Integrated standalone hybrid solar PV, fuel cell and diesel generator power system for battery or supercapacitor storage systems in Khorfakkan, United Arab Emirates

In this paper, a disturbance observer-based fuzzy sliding mode control (DOBFSMC) strategy is proposed for a single-phase PV grid-connected inverter. In the fact that the uncertainties caused by the inverter component parameter variations and the changes of climatic conditions may seriously affect the control performance of the inverter, a disturbance observer is designed to estimate these disturbances in real time and a sliding mode controller designed with the output information of the disturbance observer is employed to control the output voltage of the DC–AC inverter, and a fuzzy system is used to approximate the upper bound of the observation error between the actual disturbance and its observation value in order to improve the performance of the control system. The inverter has strong robustness since the disturbances can be adaptively compensated, and the chattering is greatly reduced since the switching gain can be very small as the upper bound of observation error is estimated by the fuzzy system. Finally, simulation results verify the effectiveness of the proposed method and demonstrate it can work reliably under different conditions.

Disturbance Observer Based Fuzzy Sliding Mode Control of PV Grid Connected Inverter

Optimal selection and management of hybrid renewable energy System: Neom city as a case study

High-voltage direct current (HVdc) transmission systems based on modular multilevel converters (MMCs) are a promising solution for efficient bulk power transmission over long distances. As in grid-connected converters, the occurrence of grid-side faults is rather common, leading to imbalances and distortions of the ac-side voltages. Therefore, operation and control of MMC-HVdc systems under grid imbalances become of great significance in order to satisfy grid codes and reliability requirements of the system. The aim of this paper is to provide a comprehensive review of operation and control methods applied to MMC-HVdc systems with a specific focus on unbalanced ac-grid conditions. The methods are classified based on their main control targets that include ac-side power control, control of the circulating current, and dc-side power ripple suppression control. Special attention is given to the comparison of the different control methods and specific requirements under certain operating conditions that include grid, load, or internal imbalances.

Operation and Control Methods of Modular Multilevel Converters in Unbalanced AC Grids: A Review

The high integration of photovoltaic power plants (PVPPs) has started to affect the operation, stability, and security of utility grids. Thus, many countries have established new requirements for grid integration of solar photovoltaics to address the issues in stability and security of the power grid. In this paper, a comprehensive study of the recent international grid codes requirement concerning the penetration of PVPPs into electrical grids is provided. Firstly, the paper discusses the trends of PVPPs worldwide and the significance of improving grid codes' requirements. In addition, the comparison of common requirements covered in the majority of international grid codes considers high‐ and low‐voltage ride‐through capabilities, voltage and frequency regulation, and active and reactive power support requirements. Finally, a broad discussion on the compliance technology challenges and global harmonization of international grid codes that the PVPPs have to address is presented. The study summarizes the most recent international regulation regarding photovoltaic integration and research findings on the compliance of these regulations and proposed recommendations for future research. It also can assist power system operators to compare their existing requirements with other universal operators or establish their own regulations for the first time. Additionally, this research assists photovoltaic manufacturers and developers to get more accurate understanding from the recent global requirements enforced by the modern grid codes.

Grid‐connected photovoltaic power plants: A review of the recent integration requirements in modern grid codes

A robust feedback linearizing control strategy, based on sliding mode compensation, is proposed for the operation of a grid-connected photovoltaic inverter system under grid faults, characterized by unbalanced voltages, to meet low-voltage ride through requirements. Under normal grid condition, the control system is developed for maximum power transfer from the photovoltaic source to the grid by maximum power point tracking operation of the dc–dc converter, and regulation of the dc-link voltage and the current at the inverter-grid side. Under grid fault, which is unbalanced grid voltage due to voltage dips, the active power is regulated to reduce the current excess and the reactive power is injected to avoid the inverter damage or disconnection, while the dc-link voltage is controlled via the dc–dc converter. A sliding mode compensator is injected into the control system to enhance its robustness to uncertainties. The feedback linearizing control schemes are developed from the grid model at the inverter side and the dc-link model at the dc–dc converter side. The proposed control strategies are experimentally validated on a three-phase grid-connected photovoltaic inverter system and experimental results show that the control system is effective in terms of voltage and power control with smooth transitions between the modes.

Robust Feedback Linearizing Control With Sliding Mode Compensation for a Grid-Connected Photovoltaic Inverter System Under Unbalanced Grid Voltages

In this paper, the integration of photovoltaics into distribution power systems with grid fault ride-through capability is investigated by proposing a robust model predictive control scheme. The control system is developed in normal conditions. It regulates the constant dc-link voltage, and it also provides the maximum power transfer to the grid by controlling unity power factor. During grid abnormality, the control system is reorganized to maintain a constant dc-link voltage, prevents the active power and injects a reactive power to support the grid operation. The model predictive control scheme is derived from the dc-link and the grid models. The proposed control scheme is experimentally validated using a hardware prototype of the photovoltaic system connected to an emulated three-phase grid. Experimental results show that the proposed controller is able to provide dc-link voltage regulation, while curtailing the active power during grid abnormalities. Moreover, the controller is able to support the grid under such conditions. The control scheme is quite robust against unknown disturbances and parametric uncertainties in the system.

Robust Model Predictive Control for Photovoltaic Inverter System With Grid Fault Ride-Through Capability

The authors propose, design, and implement a low-cost universal smart energy meter (USEM) with demand-side load management. The meter can be used in the postpaid and prepaid modes with flexible tariff plans such as time of use, block rate tariff, and their combination. The smart meter comprises of a potential transformer, current transformer, and microcontroller unit with an embedded communication module. The connectivity among the utility authority, the smart meter, and consumer is established by authority identification number, meter identification number, and user identification number using the cellular network. The load management option of the meter controls electrical loads and provides emergency power during the power shortage. The USEM can be configured and reconfigured remotely simply by short message service without changing hardware. Besides, energy consumption status, meter tampering, and fault at the distribution end can be monitored with the proposed metering system. Here, a prototype of the smart meter is presented, and its effectiveness, flexibility, and versatility are experimentally demonstrated.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-gtd.2016.1852

Labib Labib

Papers

Robust Feedback Linearizing Control With Sliding Mode Compensation for a Grid-Connected Photovoltaic Inverter System Under Unbalanced Grid Voltages

Robust Model Predictive Control for Photovoltaic Inverter System With Grid Fault Ride-Through Capability

Design and implementation of low-cost universal smart energy meter with demand side load management

Dual-mode operation based second-order sliding mode control for grid-connected solar photovoltaic energy system

Design and implementation of a fractional nonlinear synergetic controller for generator and grid converters of wind energy conversion system