Application of DSP repetitive control technology in inverter power supply system

Jacktang

Application of DSP repetitive control technology in inverter power supply system [Copy link]

This paper proposes a DSP repetitive control scheme, which uses a repetitive controller to track the periodic reference command signal, reduce the output voltage harmonics, and improve the dynamic performance of the system through current loop control. According to this control scheme, a single-phase 1kW inverter based on DSP TMS320LF2407A control is designed and debugged. Both simulation and experimental results verify the good performance of this scheme.

　　Basic theory of repetitive control
　　Repetitive control is a control concept based on the internal model principle. Its internal model mathematical model describes a periodic signal, thus enabling the closed-loop control system to track the periodic signal without static error. A single-frequency sine wave is a typical periodic signal, and its mathematical model is:

　　Then, as long as a sinusoidal signal with the same frequency as the input is connected in series to the controller forward channel, the system can achieve zero static error tracking. Repetitive control also uses digital control. The internal model of the repetitive control after discretization is:

　　Where: N is the number of samples in one cycle
　　The forward channel of the ideal repetitive control system based on the internal model principle contains a periodic delay link, which inevitably leads to poor dynamic performance. So far, there are two most effective methods to achieve high-performance control effects: one is direct repetitive control, which introduces feedforward and improves dynamic response through feedforward. Its system structure is shown in Figure 1; the other is embedded repetitive control, which adds a PI regulator on the repetitive controller side and improves dynamic performance through PI regulation. Its system structure is shown in Figure 2.

The ideal repetitive controller Q(z)=l, when the angular frequency ωd of the disturbance is an integer multiple of the angular frequency ωr of the input signal, that is, ωd=nωr, zN=1 can be obtained, that is, the ideal repetitive controller can eliminate any harmonics and can track any harmonics less than 1/2 of the sampling frequency without difference. Therefore, the controller proposed in this paper suppresses periodic interference by repeating the internal model to achieve steady-state characteristics, and PI control provides dynamic compensation. This controller takes into account the advantages of simple design and convenient implementation of PI classical control, while making up for the disadvantage of single-cycle delay of repetitive control.

　　Inverter control system design
　　Figure 3 is a schematic diagram of the inverter system control solution based on DSP. If the system introduces an inductor current inner loop, it can not only increase the stability of the system, but also appropriately reduce the resonance peak. Therefore, adding a current inner loop inside the repetitive control voltage outer loop to form a repetitive control double loop can increase the stability of the repetitive control system and reduce the difficulty of compensator design.

　　The analog part of the system mainly consists of the power circuit, interface circuit and digital part. The interface circuit needs special consideration during design. It needs to realize data conversion (A/D, D/A). For different A/D, a level conversion circuit needs to be specially set. The gate drive circuit not only needs to provide enough energy to drive the power module, but also needs isolation to protect the digital chip. Finally, digital control is realized through the programming of the digital part.

alan000345

Learned, very good