Abstract
The application of the finite control set model predictive control to cascaded inverters is severely limited by its computational complexity. In this paper, a load observer based multilayer model predictive control is proposed for the voltage mode digital power amplifier employing cascaded full-bridge neutral point clamped inverter, which can avoid the use of load current sensor and greatly reduce the controller computation without affecting its dynamic performance. The discrete mathematical model of the voltage mode digital power amplifier employing cascaded full-bridge neutral point clamped inverter is established with filter inductor current and filter capacitor voltage as state variables. A load current observer is designed based on this to avoid the use of load current observer. Based on the discrete model and the observed load current, the upper layer of the multilayer model predictive control determines the optimal level that minimizes the cost function. The middle layer allocates the optimal level to each submodule in order to achieve capacitor voltage balancing. The lower layer determines the switching state of each submodule in order to reduce switching actions. Finally, the experimental results based on the designed nine-level prototype show that the develop multilayer model predictive control lead to acceptable steady state, dynamic and robust performance, with only 1.37% of the run time of the traditional model predictive control.
Highlights
Power amplifiers are widely used in industrial testing and measurement [1]
Compared with two-level or three-level inverter, cascaded inverter, such as cascaded H-bridge inverter [5], modular multilevel converter [6] and cascaded full-bridge neutral point clamped inverter (CFNPCI) [7], has the advantages of high power, low step voltage and step current, strong fault handling ability, modular structure and high output waveform quality; it is often employed by high power digital power amplifiers
A low complexity multilayer MPC (MMPC) is proposed in Se divides multiple control objectives of the digital power amplifier system middle and lower layers
Summary
Power amplifiers are widely used in industrial testing and measurement [1]. They are often used to drive underwater acoustic transducers to produce low-frequency tunable sound sources, which can realize submarine navigation and ranging [2]. In [11], a new MPC which selects two voltage levels in a single control period is proposed to reduce the computation burden for cascaded H-bridge inverter. A multilayer MPC (MMPC) is proposed for the voltage mode digital power amplifier employing CFNPCI, which can completely avoid the cyclic calculation and comparison of the cost function without affecting the system dynamic performance, greatly reducing the amount of calculation of the controller. In order to avoid the use of Electronics 2021, 10, 1699 load current sensor, a load observer is designed, which can est current online On this basis, a low complexity MMPC is proposed in Se divides multiple control objectives of the digital power amplifier system middle and lower layers.
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