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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]

In this study, model predictive control (MPC) with constant switching frequency is proposed for four‐leg distribution static compensator (FL‐DSTATCOM) to compensate the current related power quality issues. MPC techniques having many advantages compared to conventional pulse width modulation and hysteresis control techniques. In MPC, the future behaviour of the controlled variable is predicted using the model of the system and a cost function is formed using reference and predicted variable. MPC for DSTATCOM applications consider the difference between the reference and actual DSTATCOM current as a cost function and selects the switching state which minimises the cost function. However, while using MPC, the switches of DSTATCOM operate in variable switching frequency and sometimes the values are also very high. Due to this reason higher switching losses, unequal stress appear across the inverter switches and it also reduces the lifetime of the switch. Therefore, in this study, the concept of three‐dimensional space vector modulation is adopted to achieve a constant and user‐defined switching frequency MPC for FL‐DSTATCOM to conquer the limitations of conventional variable switching frequency MPC. The validation of the proposed work is achieved using simulation and experimental studies. [ABSTRACT FROM AUTHOR]

This paper presents photovoltaic (PV) system control as distributed static compensator (DSTATCOM), termed as PV‐DSTATCOM, operated with active current control (ACC) and feed‐forward control loop (FFCL). Besides active power injection into the utility grid, the proposed PV system autonomously transforms into a DSTATCOM to provide various ancillary services including source current harmonic suppression, load reactive current compensation, zero sequences component mitigation, and power factor correction. Since PV‐DSTATCOM operates with ACC, it precisely extracts the fundamental in‐phase and quadrature components of current. It introduces high‐gain at the third‐order harmonic and thereby alleviates stationary errors in the current control loop of PV inverter. The proposed ACC+FFCL structure is computationally efficient and unconditionally stable. Practically, FFCL addresses the challenges emerged due to nonlinearity introduced by the PV unit and ensure a rapid power balance between the PV unit and electric grid. Further, a simplified perturb and observe based maximum power point tracker has been employed to evacuate the maximum power from the PV array. The proficiency of the developed ACC+FFCL structure is investigated through a comprehensive set of transient studies using MATLAB/Simulink software. Finally, a laboratory setup has been developed using the dSPACE‐1104 platform and experimental results are recorded with detailed comparative evaluation. [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]

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 work, the development of sign regressor least mean mixed norm (SRLMMN) control technique for a distribution static compensator (D‐STATCOM) is presented. This control technique extracts fundamental weight components from the non‐sinusoidal load currents and generates reference grid currents. D‐STATCOM is developed for harmonics eradication, reactive power injection and load balancing and its performance is investigated in several operating modes. The performance of SRLMMN control is compared with recursive least square (RLS) and variable step least mean square (VSLMS) control techniques in terms of convergence, steady‐state error, harmonics elimination, sample time and computation complexity. The major advantages of SRLMMN control technique, are fast convergence, less steady‐state error, low total harmonic distortion (THD) and offers less computation complexity when compared with RLS and VSLMS. A laboratory‐scale prototype of compensator is realised using a voltage source converter with the controller implemented in the dSPACE‐MicroLabBox. Both MATLAB simulation and experimental results are included to demonstrate the performance of shunt compensator under steady‐state and dynamic loadings. The developed SRLMMN control technique mitigates power quality problems and effectively suppresses THD observed in the grid current with reference to IEEE Standard 519–2014. [ABSTRACT FROM AUTHOR]

This study presents the control of distribution static compensator (DSTATCOM) using band‐dependent variable step size (BD‐VSS) individual weighting factor with sign error based adaptive filter for power quality improvement in a weak distribution grid. Here, the proposed algorithm is used for estimation of fundamental active weight components from the distorted load currents in order to generate the reference grid currents to mitigate the grid currents power quality issues. This new control algorithm is proposed for fast and accurate estimation of active weight components with low steady‐state error, without dynamic oscillation at fast convergence speed. Moreover, the frequency locked loop‐double self‐tuning second‐order generalised integrator based voltage filter is used to extract the positive sequence voltages of the distorted grid voltages for estimating the harmonics, and noise‐free voltage unit templates. Therefore, the DSTATCOM with the proposed control algorithm is capable of mitigating the harmonic currents, providing reactive power compensation and operating at unity power factor in a weak distribution grid. Test results demonstrate the viability and robustness of the proposed control algorithm under balanced and unbalanced non‐linear load conditions. [ABSTRACT FROM AUTHOR]

In this study, the design and implementation of a new hybrid soft computing control technique called Levenberg–Marquardt backpropagation (LMBP)‐based icosϕ is proposed. Two different compensation techniques are evaluated for the performance analysis of three‐phase three‐wire (3P3W) voltage source converter (VSC)‐based DSTATCOM. The first one is the conventional icosϕ control technique whereas the other one is called the LMBP‐based icosϕ control technique. The better power quality of the system is obtained using the proposed control algorithm by maintaining a less voltage across the capacitor as compared to the conventional one. So, the reduction in the size of the DSTATCOM is realised by the LMBP‐based control algorithm. Furthermore, the performance parameters such as load balancing, harmonics elimination, power factor improvement, and voltage regulation are evaluated under both balanced and unbalanced loading conditions as per the IEEE guidelines. The effectiveness of the proposed controller is studied in the MATLAB/Simulink environment and also validated with a low power rated prototype experimental results. [ABSTRACT FROM AUTHOR]

A four‐leg distribution static compensator (FL‐DSTATCOM) has been employed for improving the quality of power in electric distribution system using field‐programmable gate array (FPGA). A predictive current control technique without any modulation scheme is utilised to generate switching pulses for FL‐DSTATCOM using a cost function defining the preferred system behaviour. This technique makes the supply current as balanced and sinusoidal by exactly tracking the reference current, compensating the reactive power, maintaining near unity power factor and nullifies the current flow in neutral conductor during steady and dynamic state conditions. Synchronous reference frame theory is effectively implemented for extracting the reactive and harmonic part of load current which are the primary components in the evaluation of reference currents. The predictive current control scheme implemented in FPGA has been deployed to evaluate the behaviour of the FL‐DSTATCOM under multifarious loading conditions. [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]

This paper presents the voltage‐controlled oscillator (VCO) less phase‐locked loop (PLL)‐based control of voltage source converter. It is used in the distributed power generation system for improved power quality. This control extracts the fundamental component from the sensed load current using three phases to alpha–beta transformation without using VCO, unlike synchronous reference frame–PLL, where fundamental component extraction needs two transformations with the use of VCO. Owing to the absence of VCO in the proposed method, the computational burden of trigonometric operations is very less that results in a faster dynamic response under variable conditions. This characteristic makes it suitable for the distributed power generation system, where fast changes occur frequently. In this study, wind‐based distributed generation system has been taken for study, which comprises of self‐excited induction generator feeding non‐linear load with varying electrical conditions. Using the proposed control, the reactive power compensation, harmonics reduction and load balancing are carried out in the system. In addition to it, neutral current compensation is also accomplished with the help of star–delta transformer connected at the load end. The system performances are investigated under steady state as well as in transient state and results are found satisfactory. [ABSTRACT FROM AUTHOR]

In this study, model predictive control (MPC) of the three‐phase split capacitor (TPSC) distribution static compensator (DSTATCOM) using VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) method is proposed. Power quality improvement using MPC involves the selection of switching state which minimises the difference between reference and actual DSTATCOM currents. However, the limitation of MPC is higher switching frequency and limitation of TPSC DSTATCOM is voltage divergence of dc‐link capacitors. To alleviate these problems, one constraint is to suppress the voltage divergence and the other is to reduce the switching frequency is included in the cost function using weighting factors. Optimal selection of switching state for minimisation of a multi‐constraint cost function is depending on the weighting factor; however, its tuning is a challenging task. In this study, the simplification of weighting factor tuning is achieved using the VIKOR method and it further selects the optimal switching state based on a specific measure of closeness to the ideal solution and multi‐criteria ranking index. The advantages of the proposed work are compensation of power quality issues, balance the dc‐link voltages, switching frequency reduction of inverter and simplification of weighting factor tuning. Finally, the proposed work is evaluated using simulation and experimental studies. [ABSTRACT FROM AUTHOR]

This study presents a scheme for improvement of power quality in electrical distribution systems using a static VAr compensator (SVC). The switching of the SVC has been controlled with an objective to improve the overall power quality at the distribution level. The reduction of the degree of unbalance and improvement of power factor along with minimisation of harmonics injected into the system due to the operation of SVC are identified as the objectives of the SVC switching scheme. The proposed scheme can minimise a wider range of harmonics injected into the system without any external filter. The optimised switching angles have been calculated using the particle swarm optimisation technique. An artificial neural network has been designed to predict the optimum triggering angles and the performance of the scheme for fast changing loads has been evaluated in the laboratory using a data acquisition system. Practical evaluation of power quality has been carried out at each stage of simulation and experimentation to highlight the effectiveness of the proposed scheme. The results obtained from the proposed scheme have been compared with other recent works to prove the efficacy of the system. [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]

In recent years, new trends in electrification of the transport sector have been a major concern for distribution grid operators. New types of flexible, uncontrollable loads, such as EV, influence the reliability of distribution networks. This work is related to the distribution system planning framework, with a particular focus on uncoordinated flexible EV loads. The main focus is the enhancement of the hosting capacity of EVs on distribution networks, while maintaining power quality (especially voltage magnitude and voltage unbalance), which is ultimately a pre‐requisite for increasing prosumer engagement. Several EV charging scenarios, in the context of UK/Irish distribution networks with increased penetration of EV prosumers are considered. The results show that reactive power compensation through STATCOM, in the context of EV integration, can provide continuous voltage support and thereby facilitate 90% penetration of network customer EV connections at a normal EV charging rate (3.68 kW). If fast charging (up to 11 kW) is employed, <30% of network EV customers can be accommodated due to bottlenecks presented by the substation transformer loading. [ABSTRACT FROM AUTHOR]

A distribution static compensator (DSTATCOM) is implemented at distribution level for overcoming several power quality problems commonly encountered today. Some of these problems considered here deal with issues of harmonics, unbalancing of loads, meeting reactive power demand of the load for improving power factor to unity and regulating the voltage. A new technique is proposed based on affine projection control algorithm and its design and implementation on a shunt compensator are discussed. The proposed control approach estimates the fundamental weight values of load currents. These weights are utilised to compute the magnitude and phase of reference grid currents and consequently gating pulses for three‐phase voltage source converter (VSC). The control approach is based on the convergence of the weighted values and is independent of the property of the input signal. This control approach has characteristic of updating weights on the basis of multiple, delayed input signal vectors. Fast convergence of active and reactive weighted values is added advantage of the proposed control approach with the above‐mentioned characteristics. A working prototype of the DSTATCOM is implemented using three‐phase VSC and digital signal processor (DSP) (dSPACE 1104). The affine projection control approach is developed in MATLAB/SIMULINK and verified on a prototype using DSP. [ABSTRACT FROM AUTHOR]

Load current may become highly distorted in a weak power system network due to the presence of non‐linear and dynamic loads. Harmonics get penetrated into the supply system too; thereby making it polluted and rich in harmonic content and causing a detrimental effect on the performance of other connected loads. In such cases, the conventional control algorithms fail to work effectively to mitigate power quality (PQ) issues. This study addresses solutions to PQ issues which get aggravated in the presence of distorted supply. This study proposes a multiple complex coefficient filter (MCCF)‐second‐order generalised integrator (SOGI)‐based controller designed to effectively compensate for PQ problems associated with weak grid. A MCCF filter is designed to extract the fundamental components of grid voltage used further for grid synchronisation. The SOGI is designed to extract the fundamental active current magnitude of the load current and reduce PQ issues with the help of Distributed Static Compensator (DSTATCOM). Neutral current compensation is achieved with an appropriately designed zigzag transformer. Extensive simulation and hardware results realising dSPACE 1104 as Digital Signal Processor are considered in this study to show that the performance of the proposed control algorithm under PQ issues with distorted grid. [ABSTRACT FROM AUTHOR]

This paper presents a voltage-controlled distribution static synchronous compensator (DSTATCOM)-based voltage regulator for low-voltage distribution grids. The voltage regulator is designed to temporarily meet the grid code, postponing unplanned investments while a definitive solution could be planned to solve regulation issues. The power stage is composed of a three-phase four-wire voltage-source inverter and a second-order low-pass filter. The control strategy has three output voltage loops with active damping and two dc bus voltage loops. In addition, two loops are included to the proposed control strategy: the concept of minimum power point tracking (mPPT) and the frequency loop. The mPPT allows the voltage regulator to operate at the minimum power point, avoiding the circulation of unnecessary reactive compensation. The frequency loop allows the voltage regulator to be independent of the grid voltage information, especially the grid angle, using only the information available at the point-of-common coupling. Experimental results show the regulation capacity, the features of the mPPT algorithm for linear and nonlinear loads, and the frequency stability. [ABSTRACT FROM PUBLISHER]

In the same feeder, it will decline the power quality of power supply when the quality is poor at load side, which can cause other equipment malfunction and even damage devices. Therefore, a reactive power compensation method is suggested to improve the power quality of the electric arc furnace in a distribution power system. Both the static var compensator (SVC) and an active filter can modify power factor and balance three phase currents simultaneously. The active filter can solve the problem of instantaneous state of an SVC. Then, an SVC can reduce power quantity of the active filter. Finally, field measurement data in a metal factory were analyzed. Simulation results confirmed the feasibility of correcting the power factor and balancing load currents simultaneously using the proposed method. [ABSTRACT FROM AUTHOR]

A distribution static compensator (DSTATCOM) is used for power quality improvement in the distribution system. In the conventional DSTATCOM, the dc voltage is kept constant and it is selected based on rated reactive load. Under light load or reduced load conditions, the compensator works perfectly even though the dc voltage is reduced from its rated value. Maintaining the dc voltage constant under reduced or light load conditions leads to unnecessary voltage stress across the switching devices. Therefore, in this study, a simple dynamic dc voltage regulation is proposed to reduce the voltage stress across switching devices under the reduced load conditions. The proposed algorithm optimises the value of dc voltage based on reactive load without compromising the performance of the DSTATCOM. To validate the proposed method, simulation and experimental studies were carried out on the three‐phase two‐level split‐capacitor DSTATCOM for harmonic mitigation, reactive power compensation and load balancing. [ABSTRACT FROM AUTHOR]

The output active and reactive powers of wind farms are highly time‐varying even in extremely short time periods which cause flicker. In many wind farms static VAr compensators (SVCs) are employed to mitigate this flicker. In this study it is shown that reactive power variations of wind farms are even faster than those which can be fully compensated by SVC. This inability of SVCs comes from the delays in the reactive power measurement and thyristor ignition circuit. To overcome this limitation, the reactive power of a wind farm is predicted for a half cycle (10 ms) ahead. Large numbers of data were recorded from the Manjil wind farm in different weather conditions. Auto regressive moving average (ARMA) models were used for the prediction, and model adequacy checking was employed to determine the best ARMA model order. To evaluate the performance of proposed method, with a novel procedure the wind farm is simulated using the actual recorded data. The instantaneous flicker sensation and short term flicker were calculated and compared for three cases; without SVC, using SVC with the traditional control method, and using SVC with the proposed prediction method. The results confirm the superiority of the proposed technique. [ABSTRACT FROM AUTHOR]

Electric arc furnace (EAF) is one of the largest non‐linear loads in power systems. It is highly time‐varying which leads to low‐frequency voltage fluctuations in the system, called flicker. Static VAr compensator (SVC) is always used in EAF plants to compensate the reactive power and reduce voltage fluctuations. The reactive power calculation unit is one of the most important units in SVC control system. Since SVC can only compensate the fundamental component, the calculated reactive power should not be sensitive to other harmonics. On the other hand, since the reactive power changes every half cycle, its calculation should be fast enough to track the changes. Hence, a calculation method with minimum delay and lowest harmonic sensitivity should be utilised to achieve an effective compensation. Among different already proposed methods for calculation of reactive power, differential method has the lowest delay. However, it is very sensitive to harmonics. In this study, Kalman filter is used to extract the fundamental components of voltage and current with a little delay and then they are used as inputs for the differential method. The proposed method is evaluated using some simulation signals and practical records from several EAFs in Mobarekeh steel company in Esfahan – Iran. [ABSTRACT FROM AUTHOR]

This study investigates the impact of different flexible AC transmission system (FACTS) devices on critical power quality (PQ) phenomena including voltage sags, harmonics and unbalance from the perspective of both mitigation effect and potential negative impact. The FACTS devices, including static VAR compensator, static compensator (STATCOM) and dynamic voltage restorers, are modelled in commercially available software PowerFactory/DIgSILENT to study their impacts on the critical PQ phenomena. Two control strategies, voltage regulation and reactive power compensation, are considered for STATCOM. For DVR, a PI‐controller is developed for the purpose of voltage sag mitigation. The merit of the proposed controller is presented by the dynamic response of during fault voltage and the capability of post‐fault voltage recovery. The study is carried out on a large‐scale generic distribution network. The impact of various devices on PQ phenomena is assessed using appropriate evaluation methodologies, and the results obtained with and without mitigation are presented and compared using heatmaps. [ABSTRACT FROM AUTHOR]

In this study, an interior point optimisation‐based control algorithm is proposed for three‐phase distribution static compensator under distorted AC mains. The proposed algorithm is used to determine the optimal value of load fundamental conductance and susceptance, which minimises the supply apparent power, subjected to predefined total harmonic distortion (THD) and individual harmonic distortion limit of supply current as per international guidelines. Unlike the other optimisation techniques, this technique is based on matrices calculations, which makes it effective during load dynamics. The proposed control scheme is implemented for mitigating multiple power quality issues such as load balancing, reactive power compensation and harmonics suppression in power factor correction and zero‐voltage regulation modes under linear and non‐linear loads. [ABSTRACT FROM AUTHOR]

Low voltage feeders (LVFs) experience several voltage quality (VQ) issues such as voltage drop at network peak periods, voltage rise at middays when high number of rooftop photovoltaic cells (PVs) are existing in the feeder, rapid voltage fluctuations as the results of the clouds effects on the power generation of PVs, and voltage unbalance due to the inherent random characteristics of the single‐phase loads and PVs. This study addresses these problems by proposing the concept of coupling the neighbouring LVFs. Based on this concept, two or more LVFs of the same distribution transformer or different distribution transformers are interconnected to support each other and minimise the VQ problems. First, the performance of LVFs in the existing form is discussed and three approaches of coupling the LVFs are presented. Among the presented techniques, coupling of LVFs through a distribution static compensator (DSTATCOM) at the end of the feeder is proposed and focused as an effective technique with minimal side effects such as power losses and cost. Proper dynamic control methods are also proposed for the DSTATCOM and the performance of such a system is investigated under steady‐state and dynamic conditions via numerical analysis and simulation studies in MATLAB and PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

Unlike the traditional methods that only take static voltage stability or minimum network loss into consideration when optimising capacity of distribution static synchronous compensator (D‐STATCOM), a new approach is proposed with considering the risk of voltage sag as well as the network loss and the investment cost of D‐STATCOM. This approach can balance the investment cost and technical performance. Monte Carlo method is used for the random setting of fault types and locations to obtain the original probability of voltage sag under some given configuration schemes. Moreover, through revealing the hidden relationship between the original probability and the real‐time load, the converted probability is presented to fit the expression for calculating the original probability of voltage sag with respect to the size of additional D‐STATCOM. Finally, a single‐objective capacity optimisation model is established to obtain the optimum size of additional D‐STATCOM, which is based on the economic assessment method of risk. The proposed method is validated in Chinese Dongguang Distribution Networks. The result confirms this method can not only reduce the loss of voltage sag, but also significantly improve the efficiency of D‐STATCOM. [ABSTRACT FROM AUTHOR]

Voltage sag is the most important power quality problem. The classical solution to protect industrial processes against voltage sags is based on the use of a large series voltage compensator (SVC), such as the dynamic voltage restorer. Although the SVCs are a general solution, in most cases alternative measures should be checked before purchasing such an expensive piece of hardware. For instance, some adjustable speed drives (ASDs) have embedded protection functions to mitigate voltage sags. In addition, contactors and power line carriers could be protected by low-power single-phase square-wave SVCs, which have been shown to be cost effective. This paper shows that, using the “ride-through” function of ASDs combined with cost-effective square-wave SVCs, a significant improvement in the ride-through capability of the protected process is achieved. Extensive testing of a low-power ASD panel supports the proposed voltage sag mitigation alternative. [ABSTRACT FROM PUBLISHER]

The introduction of distributed generation (DG) into low voltage (LV) systems demands that the generation system remain grid connected during voltage sags to ensure the operational stability. The DG consisting of fixed speed squirrel cage induction generator (SCIG)-based wind turbines is unable to provide reactive power control and needs a dedicated compensating device. Under asymmetrical grid faults the negative sequence flux circulation in the airgap introduces the torque oscillations that lead to the reduction of lifetime of the generation system. This paper proposes the use of distributed constant power loads (CPLs) for asymmetrical fault ride through (FRT) instead of using a centralized STATCOM. It has also been observed that the compensation of negative sequence voltage improves the performance of SCIG by eliminating the torque ripples. The compensation of positive sequence voltage avoids a possible voltage collapse at the LV distribution level and improves the reliability and stability of the wind farm. Centralized compensation of the asymmetrical grid fault by a STATCOM is compared with the distributed compensation by CPLs. The results suggest that each individual CPL injects lower current for maximum FRT enhancement compared to a dedicated STATCOM. [ABSTRACT FROM AUTHOR]

Solid-state transformer (SST) has been regarded as one of the most important emerging technologies for traction system and smart grid application. This paper presents the system design and performance demonstration of a high-voltage SST lab prototype that works as the active grid interface in smart grid architecture. Specifically, the designs of the key components of the system, including both power stage and controller platform, are presented. In addition, the advanced control system is developed to achieve high-performance operation. Furthermore, integration issues of SST with dc microgrid are presented. Lastly, tests under different scenarios are conducted to verify the following advanced features of the presented SST technology: 1) VAR compensation; 2) voltage regulation; 3) source voltage sag operation; and 4) microgrid integration. [ABSTRACT FROM AUTHOR]