Variable Frequency Drive Research Articles

Optimization of Steam Boiler Airflow Control System in a Typical Oil Refinery Power Plant

This paper presents optimization of Steam Boiler Airflow Control System in a Typical Oil Refinery Power Plant. The power plant is equipped with four steam boilers using a damper-louvers airflow control system. Analysis has revealed significant energy wastage due to inefficiency and over-air supply, with the system requiring 59,904,436 kWh annually at a financial cost of N1, 093,255,884. The existing system's inefficiency results in an annual electrical energy waste of 8,502,302 kWh. This inefficiency is attributed to the Force Draft Fan (FDF) motor operating at maximum speed continuously, regardless of the steam profile or airflow requirements. This study aimed at optimizing the steam boiler airflow control system in a typical oil refinery power plant for improved power efficiency, energy conservation, and cost savings citing Port Harcourt Refinery Company (PHRC) at Alesa-Eleme, Rivers State, Nigeria. To address this, the damper-louvers system was replaced with a Variable Frequency Drive (VFD), which would adjust the motor speed to match the required airflow, thereby reducing energy wastage. The process was simulated and VFD/FDF motor analyzed in MATLAB Simulink, determining the optimal speed, airflow, and power requirements. Results obtained show that the VFD control system improves the FDF motor's power efficiency from 47.7% to 85%, with an annual energy saving of 8,502,302 kWh (8.5 GWh). This results in a total cost benefit of N478.18 million annually, representing a 43.8% cost saving. The implementation cost of the VFD infrastructure was estimated at N111, 440,000, with a payback period of approximately eleven months. The findings suggest deployment of higher FDF motor speed ratings to enhance speed control and energy efficiency in Oil refinery power plant.

Start-Up and Steady-State Regimes Automatic Separation in Induction Motors by Means of Short-Time Statistics

Induction motors are widely used machines in a variety of applications as primary components for generating rotary motion. This is mainly due to their high efficiency, robustness, and ease of control. Despite their high robustness, these machines can experience failures throughout their lifespan due to various mechanical, electrical, and environmental factors. To prevent irreversible failures and all the implications and costs associated with breakdowns, various methodologies have been developed over the years. Many of these methodologies have focused on analyzing various physical quantities, either during start-up transients or during steady-state operations. This involves the use of specific techniques depending on the focus of the methodology (start-up transients or steady-state) to obtain optimal results. In this regard, it is of great importance to develop methods capable of separating and detecting the start-up transient of the motor from the steady state. This will enable the development of automatic diagnostic methodologies focused on the specific operating state of the motor. This paper proposes a methodology for the automatic detection of start-up transients in induction motors by using magnetic stray flux signals and processing by means of statistical indicators in time-sliding windows, the calculation of variances with a proposed method, and obtaining optimal values for the design parameters by using a Particle Swarm Optimization (PSO). The results obtained demonstrate the effectiveness of the proposed method for the start-up and steady-state regimes automatic separation, which is validated on a 0.746 kW induction motor supplied by a variable frequency drive (VFD).

Fault Detection Techniques for Variable Frequency Drives and its Structured Components

Abstract: Variable Frequency Drives (VFDs) are essential instruments in modern industrial systems, providing precise control over motor speed in various industrial applications and improving energy efficiency. Faults in VFD’s can lead to costly downtime and reduced productivity. This paper presents precise fault detection technique for VFDs and its technical components providing flawless step by step method for quick access of faulty parts / items and time saving in testing methods. Experimental results demonstrate the effectiveness of the proposed approach in accurately detecting faults in IGBT, SCR, choke, capacitor, power card, control card, firing card, CT card and its causes like temperature over voltage and current, aging, atmosphere and bearing wear etc. The proposed methodology offers Cold test and hot test methods applied on common technical machines using oscilloscope and multi-meter.

Auditing and Analysis of Natural Gas Consumptions in Small- and Medium-Sized Industrial Facilities in the Greater Toronto Area for Energy Conservation Opportunities

This paper presents the findings of fifteen energy audits conducted on industrial sites in Canada’s Greater Toronto Area (GTA). The audits covered a range of industries including food processing, packaged goods, and finishing processes (powder-coating). The primary focus of the audits was to analyze the natural gas consumption and the performance of major-gas-consuming equipment. The audits identified natural-gas-consuming equipment that could be optimized to yield energy and operational cost savings and greenhouse gas (GHG) reduction opportunities. Food production plants’ energy intensity ranges from 5.59 m3/ft2 to 17.73 m3/ft2. Therefore, there is a significant opportunity to improve energy consumption through better technology integration. The results of the audits indicate a trend of an increase in the percentage of non-productive consumption with non-productive time. The proposed energy-saving measures include reducing non-productive natural gas consumption, gas-fired equipment tune-up, optimizing boiler loads, and reducing oven exhaust by using variable frequency drives (VFDs). The findings of this study could be used to develop a demand-side management program specifically for small- and medium-sized industrial facilities in the Greater Toronto Area and other parts of Canada.

Assessing the efficiency of measures to enhance electric power quality in variable-frequency drive for scraper conveyors

The intensive implementation of variable-frequency drive machines and installations in underground mining processes necessitates addressing several issues, with a primary focus on ensuring the quality of electric power. Elevating the energy resource of mining machines and enhancing the energy efficiency of mining operations requires maintaining the rated indicators of electric power quality in mine power distribution systems. Achieving this involves assessing the level and composition of higher harmonic components in voltage and current within power circuits equipped with variable-frequency drives (VFD). Key objectives encompass the development of a simulation model based on the equivalent diagram of the power distribution system substitution with a scraper conveyor VFD to scrutinize the spectral composition of higher harmonic components in the power circuits of the mine power distribution system (MPDS). Additionally, the study involves analyzing the impact of harmonic filters (HFs), reactors, and sine filters on the quality of electric power in the VFD system of a scraper conveyor. Further analysis extends to the spectral composition of higher harmonic components in circuits related to insulation leakage and metering circuits of the residual-current device. Practical recommendations for improving electric power quality in the VFD system of a scraper conveyor are then developed based on the research findings. The established model of a variable-frequency drive system for scraper conveyors facilitates the assessment of the effectiveness of electric power quality improvement measures. The harmonic composition of voltage and current in the mine power distribution system is determined under maximum distortion conditions and in the presence of HFs, reactors, and sine filters. Research methods are chosen to unveil the spectral composition of voltage and current in symmetrical and single-phase modes of insulation leakage, as well as in metering circuits of residual-current devices (RCDs). It is noted that the harmonic composition of leakage voltage and current is primarily influenced by the parameters of the output voltage modulated by the autonomous frequency converter inverter. Considering the high level of harmonic components in voltage and current, adjustments to RCD settings, capacitive current compensator, and the protective shunting unit are recommended for electrical safety. The study emphasizes the importance of scientifically substantiating the rated indicators of higher harmonic components for leakage circuits and further exploring the physiological effects of higher current harmonics on the human body. The feasibility of installing a harmonic filter (HF) directly on the low-voltage supply section of a scraper conveyor should be technically justified. Interestingly, the presence of HFs, reactors, and sine filters does not significantly impact the harmonic composition or the magnitudes of coefficients of the harmonic components in the phase voltage of the system concerning ground and leakage currents through insulation. However, higher harmonic components induced in leakage current circuits may pose a potential hazard, leading to a violation of magnetic compatibility and posing risks in case of contact with live parts of electrical equipment.

The use of a front-end ZVZCS DC-DC converter for an IoT VFD inverter system in the paddle wheel machine drive applications

This research paper proposes the integration of power electronics and internet of things (IoT) technologies to apply in shrimp farms. By focusing on the design of a front-end converter, a three-level half-bridge (3L-HB) DC-DC converter with the zero voltage and zero current switching (ZVZCS) technique is chosen to be the front-end power converter to supply the DC bus voltage for the variable frequency drive (VFD) inverter for the paddle wheel machine in the shrimp pond. To confirm the effectiveness and possibility of the proposed concept, the circuit was theoretically designed and tested at 540 V DC of the input voltage, 700 V DC of the DC bus voltage and 3 kW of rated power. It is found that, the front-end converter can step up the DC bus to be 700 V DC which is enough for operating the VFD inverter. All switches can achieve the soft switching condition ZVZCS resulting in decreasing the switching loss and increasing the reliability of the circuit. The maximum experimental efficiency of the front-end converter is 94.9% at 75% of a full load. In addition, the introductory concept of using the IoT system also presents to improve the shrimp farming method.

Development MPC for the Grinding Process in SAG Mills Using DEM Investigations on Liner Wear.

The rapidly developing mining industry poses the urgent problem of increasing the energy efficiency of the operation of basic equipment, such as semi-autogenous grinding (SAG) mills. For this purpose, a large number of studies have been carried out on the establishment of optimal operating parameters of the mill, the development of the design of lifters, the rational selection of their materials, etc. However, the dependence of operating parameters on the properties of the ore, the design of the linings and the wear of lifters has not been sufficiently studied. This work analyzes the process of grinding rock in SAG mill and the wear of lifters. The discrete element method (DEM) was used to simulate the grinding of apatite-nepheline ore in a mill using different types of linings and determining the process parameters. It was found that the liners operating in cascade mode were subjected to impact-abrasive wear, while the liners with the cascade mode of operation were subjected predominantly to abrasive wear. At the same time, the results showed an average 40-50% reduction in linear wear. On the basis of modelling results, the service life of lifters was calculated. It is concluded that the Archard model makes it possible to reproduce with sufficient accuracy the wear processes occurring in the mills, taking into account the physical and mechanical properties of the specified materials. The control system design for the grinding process for SAG mills with the use of modern variable frequency drives (VFD) was developed. With the use of the proposed approach, the model predictive control (MPC) was developed to provide recommendations for controlling the optimum speed of the mill drum rotation.

CONTROL OF A HEAT PUMP COMPRESSOR WITH VARIABLE FREQUENCY DEVICE DRIVEN BY PID

Integrating advanced control technologies to enhance energy efficiency and environmental sustainability in heat pump systems is of growing significance. This article offers a comprehensive review on the utilization of Proportional-Integral-Derivative (PID) control and Variable Frequency Drive (VFD) technology to govern the compressor's operation in a heat pump. The primary objective is to optimize energy consumption and thermal output under varying loads and environmental conditions, thus enhancing the heat pump's performance.
 
 The article delves into the fundamental principles of heat pump operations, emphasizing the compressor's pivotal role in maintaining the delicate balance between energy consumption and desired thermal output across applications, spanning residential HVAC to industrial processes. The PID control algorithm is introduced to adapt the compressor's speed and power consumption dynamically. The VFD is incorporated into the control system, enabling variable speed compressor operation for a responsive reaction to load fluctuations. Combining PID and VFD control is explored to achieve peak system performance and energy efficiency.
 
 Through practical experiments and simulations, the research investigates the influence of PID and VFD control on energy efficiency, stability, and performance. The results underscore substantial energy savings and environmental impact reduction potential, particularly in scenarios with variable thermal loads and fluctuating environmental conditions.
 
 This study advances our understanding of advanced control strategies in heat pump technology and underscores the pivotal role PID and VFD control play in creating energy-efficient heating and cooling solutions. The findings offer practical implications for diverse applications, from residential settings to industrial processes, and provide insights into sustainable heat pump technology use in the context of energy conservation and climate change challenges.

Harmonic Penetration Analyses for DC-Link Frequency Converter Drive Systems by Considering the Motor-Side Converter as an Ideal Current Generator

Nowadays increasing attention turns to the harmonic penetration analysis of the alternating voltage network connected devices operating with pulse width modulation (PWM). The PWM operation causes high frequency current injection to the grid (at the frequency range: 1kHz to 100kHz, depending on the power and the structure of the device). However, devices are now rolling out, that are infected by these current components, for example: power line communication (PLC) devices, smart metering devices, etc. It is very difficult to analyse such high frequency harmonic components with measurements. Therefore, the simulation analyses of the PWM devices harmonic penetration are revalued. These are cost efficient and fast. This article is dealing with the harmonic penetration analyses of alternating voltage network connected DC-link frequency converters equipped with active rectifier. In our study we were focusing on the variable frequency drive (VFD) of squirrel cage induction motors (SCIM). Simulation models of the motor and a DC-link frequency converter were built in time domain. The main purpose of this paper is, to study whether the effect of the motor-side converter of the VFD and the motor can be neglected for the harmonic penetration analyses of the DC-link frequency converter.

Energy Reductions in the Pulp-and-Paper Industry by Upgrading Conventional Pumping Systems through the Installation of VFDs – A Case Study

In this paper we intend to demonstrate the benefits that can be obtained by upgrading conventional pumping systems, i.e, without speed control, pervasive in the older project Pulp-and-Paper industries, through the installation of Variable Frequency Drives (VFDs). The main objective is to significantly reduce the energy consumption and associated cost, while simultaneously avoiding the production of excess Greenhouse Gases (GHGs), contributing to the global sustainability efforts. A case study is presented, where a conventional level control system, based on an automatic valve and a constant speed driven pump, is converted to a control strategy based on the combined actuation on the valve and on the speed of the pump. For this study, it is shown that a yearly energy reduction of about 60% is achieved. This reduction, associated with a 160 kW motor, results in a yearly energy reduction of about 533 MWh and an associated reduction of about 250 tonnes CO2 . Negative effects in the power quality such as harmonics and common-mode currents must be considered, but could be kept under acceptable limits. With the results presented in this work, fully developed in an actual industrial environment, we aim to motivate those in the industry to pursue similar objectives.

Reduction of energy consumption using remote Variable Frequency Drive (VFD)

The use of technology in irrigation is a parameter to be considered when there is a need for energy savings and greater process control. In several situations, it is necessary to adjust the characteristics of the hydraulic system during operation of the motor shaft in the irrigation system. The use of a Variable Frequency Driver (VFD) changes the frequency of the motor pump to allow the rotation of the motor shaft to suit the needs of the hydraulic system. With a change in the amount of water in the catchment tank, it becomes necessary to adjust the rotation of the motor shaft to a new head. The objective of this study was to develop a system capable of allowing remote control of a Variable Frequency Drive that controls a motor pump that feeds the central pivot. The system was developed from a microcomputer board Raspberry model and an Arduino microcontroller board controlling a potentiometer of 200k and it was observed that three motor-pump-inverter assemblies presented differences in the significance level between the data of the system and the obtained data. The data showed a strong positive correlation. This system can be an alternative when it is not possible to change the inverter parameters in the field.

The Impact of Power Quality on VFD Application in Motor Fan Dust Collector

The technology to control the motor speed according to load requirements is variable frequency drive (VFD). The motor fan dust collector operates using a VFD to reduce the speed during idle smelting conditions. In addition to energy efficiency, the power quality of the electrical energy system is important to consider. Nonlinear loads from VFDs cause harmonics in the industry that affect electrical power. Power quality measurement and analysis to determine the harmonic and unbalance values of voltage and current are important for improving power quality. This paper discusses the effect of VFDs on power quality, as a real case study, data from existing VFDs in the steel industry are taken to analyze power quality. A large current harmonic of 45% occurs when the VFD decrease the motor speed during idle smelting operation and drops to 5% when the motor speed returns to full speed during smelting operation on. The average maximum current unbalance value is 10.8% and the voltage unbalance is 0.36%, which is still below the standard maximum limit whether the motor is at full or low speed.

Flow Rate and Volume Estimates from Variable Frequency Drive Operated Drainage Sump Pumps

Highlights This article provides an overview of operations and benefits of using a variable frequency drive to operate agricultural subsurface drainage system sump pumps. A methodology is proposed to monitor flow rates leaving agricultural subsurface drainage pump stations via a MATLAB algorithm. The results of this research were mixed because the algorithm estimates did not always match with the corresponding flowmeter measurements. Abstract. 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. Keywords: Edge-of-field monitoring, Flow rate, Pump, Red River Basin, Subsurface drainage, Variable frequency drive

Introducing Analysis of Experiments in Electrical Machines Laboratory

Abstract— The scope of the Conceive, Design, Implement, and Operate (CDIO) framework is to help the learner attain higher-order thinking skills (HOTS) in their courses. But most of the theory and practical courses offered in academic institutions are of a low-order thinking level. In outcome-based teaching and learning (OBTL), in order to achieve the graduate attribute of critical thinking, the learner needs to design and do the experiment and also be able to analyze and provide inferences about the data. Most laboratory courses offered in engineering colleges have an application level. To improve the course outcome from apply to analyze level, integrating a component of experiment analysis is required in the laboratory courses, which helps the students achieve higher-order thinking skills. An electrical laboratory course is given to the second semester students with the conventional experiments of machines at the application level. In order to inculcate analyzing skills, a case study of introducing a simple statistical analyzing tool based on MS-Excel in an experiment called ‘load test on a 3-phase induction motor using variable frequency drive (VFD)’ is presented in this paper. It was found from the laboratory assessment that the students using this analysis and visualization tool for interpreting the results scored well compared to the previous year's students. Keywords— Higher order thinking skills (HOTS); outcome based teaching and learning (OBTL); variable frequency Drive (VFD); ANOVA.

ПРОГРАММНЫЙ КОМПЛЕКС ДЛЯ РЕАЛИЗАЦИИ АСИНХРОННОГО ЧАСТОТНОГО ПУСКА ВЫСОКОВОЛЬТНЫХ ДВИГАТЕЛЕЙ И СНИЖЕНИЯ ВРЕМЕНИ ПЕРЕРЫВА В РАБОТЕ ДВИГАТЕЛЯ ПРИ КРАТКОВРЕМЕННОЙ ПОТЕРЕ ПИТАНИЯ

Relevance Most of the electricity consumed comes from electric drives (ED) of various technological processes. The most common way to increase the efficiency of an electric drive is the use of a variable frequency drive (VFD). However, the use of VFDs in some cases causes a decrease in the operating efficiency of the electric drive, this is due to the high sensitivity of the frequency converter to network voltage dips, leading to the failure of the inverter and to the stop of the technological process. A current direction is the development of algorithmic methods for increasing the stability of electric drives. Aim of research Increasing the stability of a frequency-controlled motor during emergency conditions in the power supply system. Development of a power supply circuit for an electric drive, and research into the algorithm for operating the inverter in emergency modes. Methods The study of the developed method was carried out in the Matlab Simulink software package. Results A power supply circuit for an electric drive with a synchronized bypass line and a main line with a frequency converter operating according to the developed algorithm is proposed. A study of the influence of the error in measuring the shaft rotation speed on the accuracy of maintaining the recuperation of the DC transformer, as one of the ways to increase the resistance of the VFD to short-term voltage dips in the network was carried out.

Evaluation of the operation of the fan of the combine harvester air-and-screen cleaning system when using an asynchronous electric motor as a drive

The article presents the results of a study of a combine harvester fan after making design changes aimed at facilitating air flow control in airand-screen cleaning. To this effect, the mechanical drive of the combine harvester fan was replaced with an electric one having an automated control system based on variable-frequency drive (VFD).

Adapted Irrigation Pump Load in Solar PV and Wind Energy Systems through Stepped Variable Frequency Drives

Wind and solar photovoltaic (solar-PV) power are highly variable and intermittent as exhibited by corresponding generation profiles. When this power is utilized directly for water pumping, the availability and reliability of water automatically follow the Renewable Energy Sources (RES) characteristics. On the other hand, Deferrable Irrigation Load (DIL), follows a specific irrigation water need profile. The DIL profile is determined by crop cycles and corresponding water needs. It is also affected by aspects of weather mainly precipitation, temperature, and wind. In this research, discrete switches and Variable Frequency Drives (VFDs) are applied as a combined solution. Combined discrete and continuous switching through VFDs is applied to separately adapt pump load to DIL and RES profiles. Discrete switches are applied to engage the exact number of pumps required to match an expected irrigation load. A VFD is further used to ensure continuous matching of irrigation pump load to the anticipated DIL curve, through adjustment of pump speed points. Finally, the system is repeated to adapt the pump power to the RES curve. The adapting technique was implemented to improve elasticity, hence the efficiency of the system. The results showed that the adapted system to the DIL curve was 94.7% compared with a discrete-only system (91.4%). This represented a slight improvement of 3.3%. 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 94.7%.

A comprehensive analysis of the energy, economic, and environmental impacts of industrial variable frequency drives

Motor systems are ubiquitous throughout the industrial sector, particularly in fluids applications. It is well known that the efficiency of these operations can be greatly enhanced using variable frequency drive (VFD) controls, but adoption of the technology is far from universal. The goal of this paper is to introduce engineering, economic, and environmental analyses to demonstrate benefits to both individual facilities and the state at large. Individual case studies are presented to describe the variety of opportunities for VFD-enhanced motor control; however, this project seeks to describe the combined impact of VFD implementation at a new scale. Data sourced from a U.S. Department of Energy program is used to perform economic and environmental input output analysis to calculate broad impacts of individual audits and recommendations. Results indicate that widespread implementation of VFD controls on motor systems in the industrial sector will introduce significant economic and environmental benefits. One of the scenarios showed a potential reduction of over 4.7 million tonnes of carbon dioxide from regional manufacturing sector as well as a cascading contribution to the regional economy totaling nearly $1 billion. The results are presented as a demonstration of the magnitude of impact that improving control of industrial motor systems can have, as a guide to industry leaders and policymakers about the value of such investments.

Close accord on partial discharge diagnosis during voltage harmonics in electric motors fed by variable frequency drives

AbstractPartial discharge (PD) diagnostics test is a reliable solution for estimating insulation health conditions in power system components. During laboratory PD diagnostics, the effect of harmonic components in the voltage waveform generated by variable frequency drives (VFD) fed electric motors (EMs) is often overlooked. As VFD‐fed EMs operate at low speeds, the harmonic concentration in the voltage increases. It has been found that PD activity in VFD‐fed EM is significantly affected by the addition of harmonic components in the voltage, thus making it necessary to consider their impact when performing true PD diagnostics. This paper investigates the influence of voltage harmonic distortion produced in VFD‐fed EM on PD severity and the subsequent insulation degradation. Eight VFD‐fed EM are used to study the PD behaviour under different levels of harmonic pollution. The PD characteristics, such as inception voltage, pulse repetition rate, accumulated apparent charge, average discharge current, discharge power, and quadratic rate, are determined. Using probability distribution functions, PD activity and severity at various voltage harmonic levels are estimated. The proposed technique can be used to plan the maintenance activities that ensure the reliability for industrial applications dealing with the voltage harmonic distortion.

Energy efficiency investment in Swiss industry: Analysis of target agreements

Slowing down the energy efficiency (EE) improvement rate over the past half a decade and relatively low EE-related investments highlight a need for a more targeted approach to encourage EE improvement investment in the Swiss manufacturing sector. The current work is based on an analysis of already implemented energy efficiency measures (EEMs) via target agreements. Four segments of the Swiss manufacturing sector are identified using the K-means clustering based on the energy consumption profiles of the establishments. The EEMs are categorized through text analysis with the help of a machine learning algorithm. The EEMs are ranked using two indicators that can inform different stakeholders: i) EEMs with Internal rates of return well above the reported risk-adjusted hurdle rates are identified for each segment to help industrial decision-makers take ad-hoc, profit-based investment decisions on EE improvement. ii) Levelized costs of saved energy are presented as value ranges for the EEMs that have the largest impact on annual total final energy (TFE) reduction for each segment to help policymakers design a more targeted approach for the promotion of high-impact EEMs. EE system improvements such as insulation of steam systems and process optimization, as well as EE equipment improvements like process equipment insulation, installation of variable frequency drives (VFDs), smart controls, and IE3 motors, were found to be the most profitable options across all clusters. For the electricity cluster, CHP was found to be the most impactful way of EE improvement (high energy savings) but not cost-effective. For fuel-consuming clusters, waste heat recovery measures were found to be the most cost-effective and among the most impactful options for EE improvement, along with fuel substitution measures with varying degrees of cost-effectiveness.