Design of isolated inverter power supply based on Matlab

Based on Matlab software platform, the inverter source designed by double loop control strategy is modeled and simulated by Matlab-Simulink-SimPowerSystems toolbox, which verifies the feasibility and effectiveness of the design scheme.

0 Preface

With the development of renewable energy such as solar energy and wind energy, distributed power generation has become a hotspot of research in various countries due to its advantages of less environmental pollution, high energy comprehensive utilization and reliable power supply. It is mature in the United States and Europe. Countries and regions to apply them widely in the microgrid. As an effective power supply source, inverter power has become an important part of microgrid, and has been widely used in the research and implementation of microgrid.

The PWM-based isolated inverter power supply designed in this paper adopts voltage outer loop and current inner loop double loop control strategy. Both voltage outer loop and current inner loop adopt PI control mode. The Matlab software was used to establish the experimental model for simulation. The rationality of the control system design scheme and the application effect of the double loop control strategy were verified by simulation. The simulation results proved the rationality and effectiveness of the system design scheme.

1 PWM inverter circuit structure and working principle

In the AC-DC-AC inverter, the DC circuit is usually required to adopt a thyristor rectifier circuit, as shown in Figure 1(a). The magnitude of the voltage Uo of the inverter output can be controlled by changing the size of Ud. The frequency of the output voltage Uo can be changed by controlling the frequency of the inverter trigger circuit. However, this type of frequency conversion circuit has drawbacks: if the output AC voltage is a rectangular wave containing more harmonics, this is disadvantageous for the load or the AC grid; if the output power is adjusted by the phase control method, The input power factor is reduced, and the large capacitance is present in the intermediate DC ring, so that the inertia is large when the input power is adjusted, and the system response is slow.

In order to solve the above drawbacks, an inverter circuit as shown in Fig. 1(b) can be employed. This kind of circuit is usually called PWM (Pulse Width Modula-TIon) type frequency conversion circuit. The basic working principle is to control the on/off of the switching device in the inverter circuit regularly, so that the output end can be equal in width. Pulse trains, and use these pulse trains instead of sine waves. Modulating the pulse widths of the pulse train according to the required rules can change the output voltage of the circuit and change the frequency of the output voltage.

Figure 1 AC-DC-AC inverter circuit

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