Effective flicker reduction and grid code compliance in a steel plant

Challenges at the customer’s steel plant

Our customer’s steel plant in Poland has an EAF with a rating of 60 MVA and an LF with a rating of 13 MVA. The customer was experiencing rapid fluctuations in reactive power due to these high-power loads. It is common for such loads to induce voltage instability when connected to the grid. The fluctuation in reactive power and voltage is primarily caused by the dynamic operation of the EAF, which has a significant impact on power quality compared to the LF, which has a smaller rating and operates more steadily. Nevertheless, both the EAF and LF generate harmonic currents that result in harmonic voltages when flowing through the system impedances.

Our Merus^® Solution

For the customer to be able to operate the steel plant effectively, Merus Power delivered a 3 MVAr (ind) to 53 MVAr (cap) Static Synchronous Compensator (STATCOM) solution. Merus Power was responsible for the complete delivery of the Merus^® STATCOM system as a project. The total compensation of 53 MVAr was divided between active compensation and fixed compensation. 28 MVAr of active compensation was provided by 14 pcs of Merus^® M2000 STATCOM modules, whereas the remaining 25 MVAr were from a second fixed filter capacitor bank that was already installed on the site. The installed Merus^® STATCOM solution can control reactive power seamlessly and in real-time between 3 MVAr (inductive) and 53 MVAr (capacitive) for an undefined period. Short-time overloading allows compensation capacity between 15 MVAr (inductive) and 65 MVAr (capacitive).

Results after installation

The real-time response of Merus^® STATCOM met the dynamic reactive power demand created by the EAF operation efficiently and reduced the voltage flicker significantly.

Post-commissioning performance measurements showed that the reactive power 95-percentile value measured from the PCC was only 13.14 MVAr. It was also measured from the PCC that the maximum value for the short-term flicker is 0.946 p.u., the voltage unbalance 95-percentile value is 0.231 % and the largest THD 95-percentile value is 0.63 %, which are well within the limits of IEC 61000-4-30, IEC 61000-2-12, and IEC 61000-3-6 power quality standards.

The lower reactive power demand, excellent flicker, harmonics mitigation, and overall power quality improvement result in increased productivity, reduced losses, and reduced electrode consumption. These are achieved by improved arc stability of the EAF process.