On waveform distortion in the frequency range of 2 kHz–150 kHz—Review and research challenges

This paper presents an in-depth comparative analysis of the variable speed drive (VSD) performance between an IEC frame size 90 four-pole three-phase induction motor (IM) and the equal line-start interior permanent magnet synchronous motor (LSIPMSM). Employing measurement data from no-load tests, load tests, and temperature-rise tests of the aforementioned motors and different cage materials as well, the motors' no-load and load characteristics are first examined in detail and then the drives' characteristics are analyzed in open-loop volts per hertz (V/f) control by using the same voltage-source inverter and the aforementioned IM or LSIPMSM in both constant torque and constant power operation. It has been established that particularly the motors' current and power factor characteristics have distinct impact on the consequent VSD performance in terms of loss and efficiency. Furthermore, it has been shown that the lower loss of the LSIPMSM enables a significant increase of the VSD's constant power range.

Comparison of Induction Motor and Line-Start IPM Synchronous Motor Performance in a Variable-Speed Drive

Motors in semi-hermetic compressor drives are mostly fed from line. Because of good cooling conditions, the motors are heavily loaded and employ a specific rotor structure with “C” bore. In the field of semi-hermetic drives, the use of induction motors (IMs) is still dominant, although different motor types with line-starting capabilities, as for example line-start interior permanent magnet synchronous motors (LSIPMSMs), can be used. This work presents the direct performance comparison of a family of commercially available three-phase four-pole IMs for semi-hermetic compressor drives with the equal size prototypes of LSIPMSMs. The motors were rated as 1, 2.5, 3.8, 5.5, 7.5, and 20 hp. The presence of “C” bore in rotor structure can degrade LSIPMSM steady-state performance; therefore, the LSIPMSM designs steady-state performances are evaluated by FEA as well by the experimental method. The motors' dynamic performance is experimentally evaluated as well. The ultimate goal of this study is to reveal the improvement of LSIPMSMs characteristics in comparison to IMs characteristics and to check the possibility for the immediate replacement of existent IMs with LSIPMSMs in the target semi-hermetic compressor application.

Direct Comparison of Induction Motor and Line-Start IPM Synchronous Motor Characteristics for Semi-Hermetic Compressor Drives

LED lamps are both potential victims and sources of electromagnetic disturbances in the frequency range between 2 and 150 kHz (“supraharmonics”). Immunity tests for this frequency range are important due to possible performance degradation of light intensity with LED lamps. In this paper, the impact of supraharmonics (SHs) on light intensity from LED lamps has been analyzed. LED lamps have been exposed to SH test profiles based on IEC 61000-4-19. Three phenomena that impact light intensity metrics have been observed and explained by models: 1) earlier conduction/later blocking caused by SH voltage, 2) intermittent conduction depending on the SH impedance of the LED driver, and 3) reverse-recovery current of the diodes at higher frequency. It is observed that impact on the light intensity metrics shows up around the beginning and end of the conduction period. The results reveal that the profile of the SH voltage could cause deviations in the modulation depth and the average light intensity. The immunity of LED lamps against SHs shall be further studied and discussed by research groups and standard committees.

Interferences in AC–DC LED Drivers Exposed to Voltage Disturbances in the Frequency Range 2–150 kHz

Improvement of power electronic technologies can also introduce various new types of distortions in electrical power systems due to high switching frequency of power converters. The emissions from one device can create noticeable impact on other devices connected to the same system, which may raise immunity concerns. Moreover, power line communication and ripple control signaling may have implications due to the presence of these harmonics. This paper demonstrates analysis of harmonic distortions in the frequency range of 9 – 150 kHz in low voltage distribution networks. Detailed study of voltage and current harmonics is performed based on field measurements with different load characteristics and solar inverter integration. A simulation study of 5 kW inverter control is shown to demonstrate the effect of controller strategy for current harmonics. The results could be useful in development of high frequency harmonic regulations for grid connected inverters in distribution networks.

Analysis of High Frequency Harmonics in Distribution Networks: 9 – 150 kHz

This paper discusses different approaches to investigate the interaction through harmonics, interharmonics, supraharmonics, and light flicker, between photovoltaic (PV) inverters and LED lamps in low-voltage installations. Single grid-connected power generators and electronic loads like LED lamps can be easily characterized in terms of harmonics in a given range of frequency. This subject is relatively well understood, and specific standards for measuring and restricting emissions are already established to ensure a low probability of interference. However, when connected together, source and load exhibit behavior that requires further study and understanding. This work presents a discussion serving as a guide for future work on analysis of losses and other impacts of the disturbances regarding this specific load and source interaction. The following are taken into account: the nonlinearity of LED loads and PV converters; the technologies and methods used in control; and the changes in power flow caused by load and power production variations.

Interaction between grid-connected PV systems and LED lamps: Directions for further research on harmonics and supraharmonics

Increasingly, consumer electronic devices utilize power supplies that have switching frequencies up to several tens of kilohertz. Consequently, emission in the frequency range 2 to 150kHz ('supraharmonics') is continuously increasing. Cases of conducted interference in LED lamps using switched mode power supplies, from supraharmonics have been reported over the past three years. This paper presents results from experiments where supraharmonic voltage distortion was applied to commercially available LED driver circuits. Variations of light output were obtained in some cases, along with evidence pointing to reduced converter efficiency and influence of point on wave of the distortion, on the light output. Importantly, it was shown that electromagnetic compatibility is not converter topology dependent, nor influenced by galvanic isolation. The results demonstrate that converters with similar topology can have vastly different behavior and there is a marked dissimilarity in performance among different topologies.

Impact of high frequency conducted voltage disturbances on LED driver circuits

The growing demand for electricity in developing countries calls for a continuous increase in the installed capacity. However, with installed capacity unable to meet the pace of increase in demand, increase in efficiency of energy conversion devices is a vital requirement. The present paper considers one such energy improvement method in the form of a Line Start Permanent Magnet Synchronous Motor (LSPMSM) which is intended as a substitute for induction motors in developing countries. The economic benefits due to the utilization of such machines, their commercial viability and their life cycle costing have all been considered here. The paper also presents theoretical results obtained for various rotor configurations of the LSPMSM and practical results for the selected spoke type rotor geometry.

Effective energy conservation for the agricultural sector using line start permanent magnet synchronous motors

The penetration of Distributed Energy Resources (DERs) on the power system has come with its own set of problems, especially in the power quality domain. As DERs continue to be integrated at the transmission and sub-transmission voltage level, power quality engineers are faced with the unique situation of having to regulate a source of generation rather than a load. One of the important outcomes of such integration has been the concern about increase in cases of rapid voltage change (RVC). While there is evidence to indicate that DERs themselves do not contribute much to voltage fluctuations in the power grid, there have been recorded instances where the energization of transformers used to integrate DERs to the grid has led to an RVC event. This paper presents the current status of research on RVCs, particularly in terms of regulation, and then outlines the various methods and strategies that can be used to counter the problem of RVC that results from energization of transformers on the utility grid. A case study from an RVC event caused by transformer energization is presented and then used as a baseline, to study the effect of various mitigation techniques, using EMTP simulations. Various techniques have been contrasted and compared in terms of cost and effectiveness. The paper finally closes with a discussion of the future avenues and expected work with regards to Power Quality in this field.

Assessment of Best Practices for Mitigation of Rapid Voltage Change due to Transformer Inrush

The increasing popularity of inverter based Distributed Energy Resources (DERs) and single-phase power electronics based consumer load in North America, has resulted in an increase in emission in the frequency range 2 to 150 kHz, also known as ‘supraharmonics’. Despite increased awareness, measurement of such emission is beyond the capability of existing Power Quality (PQ) monitoring infrastructure for most American utilities. Further, upgrading existing PQ measurement infrastructure to extend its capabilities is a costly and time intensive endeavor. This paper proposes to overcome this problem by detecting the magnetic field radiated by sources of supraharmonics using cheap ‘off the shelf’ sensors, rather than the conducted emission. It was found that by sensing magnetic fields, the spectrum of supraharmonic emission can be easily determined, while determining the magnitude of the emission using this method may require careful calibration. This paper describes the theory behind this method, the details of its implementation and measurement results from low power rooftop solar inverters. The paper also shows the use of this method to characterize the radiated emission from solar PV plants, by mounting electromagnetic sensors on a mobile robotic platform. Finally, the paper closes with a discussion of the conclusions and the expected future work in this field.

Gaurav Singh

Papers

Interaction between grid-connected PV systems and LED lamps: Directions for further research on harmonics and supraharmonics

Impact of high frequency conducted voltage disturbances on LED driver circuits

Effective energy conservation for the agricultural sector using line start permanent magnet synchronous motors

Assessment of Best Practices for Mitigation of Rapid Voltage Change due to Transformer Inrush

Detection of High Frequency Conducted Emission using Radiated Fields