Compensation Methods for reactive power compensation Switchgear
Reactive power compensation,plays a role in improving the power factor of the power grid in the power supply system, reducing the loss of power supply transformers and transmission lines, improving power supply efficiency and improving the power supply environment.
Therefore, the reactive power compensation device is in an indispensable and very important position in the power supply system.
Reasonable selection of compensation devices can minimize the loss of the network and improve the quality of the power grid.
On the contrary, improper selection or use may cause many factors such as power supply system, voltage fluctuation, and increased harmonics.
Today, Jiangxi Yikai electric,as a professional reactive power compensation switchgear manufacturer, will introduce you to 13 kinds of reactive power compensation methods, what are their advantages and disadvantages.
(1) Adjust the camera synchronously
Basic principle: The synchronous motor runs without load, and it generates inductive reactive power when overexcited; it absorbs inductive reactive power when underexcited;
Main advantages: It can not only send inductive reactive power, but also absorb inductive reactive power;
Main disadvantages: large loss, large noise, slow response speed, complicated structure maintenance;
Applicable occasions: There are still a few applications in power plants.
(2) On-site compensation
Basic principle: Generally, the capacitor is directly connected in parallel with the motor transformer, and the two share a switch cabinet;
Main advantages: End compensation, can reduce the line loss to the maximum;
Main disadvantages: large number of units and large investment volume;
Applicable occasions: water plants and cement plants are used more often.
(3) Centralized compensation
Basic principle: centralized installation on the system bus, generally set up a separate switch cabinet;
Main advantages: Compensation can be made for the entire substation, and the investment is relatively small;
Main disadvantages: generally fixed compensation, over compensation may occur when the load is low;
Applicable occasions: suitable for systems with small load fluctuations.
(4) Automatic compensation (mechanical switch switching capacitor)
Basic principle: Use mechanical switches (contactors, circuit breakers) to switch capacitors according to the instructions of the power factor controller;
Main advantages: It can automatically adjust the reactive power output, keep the system reactive power balanced, mature technology, small footprint, low cost;
Main disadvantages: slower response time, limited by capacitor discharge time;
Applicable occasions: the current mainstream compensation method meets the needs of users in most industries.
(5) Thyristor switching capacitor
Basic principle: adopting thyristor valve group according to the instruction of power factor controller to switch capacitors through zero;
Main advantages: fast response speed, no inrush current, no impact;
Main disadvantages: large area and high cost;
Applicable occasions: mostly used in ports and other places where the load changes rapidly.
(6) Thyristor control reactor
Basic principle: It is generally composed of a fixed parallel capacitor and a parallel reactor controlled by a thyristor in parallel. By changing the conduction angle of the thyristor, the inductor current is changed to control the reactive power output of the entire device;
Main advantages: fast response speed, stepless adjustment, can compensate both capacitive reactive power and inductive reactive power;
Main disadvantages: large area and high cost, and for most enterprise users, there is no need for emotional reactive power;
Applicable occasions: mostly used in steel, electrified railways and power transmission and transformation systems;
(7) Magnetically controlled reactor
Basic principle: the size of the excitation current and the core saturation are controlled by the thyristor to change the inductor current, thereby controlling the reactive output of the entire device;
Main advantages: dynamic response, stepless adjustment, two-way compensation, low thyristor withstand voltage, no need for multi-stage series connection, and low harmonic generation;
Main disadvantages: The response time is slightly slower than TCR and the noise is large;
Applicable occasions: Have an advantage in high-voltage systems.
(8) Series compensation
Basic principle: The series capacitor bank is used to compensate the inductance of the transmission line to improve the transmission capacity and stability of the line. Series capacitors can also adjust the load distribution of parallel lines;
Main advantages: can effectively compensate the line voltage drop and reduce line losses;
Main disadvantages: fixed compensation, capacitive reactance cannot be changed, may cause sub-synchronous resonance;
Applicable occasions: used for transmission lines.
(9) Controllable series compensation
Basic principle: Connect an inductance branch controlled by thyristors in parallel at both ends of the series capacitor compensation, and change the inductance current by changing the trigger angle of the thyristors to control the change of the equivalent impedance of the LC parallel circuit
Main advantages: It can effectively compensate the line voltage drop and reduce line losses, and at the same time can dynamically adjust the capacitive reactance to prevent sub-synchronous resonance;
Main disadvantages: large area and high cost;
Applicable occasions: used for transmission lines.
(10) Voltage and volume regulation
Basic principle: Connect the parallel capacitor device to the secondary side of the voltage regulator, and change the compensation capacity of the entire device by adjusting the capacitor withstand voltage;
Main advantages: no need for grouping, no need to switch, and more compensation stages;
Main disadvantages: increase transformer, need to install transformer room;
(11) Static reactive power generator
Basic principle: A self-commutated converter composed of IGBT is used to provide leading and lagging reactive current through voltage power inverter technology to compensate;
Main advantages: fast dynamic response, stepless adjustment, two-way compensation, no need for large-capacitance capacitor reactance, and small footprint;
Main disadvantages: control and maintenance are difficult, loss is large, and cost is high;
Applicable occasions: Reactive power compensation mode of power electronics.
(12) Active filter
Basic principle: control the PWM converter, inject currents of the same magnitude and opposite directions as the detected harmonics and reactive components into the power supply system to achieve harmonic filtering and dynamic compensation of reactive power;
Main advantages: fast dynamic response, stepless adjustment, two-way compensation, no need for large-capacitance capacitor reactance, and small footprint;
Main disadvantages: control and maintenance are difficult, loss is large, cost is high, and capacity is small;
Applicable occasions: low-voltage railways, paper mills, steel mills have been applied.
(13) Integrated power flow controller
Basic principle: an AC voltage generated by a thyristor converter is connected in series and superimposed on the phase voltage of the transmission line, so that its amplitude and phase angle can be continuously changed, thereby realizing accurate adjustment of line active and reactive power.
Remarks: It is still in the research stage of physical model.