Definition of harmonic

The Sinusoidal voltage is energized to non-liner loads that naturally produce a non-sinusoidal current. The current drawn by non-linear loads passes through all of the impedance between the system source and load. This current produces harmonic voltages for each harmonic as it flows through the system impedance. These harmonic voltages sum and produce a distorted voltage when combined with the fundamental. The voltage distortion magnitude is dependent on the source impedance and the harmonic voltages produced. Making Fourier series decomposition for sinusoidal wave, in which the frequency and power frequency are the same that known as the fundamental wave, the frequency is greater than the power frequency is called harmonic.

Harmful effects of harmonic

•The equipment will increase the additional harmonic loss in the utility power grid, reduce the efficiency of power grid�ptransmission line and electrical equipment, add the loss in the power grid.
•Due to flow a lot of 3   and its integer multiple of harmonic current through zero line in the three-phase four �Cwire that Cause the over-heating in the zero line.
•Can age insulation of the electrical equipments. Hence it can reduce in efficiency of power generation, transmission and its utilization.
•The harmonic is east to occurs the parallel resonance and serial resonance between power and compensation capacitor, can make amplification of several times or even dozens of times to cause over-current, destroy the capacitors and reactors, serious harmonic can cause tripping accidents. 
•Can cause some malfunction of protection equipment, increased error in energy meters. Studies have indicated that there will be a decrease in energy recorded due to the presence of harmonics.
•Can cause Inductive interference with neighboring communication network. The harmonic existing in the power line caused interference in the adjacent communication lines thereby corrupting the messages being transmitted on the communication networks.

Introduction of harmonic standard

According to the national standard requirement��Power Quality And Harmonic In The Public Network��, Limits of harmonic voltage(phase voltage) in the public network are show in the table:

In the public joint point the minimum short-circuit capacitance value is different from the short-circuit capacitance value of above list; can modify each current value in table according the following formula:

In formula: S   -The minimum short-circuit capacity of the public joint point
                    S   -The benchmark short-circuit capacity
                    I    - The Nth harmonic current allowable value in table
                    In   - The nth harmonic current allowable value of the short-circuit capacity is S
Introduction of APF series active power filter

Active power filter connected to the power grid in parallel way to detect harmonic load and reactive component. APF load current which is equal and opposite with harmonic and reactive component into the supply and distribution system in PWM transformation technology, to realize harmonic suppression and dynamic reactive compensation.

Equipment design and production of reference standard

Technical characteristics

Real-time following, dynamic compensation

Using harmonic current detecting method Based on the instantaneous reactive power theory ,real-time monitoring of harmonic current and realize dynamic compensation via instantaneous current following. Automatically track the change of harmonic wave in the power grid, highly controllable and fast responsiveness.

Excellent compensation

Compensation performance is not affected by the impedance in the system, can eliminate the risk of resonance with impedance in the system, can also be used to suppress resonance that cause by harmonic in the power system.

Flexible compensation

Multi-function, can not only control harmonic, but also compensate reactive power, and increase power fact. Can be to compensate single harmonic resource or for multiple harmonic resource. Can realize to control specify harmonic during harmonic control.

DSP(digital signal processing) intelligent monitoring

DSP high speed monitoring and operation to ensure harmonic monitoring and compensation control effectively. Compatible with intelligent monitoring, easy to operate, display the parameter and operating status in the same time, fault auto-analysis, a remote communication interface, can be real-time monitoring by PC.

Advanced power conversion design

Derived from IGBT high frequency converter switching with using advanced control techniques. The main topology is three-phase bridge controlled PWM converter with characteristics of small dimension, high efficiency and high reliable.

Standard modular design

Using modular structure to compose with power circuit and control circuit, and realize to standard production at the same of improving reliability and maintainability in the processing.

Illustration

Technical parameter