# Impacts of Grid Voltage Harmonics Amplitude and Phase Angle Values on Power Converters in Distribution Networks

ABSTRACT:

Power Converters Motor drive systems based on diode-rectifier are utilised in many industrial and commercial applications due to their cost-effectiveness and simple topology. However, these diode rectifier-based systems can be affected by power quality and harmonics in distribution networks. Thus, this paper investigates the impact of grid voltage harmonics on the operation of power converters with three-phase diode rectifier using mathematical formulation of the drive voltage and current harmonics based on grid voltage harmonics. Simulation analysis and practical tests have been then carried out to validate the mathematical equations and the impact of grid voltage harmonics on the power converter harmonics.

INDUCTOR

The results illustrate that even a small amount of grid voltage harmonics (around 4%) could significantly impact the input current harmonic contents of the three-phase diode rectifier. It is also shown that the phase-angle of grid voltage harmonics plays a crucial role to improve or deteriorate the input current harmonics of the power converters. In the next step, the optimum condition of grid voltage harmonics to minimise the input current harmonics has been evaluated and verified based on different grid codes. Finally, a harmonic mitigation technique in multi-drive systems using Electronic Inductor is proposed to mitigate the current harmonics at the PCC.

KEYWORDS:

1. Distorted grid
2. Distribution networks
3. Total harmonic distortion
4. Three-phase rectifier,
5. Voltage harmonics

CIRCUIT DIAGRAM:

Figure 1. Simulink Model For The Tested Asd Under The Presence Of Voltage Harmonics At The Pcc.

EXPECTED SIMULATION RESULTS:

Figure 2. Simulation Results Of The Three-Phase Input Currents And Vrec In Case: (A) 1, (B) 2, And (C) 3.

Figure 3. Practical Measurements Of The Three-Phase Input Currents And Vrec In Cases: (A) 1, (B) 2, And (C) 3.

Figure 4. Simulation Results Of The Three-Phase Input Currents And Vrec In Cases: (A) Ieee-Min, (B) Ieee-Max.

Figure 5. Practical Measurements Of The Three-Phase Input Currents And Vrec In Cases: (A) Ieee-Min, (B) Ieee-Max.

Figure 6. Simulation Results For Phase “A” Current When U1 Mitigates Harmonics Generated By U2: (A) Case 3, (B) Ieee-Max Case.

Figure 7. Simulation Results For Output Voltage (Vo), Inductor Current, And Phase “A” Inverter Side Current Of U1.

CONCLUSION:

In this paper, the impact of grid voltage distortion on power converter current harmonics emission has been investigated. For that aim, ASDs with conventional diode rectifier has been considered to represent the power electronic system. A mathematical formulation of the rectified voltage, inductor current, and input currents of a three-phase diode rectifier is derived under the presence of voltage harmonics at the PCC. Different cases of voltage harmonics are then considered in the analysis to investigate the behaviour of the rectified voltage and the input current harmonics. The results show that the presence of even a small level of voltage harmonics (4%) at the PCC can change the current THDi by up to 30%. Furthermore, it has been shown that the phase-angle of the voltage harmonics can have a significant impact on the input current harmonics.

THD

Depending on the voltage harmonic phase-angle, the same amount of voltage harmonics could improve or deteriorate the rectified voltage ripple and the input current THDi. Moreover, the voltage harmonic phase-angle could create a phase delay (1) in the diodes conduction time. A positive 1 impacts the displacement power factor negatively, whereas a negative 1 improves that factor. Finally, a harmonic mitigation technique to compensate the high level of current harmonics using Electronic Inductor (EI) is presented.

REFERENCES:

 B. K. Bose, “Power electronics and motor drives recent progress and perspective,” IEEE Trans. Ind. Electron., vol. 56, no. 2, pp. 581_588, Feb. 2009.

 B. K. Bose, “Energy, environment, and advances in power electronics,” IEEE Trans. Power Electron., vol. 15, no. 4, pp. 688_701, Jul. 2000.

 W. Gray and F. Haydock, “Industrial power quality considerations when installing adjustable speed drive systems,” in Proc. IEEE Cement Ind. Tech. Conf. XXXVII Conf. Rec., San Juan, PR, USA, Jun. 1995, pp. 17_33.

 P. Waide and C. U. Brunner, “Energy-ef_ciency policy opportunities for electric motor-driven systems,” Int. Energy Agency, Paris, France, Work. Paper, 2011, pp. 1_128.

 B. Singh, B. N. Singh, A. Chandra, K. Al-Haddad, A. Pandey, and D. P. Kothari, “A review of three-phase improved power quality AC-DC converters,” IEEE Trans. Ind. Electron., vol. 51, no. 3, pp. 641_660, Jun. 2004.