A Mobile Agents Based Multi-Objective Optimization Resolution for Power Quality Problem Location

In This work a power quality (PQ) problem in an industrial plant is analyzed and its possible solutions explored, specifically regarding voltage sags. It is analyzed a plant's electrical system sensitivity regarding voltage sags, how does the magnitude depression and its duration affect the performance of the electrical loads (mainly induction motors). Several proposals are discussed and explored for voltage sag mitigation and their feasibility for the plant's PQ problem. Finally, settings of the voltage sag mitigation equipment (timer or latching relay) are made analyzing voltage recovery times after voltage sag has occurred.

This paper introduces a novel automatic hybrid classifier to detect and classify the Power Quality(PQ) problems in power systems using Wavelet Packet Transform (WPT) and Artificial Neural Networks (ANN). Various PQ events like Normal, Sag, Swell and Interruptions are obtained by modeling three phase distribution system using MATLAB simulink. For classification, the selection of suitable features from the disturbance signal is extremely important. Recent literature survey deals with various signal processing techniques like Fast Fourier Transform (FFT), Discrete Wavelet Transform (DWT) and Wavelet Packet Transform (WPT) were used for feature extraction. From the above techniques, the main issues addressed are selection of optimal feature subset and the design of ANN architecture model. To build a competent and robust classifier, it is essential to extract the utilizable feature vectors from the disturbance signal that can optimize data size as well as incorporate the main characteristics of the signal. This paper addresses these issues, and the distinctive feature vectors are obtained with reduced number of coefficients by using Energy Entropy based WPT. From these, the best discriminative feature vectors with reduced number of coefficients are obtained and are used as input to ANN, so that the burden over classification can be reduced. The classification performance is compared with FFT based ANN. The simulation results obtained have significant improvement over existing methods. Thus the proposed hybrid classifier provides the most excellent detection among PQ problems that arises in real time by improving classification accuracy in terms of both computation time and means square error.

Having an inter-tie between low/medium voltage grid and distributed generation (DG), both exposes to power quality (PQ) problems created by each other. This paper addresses various PQ problems arise due to integration of DG with grid. The major PQ problems are due to unbalanced and non-linear load connected at DG, unbalanced voltage variations on transmission line and unbalanced grid voltages which severely affect the performance of the system. To mitigate the above mentioned PQ problems, a novel integrated control of distribution static shunt compensator (DSTATCOM) is presented in this paper. DSTATCOM control helps in reducing the unbalance factor of PCC voltage. It also eliminates harmonics from line currents and makes them balanced. Moreover, DSTATCOM supplies the reactive power required by the load locally and hence, grid need not to supply the reactive power. To show the efficacy of the proposed controller, several operating conditions are considered and verified through simulation using MATLAB/SIMULINK.

Air source heat pump (ASHP) is common electric heating equipment in the "coal to electricity" project in China. ASHPs connected into the power grid can cause reactive power shortage, voltage sag, harmonic current violation and other power quality problems. Based on the typical topological structure of ASHPs and the mechanism of power quality problems, the simulation model of ASHP is built, and the power quality emission characteristics of ASHP connected to distribution network are studied. The power quality problems caused by ASHP connected to distribution network are measured and analyzed. The results of simulation and measurement analysis show that fixed frequency ASHPs will generate large reactive power when start, and will cause voltage sag. And the harmonic violation problem will occur when variable frequency ASHP runs.

Problem. Electrical distribution networks are plagued by power quality problems, which have a negative impact on sensitive electrical loads. These problems include reactive current, low power factor on the load side, and voltage harmonics, voltage sags and voltage swells on the grid voltage side. To address these issues, a unified power quality conditioner (UPQC) that combines shunt and series compensators is suggested. The goal of the work is to implement a UPQC integrated with a photovoltaic (PV) system to mitigate power quality problems in the power system, and boosting the grid supply through power injection from the PV system. Methodology. One of the less complex and effective ways to improve the grid’s voltage quality is by using the unit vector template generation (UVTG) strategy as the composition technique (UPQC-P) through the UPQC series compensator. The synchronous reference frame (SRF) strategy through the UPQC shunt compensator to improve the current quality on the load side is used. To further optimize the SRF strategy, it is used the snake optimization (SO) to find the optimal values for the PI controller’s parameters. Results. The UPQC-PV is used to mitigation the power quality issues in the grid and loads by UVTG and SRF techniques in series and shunt compensators, respectively. Scientific novelty. The composition technique (UPQC-P) through a series compensator and uses the SO for tuning the PI controller in the shunt compensator. Practical value. This study reduces the total harmonic distortion (THD) in the load voltage to 0.57 %, while the THD in the grid voltage remains at 10 %. It restores the load voltage to its reference value of 230 V during voltage sags (down to 161 V) and swells (up to 300 V) in the grid. Additionally, it mitigates the low power factor on the load side (0.707 lagging) to achieve a unity power factor in grid current, balances the unbalanced load current to a balanced grid current, and enhances grid stability by injecting power from the PV system into the grid. References 33, table 3, figures 7.

Electric railway power systems (ERPS) as one of the most critical and high-power end-user loads of utility grids are characterized by outlandish power quality (PQ) problems all over the world. The extension and evolution of different supply topologies for these systems has resulted in significant and various forms of distortions in network voltage and current in all ERPS, the connected power system, and adjacent consumers. During the last years, numerous studies have been offered to investigate various aspects of PQs in a specific supplying topology. Variation in the supply structure of the ERPS and different types of locomotives has propelled the observation of different PQ phenomena. This versatility and development have led to confront considerable types of two-way interactive interfaces as well as reliability and PQ problems in ERPS. In addition, the lack of standards explicitly dedicated to ERPS has added to the ambiguity and complexity of this issue. In this paper, an extensive review of PQ distortions and phenomena in different configurations of ERPS is proposed and a systematic classification is presented. More than 140 scientific papers and publications are studied and categorized which can provide a fast review and a perfect perspective on the status of PQ indexes for researchers and experts.

Power quality (PQ) problems include harmonics, voltage flicker, three-phase imbalance, voltage swell/sag, interruption, switching transient and so on. Identification of accurate location and occurrence time of PQ problem is important for understanding the underlying cause and to prevent future occurrence. This study presents a new method for placement of power quality measurement facilities to identify PQ problems. The power harmonics and capacitor switching transients are used as disturbance sources for illustration. The proposed method first utilises harmonic voltages and wavelet coefficients as PQ features. An enhanced genetic algorithm is proposed for solving the modified K-means clustering to place PQ measurement monitors. Simulation results for an 18-bus system show that the proposed approach is effective in comparison with the existing approaches.

Multilevel inverters are currently the subject of extensive investigation and are used primarily for medium and high voltage distribution systems. The work presented in this paper provides a cost-effective and realistic solution to mitigate power quality (PQ) problems. A Cascaded H-Bridge multilevel inverter (CHB-MLI) has been configured as a shunt active power filter (SAPF). It is well reported that large-scale use of power electronics-based devices leads to several PQ problems such as poor power factor, unregulated dc voltage, harmonics, voltage regulation etc. In this paper, an improved immune feedback control algorithm is proposed and developed to mitigate PQ issues by predicting the weighted active component of load current and to generate reference current for the grid. Extensive MATLAB simulation and experimental work have been reported for validation on a single-phase system. A low prototype model is developed in the laboratory to study and compare the steady-state and dynamic results of the proposed controller with conventional Least Mean Square (LMS) and Immune algorithm.

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.

This study deals with the stabilization of grid connected wind farms. Operation of wind turbines has an impact on the power quality and reliability at the connected electric network. Power quality problems such as voltage flicker and harmonic distortion along with reliability issues are some major concern and in this work the flicker & harmonics issues are considered. Wind turbine connected to an induction generator and synchronous generator is modeled using PSCAD software to analyze power quality and reliability problems. Due to continuously varying wind speed components, the active and reactive power along with terminal voltage fluctuates continuously. A new type of static synchronous compensator (STATCOM) unit is developed to inject reactive power by switching IGBT(s) to mitigate power quality problems and to get stable grid operation. By connecting proposed Electro-Mechanical Switched Capacitor (EMSC) based STATCOM into the grid, reactive power and terminal voltage can be controlled effectively with varying wind speed.

Power system is broadly divided into three stages, generation, transmission and distribution. There are several challenges in each stage which are needed to be addressed. This paper concentrates on the challenges in distributed systems called power quality. Power quality improvement is a major concern in the distributed system. There are several power quality problems like voltage sag, harmonics, flickering, distortions etc. Two major problems considered in this paper are the voltage sag and harmonics. To handle with these power quality problems Flexible AC Transmission Systems (FACTS) devices are utilized. Interline Dynamic Voltage Restorer (IDVR) is proposed to eliminate the voltage sag and harmonics. The major aspect of IDVR is being able to replenish energy to the DC link while injecting required voltage in more than one power line unlike the Dynamic Voltage Restorer (DVR). The building blocks of IDVR used for injecting the voltage can either be voltage source inverter (VSI) or current source inverter (CSI). An IEEE 8 bus system is considered, consisting of generation, transmission and distribution levels. The sensitive loads are assumed to be connected at the distribution side The IDVR is installed near the distribution side. The performance of the IDVR in reducing voltage sag and harmonics as its building block either VSI or CSI is investigated and compared in this paper in MATLAB environment.

The unified power quality conditioner (UPQC) is a power conditioning device, which is a integration of back to back connected shunt active power filter (APF) and series APF to a common DC link voltage. For improvement of power quality (PQ) problems in a three-phase four-wire distribution system, two topologies are proposed in this paper. A comparative analysis of these topologies along with the most common four-leg voltage source inverter (VSI) based topology of four-wire UPQC is discussed in this work. The performance of each topology of UPQC is evaluated for different PQ problems like power-factor correction, load balancing, current harmonic mitigation, voltage harmonic mitigation and source neutral current mitigation. The synchronous reference frame (SRF) theory is used as a control strategy of series and shunt APFs. The simulation results using MATLAB/Simulink enviournment are obtained, which support the effectiveness of these topologies of UPQC for power quality improvement.

This chapter introduces the custom power device to solve the various kinds of power quality (PQ) problems. It is generally known as flexible AC transmission system (FACTS) and D-FACTS (FACTs used for low voltage and low current rating in AC distribution system). The D-FACTS are various types like dynamic voltage restore (DVR), static compensator in distribution system (D-STATCOM), and unified power quality conditioner (UPQC). The third one is combination of DVR and D-STATCOM, which is known as UPQC. The UPQC can compensate all the PQ problems. Comprehensive knowledge of UPQC is presented here to understand the trade value of this device. This chapter is organized as follows: The evaluation of power electronic based devices is presented in the background part of this chapter where custom power devices (CPDs) are also discussed. And operating principle with the Matlab model of UPQC and results are presented in the section titled “Working Principle of Unified Power Quality Conditioner (UPQC).” The scope of the one of the functional power electronic based devices are presented in section titled “Scope of UPQC.” At the end, this chapter is concluded.

Large penetration of PV in a microgrid connected distribution system impacts the weak utility distribution system by creating various power quality (PQ) problems such as voltage sag or swell, unbalance, harmonics and DC current injection etc. These power quality (PQ) issues and they are broadly classified as current related PQ issues and voltage related PQ issues. The current related issues are mitigated by one of the custom power device connected in parallel namely distribution static compensator (DSTATCOM), by operating in current controlled mode (CCM). The dynamic voltage restorer (DVR) is another custom power device (CPD) for mitigating voltage related PQ problems. It is reported in literature that, a suitable modification of a DSTATCOM can achieve the capability to compensate voltage disturbances also. A multiple functions of DSTATCOM is thus achieved by operating the device so as to mitigate the current and voltage related PQ issues. Thus a multi-functional control strategy allow DSTATCOM to compensate voltage and current related PQ problems. This paper presents a hybrid DSTATCOM which can be used in highly PV penetrated distribution system to control the voltage and current related PQ issues. The topology uses a suitably designed foreign inductor, connected between the grid and load. A dynamic reference load voltage generation algorithm using instantaneous symmetric component theory (ISCT) is presented. The simulation is done with real time voltage level using MATLAB/SIMULINK.

Linear growth of Electrical energy demand in the world resulting in a consistent increase in the short circuit level in power system network, which effects in blackout. Usage of renewable energy to meet demand without proper synchronization will result in power quality problems like voltage sag, swell etc. Power System engineers at utility side are facing challenges of integrating new generation of power and renewable energy into existing power systems network. The High Temperature Superconducting Fault Current Limiter (HTSFCL) and Power Electronic Fault Current Limiter (PEFCL), offers a possible solution to the power system network. Power quality problems caused by short circuit and renewable energy sources which has been simulated and analysed in this paper. The simulated results are analysed for the effect of resistive HTSFCL in both single and three phase power system network performance to reduce fault current level and PEFCL for both single and three phase power system network recital for fault current and power quality and also the total harmonic distortion (THD) is analysed during the fault with MATLAB Simulink.