Method for generating high order harmonic generation in frequency converter work
1 inverter harmonic generation principle
Actually not limited to general inverter, thyristor power supply of DC motor, no motor commutator and general rectifier circuit in the power supply side of, will produce because of the nonlinearity caused by harmonics, the general inverter harmonic control is particularly important.
In the rectifier circuit, the input current waveform is irregular rectangular wave, waveform according to Fourier series decomposition for the fundamental and harmonic, harmonic number usually 6N + 1 harmonics, the harmonics will interfere with the input power supply system. If the power side reactance is sufficiently small, the commutation overlap angle can be ignored, then n times higher harmonic is the fundamental current of 1/n. Output harmonic generation mechanism: in the inverter output circuit, the output current signal is modulated by the PWM carrier signal pulse waveform. Input harmonic generation mechanism: the inverter main circuit is generally cross has been hand in a composition, external input and 380V / 50Hz power supply, the three-phase bridge controlled rectifier to the DC voltage and the filter capacitance and high power transistor switching element inverter for variable frequency AC voltage. For GTR high power inverter components, the carrier frequency of the PWM for 2 to 3 kHz, and high power element IGBT inverter PWM highest frequency up to 15KHz. Similarly, the output circuit current signal can be decomposed into only the fundamental wave and other high-order harmonics.
2 high order harmonic hazard
Conduction which is harmonic according to respective impedance shunt to the load of the power system and the parallel and electrical equipment of parallel interference; inductive coupling is defined in the transmission process, and the frequency of the output line parallel wire laying will produce electromagnetic coupling inductive interference; electromagnetic radiation is a converter output harmonics will produce radiation and interference to the nearby radio and electronic equipment. Like the general radio electromagnetic interference, the high order harmonic generated by the transducer through the transmission, electromagnetic radiation and inductive coupling three ways of power supply and proximity to use electrical equipment to produce harmonic pollution. The harm of high order harmonic is embodied in the following aspects:
(1) switching equipment: due to the harmonic current makes the switching device at the start of a very high rate of change of current, the transient recovery of peak voltage increases, the destruction of insulation, but also cause the switch off, causing false action.
(2) power capacitor: when the harmonic generated due to the increase of frequency, the capacitor impedance instantaneously reduced, poured into a large amount of current, resulting in overheating, or even damage the capacitor, there may resonate, vibration and noise.
(3) the protection of electrical appliances: the current harmonics will generate additional force distance, change the electrical characteristics of the electrical action, causing false action, and even change its operating characteristics, or burn the coil.
(4) induction motor: motor current and voltage harmonic also makes the copper loss and iron loss increase, temperature rise. At the same time, the harmonic current will change the electromagnetic torque, generate vibration torque, so that the motor cycle speed change, affect the output efficiency, and the noise.
(5) power electronic equipment: power electronic devices usually on the form of precise power zero crossing principle or voltage waveform to control and operate, if the voltage harmonic component, zero crossing mobile, waveform change, resulting in many malfunction.
(6) measuring instruments: measuring instruments because harmonics will cause the induction disk to generate extra torque, causing errors, reduce accuracy, and even burn the coil.
Transformer (7): harmonic current and voltage will increase the transformer copper loss and iron loss. As a result, the transformer temperature rise, the impact of insulating ability, resulting in capacity margin decreased. Harmonics can also produce resonance and noise, etc..
Also harmonic also on computers, communications equipment, TV and audio equipment, carrier of remote equipment interference, the communication interruption, noise, or even the occurrence of misoperation, will also to the lighting equipment.
3 suppression of high order harmonic control inverter
3.1 for the inverter output side of high harmonic control
Reduce contained in the PWM output waveform of AC harmonic components of magnetic noise technology has been more and more in all kinds of transducer applied, such as the use of more high frequency switch components, frequency output end to install filtering device and random method to adjust frequency switching and closed loop control to improve the harmonic.
3.2 for the inverter input side of the high harmonic control
(1) in the frequency converter AC input side of the AC reactor to increase the rectifier impedance to increase the overlap angle of the rectifier, reduce the high harmonic.
(2) using the AC filter in parallel in the power circuit, the harmonic component of the converter can be split from the power system.
(3) the installation of the inverter occasions, each with a dedicated transformer, the input transformer phase shifted method to suppress the harmonic.
3.3 regardless of the method, it is impossible to completely solve the harmonic governance issues, in the actual industrial production to eliminate the interference of inverter harmonic of electrical equipment, mainly from three aspects of conduction, radiation and coupling. The general principle is to restrain and cut off the interference source, cut off the interference to the system coupling channel and reduce the sensitivity to the interference signal. Solve the conduction interference is mainly in the circuit in the conduction of high frequency current filter out or shut out and solve the radiation interference is the radiation source or interference is line shielding, solve the interference coupling is a reasonable layout of the interference source and interference line distance, to avoid coupling.
In addition to the use of such as isolation, shielding, grounding
Actually not limited to general inverter, thyristor power supply of DC motor, no motor commutator and general rectifier circuit in the power supply side of, will produce because of the nonlinearity caused by harmonics, the general inverter harmonic control is particularly important.
In the rectifier circuit, the input current waveform is irregular rectangular wave, waveform according to Fourier series decomposition for the fundamental and harmonic, harmonic number usually 6N + 1 harmonics, the harmonics will interfere with the input power supply system. If the power side reactance is sufficiently small, the commutation overlap angle can be ignored, then n times higher harmonic is the fundamental current of 1/n. Output harmonic generation mechanism: in the inverter output circuit, the output current signal is modulated by the PWM carrier signal pulse waveform. Input harmonic generation mechanism: the inverter main circuit is generally cross has been hand in a composition, external input and 380V / 50Hz power supply, the three-phase bridge controlled rectifier to the DC voltage and the filter capacitance and high power transistor switching element inverter for variable frequency AC voltage. For GTR high power inverter components, the carrier frequency of the PWM for 2 to 3 kHz, and high power element IGBT inverter PWM highest frequency up to 15KHz. Similarly, the output circuit current signal can be decomposed into only the fundamental wave and other high-order harmonics.
2 high order harmonic hazard
Conduction which is harmonic according to respective impedance shunt to the load of the power system and the parallel and electrical equipment of parallel interference; inductive coupling is defined in the transmission process, and the frequency of the output line parallel wire laying will produce electromagnetic coupling inductive interference; electromagnetic radiation is a converter output harmonics will produce radiation and interference to the nearby radio and electronic equipment. Like the general radio electromagnetic interference, the high order harmonic generated by the transducer through the transmission, electromagnetic radiation and inductive coupling three ways of power supply and proximity to use electrical equipment to produce harmonic pollution. The harm of high order harmonic is embodied in the following aspects:
(1) switching equipment: due to the harmonic current makes the switching device at the start of a very high rate of change of current, the transient recovery of peak voltage increases, the destruction of insulation, but also cause the switch off, causing false action.
(2) power capacitor: when the harmonic generated due to the increase of frequency, the capacitor impedance instantaneously reduced, poured into a large amount of current, resulting in overheating, or even damage the capacitor, there may resonate, vibration and noise.
(3) the protection of electrical appliances: the current harmonics will generate additional force distance, change the electrical characteristics of the electrical action, causing false action, and even change its operating characteristics, or burn the coil.
(4) induction motor: motor current and voltage harmonic also makes the copper loss and iron loss increase, temperature rise. At the same time, the harmonic current will change the electromagnetic torque, generate vibration torque, so that the motor cycle speed change, affect the output efficiency, and the noise.
(5) power electronic equipment: power electronic devices usually on the form of precise power zero crossing principle or voltage waveform to control and operate, if the voltage harmonic component, zero crossing mobile, waveform change, resulting in many malfunction.
(6) measuring instruments: measuring instruments because harmonics will cause the induction disk to generate extra torque, causing errors, reduce accuracy, and even burn the coil.
Transformer (7): harmonic current and voltage will increase the transformer copper loss and iron loss. As a result, the transformer temperature rise, the impact of insulating ability, resulting in capacity margin decreased. Harmonics can also produce resonance and noise, etc..
Also harmonic also on computers, communications equipment, TV and audio equipment, carrier of remote equipment interference, the communication interruption, noise, or even the occurrence of misoperation, will also to the lighting equipment.
3 suppression of high order harmonic control inverter
3.1 for the inverter output side of high harmonic control
Reduce contained in the PWM output waveform of AC harmonic components of magnetic noise technology has been more and more in all kinds of transducer applied, such as the use of more high frequency switch components, frequency output end to install filtering device and random method to adjust frequency switching and closed loop control to improve the harmonic.
3.2 for the inverter input side of the high harmonic control
(1) in the frequency converter AC input side of the AC reactor to increase the rectifier impedance to increase the overlap angle of the rectifier, reduce the high harmonic.
(2) using the AC filter in parallel in the power circuit, the harmonic component of the converter can be split from the power system.
(3) the installation of the inverter occasions, each with a dedicated transformer, the input transformer phase shifted method to suppress the harmonic.
3.3 regardless of the method, it is impossible to completely solve the harmonic governance issues, in the actual industrial production to eliminate the interference of inverter harmonic of electrical equipment, mainly from three aspects of conduction, radiation and coupling. The general principle is to restrain and cut off the interference source, cut off the interference to the system coupling channel and reduce the sensitivity to the interference signal. Solve the conduction interference is mainly in the circuit in the conduction of high frequency current filter out or shut out and solve the radiation interference is the radiation source or interference is line shielding, solve the interference coupling is a reasonable layout of the interference source and interference line distance, to avoid coupling.
In addition to the use of such as isolation, shielding, grounding
| Datetime：2016.03.29 From： Views：