Line harmonic control system

Abstract

The invention provides a line harmonic control system. The system comprises an active filtering assembly, a nonlinear device and a power supply, the active filtering assembly and the nonlinear device are sequentially connected through a power grid circuit, and the active filtering assembly generates a corresponding offset harmonic current according to a current in the power grid circuit, so as to make harmonic waves in the power grid circuit offset and eliminated. Harmonic waves can be effectively treated by means of suppression and filtering, the harmonic waves in a suppressible range are suppressed by means of suppression, and when the harmonic wave content in the system reaches a certain amount and the problem cannot be solved by suppression, the harmonic waves with high content are eliminated by means of filtering, so that the harmonic waves in the system can be effectively treated. Therefore, the harmonic content in the system is lower than the national standard limit, and the stable operation of the system is ensured.

Description

technical field [0001] The invention relates to the technical field of stability analysis of new energy grid-connected systems, in particular to a line harmonic control system. Background technique [0002] In recent years, due to the harmonic problem of the distribution network, the supplementary capacitor often trips and cannot be put into operation or even explodes. The microcomputer protection device also causes accidents due to malfunction or even refusal to operate. For example, in July 1998, Hunan Lianyuan Iron and Steel Co., Ltd. caused a 16-hour power outage at Baonanshan 220kV substation due to the 5th harmonic exceeding the standard, causing an economic loss of 24 million yuan; from 2001 to 2002, Guangdong Zhongjin Lingnan The 2nd and 5th harmonics seriously exceeded the standard, and high-voltage switchgear misoperation occurred many times, which caused damage to motors and transformers, resulting in economic losses of 27 million yuan; in March 2006, Nanjing Powe...

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Problems solved by technology

[0004] 1. Increase the load of power facilities, reduce the power factor of the system, reduce the effective capacity and efficiency of power generation, transmission and power consumption equipment, resulting in equipment waste, line waste and power loss;

[0005] 2. Cause resonance and harmonic current amplification of the reactive power compensation capacitor, resulting in damage to the capacitor bank due to over-current or over-voltage or failure to put it into operation;

[0006] 3. Generate pulsating torque to cause motor vibration, affecting product quality and motor life;

[0007] 4. Due to eddy current and skin effect, motors, transformers, transmission lines, etc. will overheat due to additional power loss, waste electric energy and accelerate insulation aging;

[0008] 5. The harmonic voltage enhances the electric field strength of the insulating medium in a form proportional to its peak voltage, reducing the service life of the equipment;

[0009] 6. The zero-sequence (multiple of 3) harmonic current will cause the neutral line of the three-phase four-wire system to be overloaded, and a circulating current will be generated in the transformer winding of the delta connection, causing the winding current to exceed the rated value, and even cause an accident in severe cases;

[0010] 7. Harmonics will change the action characteristics of the protection relay, cause the malfunction of the relay protection facilities, and cause the disorder of the automatic devices such as relay protection;

For example: A static var compensator SVC is applied to a node to improve the power factor and reduce the loss of electric energy; at the same time, a harmonic suppression device is used to reduce the harmonic content of the node and reduce the harmonic loss; but the SVC itself is not considered The characteristics of harmonics and the impact on harmonic suppression devices cause resonance between equipment and between equipment and the grid, which in turn causes faults in adjacent lines and forms a "critical area"

[0015] Usually specific electrical equipment will produce extremely strong high-order harmonic pollution, thereby reducing power quality, increasing the loss of lines and electrical equipment, and also affecting the normal operation of other equipment on the grid

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