Method for predicting harmonic current of hybrid active power filter based on optimal linear prediction theory
A harmonic current and linear prediction technology, applied in the direction of measuring current/voltage, measuring electrical variables, active power filtering, etc., can solve problems such as complex calculations, difficulty in realizing digitization, and difficulty in implementing analog circuits
Inactive Publication Date: 2013-04-03
HUNAN UNIV OF TECH
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In the article "An adaptive kalman filter for dynamic harmonic state estimation and harmonic injection tracking" in the 20th issue of "Transaction on Power Delivery" in 2005, the inner loop controller adopts the predictive current control strategy, and uses the state information at the current sampling time to predict the next sampling Periodically compensate the trajectory of the current, so as to determine the switching function of the inverter, so that the compensation current follows the change of the current reference value, and realizes the harmonic current predictive control, but there are disadvantages such as complicated calculation
The article "Predictive transient-following control of shunt and series active power filters" in the 17th issue of "IEEE Transactions on Power Electronics" in 2002 adopts the neural network prediction method, which has the advantage of strong tracking and detection ability, but the disadvantage is that it is difficult to realize digitization. And its analog circuit implementation itself is also more difficult
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[0033] Prediction principle of harmonic current:
[0034] The prediction principle and basic steps of harmonic current are:
[0035] The first step is to find the transfer function: set the harmonic current signal x(t) at t=0, and the sampling values of T, L, nT and L are respectively x(0), x(1), L, x(nm) , L, x(n-1), x(n), L, where T is the sampling period. If m values such as x(n-1), L, x(n-m) are known, the linear predicted value of harmonic current is
[0036] x ^ ( n ) = X k = 1 m a mk x ( n - k )
[0037] Where a mk Is the linear prediction coefficient. Let x(n) be its true value, the predicted error value can be obtained
[0038] e m ( n ) = x ( n ) - x ^ ( n ) = x ( n ) - X k = 1 m a mk x ( n - k )
[0039] Perform Z transformation on the error value to get
[0040] E m ( z ) = X ( z ) - X k ...
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The invention provides a method for predicting the harmonic current of a hybrid active power filter based on an optimal linear prediction theory. The method comprises the following steps of: 1, obtaining a harmonic current prediction error and carrying out Z conversion to obtain a harmonic current transmission function; 2, taking a partial derivative of a prediction error mean square value on a prediction coefficient as zero, deducing a regular equation of an optimal prediction coefficient, and obtaining an order updating equation of the prediction coefficient through a Levinson-Durbin method; 3, obtaining a minimum prediction error value of the harmonic current according to the definition of a minimum prediction error and the regular equation of the optimal prediction coefficient; and 4,obtaining an optimal harmonic current predication value according to the minimum prediction error value. According to the method disclosed by the invention, the harmonic current can be accurately predicted; the minimum error compensation is realized through a self-adaptive predication control policy; and the simulation and experimental results show that the method has the characteristics of beinghigh in prediction precision, good in compensation effect and the like.
Description
Technical field [0001] The invention relates to a harmonic current prediction method of a power filter, in particular to a hybrid power filter harmonic current prediction method based on the optimal linear prediction theory. technical background [0002] Hybrid active power filter (HAPF) composed of passive filter and active filter has many advantages such as low cost and good filtering effect. It plays an increasingly important role in power quality adjustment and control. Important role. It mainly uses passive filters to suppress harmonics and compensate reactive power, while active filters are only used to improve the filtering effect of passive filters. Real-time and accurate detection of harmonic currents in the load is an important part of improving the HAPF compensation effect. However, the sampling, A / D conversion, signal calculation, and discretization of the control signal in the HAPF digital controller will introduce more serious delays. This will cause the compensa...
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IPC IPC(8): H02J3/01G01R19/00
CPCY02E40/40Y02E40/22Y02E40/20
Inventor 李圣清
Owner HUNAN UNIV OF TECH