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In the two-stage converter such as PV renewable energy system, the second harmonic fluctuation exists in the DC voltage due to the power coupling between the DC-link and AC system. The second harmonic voltage in the DC link could increase the system loss and decrease the stability of the converter system, and its generation process and transmission mechanism are analyzed in this paper. The mathematical expression of second harmonic voltage in DC-link has been derived. A second band passing filter (BPF) feedback control loop is used to feedback the second harmonic ripple voltage in DC link into the statable modulation index. This strategy can decrease the second harmonic voltage in the DC-link and the third harmonic voltage in the AC sides. Finally, the control parameters are implemented using a simulation platform, and the match suppression strategy is validated by the simulation results.

Leakage current measurement is the most reliable and effective method for condition monitoring of overhead insulators deployed in the field. However, a major challenge in the leakage current based insulator monitoring is to interpret the indices extracted from the leakage current measurements under varying harmonic content in system voltage. This paper reports the possibility of employing the instantaneous value of time-integral of leakage current as a low-sensitive parameter for the monitoring of leakage current in overhead insulators in the presence of voltage harmonics. It has been shown that any change in the harmonic content of the system voltage has a significant influence on the harmonic characteristics of the leakage current, but has a comparatively less severe effect on the time-integral. The monitoring technique has been validated through laboratory recorded experimental data and incorporated in an online measurement device that has been tested in the laboratory.

Nowadays permanent magnet synchronous machines those frequency-controlled from stator side with frequency inverters made on the basis of power transistors or fully controlled thyristors, are widely used as motors and generators. In future they are also promising a good application in transport, including marine. Modern frequency inverters are equipped with a control system based on sine-shaped pulse width modulation. While shaping the voltage in the output of the inverter, in addition to the fundamental harmonic, higher harmonic components are also included in the voltage shape, which certainly affect the operating parameters of the generator (electromagnetic torque, power, currents). To determine this effect the modeling and investigation technique of higher harmonic voltages in the "electric network – frequency converter – synchronous machine with permanent magnets" system has been developed. The proposed equations of a frequency-controlled permanent magnet synchronous machine allow relatively simply reproduce the harmonic composition of the voltage in the output of a frequency inverter equipped with the control system based on a sinusoidal pulse width modulation. The developed research technique can be used for inverters with any number and composition of voltage harmonic components feeding a stator winding of a permanent magnet synchronous machine. On a particular case, the efficiency of the research technique of the higher harmonics influence on the operating parameters of the generator has been demonstrated. At the same time, the study has been carried out taking into account the shape of the voltage curve feeding the windings of the synchronous machine containing in addition to the fundamental harmonic the 8, 10, 11, 13, 14 and 16-th harmonic components, and the rated active power of the synchronous machine has been equal to 1 500 kW.

High voltage direct current transmission (HVDC) has been widely used in China in recent years due to its advantages of large transmission capacity, long distance, and low cost. It is significant to establish models for harmonic analysis in HVDC system. The switching function is used to get DC side harmonic voltage source, and the leakage inductance of transformer in both rectifier and inverter stations is equivalent to the DC side. A DC side harmonic equivalent calculation circuit for 6/12-pulse HVDC system is proposed accordingly. Using the simulation examples built in PSCAD/EMTDC, the correctness of the proposed model is verified.

In a three-level (NPC) converter, the voltage imbalance problem in the DC-link capacitors is major issue. This paper proposes the DC-link capacitor voltage imbalance compensation method, where a common offset voltage is injected for a multi-module NPC inverter. The offset voltage consists of a harmonic voltage and a voltage difference between the upper and lower capacitors. The proposed method does not require any hardware modification, so that it is easily implemented. In order to show the effectiveness of the proposed balancing method, theoretical analysis is provided to balance the voltages, and both the simulations and the experiments were carried out to show that the voltage difference of the DC-link was decreased by the proposed method.

This paper presents an assessment of voltage distortion, flicker and slow voltage variation caused by a distributed rooftop photovoltaic system in the low voltage distribution network at the campus of Universidad de El Salvador. Individual triplen harmonic voltage levels and longterm flicker index levels assessed in field measurements at the campus exceeded the compatibility levels established in most international power quality standards. The assessments also show a growing trend in all triplen harmonic voltage levels, short term flicker severity index and long-term flicker severity index levels, after the photovoltaic generation started operation.

The converter stations of different HVDC systems located in the adjacent networks, which have short electrical distance, forming a Multi-HVDC system. In the Multi-HVDC system, exists the harmonics interaction. This paper establishes the Multi-HVDC harmonic impedance model. The harmonic self-impedance, harmonic transfer impedance and harmonic transfer coefficient are defined to measure the influence of each harmonic current on the harmonic voltage of converter stations; giving the concept of harmonic voltage transfer amplification and transmission reduction. Taking Yin Chuandong Station and Lingzhou Station as examples, which belong to the Ning-Dong and Ning-Zhe Multi-HVDC systems. Calculate the harmonic self-impedance, harmonic transfer impedance and harmonic transfer coefficient of two converter stations. The results indicate that 3rd, 5th, 7th harmonics have greater impacts on the converter station. When the 5th harmonic current is injucted into the Ling Zhou Station, the harmonic voltage induced on Yin Chuandong Station is higher than that of in Lingzhou Station. After transmitted through the AC system, the effect of harmonic current on the remote converter station is increased, the voltage transfer amplification has occurred. All the results are verified by PSCAD simulation.

The oil-paper insulation of valve-side windings in a high voltage direct current (HVDC) converter transformer is subjected to both complicated voltage and severe thermal stresses. Partial discharge (PD) occurring in oil-paper bounded cavities is influenced by voltage stress type as well as temperature. This paper presents PD behaviors in an oil-paper bounded gas cavity under pulsating DC voltages. The voltage across the gas cavity and PD inception voltages at different test conditions are analyzed. Influences of temperature on statistical PD distributions and parameters are also presented. A numerical model is used to interpret PD behaviors under pulsating DC voltages and various temperatures. Experimental results and theoretical statements show that the temperature exhibits a great influence on the behaviors of cavity discharge under pulsating DC voltages. Volume resistivity, gas pressure, charge decay time constant, and electron generation rate are the primary parameters influencing PD behaviors at different temperatures.

The limitation of harmonic currents emitted by individual equipment and customer installations is essential in order to maintain harmonic voltages below compatibility or planning levels and consequently to ensure Electromagnetic Compatibility (EMC). At present, a large variety of methods exists worldwide for calculating harmonic emission limits, majorly expressed as harmonic currents. A systematic search on available methods has been performed for more than 70 countries from all over the world. Finally 16 individual methods for low voltage (LV), medium voltage (MV) and high voltage (HV) networks have been selected for a detailed quantitative comparison based on a probabilistic approach. This paper compares harmonic emission limits of the different methods for individual customer installation and is focused on generating installations. The first part provides details about the framework of comparison; the second part summarizes the results for the different voltage levels.

This paper presents the rules of harmonic penetration in Zhengzhou harmonic voltage level. National standards limit the harmonic voltage distortion level in the buses, so study the UHV AC/DC hybrid system is significant to power grid. In order to find out the harmonic voltage level near Zhengzhou converter station, a method has been proposed in this paper, including the models of radiation power grid, load characteristics and converter station's AC filter. Finally, according to Zhengzhou converter station power frame sets up a detail model in the simulation software packages PSCAD/EMTDC to study the law of harmonic penetration.

The purpose of the analysis of measurement results of harmonics presented in this paper is to predict the potential dangers after installation of capacitor banks in a medium-voltage (6 kV) network of the Kolubara open pit mine. Although the measured values for most of the harmonic voltages are lower than the maximum allowed values for medium-voltage networks, there is a risk of resonant occurrences of certain harmonics. It is shown that the resonant harmonic currents of the 11th to 25th orders can increase up to 10 times. These increases in harmonic currents could not overload network elements, but they could lead to overload and outage of the power capacitors. It is particularly important to note that the (quasi-) resonant phenomenon, which is common for harmonics between the 11th and the 25th order, is difficult to avoid without performing additional measures.

This paper uses data obtained from laboratory measurements of typical appliances such as Refrigerator, TV set to verify whether these non- linear loads behave similar to current harmonic sources or voltage-type harmonic sources. Inverter is used as input power supply. The output of inverter 230V is connected to Residential & Commercial Loads through a distribution transformer. Based on the measurements and additional simulations, and comparison from the tabular form it is stated that residential and commercial electronic loads behave essentially like harmonic voltage sources. This behavior helps to explain why shunt compensators and filters may even increase the harmonic current content in the feeder.

This paper deals with a new concept for calculating DC harmonic voltages and currents of line- commutated HVDC systems. In contrast to the conventional method, this method is useful for BTB (Back-To-Back) HVDC systems without smoothing reactors or PTP (Point-To-Point) with very short transmission line. This method proposes a new direction for HVDC system design and analysis. The proposed method is applied to a 50 Hz/60 Hz BTB test system and a synchronized BTB test system. After simulation and verification, the new results are introduced.

This paper studies the impact of different plug-in electric vehicles on network harmonic distortions, both at low frequencies and at high frequencies. Extensive measurements have been conducted in four different EVs (both regular passenger vehicles and electric buses), charged through different stations. Fast and slow, commercial and residential charging events were monitored. The collected set of measurements has shown that EV charging does have an impact on harmonic distortion levels. At low frequencies, harmonic voltages are below 4.0% and, therefore, EV impact is limited and unlikely to cause violations of harmonic distortion limits established in the Brazilian regulation (i.e., 10%). At high frequencies, voltage distortions of up to 1.0% of 60 Hz voltage were observed; however, the results are still preliminary and do not offer a reliable conclusion on whether such distortions have the potential to become a concern for utilities or not.

A methodology of diagnosing the winding insulation defect according to data of transient voltage and current from the impulse voltage test is put forward in this paper. Lightning impulse test for transformer is divided into half-wave and full-wave at the moment. According to the full voltage and reduced voltage at two pressure processes. The transient voltage and current from the impulse voltage test can be divided into Series of harmonics. The insulation defect is diagnosed by dividing impulse voltage and current into series of harmonic and structuring discriminant function according to the longitudinal ratio method and cross ratio method for the corresponding period of harmonic voltage and current. The methodology is also applicable to diagnose whether there are insulation damage in the windings those have passed the lightning impulse test.

International audience; To keep a high level of power quality, Distribution System Operators (DSOs) must keep harmonic voltage levels under limits specified in standards. These harmonic voltages are due to non-linear equipment connected inside installations, which inject harmonic currents into public networks. In order to apply emission limits per installation, DSOs need to have an accurate and reliable indicator to assess the harmonic emissions of an installation. In this paper, a comparative analysis of two definitions for assessing the harmonic emissions of installations is presented. Their respective advantages and drawbacks are pointed out.

Novel tunable distributed harmonic Voltage Controlled Oscillators (VCOs) are reported here for generation of 2nd or 3rd or both 2nd and 3rd harmonic frequency microwave/millimeter-wave signals, designed using Distributed Oscillator (DO) and achieved frequency tuning by body bias. The above generation of signals is become possible by the use of combination of innovative gain cell (i.e. amplifier), CPW lines and selection of the value of peaking inductor in the gain cells. The highest power output of the oscillator is at the third harmonic frequency of 41.84 GHz using low cost industrystandard 180nm CMOS which has a cut-off frequency of 50 GHz.

The main contents of this paper are the PQM system construction case and distribution system harmonic voltage analysis. The PQM system has constructed by KEPCO in order to investigate power quality of distribution power system for new power quality standard of KEPCO. In result, we have confirmed that voltage harmonic measurement value of the high voltage contract customer 8 households is suitable the KEPCO harmonic standard tentative plan. And the voltage harmonic value of distribution line end side is not always more high than source side by harmonic current offset effect. In the future, acquired data by season, region, load from the PQMS will be used on the resonable harmonic standard enactment in KEPCO.

A stator earth fault of a generator is the result of a lack of isolation between the stator winding of a generator and its iron core. In the last decades a number of different philosophies have been developed. With the latest experiences on the behaviour of the 3rd harmonic voltages of a generator the differences of applicable philosophies will be discussed and an approach to a sustainable solution will be outlined.

Characteristics of the current emission for new developed devices are changing resulting in lower low order harmonics and an increase in high order harmonics. For the low voltage network this results in an increase in high order harmonic voltages, violating more often the limits for the harmonic voltages at the 15th and 21th order harmonic. To improve this situation harmonic current could be reduced, network impedance could be decreased or the harmonic voltage limits could be increased. Since there are no complaints regarding these higher harmonic voltages, this paper presents an alternative approach to update these harmonic voltage limits.

Keywords: Harmonic; electronic instrument transformer; Harmonic error measurement system Abstract. A harmonic error measurement system which can simulate the actual operating conditions of electronic instrument transformer was established for electronic instrument transformer harmonic error measurement. The system consists of High-power current and voltage harmonic source which is used to output fundamental and harmonic signal, harmonic voltage and current standard device and harmonic analyzer. The results indicate that after superposing the fundamental and harmonic, ratio and phase error of electronic current transformer (ECT) becomes larger with increasing frequency; ratio error of electronic voltage transformer(EVT) increases with the increasing harmonics frequency, but EVT phase error changed to negative value at rated current, 150Hz frequency.

The basic function of electrical power system is to convert electrical energy from some universal form to electrical form, which may be consumed locally, or can be transmitted from one location to other. During power delivery and transmission, ideally frequency should be constant, but in real time applications, it is a variable notation. This variance sometimes makes the angular bus voltage differences erratic, rendering into irregular behaviour of a network. This paper deals with the estimation of change of harmonic voltage angles in a multi-bus network for fundamental, harmonic and symmetrical short circuit fault conditions of the network. The changes found have been analyzed and feature extraction has been done to identify the fault bus in the network.

This paper proposes a novel harmonic compensator for consumer electronic equipment that act as harmonic voltage sources in single-phase circuits, using the correlation function. The distribution transformer is equipped with an additional winding on the secondary side, and a single-phase voltage-source PWM inverter is connected to the added winding, acting as a shunt active filter. The leakage inductor on the secondary side winding behaves as though connected in series to the consumer electronic equipment. The shunt active filter can thus be used to compensate harmonic currents on the source side without an inductor series-connected to the harmonic voltage source. The basic principle of the proposed compensation method is discussed in detail. Digital computer simulation is implemented to verify the validity of the proposed compensation method. Experimental results demonstrate the novelty and excellent practicability of the proposed harmonic compensator with the proposed harmonic current detection method using the correlation function.

Summary Owing to increased capabilities of power quality monitors, synchronized harmonic phasor data are becoming more widely available. Taking advantage of the new data, this paper presents a new and effective method to solve the problem of how to estimate the harmonic impact of several individual loads on the harmonic voltages at a specific location of a power network. The method uses the independent fluctuation of the harmonic sources and is solved as a blind source separation problem. The proposed method has been verified through simulation verification where harmonic currents measured at actual substations are used as input so realistic load fluctuations are considered. Furthermore, lab experiments are conducted to validate the proposed method.

This paper discusses cause and effect of harmonic voltages and severe lighting equipment flicker that were observed by low voltage end consumers in connection with the operation of a pumping station connected to a 22 kV radial line of a typical MV distribution network of a Norwegian utility. The pumping station, consisting of three wound-rotor induction motors rated at 1.75 MW, 6.6 kV, forms part of a local medium-size hydro power scheme. The voltage disturbance is a 7.harmonic (and partly 5.harmonic) component fluctuating with a frequency of approximately 2 Hz, resulting in considerable flicker problems in lighting equipment at end customers, causing customer complaints.

Determination of harmonic emission levels is becoming a very important task in power distribution networks. Accurate measurements of harmonic voltages and currents are extremely important for correct evaluation of harmonic emissions. Voltages and currents in MV and HV networks are usually measured by the instrument transformers but the accuracy of these transformers for frequencies above their rated frequency is usually not known. The paper presents the behavior of the voltage and current instrument transformers at higher frequencies (above 50 Hz or 60 Hz). The harmonic magnitude and phase angle measurements errors are evaluated. At the end the impact of the measurements errors on the harmonic emission levels calculation is discussed.

Caused by the increasing use of dc power supplies based on rectifiers with capacitive smoothing, Fig. 1, the harmonic voltage levels are continuously rising in public mains systems. Remedial measur...

This paper considers the influence of grid modelling accuracy on grid impedance characteristic in PCC and therefore harmonic voltages. Influence of power system model components like: capacitor batteries, lines, stiff grid and generators was investigated. Location of these elements and its impact on results was evaluated. Results for the basic system configuration and alternative network configurations were compared. Simulations were carried out in PowerFactory Software.

The limits for harmonic currents injected into the public electric power supply system were prescribed in Japan in 1994. It is important to ascertain the effectiveness and sufficiency of these limits. Harmonic voltages at the same bus bars at several substations have been measured since 1994.

Harmonic voltage measurements have been carried out in MV- and LV-systems having different load mixture. The results are presented separately for systems supplying industrial, commercial and residential load as well as for systems with photovoltaic generation. The harmonic voltages mainly of the low order harmonics in some of the MVand LV-systems are extremely high, reaching almost the compatibility levels. Harmonics of higher order are considerably lower. The influence of photovoltaic generation is seen in an increase of harmonic voltages for all harmonics, whereas even for high order harmonics the voltage level is high. In industrial systems the harmonic voltage levels cover a wide range, even and odd order harmonics are present to a significant extend. The increase of system load in a LV-system indicated doubling of the harmonic voltage levels while the system load increased ten times. The results can be transferred to other systems having similar load mixture and short-circuit characteristic and can also be used to verify limits for the connection of additional electronic load and generation.

The authors report seven day measurements of harmonic current and voltage made at the sending out of five feeders. The comprehensive survey monitored voltage and current distortion at eleven locations: five distribution feeders, one large apartment building, three industrial customers, and two commercial. The major goals are to present different ways of recording and displaying harmonics, to explain the results, and to compare them with existing engineering recommendations. >

Effects of compact fluorescent lamps (CFLs) on the electric power network are analyzed. Measurements of electrical characteristics of eight CFLs are made during their switching and normal scheme operations. On the basis of measurement results a simulation model of a part of the electric power network was developed using the PSCAD simulation program. The model enables simulation of a detailed operation of CFLs with regard to other different loads. A comparison is made of the effects of replacement of the classic incandescent light bulbs with CFLs on the active and reactive power and harmonic voltages and currents (with regard to the EN 50160 specifications).

The paper intends to study the iron losses of non-oriented electrical steel laminations under sinusoidal, non-sinusoidal and PWM voltage supplies. The measurement of core losses of electrical steel laminations in Epstein frame is implemented step by step from 50 Hz to 400 Hz. The accuracy of results is verified by simulated modeling of the Ansoft EM software package. The core losses of non-oriented electrical steel laminations under sinusoidal, non-sinusoidal and PWM voltage excitations are compared in the paper. The analyzed results provide motor manufacturers with the important reference to minimize the core losses of the special motors under harmonic voltage supply.

This paper investigates the impact on the harmonic levels of changes in television viewing patterns in Australia. Harmonic levels during special sporting events which attracted large television viewing audiences were recorded at several sites and compared to levels at other times. The enormous increase in television audience levels (compared to typical levels at that time of the night) during the 2006 World Cup soccer match resulted in a modest increase in harmonic voltage levels. The surprisingly low impact may be attributable to the number of television receivers which are continually in operation or standby mode. No conclusive trends were observed in harmonic voltages during the 2004, 2005 and 2006 Melbourne cup races. There was a reduction in harmonic voltages at one site during 2004 and 2005 races. However this trend was not repeated in 2006. The influence of network capacitors on harmonic levels was considered. Lessons learned from these observations could potentially improve our understanding of the impact of customer equipment and customer behaviour on harmonic levels and assist in managing waveform distortion now and in the future.

A device compensator able to help in improving the daily operation of an electric network by means of the sags and swells mitigation, as well as the correction of harmonic voltages is proposed. The device has been implemented in a laboratory prototype, where the control is carried out through a DSP. The preliminary results are promising and a bigger prototype is under construction.

Through the analysis and measurements of power quality on distribution line of 10 kV and 0.38 kV, it was approved that harmonic voltage and harmonic current can be generated while the steelworks was running. Because of harmonic affect, the capacitive voltage-rise was taken place, the longer of the transmission line the higher of the capacitive voltage-rise, meanwhile, a lot of electric equipments were damaged

The surge arrester is an important piece of overvoltage protection equipment in substations, and the latent faults of MOA can be found by on-line resistive leakage current monitoring. It is reasonable to adopt the resistive leakage current's first component i/sub r/ and third component i/sub 3r/ as the metal oxide surge arrester's indicators. These indicators can find the aging phenomenon of the metal oxide surge arrester in time. But the existence of harmonic voltages in the power system will influence the indicators' accuracy. In this work, this influence is analyzed and an improved compensation method to separate the resistive leakage current under the existence of harmonic voltage is described. Finally, according to these methods, an on-line resistive current MOA monitoring system based on a bus-module is developed.

The connection of medium-frequency converters applied for melting ovens to medium-voltage systems are investigated in this paper. The influence on the voltage quality, especially on harmonics needs special attention in this case. Measurements of harmonic currents and voltages for a time period of one week, determined by the characteristic of the load were carried out. It was recognized, that the harmonic voltage level depends significantly on the configuration of the feeding power system as well. This is due to the fact that parallel and serial resonances exist in the power system with resonance frequencies typically close to significant harmonics. Taking account of the worst conditions, the MF-converters cannot be operated without violating the emission limits and/or the compatibility levels defined in international standards. Solutions were investigated and applied which allowed the operation of the converter ovens without any additional equipment to be installed.

The region „Unterengadin“ is situated in the southeast of Switzerland in the middle of the Alps. The regional distribution networks are fed from the 380kV substation „Pradella“ which is connected via a 380 kV overhead line to Sils and the Swiss as well as the European EHV transmission grids. In the year 1991 the EHV transmission grid has been extended with a double circuit overhead line from „Pradella“ to „Westtirol“ in Austria (FIG. 1).

A monitor system is presented in this paper which is used to measure the harmonic voltages and currents of a three-phase source in a power network. In accordance with the principles of harmonic measurement of digital sampling, this system does synchronous sampling for three voltage signals and three current signals analyzing the harmonics. A synchronous sampling impulse circuit is added in hardware to reduce errors caused by leakage effects, and a quasisynchronous sampling algorithm is used in software design. To reduce errors further, the system can monitor and analyze the fundamental wave and harmonics up to the 50/sup th/ order in real-time.

Surge arresters are important over voltage protection equipment in a substation. It is necessary to monitor the resistive leakage current of MOAs (metal oxide surge arresters) on line so that we can prevent faults from developing in time to avoid economic loss. It is reasonable to adopt the resistive leakage currents basic component, i/sub r/, and thrice component, i/sub 3r/, as metal oxide surge arrester indicators. These indicators can detect the aging phenomenon of a metal oxide surge arrester in time. However, the existence of harmonic voltages in the power system influences the indicator accuracy. We analyze this effect and put forward an improved compensation method to separate the resistive leakage current under the existence of harmonic voltage. Finally, according to these methods, we develop an on-line MOA resistive current monitoring system based on the bus-module.

This paper presents a new method for predicting the net harmonic currents produced by a large number of residential PV inverters. The simple experimental based models of a PV inverter, which have been installed at the Sydney Olympic Village, are described. The effect of background harmonic voltages, input current from PV arrays and also randomness in individual inverter's harmonic performances are taken into account. The model allows for harmonic cancellation due to diversity of magnitudes and phase angles. The study includes the harmonic measurement, data analysis, statistical analysis, mathematical modeling technique and simulations. The results of measurement from the Sydney Olympic Village and UNSW laboratory are compared to the simulation to confirm the accuracy of the models. Those results also show that harmonic voltages at the Olympic Village are far below both the IEEE 519-1992 and Australian Standard limits even after the operation of all PV inverter systems in the solar village (1.9%), and ready for the Sydney 2000 Olympic Games.