August 14th

Small hydroelectric power plants in China

Driving rural development

Hydroelectric generation in China is not limited only to huge scale projects. In recent years, the country has become one of the most successful adopters of small hydroelectric facilities (plants up to 25 MW) as a means of achieving carbon emission free rural development.

The total installed capacity of small hydroelectric plants in China is estimated at approximately 50,000 MW and growing at about 6,000 MW annually.

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August 12th

Voltage Quality Improvement in Distribution Networks

This paper is presented by Chilectra, a subsidiary of the Endesa Group Spain and the biggest electric utility in Chile. It sets out a methodology for estimating and determining control parameters for the voltage quality to be delivered to its end customers.

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August 5th

Switching Power Supplies: Analysis of Waveform Distortion and Absorbed Powers

Analyses to have a quantitative idea of the real behavior of Switching Power Supply (SPS) units from the point of view of waveform distortion and power absorption are developed. Results of several experimental tests performed by means of a test system built up at Laboratories of the Second University of Naples (Italy) are firstly reported.

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August 4th

Voltage Collapse Proximity Indicators for Radial Distribution Networks

Based on the single-line equivalent system of a radial distribution network, two simple methods to evaluate two efficient voltage collapse proximity indicators are presented and discussed. The two methods differ on the determination of the parameters which define the equivalent system from which the indicators are derived.

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Application of DSTATCOM compensators for mitigation of power quality disturbances in low voltage grid with distributed generation

The paper presents capabilities of DSTATCOM systems used to improve power quality (PQ) in low voltage (LV) grids with distributed energy resources (DERs). For the case study a typical rural network has been selected in which, on one hand DER installing is the most probable and on the other hand, integration process may cause the biggest problems. Selected single-phase DERs of varying power are connected into the network which introduce PQ disturbances such as voltage variations, harmonics and asymmetry.

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The Load Flow Calculation in Harmonic Polluted Radial Electric Networks with Distributed Generation

Analyse of harmonic distortion in power systems consists in the determination of steady state quantities for each harmonic component at a time. The existing theoretical relationships are difficult to be implemented in complex systems containing many elements, in various combinations. In the case of radial power systems operated in sinusoidal conditions, the load flow calculation can be performed using a particular method known as the backward/forward sweep.

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Damped-Type Double Tuned Filters Design for HVDC Systems

The ac/dc filters are always needed in HVDC converter stations to suppress harmonic currents/voltages. The ac side filters are also employed to compensate network requested reactive power. Among different types of filters, double tuned passive filters have been widely utilized in HVDC stations, yet these filters are still not considered well developed. This paper presents an algorithm for design of the conventional and damped-type double tuned filters to reduce harmonic distortion and improve power factor in electrical systems.

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Search for Network Parameters Preventing Ferroresonance Occurrence

Application of the continuation and bifurcation method for studying the influence of network parameter values (e.g. source voltage, network capacitance or damping resistance loading the broken delta of voltage transformers (VT) tertiary windings) on network stability is described in the article. It is possible to estimate in this way sensitivity of the network to ferroresonance occurrence after a fault such as breaker switching or ground short-circuit. The advantages and limitations of the method are given.

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An experimental evaulation of short-time flicker index

A waveform generator capable of supplying an interharmonically distorted voltage supply was constructed and used to evaluate the human perception of light flicker. The light flicker index (Pst), as defined in IEC guidelines [1] is a measure of perceived light flicker. Comparisons were made of light flicker experienced to corresponding values of Pst measured. Results show that the Pst value of 1 is a good indicator of unacceptable flicker. Interharmonic magnitudes of 0.2% or more are also seen to lead to light flicker complaints.Read full article

July 31st

Connecting Distributed Generation (DG) units to the network

By David Chapman & Bruno De Wachter

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