Variable frequency power supply is a device that uses frequency conversion technology and microelectronics technology to control the power transmission of AC motors by changing the frequency and amplitude of the motor's working power supply. It is widely used in power systems. It includes single-phase variable frequency power supply, three-phase variable frequency power supply, etc. Variable frequency power supply belongs to a type of electronic device device, which not only has strict restrictions on the installation environment, but also may have an impact on surrounding equipment during the use of variable frequency power supply and single-phase variable frequency power supply. Therefore, it is necessary toPower quality monitoringIt is meaningful to sort out the possible impacts and study solutions.
Modern production and life cannot do without electricity. The power sector not only needs to meet the growing demand for electricity from users, but also needs to meet the requirements for power quality. Like other products, electric energy also has quality advantages and disadvantages. The power quality mainly includes the following contents:

1. Frequency. The rated frequency of AC power in China's power grid is 50Hz, which is consistent with the regulations of most countries in the world, and there are also some countries that use 60Hz as the power grid frequency.

2. Voltage. The national standard GB156-93 "Standard Voltage" specifies the nominal voltage of the power system, the rated voltage of electrical equipment, and the voltage of electrical equipment.

3. Waveform. The waveform of alternating current in the power system should be a sine wave.

4. For three-phase systems, three-phase symmetry is also required.

The high order harmonics of variable frequency power supplies are one of the possible impacts that variable frequency power supplies may have on power quality monitoring. At present, almost all variable frequency power supplies adopt PWM control method. This pulse modulation form causes high-frequency harmonic currents on the side of the power supply during operation, and causes voltage waveform distortion. This change in voltage waveform will have a significant impact on the power supply system of other equipment.