Showing papers on "Variable-frequency drive published in 2019"

High-Accuracy Capacitance Monitoring of DC-Link Capacitor in VSI Systems by LC Resonance

Abstract: Monitoring the condition of a dc-link capacitor is important for the reliability-critical voltage source inverter (VSI) systems. With the ever increasing application of a metalized poly propylene film (MPPF) capacitor, a new challenge for dc-link capacitor condition monitoring (CM) is presented due to the very small equivalent series resistance and capacitance end-of-life criterion (typically 2%–5%) of an MPPF capacitor. To improve the accuracy of capacitance estimation, a novel quasi-online CM method is proposed in this paper, which introduces an LC resonance intentionally when system is not in operation. Experimental work is carried out to validate the method and the results show that 1% capacitance estimation accuracy can be achieved in a 3-kW induction machine variable frequency drive system. Because of the signal measurement at large amplitude (e.g., nominal current) and the time-based multi-parameters identification algorithm, the method is accurate and inherently insensitive to the system parameters variation, measurement noise, and effect of temperature drift. In practice, the method can be implemented using the system available sensors with no need of hardware modification. Moreover, since the resonance current is limited and decays shortly, the condition of a dc-link capacitor can be monitored safely and frequently on-site in a VSI system.

A Twelve Concentric Multilevel Twenty-Four Sided Polygonal Voltage Space Vector Structure for Variable Speed Drives

Abstract: Generating dense multilevel voltage space structure using polygons of higher sides is one of the novel and elegant method to suppress low-order harmonics and to obtain refined sinusoidal voltages using voltage source inverters for variable frequency drive application without passive filters. Apart from the advantages of conventional multilevel inverter topologies, schemes generating polygonal voltage space vector structure can equip full dc-bus utilization, low switching frequency strategies to eliminate low-order harmonics, and increased linear modulation range. In this paper, an induction motor drive scheme generating a highly dense multilevel 24-sided polygonal voltage space vector structure using a single dc source, which can eliminate harmonics till 23rd order from phase voltages, is presented. Cascaded power circuit topology with a flying capacitor inverter fed with a dc source and two low voltage floating capacitor fed H-bridge inverters is used. Detailed experimentally validated results, under scalar as well as indirect rotor field oriented control of induction motor are provided. Studies on voltage ripple and reactive energy in various floating capacitors, harmonic performance of output voltage for wide range of speed operation, are also included.

Application of an active rectifier used to mitigate currents distortion in 6-10 kV distribution grids

Abstract: The paper addresses issues of using the active rectifier in partially loaded variable frequency drive as active filter in the conditions of non-sinusoidal current and voltage disturbances caused by the presence of high-power non-linear load in the grid The topology of transformless three-level converter for 6-10 kV suitable for proposed solution has been presented and its mathematical model has been de-rived Based on the model, the direct power control algorithm with ability to compensate non-linear currents has been designed The investigation of active rectifier efficiency was performed depending on the relation between linear and non-linear load currents of the grid node, as well as on active power load of the active rectifier Efficiency analysis was based on the developed computer model of the grid node with connected non-linear load simultaneously with the variable frequency drive with active rectifier

High-speed and High-dynamic Variable Frequency Drive Using Modular Multilevel Converter and SiC Devices

Abstract: This paper presents a high-speed and high-dynamic variable frequency drive (VFD) based on the modular multilevel converter (MMC) and silicon carbide (SiC) devices. A compact submodule design with the straightforward extension feature is introduced. An integrated control scheme including the low- and high- speed control is developed. Based on the designed prototype and the advanced control scheme, the dynamic response including speed acceleration and torque step-change capabilities are investigated. Besides, the steady-state performance in the high-speed range is also examined in terms of speed control accuracy and current distortion. Validated by the experimental results, the developed VFD prototype with the proposed control scheme can successfully reach the high speed (6000 rpm). It has accurate speed control (±1%) and low current distortion (THD%=2.54%) in high-speed operation, as well as the robust dynamic response.

Well service pump power system and methods

Abstract: A well service pump system supplies high pressure working fluid to a well. The pump system has a linear design which incorporates an electric motor (212), a variable frequency drive (VFD) (216), a pump drive (220), closed loop variable flow rate hydraulic pumps (224), hydraulic ram cylinders (228), working fluid end cylinders (236), and a coupling to connect the hydraulic ram cylinders (228) and the working fluid end cylinders (236). The electric motor (212) powers the hydraulic system which, in turn, provides hydraulic fluid to operate the hydraulic ram cylinders (228). The VFD (216) is connected to a single one of the hydraulic pumps (224) at a time and applies power to the connected pump, via the pump drive (220), to drive the connected pump from a cold start to an operating speed. The VFD (216) is connected sequentially, one pump at a time, to each of the hydraulic pumps (224) and disconnected from each pump once the pump reaches the operating speed. Once the pump (224) reaches operating speed, the pump is connected to receive power directly from the electric motor (212).

Design and Development of Three-Phase Voltage Source Inverter for Variable Frequency Drive

Abstract: Three phase induction motors are the workhorse of industry. Variable speed operation of the motor enables substantial energy savings through implementation of variable frequency drives. This project concerns on the design and implementation of three-phase voltage source inverter (VSI) for variable frequency drive. The focus was to generate variable frequency output suitable to be fed to the induction motor for the purpose of variable speed control. SPWM signal was generated through SIMULINK algorithm. The VSI circuit was designed, fed with SPWM trigger signal and simulated for variable frequency output in terms of line-to-neutral and line-to-line voltage across R-L load. In the experimental setup, the real VSI system was developed, the SPWM trigger signal generated through SIMULINK and interfaced to hardware using Arduino microcontroller. The output is dropped across resistive load and parameters line-to-neutral and line-to-line voltage was measured. Three set of output voltage with frequency of generated at 20Hz, 50Hz and 70Hz. Thus, experimental result validated that variation of frequency of voltage output of the VSI has been successfully achieved.

Operational Parameters Affecting Harmonic Resonance in Electrical Submersible Pump Systems

Abstract: Electrical submersible pump (ESP) systems in the oil field have unique features due to the long cabling effect. The electrical system for a typical ESP installation consists of a variable frequency drive (VFD), a multi-tap step-up transformer, a surface cable, a downhole main cable, a motor lead extension (MLE) cable, and an electrical submersible motor. A load filter is usually required in a VFD-ESP system. In this paper, several operational parameters that can significantly affect operating conditions of an ESP system are demonstrated through field measurements and simulation of a practical ESP system currently in operation in Alberta, Canada. The simulation model is also validated by comparing with field measurement data. This analysis is beneficial to field engineers and ESP system operators to understand better the impacts of equipment parameter settings.

Reliability analysis of application of variable frequency drive on condensate pump in nuclear power plant

Abstract: The aim of this paper is to analyze the reliability of Variable Frequency Drives (VFD) when used to control condensate pump motor in a nuclear power plant. IEC 60812 system reliability analysis pro...

Thermal Characterization of SiC Modules for Variable Frequency Drives

Abstract: In this paper, the advantages of SiC power modules to reduce peak junction temperature and power cycling effects are presented. A detailed power loss calculation and thermal model is developed and tested on a 480 V, 190A, 150 HP variable frequency drive (VFD) with SiC modules. A comparison between the SiC module and an equivalent rated Si module is presented to demonstrate the reduction in power cycling effects, particularly at low speed operation. Infrared (IR) imaging results and an analytical explanations of the phenomenon is provided. These results show that SiC inverters can be used for high torque and low speed applications. Also, the reduction in junction temperature swing improves reliability.

Sub-Synchronous Torsional Interactions and Start-Up Issues in Oil&Gas Plants: a Real Case Study

Abstract: This paper provides theoretical determination and experimental validation of the currents interharmonics of a Thyristor Variable Frequency Drive (TVFD) in an Oil&Gas plant. Currents harmonics imply torque harmonics of the turbine generator resulting in Sub-Synchronous Torsional Interactions (SSTIs). This phenomenon can lead to blackouts of the plant or damage of the equipment. An integrated electrical and mechanical simulation model allows to emulate the behavior of the overall Oil&Gas plant at the start-up of the moto-compressor train. During the start-up interharmonics are frequency-variant, hence it represents a condition particularly critical for the turbine generator.

Effects of Harmonic Distortions on the Accuracy of Energy and Power Losses Measurements in a Water Treatment Industry

Abstract: Harmonic distortions in electric power system are the main power quality concerns, mostly generated by nonlinear loads such as Variable Frequency Drive (VFD). A water treatment industry usually utilizes VFD to control their water pump motors during the operation. In this study, we investigated the effects of harmonic distortion resulted from VFD on the measurement accuracy in the distribution system operated by state-owned electric utility. The results showed that the VFD that employed the pulse width modulation (PWM) technique has adjusted the supply frequency of 50 Hz into specific number to control the speed of motors. Data recorded on energy meter for seven days exhibited the THD V of 3.27% and THD I of 36.37%. We found that the harmonic distortion has caused the energy measurement error of 1.2%, and this becomes potential losses for the utility because it could not be charged to customers due to the government tariff regulation

Vector control system, control method and device, air conditioner and storage medium

Abstract: The invention provides a vector control system, a control method and device, an air conditioner and a storage medium. The vector control system comprises a control module and a variable frequency drive module, wherein the control module comprises a weak magnetic current, a maximum torque current ratio control unit and an adjustment module; the variable frequency drive module receives an input pulse width modulation signal and is used for inverting the DC signal into a three-phase AC signal to input the signal in a permanent magnet synchronous motor, wherein the current output of the three-phase AC signal is increased by injecting the weak magnetic current so as to make the permanent magnet synchronous motor generate heat. The vector control system increases the current output of the three-phase AC signal by injecting a weak magnetic current into the permanent magnet synchronous motor such that the permanent magnet synchronous motor can generate heat, which realizes the function of low-temperature heating only needing to increase the weak magnetic current by means of software control with no need to modify the existing compressor structure. And the vector control system is applied to the outdoor unit of the air conditioner, which helps to reduce the production cost of the enterprise with a simple structure and is easy to implement.

FPGA Accelerator for Real-Time Emulation of Power Electronic Systems Using Multiport Decomposition

Abstract: Development of accurate Real-Time systems with power electronic converters is a challenging task due to its high switching frequency and the time varying circuit topology. This paper explains the strategies to implement power electronic circuit models in real time, by exploiting the parallel and distributed computing nature of FPGA, with three-phase-three-level diode-clamped inverter as a case study. A generic multiport decomposition technique is applied to improve parallelism and to reduce the size of the matrix for the computation. Also, by developing a PySpice based utility, which pre-computes all the system matrices from the given netlist, implementation is made more adaptable to different partitions and circuit variations. Target circuit is implemented in C/C++ language, converted to VHDL and implemented on ZedBoard (XC7Z020) using Xilinx Vivado tools. With this generalized approach, a latency of less than $5\mu\mathrm{s}$ is achieved with reasonable utilization of resources, on FPGA. Real-Time performance of the implemented inverter model with Sine-Pulse-Width-Modulation technique is verified by connecting in loop with the induction motor model for its speed control. A latency of $6.65\mu\mathrm{s}$ is achieved within each simulation time step for the closed loop control of induction motor which is sufficient for the wide range of variable frequency drive applications.

Impulse Voltage-based Test Method for Identifying the Stator Insulation Component with PD Activity for Low Voltage AC Motors

Abstract: IEC 60034-18-41 has been developed as a standard acceptance test to ensure partial discharge (PD)-free operation for improving the reliability of low voltage (LV) variable frequency drive (VFD) motors. Although the test can verify whether PD exists in the stator for a voltage surge with predetermined magnitude and risetime, the information on where PD activity is occurring in the stator insulation is not clearly given. In this paper, a method based on variable risetime surge voltage testing is proposed for identifying the component of the stator insulation system where PD occurs in LV random wound motor stators (turn, phase, or ground insulation). This information can be used for increasing the PD inception voltage for improving the reliability of the motor through insulation system design/manufacturing. The test is implemented with a 4.5 kV variable risetime surge generator prototype. 4 LV ac motors are tested to show where PD is likely to occur in commercial LV motors.

Variable frequency drive optimization using torque ripple control and self-Tuning PI controller with PSO

Abstract: Drive’s output power must be restricted for the prevention of stresses over higher components in the input power system while utilizing a three-phase Variable Frequency Drive (VFD) which has powered from a single-phase AC source. To resolve this problem, we introduced a novel motor q-axis current (M-QAC) with torque ripple control (TRC) of an induction motor and self-tuning PI controller with particle swarm optimization (STP-PSO) for mitigating the stress over induction motor by the torque ripple elimination and controlling. Our proposed approach has an information related to the different parts stresses of the VFD which includes the terminal block and the diodes in the input side, DC bus capacitors, torque ripple, harmonics in the current and active performance for sudden changes in the speed and load. Our proposed model is simulated in MATLAB/Simulink environment. In this paper the standard dc-bus voltage ripple-based fold- back, q-axis average current fold-back and q-axis ripple current fold-back methods are utilized for the comparative analysis. Also the comparative analysis of proposed M-QAC, TRC and STP-PSO methodologies are provide with respect to steady-state values of peak-to-peak dc voltage (Vdc), peak-to-peak input current (IINPUT), input RMS current (IRMS), motor speed and the output power. Extensive simulated performance show that the STP-PSO obtained superior results over conventional standard dc-bus voltage ripple-based fold-back method, M-QAC and TRC schemes.

Air cooled variable-frequency drive

Abstract: Methods and apparatus for simultaneous operation of a variable-frequency drive (VFD) and a controller. The VFD drives an electric motor of a drilling rig machine. The controller controls temperature of an insulated-gate bipolar transistor device (IGBT) of the VFD by controlling an air mover in response to real-time temperature data. The air mover generates airflow into a passage, the airflow thereby interacting with radiating members extending into the passage from a heat sink thermally coupled with the IGBT in the inner housing outside the passage.

Performances of Asynchronous Motor within Variable Frequency Drive with Additional Power Source Plugged via Combined Converter

Abstract: The paper deals with analysis of induction motor operation when it is fed by two sources – one is the frequency converter, the second is a low voltage DC source like photovoltaic panel or fuel cell connected in a special manner via the neutral point of the motor. In this special schematic solution, the switches of frequency converter are controlled by proper algorithm that allows transmitting the energy to the DC link. In the article, the effect of the additional current components on the motor's performances is estimated. Detailed mathematical description of the motor within such combined converter is given, simulation results are shown. Recommendations regarding the values of components providing the best operation are given as well.

Control of D-STATCOM for Asymmetric Voltage Dips Compensation

Abstract: The variable frequency drive (VFD) is sensitive to distortions at the point of common coupling (PCC). Decreasing of the voltage at the PCC for more than 50 ms leads to the shutdowns of VFD and breaks the process. As a result, it leads to emergency situations, defects and under-release of products. The VFD of rolling mills, gas pumping compressors, stations for maintaining reservoir pressure and other powerful electrical equipment are sensitive to voltage dips. The phenomena of a voltage dip often caused by short circuits or starts of a powerful load. Often short circuits accurse in one or two lines and lead to asymmetric voltage dips. The article describes the D-STATCOM control method to compensate for asymmetric voltage dips, although usually D-STATCOM is used to reduce symmetrical voltage dips. The obtained analytical expressions for solving the inverse problem of determining the voltage of a series-connected compensator show the possibility of using it to compensate for voltage dips

VFD Control for Industrial Machines using PLC and LC Filter

Abstract: Variable frequency drive (VFD) and servo drive usage in the industrial application are increased in a large amount. The control of VFD can be done using a programmable logic controller (PLC). The apparatus includes a main controller i.e. VFD and first interface PLC. The motor controller (VFD) is coupled to the PLC and controls the electric motor according to the application. PLC is further coupled to Human Machine Interface (HMI) to show the operation visually. An input to VFD is given from the PLC to run the motor and outputs from the VFD is controlled frequencies, which control the speed and torque of a motor. Harmonics, motor bearing damage, motor noise, electromagnetic interference are observed in the pulse width modulated (PWM) VFD fed induction motor. A sinusoidal LC filter is placed between the VFD and motor to smoothen the pulse width modulated waves into sinusoidal waves, which basically reduces the noise and effectively improve the overall efficiency of VFD.

Repairing and commissioning of an AC motor speed controller for a centrifugal pump

Abstract: A centrifugal pump was installed in 1984 in the Fluid Mechanics Laboratory of Mechanical Engineering Department of Rajshahi University of Engineering & Technology. The motor of the centrifugal pump was dc motor and was not working. It could not be commissioned for a long time because of the damaged speed controller. The main shaft (rotor) was also jammed. In this project work, the dc motor was tried to repair. But it could not be run because the specification of the motor and the operating manual was not available. To complete the project successfully, the dc motor was replaced by an ac induction motor. After replacing the motor, the speed of the new motor was controlled by a variable frequency drive (VFD). Using this device, the speed was controlled from 600 rpm to 3000 rpm smoothly. After the replacement, the testing of the centrifugal pump was successfully performed and the motor was controlled in various speeds. Experiment on the performance test of the centrifugal pump was carried out satisfactorily running the pump in various speeds operated by the VFD.

Integrated A Variable Frequency Drive for a Diesel-Generating Set using the Genset-Synchro Concept

Abstract: This paper examines the feasibility of implementing a variable frequency drive based on real-time control of the stator speed for a standby diesel generating-set using Genset-Synchro technology. The controller algorithms are designed using the Code Composer Studio version 8.0 software in C code, which can be downloaded to the digital signal controller TMS320F28335 from Texas Instruments in real-time. The paper shows results for the compensator motor that drives the stator speed to maintain the voltage and frequency at the output fixed. The results show the possibility to meet the performance class criteria of ISO 8528 part 5 G2 when diesel generators are equipped with Genset-Synchro technology. Keywords— Variable Diesel Generator, Genset-Synchro, EoSynchro, Real-Time Control, ISO 8528, Variable Frequency Drive.

Study of the effectiveness of a variable frequency drive of an induction motor

Abstract: The results from a study of the effectiveness of a variable frequency drive of an induction motor, are presented in the paper. The electric power savings when regulating the voltage and the output frequency of the frequency converter are analysed. The power losses when varying the angular speed and the load, and also the efficiency of the obtained power drive system, are determined.

Real-Time Power Control of a Permanent Magnet Synchronous Generator Based Wind Turbine Through a Laboratory Test-Rig

Abstract: In this work, a discrete Real-time laboratory test rig is used to control the power or torque of a permanent magnet synchronous generator (PMSG) based Wind Turbine Generator (WTG) to analyze its behavior in a variable speed operation. A Variable Frequency Drive (VFD) controlled Induction Motor (IM) is used as a wind turbine emulator to drive 5kVA PMSG. Moreover, an inverter is directly connected to the stator winding to facilitate the power control of the WTG in real-time under various scenarios. For implementing PI controllers to control the power of the WTG in real-time, Texas instrument TMS320F28069 Digital Signal Processor (DSP) discrete real-time microcontroller control card in a GUASCH board is used. In addition, the simulation model of the system is prepared in MATLAB Simulink to be validated by the results of the test rig. Finally, the achieved results of the simulation and test rig indicate the real-time power control results of the system validates the MATLAB simulation model results of the system.

Designing Passive Harmonic Filter on Dynamic Positioning Vessel's Electrical System Affected using Electrical Thruster

Abstract: Ship with a dynamic positioning system has the ability to maintain her position dynamically. To be able to maintain the position, generally, ship with a dynamic positioning system have several thrusters located at bow or stern of the ship. Based on the propulsion system, there are 2 types of thruster which are mechanical thruster and electrical thruster. In electrical type, the thruster is driven by an electric motor supplied from the generator. In addition, on dynamic positioning vessel equipped with the electrical thruster, there are also VFD or Variable Frequency Drive to control the speed of motor thruster. The use of VFD components in the system may cause harmonic interference. Harmonic itself can be regarded as distortion in the sinusoidal waves due to the interference of other waves that have integer frequency multiples of their fundamental frequency due to the operation of non-linear thruster motor. Some of the most affected components of this distortion are the communications equipment and the components used for measurement. This research conducted an analysis of harmonic disturbance arising from the operation of 2 units bow thruster on DP Ship by simulating 6 scenarios of generator configuration using simulation software . The results from this research were total harmonic distortion value or VTHD of the system that complies with standards and rules, also the specification of a passive harmonic filter to reduce the VTHD value at the specific harmonic order.

System and method for motor drive control

Abstract: A method of controlling operation of a motor drive system includes receiving motor drive data corresponding to a variable frequency drive. The motor drive data includes a plurality of frequency drive input parameters and a plurality of frequency drive output parameters. The method further includes receiving, by a digital variable frequency drive unit, the plurality of frequency drive input parameters. The digital variable frequency drive unit is a real-time operational model of the variable frequency drive. The method further includes generating, by the digital variable frequency drive unit, frequency drive output parameter estimates corresponding to the plurality of frequency drive output parameters. The method also includes controlling operation of the variable frequency drive based on the one or more of the motor drive data, and the frequency drive output parameter estimates.

DC Side Oscillation Suppression Strategy of Metro Traction Converter Based on Indirect Vector Control

Abstract: Asynchronous motor traction variable frequency transmission system has been widely used in the industrial and transportation track industry. Vector control has become the mainstream of AC speed control due to good control performance. However, in such a system, due to the instability of the DC side negative impedance, the system damping is reduced, and the DC side LC filter is prone to oscillation, which affects the stability and normal operation of the variable frequency drive system. In this paper, without increasing the hardware circuit, the control strategy is used to improve the system characteristics and suppress the occurrence of the oscillation phenomenon. The effectiveness of the oscillation suppression strategy is proved by simulation and implementation.