As an efficient reactive power compensation technology, SVG (Static Var Generator) is a key tool to improve the grid-connected performance of photovoltaic power stations, reduce system losses, and improve power quality.
As the photovoltaic industry and home solar power system continue to grow mature and power grid requirements continue to improve, the application of static var generator will become more widespread, which is of great significance to promote the development of photovoltaic power stations, especially large-scale photovoltaic power stations.
For power system operators and photovoltaic power plant investors, understanding and correctly applying static var generator technology will help improve the economic and technical benefits of photovoltaic projects and achieve efficient use of green energy.
This article will delve into the role of static var generator in photovoltaic power plants, also how to optimize the performance and economic benefits of power plants by improving power factor and reducing losses.
1. What is static var generator？
The static var generator is an advanced reactive power compensation equipment. Its main working principle is to use power electronics technology to quickly and accurately provide reactive power to improve power quality. The following is a detailed introduction to the working principle, application scenarios and advantages of static var generators compared with traditional devices.
2. How static var generator works
The reactive power compensation static var generator uses a power electronic device (IGBT) that can be turned off to form a self-commutated bridge circuit, which is connected in parallel to the power grid through a reactor to appropriately adjust the amplitude and phase of the output voltage from the AC side of the bridge circuit, or directly control its output voltage. For further information, you can also refer to inverter IGBT.
The AC side current quickly absorbs or releases the required reactive power to achieve the purpose of quickly and dynamically adjusting reactive power. Reactive power compensation static var generator, as an active compensation device, can not only track the impact current of the impact load, but also track and compensate for the harmonic current.
The voltage source inverter, such as 2000w inverter and 3000w inverter, consists of two parts: a DC capacitor and an inverter bridge. The inverter bridge is composed of a turn-off semiconductor device IGBT. In the operation of the reactive power compensation static var generator, by adjusting the switching value of the IGBT device in the inverter bridge, the amplitude and phase of the DC to AC voltage can be controlled.
Therefore, the entire device is equivalent to a phase-modulated power supply. By detecting the reactive power required by the system, reactive power with the same amplitude and opposite phase can be quickly emitted to achieve on-site balance of reactive power and maintain high-rate operation of the system.
Reactive power compensation static var generator has continuous, smooth and linear reactive power compensation capabilities and any target power factor value can be set. Both reactive power and reactive power can be compensated.
The reactive power compensation static var generator has significant advantages such as high power density, high efficiency, low cost, and low noise. It has a parallel and plug-in modular design, compact structure, and flexible design. It can be used as a standard component of the power distribution system and it supports third-party cabinet embedding.
3. Advantages of static var generator
Reactive power compensation static var generator devices should be installed wherever low-voltage transformers are installed and next to large electrical equipment, especially in industrial and mining areas, enterprises and residential areas with low power factors.
Reactive power compensation static var generator is especially suitable for large asynchronous motors, transformers, welding machines, punch machines, lathe groups, air compressors, presses, cranes, smelting, steel rolling, aluminum rolling, large switches, electric irrigation equipment, electric locomotives, etc.
In addition to incandescent lamps in residential areas, air conditioners and refrigerators are also reactive power consumers that cannot be ignored. The electricity consumption situation in rural areas is relatively poor, with insufficient power supply in most areas, large voltage fluctuations, and particularly low power factors.
Installing reactive power compensation static var generator is an effective measure to improve the power supply situation and increase the utilization rate of electric energy. Compared with traditional devices (such as capacitors and reactor combinations), reactive power compensation static var generator devices have the following advantages:
- Fast response: The static var generator can respond to changes in reactive power in milliseconds, while traditional devices respond slowly.
- Continuous adjustment: The static var generator can realize continuous adjustment of reactive power without being limited by step changes.
- Two-way regulation: The static var generator can not only provide reactive power, but also absorb excess reactive power from the power grid.
- Adaptability to harmonics: Static var generator can suppress system harmonics and improve power quality, while traditional devices may require additional harmonic control facilities.
- No overload protection required: The static var generator does not require overload protection due to excessive reactive power during operation, and is relatively more stable and reliable.
- Small footprint: Since the static var generator is based on power electronics technology, its size is smaller than traditional equipment and its installation is more flexible and convenient.
- Low maintenance costs: Due to its simple semiconductor devices and controls, static var generators have lower maintenance costs than traditional devices that require regular maintenance.
- Compensation method: Traditional devices basically use capacitors for reactive power compensation, and the power factor after compensation is generally around 0.8-0.9. The static var generator uses power modules for reactive power compensation. The compensated power factor is generally above 0.98.
- Compensation time: The traditional device completes one compensation in 200 milliseconds, while the static var generator can complete one compensation in 5-20 milliseconds. Static var generator needs to be completed in an instant. If the compensation time is too long, it will cause the undesirable situation that there is no power when there should be power and there is power when there should not be.
- Stepless compensation: Traditional devices basically use 3-10 levels of step-by-step compensation, with hundreds of thousands of ways to increase or decrease each time, making it impossible to achieve accurate compensation. The static var generator can perform stepless compensation starting from 0.1 thousand farads, fully achieving accurate compensation.
- Harmonic filtering: Since traditional devices use capacitors, the capacitor itself will amplify harmonics and cannot filter out harmonics at all. The static var generator does not produce harmonics, nor does it amplify harmonics, and can filter out more than 50% of harmonics.
- Service life: Traditional devices are generally controlled by contactors or thyristors. They have a short service life, usually about three years, and require large losses and frequent maintenance. The service life of a static var generator is more than ten years, its own loss is very small, and it basically requires no maintenance.
4. Applications of static var generator
Static var generator reactive power compensation equipment can take a wide range of measures to improve power quality, including reactive power compensation, harmonic suppression, reducing voltage fluctuations and flicker, and solving three-phase unbalance.
Devices used for reactive power compensation and harmonic control, such as passive power filters, have both reactive power compensation and voltage regulation functions. Generally, special design is required based on the parameters of the harmonic source, the electrical characteristics of the installation point and user requirements.
Static var generator reactive power compensation equipment is an important equipment for comprehensively controlling voltage fluctuations and flickers, harmonics and voltage imbalance. Active power filter (APF) is a new power electronic device that dynamically suppresses harmonics and compensates reactive power. It compensates for harmonic and reactive currents that vary in frequency and amplitude. Mainly used in low voltage power distribution systems.
Among them, the development of static var generator reactive power compensation equipment has gone through several different stages from synchronous camera adjustment → switching fixed capacitor → static var compensator → triggering static var generator.
According to different structural principles, the technologies used in static var generator reactive power compensation equipment are divided into: self-saturating reactor type, thyristor phase-controlled reactor type, thyristor switched capacitor type, high-resistance transformer type and excitation control type.
With the development and improvement of power electronics technology and smart grid technology, especially high-power breaking device technology, more advanced static var generator reactive power compensation equipment is still being developed over the world.
Although still under development and trial operation, it has not yet been commercialized. Static var generator reactive power compensation equipment will be increasingly widely used in power systems due to its superior performance characteristics. Static var generator is often used in the following scenarios:
- Industrial enterprises: Especially industries with higher power quality requirements, such as semiconductors, precision manufacturing, etc.
- Data center: Ensure stable power supply in the data center and protect sensitive IT equipment.
- Renewable energy: Such as wind power and solar farms, improving the quality of grid access.
- Public power grid: Provide grid reactive power regulation and optimize power quality.
- Commercial buildings: Large shopping malls, office buildings, etc., to improve energy efficiency and stability of power systems.
5. How to improve static var generator power factor?
Power factor is an important indicator to measure power quality and is directly related to the efficiency of power utilization and the operating cost of the power system. In a photovoltaic power station, the power output from the photovoltaic array exhibits fluctuation. This fluctuation not only includes changes in active power, but is also accompanied by changes in reactive power.
The static var generator can detect the voltage and current status of the power grid in real time and quickly compensate for the reactive power, so that the power factor of the power station is close to 1, that is, "unit power factor" is achieved, which can maximize the transmission of effective power.
6. How to reduce static var generator losses?
When reactive power is present in a power system, it causes the current to increase, resulting in more line losses and equipment heat losses. The static var generator reduces the current levels in the system by effectively controlling reactive power, thereby reducing losses.
In addition, the dynamic adjustment capability of the static var generator also means that when the photovoltaic output fluctuates, it can quickly compensate for the corresponding reactive power, maintain the stability of the power grid, reduce power loss, and improve the economic efficiency of the entire power system.