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Position:IcFull.com » IC Electronic information » Category: R

IC Electronic information

RCP-based design of hybrid power filter

In Electronic Infomation Category: R | on April 15,2011

Abstract: To solve the harmonic control in power systems, digital controller design cycle is long, the problem of higher cost of investment in the study of traditional power filters designed on the basis of a fast control model. In the tradition of adding a filter structure based on the active power filter, while the use of computer-aided software company Simulink and MC10H104L datasheet and TI DSP development environment CCS, on the hybrid active power filter in-circuit debugging and MC10H104L price and accurately reduce the harmonic components. Simulation results show that, through the filter, the grid voltage distortion factor dropped to 1.88% (lower than the IEEE-519-1992 standard). The device was 35 kV power grid in the Wuhan Iron and MC10H104L suppliers and Steel arc furnace operation, the results show high reliability of the device, filtering effect is remarkable, with good engineering applications.

Present, power filter and more use of digital controllers, engineers have a higher need for software programming skills. Thus, most of the time filter design cycle will be used for the preparation and optimization of the program. Taking into account the mathematical model, algorithm design, off-line debugging, the development time will be very long, the cost will increase accordingly.

Rapid control model (Rapid Control Prototyping, RCP) design reduces the design cycle, using Simulink graphical programming, eliminating the need for complex programming: For hardware engineers, change the model parameters can be achieved on-site debugging; for theoretical research personnel, the algorithm need only consider the speed and practicality.

Wavelet transform is a non-steady-state analysis of voltage and current waveforms of the fast and effective way. As with the FFT, wavelet transform signal into frequency components. However, the discrete wavelet transform (DWT) with variable frequency resolution, can effectively solve the network load caused by mutations in voltage flicker, and real-time tracking the harmonics. This is used to analyze transient signals a useful feature. In addition, wavelet analysis does not require the entire frequency range at the same time, the calculated amount of concentrated in one frequency range, reducing the computation to speed up the analysis speed. Simulink software

Based on Hybrid Active Power Filter (Hvbrid Active Power Filter, HAPF) model, using Wavelet analysis and simulation of harmonic toolbox from MATLAB / Simulink / Embedded Target for TI C2000 DSP generation code and, ultimately, TMS320F2812 hardware implementation.

1 rapid control model (RCP)

RCP consists of two parts: computer-aided design software with Simulink and proprietary real-time operating system, hardware, TMS320F2812, shown in Figure 1. The graphical programming approach instead of the traditional procedures for the preparation, only requires engineers to focus on the optimization of functionality and performance. This paper presents a complete system simulation environment.


Figure 1 RCP component

Embedded Target for TI C2000 connectivity software and hardware, Simulink toolbox provides all the necessary paper model for general-purpose DSP on the design, simulation and implementation of embedded control system provides the integration platform. Figure 2 shows the design flow.


Figure 2 flow chart

Using Embedded Target, through CCS (Cede Composer Studio) generate efficient DSP code, the host and the DSP of the interface will connect the two to connect to the DSP on-line control and optimization. For the calculation of the need for complex algorithms cycle, RCPs rapid implementation features will reflect the great advantage. In view of power system harmonic wavelet analysis of the prospects, as well as the convenience of modeling, the active part of the filter control algorithms using wavelet transform to analyze the harmonics.

2 Wavelet analysis

2.1 Multiresolution decomposition method

Commonly used wavelet analysis to achieve multi-resolution signal decomposition (Multiresolution Signl Decomposition, MSD), high-pass filter and low-pass filter g h, respectively, the wavelet function to form, as shown in Figure 3.


Figure 3, multi-resolution wavelet analysis of signal decomposition method to achieve

Figure 3 contains the scale of 1 to the Nyquist frequency from 1 / 4 of sampling frequency information, scale 2 contains from 1 / 4 to 1 / 8 sampling frequency information, and other information contained in this scale and so on. Wavelet decomposition can be terminated at any scale, the final smoothing the output contains information on all remaining scales. However, the signal decomposition level is not arbitrary. The signal length N can only be broken down into log2N layer.

2.2 Wavelet Transform

Continuous signal f (t) of the wavelet transform is defined as:


Which, as the mother wavelet, a is scaling factor, b the translation factor. In the time domain is a stretch or shrink depending on a.

In the discrete wavelet transform, we give a number of wavelet coefficients m and n, these coefficients depends on the dilation factor and translation factor of the number of times. The discrete wavelet coefficients can be expressed as:


Although this transformation is time continuous, but discrete wavelet form. Inverse discrete wavelet transform is as follows:


Type (3): K = (A + B) / 2, A and B are a and b, respectively, the maximum (frame value).

For different problems, the choice of the mother wavelet is different, and the mother wavelet selection for the resulting structure has great influence. To ensure that the signal from its wavelet transform coefficients can be reconstructed, with a symmetric wavelet filter coefficients to produce linear phase shift, derived from the Daubechies orthogonal wavelet set wavelet domain coverage.

2.3 model control algorithm to achieve

Simulink toolbox provides a wealth of mathematical models, select from C28xADC, C28x PWM, F2812 eZdsp (if not the module is unable to generate DSP code), DWT and IDWT other modules to form the model shown in Figure 4.


Figure 4 contains the control algorithm model wavelet transform

Which, in the Wavelet subsystem integrates Environment ControRer, Buffer, DWT and IDWT and other modules of the sampling the quantized signal harmonic analysis, and produce compensation voltage command signal, and then output through the PWM control of IGBT turn-off signal , to reduce harmonics and reactive power compensation purposes. The process of simulation, real-time adjustment needed C28x PWM duty cycle to produce the appropriate output waveform.

3 Hybrid Active Power Filter Model

3.1 Hybrid Active Power Filter

Harmonic current of high voltage large capacity is mainly used passive LC resonant filters (Passive Power Filter, PPF), which filters both reactive power compensation. Although the PPF has a small initial investment, operation and higher efficiency, but the filtering effect of PPF by the greater impact on power system impedance, and can only remove a certain number of harmonics, the number of frequent changes to the load harmonic filtering effect is not good.

May also occur with the system resonance, the LC filter is overloaded or destroyed. Active Power Filter (Acfiire Power Filter, APF) is equivalent to a variable resistor of the fundamental impedance is 0, the harmonic having a high impedance state, APF, although able to overcome the shortcomings PPF, but its installed capacity by switching devices capacity constraints.

Passive filters and active filters will be combined constitute a hybrid active power filter (HAPF), active power filter is only used to improve the filtering effect of passive filter and suppress possible resonance. In this way, the active power filter is not exposed to the fundamental voltage AC power, the installed capacity greatly reduced, usually only the total capacity of nonlinear loads about 1 / 10, so that the active power filter can be applied in high power applications.

Large-scale supply and distribution stations usually want to filter out the harmonic reactive power compensation at the same time, the inverter will increase the technical difficulty and cost of implementation, thereby limiting the active power filter in a large substation. Inverter output voltage through the transformer coupled to the passive filter through the filter branch of the inductors and capacitors at both ends, so that neither bear the fundamental active power filter does not bear the fundamental current voltage, thereby greatly reducing the capacity of active power filter.

3.2 Control System Architecture

In the past to control active power filter in part by the industrial computer and single chip form, IPC to achieve harmonic detection, analysis and calculation of control signal, MCU control signals are generated. Limited to the single chip processing speed, this will signal sampling, harmonic analysis and the generation of PWM pulse signals are integrated in the TMS320F2812 completed in full 32-bit DSP computational efficiency. The control circuit shown in Figure 5.


Figure 5, the control circuit structure A phase voltage

been selected as the initial value of zero, after the initial time of three-phase current is measured using Hall sensors, will measure the value into the DSP, through high-speed A / D conversion by sampling value, and then discrete wavelet transform sampling value, the fundamental value of the phase current obtained is1, respectively, minus the three-phase current fundamental value of the sample, that is to be compensated by active power filter harmonic current value of the three-phase ish, to receive compensation for active power filter output voltage command signal U = KIsh. And through the DSPs PWM module control inverter, you can get the desired voltage waveform.

3.3 Hybrid Active Power Filter Simulation Model

Powerful Simulink toolbox contains this series covered all the C2000 DSP algorithms and peripherals, which will undoubtedly facilitate the controller design of the simulation conditions. Hybrid active power filter model shown in Figure 6.


Figure 6 hybrid active power filter model

Three-phase AC voltage source 35 kV, 50 Hz, 500 kVA simulation grid, step-down transformer to 400V, 50Hz. Active filter inverter output voltage through the transformer coupled to the passive filter inductor and capacitor filter branch ends to reduce the capacity of active power filter shown in Figure 7. B1, B2 respectively, measuring instruments, non-linear load composed by a non-symmetrical rectifier.


active filter model of Figure 7

4 results

DC bus capacitance:


Which capacitor rated voltage Vn = Vc/1.83, distribution line apparent power Sn = S * n/0.087, S * n as the capacitor in the f = 50 Hz power.

Minimum filter capacitance:


Formula for harmonic current standard n What value What is the value of the voltage fundamental standard.

According to formula (6) obtained by the filter inductance:


s angular frequency for a determined time. By the above formula, the simulation system parameter values ??obtained in Table 1.

Table 1 System parameter values ??


Current waveform shown in Figure 8 before and after compensation. Can be drawn from the waveform, after filtering and compensating current passive role, be a more accurate three-phase sinusoidal current waveform.


Figure 8 Current waveforms before and after compensation

Through wavelet analysis toolbox for harmonic calculation, analysis, through the hybrid active power filter, the distortion coefficient of 22.50% down to 1.88%, in line with IEEE-519-1992 standard, shown in Figure 9.


Figure 9, A-phase voltage before and after filtering the spectrum

5 Conclusion

Compared with conventional power filter, short design cycle fast control model, the investment cost is low, the filter effect is obvious. Running results show that the rapid establishment of DSP as the controller model can accurately track the load caused by mutations in the grid voltage flicker, and thus the harmonic compensation. The equipment, high reliability, strong anti-interference ability, with good economic, engineering applications for promotion.

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