Reactive Power Compensation SVG: Measures to Improve Power Quality
The measures for improving power quality with reactive power compensation SVG are extensive, including reactive power compensation, harmonic suppression, reducing voltage fluctuations and flicker, and addressing three-phase imbalance. Devices used for reactive power compensation and harmonic governance, such as passive power filters, also provide reactive power compensation and voltage regulation functions. Typically, special designs are required based on the parameters of the harmonic sources, the electrical characteristics of the installation points, and user requirements. Reactive power compensation SVG is an important device for comprehensively controlling voltage fluctuations and flicker, harmonics, and voltage imbalance.
An Active Power Filter (APF) is a new type of power electronic device for dynamically suppressing harmonics and compensating for reactive power. It compensates for harmonics and reactive currents that change in frequency and amplitude. It is mainly used in low-voltage distribution systems.
Development Stages of Reactive Power Compensation SVG
The development of reactive power compensation SVG has gone through several stages: synchronous machine adjustment → switching fixed capacitors → static reactive compensators → triggering static reactive generators.
Depending on the structural principles, the technologies employed in reactive power compensation SVG are categorized into: self-saturating reactor type, thyristor phase-controlled reactor type, thyristor switched capacitor type, high-impedance transformer type, and excitation control type.
With the advancement and refinement of power electronics technology, especially in high-power switching device technology, ongoing research and development aim to create more advanced reactive power compensation SVG worldwide. Although still in development and trial operation phases, and not yet commercialized, reactive power compensation SVG is expected to see increasingly widespread application in power systems due to its superior performance characteristics.
1. What is the Principle of Reactive Power Compensation SVG?
Reactive power compensation SVG is a typical power electronic device consisting of three basic functional modules: detection module, control calculation module, and compensation output module. The working principle of reactive power compensation SVG is to detect current information through an external current transformer (CT) detection system, analyze the current information (such as power factor (PF), apparent power (S), and reactive power (Q)) using the control core; the controller then issues a compensation driving signal that leads to the issuance of compensating current from an inverter circuit composed of power electronic devices.
Working principle of reactive power compensation SVG:
Reactive power compensation SVG uses controllable power electronic devices (IGBT) to form a self-commutating bridge circuit, which is connected in parallel to the grid through a reactor, allowing for proper adjustment of the output voltage's amplitude and phase. The AC side of the bridge circuit can control its output voltage directly. This rapid absorption or release of the required reactive power by AC side current achieves the goal of quickly and dynamically adjusting reactive power. As an active compensation device, reactive power compensation SVG can not only track impact loads' surge currents but can also track and compensate for harmonic currents.
The voltage source inverter consists of a DC capacitor and an inverter bridge, where the inverter bridge is made up of controllable semiconductor devices (IGBT).
By adjusting the switching amounts of the IGBT devices in the inverter bridge during the operation of reactive power compensation SVG, the amplitude and phase of the DC to AC voltage can be controlled. Therefore, the entire device effectively acts as a phase-modulating power source. By detecting the required reactive power from the system, it can quickly issue reactive power of the same amplitude but opposite phase, achieving field balance for reactive power and maintaining high-efficiency operation of the system.
Reactive power compensation SVG features continuous, smooth, and linear reactive power compensation capabilities. It can replace traditional phase capacitors. Any target power factor can be set, allowing for compensation of both active and reactive power. Reactive power compensation SVG possesses significant advantages, including high power density, high efficiency, low cost, and low noise. It features a parallel, modular design that is compact and flexible, making it suitable as a standard component for distribution systems, and it supports third-party cabinet embedding.
2. Applications of SVG Reactive Power Compensation Equipment
The measures that SVG reactive power compensation equipment takes to improve power quality are broad, including reactive power compensation, harmonic suppression, reducing voltage fluctuations and flicker, and addressing three-phase imbalance. Devices used for reactive power compensation and harmonic control, such as passive power filters, also provide both reactive power compensation and voltage regulation capabilities. Typically, special designs are tailored based on the parameters of harmonic sources and the electrical characteristics of installation points, as well as user requirements. SVG reactive power compensation equipment is crucial for controlling voltage fluctuations, flicker, harmonics, and voltage imbalance comprehensively.
The development of SVG reactive power compensation equipment has evolved through stages from synchronous machine adjustment → switching fixed capacitors → static reactive compensators → triggering static reactive generators.
Depending on the structural principles, the technologies employed in SVG reactive power compensation equipment are divided into: self-saturating reactor type, thyristor phase-controlled reactor type, thyristor switched capacitor type, high-impedance transformer type, and excitation control type.
With the advancement of power electronics technology, particularly in high-power switching device technology, ongoing research continues to develop more advanced SVG reactive power compensation devices both domestically and internationally. Although still in development and trial phases with no commercial availability yet, these devices are anticipated to see broader applications in power systems due to their superior performance characteristics.
Characteristics of SVG Reactive Power Compensation Equipment:
Synchronous Machine Adjustment: Slow response speed, high noise level, significant losses, and outdated technology.
Switching and Fixed Capacitors: A slow compensatory method with poor continuous controllability.
SVG Reactive Power Compensation Equipment: Advanced, practical technology widely used in transmission and distribution systems, representing a more flexible AC transmission system technology and an important component of customized power source technology. This represents the development direction of modern reactive compensation devices.
3. Advantages of Reactive Power Compensation SVG
Reactive power compensation SVG devices should be installed in areas where low-voltage transformers and large electrical equipment are located, especially in industrial zones, enterprises, and residential areas with low power factors. Reactive power compensation SVG is particularly suitable for large asynchronous motors, transformers, welding machines, punching machines, lathe machines, air compressors, presses, cranes, smelting, rolling steel, rolling aluminum, large switches, electric irrigation equipment, and electric locomotives. In addition to incandescent lights in residential areas, air conditioners and refrigerators are also significant reactive power consumers. In rural areas with poor electricity supply and significant voltage fluctuations, where the power factor is particularly low, installing reactive power compensation SVG is an effective measure to improve power supply conditions and enhance the utilization of electric energy.
Here are the advantages of reactive power compensation SVG compared to other domestic products:
Compensation Method: Domestic reactive power compensation devices generally use capacitors for reactive power compensation, with compensated power factors typically around 0.8–0.9. In contrast, SVG uses power modules for reactive power compensation, achieving compensated power factors generally above 0.98.
Compensation Time: Domestic devices complete a compensation cycle in 200 milliseconds, while SVG can achieve compensation in 5–20 milliseconds. Rapid compensation is crucial; excessive compensation time could result in reactive power when not needed.
Stepless Compensation: Domestic devices generally employ 3–10 steps for compensation, altering dozens of capacitance values, making accurate compensation unattainable. SVG allows for stepless compensation starting from 0.1 kilofarads, achieving precise compensation.
Harmonic Filtering: Domestic devices employing capacitors amplify harmonics, failing to filter them adequately. SVG neither generates nor amplifies harmonics and can filter out over 50% of harmonics.
Service Life: Domestic devices typically use contactors or thyristor controls, leading to shorter lifespans of around three years, with high losses and frequent maintenance. In contrast, SVG has a service life exceeding ten years, exhibiting minimal self-loss and requiring little maintenance.
