How can a low-voltage static var generator (SVG) quickly and accurately identify the specific changes in the power grid's reactive current demand?
Publish Time: 2025-12-31
In modern industrial and commercial power distribution systems, a large number of nonlinear loads are connected, leading to severe fluctuations in the power factor, frequent voltage flicker, and increased harmonic content. Traditional capacitor-switched reactive power compensation devices are slow to respond, have low accuracy, and are prone to system resonance, making them unable to meet the demands of high-dynamic, high-reliability power quality management. The low-voltage static var generator (SVG), with its millisecond-level response, continuous adjustability, and bidirectional compensation capabilities, has become the core equipment for the next generation of dynamic reactive power compensation. The prerequisite for its efficient compensation lies in its ability to "understand" the rapidly changing reactive power demand of the power grid—this relies on a high-speed, intelligent, and robust power grid state perception and current command generation mechanism.1. High-precision real-time sampling and synchronous phase-locked loop technologyThe SVG first uses a high-bandwidth current/voltage transformer to synchronously acquire the three-phase voltage and load current signals of the power grid at a sampling frequency of no less than 10 kHz. The key lies in employing digital phase-locked loops (PLLs) or software PLLs based on the αβ coordinate system to accurately extract the fundamental phase and frequency of the grid voltage. Even under voltage distortion or imbalance conditions, a stable reference coordinate system can be established. This "time base" is the cornerstone of the accuracy of subsequent reactive power component separation.2. Instantaneous Reactive Power Theory Achieves Millisecond-Level DecompositionSVG commonly uses algorithms based on instantaneous reactive power theory to decompose the three-phase load current into active and reactive components in real time under the dq rotating coordinate system. This method requires no filtering delay and can complete the calculation within a single power frequency cycle, even outputting compensation commands one beat in advance through predictive control. For complex currents containing harmonics, some high-end SVGs also integrate FFT or wavelet transform modules to further separate the reactive power of each harmonic, achieving "on-demand" compensation.3. Closed-Loop Current Control Achieves Precise TrackingAfter identifying the reactive current command requiring compensation, the SVG drives a self-commutating bridge circuit through direct current control, injecting a current with the same amplitude but opposite phase to the load reactive component into the grid via the output reactor. Thanks to the high-frequency switching capabilities of fully controllable devices such as IGBTs, SVG can achieve high-fidelity tracking of command current with a dynamic response time of less than 5 ms, far faster than the second-level response of traditional TSC/TCR devices.4. Modular Architecture Enhances Adaptability and ReliabilityTo meet different capacity and scenario requirements, modern low-voltage SVG adopts a modular design, allowing multiple power units to be connected in parallel for expansion. Each module samples and controls independently, achieving current sharing and coordination through high-speed CAN or fiber optic communication to avoid single points of failure. Simultaneously, the module casing has a high protection level, and the internal circuitry is treated with conformal coating, enabling stable operation in harsh industrial environments such as dust, high temperature, and high humidity. This "plug-and-play" flexibility allows SVG to be quickly deployed in distribution cabinets, near motors, or at the end of production lines, addressing reactive power issues locally.5. Multifunctional Integration and Intelligent SchedulingAdvanced SVG not only compensates for fundamental reactive power but also integrates active filtering, three-phase imbalance management, and voltage support functions. Its control system incorporates a power quality analysis module, which can monitor power factor, THD, voltage deviation, and other indicators in real time, and automatically adjust compensation targets according to preset strategies. Some products support linkage with EMS energy management systems to proactively optimize reactive power distribution during peak electricity consumption periods, reduce line losses, and help enterprises save energy and reduce carbon emissions.The reason why low-voltage static var generators (SVG) can be so responsive and efficient in complex power grids lies in their integration of high-speed sensing, advanced algorithms, and power electronic execution, constructing a closed loop of "perception-decision-execution." It can not only accurately capture subtle changes in the reactive power demand of the power grid, but also proactively "supply" the required current at millisecond speeds, truly achieving "dynamic follow-up and on-demand compensation." In today's increasingly stringent power quality requirements of new power systems, SVG is moving from a "supporting role" to a "leading role," becoming a key force in ensuring the efficient, stable, and green operation of the power grid.
