Current threats to the power grid
The voltage quality of the grid is usually measured by indicators such as stability, symmetry and sinusoidality. With the large number of non-linear loads such as modern power electronic equipment connected to the grid, the power supply quality is seriously affected, and a large number of various power electronic switching devices are used therein. Frequent fluctuations in the load and load are the main sources of interference, resulting in a series of adverse effects.
â—† The lack of timely reactive power regulation in the transmission system makes it easy to expand the system oscillation and reduce the stability of the transmission system.
â—† The lack of rapid reactive power support in the load center can easily lead to low voltage or even voltage collapse.
â—† Low power factor, increased power grid losses, increased production costs, and reduced productivity.
â—† Reactive power impact caused by the grid voltage, voltage fluctuations and flicker, resulting in the transmission and protection devices can not work properly and even stop production.
◆ Produce a large number of harmonic currents, resulting in distortion of the grid voltage, which is the “hidden killer†of the grid.
Can lead to:
â— The protection and safety automatic device malfunctions.
â— The capacitor bank harmonics and harmonic currents are amplified, overloading the capacitor or over-voltage, or even burning it.
â— Increase the loss of transformers and cause transformer heating.
â— Causes the power equipment to generate heat and the motor torque is unstable or even damaged.
â— Accelerate the insulation aging of power equipment and it is easy to breakdown.
â— Reduce EAF production efficiency and increase losses.
â— Interference with communication signals.
â—† Causes the three-phase grid to be unbalanced and generates a negative-sequence current to cause the motor rotor to vibrate.
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The best solution:
At present, the most ideal solution is to use SVG to improve grid stability, increase transmission capacity, eliminate reactive power shock, filter out harmonics, and balance three-phase grids.
â—† Improve line transmission stability The installation of SVG devices on long-distance transmission lines not only compensates for reactive loss of the line under normal operating conditions, raises the line voltage, increases the effective transmission capacity, and can provide timely in the event of a system failure. Reactive power regulation, damping system oscillations, improve the stability of the transmission system.
â—† Maintain the voltage of the power receiving terminal and strengthen the voltage stability of the system For the load center, due to the large load capacity, there is no large-scale reactive power supply support, so it is easy to cause a stable accident that the voltage of the power grid is low or the voltage collapses. The SVG has a fast reactive power regulation capability, which can maintain the voltage on the load side and improve the voltage stability of the power supply system on the load side.
â—† Compensation system reactive power, increase power factor, reduce line loss, save a lot of loads in the power system, such as asynchronous motors, electric arc furnaces, rolling mills and large-capacity rectifier equipment, in the operation requires a lot of reactive power; At the same time, transformers and line impedances in transmission and distribution networks will also generate certain reactive power, which will lead to a decrease in power factor of the system.
For the power system, the low power factor of the load will increase the energy loss and voltage drop of the power supply line and reduce the voltage quality. At the same time, reactive power will also lead to lower utilization of power generation, transmission, and power supply equipment. For power users, low power factor will increase electricity bills and increase production costs.
â—† Suppression of voltage fluctuations and flicker voltage fluctuations and flicker are mainly caused by drastic changes in the load. The rapid change of the load will cause the corresponding severe fluctuation of the load current, and the violently fluctuating current will cause the system voltage loss to change rapidly, causing the flicker of the grid voltage of the power receiving end. Typical loads that cause voltage flicker are arc furnaces, rolling mills, electric locomotives, and the like.
SVG can quickly provide changing reactive currents to compensate for voltage fluctuations and flicker caused by load changes.
At present, the best solution to suppress voltage fluctuations and flicker is to use SVG.
â—† There are a large number of three-phase unbalanced loads in the three-phase unbalanced distribution network, such as electric locomotive traction loads and AC arc furnaces. At the same time, unbalanced three-phase impedance of power transmission and distribution equipment such as lines and transformers can also lead to voltage imbalance problems.
SVG can quickly compensate the negative sequence current due to load imbalance, always ensure the balance of the three-phase current flowing into the power grid, and greatly improve the power quality of power supply and use.
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Multiple compensation functions
â—† Grid-oriented applications suppress system oscillations, improve grid stability, and protect the power grid.
Due to the increasing capacity of regional grids, this requires a corresponding increase in the capacity of the compensation devices. In the hundreds of MVA-level reactive power compensation systems, the commonly used solution is to combine SVG and SVC to give full play to the rapid characteristics of SVG and the steady-state performance of SVC, so that the system achieves the most in terms of compensation characteristics, cost, and reliability. excellent.
â—† Various compensation functions for rolling mills, arc furnaces, electrified railways, etc.
â— Compensation for reactive power - The power factor can be up to 0.98. It is the most effective flicker suppression device.
â— Compensation for reactive power and harmonics - that is, compensation for reactive power and harmonic compensation at the same time.
â— Three-phase unbalanced load compensation - the most effective negative sequence current suppression device.
â— Compensation for load reactive power, harmonics and three-phase imbalance - that is, it can compensate for reactive power, and it can simultaneously compensate for harmonics and three-phase unbalance. It is the perfect solution to load power quality problems.