A simple and low-cost control strategy for active power filters implemented with pulsewidth modulation voltage-source inverters (PWM-VSIs) connected in cascade is presented and analyzed in this paper. The principal component of the control circuit is an INTEL 8031 AH microcontroller, which generates the current reference waveforms and respective switching patterns for each inverter. The switching pattern is obtained by using a vector control technique. The proposed active power filter consists of two PWM-VSIs, connected in cascade, each operating at a different switching frequency. This paper presents the proposed control strategy in terms of principles of operation, circuit design and implementation. Finally, predicted results are verified experimentally on a 10 kVA breadboard model.

A simple and low-cost control strategy for active power filters connected in cascade

An active power filter connected in series to the power distribution system is presented and analyzed in this paper. The series active power filter is implemented with a PWM voltage-source inverter and operates in conjunction with a resonant LC filter connected in parallel to the power lines and is able to compensate current harmonics and the fundamental negative and zero sequence voltage components generated by nonlinear unbalanced loads. The proposed series active power filter also compensates zero sequence current harmonic components that flow through the neutral conductor. In particular, the active power filter is discussed in terms of the principles of operations under steady-state and transient operating conditions. The design of the power and control circuits are reported. >

A series active power filter which compensates current harmonics and voltage unbalance simultaneously

This paper presents the results for the performance of passive and active power filter to reduce harmonics in the distribution system. The harmonics analysis is performed in order to observe the percentage reduction of amplitude current harmonics and total harmonic distortion for passive and active power filter at various loads. In addition to that the bidirectional switching is used as a strategy control in active power filter. Representative result of circuit simulations is carried out. The results show that the active power filter can simultaneously attenuate various frequencies and are compared with passive filter which is only filtering an individual harmonics. Also, the significant percentage of reduction for the amplitude current harmonics and total harmonic distortion by active power filter are compared to passive filter. Furthermore, the sinusoidal current waveform quality at distribution lines which filtered by active power filter is better compared with passive filter. Therefore, the active power filter is good to reduce harmonics in the electrical distribution systems.

Performance for passive and active power filter in reducing harmonics in the distribution system

A novel strategy for shunt active filter control

The current and voltage harmonic spectrum, and power factor in gas discharge lamps: sodium (Na)-high pressure and mercury (Hg) in actual use in public street lighting have been measured. A sample of nearly 360 gas discharge lamps (Na, Hg) of different rated power was obtained by simple random sampling over a universe of approximately 15000 lamps. An "equivalent" current harmonic spectrum for gas discharge lamps is proposed, which is independent of the type of gas and the lamp rated power. This current spectrum can be used to integrate gas discharge lamp models for harmonic distortion level assessment in distribution networks. The relation of this equivalent current harmonic spectrum with: (i) lamp voltage waveform, (ii) type of lamp (Na, Hg), and (iii) power factor-capacitor lamp, is analyzed.

Harmonic distortion and power factor assessment in city street gas discharge lamps

This paper contains a discussion of several energy saving technologies and their impact on electric power distribution systems. The reduced power demand of these energy saving devices reduces the peak system demand. However, there are increased distribution transformer and distribution network losses due to the distorted load current waveshape. These losses, when integrated over many services and over the year, represent a significant cost due to fuel costs and higher peak. The main focus of the discussion relates to ASD heat pumps and electronic ballast fluorescent lighting. >

G.T. Heydt

Papers

The impact of energy saving technologies on electric distribution system power quality