Development of AC Regulated Power Supply Using Instantaneous Comparison Method
Precision electronic instruments and equipment are widely used in household, industrial production, office automation, experimental research, communication engineering, medical and other fields, and are generally powered by urban power grids. The rated voltage of urban power grid is single-phase 220V, which is the ideal voltage specified by humans. Due to the initial voltage of the power supply line from the transformer being (220+10%) V and the final voltage being (220-10%) V, electrical equipment is required to have a certain ability to withstand voltage fluctuations in the power grid. Although most electrical equipment has the ability to withstand power supply voltage fluctuations, according to statistics, power supply voltage fluctuations are one of the causes of electrical equipment failures. Therefore, these electrical equipment need to use a regulated power supply to ensure their normal operation.
Voltage stabilizing power supply is a device that stabilizes the voltage of the power grid. It has been used in China for many years, such as sliding contact type, variable reactor type, magnetic saturation type automatic voltage stabilizing power supply driven by servo motor and regulating transformer.
The above voltage stabilizing power supplies are based on sampling the grid voltage, comparing and adjusting it using servo motors or contactless switches to ensure stable output of AC voltage. This type of regulated power supply generally has poor voltage stabilization effect, with an accuracy of 1%~0.5%.
The current AC stabilized power supply mainly has the following problems:
(1) The use of nonlinear reactors often brings harmonics, which does not improve the quality of the voltage waveform in the power grid. Some even have additional waveform distortion, causing harmonic pollution to the power grid.
(2) The sampling time and execution mechanism action time are too long.
These two steps have a significant impact on the performance of the voltage regulator, and the sampling method generally uses effective value or average value sampling, which requires at least several cycles; The servo motor usually takes several seconds to tens of seconds to perform adjustment actions, which is too long and does not improve the voltage waveform. These voltage stabilization methods do not have enough time to respond to and execute disturbances such as surges, dips, pulse interference, and high-frequency interference in the rapidly changing voltage of the power grid, causing interference to pass through the voltage stabilization device and reach the electrical equipment, which cannot provide protection for the electrical equipment and may even cause the electrical equipment to malfunction or be damaged.
