Multi-functional model predictive control with mutual influence elimination for three-phase AC/DC converters in energy conversion

© 2019 by the authors. Conventional model predictive control (MPC)-based direct power control of the three-phase full-bridge AC/DC converter usually suffers from the parametric coupling between active and reactive powers. A reference change of either the active or reactive power will influence the other, deteriorating the dynamic-state performance. In addition, the steady-state performance affected by one-step-delay arising from computation and communication processes in the digital implementation should be improved in consideration of switching frequency reduction. In combination with the proposed novel mutual influence elimination constraint, this paper proposes the multi-functional MPC for three-phase full-bridge AC/DC converters to improve both the steady and dynamic performances simultaneously. It has various advantages such as one-step-delay compensation, power ripple reduction, and switching frequency reduction for steady-state performance as well as mutual influence elimination for dynamic capability. The simulation and experimental results are obtained to verify the effectiveness of the proposed method

Advanced multi-functional model predictive control for three-phase AC/DC converters

© 2016 The Institute of Electrical Engineers of Japan. With the conventional model predictive control (MPC) based direct power control of three-phase AC/DC converters, the active and reactive powers can be simultaneously controlled by a single cost function. A change in parameters of either the active or reactive power within the cost function will affect the other, leading to poor dynamic performance of transient response. Besides, the steady state performance of the conventional MPC is affected by one-step-delay of digital implementation. This paper proposes an advanced multi-functional MPC of three-phase full-bridge AC/DC converter for high power applications. It has multiple functions such as one-step-delay compensation, power ripple reduction, switching frequency reduction, and dynamic mutual influence elimination. Using the proposed modified cost function, both the steady state and dynamic performances of the converter can be improved. Finally, the simulation results are reported to validate the advancement of the proposed control strategy in comparison with other control methods

Modeling, Analysis and Control of DC Hybrid Power Systems.

All electric ships are featured with integrated power systems which combine electric propulsion technology with heterogeneous power generation and distribution technologies to form one single electrical platform. The auxiliary and main power generation system form an isolated hybrid power system to feed the ship service loads and to meet the propulsion power requirement. Although for decades, the methodologies for power converter control have been explored in many publications, the modeling, analysis, and control of hybrid power systems with multiple power converters remains an interesting open problem, leading to its exclusive focus in this dissertation. Along with the opportunities introduced by hybrid power systems, the inter-connectivity and complexity represent a major system analysis, design and optimization challenge, calling for the development of effective tools. Therefore, a comprehensive testbed is developed. Moreover, component level modeling, analysis and modulation strategy development are performed to ensure system level performance. A new power flow model for the dual active bridge converter is derived. The new model provides a physical interpretation of the observed phenomena and identifies other characteristics that are validated by experiments. To overcome the drawbacks of traditional modulation strategies, a novel modulation strategy is developed for the dual active bridge converter. The experimental results verified that, if the new strategy is used to modulate the dual active bridge converter, this testbed can be used as an effective tool for optimal power management algorithm development for the hybrid power systems. The development of advanced control algorithms, together with the increased computational power of microprocessors, enables us to deal with the control problem from a new perspective. In this dissertation, the voltage regulation problem for a full bridge DC/DC converter is formulated as both a linear and a nonlinear Model Predictive Control (MPC) problem with a nonlinear constraint that captures the peak current protection requirement. The experimental results reveal that both the MPC algorithms can successfully achieve voltage regulation and peak current protection. The successful implementation of the MPC schemes on the full bridge DC/DC converter paves the way for future system-level advanced control algorithm development for hybrid power systems.Ph.D.Naval Architecture & Marine EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/75813/1/yhxie_1.pd

Adaptive reference model predictive control for power electronics

An adaptive reference model predictive control (ARMPC) approach is proposed as an alternative means of controlling power converters in response to the issue of steady-state residual errors presented in power converters under the conventional model predictive control (MPC). Differing from other methods of eliminating steady-state errors of MPC based control, such as MPC with integrator, the proposed ARMPC is designed to track the so-called virtual references instead of the actual references. Subsequently, additional tuning is not required for different operating conditions. In this paper, ARMPC is applied to a single-phase full-bridge voltage source inverter (VSI). It is experimentally validated that ARMPC exhibits strength in substantially eliminating the residual errors in environment of model mismatch, load change, and input voltage change, which would otherwise be present under MPC control. Moreover, it is experimentally demonstrated that the proposed ARMPC shows a consistent erasion of steady-state errors, while the MPC with integrator performs inconsistently for different cases of model mismatch after a fixed tuning of the weighting factor

Comparison of single-phase matrix converter and H-bridge converter for radio frequency induction heating

This paper compares the newly developed single-phase matrix converter and the more conventional H- bridge converter for radio frequency induction heating. Both the converters exhibit unity power factor, very low total harmonic distortion at the utility supply interface, good controllability under soft switching condition for a wide range of power, and high efficiencies, whilst still having simple structures. A novel switching control pattern has been proposed for the matrix converter in order to maintain the comparable performance to the H-bridge converter. Simulation and experimental results for both converters are presented. Comparisons between two converters have confirmed the excellent performance of the proposed matrix converter

Analysis and mitigation of dead time harmonics in the single-phase full-bridge PWM converters with repetitive controllers

In order to prevent the power switching devices (e.g., the Insulated-Gate-Bipolar-Transistor, IGBT) from shoot through in voltage source converters during a switching period, the dead time is added either in the hardware driver circuits of the IGBTs or implemented in software in Pulse-Width Modulation (PWM) schemes. Both solutions will contribute to a degradation of the injected current quality. As a consequence, the harmonics induced by the dead time (referred to as "dead time harmonics" hereafter) have to be compensated in order to achieve a satisfactory current quality as required by standards. In this paper, the emission mechanism of dead time harmonics in single-phase PWM inverters is thus presented considering the modulation schemes in details. More importantly, a repetitive controller has been adopted to eliminate the dead time effect in single-phase grid-connected PWM converters. The repetitive controller has been plugged into a proportional resonant-based fundamental current controller so as to mitigate the dead time harmonics and also maintain the control of the fundamental frequency grid current in terms of dynamics. Simulations and experiments are provided, which confirm that the repetitive controller can effectively compensate the dead time harmonics and other low-order distortions, and also it is a simple method without hardware modifications

System configuration, fault detection, location, isolation and restoration: a review on LVDC Microgrid protections

Low voltage direct current (LVDC) distribution has gained the significant interest of research due to the advancements in power conversion technologies. However, the use of converters has given rise to several technical issues regarding their protections and controls of such devices under faulty conditions. Post-fault behaviour of converter-fed LVDC system involves both active converter control and passive circuit transient of similar time scale, which makes the protection for LVDC distribution significantly different and more challenging than low voltage AC. These protection and operational issues have handicapped the practical applications of DC distribution. This paper presents state-of-the-art protection schemes developed for DC Microgrids. With a close look at practical limitations such as the dependency on modelling accuracy, requirement on communications and so forth, a comprehensive evaluation is carried out on those system approaches in terms of system configurations， fault detection, location, isolation and restoration