Part 1: The Importance of Power to Humanity
Electricity! We are both familiar and unfamiliar. Electricity is widely used in our lives, ranging from lamps, televisions, computers, telephones, etc. in our daily life. In modern industry, agriculture and other sectors of the national economy, electricity is the main source of power to support the operation and production of power equipment.
In the early stage of electric power development, short-term voltage changes have little impact on the power load, and only need to ensure the continuous and reliable power supply. Sex raises many new and unprecedented questions. In the modern power system, the upgrading of power electronic equipment will lead to the emergence of many new frequency converters, rectifiers, electric arc furnaces, etc. in the power grid. The power consumption of these power equipment is nonlinear, impactful and unbalanced, which will generate electromagnetic interference and affect the safe operation of the power system and power network. It causes heavy losses to the production and economic operation of enterprises, and improving the power quality is of great significance to ensure the quality of industrial products and reduce energy consumption.
Part II: What is Power Quality
Power Quality (PowerQuality), strictly speaking, the main indicators to measure power quality are voltage, frequency and waveform. In a general sense, it refers to high-quality power supply, including voltage quality, current quality, power supply quality and power consumption quality. Power quality problems can be defined as: deviations in voltage, current or frequency that cause electrical equipment to malfunction or fail to work properly, including frequency deviation, voltage deviation, voltage fluctuation and flicker, three-phase unbalance, instantaneous or transient overshoot. Voltage, waveform distortion (harmonics), voltage sags, interruptions, swells, and power supply continuity, etc.
An ideal power system should supply power to users at a specified voltage level (nominal voltage) with a constant frequency (50Hz) and sinusoidal waveform. In a three-phase AC power system, the voltage and current of each phase should be in a symmetrical state with equal amplitudes and a phase difference of 120°. Due to the fact that the parameters of each element of the system (generator, transformer, line, etc.) are not ideally linear or symmetrical, the load properties are different and change randomly, coupled with the imperfect control means, operation, external interference and various faults, etc. This ideal state does not exist in practice, and various problems in power grid operation, electrical equipment and electricity consumption have arisen from this, and the concept of power quality (PowerQuality) has also been generated.
Part 3: Causes of Power Quality Problems
In a broad sense, the factors affecting power quality mainly include three aspects:
1. The influence of natural factors such as lightning strikes, storms, rain and snow on the power quality will cause accidents in the power grid and reduce the reliability of power supply.
2. The startup and shutdown of large power equipment, the automatic protection of power equipment and devices such as automatic switch tripping and reclosing, and the influence of normal operation on the power quality will temporarily reduce the rated voltage, produce fluctuations and flicker, etc.
3. The extensive use of nonlinear loads and impact loads, such as steelmaking electric arc furnaces and the operation of electrified locomotives, have an impact on power quality, causing a large amount of harmonic interference, voltage disturbance, voltage fluctuation and flicker in the public power grid. Wait.
In terms of the degree of harm, the harm of some power quality problems is destructive. For example, the overvoltage caused by the harmonic resonance caused by lightning wave impact, capacitor and cable line switching often causes insulation and mechanical damage of electrical equipment, thus affecting the normal operation of the power system; short-term voltage interruption or voltage sag may Lead to production chaos or a large number of scrapped industrial smelting products and even endanger personal safety.
Part 4: Classification of Power Quality Problems
Power quality problems can also be classified according to voltage quality and current quality. The contents of power quality are shown in the following figure.
The fifth part: the comprehensive management plan of part of the power quality of Shenghong Electric;
|Harmonic Control||Sinexcel Active Power Filter APF|
|Reactive power compensation||Sinexcel Static Var Generator SVG|
|Three-phase unbalance treatment||Sinexcel full control power quality correction device SPC|
|Voltage sag, flash stop||Sinexcel real-time control dynamic voltage regulator AVC-RTS|