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[Introduction] In this article, Xiaobian will introduce the more important control system part of the inverter power supply, and use the combination of graphics and text to help readers understand the principle and design ideas of the inverter power supply. Let's see.
In this article, Xiaobian will introduce the more important part of the control system in the inverter power supply. The combination of graphics and texts will help readers understand the principle and design ideas of the inverter power supply. Let's take a look at it with Xiaobian. .

Figure 1 is a schematic diagram of a DSP-based inverter system control scheme. If the system introduces an inductor current inner loop, it not only increases the stability of the system, but also appropriately reduces the resonance peak. Therefore, adding a current inner loop inside the outer loop of the repetitive control voltage to form a repeated control double loop can increase the stability of the repetitive control system and reduce the design difficulty of the compensator.

2 is a structural block diagram of a digital control system. The system analog part is mainly the power circuit and interface circuit, the digital part. The interface circuit needs special consideration when designing. It needs to realize data conversion (A/D, D / A). For different A/D, it is necessary to specially set the level conversion circuit. The gate drive circuit not only provides enough energy to drive the power module, but also needs isolation to protect the digital chip. Finally, digital control is achieved by programming the digital part.

According to the internal model principle, the basis of the repetitive control design is that the controlled system is stable, and then the repeated internal modes are added to obtain the static-free characteristics of periodic input or interference. Designing a repetitive control system requires knowing the exact model of the controlled system so that a compensator that satisfies the stability domain relationship can be designed. The system after adding the repeat controller is shown in Figure 3.

In Figure 1, T is the fundamental period; S(s) is the compensator to be designed; Gp(s) is the average model of the controlled system, ie, equation (3).
In order to simplify the analysis, the filter series equivalent series resistance rL and the filter capacitor equivalent series resistance rc are ignored, and the Kvf, Utr, Ud constant gain links are regarded as unit gain, and the average model of the inverter simplified to unit feedback can be obtained, namely:

The open-loop transfer function of the repetitive control system can be obtained from Figure 1:

Due to the existence of the pure delay link e-Ts, it is difficult to implement in the simulation, and it needs to be discretized, so that the analysis method of the discrete system is adopted. Where e-Ts=zN, N is the number of samples in one fundamental wave. Q is used to improve the critical stability characteristics of the internal parameters of the repeating controller. It can be a parameter slightly lower than l or a low-pass filter. The comparison between the constant type Q and the function type has a higher gain in the low frequency range. The state characteristic will be more ideal, but it can be seen that it will introduce phase shift. Therefore, it is necessary to design phase compensation for it. The design is not good, the system may be unstable, but the expected stability compensation effect is not achieved. Therefore, In the usual design, constant Q = 0.95 is often chosen for simplified design.
This paper explains the part of the inverter-based power supply control circuit based on DSP, and helps the beginners to strengthen the understanding of the inverter power supply through the illustrated method. Friends who are interested in inverter power supply may wish to spend a few minutes reading this article, I believe there will be unexpected gains.