Point Of Common Connection Research Articles

MATLAB/Simulink-based modelling and analysis of a grid connected wind energy conversion

The paper presents the dynamic modelling and simulation of a grid connected variable speed wind generating system, using MATLAB/Simulink in power system block-set. The wind generating system with direct drive generator and power electronics interface is modelled for dynamic analysis. Using the instantaneous reactive power theory, controller controls the inverter. The hysteresis current controlled of inverter has been implemented, to capture the maximum energy from varying wind speed and maintaining the unity power factor at the point of common connection (PCC) on the grid. Thus, the power system will enhance the power quality norms at PCC. The simulated studies provide control performance and dynamic behaviours of grid connected wind energy conversion system. The system model and control scheme evaluates the performance on the power grid so as to maintain the power quality norms according to the IEC 61400-21 Standard at PCC.

An Active Power Filter with Direct Current Control for Power Quality Conditioning

Fast dynamic response and high-frequency switching make the active power filter an appropriate converter to implement the correction of low-power quality events and impose a sinusoidal current in the grid at the point of common connection. In this article, a new simple and robust control structure for an active power filter is designed, simulated, and tested. The current loop, based on the DC bus energy balance, is intuitive, robust, simple to implement, and allows a fast dynamic response. The implementation is validated with simulated and experimental results obtained in a three-phase 5-kVA prototype.

Shunt active power filter implementation for induction heating applications

PurposeThis paper aims to present the prototype of a 140 kVA shunt active power filter (APF) for current harmonics and fundamental reactive power compensation of a 200 kW induction heating system.Design/methodology/approachDesign issues of the power components, of the switching ripple filter and of the digital control are addressed and discussed. The APF control algorithm has been implemented on the 16‐bit, fixed‐point, TMS320LF2407 A DSP controller. The current control is based on proportional‐sinusoidal signal integrators with good performance in current harmonic elimination and power factor compensation.FindingsThe experimental tests, performed in real industrial environment for a 200 kW induction heating plant, show that the performance goals are fulfilled.Practical implicationsThe sinusoidal signal integrators (for consistency with the other plural forms of acronyms) of the current controller are implemented in the rotating reference frame aligned with the voltage vector at the point of common connection. This allows the compensation of two harmonics with a single SSI, thus halving the computational effort of the DSP.Originality/valueIn industrial induction heating, the need for harmonic and reactive power compensation lasts a few seconds per minute, making passive solutions not suitable. The presented APF is a valid solution for this application, where only a few tailored implementations are available on the market.

Unified power quality conditioner with super‐capacitor for energy storage

AbstractThis paper proposes a new configuration of UPQC (Unified Power Quality Conditioner) that consists of the DC/DC converter and the super‐capacitors for compensating the voltage interruption. The proposed UPQC can compensate the reactive power, harmonic current, voltage sag and swell, voltage unbalance, and the voltage interruption. The performance of proposed system was analyzed through simulations with PSCAD/EMTDC software, and the realization of proposed system was verified through experimental works with a prototype. The proposed system can improve the power quality at the common connection point of the non‐linear load and the sensitive load. Copyright © 2007 John Wiley & Sons, Ltd.

The p-q theory for active filter control: some problems and solutions

The instantaneous active and reactive power theory or the p-q Theory is widely used to design controllers for active filters. This paper deals with some problems due to the misinterpretations of this theory. A historical background of the theory is presented and the problem caused by distorted voltages at the point of common connection (PCC) is analyzed. In addition, the appearance of source current harmonic component not present in the load current (hidden current) caused by different filtering characteristics for the calculation of the oscillating real and imaginary power components is discussed. The problem caused by the voltage distortion can be solved using a phase locked loop (PLL) circuit. For the hidden current, filters with similar characteristics can avoid them. These analysis and solutions are presented to clarify some aspects of the p-q Theory not clear in the original approach of the theory.

Reduction of harmonic currents generated by discharge lamp systems

The paper presents a novel scheme for minimising harmonic currents generated by 3-phase systems of discharge lamps. The main idea is to install in the neutral conductor a filter with characteristics which allows the first harmonic component to flow with minimum attenuation while higher harmonic components of the neutral current are attenuated. For filter design, a 3-phase system of fluorescent lamps is substituted by a Thevenin equivalent seen from the common point of a lamp connection and the ground point of the supply system. It leads to nonlinear Thevenin equivalents when an internal impedance and an equivalent voltage are dependent on the current flowing in the neutral conductor. The equivalent circuits developed are subsequently used for filter design and simulation. Rosenbrock's optimisation procedure is implemented to compute filter parameters. The assumed objective function aims at the small impedance for the first harmonic to allow asymmetrical current flow and large impedance for higher harmonics to reduce harmonic distortion in the supply and neutral currents. The equivalent models developed are applied for simulation of filter working conditions in the neutral conductors. Simulations are verified by laboratory tests, showing good agreement.