Low Voltage Reactive Power Compensation and Filtering Cabinet
Short Description:
Facing the severe issue of power harmonic pollution, active power filters are an effective tool for improving power quality. Active power filters are specialized devices for harmonic management in power systems, made using modern power electronics technology and digital signal processing technology based on high-speed DSP devices. An active power filter functions like a harmonic current generator: it tracks the harmonic components in the source current and generates harmonic currents of equal amplitude but opposite phase, thereby canceling out the harmonic currents produced by the source.
Product details
1. Product introduction
Faced with the severe problem of power harmonic pollution, active power filters are an effective tool to improve power quality. Active power filter is a special equipment for power harmonic governance made of modern power electronics technology and digital signal processing technology based on high-speed DSP devices. The active power filter is equivalent to a harmonic current generator, which tracks the harmonic components in the current of the harmonic source and generates a harmonic current that is inverted to the same amplitude, thereby canceling out the harmonic current generated by the harmonic source. Compared with traditional passive power filters, active power filters offer the following advantages:
(1) The harmonic filtering rate is high, and the filtering performance is not affected by the impedance of the system;
(2) There will be no series or parallel resonance with the system impedance, and the change of system structure will not affect the treatment effect;
(3) It has the characteristics of broadband filtering, and one device can complete the management of each harmonic;
(4) Dynamic governance is realized, which can quickly respond to changes in the frequency and magnitude of harmonics;
(5) Since the device itself can complete the output current limit, it will not be overloaded even if the load harmonic content increases;
(6) It has a variety of compensation functions, which can compensate for reactive power and negative sequence;
(7) The harmonic compensation characteristics are not affected by the frequency change of the power grid;
(8) Multiple harmonic sources can be centrally governed.
Active power filter can be widely used in power, harmonic control, industrial, commercial, information industry and other fields, with good governance effect, energy saving, material saving, is the development direction of harmonic control technology, and has broad development prospects.
2. Introduction to the working principle
Active Power Filter (APF) is a special device for power harmonic management made of modern power electronics technology and digital signal processing technology based on high-speed DSP devices. It consists of two main parts: the instruction current operation circuit and the compensation current generation circuit. The command current operation circuit monitors the current in the line in real time, converts the analog current signal into a digital signal, sends it to a high-speed digital signal processor (DSP) to process the signal, separates the harmonics from the fundamental wave, and sends a driving pulse to the compensation current generation circuit in the form of a pulse-width modulation (PWM) signal, drives the IGBT or IPM power module, generates a compensation current equal to the amplitude of the harmonic current of the power grid, and injects it into the power grid, compensates or cancels the harmonic current, and actively eliminates the power harmonics.
Active power filter is a device that uses fully controlled power electronic components to meet the needs of users with different requirements for power quality (power factor and harmonics). The main function of the APF device is to ensure that the current on the system side is free of harmonics and reactive currents when the load side generates harmonics and reactive currents during the power supply process of the power grid, so that the user's other key sensitive equipment can operate normally in a near-undisturbed electrical environment and will not pollute the power grid.
The active power filter device adopts a hierarchical distributed controller system based on DSP-based main controller and module driver, and adopts a human-machine interface based on color touch screen, which has the characteristics of full digitalization, automation, intelligence, human-machine interface friendliness, and flexible control methods. At present, the voltage level of the product is 380V, and the filter current is 400A.
3. Product advantages
Real-time tracking and dynamic compensation
The intelligent monitoring algorithm based on the iterative discrete Fourier transform based on the sliding window breaks through the industry's classic harmonic algorithm, which is more efficient and stable. It is used to monitor the harmonic current in real time, and automatically track the harmonic changes of the power grid through PI and PR current tracking control, which has a high degree of controllability and fast response.
Power conversion design
Adopting the world's IGBT intelligent modular power devices, the main circuit adopts three-level NPC topology and sinusoidal PWM conversion technology, which has the characteristics of small size, high efficiency and good reliability, and the LCL filtering technology and multi-module parallel current sharing strategy are convenient for the expansion of the capacity of the whole machine.
Smart monitoring
It adopts floating-point operation DSP (digital signal processor) and CPLD (programmable logic device) for high-speed monitoring and calculation, harmonic monitoring and compensation accuracy is accurate and effective, and has intelligent monitoring, remote Internet supervision and automatic fault diagnosis functions, and can carry out grid connection and off-grid operations.
4. Application field
1. Petrochemical industry
Harmonic characteristics: a large number of frequency converters are used, and the harmonic current is mainly 5, 7, 11, 13, and 17 times;
Significance of harmonic governance: reduce the error of power measuring instruments, the accuracy of power management and charging;
Typical applications: chemical plants, drilling platforms;
Problem: Capacitor compensates for over-capacity or under-capacitance, and the power factor is too low, resulting in reactive power fines.
2. Steel smelting industry
Harmonic characteristics: There are a large number of impact nonlinear loads (electric arc furnaces, rolling mills) and frequency converters in the steel smelting system, which will generate 2~13 harmonic currents during operation;
The significance of harmonic control: reduce the impact of harmonic current on the power grid, ensure the safe operation of equipment, reduce the impact of harmonics on PLC and other controllers, and reduce the loss caused by equipment malfunction;
Typical applications: rolling mills;
Problem: The current of the power supply system is seriously distorted, the PLC control system is often disturbed, and the relay protection device malfunctions.
3. Communication industry
Harmonic characteristics: A large number of UPS and switching power supplies in the communication system will cause a sudden increase in 5th, 7th and 11th harmonics in the power grid, and the distortion rate is as high as 50%
The significance of harmonic governance: improve the reliability of power supply, eliminate the interference of harmonics on the communication system, and extend the life of the equipment
Typical application: Data center
Problem: The load is UPS, the inlet switch trips for no reason, and the harmonic interference is serious
4. Rail transit industry
Harmonic characteristics: The nonlinear load in the rail transit system mainly includes the locomotive traction device and the frequency converter of the electromechanical system, UPS and energy-saving lamps, etc., mainly with 3, 5, 7, 11, 13, 17 harmonic currents;
Significance of harmonic governance: through harmonic governance, ensure the safe and reliable operation of the reactive power compensation device;
Typical Applications: Subway Stations;
Problem: The reactive power compensation capacitor is easy to burn out, the compensation capacity cannot be adjusted, and the power distribution system contains a large number of harmonics.
5. Mining industry
Harmonic characteristics: mainly due to the influence of frequency conversion equipment in the system, the current harmonics of the 5th, 7th, 11th and 13th currents exceed the standard, causing serious harmonic pollution to the power grid;
The significance of harmonic control: it can reduce the temperature of the transformer, ensure reliable operation, and reduce the loss of the power grid;
Typical Applications: Mining Plants;
Problem: Multiple frequency converters are used in the power supply system of the mine, and the harmonics of each sub-harmonic seriously exceed the standard, causing the transformer to heat up seriously and affecting the safe operation of other equipment.
The working principle of the APF active power filter cabinet
The active power filter detects the load current in real time through the external current transformer CT, and extracts the harmonic component of the load current through the internal DSP calculation, and then sends it to the internal GBT through the PWM signal to control the inverter to generate a current equal to the harmonic magnitude and in the opposite direction injected into the power grid to compensate for the harmonic current and realize the filtering function.
