The impact of frequency converters on power grids and measures to suppress harmonics are a complex and important topic. The following will elaborate on the impact of frequency converters on power grids, the source of harmonics, the specific impact of harmonics on power grids, and measures to suppress harmonics.
Frequency converters are mainly used to adjust the speed of AC motors, and have the advantages of wide speed regulation range, high precision, and good dynamic response. However, frequency converters will have certain impacts on the power grid during operation, the most important of which is harmonic pollution. Since the frequency converter contains rectifier circuits and inverter circuits, these nonlinear devices will cause the voltage and current waveforms in the power grid to be distorted, thereby generating harmonics.
The source of harmonics lies in the rectification and inversion process inside the frequency converter. In the rectification link, the frequency converter converts AC power into DC power, and a large number of harmonics will be generated in this process. In the inverter link, DC power is converted into AC power to drive the motor, which will also generate harmonics. These harmonics will be injected into the power grid and affect the quality of the power grid.
Deterioration of power grid quality: Harmonics will cause waveform distortion of power grid voltage and current, reducing the power supply quality of the power grid.
Increase grid loss: When harmonic current flows in the grid, it will generate additional losses and increase the energy consumption of the grid.
Shorten the life of electrical equipment: Harmonics can cause heating, vibration and noise in electrical equipment, accelerating the aging and damage of equipment.
Interference with communication system: Harmonics may also interfere with nearby communication systems through electromagnetic radiation, reducing the transmission quality of signals.
Use isolation transformer: Installing an isolation transformer between the frequency converter and the grid can reduce the electrical interference of the frequency converter to the grid.
Install filter: Installing a filter at the input or output of the frequency converter can effectively filter out harmonics. Passive filters have the advantages of simple structure and low cost, but the filtering effect may be affected by system parameters. Active filters are highly controllable and fast responsive, and can automatically track and compensate for changing harmonics.
Use multiplexing technology: Using multiplexing technology in the rectification link, such as 12-pulse, 18-pulse or 24-pulse rectification, can reduce harmonic components. At the same time, the parallel diversification of inverter units and the series diversification of power units are also effective harmonic suppression methods.
Increase the cross-sectional area of the cable: Increasing the cross-sectional area of the cable can reduce the loop impedance, thereby reducing the impact of harmonic current on the power grid.
Choose a suitable frequency converter: When choosing a frequency converter, priority should be given to products with low harmonic content and little impact on the power grid. For example, a green frequency converter should have quality standards such as both input and output currents are sinusoidal and the input power factor is controllable.
In practical applications, it is necessary to select appropriate harmonic suppression measures according to specific circumstances. For example, in a workshop where frequency converters are relatively concentrated, centralized rectification and DC common bus power supply can be used to reduce the generation of harmonics. At the same time, a variety of harmonic suppression methods can be combined to achieve the best harmonic suppression effect.
After implementing harmonic suppression measures, it is necessary to regularly detect and evaluate the harmonic content of the power grid. This helps to understand the effect of harmonic suppression measures and adjust and optimize them according to actual conditions.
The impact of frequency converters on the power grid is mainly reflected in harmonic pollution. In order to suppress the impact of harmonics on the power grid, a variety of measures can be taken, including the use of isolation transformers, the installation of filters, and the use of multiplexing technology. In practical applications, it is necessary to select appropriate harmonic suppression methods according to specific circumstances, and regularly detect and evaluate the harmonic content of the power grid. Through the implementation of these measures, the harmonic pollution of the frequency converter to the power grid can be effectively reduced, and the power supply quality and stability of the power grid can be improved.
