LDAPF has an unprecedented comprehensive power quality management capabilities, the device to compensate for reactive power, 2-51 times harmonic, three-phase imbalance-based, the device can be more than parallel operation at the same time, the whole efficiency of more than 97.5%, fully applicable to industry, Civil areas of various circumstances, is the nonlinear load harmonic control and reactive power compensation the best solution.
〓Functional principle
Users can set the parameters, so that equipment can also have a filter harmonic, dynamic compensation reactive power, compensation for three-phase imbalance, compensation voltage drop and other functions.
◆ filter out the harmonic principle
The device realizes the current signal through the external current transformer, separates the harmonic part through the internal detection circuit, generates the compensation current which is opposite to the harmonic level in the system through the IGBT power converter, and realizes the function of filtering the harmonic The
The output compensation current of the device changes dynamically according to the harmonic quantity of the system, so there is no problem of overcompensation. In addition, the device has an overload protection function, when the system harmonic is greater than the filter capacity, the device can automatically limit the output capacity of 100% rated capacity, no overload.
◆ compensation reactive power principle
The device generates the capacitive or inductive fundamental current through the IGBT power converter according to the reactive power of the system to achieve the purpose of dynamic reactive power compensation. The compensation target value can be set by the operation panel without compensation and smoothing , Will not produce on the load and the power surge surge.
◆ compensation three-phase unbalance principle
The device according to the system current, dq coordinate rotation, extract the negative sequence component, the three-phase current negative part of the compensation to zero, you can three-phase unbalanced current can be corrected to three-phase balanced current.
〓Principle of internal control
After the isolation switch is closed, to prevent the instantaneous impact of the grid on the DC bus capacitor at power-up, the device first charges the capacitor of the DC bus through a soft-acting resistor, which lasts for several tens of seconds. When the bus voltage Udc reaches a predetermined value, the main contactor is closed. DC capacitors as energy storage devices, through the IGBT inverter and the internal reactor output compensation current to provide energy. The device collects the current signal from the external CT real-time signal to the signal conditioning circuit and then sends it to the controller. The controller divides the fundamental components and extracts all the harmonic currents, reactive currents, and three-phase unbalanced currents. The current components to be compensated are compared with the compensation currents that have been issued by the device. As a real-time compensation Signal output to the drive circuit, triggering the IGBT converter to compensate the current injected into the grid, to achieve closed-loop control to complete the compensation function.
〓Product Features
● Modular design, any module failure will not affect the normal work of other modules, greatly improving the reliability of the whole machine equipment;
● Simultaneous filtering of harmonic current; reactive power compensation can make the power factor of 1; can correct the three-phase current imbalance to complete balance;
● filter, compensation reactive power, compensation three-phase imbalance can be selected or multi-election, and can set the priority of the function;
● Sliding window iterative DFT detection algorithm, fast, instantaneous response time is less than 0.1ms, the device compensation full response time is less than 10ms;
● In the field can be connected with any LC passive equipment, and no resonance occurs;
● The use of reliable current limiting control link, when the system to be compensated current is greater than the device capacity, the device can automatically limit the flow of 100% capacity output, to maintain normal work, there will be no overload burn failure;
● using high-definition 7-inch touch screen, easy to operate, the screen real-time display device operating parameters, with fault alarm and recall function;
● 600mm wide cabinet maximum power of 450A / 300kVAR, 800mm wide cabinet of high power up to 900A / 600kVAR;
● input in accordance with the two lightning protection design, equipped with a reliable surge protection device, in the event of lightning protection, does not damage the equipment;
● The use of layered design, dust and rain will not be attached to the circuit board, to adapt to the use of harsh conditions.
〓Method of Calculating Harmonic Current
According to years of operating experience, derived the following harmonic current calculation empirical formula, to meet the engineering design requirements. The formula is empirical formula, the calculation process involves only numerical calculation, does not involve the dimension.
Ih = SL x ah
Ih harmonic current (A); SL calculated load rated capacity (KVA);
ah compensation coefficient, usually between 0.075-0.3, unit / KV
■ No special interference items: such as office buildings, residential buildings, etc., the compensation coefficient of 0.075 ~ 0.12.
■ medium interference items: such as energy-saving lamps, computers, copiers, air conditioning relatively concentrated office buildings, lighting, more sports venues and stage theaters, communications data centers, banking data centers, television studios, general factories, compensation The coefficient is chosen from 0.12 to 0.225.
■ strong interference of the project: such as communication base stations, electric arc furnace, large UPS equipment, frequency converter, welding machine, rectifier equipment and other factories, the compensation coefficient selected 0.225 ~ 0.3.
Example: Configure APF capacity calculation as follows:
■ According to the above calculation formula and determine the operating environment for the "medium interference": Harmonic current = 800 × 0.1725 = 138A, selected 150A specifications
■ Calculated according to the THD determination capacity method in the harmonic load table
Shop lighting 210A × 15% + landscape lighting 145A × 15% + living water pump (frequency) 197A × 33% + office electricity 158A × 15% + change
Frequency air conditioning 210A × 10% = 31 + 21 +65 +23 +21 = 169A, selected 150A specifications
〓Common harmonic content of common harmonic loads
〓CT installation location
The CT current can not contain the current of the passive filter device when a parallel capacitor or a passive filter device has been installed in the field. Specific examples
