Search

The utility scale of non-conventional generators (NCGs), such as wind and photovoltaic (PV) plants, are competitive alternatives to synchronous machines (SMs) for power generation. Higher penetration of NCGs has been respondent of causing several recent incidents leading up to voltage collapse in power systems due to the distinct characteristics of NCGs under different operating conditions. Consequently, the so-called system strength has been reduced with higher NCGs penetration. A number of indices have been developed to quantify system strength from the short-term voltage stability (STVS) perspective. None of the indices capture the overall performances of power systems on dynamic voltage recovery. In this paper, an improvement in one of the STVS indices namely, the Voltage Recovery Index (VRI), is proposed to overcome shortcomings in the original index. Moreover, the improved index is globalized to establish a new index defined as system voltage recovery index (VRIsys) to quantify STVS at the system level. The amended VRI and developed VRIsys are used in systematic simulations to quantify the impact and interaction of various factors that could affect system strength. The assessment was conducted using time-domain simulation with direct connected induction motors (DCIMs) and a proliferation of converter-based technologies on both the generation and load sides, namely, NCGs and Variable Speed Drives (VSDs), respectively.

A planning framework and operation strategy for energy storage are developed to limit the rate of change of frequency (RoCoF) within the industry requirements in power systems with high renewable energy penetration. The planning framework utilizes a two-step algorithm for the capacity estimation of energy storage. In the first step, the size is calculated analytically based on the frequency dynamics. While in the second step, the estimated size is used as an initial guess in the region reduction iterative algorithm (RRIA) to calculate the accurate required capacity. Furthermore, an economical comparison is carried out among the available rapid responsive storage technologies to find out the most suitable technology for virtual inertia support (VIS). Next, a wind speed forecast informed coordinated control strategy is developed for the storage and wind turbine to provide VIS. An ensemble neural network technique is used for the wind speed forecasting. The coordinated control strategy utilizes the information of forecasted wind speed and the state of energy storage to improve the utilization of storage while limiting the RoCoF within desired window. Simulation results depict the accuracy of the estimated capacity and the effectiveness of the coordinated control strategy.

High penetrations of inverter-based renewable resources (IBRs) diminish the resilience that traditional power systems had due to constant research and developments for many years. In particular, dynamic voltage stability becomes one of the major concerns for transmission system operators due to the limited capabilities of IBRs (i.e., voltage and frequency regulation). A heavily loaded renewable-rich network is susceptible to fault-induced delayed voltage recovery (FIDVR) due to insufficient effective reactive power (E-VAr) in power grids. Hence, it is crucial to thoroughly scrutinize each VAr resources’ participation in E-VAr under various operating conditions. Moreover, it is essential to investigate the influence of E-VAr on system post-fault performance. The E-VAr investigation would help in determining the optimal location and sizing of grid-connected IBRs and allow more renewable energy integration. Furthermore, it would enrich decision-making about adopting additional grid support devices. In this paper, a comprehensive assessment framework is utilized to assess the E-VAr of a power system with a large-scale photovoltaic power. Plant under different realistic operating conditions. Several indices quantifying the contribution of VAr resources and load bus voltage recovery assists to explore the transient response and voltage trajectories. The recovery indices help have a better understanding of the factors affecting E-VAr. The proposed framework has been tested in the New England (IEEE 39 bus system) through simulation by DIgSILENT Power Factory.

Forced oscillation (FO) has recently been detected in power grids, e.g., Nordic and Western American power systems. It has been reported that the FO is excited by forced disturbances, which consist of the frequencies nearly equal to inter-area oscillation frequencies. The FO can lead to severe resonance even for the system with an inter-area damping margin higher than the industry standards. These major events and concerns lead to intensive research of the FO. Though numerous techniques have successfully been applied for FO detection, only a small number of research works have focused on the damping of the FO. Lack of proper control for the FO may lead to instability. Hence, in this paper, a power oscillation damper (POD) is proposed to damp both the FO and inter-area modes simultaneously. The adaptive control technique is applied to enhance the FO mode along with a moving window time, which also avoids the new installation of PODs. Besides, the event-triggered control strategy is used to activate the functions of the new adaptive POD appropriately. The controller's performance and robustness are verified in the modified 14-machine Southeast Australian (SE-A) power system under various uncertainties and disturbances.

Short-term frequency instability is one of the major challenges that arise due to large-scale penetration of converter interfaced renewable energy sources (RESs) in isolated power systems. The short-term frequency instability is associated with high values of rate of change of frequency (RoCoF) and larger frequency excursions. In this paper, a frequency constrained energy management algorithm is proposed. The proposed algorithm manages the power output of RESs, energy storage system, and electric vehicles (EVs) in such a way that the system keeps nonsynchronous power reserve for providing virtual inertia support to avoid high values of RoCoF and frequency excursions. The non-synchronous power reserve is readily available and when deployed can limit the RoCoF as per the required standard. The proposed management algorithm selects the non-synchronous power reserve from different resources, i.e., RES (solar PV, wind turbine), energy storage, and EV, depending on the availability and system loading conditions. Simulation results show the effectiveness of the proposed algorithm.

Frequency stability control in multiple asynchronous grids is a challenging and complex issue. An adaptive droop control strategy to improve the frequency regulation of asynchronous AC areas connected by a multi-terminal DC grid is proposed here. The droop coefficients are adjusted to share the active power adaptively among multiple asynchronous AC grids based on the characteristics of frequency deviation and rate of change of frequency. This results in a cogent allocation of imbalance power in multiple asynchronous grids from the frequency variation perspective. The performance of the proposed scheme is evaluated in a modified multi-machine power system using DIgSILENT Power Factory. Simulation results under significant frequency disturbances caused by credible contingencies are presented to demonstrate the effectiveness of the proposed approach. It is found that the proposed adaptive control ensures an excellent and robust frequency response under different operative conditions.

Large-scale renewable energy-based power plants are becoming attractive technically and economically for generation mix around the world. Nevertheless, network operation has significantly changed due to the rapid integration of renewable energy in supply side. The integration of more renewable resources, especially inverter-based generation, deteriorates power system resilience to disturbances and substantially affects stable operations. The dynamic voltage stability becomes one of the major concerns for the transmission system operators (TSOs) due to the limited capabilities of inverter-based resources (IBRs). A heavily loaded and stressed renewable rich grid is susceptible to fault-induced delayed voltage recovery. Hence, it is crucial to examine the system response upon disturbances, to understand the voltage signature, to determine the optimal location and sizing of grid-connected IBRs. Moreover, the IBRs fault contribution mechanism investigation is essential in adopting additional grid support devices, control coordination, and the selection of appropriate corrective control schemes. This article utilizes a comprehensive assessment framework to assess power systems’ dynamic voltage signature with large-scale PV under different realistic operating conditions. Several indices quantifying load bus voltage recovery have been used to explore the system’ s steady-state, transient response, and voltage trajectories. The recovery indices help extricate the signature and influence of IBRs. The proposed framework’s applicability is carried out on the New England IEEE - 39 bus test system using the DIgSILENT platform.

Forced oscillation (FO) is a challenging problem as it could initiate power system instability due to resonance, especially when the frequency of FO and inherent electromechanical (EM) modes of power system coincide. Twin oscillation components (i.e. inter-area oscillation and FO in the range of 0.1-Hz to 0.8-Hz) are created due to uncertain and uncaptured oscillatory inputs in power systems. The FO may lead to power system instability even with very well-damped EM modes. Therefore, effective countermeasure, i.e., a FO damping method should be incorporated to suppress the FO. This paper presents the systematic design and development of a controller termed as a Force Oscillation Damping Controller (FODC) for damping FO considering uncertainties and disturbances. The FODC and conventional inter-area damping controller are activated at different stages to make sure both controllers operate effectively. An adaptive algorithm is applied to make sure that the FODC can keep the FO mode in stable region at all operating conditions. The FO detection using an event-triggered control is applied to start the operation of FODC during the forced disturbance. Study results in IEEE 14-machine South East Australian (SE-A) interconnected power system demonstrate the efficacy of the proposed FODC in damping major FOs.

The electrical energy required by the remote communities can be supplied efficiently and effectively using a decentralised renewable energy source (RES). However, the stochastic variations in power output of RESs, i.e. solar photovoltaic and wind turbine, and deviations in demand make it difficult to preserve the balance between generation and demand which may jeopardise the stable operation of the system. Moreover, in the islanded systems the lack of inertia due to the replacement of conventional power plants with inverter-based sources cause undesirable influence on the frequency of the supply. Generally, various energy storage systems (ESSs) are proposed in such a grid to overcome this problem. This study investigates the implications of the hybrid ESS (HESS) on the frequency regulation (FR) of an islanded system. Battery ESS and a supercapacitor has been used to form a HESS for the islanded power system. Analysis has been conducted in MATLAB/Simulink simulation platform. Simulation results demonstrate the efficacy of the proposed HESS in FR of the islanded system.

The future Indonesian power grid will have significant REGs, especially in Java Island. Wind and solar photovoltaic (PV) will be the dominating technologies in future Indonesian grid. Although REG can provide clean and sustainable energy, they also cause undesirable effects on system stability due to the uncertainty in their output and different dynamic characteristics. Battery energy storage system (BESS) has been considered as the promising candidate to manage the intermittency and low inertia associated with wind and PV in many future power systems. In addition to the normal functionality, the resilient wide-area power oscillation damping (POD) can be implemented in the BESS to damp the low-frequency oscillation in the system. This research proposes a method to design a resilient wide-area POD in BESS. A grey wolf optimiser (GWO) has been used to synthesise the resilient wide-area POD. The representative dynamic model of Java-Indonesian power system is used to evaluate the performance of the GWO-based resilient wide area POD. From the results, it is evident that the implementation of the proposed controller at BESS successfully damped the critical mode of the system. It is also observed that the proposed controller is robust against the failure of the input signal.

Modern power systems consist of power electronics devices, which are used in renewable energy (RE) conversion. However, these devices, associated controllers, and uncertainty in RE output could bring new challenges to power system stability, especially oscillatory stability. Hence, the integration of battery energy storage systems (BESSs) is being developed to minimise the uncertainty and variability in renewables. Furthermore, to tackle the complex dynamics and inertia-less characteristics of wind and PV plants additional controllers such as power oscillation damping (POD) control and virtual inertia scheme are sought. However, the primary challenges associated with the wide-area oscillation damping controller are signal transmission delay, loss of communication signal, data drops, and others. This paper proposes a bat algorithm (BA) based resilient wide-area multi-mode controller (MMC) for enhancing oscillatory stability margin with high penetration of renewable power generations (RPGs) and BESSs. The Java 500 kV Indonesian grid is used to evaluate the performance of the resilient wide-area MMC. From the results, it is found that the proposed controller effectively damp the critical mode of oscillation in the system even under communication failure as well as certain damping controller failures.

High penetration of voltage source converter (VSC) based system is anticipated in future power systems. This study discusses the interaction of modular multilevel converter (MMC) based high voltage dc (HVDC) system with the dynamic of the host ac network in the electromechanical time frame. The respective controls for MMC-HVDC system suitable for the stability studies in the electromechanical time-frame are considered. This paper gives insight into the effects of several important sensitivities such as (i) MMC control implementation, (ii) non linearity associated with the fault ride through implementation, and (iii) phase locked loop parameters on ac system dynamics. The comprehensive analysis has been performed using an equivalent model of Great British transmission system.

In the current energy perspective, home energy management (HEM) is an essential requirement for residential consumers due to excessive energy utilization by the household appliances. This paper proposes an improved energy and cost minimization scheme for residential consumers to shape peak load and utility tariffs. An efficient power management algorithm (PMA) has been developed with renewable energy sources (RESs) and energy storage systems (ESS). The PMA is executed using C++ software. The benefits of the RESs and ESS with the proposed PMA techniques are analyzed using three different scenarios. Extensive case studies are carried out to validate the effectiveness of the proposed energy and cost minimization scheme. It is demonstrated that the proposed method may save energy and costs up to 34% and 45% compared to the existing methods.

Energy storage is recognized as a potential solution to alleviate the impacts of inertia reduction and intermittency due to the integration of inverter based renewable energy sources (RES) in power systems. Out of various rapid responsive energy storage technologies, supercapacitor energy storage (SCES) is the most promising technology for synthetic inertia support. Because the SCES has high power density, very small response time, and large cycle life. In this paper, a dynamic derivative-droop control strategy is developed for SCES to provide the synthetic inertia in low inertia power system. The proposed strategy overcomes the limitations of separately applied derivative and droop controls. In addition, the use of time varying gains (referred as dynamic) instead of fixed gains improves the performance compared to derivative-droop coordinated control. Different types of events are created at different penetration levels of RES to test the robustness of the proposed control. A comparison, based on RoCoF and frequency nadir, between the derivative, droop, derivative-droop coordinated and the proposed controls is presented to show the effectiveness of the proposed control approach.

Several efforts have been taken to promote clean energy towards a sustainable and green economy. Existing sources of electricity present some complications concerning consumers, utility owners, and the environment. Utility operators encourage household applicants to employ residential energy management (REM) systems. Renewable energy sources (RESs), energy storage systems (ESS), and optimal energy allocation strategies are used to resolve these difficulties. In this paper, the development of a cluster-based energy management scheme for residential consumers of a smart grid community is proposed to reduce energy use and monetary cost. Normally, residential consumers deal with household appliances with various operating time slots depending on consumer preferences. A simulator is designed and developed using C++ software to resolve the residential consumer&rsquo, s REM problem. The benefits of the RESs, ESS, and optimal energy allocation techniques are analyzed by taking in account three different scenarios. Extensive case studies are carried out to validate the effectiveness of the proposed cluster-based energy management scheme. It is demonstrated that the proposed method can save energy and costs up to 45% and 56% compared to the existing methods.

Due to the anticipated proliferation of HVDC links up to and beyond 2020 into transmission systems, it is expected that in some locations, two or more HVDC links will be installed with a short electrical distance between them and will form a multiinfeed (MI)-HVDC scenario for the system. The control and operation of MI-HVDC systems are of particular concern for weak grids such as that likely to be found in the North of Scotland network. It is shown that the ac voltage regulation in the VSC-HVDC link may adversely affect the dynamic performance of the host weak ac system under the MI-HVDC scenario. To overcome this identified limitation associated with the ac voltage controller in the VSC-HVDC link, a new controller modification conforming to the grid code is proposed in this paper. Furthermore, this paper presents a robust control design method for ac voltage control using the fractional order (FO) control design theory. The influences of the proposed FO-based ac voltage controller are assessed alongside various voltage controllers for the representative North Scotland system. It is shown that the FO-based ac voltage controller has favorable effects on the dynamic behavior of weak ac systems with MI-HVDC.

Recently, the electromechanical oscillations are becoming the primary concerns in power grids due to the integration of renewable energy generations (REGs). The inherent characteristics of REGs, e.g. low or no inertia, stochastic generation, could lead to the lower damping margin in power systems. A supplemental control such as power system stabiliser or power oscillation damping (POD) controller is widely applied to augment the damping margin in power systems. However, the PSS or POD using local signal is not adequate to damp the oscillation contributed from different sources. Hence, a wide-area damping controller can be employed in this context. Nonetheless, the wide-area controller suffers from communication failure. Therefore, the wide-area controller with resilient to communication failures is inevitable. This study proposed a wide-area POD design method considering resiliency. A modified differential evolution algorithm is employed to synthesise the wide-area damping control. The two-area and Java-Indonesian (three-area) power systems are used to evaluate the performance of the proposed controller for oscillation damping. From the results, it is evident that the critical mode(s) of the system successfully damped by employing the proposed controller. It is also found that the proposed controller is robust against communication failures.

Voltage-source converter-high-voltage direct current (VSC-HVDC) systems have become an attractive option for integrating remote and far-from-shore renewable energy resources to main AC grids. The desire for greater power transfer capability and the difficulty in securing right-of-way for new AC lines in many countries is also resulting in the increased use of embedded VSC-HVDC systems operating in parallel with existing AC lines. It has been stated that the control and operation of VSC-HVDC systems are of particular concern for weak grids with fewer large synchronous generation units (a highly probable case for many grids in future). If the anticipated proliferation of VSC-HVDC links continues, several aspects of system stability will be significantly impacted. This study presents an overview of the effects of VSC-HVDC control and operation on power system stability. The structure, control, control tuning, and modelling of VSC-HVDC is briefly summarised to provide context for subsequent discussion of the system dynamics. An extensive critical review of the previous research into mixed AC-DC systems incorporating VSC-HVDC is then provided including voltage stability, small and large-disturbance angle stability, high-frequency interaction, and frequency stability. Finally, recommendations are presented to guide critical future research.

The efficient utilization of clean energy resources to meet increasing electricity demand is imposing the integration of the electricity market and the construction of secure transmission mechanisms around the globe. Accordingly, the Association of Southeast Asian Nations (ASEAN) is integrating its large geographical power transmission infrastructure via the ASEAN power grid (APG). This study extensively reviews the energy resources (i.e., fossil fuels and renewables), the current utilization, and the future projection for ASEAN. Electricity export-import scenarios and renewable generation based transmission expansion planning practices in ASEAN will also be critically reviewed in this work. Additionally, the major barriers and technical challenges for establishing an ASEAN grid will be briefly analyzed. Finally, this work suggests possible techniques that help expedite the renewable power generations to overcome the limitations associated with the establishment of the APG, as well as future research direction in enhancing the utilization of APG for ASEAN.

This paper reports on a case study of the community group Zero Emissions Noosa, whose goal is for 100% renewable electricity in the Noosa Shire (Queensland, Australia) by 2026. Described within this paper are the processes used by Zero Emissions Noosa to set up their zero emissions plan, involving community engagement and the use of an external consultant. The external consultant was employed to produce a detailed report outlining how to successfully achieve zero emissions from electricity in the Noosa Shire by 2026. This paper explains how and why the community engagement process used to produce the report was just as important as the outcomes of the report itself. Modeling was undertaken, and both detailed and contextual information was provided. Inclusion of the community in developing the scenario parameters for the modeling had a number of benefits including establishing the context within which their actions would occur and focusing their efforts on options that were technically feasible, financially viable and within their capabilities to implement. This provided a focal point for the community in calling meetings and contacting stakeholders. Rather than prescribing a particular course of action, it also resulted in a toolbox of options, a range of possible solutions that is flexible enough to fit into whatever actions are preferred by the community. The approach and outcomes discussed in this paper should, therefore, be useful to other communities with similar carbon emission reduction goals.

Dynamic voltage instability (DVI) issues are the primary concern in low-voltage distribution network (DN) due to growing integration of low-inertia compressor motor loads such as air-conditioner and refrigerator. The concern of DVI is likely to increase owing to high penetration of rooftop type single-phase photovoltaic (PV) units in DN. On the other hand, DNs are inherently unbalanced as a result of load and line characteristics along with unbalanced PV penetration. This paper examines the impact of imbalance on the dynamic voltage stability (DVS) in DN and provides solutions to mitigate any adverse effects. Dynamic models of the single-phase PV units are developed and utilised in the paper. The degree of unbalanced is defined first, and then its impact on the DVS is investigated. From the investigation, it is observed that degree of instability is increased with the increment of imbalance. The paper has also proposed a mitigation strategy i.e. reactive power injection by PV inverter. Case studies are conducted on modified IEEE 4 bus system which represents a low-voltage DN. Results reveal that reactive power injection by PV inverter can improve the DVS by mitigating the impact of unbalance.

A paradigm shift in power generation technologies is happening all over the world. This results in replacement of conventional synchronous machines with inertia less power electronic interfaced renewable energy sources (RES). The replacement by intermittent RES, i.e., solar PV and wind turbines, has two-fold effect on power systems: (i) reduction in inertia and (ii) intermittent generation, lead to the degradation of the frequency stability. In modern power system, the frequency regulation (FR) has become one of the most crucial challenges compared to conventional system because the inertia is reduced and both generation and demand are stochastic. The fast responsive energy storage technologies, i.e., battery energy storage, supercapacitor storage technology, flywheel energy storage, and superconducting magnetic energy storage are recognized as viable sources to provide FR in power system with high penetration of RES. The important aspects that are required to understand the applications of rapid responsive energy storage technologies for FR are modeling, planning (sizing and location of storage), and operation (control of storage). This paper comprehensively reviews these important aspects to understand the applications of fast responsive storage technologies more effectively for FR services. In addition, based on the real world experiences this paper highlights the gaps and limitations in the state-of-the-art practices. Moreover, this study also provides recommendations and future directions for researchers working on the applications of storage technologies providing FR services.

Power industries around the world are becoming liberalized to meet the increasing electricity demand efficiently and sustainably. Advanced and robust system planning are required to interconnect the power system over the large geographical area. The accurate model of power system covering the large geographical area like ASEAN Power grid (APG) is not available in the public domain. This paper presents a methodology for developing a test system model for ASEAN power grid using publicly available data. The modelling approaches are explained, and information sources are given here. The resulting APG model is simulated in MATLAB/MATPOWER simulation environment, and results are validated against the published generation and demand profiles. From the validation results, it is found that the developed model closely resembles the ASEAN power grid. The model developed here will help different stakeholders to analyze the future development scenarios of the ASEAN network.

This paper proposed a method for simultaneous parameter optimization for coordinated control of battery energy storage (BESS) and dual input power system stabilizer (DIPSS). An artificial immune system (AIS) clonal selection algorithm has been employed for parameter optimization. The two-area power system is used as a test system to assess the coordinated control along with the optimized parameters. Eigenvalue analysis and time domain simulations are used to investigate the dynamic performance of the system with proposed coordinated control algorithm. From the simulation results, it is found that by designing BESS and DIPSS parameter coordinately using AIS clonal selection algorithm the oscillatory stability performance of the power system can be enhanced with high penetration of REG.

The Java-Indonesia 500 kV network is the biggest interconnected system in Indonesia. This system extends from the western part of Java Island to eastern part with a distance of approximately 1000 km. This long tie-line may contribute to the instability of power system, in particular, low-frequency oscillation stability of the system at weak grid condition. However, small attention has been paid so far to investigate the low-frequency oscillation stability performance on Java 500 kV system. Hence, this paper investigates the low-frequency oscillation stability performance of Java 500 kV network. Eigenvalue analysis and damping ratio analyses are employed to examine the dynamic behavior of this system. Time domain simulation has been applied to verify the modal analysis of Java system. Furthermore, dual input power system stabilizer (DIPSS) has been applied in this paper to enhance the low-frequency oscillation stability margin of the system. The DIPSS parameters are tuned using Craziness particle swarm optimization (Craziness PSO). From the simulation results, it is found that there is a weak mode in the Java 500 kV system. The installation of DIPSS based on Craziness PSO in the Java 500 system enhanced the low-frequency oscillation stability margin of the system.

In the 21st century, integration of large-scale renewable energy sources (RESs) is increasing significantly. Although RESs provide clean and sustainable energy, they may adversely affect the performance of power system due to their distinct dynamic characteristics and intermittent power output. It is apparent that the integration of battery energy storage system (BESS) in power system is inevitable to accommodate more RESs. BESS could provide additional active and reactive power to the grid to overcome the energy shortfall. It is reported that the dynamics associated with BESS may significantly influence the low-frequency oscillation of the system. Therefore, it is important to analyze the various models of BESS for power system small signal stability studies. This paper investigates various models of BESS and their impacts on low-frequency oscillation for high penetration of RESs. Analysis has been conducted using Two-area power system for which the benchmark results are available for comparison purpose. Both the eigenvalue and time-domain analyses are employed in this paper to assess the impacts of various BESS models on low-frequency oscillation. From the simulation results, it is evident that the detailed model of BESS (i.e. 5th order model) could reflect the complete influence of BESS controller on low-frequency oscillation.

This paper presents the impact of dynamics within the wind farm on low-frequency oscillatory stability of power systems. The aggregated dynamic model of squirrel cage induction generator (SCIG) based wind farm is used in this paper to examine the contribution from wind energy conversion system on low-frequency oscillation. The characteristics of the oscillatory modes are presented using the modal analysis for the given operating condition. Finally, a detailed wind farm model consisting of actual number of wind generators is used in simulation to capture all the possible modes within the wind farm. The analysis conducted in this paper reveals the importance of using detailed wind farm model in low-frequency oscillatory stability studies.

This work is a feasibility study of high voltage AC (HVAC) and high voltage DC (HVDC) transmission option for the Association of Southeast Asian Nations (ASEAN) Power Grid (APG) interconnections. An optimal power flow, a minimum-cost power generation model, is developed in the MATPOWER simulation platform to perform this analysis. Electricity generation and consumption data are taken from the latest power development plans of individual ASEAN countries for the evaluation of optimal cross-border power flow through the interconnections. Results show that APG can enhance power generation from countries with abundant renewable resources to meet the growing demand at load centers in the ASEAN member nations. An annual cost is used as the output matrix for this study. The analysis results reveal that in some interconnections, implementing HVDC link instead of currently planned HVAC could be economically beneficial for the APG. The findings in this paper would serve as valuable references for the APG planners.

This paper presents a frequency control mechanism for an AC system through the active and reactive power loops of a VSC-HVDC system. The proposed scheme makes use of the reactive power loop for inertia support by exploiting the voltage-power sensitivity of loads, and active power droop control has been used to provide governor-like support following the large-disturbance. The performance of the presented controller is evaluated through various simulation case studies in DIgSILENT Power Factory including small-perturbation to demonstrate the effect of the frequency controller in system electromechanical mode damping. From the set of case studies it can be found that the proposed dual-loop control has favorable effects on the frequency behaviour and the inter-area mode damping of the system.

To exploit the full and flexible capability of offshore voltage-sourced converter high-voltage DC (VSC-HVDC) lines, interaction studies in the offshore AC grid are required but are not well understood or reported. This study examines the interaction dynamics of an offshore AC grid for interconnecting large wind power plants (WPPs). The conventional eigenvalue analysis method has limitations which make the interaction analysis of such systems difficult. Hence, in this study, an impedance-based analytical approach is employed to investigate the interaction phenomena. The impedance model of a VSC-HVDC converter for both direct and vector control with outer and droop controls are derived along with the impedance model of the full-converter wind generator. The interaction dynamics of the offshore grid is predicted through the well-established Nyquist criteria and is validated using time-domain simulations. The analysis shows that the system stability is decidedly influenced by the control configurations and tuning of the VSC-HVDC lines.

Point-to-point VSC-HVDC Wind power plant (WPP) links connected offshore by AC cables can be called an AC integrated VSC-HVDC scheme or virtual multi-terminal DC (MTDC) grid. Since, the AC integrated VSC-HVDC scheme forms an offshore AC grid, parallel operation of offshore VSC-HVDC converters is required. This paper compares three offshore converter control topologies: (i) feedforward control of AC voltage and frequency, (ii) feedback control of AC voltage, and (iii) feedback control of AC voltage and frequency with an inner current loop. The performance of power and current based droops has been assessed for the parallel offshore converters. Simulations carried out in DIgSILENT Power Factory are presented to illustrate the effect of these offshore converter control strategies on the dynamics of the AC system following the offshore grid disturbances.

Renewable energy sources, especially wind and solar photovoltaic (PV) are well on the way to dominate power systems as their penetration levels are increasing at a staggering rate in many countries. Consequently, utilities around the world are discussing and conducting feasibility studies of “100 %” renewable energy based power systems. Even though a very high penetration level of renewable energy looks plausible, the technical challenges associated with them could be a hindrance to the seamless integration. This chapter focuses on technical challenges associated with the grid integration of renewable energy and they are classified as challenges in the distribution and transmission systems, respectively. Most of the PV integration is happening in the distribution system while wind integration can also be in the transmission system. This chapter also highlights security concerns and associated risks, which are categorized as technical and non-technical issues. Finally, the chapter summarizes the way forward for the renewable energy integration in power systems.