Predictive Control algorithm to achieve power balance of Cascaded H-Bridge converters (original) (raw)
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Predictive Control of Cascaded H-Bridge Converters Under Unbalanced Power Generation
IEEE Transactions on Industrial Electronics, 2016
This work presents a predictive control strategy for grid-connected Cascaded H-Bridge (CHB) converters under unbalanced power generation among each converter phase. The proposed controller belongs to the Finite-Control-Set Model Predictive Control (FCS-MPC) family and is designed to extract unbalanced power from each CHB converter phase while providing balanced power to the grid. The key novelty of this strategy lies in the way the unbalanced power generation among the phases is explicitly considered into the optimal control problem. Power balance is achieved by enforcing the CHB converter to work with a suitable zero-sequence voltage component. The proposed predictive controller is directly formulated in the original abc-framework to account for the commonmode voltage. Simulation and experimental results are provided to verify the effectiveness of the proposed FCS-MPC strategy.
Modulated Model Predictive Control for a Seven-Level Cascaded H-Bridge Back-to-Back Converter
IEEE Transactions on Industrial Electronics, 2014
Multilevel Converters are known to have many advantages for electricity network applications. In particular Cascaded H-Bridge Converters are attractive because of their inherent modularity and scalability. Predictive control for power converters is advantageous as a result of its applicability to discrete system and fast response. In this paper a novel control technique, named Modulated Model Predictive Control, is introduced with the aim to increase the performance of Model Predictive Control. The proposed controller address a modulation scheme as part of the minimization process. The proposed control technique is described in detail, validated through simulation and experimental testing and compared with Dead-Beat and traditional Model Predictive Control. The results show the increased performance of the Modulated Model Predictive Control with respect to the classic Finite Control Set Model Predictive Control, in terms of current waveform THD. Moreover the proposed controller allows a multi-objective control, with respect to Dead-Beat Control that does not present this capability.
Model predictive control for Cascaded H-bridge multilevel inverters with even power distribution
2010 IEEE International Conference on Industrial Technology, 2010
In this work, a suitable long prediction horizon (multistep) model predictive control (MPC) formulation for cascaded H-bridge inverters is proposed. The MPC is formulated to include the full steady-state system information in terms of output current and output voltage references. Generally, basic single-step predictive controllers only track the current references. As a distinctive feature, the proposed MPC also tracks the control input references, which in this case is designed to minimize the common-mode voltage (CMV). This allows the controller to address both output current and CMV targets in a single optimization. To reduce the computational effort introduced by a long prediction horizon implementation, the proposed MPC formulation is transformed into an equivalent optimization problem that can be solved by a fast sphere decoding algorithm. Moreover, the benefits of including the control input references in the proposed formulation are analyzed based on this equivalent optimization problem. This analysis is key to understand how the proposed MPC formulation can handle both control targets. Experimental results show that the proposal provides an improved steady-state performance in terms of current distortion, inverter voltages symmetry, and CMV.
Predictive control algorithm technique for multilevel asymmetric cascaded H-bridge inverters
Industrial Electronics, IEEE …, 2008
Predictive control algorithms have been proposed for power electronic converters, featuring a high performance in terms of dynamic behavior. This is true due mainly to the accurate modeling and the finite set of inputs or possible switching combinations. However, when it is used in multilevel converters, the dynamic performance is degraded, because the optimization algorithm needs to evaluate and search over a large number of possible switching combinations. In this paper, a predictive control algorithm, which exhibits high dynamic performance for multilevel converters, is proposed. The algorithm reduces the complexity of calculations and the number of possible combinations, allowing the use of predictive control with a large number of switching states. Experimental results on a 27-level asymmetric multicell converter, which validate the proposed algorithm, are presented.
Electronics
The multilevel back-to-back cascaded H-bridge converter (CHB-B2B) presents a significantly reduced components per level in comparison to other classical back-to-back multilevel topologies. However, this advantage cannot be fulfilled because of the several internal short circuits presented in the CHB-B2B when a conventional PWM modulation is applied. To solve this issue, a powerful math tool known as graph theory emerges as a solution for defining the converter switching matrix to be used with an appropriate control strategy, such as the model-based predictive control (MPC). Therefore, this research paper proposes a MPC with the graph theory approach applied to CHB-B2B which capable of not only eliminating the short circuit stages, but also exploring all the switching states remaining without losing the converter controllability and power quality. To demonstrate the proposed strategy applicability, the MPC with graph theory approach is tested in four different types of SST configurat...
Model Predictive Control of Multilevel Cascaded H-Bridge Inverters
IEEE Transactions on Industrial Electronics, 2010
This paper presents a model predictive current control algorithm that is suitable for multilevel converters and its application to a three-phase cascaded H-bridge inverter. This control method uses a discrete-time model of the system to predict the future value of the current for all voltage vectors, and selects the vector which minimizes a cost function. Due to the large number of voltage vectors available in a multilevel inverter, a large number of calculations are needed, making difficult the implementation of this control in a standard control platform. A modified control strategy that considerably reduces the amount of calculations without affecting the system's performance is proposed. Experimental results for five-and nine-level inverters validate the proposed control algorithm.
An improved method of model predictive current control for multilevel cascaded H-bridge inverters
Journal of Electrical Engineering
Finite control set ModelPredictive control (FCS-MPC) with the principle of considering all voltage vectors to find the optimal voltage vector for multilevel inverter in a very small sampling cycle is hardly feasible because there is no modulation part, the implementation of optimizing common-mode voltage and switching number for the multilevel inverter should be performed in the cost function. To solve the above problem, this paper proposes an improved method of model predictive current control selecting 19 adjacent voltage vectors and using weighting coefficients for common-mode voltage elimination and switching optimization. By using a discrete-time model of the system to predict the future value of the current for the voltage vector in the previous sampling cycle and its 18 adjacent voltage vectors, the one that minimizes a cost function will be selected. Thus, in a multilevel inverter with any number of levels, the cost function is performed only 19 times in a sampling cycle. Th...
Model predictive-based control method for cascaded H-Bridge multilevel active rectifiers
… and Exposition (ECCE) …, 2011
The cascaded H-Bridge multilevel active rectifier is an emerging converter topology, which offers significant advantages, such as modularity and high flexibility for a wide range of applications, including traction systems, industrial automation plants, uninterruptable power supplies, and battery chargers. However, the need for stable operation of the H-Bridge cells at asymmetrical voltage potentials and unbalanced loads imposes demanding requirements, in terms of an advanced and accurate control strategy. This paper introduces a simple and powerful solution to the mentioned problems, based on constrained Model Predictive Control (MPC). The proposed nonlinear controller achieves low input current harmonic distortion with almost unity power factor, as well as independent regulation of the H-Bridge cells, both under steady state and transient conditions. The effectiveness of the novel control algorithm is demonstrated by means of simulations as well as preliminary experimentation on a single-phase laboratory setup.
IECON 2011 - 37th Annual Conference of the IEEE Industrial Electronics Society, 2011
The selective harmonic elimination (SHE) strategy is specially well suited for high-power applications where the power losses must be kept below strict limits. The SHE technique is based on offline calculations and the generation of a preprogrammed voltage waveforms eliminating some low order harmonics. An evolution of SHE is the selective harmonic mitigation (SHM) technique which is based on pre-programmed waveforms non eliminating the low order harmonics but reducing the distortion below the limits imposed by a grid code. However, the main drawback of these pre-programmed SHE and SHM techniques is a low dynamic performance. In a recent paper, an online SHE technique based on the model predictive control (MPC) has been presented improving the dynamic performance of the conventional SHE method. In this paper, the online version of the SHM technique is introduced. It is based also in the MPC strategy and has been tested in a cascaded multilevel converter obtaining a high performance with very low switching frequency.
In this paper, a model predictive control strategy is adapted to the cascaded H-bridge (CHB) multilevel rectifier. The proposed control scheme aims to keep the sinusoidal input current in phase with the supply voltage and to achieve independent voltage regulation of the H-bridge cells. To do so, the switches are directly manipulated without the need of a modulator. Furthermore, since all the possible switching combinations are taken into account, the controller exhibits favorable performance not only under nominal conditions but also under asymmetrical voltage potentials and unbalanced loads. Finally, a short horizon is employed in order to ensure robustness; this way, the required computational effort remains reasonable, making it possible to implement the algorithm in a real-time system. Experimental results obtained from a two-cell CHB rectifier are presented in order to demonstrate the performance of the proposed approach.