Power Quality Assessment & Mitigation in Distribution System (A Case Study at Adama Spinning Factory)

Abstract

Investigation and monitoring of power quality is necessary to maintain accurate operation of sensitive equipment in an industrial environment. This paper presents the assessment and mitigation of power quality problem in Adama Spinning Factory. Monitoring of voltage and current harmonic distortion levels up to the 11th order on the four distribution transformers of the factory’s electrical network is carried out using DELAB NV8s PFC measuring equipment. Even though this equipment is primarily intended for automatic power factor controlling using 3-phase capacitor banks, they also have a capability to measure %THD and individual harmonic distortion up to 11th order for voltage and current. The measured voltage and current harmonic distortion levels are compared with the IEEE 519-2014 and IEC 61000-2-2 / -3-4 international standards. The harmonic voltage distortion level in the factory has found to be well under the limits set by these standards while the current harmonic distortion levels on three of the transformers exceeds the standard limits with a maximum %THDI value of up to 43.8%. Moreover, the power factor level of the factory on the utility meter found to be below 0.9, the minimum limit not to be penalized by the utility. For mitigating the current harmonic distortion level in the factory a Distribution Static Synchronous Compensator (DSTATCOM) in current control mode is proposed. DSTATCOM is a shunt connected device, designed to inject unbalanced and harmonically distorted current to distribution line to eliminate unbalance or distortions in the load current. Instantaneous reactive power (IRP) based control theory is used to generate the reference currents. The distribution network of the factory is modeled in MATLAB’s SIMULINK environment by considering the distribution transformer impedances, the power factor capacitor banks and the linear RL load. The non-linear loads are modeled as ideal harmonic current sources of 3rd to 11th order harmonics with amplitude of the maximum measured harmonic amplitude. The performance of the proposed DSTATCOM is evaluated by simulating the distribution network with and without DSTATCOM. The simulation results show that the source current becomes pure sinusoidal and in-phase with the source voltage within 0.02 seconds (one cycle) after the introduction of the DSTATCOM in the system.