MITIGATION VOLTAGE SAG USING DVR WITH HYSTERESIS-ANN CONTROL ON DISTRIBUTION SYSTEM PUJON FEEDER LINE

The increase of sustainable energy sources and integration with the power distribution grid produced power quality (PQ) problems such as voltage sag and voltage swell. These problems are produced in the power distribution systems due to multiple reasons that affect sensitive loads. Voltage sag and voltage swell mostly occurring Power quality complications in the power system. These power quality issues in the power distribution system can be mitigated by using custom power devices, Dynamic Voltage Restorer (DVR) is the newly introduced device. Different techniques and algorithms have been used to mitigate these problems. In this research work, an ultra-capacitor-based DVR and a super-twisting sliding mode controller are used for the said problem. The addition of energy storage, such as an ultra-capacitor, to a dynamic voltage restorer, creates a voltage that can alleviate voltage issues such as sag and swell. For both the voltage sags and voltage swells, a high voltage is necessary for a short spell. A dynamic voltage restorer is an apparatus that is linked between the voltage source and the load side using an injection transformer to input voltage into the power distribution side to remedy a problem that has a significant impact on the load voltage. With the inclusion of a dynamic voltage restorer and sliding mode controller, the system will be able to fix PQ issues such as voltage sag and swell on its own, rather than relying on the grid as in past years. MATLAB/Simulink R2018a has been used to conduct simulation studies. Simulation studies have demonstrated that the proposed scheme is more effective, simple, robust, and more flexible and has a better mitigation time of 2.5 milliseconds and a total harmonic distortion of less than 5% as per IEEE standards.

One of the major power quality problems in distribution systems are voltage sags. This paper deals with a dynamic voltage restorer (DVR) as one of the different solutions to compensate these sags and protect sensitive loads. However, the quality of DVR output voltage, such as THD, is important. This paper present a new configuration of DVR based on flying capacitor multicell (FCM) converter. The main properties of FCM converter, which causes increase in the number of output voltage levels, are transformer-less operation and natural self-balancing of flying capacitors voltages. To avoid any exchange of active power in compensation process, the proposed DVR is controlled by energy minimized compensation strategy which is explained in details for general unbalanced voltage sags. Also, the proposed voltage sag detection method as well as proposed DVR reference voltage determination method based on synchronous reference frame (SRF) is adopted as the control system. The proposed DVR is simulated using PSCAD/EMTDC software and simulation results are presented to validate its effectiveness.

Problem statement: ANRPC is a refinery based in Alexandria, Egypt. The plant was subjected to several shutdowns due to tripping of large induction motors, either by under voltage or by over current relays, sometimes by the mechanical protection. The main cause for such unplanned shutdowns was voltage sags. The Dynamic Voltage Restorer (DVR) has recently been introduced to protect the industrial facilities from voltage sags and other voltage disturbances. Existing configurations and control techniques for the DVR aim at protecting industries of high-tech, loads with adjustable speed drives and other power-electronic based loads. Industries with induction motors loads require a complete different approach for the design and control of a suitable DVR. Owing to the inherit inertia of the induction motors and their capability to withstand short-duration, shallow sags, in addition to its tolerance to phase jumps, a DVR with low cost, fast response and simple controller could be configured to fulfill the voltage restoration requirements. Approach: In this study, a simple DVR was proposed, which utilized the classical Fourier Transform (FT) for sag detection and quantification, a controller based on feed-foreword technique which utilized the error signal (difference between the reference voltage and actual measured voltage) to trigger the switches of an inverter using a Pulse Width Modulation (PWM) scheme. The proposed DVR utilized energy from other available feeder or from energy storage unit through a rectifier. Modeling and simulation of the proposed DVR was implemented in the Matlab/Simulink workspace. Results: Simulation results showed that the proposed DVR was efficient in mitigating balanced, unbalanced, multistage and consecutive sags, as well as swells (over-voltages). The main shortcoming of the DVR, being a series device, is its inability to mitigate complete interruptions. Conclusion: The DVR should be configured with respect to the load requirements. With respect to induction motors loads with inherit inertia and insensitivity to phase jumps, the proposed DVR would be of lower cost, simpler controller and faster response.

When a sudden load is connected to the distribution system Voltage sag takes place. DVR (Dynamic Voltage Restorer) is one such custom power device which helps in mitigating voltage sag. The DVR injects required volt-ampere to the system in order to maintain nominal balanced sinusoidal voltage at the load. The operation of DVR is depends on the control technique used. In this paper four control techniques are used, the techniques used are pre sag compensation method, in phase compensation method, energy optimization method and in phase advanced compensation method for mitigation of voltage sag. The performance of all the four methods compared. It is observed that in phase advanced compensation method has given better results in magnitude of voltage sag and THD compared to other methods. The simulations are carried out by using MATLAB / SIMULINK software.

A product that might improve voltage sag and swell change and integration of energy storage is the dynamic voltage restorer (DVR). Ultra capacitors, or UCAPs, are conducive in relieve voltage swells and sags which compose a challenge to high power for concise periods of time. In the end, both high power density and low energy density are consummate. One vital outcome of the ongoing study is that the DVR form accommodate rechargeable UCAP-based energy storage. When this system is assimilate, it will banish commitment for the grid to monitor for foible on the grid as long as the UCAPDVR system wield as an active power source and self-adjust to indemnify for unforeseen voltage swells and sags. An engrossing way to lessen sag is to utilize a dual-way DC-DC converter connected to an ultra-capacitor or dynamic voltage restorer to provide an accurate dc-link output voltage for the DVR. As a result of the integrated UCAP- DVR's advancement, speedy harmonic distortion is mitigated by reducing transient voltage swells and sags simultaneously. The PI controller will be leaned over other controllers in this specimen. A suggested framework is confirmed by virtue of, simulations using MATLAB/Simulink software.

This paper proposes Interline Dynamic Voltage Restorer (IDVR) to mitigate voltage sag, while its DC link energy is restored by phase shifting transformers. The Dynamic Voltage Restorer (DVR) was proposed as a solution to Voltage Sag compensation involving considerable amount of real power injection into the system which entirely depends on the energy storage capacity of DVR thus limiting its capabilities. The extension of the Dynamic Voltage Restorer leads to the concept of IDVR which consists of two DVRs sharing a common DC link. Usually one of the DVR's of IDVR compensates voltage sag while other DVR replenish the energy at DC link. In this paper a new concept of IDVR is proposed where one DVR compensates the Voltage Sag while the energy at the DC link is replenished by other DVR using the phase shifting transformers. The concept is simulated in MATLAB Simulink and performance of IDVR is investigated. Simulation results presented for a three phase example system with voltage sag demonstrates the effectiveness of the proposed method.

Dynamic voltage restorer (DVR) is conventionally utilized in the electrical distribution system to mitigate the voltage sag and swell on point of common coupling of sensitive consumers. In this paper, a novel DVR based on power electronic transformer (PET) is proposed to mitigate the symmetrical and asymmetrical voltage sag and voltage swell. PET is connected between DC power supply and multilevel inverter to provide transitive DC voltage for DC-link of DVR. PET has effectually and flexibly created relevant DC voltage with required magnitude and low distortion. The performance of suggested DVR based on PET has been evaluated under occurrence of different disturbances in the electrical distribution system. Ultimately, the simulation results have confirmed that DVR-PET can significantly mitigate the symmetrical and asymmetrical voltage sag and voltage swell on sensitive consumers.

In the current energy landscape, power quality (PQ) emerges as a critical concern. Even when there is no fault on a line, PQ issues are common in all power networks since 90% of power systems’ loads are variable or inductive in nature. Variable loads cannot be avoided; hence, PQ concerns such as voltage swelling and sag will always arise. Voltage sag is one of the main issues within a distribution network, resulting in financial losses for the utility company and the customer. The Dynamic Voltage Restorer (DVR) effectively addresses voltage sags and minimizes total harmonic distortion (THD) in the distribution network. This paper proposed a novel control strategy to increase the PQ in a system. A Frilled Lizard Optimization-optimized fuzzy PI controller is proposed in this work to control the inverter. This proposed method improves the DVR’s ability to correct voltage sag and reduce total harmonic distortion as soon as possible. The PI control scheme is utilized initially to reduce the oscillations and remove the steady-state error. To increase the tendency rate of the error to zero, the PI method is applied to a fuzzy logic-based compensatory stage. The proposed approach is validated using pro-type models, as well as mathematical and Simulink modelling. In the Results Section, the performance of the proposed controllers with the DVR is tabulated and compared with other DVR controller schemes described in other research papers.

In this paper a new control algorithm for self-supported Dynamic Voltage Restorer (DVR) is analysed. DVR is used to mitigate the power quality problems in terminal voltage like voltage sag, swell, harmonics etc. Here two PI (Proportional Integrator) controllers are used for regulating the DC bus voltage and the load voltage. The focus of this paper is to reduce the active power injected by DVR. Synchronous Rotating Frame (SRF) theory is used to extract the fundamentals of terminal voltage and reference voltage is genereted. The error between sensed load voltage and reference load voltage is used to generate the control signal for the DVR. The compensation of voltage sag, swell, harmonics is evaluated using the Self-supported DVR. The DVR has been modelled using MATLAB software with its Simulink and Sim-power system (SPS) block set tool boxes.

Dynamic voltage restorers (DVRs) are used to protect sensitive loads from the effects of voltage sags on the distribution feeder. This paper presents and verifies a novel voltage sag detection technique for use in conjunction with the main control system of a DVR. In all cases it is necessary for the DVR control system to not only detect the start and end of a voltage sag but also to determine the sag depth and any associated phase shift. The DVR, which is placed in series with a sensitive load, must be able to respond quickly to a voltage sag if end users of sensitive equipment are to experience no voltage sags. A problem arises when fast evaluation of the sag depth and phase shift is required, as this information is normally embedded within the core of a main DVR control scheme and is not readily available to either users monitoring the state of the grid or parallel controllers. Previous research presented an additional controller, which required phase and sag depth information to manipulate the injection voltage vector returned by the main controller in order to prevent the DVR injection transformers from saturating. Typical standard information tracking or detection methods such as the Fourier transform or phase-locked loop (PLL) are too slow in returning this information, when either applied to the injection voltage vector, or to the supply voltages directly. As a result of this the voltage sag detection method in this paper proposes a new matrix method, which is able to compute the phase shift and voltage reduction of the supply voltage much quicker than the Fourier transform or a PLL. The paper also illustrates that the matrix method returns results that can be directly interpreted, whereas other methods such as the wavelet transform return results that can be difficult to interpret.

Power quality (PQ) is an important issue in power systems that reflects a measure of quality of energy supply to the consumers. Power electronics-based equipment is increasing in power systems that cause voltage distortions which may damage a sensitive appliance in the distribution grid. Besides, many electrical and electronic equipment is susceptible to power supply disturbances in modern industrial establishments. The most vital power quality issues affecting large commercial and industrial customers are momentary power interruptions and voltage sags. Usually, these PQ issues are associated with the faults that occur in the supplying power systems. Voltage sags are very common since they can be associated with the faults that happen remotely to the customer. Further, these PQ problems with about 4–5 cycles may cause an extensive malfunction to the sensitive equipment. Therefore, an appropriate solution is necessary to handle this problem. A Dynamic voltage restorer (DVR) is a custom power device (CPD) that can protect sensitive equipment against voltage disturbances and improve power quality in electrical distribution systems. In recent years, many CPDs have been developed to meet the need of the industries and their critical load establishment. The DVR is one of the most promising CPDs used to improve the power quality before feeding it to the sensitive load to protect electric appliances from damage. DVR is the combination of a voltage source inverter (VSI), which can impose the voltage in series through a series injection transformer (SIT) with the power distribution system during voltage sag. The required voltage compensation can be achieved by adopting the pulse width modulation (PWM) technique for VSI. The DVR's performance mainly depends upon the control system that includes voltage disturbance detection, reference generation, voltage & current control and PWM switching strategy. The main objective of the control system is to compensate for the disturbance at the earliest using a fast detection technique, optimum control variables for the control circuit and a suitable PWM switching methodology. Many such compensation methods and control techniques are proposed in the literature along with various DVR topologies which are analysed and studied in this chapter.KeywordsPower qualityDynamic voltage restorerVoltage source inverterPI controllerHarris hawk’s optimization (HHO) algorithm

Voltage sag is considered to be the most serious problem of power quality. It is caused by faults in the power system or by the starting of large induction motors. Voltage sag causes about 80% of the power quality problems in power systems. One of the main reasons for voltage sag is short circuit fault, which can be compensated for by a distribution static compensator (DSTATCOM) as an efficient and economical flexible AC transmission system (FACTS) device. In this paper, compensation of this voltage sag using DSTATCOM is reviewed, in which a sliding mode control (SMC) technique is employed. The results of this control system are compared with a P+Resonant control system. It will be shown that this control system is able to compensate the voltage sag over a broader range compared to other common control systems. Simulation results are obtained using PSCAD/EMTDC software and compared to that of a similar method.

Electric power aims to generate electrical energy and distribute to the end-user application at an acceptable voltage level. The quality of power will be affected by various factors like voltage sag, swell, harmonic and Power interruptions, etc. The major reason behind the deteriorations of the power quality is nonlinearity in loads which draws out harmonics. Due to this nonlinearity, all loads cause disturbances in the voltage waveform. In this paper, an Intrinsic Space Vector Transformation (ISVT) based solar fed Dynamic Voltage Restorer (DVR) is connected in series with the power grid to compensate for the reactive power. The operation of the proposed DVR model produces reactive power based on the voltage sag and voltage swell. The ISVT controller produces an appropriate pulse to the voltage source inverter (VSI), which delivers a suitable reactive power to compensate for the sag and swell voltages in the grid. Moreover, solar fed DVR reduces Total Harmonic Distortion (THD) value at the time of voltage sag mitigation. The performance of the proposed system is evaluated by analysing the power consumption and efficiency. Finally, the proposed system is compared with other existing methods. The simulation is carried out using MATLAB SIMULINK 2017b software.

Dynamic voltage restorers (DVR) have gained popularity as a cost-effective solution for protecting sensitive loads from balanced and unbalanced voltage sags. DVR implementation has been proposed at medium voltage (MV) levels to safeguard downstream or sensitive loads from such disturbances. This paper presents a case study of a DVR implemented on a medium voltage (11 kV) system, modelled in MATLAB/Simulink environment. The impact of the DVR was evaluated under both unbalanced and balanced conditions for linear loads, where voltage sags of varying durations and depths were applied. The analysis focuses on voltage restoration capability and the resulting waveshape at the load side. The results demonstrate that the DVR compensates for the balanced sags up to 0.5 p.u. For sags where the retained voltage was lower than 0.5 p.u., partial compensation was achieved by the DVR. Under unbalanced conditions, particularly during single-phase-to-ground faults, the DVR helps maintain a stable voltage above 0.9 p.u. These findings validate the DVR's capability as a viable solution for voltage sag mitigation in MV networks and highlight design considerations for optimal performance under diverse fault conditions.

Dynamic voltage restorers (DVRs) are now becoming more established in industry to reduce the impact of voltage sags to sensitive loads. However, DVRs spend most of their time in standby mode, since voltage sags occur very infrequently, and hence their utilization is low. In principle, it would be advantageous if the series-connected inverter of a DVR could also be used to compensate for any steady-state load voltage harmonics, since this would increase the power quality "value-added" benefits to the grid system. However, before this can be done, consideration must be given to the control of steady-state power through the DVR, the increased losses, and the low modulation depths at which the scheme must operate to achieve acceptable harmonic compensation performance. This paper presents a selective harmonic feedback control strategy that can be easily added to medium-voltage DVR systems to provide voltage harmonic compensation capabilities with minimal effect on the sag compensation performance of the basic DVR. The proposed controller has been experimentally verified on a medium-voltage (10 kV) three-phase DVR prototype under a range of conditions, including distorted supply voltages, nonlinear loads, and operation during distorted voltage sags.