Abstract : This paper addresses the inquiry of a user located in an industrial development zone who requested to increase the power of their 1250kW frequency converter to 2500kW. Following this inquiry, tests were conducted on the user's current and post-upgrade power supply to understand the magnitude and impact of harmonics injected into the power grid, thereby determining the feasibility of supplying power to them. Keywords : Power supply scheme, frequency converter, user, capacity expansion project Introduction Harmonic sources in power systems are diverse, primarily originating from synchronous generators and transformers, high-power controllable rectifiers, and other nonlinear electrical equipment. Harmonics can have many adverse effects on equipment operation, such as increasing equipment losses, raising temperature rise, reducing equipment output and lifespan, increasing dielectric losses and partial discharge in insulation, accelerating insulation aging, and increasing motor vibration and noise. The company's power supply business rules clearly stipulate that the sinusoidal distortion rate of the grid's point of common coupling voltage and the harmonic current injected into the grid by the customer should comply with the provisions of GB/T 14549-93 for harmonics in public power grids. For customers with nonlinear equipment connected to the power grid, the following regulations should be met: 1) When installing or changing power, customers with the following electrical equipment should provide the company with harmonic source parameters: converter and rectifier devices, including rectifier devices for electrified railways and trams, charging equipment for power batteries, etc.; rolling mills, induction furnaces and electric arc furnaces in the metallurgical sector; electrolytic cells and electrolytic chemical equipment; large-capacity electric arc welding machines; and nonlinear loads of other large-capacity impact equipment. 2) When providing power supply solutions to the above-mentioned customers, the company will propose the limit value (maximum value) of harmonic current allowed to flow into the power grid according to national standards. 3) The above-mentioned customers should calculate the harmonic current value flowing into the power grid during the design phase. If a certain harmonic current exceeds the standard, a corresponding filter device should be installed; if a certain harmonic current may exceed the standard, the design should consider reserving space and costs for installing harmonic elimination devices, in case the actual measured value exceeds the standard after commissioning. [b][align=center]For details, please click: Determining the Power Supply Scheme for Capacity Expansion Projects for Users Using Frequency Converters[/align][/b]