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This research proposes two approaches for determining the required frequency and modulation index for a pulse-width-modulation (PWM) system in a variable frequency drive (VFD) to control the speed of the threephase induction motor. The first approach which is the reverse direction algorithm (RDA), uses a set of equations to calculate the necessary frequency and voltage for maintaining a constant motor speed under varying load conditions. The second one involves training a neural network (NN) on data collected by the RDA, which can then be used to continuously adjust the motor speed in real time to adapt to changing load torque requirements. Simulation and laboratory models for the three-phase induction motor are built and the proposed RDA-NN controller is examined. Results have proved that the proposed controller is effective in providing a stable and responsive motor speed control system. [ABSTRACT FROM AUTHOR]

The objective of this study is to create a variable frequency drive (VFD) trainer kit, assess the practicality of the developed VFD educational tool, and evaluate its impact on the academic performance of industrial electronic engineering students, particularly in the area of electronic control systems. The study utilizes the ADDIE model and customized to meet the requirements and consists of the following phases: analysis, design, development, implementation, and evaluation. There were 130 respondents consisting of 122 vocational students, 1 industry expert/practitioner in the field of VFD, 1 vocational training center instructor, 4 vocational teachers, and 2 lecturers. Data were collected using questionnaires with 4 Likert scales from strongly agree to strongly disagree, feasibility assessment sheets from media experts and material experts, interviews, and electronic control system learning outcomes tests. The learning media receives a "highly feasible" and the job sheet obtains 67 "highly feasible". Moreover, the level of effectiveness of the learning media receives a score of 0.724, indicating high effectiveness. Therefore, they have proven to be effective in enhancing student learning outcomes and developing their proficiency in controlling the speed of electric motors. This will help bridge the gap between the industry's skill requirements and the skills taught in schools. [ABSTRACT FROM AUTHOR]

The use of a variable frequency drive (VFD) for sucker-rod pump units (SRPUs), widely employed in oil extraction, enhances the energy and technological efficiency of oil production and reduces equipment wear. However, its application is hindered by unstable operation under insufficient balancing of the SRPU and sensitivity to short-term voltage dips, which frequently occur in the extensive electrical networks of oil fields. Insufficient balancing of the SRPU leads to the occurrence of a period within the pumping cycle where the motor operates in generator mode, caused by the unevenness and reversal of the resistance torque of the working mechanism. The motor’s transition to generator mode, as well as voltage dips in the power supply, causes the voltage in the DC link of the VFD to exceed the set limits, resulting in the drive being shut down. To investigate the processes during the operation of sucker-rod pump units and to test methods for mitigating the negative impact of generator mode and voltage dips in the power supply network on the VFD, a model of the “power grid – variable frequency SRPU drive” system with a load characteristic of this application was developed in Matlab Simulink. A series of experiments were conducted, and the results were analyzed. The suppression function of the generator mode was examined, and the feasibility of its application to real SRPUs was evaluated. The use of an uninterruptible power supply system based on battery energy storage to prevent operational interruptions during different levels of power supply voltage dips was analyzed. The resulting model can be used for general analysis of operability and stability, as well as for verifying the correct selection of key elements in the design of sucker-rod pump unit systems with variable frequency drives.

A modular multilevel converter (MMC) is reflected to be an emerging multilevel topology for medium- to high-power induction motor drives due to its highly reliable structure, modularity and scalability. However, large circulating current produced in the phase arm of MMC during low-speed operation of induction motor drive is a major drawback of MMC, which leads to affect the size of a sub-module capacitor, inductor and switch rating. To mitigate the circulating current and improve the performance of MMC-fed induction motor drive, this paper proposed a new circulating current error compensator (CCEC) technique with reduced arm current peak. By proper control of instantaneous voltage between arms and DC link current, second-order fundamental frequency current harmonic from circulating current is eliminated which leads to a significant reduction in circulating current. A comparative evaluation between conventional control scheme and the proposed CCEC control scheme is presented. The performance and effectiveness of the proposed CCEC technique are validated using a MATLAB-based simulation. Scale-down laboratory experimental setup is also developed to check the effectiveness of the proposed CCEC control technique. Reduction in circulating current for entire speed range with improved DC link current profile is observed as compared to conventional circulating current suppression control. [ABSTRACT FROM AUTHOR]

Subsurface drainage plays a crucial role in excess water removal through perforated pipes buried in the soil. The Red River Valley of eastern North Dakota and west central Minnesota often requires pumped drainage outlets due to its flat topography, with many modern systems incorporating variable frequency drives (VFD) for improved efficiency. VFDs adjust pump speeds to match drainage needs, but this dynamic operation complicates accurate flow rate estimation for edge-of-field monitoring. This project aimed to devise an automated method for calculating flow rate estimates from VFD pumping systems involving tank geometry, operational water levels, and pump duty cycling. Linear regressions with calibration data from a transit-time ultrasonic flowmeter produced mixed outcomes. Some linear regressions revealed errors in calculated versus measured flow rate of =14%, while other regressions showed errors nearing 40%. To address this, future efforts should explore methods incorporating the pump's electrical characteristics. This approach would provide a more accurate representation of the unstable and intricate pumping operations during transient conditions. [ABSTRACT FROM AUTHOR]

Induction motor driven pumps are a staple in many sectors of industry, and crucial equipment in naval ships. Such machines can suffer from a wide variety of issues, which may cause it to not perform its function. This can either be due to degradation of components over time, or due to incorrect installation or usage. Unexpected failure of the machine causes downtime and lowers the availability. In some cases, it can even lead to collateral damage. To prevent collateral damage and optimise the availability, many asset owners apply condition monitoring, measuring the dynamic response of the system while in operation. Two high-frequency measurement methods are widely accepted for the detection of faults in rotating machinery at an early stage: vibration measurements, and motor current and voltage measurements. These methods can also distinguish between different failure mechanisms and severities. The dataset described in this article presents experimental data of two centrifugal pumps, driven by induction motors through a variable frequency drive. Besides measurements of behaviour that is considered healthy (new bearings, well aligned), the machines have also been subjected to a variety of (simulated) faults. These faults include bearing defects, loose foot, impeller damage, stator winding short, broken rotor bar, soft foot, misalignment, unbalance, coupling degradation, cavitation and bent shaft. Most faults were implemented at multiple levels of severity for multiple motor speeds. Both vibration measurements, and current and voltage measurements were recorded for all cases. The dataset holds value for a wide range of engineers and researchers working on the development and validation of methods for damage detection, identification and diagnostics. Due to the extensive documentation of the presented data, labelling of the data is close to perfect, which makes the data particularly suitable for developing and training machine learning and other AI algorithms.

Wind and solar photovoltaic (solar-PV) power are highly variable and intermittent as exhibited by corresponding generation profiles. In the utilization of power directly for water pumping, the availability and reliability of water automatically followed the Renewable Energy Sources (RES) characteristics. On the other hand, Deferrable Irrigation Load (DIL), followed a specific irrigation water need profile. The DIL profile is determined by crop cycles and corresponding water needs. It was also affected by aspects of weather, mainly precipitation, temperature, and wind. This research considered the application of discrete switches and Variable Frequency Drives (VFDs) as a combined solution. Combined discrete and continuous switching through VFDs, to adapt pump load to DIL and RES profiles proved successful. Discrete switches engaged the exact number of pumps required to match an expected irrigation load. VFD further ensured continuous match of irrigation pump load to the anticipated DIL curve, through adjustment of pump speed points. Running of the system to adapt the pump power to the RES curve yielded better curve-fit results. The energy adapting technique was implemented to improve elasticity, hence the efficiency of the system. The results showed that the adapted system to the DIL curve-fit was 95.4% compared with a discrete-only system (91.35%). This represented a slight improvement of approximately 4.5%. The results demonstrated the smoother operation of the pump system and increased energy utilization efficiency. A further improvement on the control strategy for VFD coupled with the re-design of irrigation pipe networks was required to improve efficiency beyond 95.4%. [ABSTRACT FROM AUTHOR]

Increasing ship energy efficiency is essential to reducing fuel consumption and shipbased harmful emissions. In a ship's engine room, there are a lot of electric motors, and their energy consumption is remarkable. The effective operation of these electric motors becomes significant when taking into account ship energy efficiency with regard to the effects on the environment and climate change. The electrical, mechanical, and operational efficiencies of electric motors can be improved with a variable frequency drive. In order to improve the ship's overall energy efficiency, the electric motors used for engine room ventilation are examined in this paper using variable frequency drives for two different ambient temperatures. Energy consumption of the engine room ventilation fans is calculated and the change in the efficiency depending on the air temperature is analyzed. By using data from actual crude oil tanker ships, the outcomes are compared with those of the traditional system. The results indicate an energy consumption reduction of more than 80% is achievable by using VFD electric motors for engine room fans. The result corresponds to 153.279 kWh of energy instead of 613.116 kWh annually. [ABSTRACT FROM AUTHOR]

Most of the old machines installed in different industries are managed manually by system operators. This action makes their productivity low and not suitable to cover the needs in other sectors. In addition, these machines are not without risks due to the proximity of the operators to them. The installing a new full system instead of the old one on the same site requires very high costs. So, modernizing the same old system by making its operation automatic has become necessary to reduce the economic cost significantly. In this paper, an automatic control system based on programmable logic controller (PLC) for the cutting steel plate machine that had been managed manually in a factory is designed. The system includes an Encoder that is used to specify the length of the steel plate to be cut by sending a signal to the PLC. The system operation is completed by using human machine interface (HMI) unit to monitor and control the system performance by the system operator. A practical test for the developed system offered more productivity (more than 30%), more safety, reduces human efforts and the total daily production cost (less than one third). [ABSTRACT FROM AUTHOR]

In modern power systems, interharmonics have emerged as noninteger frequency components that appear in current or voltage signals. Double-stage AC-DC-AC converters have been identified as a primary source of interharmonics. Previous studies have highlighted modulation techniques, filters, passive components, unbalanced conditions and DC link effects as relevant factors. However, the interaction between these factors and the inertial properties of induction motors has not been explored. This study assesses various types of AC drives, including variable frequency drives (VFDs) and soft starters (AC choppers), to investigate their interaction with machine inertial properties in interharmonic generation. The employed technique for time-frequency spectral analysis is the wavelet synchrosqueezed transform combined with a clustering method. This paper demonstrates that the interaction of the inertial properties of low-power induction motors with the variations of the switching frequencies of the VFDs, the filters used in the DC link and a soft start indirectly contribute to harmonic generation and potentially to interharmonics in the electrical grid and the outputs of the inverter. [ABSTRACT FROM AUTHOR]

Currently, the most implemented solution for driving a pumping system (PS) at variable speed is using a variable frequency drive (VFD). Because most of the VFDs have integrated only one proportional-integral (PI) frequency controller whose parameters (proportional gain/the integration time) can be off-line tuned but cannot be changed during real-time operation, and many PS must operate in different regimes (at variable speed, variable flow rate, at variable pumping head or even at variable power, e.g., those powered by renewable energy sources), the adaptive control strategy proposed in this paper overcomes these problems with very good performances. The proposed adaptive control strategy uses only simple PI controllers for managing several operating regimes. The adaptive character is not ensured by re-tuning the PI controller parameters as in self-tuning controllers but by readjusting the control law through a change in the control loop depending on the controlled output of the process (pump speed, pump discharge, pumping head or absorbed power). The deviations of the mentioned controlled outputs from their referenced values are converted into electrical frequency error (the deviation of the current value from its reference), which is the regular input to the already tuned controller; therefore, no controller re-tuning is required. [ABSTRACT FROM AUTHOR]

The article discusses research which tested speed optimization using variable frequency drive fitted to dhan foundation dehuller to determine the effectiveness of dehulling speed with time of dehulling in selected minor millets. The study describes the conservation of power for efficient dehulling of minor millets. It tested minor millet grains for its moisture content and observed the performance and capacity of the double head dehuller, as well as head rice recovery after dehulling.

Perkembangan teknologi dan kebutuhan dunia industri terhadap kendali motor listrik menuntut dosen untuk mengupdate dan mengembangkan media pembelajaran. Salah satu media pembelajaran dalam mata kuliah pratikum adalah trainer, trainer kendali motor induksi menggunakan Variable Frequency Drive (VFD) yang telah dikembangkan harus dilakukan pengujian sebelum digunakan pada pembelajaran. Hal ini bertujuan untuk memastikan bahwa trainer yang dikembangkan memenuhi standar dan kriteria untuk media pembelajaran pratikum. Metode penelitian ini adalah pengujian langsung dilaboratorium pada Jog Dial dan External Potentio Meter. Jog dial merupakan mode kendali yang tersedia pada VFD dan External Potentio Meter yang terpisah dari peralatan VFD, dengan frekuensi sebagai set point. Hasil penelitian menunjukkan bahwa parameter terukur dengan baik sesuai datasheet peralatan dan komponen yang digunakan, sehingga trainer telah berfungsi dengan baik sebagai kendali motor induksi 3 fasa. Dengan demikian dapat disimpulkan trainer ini dapat digunakan sebagai media pembelajan pratikum khususnya pada kendali motor listrik industri.

Despite the recent interest in direct current (DC) power distribution in buildings, the market for DC-ready loads remains small. The existing DC loads in various products or research test beds are not always designed to efficiently leverage the benefits of DC. This work addresses a pressing need for a study into the development of efficient DC loads. In particular, it focuses on documenting and demonstrating how to best leverage a DC input to eliminate or improve conversion stages in a load's power converter. This work identifies how typical building loads can benefit from DC input, including bath fans, refrigerators, wall adapters, task lights, and zone lighting. It then details the development of several prototypes that demonstrate efficiency savings with DC. The most efficient direct-DC loads are explicitly designed for DC from the ground up, rather than from an AC modification.

Despite the recent interest in direct current (DC) power distribution in buildings, the market for DC-ready loads remains small. The existing DC loads in various products or research test beds are not always designed to efficiently leverage the benefits of DC. This work addresses a pressing need for a study into the development of efficient DC loads. In particular, it focuses on documenting and demonstrating how to best leverage a DC input to eliminate or improve conversion stages in a load's power converter. This work identifies how typical building loads can benefit from DC input, including bath fans, refrigerators, wall adapters, task lights, and zone lighting. It then details the development of several prototypes that demonstrate efficiency savings with DC. The most efficient direct-DC loads are explicitly designed for DC from the ground up, rather than from an AC modification.

Water is a precious resource for agriculture and most of the land is irrigated by tube wells. Diesel engines and electricity-operated pumps are widely used to fulfill irrigation water requirements; such conventional systems are inefficient and costly. With rising concerns about global warming, it is important to choose renewable energy source. In this study, SPVWPS has been optimally designed considering the water requirement, solar resources, tilt angle and orientation, losses in both systems and performance ratio. A PVSyst and SoSiT simulation tools were used to perform simulation analysis of the designed solar photovoltaic WPS. After designing and performance analysis, farmers were interviewed during fieldwork to assess socioeconomic impacts. In the result section, performance of PV system is analyzed at various tilt angles and it is established that system installed at a 15° tilt angle is more efficient. The annual PV array virtual energy at MPP of designed photovoltaic system is 33342 kWh and the annual energy available to operate the WPS is 23502 kWh. Module array mismatch and ohmic wiring losses are 374.16 kWh and 298.83 kWh, respectively. The total annual water demand of the selected site is 80769 m³ and designed SPWPS pumped 75054 m³ of water, supplying 92.93% of the irrigation demand. The normalized values of the effective energy, system losses, collection losses and unused energy in the SPVWP system are 2.6 kW/kWp/day, 0.69 kW/kWp/day, 0.72 kW/kWp/day and 0.48 kW/kWp/day, respectively. The annual average performance ratio of the proposed system is 74.62%. The results of the interviews showed that 70% of farmers are extremely satisfied with the performance of SPVWPS and 84% of farmers indicated that they did not incur any operating costs. The unit cost of the SPWPS is 0.17 €/kWh, which is 56.41% and 19.04% less expensive than the cost of diesel and grid electricity.

Vibration failure in the pumping system is a significant issue for industries that rely on the pump as a critical device which requires regular maintenance. To save energy and money, a new automated system must be developed that can detect anomalies at an early stage. This paper presents a case study of a machine learning (ML)-based computational technique for automatic fault detection in a cascade pumping system based on variable frequency drive (VFD). Since the intensity of the vibrational effect depends on which axis has the most significant effect, a three-axis accelerometer is used to measure it in the pumping system. The emphasis is on determining the vibration effect on different axes. For experiment, various ML algorithms are investigated on collected vibratory data through Matlab software in x, y, z axes and performances of the algorithms are compared based on accuracy rate, prediction speed and training time. Based on the proposed research results, the multiclass support vector machine (MSVM) is found to be the best suitable algorithm compared to other algorithms. It has been demonstrated that ML algorithms can detect faults automatically rather than conventional methods. MSVM is used for the proposed work because it is less complex and produces better results with a limited data set. [ABSTRACT FROM AUTHOR]

In this study, a designed variable frequency drive (VFD) was used to control a single-phase induction motor’s speed to pump guava juice at two solid concentrations (9°Bx and 11°Bx). Next, the pressure drop was measured in stainless-steel pipes of three diameters. The pressure drop percentage difference before and after using the VFD at varied flow rates with 10 repetitions at 5-minute intervals was evaluated. The pressure drop reduction range was 19.7%– 30.8% and 19.2 %–32.4% for the 9% and 11% solid concentrations respectively after using the VFD, which resulted in an average of 25.73% reductions in pressure drop and the pump’s total head and driving power. The rheological properties of guava juice were investigated at various temperatures (5, 15, 25, 35, 55 and 75°C). From the results, all materials exhibited non-Newtonian pseudoplastic behavior at all temperatures and concentrations, and correlated well with the power law model, with flow behavior index (n) values less than unity for the 9% and 11% solid concentrations. The findings offer helpful information for predicting how heat variations during processing influence the behavior of guava juice concentrates.

This article reports the heat transfer data obtained from experimenting a novel functionalized nanodiamond (fND) colloid. In this functionalization technique, the nanodiamonds are coupled with molecules of the host fluid via carboxylic bonds, leading to a de-aggregated and fully stable nanodiamond colloid. The colloid flows through a conduction cold plate where the system cools the electronic component, leading to the resultant heat dissipation. This surface modification on the fully functionalized nanodiamonds ensures ultimate stability of the colloidal suspension of nanodiamond particles. The heat transfer experiments were performed with different concentrations of nanodiamond (0.05, 0.10, and 0.20 wt.%) and under a turbulent flow regime (6,400 < Re < 17,000). The closed-loop heat transfer apparatus utilizes a pump equipped with a variable frequency drive to study the pumping power at various flow rates and fND concentrations. The experimental results of this paper show the remarkable effect of low-concentrated fND additives on enhancing the heat-transfer coefficient of the deionized water. The results show up to a 70% enhancement in the heat transfer coefficient compared to the base fluid at the same pumping power using a 0.20 wt.% fND. The nanodiamond colloid has shown no sedimentation after remaining stored over two years after synthesis. [ABSTRACT FROM AUTHOR]

The traditional circulating cooling water system regulates the flow rate through parallel pumps and valves. Due to fluctuations in operation, there will be lots of energy waste, resulting in inefficient operation of the circulating cooling water system. This research proposed a mixed-integer nonlinear programming (MINLP) method. By installing variable frequency drives (VFDs) on the pumps, changing constant-speed pumps (CSPs) into variable speed pumps (VSPs), we can regulate flow rate with valves and VSPs simultaneously. Optimizing the system using Genetical algorithm (GA) to obtain precise operating parameters, including the configuration of VFDs, the number of CSPs and VSPs and the resistance coefficients of valve in the branch and main pipe. Sensitivity analysis of the model is carried out, and the energy-saving effect of VFD under different temperature differences, pump types and electricity prices, the operating status of the pump and the status of the pipeline are compared. The results indicate that the MINLP genetic algorithm optimization model for industrial circulating water considering variable frequency drive proposed in this paper has a wide range of applicability. It can save an average of 23 % of the total cost under different conditions, and has a promising energy saving effect. • The synergy between pump system and pipeline system are considered. • The precise operation can be obtained in different outer conditions. • The MINLP model can optimize the operation of the existing circulating water system with VSPs. [ABSTRACT FROM AUTHOR]

In modern power systems, interharmonics have emerged as noninteger frequency components that appear in current or voltage signals. Double-stage AC-DC-AC converters have been identified as a primary source of interharmonics. Previous studies have highlighted modulation techniques, filters, passive components, unbalanced conditions and DC link effects as relevant factors. However, the interaction between these factors and the inertial properties of induction motors has not been explored. This study assesses various types of AC drives, including variable frequency drives (VFDs) and soft starters (AC choppers), to investigate their interaction with machine inertial properties in interharmonic generation. The employed technique for time-frequency spectral analysis is the wavelet synchrosqueezed transform combined with a clustering method. This paper demonstrates that the interaction of the inertial properties of low-power induction motors with the variations of the switching frequencies of the VFDs, the filters used in the DC link and a soft start indirectly contribute to harmonic generation and potentially to interharmonics in the electrical grid and the outputs of the inverter.

Variable frequency drive (VFD) is one of the key elements in industrial field. It is used to match the three-phase induction motor's speed and torque to the industrial field process requirements in addition to energy saving and efficiency improvement. This important role of the VFD asks for the development of an efficient training and cost effective platform for the electrical engineering students, technicians, and maintenance personals. This paper introduces a user-friendly platform through which the users can understand and practice the configuration of the various parameters of the VFD unit. This platform uses two computing devices to deal with the VFD; these are the personal computer (PC) and the programmable logic controller (PLC) which is also a computer but designed to operate in wide range of temperature and humidity and can accept digital and analog signals. The PC uses WxPython (cross-platform graphical user interfaces (GUI) toolkit of Python programming language) and PyModbus communication utility to play the role of the human machine interfacing (which allows the user to execute the communication requirements and at the same time provide an oscilloscope like facility to display the platform response in real time mode or history recorded mode). With this platform, the VFD's parameters configuration is done via the RS-485 communication port using Modbus recommandation temporaire d'utilisation (RTU) communication protocol. [ABSTRACT FROM AUTHOR]

In modern electric vehicles, electrical failure has become a critical problem that reduces the lifetime of traction motors. Moreover, traction motors with high-voltage and high-speed systems for a high power density have been aggravating the shaft voltage problems. This study identifies that direct-oil-cooling systems exacerbate this problem. To address this, an analytical method for calculating parasitic capacitance is proposed to determine the effects of cooling oil in a traction motor with a direct-oil-cooling system. Capacitance equivalent circuits are configured based on whether the slot is submerged in the cooling oil. In addition, an electric field decomposition method is applied to analyze the distortion of the electric field by the structure of the conduction parts in the motor. The results indicate that the parasitic capacitances of the traction motor are increased by the influence of the cooling oil resulting in an increase in the shaft voltage. [ABSTRACT FROM AUTHOR]

This paper presents the optimal design of a photovoltaic (PV) drip irrigation system. Designing a PV system is based on calculated motor power, solar irradiance level and other meteorological parameters at a certain geographical location. Therefore, a simulation study of the designed PV system were performed by a PVGIS simulation tool. The PVGIS simulation tool analyzes the potential of power generation with optimal PV modules tilt angle and orientation on a monthly and annual basis, and an analysis of the overall shading situation (horizon) as well as the internal shading between the PV module rows. The selection of water pump and motor depends upon the depth of water table and desired discharge and head to operate the irrigation system. Furthermore, a locally developed Solar-Drip Simulation Tool (SoSiT) was used for load and supply optimization. Based on ambient temperature, solar irradiation and water requirements, SoSiT calculates net generation by a PV system and resultant water output of the irrigation system. The particular drip irrigation site has two zones; the maximum water requirement for zone 1 (row crop) is 50,918.40 Liters/day and for zone 2 (orchards) is 56,908.80 L/day. From PVGIS simulation results, the maximum daily energy production of the designed PV system was 6.48 kWh and monthly energy production was 201 kWh in the month of May. SoSiT results showed that the PV system fulfilled the required crop requirement by only using 28% of the potential water supply, and 72% of the potential water supply from a solar-powered pump was not used. This value is high, and it is recommended to grow more or different crops to utilize the fuel-free electricity from the PV system. The unit cost of PV-powered drip irrigation is USD 0.1013/kWh, which is 4.74% and 66.26% lower than the cost of subsidized electricity and diesel, respectively. [ABSTRACT FROM AUTHOR]

Currently, the most implemented solution for driving a pumping system (PS) at variable speed is using a variable frequency drive (VFD). Because most of the VFDs have integrated only one proportional-integral (PI) frequency controller whose parameters (proportional gain/the integration time) can be off-line tuned but cannot be changed during real-time operation, and many PS must operate in different regimes (at variable speed, variable flow rate, at variable pumping head or even at variable power, e.g., those powered by renewable energy sources), the adaptive control strategy proposed in this paper overcomes these problems with very good performances. The proposed adaptive control strategy uses only simple PI controllers for managing several operating regimes. The adaptive character is not ensured by re-tuning the PI controller parameters as in self-tuning controllers but by readjusting the control law through a change in the control loop depending on the controlled output of the process (pump speed, pump discharge, pumping head or absorbed power). The deviations of the mentioned controlled outputs from their referenced values are converted into electrical frequency error (the deviation of the current value from its reference), which is the regular input to the already tuned controller; therefore, no controller re-tuning is required.

Current work presents salient insights from energy audit of a 1050 MW thermal power plant by BEE Certified Energy Auditors. It provides insights into grassroot level data instead of relying only on theoretical calculations, unlike previously published literature. Arresting the air leakages in air-preheater has given total saving of 10.72 million kWh/year, saved 398,978.97 kJ/year, thus saving of 25,322.80 MT of coal/year. Upgradation of insulation resulted in total saving of 6632.208 Million kJ/year, i.e. saving of 510 MT/year of coal. Replacing cooling tower blades material proposed saving of 15,242.4 kWh/year. Installation of Variable Speed Drives for pumps provided saving of 274,836 kWh/year. Replacement of old inefficient pumps with energy efficient pumps has saving potential of 739,632 kWh/year. Pressure reduction in compressors has given saving of 344,794 kWh/year. Thus, in total, this energy audit helped to conserve 12.098 Million kWh & 25,832.80 MT coal/year and consequently, 104,243 tCO 2 /year. Such savings not only help the plant management/decision makers on the monetary front but also identify the avenues for improvement and channelize the resources such time and investment, prudently. Consequently, it has been established that energy audit is a pragmatic tool to achieve energy conservation at grassroot level. [Display omitted] • Energy audit of coal fired thermal power plant to identify significant energy saving potential with minimum investment. • Novel effort to provide fresh insights into air preheater leakage arrest as substantial energy saving avenue. • Saving of 12, 098, 293.30 kWh electricity/year. • Saving of 25,832.80 MT of coal/year. • Saving of 104,243 tCO 2 /year without hefty investment. [ABSTRACT FROM AUTHOR]

More and more light-emitting diode lighting devices (LED) are being connected to modern power distribution lines. In addition to its many positive features, this poses problems in terms of reactive power compensation. The large number of LEDs interacting with traditional reactive power compensators leads to a harmful phenomenon—overcompensation. This was experimentally determined in the investigated power distribution lines. Along with LEDs, a large number of devices with variable frequency drives (VFD) are connected to the same power distribution lines. This study presents an innovative approach to conventional diode rectifier supply side AC-DC-AC VFDs. It is proposed to use these VFDs as a reactive power compensation device while maintaining their main functions—motor powering and motor speed control. Minor improvements have been proposed to enable these VFDs to provide and draw out reactive power, thereby keeping power factors close to the unit in LED-loaded power distribution lines. The proposed improvements are based on the interaction between the power distribution lines inductivity and the DC circuit capacitance of the VFD. It has been shown that the power factor can be controlled by varying the capacity of the DC circuit. The ability of the AC-DC-AC VFD to compensate for the reactive power provided by the light-emitting diode lighting devices was confirmed by mathematical calculations and experimentally with a laboratory prototype. [ABSTRACT FROM AUTHOR]

Voltage/frequency (V/f) drive of a three-phase induction motor plays a crucial role in a flour mill for energy saving. Wheat consumption in India is increasing day by day, which reached 105,000 metric ton (MT) in 2021. India's high wheat consumption and production increase flour mills. Thus, energy efficiency in a flour mill is a must in the present situation. Hence, V/f drives are widely used in flour mills. Apart from the advantages of V/f drive, electronic circuits in a drive induce harmonics in a power system. Power quality plays a vital role in a modern power system. Harmonics by V/f drive increase the current consumption, causing increased losses, cable overheating, and motor overheating, which necessitates a filter for harmonic mitigation. In this paper, an artificial neural network controller-based hybrid power filter is proposed for harmonic mitigation. A hybrid power filter (HPF) is presented to overcome the problems and achieve the active and passive power filter's benefits. Harmonic mitigation of the proposed hybrid power filter is compared with the passive and active filter-based drives. This paper analyzes harmonic mitigation for three-phase induction motors with V/f drive installed in a 300-ton/day wheat flour mill's purifier fan. The performance of the suggested system is analyzed under various speeds in the aspects of harmonic mitigation, reduction in current consumption, and energy saving using various filters. The entire system is developed and analyzed using MATLAB/Simulink. Energy saving is increased by around 10.97 kWh per year by HPF by means of reducing harmonics and current consumption compared to an active power filter, while it is increased by around 28.16 kWh/year compared to a passive power filter. Along with the harmonic mitigation, energy saving is also validated for various filters under various speeds. [ABSTRACT FROM AUTHOR]

The high frequency PWM voltage pulses from a two-level six-switch inverter produce a common-mode voltage in an electric machine's windings, a fraction of which appears on the machine shaft due to electrostatic (capacitive) coupling. When the shaft voltage exceeds the dielectric strength of the bearing lubricating grease, electric discharge machining (EDM) electrostatic discharges occur within the bearing, which can lead to premature failure. According to pulsed dielectric theory, the breakdown voltage across a dielectric increases with an increase in voltage slew rate (dv/dt). Therefore, the faster voltage rise times of wide bandgap devices are expected to produce higher magnitude shaft voltages and EDM bearing currents. This paper presents circuit modeling of EDM currents and compares the shaft voltage and bearing current amplitudes of silicon- and silicon carbide-based PWM inverters through experimental measurements and a statistical analysis using probability density functions. The statistical analysis provides insights regarding the correlation between bearing failure and the number of damage causing discharges over time which is a key step in developing bearing lifetime prediction models. [ABSTRACT FROM AUTHOR]

In this study, a designed variable frequency drive (VFD) was used to control a single-phase induction motor’s speed to pump guava juice at two solid concentrations (9°Bx and 11°Bx). Next, the pressure drop was measured in stainless-steel pipes of three diameters. The pressure drop percentage difference before and after using the VFD at varied flow rates with 10 repetitions at 5 min intervals was evaluated. The pressure drop reduction range was 19.7%– 30.8% and 19.2 %–32.4% for the 9% and 11% solid concentrations respectively after using the VFD, which resulted in an average of 25.73% reductions in pressure drop and pump’s total head and driving power. The rheological properties of guava juice were investigated at various temperatures (5, 15, 25, 35, 55 and 75°C). From the results, all materials exhibited non-Newtonian pseudoplastic behavior at all temperatures and concentrations, and correlated well with the power law model, with flow behavior index (n) values less than unity for the 9% and 11% solid concentrations. The findings offer helpful information for predicting how heat variations during processing influence the behavior of guava juice concentrates. [ABSTRACT FROM AUTHOR]

In this study, an innovative approach to matrix-converter-based AC-–AC variable frequency drives (VFDs) is introduced. The possibility of using AC–AC matrix VFDs for reactive power compensation in conventional AC–DC–AC VFD-loaded power distribution lines is investigated. It is found that the interaction of a large number of conventional AC–DC–AC VFDs with a conventional capacitor-based local compensation device leads to overcompensation in 0.4 kV power distribution lines. This is due to the fact that the conventional compensation device is designed to compensate the lagging reactive power produced by inductive loads, such as AC motors. This highlights the demand for the compensation of leading reactive power that is not predicted by the designer. To solve this problem, the modification of a certain number of previously installed VFDs by replacing their conventional AC–DC–AC converters with AC–AC matrix converters is proposed. This can lead to improvements in the power factor in 0.4 kV power distribution lines. In this study, the range of reactive power produced by conventional AC–DC–AC VFDs was determined mathematically, by simulation, and experimentally. The range of reactive power produced by the novel AC–AC matrix VFD was also determined. On that basis, the number of VFDs to be modified is defined to keep the power factor close to unity. [ABSTRACT FROM AUTHOR]

In this paper, a novel fault diagnosis method for variable frequency drive (VFD)-fed induction motors is proposed using Wavelet Packet Decomposition (WPD) and greedy-gradient max-cut (GGMC) learning algorithm. The proposed method is developed using experimental stator current data in the lab for two 0.25 HP induction motors fed by a VFD, subjected to healthy and faulty cases under various operating frequencies and motor loadings. The features are extracted from stator current signals using WPD by evaluating energy eigenvalues and feature coefficients at decomposition levels. The proposed method is validated by comparing with other graph-based semi-supervised learning (GSSL) algorithms, local and global consistency (LGC) and Gaussian field and harmonic function (GFHF). To enable fault diagnosis for untested motor operating conditions, mathematical equations to calculate features for untested cases are developed through surface fitting using features extracted from tested cases.

Accurate load modeling is critical for credible power system stability analysis. Because of the increasing complexity in modern system load, establishing a more comprehensive load model and performing accurate parameter estimation are the two biggest challenges in composite load modeling. In this paper, an induction motor with variable frequency drive (IM-VFD) together with the traditional ZIP+IM model is utilized to describe the dynamic characteristics of the system load. We estimate the time-varying probabilistic distributions of all states and parameters to describe their stochastic characteristics, thereby representing the real-time varying features of an actual load. The Fokker-Planck operator is applied to linearize the updated load model in tensor format. We then use tensor decomposition to reduce the computational and storage costs for calculating load model parameters. A sensitivity indicator is used to analyze the sensitivities of the estimated parameter distributions for subsequent model reduction. Simulations demonstrate that the updated load model has better performance than the traditional ZIP+IM model. [ABSTRACT FROM AUTHOR]

This paper presents a dual-motor drive system with a three-phase two-level inverter for independent speed control of a three-phase motor and a single-phase motor. The single-phase motor is connected in series between the neutral point of the three-phase motor and the midpoint of two split DC-link capacitors. As the single-phase motor current is a zero-sequence component flowing in the three-phase motor, it does not affect the operation of the three-phase motor. The proposed drive system can reduce the number of power switches compared with the conventional drive system that uses a single-phase and a three-phase inverter. Thus, the proposed system can reduce the cost of the drive system. Simulations and experiments are presented to verify the proposed drive system. [ABSTRACT FROM AUTHOR]

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The torsional vibration problem of shaft in an induced draft fan (IDF) caused by frequency conversion driving technology is a result of dynamic electro-mechanical coupling behavior during the energy conversion. Therefore, it is difficult to understand the mechanism of torsional vibration by only analyzing the mechanical structure or the electrical structure. In this paper, eigenvalue structural analysis (ESA) and time-domain transient analysis, which are typically used to examine sub-synchronous resonance (SSR), are employed to resolve this issue. It is difficult to develop a linear model for complex controllers with ESA as ESA can cause certain errors during the linearization and estimation of initial values of equilibrium points. On the contrary, time-domain analysis not only offers a small-step integration technique to simulate a realistic condition but also facilitates transient analysis of complex controllers. Transient analysis has been used to study the influence of elastic parameters of shaft, self-damping coefficients, resistance of the stator side, smooth reactance of the stator side, and voltage-frequency ratio on the control of target frequency converters and cascade multilevel high-voltage frequency converters. In this paper,It is also advised to avoid torsional resonance region with torsional-vibration monitoring during the operation of the system, and stator resistance can be added and the voltage-frequency rate can be adjusted to obtain an integrated control of an active torsional-vibration system.

This paper presents a quantitative prediction model of conducted electromagnetic emissions (EME) for a variable frequency drive (VFD) motor system based on the macro-modeling approach. This model relies on the effective representations of the frequency dependent characteristics of the parasitic behaviors between converter arms and heatsink, of shielded power cable, and of motor windings. The frequency dependent performances between converter arms and heatsink, and of the motor windings are obtained by processing measurement data. Then the vector fitting method (VFM) with passivity enforcement and circuit synthesis method are adopted to obtain the corresponding equivalent circuits. The equivalent circuit implementation of shielded power cable is achieved by applying a node-to-node admittance functions (NAFs) model, which considers the propagation phenomenon and frequency dependent losses accurately. The conducted EME model is compatible with commonly used transient circuit solvers since it only includes constant circuit elements. The conducted emissions of the VFD system are then evaluated by analyzing the common mode (CM) and differential mode (DM) voltages and currents. [ABSTRACT FROM AUTHOR]

The modular multilevel converter (MMC) is considered to be emerging multilevel topology for medium to high power applications due to its modularity and highly reliable structure. However, large submodule (SM) capacitor voltage ripple and higher circulating current during variable frequency operation is the major drawback of the MMC. In the literature, higher-order harmonic elimination technique is presented to reduce SM capacitor voltage ripple and circulating current. In this article, effect of lower-order harmonics on circulating current is investigated. The effect of second-order fundamental frequency current harmonic I2f on arm inductor is analyzed. Based on detailed analysis, an optimal design method for selection of arm inductor is proposed. Proposed optimal design is capable of reducing the circulating current under variable frequency range as well as SM capacitor voltage ripple remains under specified limit during entire variable frequency operation. A detailed MATLAB model of MMC fed high power medium voltage drive is developed. Experimental setup is also developed to check the effectiveness of proposed optimal design method. Reduction in circulating current and control of SM capacitor voltage ripple is observed for entire range of frequency. [ABSTRACT FROM AUTHOR]

• Design a stand-alone SPV-powered variable frequency drive (VFD) for water irrigation using bubblers. • The VFD that control water pumping system was based on the direct drive during the daytime without battery backup. • The performance of the developed system was evaluated, and their costs were analyzed. • Uniformity of water distribution by bubblers and soil moisture at different depths in the root zoon was investigated. • Automated irrigation system using SPV provides a sustainable solution to enhance water use efficiency and energy crises. This work aims to design a standalone solar photovoltaic (SPV) system to operate variable frequency drive (VFD) for palm trees irrigation using bubblers and control the irrigation network. A complete irrigation system is designed and constructed in two fields of date palm trees. A small photovoltaic (PV) system is used to operate the rainbird controller which changed water delivery from one subline to another after a predetermined time. The performance of the developed system is evaluated under different operating factors and its costs are analyzed. Water distribution uniformity and soil moisture at different depths in the root zoon are measured. The frequency of supply voltage is influential in controlling the speed of the induction motor, whereby operating the inverter, the motor speed is constant without any oscillation. Irrigation through the last two laterals in field II indicated that the required maximum hydraulic energy and maximum PV array power was 7.81 kW h/d and 3.74 kWp, respectively at the total dynamic head of 22.75 m. The coefficient of variation of bubblers flow was a small value for a single lateral (3.83 %), while for two laterals it varied from 8 to 12 %. The total dynamic head reached about 22.75 m for the last sublines in field II. The average subsystem efficiency was about 0.41. The annual cost of unit power of PV system was 0.161 $US /kWh without subsidies. The proposed SPV pumping is cost-effective and controlled the motor efficiently without energy backup. [ABSTRACT FROM AUTHOR]

The purpose of the article is to study the possibility and feasibility of participation of nuclear power plants (NPPs) with VVER in emergency frequency control in power systems with a high proportion of nuclear power units and, at the same time, of reducing the power consumption for the own needs of the main circulation pumps during modes with power below nominal. To solve these problems, it was proposed to increase the achievable speeds of power gain (load increase) due to the installation of frequency controlled drives of the MCP. Large system frequency variations (caused by large imbalances between generation and demand) may jeopardize electrical equipment, in terms of maintaining stable and reliable operating conditions. For NPPs, the task of preventing or localizing accidents is even more important than for TPPs, since in case of major system accidents, it is possible to completely stop external power supply of the NPPs own needs. Thus, besides the requirements for the primary control of the frequency of NPPs with VVER, today we need more stringent requirements for their emergency acceleration and mobility. The operation of NPPs with long-term non-recoverable active power shortage causes a decrease in the speed of the main circulation pumps of NPPs with VVER and a decrease in the coolant flow rate. It is shown that the installation of variable frequency drives of the MCPs at NPP with VVER is appropriate not only to save energy consumption for their drive in partial modes, but also to increase the power of NPP above the nominal (without reducing the reserve before the heat exchange crisis in the reactor core) for the elimination of system accidents, and thus to improve the safety of the NPPs included in the power system.

Abstract: The coordinated generation and load control to increase transient stability level of oil- production enterprise autonomous power system with dominant motor load is studied in the paper. Mutual angle between voltage phasors at gas turbine plant bus and equivalent load node as well as slip difference of synchronous machines are used as input signals. It is shown that implementation of additional control allows to increase the level of transient stability by more than 40%. The combined coordination of power system stabilizer of synchronous generators and motors as well as gas turbine frequency control parameters is applied. The positive impact of power system stabilizer settings on post-accident conditions is proved by analysis of small signal stability.

A closed-loop control simulation model of variable frequency drive hydraulic winch system was built using AMESim, and the dynamic characteristics of the hydraulic winch system under different load mutations were simulated and analyzed using the model. The simulation results show that the variable frequency drive hydraulic winch system can realize accurate control of drum speed. In the process of no-load and on-load start-up, the lifting speed of the drum can reach the target speed after short-term fluctuation, and the final deviation between the actual displacement of the drum and the target displacement in two cases is not more than 0.1 m. Under the start-up with load, the variable frequency drive hydraulic winch system has good response and tracking characteristics to speed step and sinusoidal changes, and the drum speed of winch is insensitive to the change of load, and the speed stability with load is good.