The application of SVG static reactive power generator in charging stations

With the increasing scarcity of fossil energy, the proportion of power clean energy in society is gradually increasing, and the application of reactive power compensation devices has been vigorously promoted. The development of reactive power compensation devices has mainly gone through three stages: switching capacitors, static var compensators (SVC), and static var generators (SVG). With the development of high-power switching devices and the advancement of control technology, more efficient SVGs have gradually gained popularity among users.

SVG Working Principle:
Since the sum of the power in a three-phase circuit is constant, the total power of the three-phase circuit at any given moment is equal to the sum of the active power and reactive power of the three-phase circuit. The reactive power in the three-phase circuit circulates among the three phases, which is equivalent to there being no reactive power transfer between the load and the power source of the three-phase circuit. SVG precisely handles each part of the three-phase circuit uniformly.

The ideal SVG is a purely resistive load. It controls the number and mode of each phase reactor connected to the grid by controlling the on-off of the switching devices. This function is similar to a three-phase bridge rectifier circuit, except that the DC side of the SVG is an ideal passive load.

When reactive power of the fundamental wave is compensated, the voltage control of the SVG switching devices and the DC side load is achieved by controlling the switching states and conduction angles of the switching devices. The core of the SVG device lies in achieving precise control, that is, achieving complete compensation to meet the changes in the load.

Since the charging equipment of electric vehicles needs to convert alternating current to direct current during operation, when a large number of power electronic devices are put into use, the power grid will generate a large amount of harmonics and reactive power, which will pose a serious threat to the stable operation of the power grid and the safety of the equipment. Therefore, it is recommended to use SVG static var generators, which can effectively improve the power quality of the charging equipment, ensure the safe operation of the power grid, and solve the problems of harmonics and reactive power.

Compared with traditional SVC devices represented by TCR, the static var generator (SVG) has a faster regulation speed, a wider operating range, and significantly reduces the content of carrier frequency harmonics in the compensation current after adopting multiple, multi-electricity and other PWM technical measures. More importantly, the reactors and capacitors used in SVG are much smaller than those used in SVC, which will greatly reduce the size of the device.