoltaic (PV) and wind energy are more popular for residential and commercial applications. Because, of their eco friendlessness and cost effective operation. A Re-Lift Luo Converter integrated with renewable sources to the utility microgrid along with Intelligent Controller strategies is proposed. The solar photovoltaic system provides voltage to the inverter through a Re-lift Luo converter. The Bidirectional Battery converter along with battery system is used to achieve energy control management for the proposed system. In this paper the grid synchronization with DSTATCOM devices controlled by PI controller with D-Q theory transformation is achieved. Under this work, DSTATCOM has been used to improve the power quality under different loading conditions. The LC filter is employed to develop the output of the inverter. The input of the PV and battery systems are DC bus power source, as well as AC power injected into the grid network. The obtained results indicate that proposed approach delivers better performance with superior efficiency and nominal harmonics. The entire proposed system is validated through a MATLAB simulation and Hardware experimental prototype.

Switched Z-Source Boost Converter in Hybrid Renewable Energy System for Grid-Tied Applications

The world's focus is shifting toward Renewable Energy Sources (RES) as a result of the sharp rise in energy demand and the depletion of conventional energy sources. Distributed generation (DG) units developed on RES are easily and reliably integrated into grid due to microgrid technology. Inverters are typically used to integrate DGs into microgrid. At present, the fastestgrowing renewable sources of electricity in the world is photovoltaic (PV) and wind energy conversion system (WECS), which evolved in response to growing environmental concerns about the risks of climate change connected with power generation. Recent technological developments have made it a top priority for researchers to find ways to enhance the efficiency of hybrid systems and the power converter stage. In order to achieve transmission losses and ensure energy savings, a new 13-bus system is developed in this work for regulating the output voltage in distribution networks. Switched Z-source Boost converter along with Proportional Integral (PI) controller is employed to boost the voltage obtained from PV system. A battery converter along with a bi-directional battery is connected to the DC link, to store energy generated by Hybrid Renewable Energy System (HRES) in excess amount. The obtained DC link voltage is transferred to three-phase voltage source inverter (VSI) for the conversion of DC to AC voltage. Effective harmonic reduction is attained with the aid of LC filter coupled to Three phase grid, and the PI controller associated to the grid supports in achieving effective grid synchronization. The proposed research is validated using MATLAB Simulink by considering the 13-bus system and an efficiency of 96.8 % is obtained with 0.93% Total Harmonic Distortion (THD).

The Significance of the Digital Frequency Relays in Grid Synchronization Maintenance

Modeling tools play a crucial role in both educational and industrial settings, enabling engineers to simulate power systems under various operating conditions, including normal and faulty scenarios. This research focuses on the design of a relay system capable of addressing both over and under frequency conditions. Digital relays exhibit distinct advantages over traditional electromechanical relays, notably in terms of accuracy and response speed. The significance of frequency control cannot be overstated, as significant fluctuations can potentially lead to complete power system blackouts. Historical incidents have demonstrated the severe consequences of frequency instability, often stemming from supply-demand imbalances and unforeseen contingencies. With the rise of distributed generation and the inherent challenges of islanding in modern power systems, the attention of both industrialists and researchers has once again turned to frequency relaying solutions. This study aims to evaluate the performance of the proposed digital frequency relay under diverse system dynamics using simulation tools such as MATLAB/Simulink and microcontroller-based implementations. By conducting rigorous testing and analysis, this research endeavors to contribute to the enhancement of grid stability and the prevention of power system disruptions caused by frequency deviations.

Simple solution of DC-offset rejection based phase-locked loop for single-phase grid-connected converters

Distributed Generators (DG) systems based on Renewable Energy Sources (RES) such as hydro, wind, and solar power plants have been spread widely due to their lower cost and the advanced capability of connecting them with the grid. The power generated from the DG must be shaped to be interfaced with the grid employing power electronics converters. The grid-connected power electronics converters must be synchronized with the grid (i.e., the same fundamental component of the grid frequency, phase, amplitude, and sequence). Synchronization techniques are employed to achieve accurate and fast grid synchronization between the converter and the grid. The existence of (DC-offset) in the input of Phase Locked Loop (PLL) caused synchronization problems as it causes oscillations in the estimated fundamental grid phase, frequency, and amplitude. In addition, the closed-loop system stability can be affected. This work proposes a simple technique for grid synchronization based on PLL with a phase angle correction. The proposed method was developed using Transfer Delay (TD) and Delay Signal Cancelation (DSC) operators; then, the small single model and stability analysis was employed. Several scenarios were developed to compare the proposed method with previous methods using MATLAB/Simulink tool. The scenarios involve introducing phase jumps, DC offsets, and amplitude changes to the grid voltage. Additionally, the grid frequency was also changed. The results show that the proposed PLL can solved the DC-offset problem using any delay time and fully synchronized with the grid. Moreover, the proposed PLL has the fastest dynamic response and shortest synchronization time over the other methods from literature.

Synchronization of Grid Connected Three Phase Inverter

Synchronization of Grid Connected Three Phase Inverter

A Grid Synchronization PLL With Accurate Extraction Technique of Positive/Negative Sequences and DC-Offset Under Frequency Drift

A Grid Synchronization PLL With Accurate Extraction Technique of Positive/Negative Sequences and DC-Offset Under Frequency Drift

Grid Synchronization Control for Grid-connected Voltage Source Converters Based on Voltage Dynamics of DC-link Capacitor

Grid Synchronization Control for Grid-connected Voltage Source Converters Based on Voltage Dynamics of DC-link Capacitor

Application of an Enhanced Generalized Integrator Based Control for an Emission-Free Marine Microgrid with Shore Grid Synchronization

Application of an Enhanced Generalized Integrator Based Control for an Emission-Free Marine Microgrid with Shore Grid Synchronization

Enhancing Solar PV Performance: Advanced Converters for Efficient Green Energy Conversion and Grid Compatibility

This paper delves into the vital role of converters in enhancing the efficiency and reliability of solar photovoltaic (PV) systems. With the escalating demand for renewable energy sources, solar PV systems emerge as a sustainable solution, necessitating advanced power electronics for optimal performance. The study highlights various DC-DC converters, such as buck, boost, and buck-boost converters, analyzing their functionalities in achieving maximum power point tracking (MPPT) and their implications on system cost, efficiency, and limitations. Further examination of gridconnected PV systems underscores the necessity for sophisticated inverter designs to ensure high efficiency, minimal harmonic distortion, and effective power management. Through MATLAB SIMULINK simulations, the paper evaluates the performance of solar PV systems equipped with different converter and inverter configurations, addressing the challenges posed by power fluctuations and the integration of solar energy into the grid. The research contributes to the ongoing discourse on renewable energy integration, presenting innovative solutions for grid synchronization, voltage regulation, and harmonic distortion reduction in solar PV systems.

Dual Grid-Forming Control With Energy Regulation Capability of MMC-HVDC System Integrating Offshore Wind Farms and Weak Grids

To integrate weak onshore grids, some grid forming (GFM) control schemes taking advantage of DC voltage synchronization have been proposed for modular multilevel converter-based high-voltage direct current (MMC-HVDC) systems. In these control schemes, the sub-module (SM) capacitor energy is only used for grid synchronization. Since the SM capacitor is an energy storage device, it has the potential to actively regulate the stored energy. To fully exploit the energy management capability of MMC, a dual grid forming control scheme with energy regulation capability is presented in this paper. The proposed control scheme enables grid forming for both onshore and offshore MMC stations. Meanwhile, the capacitor energy of MMCs can be flexibly regulated to provide frequency support for the onshore grid. To verify the effectiveness of the proposed control scheme, case studies are first carried out in a point-to-point offshore wind farms (OWFs) integrated HVDC system. In addition, the frequency support performance is evaluated in a 3-area 4-machine grid integrated with two OWFs-HVDC systems. Finally, a single-terminal three-phase MMC prototype is developed to test the voltage decoupling and energy management capabilities of the proposed control strategy.

Power quality disturbance mitigation in grid connected photovoltaic distributed generation with plug-in hybrid electric vehicle

In the last twenty years, electric vehicles have gained significant popularity in domestic transportation. The introduction of fast charging technology forecasts increased the use of plug-in hybrid electric vehicle and electric vehicles (PHEVs). Reduced total harmonic distortion (THD) is essential for a distributed power generation system during the electric vehicle (EV) power penetration. This paper develops a combined controller for synchronizing photovoltaic (PV) to the grid and bidirectional power transfer between EVs and the grid. With grid synchronization of PV power generation, this paper uses two control loops. One controls EV battery charging and the other mitigates power quality disturbances. On the grid connected converter, a multicarrier space vector pulse width modulation approach (12-switch, three-phase inverter) is used to mitigate power quality disturbances. A Simulink model for the PV-EV-grid setup has been developed, for evaluating voltage and current THD percentages under linear and non-linear and PHEV load conditions and finding that the THD values are well within the IEEE 519 standards.

Machine learning based cascaded ANN MPPT controller for erratic PV shading circumstances

Power generation is challenged to meet energy demand during peak hours. As a result of limited non-renewable energy resources, power utilities heavily rely on fossil fuels. Therefore, scientists and researchers are looking for some distributed generators to provide additional power during peak hours. During such period, load demand is solved using solar power. As a consequence, grid-connected solar Photovoltaic (PV) systems are catching the attention owing to their ability to significantly reduce the use of fossil fuels. Under Partial Shading Condition (PSC), this paper utilizes Luo Converter along with Cascaded Artificial Neural Network (ANN), which is a Machine Learning Based Maximum Power Point Tracking (ML-MPPT) approach for tracking optimal power from PV system. The gained DC supply is converted into AC voltage using VSI attached to the system. In addition, PI controller engaged controls the voltage at grid side and results in effective grid synchronization. Furthermore, MATLAB Simulink analysis is carried out and the outcomes reveal the effectiveness of proposed system with 98% efficiency under different PV circumstances.

Model Predictive Control for Matrix Converters in Grid-Interactive Applications

Model Predictive Control (MPC) is a promising control strategy for matrix converters in grid-interactive applications. MPC optimizes a cost function over a finite time horizon, considering system constraints like voltage and current limits, grid codes, and power factor requirements. This enables effective grid synchronization, power quality regulation, and efficient power conversion. Advancements in MPC include predictive modelling techniques, adaptive algorithms, optimization algorithm integration, hybrid control strategies, and multi-objective optimization formulations. Benefits include fast response to changes in grid conditions, robustness in handling uncertainties, and extended time-horizon optimization. This study provides insights into MPC techniques and highlights the potential for further research.