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Through mathematical methods, the small power switching power supply system represents a mathematical model and a nonlinear control model to establish a simulation model of a system of switching power supply, which improves the simulation speed. MATLAB is a senior mathematical analysis software. SIMULINK is a software package running in a MATLAB environment for modeling, simulating, and analyzing a dynamic system, which supports continuous, discrete, and mixed linear and nonlinear systems.
The power system toolbox is introduced in Matlab 5.2, which can be used in conjunction with SIMULINK, which can easily simulate the power electronics. With the development of power technology, PWM controlled switching power supplies have been widely studied and applied, such as communication power supplies, locomotive power, etc. Here is a 220 V high-frequency switching power source to establish a model. The power supply uses a pulse width modulation control method to achieve multiple indicator requirements such as weight, reduction volume, improvement accuracy, and is very representative in system model research of switching power supplies. The main circuit uses the DC-HFAC-DC-LFAC structure and uses Matlab to create a discrete, nonlinear model. The system is opened and closed, and the simulation results are compared and analyzed.
1 circuit schematic
The principle of circuit is shown in Figure 1.
2 simulation circuit
The simulation model of each sub-module in Fig. 2 is shown in Figs. 3 to 10. The simulation parameters of the system are: DC boost circuit simulation parameter setting: operating frequency ∫ = 20 kHz; transformer ratio k = 13; output filter L = 8 μH, C = 300 / μF. Full bridge inverter circuit simulation parameter setting: operating frequency f = 25 kHz, output filter L = 80 MH, C = 100 μF. Here, set the corresponding simulation parameters for simulation debugging.
2.1 Modeling of input loop
The power module of the power system toolbox and the resistance capacitor module can be easily established simulation model of the input loop. Entering the two-stage LC DC input filtering technology, while ensuring steady-state filtering effect, it limits the transient resonance peak, with no power, high attenuation, controllable resonance peak.
2.2 Modeling of DC-DC circuit
As can be seen from Fig. 1, the rectifier diode in the output circuit cannot flow through the reverse current, which is also a nonlinear link to establish a nonlinear mathematical model.
2.2.1 Modeling of DC-DC Main Circuit
According to Figure 1, the current inductance inductance is:
Where: UI is an output voltage of an inconsistent rectified; UF is a load voltage; UL is inductive voltage; load voltage is:
Where: UC capacitor voltage; IL is inductive current; IC is a capacitor current; LF is a load current.
2.2.2 Modeling of PI regulator
Proportional Integral Regulator Simulation Model (PI) is shown in Figure 5.
The output waveform of the PI regulator is shown in Figure 6.
2.2.3 Modeling of the PWM controller
The simulation utilizes the integral relationship to generate triangular waves, and SOURINK has a pulse generator (Pulsegenerator), which produces a frequency of 20 kHz, a magnitude of 4104, a duty cycle of 50%.
2.3 Modeling of inverter circuit
The inverter circuit simulation model (Inverter) is shown in Figure 9.
2.3.1 Modeling of the PI regulator
The proportional integral regulator simulation model (P11) is shown in Figure 10, and its output waveform is shown in FIG.
2.3.2 SPWM modeling
Sine Width Modulation Model Simulation Module (SPWM) is shown in Figure 12.
2.4 Modeling of output loop
Output and Display Module Simulation Model (OUTPUT) is shown in Figure 13.
3 simulation results
Establish a Sireulink system simulation model, the simulation model sets the simulation time 0.3 s, and selects the ODEL5 algorithm that will be changed. When the input voltage is 48 V, the load is the rated load, the startup simulation can obtain its output waveform, output voltage waveform The diagrams and THD spectrum are shown in Figures 14 and 15.
3.1 open loop simulation
The open loop simulation is shown in Figure 14.
3.2 closed-loop simulation
The closed loop simulation is shown in Figure 15.
As can be seen from the spectrum analysis, the total harmonic coefficient (THD) is 3.02%, and the three harmonic content is relatively large. When closed loop, the total harmonic coefficient (THD) is 0.07%, and there is very little harmonic content. As can be seen from the voltage waveform, the voltage output waveform in the open loop reaches stable in the third cycle, and when the closed loop has reached stable in the second cycle, the voltage reaches the voltage when the closed loop reaches the speed than the opening ring. quick.
4 knot
This model can not only be used to examine the transient change process within the main state of the system, but also to analyze and design control loops. This has a practical significance and research value for improving the performance of the control system. Improve the modeling of the switching power supply system with the mathematical method, the selection of simulation time is 0.3 s, and complete the simulation as long as 40 s, not only avoiding the ultimate simulation speed of other tools, but also improves the reliability of simulation. Sireulink is a powerful dynamic simulation tool for controlling system simulation, achieving system control easy, and simple structural model. , Reading the full text, the technology area
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