Control method for predicating switching signal of three-phase four-wire active filter
A three-phase four-wire, source filter technology, applied in active power filtering, AC network to reduce harmonics/ripples, etc., can solve problems such as increasing the burden on the controller, difficulty in ensuring system response speed, and complicated controllers
Inactive Publication Date: 2012-08-15
HUNAN UNIV
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Problems solved by technology
[0004] For the three-phase four-wire active power filter of the distribution network, since the harmonic frequency band to be controlled is very wide (generally from the 2nd harmonic to the 50th harmonic), it must be ensured that the controller has a large frequency range in the wide frequency range. Gain, the traditional PI control is difficult to meet
For this reason, the 2nd to 50th harmonics must be detected separately, and then a controller is designed for each harmonic separately, which makes the controller very complicated and it is difficult to guarantee the response speed of the system. compensation, the three phases must be controlled separately, which further increases the burden on the controller
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Embodiment 1
[0063] figure 1 It is a structure diagram of a three-level three-phase four-wire active power filter, which consists of a double capacitor, a three-level inverter bridge, and a two-stage LC output filter. Its working principle is that according to the reference current signal I ref , calculate the control switch state of the three-level inverter bridge, so that the current I injected into the grid z Can track I ref changes to achieve the purpose of harmonic filtering.
[0064] figure 2 is the reference current signal I ref Detection Schematic, I ref It consists of 3 parts: load harmonic current, active current for stabilizing capacitor voltage, and DC current for maintaining voltage balance between two capacitors. Load harmonics are detected by instantaneous reactive power theory; active current is detected by the sum of the voltages on the two capacitors, and the reference value U DCref Comparison, then PI adjustment, and finally multiplied by the sinωt that changes s...
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The invention discloses a control method for predicating a switching signal of a three-phase four-wire active filter, comprising the following steps of: step 1: acquiring a signal, and computing a reference current signal Iref, wherein the computing formula of the reference current signal is that Iref=Ipref*sin omega t+Idc-pref / 3+Ih; step 2: computing the switching time T<K+1> of the next time; T<K+1>=(Us+L1*(Iref-Iinv-Ic1-Ic2) / T +L2*(Iref-I<L>-Ic1) / T) / U<DC1>, or computing by the formula T<K+1>=-(Us+L1*(Iref-Iinv-Ic1-Ic2) / T +L2*(Iref-I<L>-Ic1) / T) / U<DC2>; and step 3: controlling a switching device of each phase in a three-level inverter bridge according to the T<K+1>. The control method for predicating the switching signal of the three-phase four-wire active filter is used for predicating the switching state of the next control period according to the single-phase status of the active filter, thereby being easy to implement, and quick in response speed.
Description
technical field [0001] The invention belongs to active filtering technology, and relates to a three-phase four-wire active filter switching signal predictive control method. Background technique [0002] With the popularization of household electronic equipment, the power quality of the distribution network has been seriously affected. In particular, the rectifier is widely used in household electrical equipment for power supply, which has brought a lot of harmonic pollution to the distribution network and must be treated. The management of harmonics mainly includes passive filters, active filters and hybrid filters. Parallel passive filter is the simplest harmonic control method, but it can only have a good filtering effect on specific harmonics, and the filtering frequency band is very narrow. A passive filter is a power electronic device that can compensate for harmonics of any frequency and size. The compensation characteristics are not affected by changes in grid imped...
Claims
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IPC IPC(8): H02J3/01
CPCY02E40/20
Inventor 荣飞罗安周贤正谢三军朱文杰
Owner HUNAN UNIV