Search

As a result of the increasing penetration of renewables in power systems, wind farms (WFs) have to satisfy the low-voltage ride-through (LVRT) requirement to stay connected to the power grid under fault conditions. This study proposes a novel method that uses the static synchronous compensator (STATCOM) to improve the LVRT capability of WFs during grid faults. The proposed method is based on the Taguchi method which involves orthogonal experiments. The allocation (locations and sizes) and fuzzy control gains of STATCOM are determined by the analysis of mean (ANOM) technique as part of the Taguchi method to achieve a robust design that is insensitive to variations of operating conditions and faults. The optimal STATCOM that is obtained by the proposed method is validated in both a single WF-infinite bus power system and the IEEE 39-bus power system. The simulation results show that the proposed method can enhance the LVRT capability of WFs. [ABSTRACT FROM AUTHOR]

As a result of the increasing penetration of renewables in power systems, wind farms (WFs) have to satisfy the low‐voltage ride‐through (LVRT) requirement to stay connected to the power grid under fault conditions. This study proposes a novel method that uses the static synchronous compensator (STATCOM) to improve the LVRT capability of WFs during grid faults. The proposed method is based on the Taguchi method which involves orthogonal experiments. The allocation (locations and sizes) and fuzzy control gains of STATCOM are determined by the analysis of mean (ANOM) technique as part of the Taguchi method to achieve a robust design that is insensitive to variations of operating conditions and faults. The optimal STATCOM that is obtained by the proposed method is validated in both a single WF‐infinite bus power system and the IEEE 39‐bus power system. The simulation results show that the proposed method can enhance the LVRT capability of WFs. [ABSTRACT FROM AUTHOR]

The popularity of electric springs (ESs) has been grown in the last years mainly due to the boost in the growth of smart grids (SGs) and micro‐grids (μGs), as well as the high penetration of renewable energy sources. In general, ESs have a hardware structure similar to other compensator devices such as distributed flexible AC transmission systems or active filters. ESs offer the exchange of active and reactive powers with the electrical grid and the demand‐side load management. Their ability to simultaneously perform multiple tasks without the need of modifying their hardware structure classifies them as smart loads, distinguishing them from other types of compensators such as active filters, hybrid filters, dynamic voltage restorers, and distribution static VAR compensators, among others. In this work, an exhaustive review of ESs is carried out to cover their three main research trends, i.e. hardware structure evolution, different types of controllers, and applications in electric power distribution systems, SGs, and μGs. Moreover, their main advantages, disadvantages, and contributions in the power quality improvement are discussed. This review clarifies future research trends that have to be explored to advance the subject. [ABSTRACT FROM AUTHOR]

Integrated photovoltaic (PV) distribution systems voltage stability is of great significance in supporting all connected equipment smooth functioning in the distribution network. Voltage profile maintenance is one of the challenging tasks in PV integration. To maintain a constant voltage profile to a sensitive load of 22 kVA is the main idea of this study. A single‐phase PV‐integrated distribution system is selected for the study. The novelty is that differential inverters are used for dynamic voltage restorer and distribution static synchronous compensator of the unified power quality conditioner (UPQC). Active power decoupling facility is the main advantage using the differential inverter. The research work objective is to synchronise a 10 kW solar PV system to the distribution system using this new UPQC. The research work discusses and derives the most suitable control strategy for the UPQC with battery energy storage system. A 20 kVA UPQC is designed for the PV integration and to increase voltage stability of the distribution system. The frequency, voltage and reactance/resistance ratio of the distribution system is assumed to be constant. A prototype model of differential UPQC is developed. Experimental and simulation results validate the main objective. [ABSTRACT FROM AUTHOR]

This study presents a single stage grid‐interfaced solar photovoltaic (SPV) system using a multifunctional complex coefficient reduced ordered generalised integrator (CC‐ROGI) based frequency‐locked loop (FLL) control. The main contributions of this study, include (i) the extrication of fundamental active components from load currents using CC‐ROGI‐FLLbased control to generate the reference grid currents for voltage source converter (VSC) switching, (ii) VSC works as a distribution static compensator, which performs multi‐functions like harmonics mitigation, reactive power compensation, unity power factor operation and grid currents balancing, (iii) this CC‐ROGI‐FLL also extricates the fundamental grid voltages component even under grid voltage harmonic distortion and grid voltages unbalancing. Moreover, SPV power feed‐forward component is assimilated in this control to reduce the oscillations in grid currents under variable irradiance. Simulated and experimental results show satisfactory behaviour of the system at different conditions like load unbalancing, variable solar irradiance and abnormal grid conditions. The comparative performance of CC‐ROGI‐FLL control with other FLL and phaselocked loop controls are shown in this study. This CC‐ROGI‐FLL control has manifested a good steady state performance and dynamic response. The total harmonic distortions of grid currents are found well within the limits of the IEEE‐519 standard, even under abnormal grid conditions. [ABSTRACT FROM AUTHOR]

This study investigates the mitigation of transient overvoltages (TOVs) in a microgrid supplied by renewable distributed generation resources, which include photovoltaic (PV) generators, hydro generation unit, and wind power generators. ATP/EMTP is used in this study as electromagnetic transient software. Accurate simulation models are needed to carry out the study. Therefore, a three‐phase PV system model based on the equivalent Newton–Raphson circuit is used, and the efficiency of the PV system components is studied. Then, the use of the PV generation system model for switching studies is investigated using two different electrical systems. The use of different mitigation methods for TOVs at the microgrid is investigated. Three different mitigation methods are considered. First, a device to compensate reactive power such as static var compensator (SVC) is represented as a TOVs mitigation method. Then, adding a supercapacitor as TOVs mitigation method is evaluated. After that, a combination of active and reactive power simultaneously to mitigate TOV, by the addition of SVC to a supercapacitor, is investigated. The grid‐connected mode and isolated mode of the microgrid are considered. The results show that the usage of SVC with supercapacitor has the ability to mitigate the transient overvoltage and the waveforms are more regular. [ABSTRACT FROM AUTHOR]

A multi-microgrid (MMG) system comprises of a group of self-sufficient microgrids capable of operating in grid-connected, islanded, or interconnected modes. A three-microgrid-based MMG system consisting of a solar photovoltaic system, doubly-fed induction generator-based wind generation, and static synchronous compensator as distributed energy sources are considered. Each microgrid includes a battery interfaced with a bidirectional DC–DC converter. As there are multiple battery units in the MMG system, different states-of-charge (SoC) are evident in the batteries. Hence, there is a need to charge/discharge by following the SoC of the batteries. In this study, an intelligent scheme employing fuzzy logic is applied to monitor the SoC of the batteries and determine the reference current for current control through the bidirectional DC–DC converter in an MMG system. Microgrid frequency control in the MMG system is carried out using the proposed five-membership function-based fuzzy logic control. During sudden transient events, the proposed intelligent frequency control strategy shows an improved transient response as compared to conventional PI control. A multi-input and multi-output fuzzy logic-based power management algorithm is proposed to handle multiple sources, batteries, and loads in the system. The MMG system with the proposed control is simulated using real-time digital simulator OP4510 from OPAL-RT. [ABSTRACT FROM AUTHOR]

A multi‐microgrid (MMG) system comprises of a group of self‐sufficient microgrids capable of operating in grid‐connected, islanded, or interconnected modes. A three‐microgrid‐based MMG system consisting of a solar photovoltaic system, doubly‐fed induction generator‐based wind generation, and static synchronous compensator as distributed energy sources are considered. Each microgrid includes a battery interfaced with a bidirectional DC–DC converter. As there are multiple battery units in the MMG system, different states‐of‐charge (SoC) are evident in the batteries. Hence, there is a need to charge/discharge by following the SoC of the batteries. In this study, an intelligent scheme employing fuzzy logic is applied to monitor the SoC of the batteries and determine the reference current for current control through the bidirectional DC–DC converter in an MMG system. Microgrid frequency control in the MMG system is carried out using the proposed five‐membership function‐based fuzzy logic control. During sudden transient events, the proposed intelligent frequency control strategy shows an improved transient response as compared to conventional PI control. A multi‐input and multi‐output fuzzy logic‐based power management algorithm is proposed to handle multiple sources, batteries, and loads in the system. The MMG system with the proposed control is simulated using real‐time digital simulator OP4510 from OPAL‐RT. [ABSTRACT FROM AUTHOR]

The variable step size modified least mean square (VSSMLMS) learning algorithm based multifunctional double‐stage grid interactive photovoltaic (PV) system is implemented in this paper which feeds power to the grid and the load, ensures unity power factor operation and compensates reactive power. Along with this, it mitigates high grid neutral current during unbalanced loading condition. This algorithm uses variable step sizes to have a smooth dynamic and steady state performances. The boost converter (booster) is used in the first stage to extract peak power from a PV array using perturb and observe peak power point tracking technique. Next to this, a four leg voltage source converter (VSC) is placed to interlink the solar PV system to the grid and the loads. VSSMLMS‐based control technique is used to filter the fundamental component of load current and hence gate pulses are generated for the four‐leg VSC. This system is simulated in SIMULINK/MATLAB software under several working conditions and the obtained simulation results are validated on a developed laboratory prototype. The performance of the VSSMLMS‐based control technique is compared with that of the traditional LMS‐based technique. All results validate the IEEE‐519 standard. [ABSTRACT FROM AUTHOR]

In this study, a double fundamental signal extracter using third‐order signal integrator‐based control technique is used for the improvement of power quality of single phase grid interfaced with hybrid wind energy generation system (WEGS) and solar photovoltaic (PV) array under weak grid conditions. The control algorithm is proposed for the extraction of dual fundamental components of load current and to extract fundamental grid voltage for synchronisation to the grid. The main objective of the system is to establish secure, reliable and safe integration while mitigating several power quality issues such as total harmonic distortion (THD) of the grid current, DC current injection. The system operates in distribution static compensator mode in the absence of renewable energy sources and also, maintains the grid current THD as per the limit of the IEEE‐519 standard. For optimal power extraction from WEGS as well as the solar PV array, perturb and observe algorithm is used. The prototype developed in the laboratory is tested under different operating conditions such as variable wind speed, grid voltage sag/swell, variable solar insolation, and varying load conditions. [ABSTRACT FROM AUTHOR]

In this study, a ring‐type multi‐microgrid (MG) system comprising of three MGs with solar energy‐based generation, wind energy‐based generation, and static synchronous compensator as primary sources along with batteries as emergency back‐up is proposed. The voltage‐source converters at the individual MG level serve as the interface between the neighbouring MGs and the grid. An augmented proportional sliding‐mode‐control‐based approach is proposed in the primary control level to improve the power quality of the system during balanced and unbalanced loading conditions. A negative‐sequence controller is also included to mitigate the negative‐sequence voltage from the inverter output voltage. The multi‐MG (MMG) system is capable of operation in grid‐connected, islanded, or interconnected mode with balanced and unbalanced loads. The bidirectional DC ‐DC converters interfacing the batteries at the DC link is controlled by a hysteresis‐function‐based sliding‐mode control. A comparison of the proposed inverter primary control with proportional ‐integral controller, quasi‐proportional ‐resonant controller, and hysteresis‐band current controller is carried out. The comparison reveals that the total harmonic distortion and voltage unbalance factor improves by employing the proposed control when compared with conventional control. The proposed MMG system with its control strategies is modelled in MATLAB/Simulink environment and is experimentally verified using OP4510 from OPAL‐RT. [ABSTRACT FROM AUTHOR]

The static synchronous compensator (STATCOM) has attracted considerable attention because it can stabilise severe transients that are caused by power system disturbances. This study presents a novel interval type 2 fuzzy control system (IT2‐FCS)‐based controller for the STATCOM to stabilise bus voltages that are caused by faults or forced wind farm outages in a smart grid. Two IT2‐FCSs are presented to tune increments of the proportional integral (PI) controller, which are optimised by the gradient descent method. The IT2 fuzzy rules, involving upper and lower membership functions, result in a fast and stable system response. Since many possible scenarios may arise in the power system, the Taguchi method is used to design experiments using an orthogonal array, in which all scenarios are mutually independent. A power system that consists of a wind farm and STATCOM is studied. Comparative studies show that the proposed method is superior to traditional PI and type 1 FCS methods. [ABSTRACT FROM AUTHOR]

Local latency adversely affects the stabilising performance of damping controllers especially in the two‐level control scheme. By considering both wide area and local latencies, this study presents the two‐level coordinated control which consists of wide area centralised and local controls of power oscillation damper (POD) and power system stabiliser (PSS) for robust power oscillation damping. The PODs are equipped with the doubly fed induction generator (DFIG) wind turbine, the solar photovoltaic generator (SPV), and the static VAR compensator (SVC). The centralised PODs of DFIG, SPV, SVC, and the centralised PSSs act as the primary damping controllers. When the communication failure occurs, the local PODs of such devices and the local PSSs are activated and used as the backup damping controllers. To achieve the damping performance and robustness, the parameters of centralised and local controllers are individually optimised based on the worst scenarios determined by the lowest damping ratio of target inter‐area oscillation modes. Study results in New England and New York IEEE 68‐bus system demonstrate that the proposed two‐level coordinated controllers are superior to the conventional two‐level controllers in terms of damping performance and robustness against various operating conditions. [ABSTRACT FROM AUTHOR]

An adaptive damping control scheme based on classification and regression tree (CART) using wide‐area signals is proposed in this study. A family of robust controllers is designed off‐line and are used in real‐time after the corresponding operating point is retrieved from phasor measurement unit (PMU) data with CART interpolation. When the power system is operating precisely at a pre‐selected operating point, only the corresponding controller is active. When the power system is not exactly at the operating point, a combined controller is formed for damping. A 68‐bus, 16‐generator system is used as a test system. A thyristor‐controlled series capacitor, a static var compensator and an energy storage device are used as actuators, and remote PMUs frequencies as added inputs are employed as the example control. The simulation results demonstrate the effectiveness and robustness against the wider range of operating changes even without knowing precisely the model of disturbances that occurred in the dynamic system. [ABSTRACT FROM AUTHOR]

Wind shear and tower shadow produce a periodic pulse reduction in mechanical torque captured from wind energy resulting in wind energy conversion system (WECS) active power oscillations. In this study, an adaptive neuro‐fuzzy controller for static VAR compensator, used in power networks integrated with WECS, is presented to address the torque oscillation problem. The proposed controller consists of a radial basis function neural network representing a third‐order auto‐regressive and moving average system model and performing the prediction, and a main controller with adaptive neuro‐fuzzy inference system providing the damping signal. A modified two‐area four‐machine power network with WECS integration is applied to validate the proposed implementation, compared with conventional lead/lag compensation. Time‐domain simulations prove that the proposed controller can provide a damping signal to improve the active power oscillation and system dynamic stability, influenced by torque oscillations under WECSs synchronised operating condition. [ABSTRACT FROM AUTHOR]