Harmonic Current Limits Research Articles

Single-Phase Universal-Input PFC Converter Operating at High Frequency

Single-phase ac to dc converters for computers and related applications have requirements that are difficult to meet while achieving both high power density and high efficiency: wide input voltage range, large voltage step down, galvanic isolation, harmonic current limits and hold-up requirements. This work explores a circuit architecture and topology that is structured to facilitate operation at multi-MHz frequencies in order to address this challenge. We present a 250 W, 24 V output, universal input PFC converter prototype that leverages the proposed approach to achieve a power density of 34.9 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> while meeting the 80 PLUS Platinum efficiency standard, EN61000-3-2 line harmonic requirements and half-cycle holdup. The converter operates at variable switching frequencies in the range of 1-4 MHz; the measured efficiency at 230 Vac RMS, 60 Hz input is 95.33% at full load and 84.57% at 8% load.

Sensitivity Analysis Approach of New Dynamic Harmonic Distortion Current Limits on Utility Grids

—Harmonic levels in distribution power systems are expected to rise in the future. Understanding the consumer load composition of each individual circuit and maximum harmonic limits can help utilities plan and mitigate power quality issues. This paper presents a sensitivity analysis approach of IEEE Standard 519 total harmonic distortion (THD) current limits on an actual utility model. A new dynamic harmonic index method for characterizing distribution power circuits is proposed, which utilizes the short circuit ratio (SCR) as the main parameter. OpenDSS is used as a modeling platform to study the THD of the voltage (THDv), while increasing the harmonic spectrum of random consumer load points. The main goals are to: (1) identify voltage behavior in power utility networks when an increasing number of consumers operate at the Std. 519 limits, and (2) categorize utility circuits using available information. The short circuit at the point of common coupling, maximum demand load currents, and the circuit configuration are considered. Three actual utility circuits are analyzed and compared in terms of their SCR and one of these circuits is analyzed in depth as part of the sensitivity study. The proposed method is also compared with the conventional pure capacitor and tuned filter bank methods. Finally, a recommendation for new harmonic distortion current limits is provided.

Harmonics Measurement in Computer Laboratory and Design of Passive Harmonic Filter using MATLAB

In this paper the harmonics measurement for computer loads is analyzed and passive filters are designed for mitigating those harmonics. The filters are designed to meet the IEEE standard 519-1992 which is recommended for harmonic current limits. Personal computers are non-linear loads that generate harmonics due to non-sinusoidal current present at entrance of power supply. In this work the personal computers in laboratory are taken as domestic load and harmonics generated by them cannot be ignored which are simulated using MATLAB/Simulink. The purpose is developing analytical method for the design of the passive harmonic filter that absorbs current harmonics caused by computer loads. The findings of this study would be supportive to make the source current free from harmonics thereby reducing the THD. Simulation results of proposed design method of passive filters shows attractive results for harmonic reduction with profit of upgrade of power factor. Design of passive harmonic filters by using non active power can be simple cost effective solution for systems.

Spectral Analysis of Harmonic Measurement Using Wavelet Transformation in IEEE -13 Bus System

An efficient compensation method and design for sizing the three phase four wire shunt Active Power Filter (APF) based on wavelet transformation is presented in this paper. The compensation currents injected by shunt active power filter are determined to eliminate harmonic currents of the non linear loads as well as to compensate reactive power and maintain the source currents as sinusoidal. In this paper Fast Fourier Transforms (FFTs) is used for APF to calculate reference compensation current. Proposed APF has the capability to operate in balanced, unbalanced and variable load conditions. The proposed auto tuned filter meet the IEEE – 519 harmonic current limits and other constraints like power factor improvement and reactive power compensation. The proposed methodology is tested for different loads with good dynamic behavior of APF using wavelet controllers. The results obtained by simulations with MATLAB/Simulink shows that the proposed approach is very effective and simple for compensating harmonic currents generated by the nonlinear loads with an optimal size of the shunt active power filter.

Harmonic emission limits and responsibilities at a point of connection

A customer expects to receive a voltage supply at his installation that meets the requirements of standards like (national) grid codes, EN50160 standard etc. under normal operating conditions. On the other hand, the devices connected to a customer's installation should meet power quality (PQ) requirements as given in the IEC standards (and other relevant product standards). In contrast, present standards give very limited information about the PQ requirements at a customer's point of connection (POC). Modern household customers use many power electronic-based devices for their daily usage. Those devices inject harmonic currents and all together distort the network's voltage. It is noticed from surveys that harmonic-related inconveniences are increasing in the power system. Some field measurements (on harmonics) in the Dutch low-voltage (LV) network will be discussed in this paper. Also, harmonic simulation is done on a typical LV network that supplies electricity to several households. Both the field measurements and simulation results are compared with the limit values of the standards. Further, harmonic current emission limits at different customers' installations are derived. This information would be helpful for the customers to know their rights and responsibilities in the network. Additionally, a proposal is made about new planning level values of harmonic voltages in the network. Finally, a methodology is developed to assess harmonics-related responsibilities of each of the involved parties in the power system, and it is shown where these can be applied.

Nonlinear Current Control of Single-Phase PFC Converters

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A set of new nonlinear current control methods are presented for single-phase power factor corrected ac–dc converters. These control methods combine input current feedforward with partial feedback based on the switch current to achieve sinusoidal input current and unity input power factor. They overcome the limitations of conventional linear (average) current control in terms of control bandwidth and sensitivity to noise, resulting in high-performance input current control which can meet the most stringent harmonic current limits required by variable-frequency airborne power systems. The control methods are also ideally suited for integrated mixed-signal implementation, requiring an analog current controller which is very simple, much less sensitive to noise than conventional linear feedback control, and independent of converter and control design parameters; and a digital controller which operates with a sampling frequency much lower than the switching frequency. Detailed development of the control methods is presented along with their stability analysis and circuit implementation. A prototype converter and its operation are also presented to validate the analysis and to demonstrate the performance of the control methods. </para>

Meeting IEEE-519 Current Harmonics and Power Factor Constraints With a Three-Phase Three-Wire Active Power Filter Under Distorted Source Voltages

An efficient steady-state compensation method and a conceptual design for sizing the three-phase three-wire shunt active power filter (APF) under nonsinusoidal source voltages are presented in this paper. Conventionally, the compensation currents injected by the APF are determined to eliminate harmonic currents of the nonlinear load as well as to compensate reactive power and maintain the sinusoidal source currents. However, the subject related to the optimal control of the APF to meet the IEEE-519 harmonic current limits and other constraints, such as minimum load power factor requirement after compensation with an optimal kilovolt-ampere rating, are rarely investigated. In this paper, an optimization-based solution algorithm is proposed to determine the three-phase three-wire APF current injections to meet different constraints with an optimal filter size, where the voltage compensation-based control strategy is formulated as a nonlinear programming problem and is solved to find the optimal compensator gains and APF current injections. Results obtained by simulations with Matlab/Simulink show that the proposed approach is very flexible and effective for compensating harmonic currents generated by the nonlinear load with an optimal size of the APF.

A New Approach for Optimal Shunt Active Power Filter Control Considering Alternative Performance Indices

A new steady-state approach for determining the optimal shunt active power filter (APF) reference compensation current injections to control harmonic currents generated by the nonlinear load and for reactive power compensation under ideal or nonideal supply voltages are presented in the paper. Conventionally, the compensation currents injected by the shunt APF are determined to eliminate harmonic currents of the load. However, when considering different APF performance indices such as minimizing source current distortion and maximizing compensated load power factor, the issues related to sizing the APF to meet IEEE-519 harmonic current limits and other constraints such as current imbalance limits and minimum load power factor requirement are rarely investigated. In the paper, a new theory of APF control in the a-b-c reference frame is proposed to determine the APF current injections to meet different constraints with an optimal APF size, where the filter control strategy is formulated as a nonlinear programming problem and is solved to find the optimal current injections. Results obtained by simulations with Matlab/Simulink show that the proposed approach is more flexible and effective than the conventional approaches on compensating reactive power and harmonic currents of the load.

Optimisation-based strategy for shunt active power filter control under non-ideal supply voltages

A new theory and a conceptual design for the three-phase shunt active power filter (APF) control strategy under imbalanced and distorted supply voltages are presented. Conventionally, the compensation currents injected by the APF are determined according to reference frame transformation-based approaches, where the load instantaneous real and reactive powers are calculated in the new reference frame. The APF injection currents are then computed to maintain the balanced and sinusoidal source currents, as well as the least active power consumption by the APF. However, if current harmonics set by harmonic standards or other constraints are considered, the load harmonic currents after APF compensation can be controlled to meet the requirements. Therefore, the APF may have an adjustable performance. An optimal algorithm for the APF control in steady state is proposed, in which the individual and total harmonic current distortion limits, the minimum load power factor, levels of current imbalance and the size of the APF can be taken into account. The planned APF does not consume or produce active power and only the passive energy-storage elements are required in the new APF design. Results obtained by simulations with Matlab and Simulink show that the proposed approach is more flexible than conventional approaches for compensating reactive power and harmonic/neutral currents of the load, even if the source voltages are severely distorted and imbalanced. The new control strategy is very suitable for planning the APF when several alternative objective functions and constraints are under considerations.

A PV dispersed generator: a power quality analysis within the IEEE 519

The use of environmentally clean photovoltaic (PV) dispersed generation will become more widespread in the future due to anticipated cost reductions in PV technology. This paper summarizes the results of a power quality (PQ) study performed on a PV generator in order to estimate the effects that inverter-interfaced PV dispersed generation might have upon the quality of electric power. Different interpretations of the harmonic distortion limits set in the IEEE 519-1992 standard are performed together with a comparison with the BC Hydro's harmonic current limits. This paper also includes a statistical analysis of all measurements recorded with the help of two PQ monitors, an evaluation of the results from a connection/disconnection test, and harmonic simulation results.

Application of dominant harmonic active filter system with 12 pulse nonlinear loads

Harmonic filtering is required for 12 pulse rectifier-utility interface to meet IEEE 519 harmonic current limits. Passive filter techniques employ tuned L-C filters at dominant 11th and 13th harmonic frequencies. However, they also require 5th and 7th tuned filters to avoid series and parallel resonance conditions. State of the art active filtering solutions require high bandwidth and relatively large rating PWM inverters for harmonic filtering of 12 pulse rectifier loads. Thus existing passive and active harmonic filtering solutions are not cost-effective for high power 12 pulse rectifier loads. Dominant harmonic active filter (DHAF) based on square-wave inverters is proposed to cost-effectively meet IEEE 519 harmonic current limits for 12 pulse rectifier loads. The proposed DHAF system employs square-wave inverters switching at 5th and 7th harmonic frequencies, which are transformer coupled in series with 11th and 13th passive filters respectively. The square-wave inverters are controlled to provide 'harmonic isolation' between the supply and load at 5th and 7th harmonic frequencies. The square-wave inverters are rated 1%-2% of the load kVA rating. The proposed DHAF system eliminates the need for large kVAR rated and bulky 5th and 7th passive filters, delivers superior harmonic filtering performance, and provides cost-effective harmonic filtering solution. Simulation results are given to validate the 'harmonic isolation' feature at 5th and 7th harmonic frequencies, and also demonstrate harmonic filtering required to meet IEEE 519 harmonic current limits.

Uncertainties in compliance with harmonic current distortion limits in electric power systems

The recent widespread use of static power converters has brought about the need to set limits on harmonic distortion to avoid noise and interaction problems in the power system. The harmonic distortion of any repetitive voltage or current waveform is typically described by the quantity total harmonic distortion (THD). Proposals have been made to limit harmonic currents in power systems using the total harmonic distortion of the current as the criterion. This criterion, although it may be necessary, can be ambiguous and lead to compliance uncertainties. A discussion is presented on several of the practical problems by applying total harmonic current distortion limits to industrial and commercial power systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>