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Let’s learn about filters

2020-07-10 08:51
Active power filter is a new type of power engineering electronic system for dynamically suppressing harmonics and compensating reactive power. It can compensate for harmonics and reactive power that have changed in size and frequency. At this stage, the active power filter is mainly used in power consumption machinery and equipment with a rated voltage of 380V, and the power consumption machinery and equipment for high pressure levels are rarely used.
The following key points are: For the uncontrollable rectifier and the half-controlled rectifier of the high-voltage inverter, the power factor is low, the harmonics are high, and the efficiency is inferior. Complete high efficiency, environmental protection, energy conservation, and environmental protection.
Network topology and basic principles of active power filters
Compared with passive filters, the active power filter has a stronger harmonic remediation effect, can filter out several times and higher harmonics, and is not likely to cause series resonance. At present, the active power filters are dominated by low voltage, and the technical characteristics of high voltage active power filters have long been perfected, but the specific application of safety performance is very low. The international practice is to use transformers to ensure their credibility. China Relevant departments also stipulate that transformers should be combined with active power filters to rectify high-voltage harmonics.
The active power filter checks the load current according to the current transformer, and calculates it according to the internal DSP to obtain the harmonic component of the load current, and then sends it to the internal IGBT according to the PWM signal to manipulate the inverter power supply to cause a load harmonic. The amount of current is the same, and the amount of harmonic current with reversed orientation is introduced into the power grid to achieve the purpose of the filter.
The customer drives a motor (rated voltage of 64A, rated current of 8kV) with a high-voltage inverter (rated voltage of 88A and rated current of 8kV) on the spot, and each phase of the high-voltage inverter is composed of 6 modules connected in series. Only one module on the secondary side of the phase-shifting transformer is loaded as an example to show that the ZAPF active power filter is used to filter out the harmonics of the high-voltage inverter. The current wave form developed by the input front end of a module has a very large harmonic component , Achieve 71.3%, according to the transformer, the active power filter is loaded into the module, the current wave shape changes, the current wave harmonics are significantly reduced, to achieve 4.046%, to achieve national industry standards, according to the wave mode It can be seen that the active power filter can filter out the harmonics very well, and can control the environmental pollution of the power grid by the harmonics very well.
This is the case of harmonic current remediation in only one of the 18 modules. If all 18 modules are loaded with active power filters, the cost of economic development and the indoor space are very large. According to the calculation, the 8kV rated voltage developed by loading the front end of the phase-shifting transformer according to the transformer can be selected, and the volume of the active power filter should be relatively increased according to the calculation, so that the cost of economic development and indoor space can be reduced.
According to a test case, it can be shown that the combination of active power filters and high-voltage frequency converters can very well complete the clean power grid, improve work efficiency, save energy and reduce consumption, and can be vigorously developed for use in the sales market.
The test results show that the combination of active power filter and high-voltage frequency converter can very well manipulate the amount of current on the power grid side, reduce its harmonic content, and the power factor is close to 1, which greatly reduces the environmental pollution to the power grid. This type of approach rationally integrates energy conservation and consumption reduction with power energy environmental protection. The test also shows that the system software can work smoothly and reliably, and has good practical significance.
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