Improve Power Quality: 3 Methods You Should Know
With the rapid development of economy and society, people’s demand for power quality is increasing day by day, so the demand for power quality is also increasing. In order to meet the needs of production and life, it is more and more important to improve the power quality of the power supply and distribution system.
Today, let’s talk about how to improve power quality and reduce power grid pollution. We all know that the widespread application of nonlinear and impact loads makes the pollution problem in the power grid more and more serious. Since electric energy is a commodity, we must ensure its quality.
At present, in terms of reducing frequency and voltage deviation, power grid dispatching automation, reactive power optimization, and load control are common methods. What methods are used to suppress power grid harmonics and reduce voltage fluctuation and flicker?
Harmonic control
The control of harmonics(eliminating harmonics) can be divided into two aspects: prevention and remedy: preventive control refers to taking full consideration of the harmonic injection effect on the power grid during the manufacturing and design of equipment, and taking measures to minimize the generation of harmonics. Remedial treatment refers to the installation of additional harmonic treatment equipment after the equipment is put into operation to offset and reduce the existing harmonics in the system.
Harmonic prevention methods
Rectifier with multi-pulse wave number
The multi-pulse wave number rectifier formed by different wiring modes of transformer winding can reduce the generation of harmonics through phase cancellation or phase multiplexing.
Change the connection mode of transformer
The third harmonic of zero sequences can be blocked by connecting the winding with triangle type
Design of rotating electrical machine with reduced harmonic magnetic potential
Improve the pole shoe ideotype of the magnetic pole or the distribution range of the excitation winding, eliminate the third harmonic in the electromotive force by using Y-type wiring, and weaken the harmonic potential by using short distance winding and distributed winding.
Harmonic remedial method
Passive harmonic filter
It is composed of a capacitor and a reactor in series, and the parameters are set to resonate with a certain frequency. It is connected in parallel at the position where the nonlinear load is connected to the power grid to absorb the harmonic generated.
Active harmonic filter (AHF)
Its structure is relatively complex, mainly including the control part and the inverter. Theoretically, it can compensate the harmonics within any frequency range, not only the harmonics of a specific frequency, and completely recover the sinusoidal waveform of the power frequency, but it is expensive.
Hybrid active power filter
It is a very valuable use scheme. It not only has the efficient compensation capability of AHF, but also has the price advantage that AHF cannot compare under the same capacity.
The voltage fluctuation and flicker control
The voltage fluctuation and flicker are mainly caused by the impact load. We can control the voltage fluctuation and flicker by improving the power supply capacity of the power grid and installing compensation equipment, regardless of the performance of the equipment.
The voltage fluctuation and flicker are mainly caused by the impact load. We can control the voltage fluctuation and flicker by improving the power supply capacity of the power grid and installing compensation equipment.
Improve power supply capacity
- Improve the power grid supply voltage level
- Erection of lines with large load groups
- Decentralized power generation technology is adopted near sensitive loads
Installation of compensation equipment
Static var compensator SVC
The relatively simple ones are thyristor switching capacitors. The thyristor switch is used to form a contactless power electronic switch fast switching capacitor bank to realize the regulation of capacitive reactive power. The key technology is the instantaneous cut-off when the capacitor current crosses zero.
Static var generator SVG
Static var generator has the advantages of continuous adjustment, large adjustment range, fast response speed, high control accuracy, and reliable operation. It is the best dynamic reactive power compensation device at present.
Static var generator is a device for dynamic reactive power compensation by self-commutated power electronic bridge rectifier with self-rectifying charging capability. SVG is actually an inverter that can generate lead phase or lag phase current by connecting the self-commutated bridge circuit to the power grid in parallel through a reactor.
The voltage regulation range of SVG is not affected by the grid reference voltage, and the response effect speed is fast.
Remedial measures for voltage interruption and sudden drop
In case of short-term voltage interruption, the load can be supplied with power by an uninterruptible power supply (UPS). UPS requires energy storage device, usually a battery. In case of voltage interruption, UPS can provide uninterrupted power supply for several minutes to several hours, and the duration is determined by the battery capacity. The cost of UPS is high, and it is usually only used on important loads with small capacity.
In case of sudden voltage drop fault of the system, the voltage will drop rapidly. At this time, a compensation device with extremely fast response speed is required. The dynamic voltage regulator (DVR) can compensate the voltage drop to the normal value within millisecond to ensure that the load is not affected by the voltage drop.
