This study presents a comprehensive review of the ocean wave technology and prospects of the wave energy penetration to cater to clean global energy demand. An ocean wave is a remarkable energy resource, but it presents a very small share in the global energy mix because of various challenges and limitations encountered to unleash its potential. This study evaluates intensively the complex barriers to the ocean energy technology deployment. The existing and prospective major wave energy projects are extensively examined to identify the learned lessons and optimise possible technological solutions to close the gap in the energy market. Furthermore, limiting and motivating factors to foster the global wave energy potential growth are deeply discussed to ignite new research directions and promising solutions. In particular, the wave energy converters as the underpinning enabling technology are fully investigated regarding their technical readiness, reliability, competitiveness and critical challenges. To complete the power equation, possible energy conversion stages, grid connection and integration issues are dealt with in a broad view of the wave energy power system. Eventually, this study aims at providing an updated ocean wave technology review and progress while introducing new research gap to fast-track contributions in the global energy mix.

Solar power being stochastic and asynchronous in nature, its integration with conventional power generation has so many challenges in damping of low-frequency oscillations. This study presents an investigation of low-frequency oscillation and damping of stochastic solar power integrated power system by a unified power flow controller (UPFC)-based dual optimal controller, which gains are optimised by a novel hybrid particle swarm optimisation and improved grey wolf optimiser. The dual controller simultaneously controls the modulation index of series and phase angle of shunt converters of UPFC, which co-operate with each other, optimising its efficacy and thereby implementing the advantages of both static synchronous series compensator and static synchronous compensator. A detailed Eigen value analysis has been performed with time domain simulations to study the damped oscillatory response of variable and random solar penetration with a power system along with the interaction of solar power with variable synchronous power generations. For a multi-machine system, a multi-input single output dual controller is proposed. A maximum sensor and time delay have been considered to design the controller providing a realistic approach. It is observed that random and heavy solar penetration has a more detrimental effect on system oscillations, which can be damped heavily with the proposed controller, in contrast to particle swarm optimisation, differential evolution, grey wolf optimiser, differential evolution particle swarm optimisation optimised lead-lag and dual controllers.

This study deals with a position sensorless brushless DC (BLDC) motor-driven solar photovoltaic (PV) fed water pump. A technique based on the back electromotive force (back-EMF) zero crossing is proposed for sensorless operation of the BLDC motor. The back-EMF is derived from the difference of line voltages. Thus, a requirement of neutral potential is eliminated. In addition, the proposed drive avoids the use of phase current sensors. The speed is automatically adjusted according to the available peak power from the PV array. The devices of voltage source inverter, used to feed the BLDC motor pump, are switched at fundamental frequency. This leads to minimised switching losses. The responses of PV fed pumping system with the proposed drive are observed under various operating conditions. The suitability of the proposed topology is demonstrated through the hardware implementation.

The optimum tilt and azimuth angle for PV installations in 26 different locations within the county of Yorkshire, UK have been evaluated. In order to examine the performance of the PV systems, a selection of criteria has been identified as follows: (i) the maximum difference in the age of the PV installations is no older than two years, (ii) PV modules technology is crystalline-Silicon (c-Si), (iii) maximum area of study in each location is 20 km², and (iv) PV systems have either the same tilt or azimuth angle within ±2°. The Huddersfield area was used as the primary example to evaluate the proposed methodology. The optimum tilt and azimuth angle for PV installations in the area is 39° and −1° respectively. Moreover, based on 4 kWp PV installations observed in all studied locations, a geographical map representing the annual energy production in the 26 locations has been drawn. The maximum annual energy production is observed for the city of Hull, whereas the minimum observed for the town of Keighley. Finally, the evaluation of the overall annual energy production is discussed using the analysis of the direct normal irradiance (DNI), ambient temperature, air frost, and the cloudiness.

The grid-connected photovoltaic (PV) power is booming, and large-scale PV power is mostly integrated to grid through long transmission lines; however, PV systems may face the threat of subsynchronous oscillation (SSO) when AC system strength is weak. This study establishes the sequence impedance model of grid-connected PV system; mechanism and characteristic of SSO in PV plants integrated to weak AC networks are delved into through impedance-based analysis method. The results show that, under certain conditions, the impedance of PV system is capacitive in the subsynchronous frequency domain, when the networks are weak and the PV capacity is high, the resonance may occur between the capacitive PV system and inductive AC grid. In addition, a smaller proportional gain of current loop may increase the risk of SSO; however, a larger proportional gain and integral gain of phase-locked loop can ease the SSO. Finally, time domain simulation based on PSCAD/EMTDC is conducted to validate the results of the impedance-based analysis. The research here can provide guidance to the project of scaled PV plants integrated to weak AC networks in some sense.

This study presents an optimal control operation of a photovoltaic-battery based standalone microgrid, feeding non-linear loads. To ensure continuous power supply to the critical loads during low insolation or low battery state of charge, a diesel generator (DG) is used as an auxiliary generator. This cost effective hybrid system with maximum utilisation of the renewable as well as fossil fuel based generators can be employed in hospitals, telecom stations in remote areas. In order to nullify the effect of non-linear loads on the DG, modified enhanced phase-locked loop (EPLL) based power quality conditioner is used. The characteristic equation of conventional EPLL is amplitude dependent, thus, the controller tuning parameters need to be modified if the input signal varies over a large range. The presented controller overcomes this problem making the system more robust in eliminating noise and harmonics and extracting fundamental component of a given signal. This component is drawn from the DG with the help of a voltage source converter, thus, making its current always distortion free. The proposed control scheme is simulated in MATLAB. Furthermore, experimental verification is done on a laboratory prototype of the same. The steady state and dynamic responses of the system validate its satisfactory performance.

Four cascaded quasi-impedance source inverter (qZSI) modules are required for achieving nine-level output voltage waveform. In case of one module failure, number of levels in output voltage are reduced to seven. This leads to decrease in the output voltage magnitude and increased THD (higher than conventional seven-level qZSI). This is due to the dominance of unwanted harmonic component introduced in the harmonic spectrum. To restore voltage magnitude and optimize THD performance, novel voltage balancing algorithm is proposed. To validate the control algorithm for off-grid and grid connected system, simulation results of the multilevel qZSI are discussed in two categories: (i) DC voltage source powered multilevel qZSI for RL load subjected to module failure and (ii) solar powered multilevel qZSI connected to utility grid subjected to module failure and variable solar irradiation. Pre-fault and post-fault performance of the system with the proposed control algorithm is discussed for both categories, which validates the effectiveness of the algorithm. Hardware results for proof-of-concept are discussed for DC voltage source fed cascaded qZSI connected to RL load during pre-fault and post-fault conditions. FPGA Virtex-5 is used for hardware implementation of the control algorithm. The results validate the improvement in output voltage both quantitatively and qualitatively.

Multi-level voltage source inverter (VSI) fed doubly fed induction machine (DFIM) has gained prominence in large rated hydro-generating unit (HU) since it provides part load operation with reduced power converter rating and high dynamic stability. Power converters connected in rotor side control real and reactive power of the unit. This study discusses the condenser operation of variable speed HU (250 MW), to be commissioned in Tehri plant (India), with the power flow diagram. Further, it provides dynamic behaviour and survivability status of the DFIM unit during power converter and control circuit faults where power converter redundancy is not available in large rated DFIM unit. Economic analysis of 250 MW HU under power converter and control circuit failures are also investigated. The present work also explores fault tolerant operation of a 250 MW DFIM unit at open switch fault in converters to increase the continuity of the unit operation which provides additional 2% of reactive power support to the grid compared to the DFIM without power converter redundancy operation. Open switch fault is detected through Park's vector phase currents technique and variation in DC link voltage. The computer simulation results are validated in an experiment carried on 2.2 kW DFIM in the laboratory.

Focusing on the electricity and thermal energy requirement of contemporary buildings, a joint operation of photovoltaic thermal (PV/T)-based prosumers and a microturbine-based combined heat and power system has been presented to analyse the economics of a grid-connected microgrid (MG) system. The bidirectional flow of the electricity and heat model is considered and is optimally managed using a price-based demand response (DR) scheme. Thermal storage is exploited to ward off the substantial amount of heat wastages that enhance the system's reliability during any disruption of microturbine. The objective functions of both the prosumer and MG operator (MGO) are formulated as a profit maximisation problem where they interact with each other on the basis of DR activity. To establish this strategic decision-making process, the system is modelled as a Stackelberg equilibrium game, where MGO acts as a leader while PV/T prosumers act as a follower. The interaction or contribution of two players in a game is a problem of non-linear optimisation, which is solved by the differential evolution algorithm. In the end, in a case study, it has been proved that the results are quite lucrative for the proposed model.

With rapid growth of renewable energy sources (RESs) in modern power systems, the microgrids (µGs) have become more susceptible to the disturbances (e.g. large frequency/voltage fluctuations) than the conventional power systems due to decreasing their inertia constant. This low system inertia issue could affect the µGs stability and resiliency in the situation of uncertainties, thus threaten their dynamic security. Hence, preserving µG dynamic security is one of the important challenges, which is addressed in this study. Therefore, this study proposes a novel concept of frequency control incorporating a virtual inertia control-based optimal proportional–integral controller to emulate virtual inertia into the µG control loop, thus stabilising µG frequency during high penetration of RESs. Moreover, the proposed virtual inertia control system is coordinated with digital over/under frequency protection for enhancement of the frequency stability and preservation of the µG dynamic security because of the high integration level of the RESs. The simulation results of the studied µG are carried out using MATLAB/Simulink^® software to validate the effectiveness of the proposed coordination scheme. Results approved that the proposed coordination scheme can effectively regulate the µG frequency and guarantee robust performance to preserve the dynamic security of µG with high penetration of RESs for different contingencies.

Large-scale wind farms connected to the power grid have brought great challenges to power-system dispatch. In this study, an improved two-stage compensation stochastic optimisation algorithm based on recursive dynamic regression is proposed to solve the day-ahead dynamic economic-dispatching problem considering the high-dimensional correlation of multiple wind farms. First, a copula function is used to describe the correlation of high-dimensional wind farms. Second, a two-stage compensation stochastic-optimisation algorithm is proposed to convert the dynamic economic-dispatching model to a two-stage model with mutual iteration by decoupling the conventional and stochastic variables. In this decoupled model, the calculation of the expected compensation cost is critical and usually limited by the dimension of the correlated wind farms, which leads to inefficient convergence and long computation times. To solve those problems, a recursive dynamic multivariable linear regression method based on global least squares is proposed to improve the two-stage stochastic optimisation algorithm. This improved two-stage compensation algorithm overcomes the dimensional disaster of traditional stochastic optimisation methods and can solve the dynamic economic dispatching problem considering the high-dimensional correlation of multiple wind farms. Finally, the practicability and efficiency of the proposed algorithm are verified by the examples of an IEEE118 system and an actual provincial system.

In recent times, the energy consumed by buildings facilities became considerable. Efficient local energy management is vital to deal with building power demand penalties. This operation becomes complex when a hybrid energy system is included in the power system. This study proposes new energy management between photovoltaic (PV) system, Battery Energy Storage System (BESS) and the power network in a building by controlling the PV/BESS inverter. The strategy is based on explicit model predictive control (MPC) to find an optimal power flow in the building for one-day ahead. The control algorithm is based on a simple power flow equation and weather forecast. Then, a cost function is formulated and optimised using genetic algorithms-based solver. The objective is reducing the imported energy from the grid preventing the saturation and emptiness of BESS. Including other targets to the control policy as energy price dynamic and BESS degradation, MPC can optimise dramatically the efficacy of the global building power system. The strategy is implemented and tested successfully using MATLAB/SimPowerSystems software, compared to classical hysteresis management, MPC has given 10% in energy cost economy and 25% improvement in BESS lifetime.

Primary frequency regulation capability of the wind turbine generators is an appealing topic in order to consider safe increasing of the wind power integration into power grids. This study introduces improvements in the primary frequency contribution of the grid-connected variable speed wind turbine generators, which operate under de-loaded conditions. A new dynamic droop control approach based on the fuzzy logic system is proposed. In this control approach, the droop setting is continuously adjusted in response to the de-loaded rotor speed, the frequency deviation, and the rate of change of frequency. In addition, a new dynamic de-loading technique based on the Sugeno–Fuzzy inference system is proposed where the de-loading percentage of the wind turbine generator is decided continuously according to the frequency deviation. The effectiveness of the proposed dynamic de-loading and dynamic droop control approaches is verified through extensive comparative studies. The simulation results confirmed that the proposed control approaches have the ability to provide transient and steady-state power-sharing and improve effectively the frequency stabilisation of the power system within the stable and secure limits of the wind turbine.

Here, the authors bring attention to the stability of the hydro-turbine generator unit (HTGU) with stochastic disturbance during the grid-connection process. First, the stochastic factor of the water head is innovatively introduced to the hydro-turbine governing system (HTGS) during the start-up process of the HTGU. Then, the dynamic characteristics of the start-up and grid-connection process are studied under different stochastic intensities and different values of three system parameters by two different methods, in detail. The results show that the stability of grid-connection is affected obviously by the various intensities of stochastic water head, and there are some interesting phenomena and significant laws. Meanwhile, the values of the HTGS parameters show certain effect on the resistance of HTGS to the stochastic disturbance. Finally, this study can provide a theoretical basis for improving the probability of success in combining the HTGU to the grid in practical process.

The work presented in this study aims to develop an intelligent algorithm, based on fuzzy logic, to track the maximum power point (MPP) of a photovoltaic (PV) panel. Modelling and simulation steps of the PV panel are made by using the MATLAB/Simulink environment, before passing to the description of fuzzy logic MPP tracking (MPPT) algorithm. On an Arduino Mega 2560 controller board, a real-time implementation of the MPPT algorithm by using Simulink Support Package for Arduino Hardware in MATLAB/Simulink was conducted to experimentally validate the preliminary results of simulations. The proposed work outlines also the solution to modify pulse-width modulation frequency of Arduino when it is used with Simulink.