Abstract
Finite control set model predictive control (FCS-MPC) is able to handle multiple control objectives and constraints simultaneously with good dynamic performance. However, its industrial application is limited by its high dependence on system model and the huge computational effort. In this paper, a novel robust two-layer MPC (RM-MPC) with strong robustness is proposed for the full-bridge neutral-point clamped (NPC) voltage mode Class-D amplifier (CDA) aiming at this problem. The errors caused by the parameter mismatches or uncertainties of the LC filter and the load current are regarded as lumped disturbance and estimated by the designed Luenberger observer. The robust control can be achieved by compensating the estimated disturbance to the used predictive model. In order to reduce computation of the controller, a two-layer MPC is proposed for the full-bridge NPC inverter with an LC filter. The first layer is used to calculate the optimal output level which minimizes the tracking error of the output voltage. The second layer is used to determine the switching state for the purpose of capacitor voltage balancing. The experimental results show that the lumped model error is observed centrally through only one observer with low complexity. The two-layer MPC further reduced the computation without affecting the dynamic performance.
Highlights
In the area of industrial measurement, testing, and process technology, there exist many applications of power amplifiers in order to generate current and voltage signals of special shape at high power levels. [1,2]
In [18], the model predictive control (MPC) based on optimal switching sequences was proposed for the full-bridge neutral-point clamped (NPC) inverter, which could achieve fixed switching frequency for the switch devices
The errors caused by the parameter mismatches or uncertainties of the LC filter and the load current are regarded as lumped disturbance and estimated by the designed Luenberger observer
Summary
In the area of industrial measurement, testing, and process technology, there exist many applications of power amplifiers in order to generate current and voltage signals of special shape at high power levels. [1,2]. In [18], the MPC based on optimal switching sequences was proposed for the full-bridge NPC inverter, which could achieve fixed switching frequency for the switch devices This method failed to balance the capacitor voltage [19]. Layered structure is used in the proposed robust MPC, so that the output voltage tracking and the capacitor voltage balancing can be achieved simultaneously and decoupled without affecting the dynamic performance, and the required computation can be further reduced. 2. Modeling of the Voltage Mode Amplifier Using Full-Bridge NPC Inverter the CDA is established. Assuming that UC1 and UC2 are well balanced, the differential equation of the full-bridge NPC inverter-based voltage mode amplifier can be obtained as Equation (1) from Figure 1, based on the Kirchhoff’s laws of voltage and current.
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