A Model-Based Direct Power Control for Three-Phase Power Converters

Direct Power Control (DPC) technique has been widely used as control strategy for three-phase power rectifiers due to its simplicity and good performance. The DPC uses the instantaneous active and reactive power to control the power converter, the controller design has been proposed as a direct control with a look up table (LUT), and in recent works, as an indirect control with an inner control loop with proportional plus integral controllers for the instantaneous active and reactive power errors. In this paper a model-based DPC for three-phase power converters is designed, obtaining expressions for the input control signal which allow to design an adaptive control law minimizing the errors introduced by the parameters uncertainties as the smoothing inductor value or the grid frequency. Controller design process, stability study of the system and experimental results for a synchronous three-phase power rectifier prototype are presented to validate the proposed controller

Matrix Converter-Based Unified Power-Flow Controllers: Advanced Direct Power Control Method

This paper presents a direct power control (DPC) for three-phase matrix converters operating as unified power flow controllers (UPFCs). Matrix converters (MCs) allow the direct ac/ac power conversion without dc energy storage links; therefore, the MC-based UPFC (MC-UPFC) has reduced volume and cost, reduced capacitor power losses, together with higher reliability. Theoretical principles of direct power control (DPC) based on sliding mode control techniques are established for an MC-UPFC dynamic model including the input filter. As a result, line active and reactive power, together with ac supply reactive power, can be directly controlled by selecting an appropriate matrix converter switching state guaranteeing good steady-state and dynamic responses. Experimental results of DPC controllers for MC-UPFC show decoupled active and reactive power control, zero steady-state tracking error, and fast response times. Compared to an MC-UPFC using active and reactive power linear controllers based on a modified Venturini high-frequency PWM modulator, the experimental results of the advanced DPC-MC guarantee faster responses without overshoot and no steady-state error, presenting no cross-coupling in dynamic and steady-state responses

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

Direct Power Control By Using Matrix Converter Based UPFC

This paper describes direct power control (DPC) by using Matrix converter based Unified power flow controller (UPFC). The basic problems of UPFC’s are discussed, however this paper proposes an alternative solution for direct power control using a direct ac-ac converter called a matrix converter. The pulse width modulation control technique developed and presented in this paper is based on space vector approach. This paper presents the complete space vector model of a three phase to three phase matrix converter topology. Theoretical principles of direct power control (DPC) based on sliding mode control techniques are established for a matrix converter based UPFC dynamic model including the input filter. Matrix converters (MCs) allow the direct ac-ac power conversion without dc energy storage links, matrix converter is a bidirectional power flow converter that uses semi converter switches arranged in the form of matrix array. Therefore, the matrix converter based unified power flow controller (MC-UPFC) has reduced cost, capacitor power losses and volume with higher reliability By selecting an appropriate matrix converter switching state, line active and reactive power, together with ac supply reactive power, can be directly controlled, and guaranteeing good steady-state and dynamic responses. The line active and reactive power linear controllers based on a modified Venturini high-frequency PWM modulator compared with direct power controller (DPC) by using MC-UPFC; guarantee faster responses without overshoot , presenting no cross-coupling in dynamic and steady-state responses and no steady state error. Experimental results of direct power controllers for MC based UPFC shows decoupled active and reactive power control and fast response times

Model based adaptive direct power control for three-level NPC converters

In this work, a Model Based Adaptive Direct Power Control (MB-ADPC) with constant switching frequency for Three-Phase Three-Level Neutral Point Clamped (3L-NPC) converters is proposed. The rectifier and inverter operation mode are used to illustrate the flexibility of the proposed MB-ADPC controller. The control design process is based on the continuous averaged model of the system. Depending on the operation mode different control objectives have to be guaranteed. The proposed controller ensures the voltage regulation of the dc-link capacitors for the rectifier operation mode and to achieve voltage balance in the dc-link capacitors and the active and reactive power tracking for the rectifier and inverter operation modes. In addition, adaptive techniques are used to avoid system parameters uncertainties as smoothing inductors and grid frequency values. This work shows that the application of advanced control strategies based on the system model allows enhancing the performance of the overall system. The details of the controllers design process and the experimental results using a 50 kVA Three-Phase Three-Level NPC prototype are presented in this paper validating the proposed controllers

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

Sequential model predictive control of direct matrix converter without weighting factors

© 2018 IEEE. The direct matrix converter (MC) is a promising converter that performs direct AC-to-AC conversion. Model predictive control (MPC) is a simple and powerful control strategy for power electronic converters including the MC. However, weighting factor design and heavy computational burden impose significant challenges for this control strategy. This paper investigates the sequential MPC (SMPC) for a three-phase direct MC. In this control strategy, each control objective has an individual cost function and these cost functions are evaluated sequentially based on priority. The complex weighting factor design process is not required and the computational burden can be reduced. In addition, specifying the priority for control objectives can be achieved. A comparative simulation study with standard MPC is carried out in Matlab/Simulink. Control performance is compared to the standard MPC and found to be comparable. Simulation results verify the effectiveness of the proposed strategy

Stability analysis of VSC-HVDC system based on new phase-locked-loop less voltage oriented control method

Voltage Source Converters-based High Voltage Direct Current (VSC-HVDC) systems are generally implemented to transmit power across long distances due to their low cost and flexibility. This paper will discuss a new simple and low-computational-burden phase-locked loop less voltage-oriented control strategy (PLL-less-VOC strategy) for controlling and synchronizing a VSC-HVDC system in a synchronous rotating frame (dq frame). The proposed method is used not only to control the VSC-HVDC but also to obtain the mathematical model of both VSCs-based HVDC systems in the dq frame using the basics of the direct instantaneous power control theory (DPC) without using PLL and Park transformations. The proposed PLL-less-VOC strategy is equivalent to the conventional VOC strategy for steady-state stability, but it has the benefit of both conventional VOC and DPC, better transient stability performance, and low computational burden in the implementation. The experimental tests using STM32F407G microcontroller demonstrate that the proposed control strategy has better dynamic stability under certain exceptional conditions such as step changes on DC-link voltage change, powers change, and three-phase fault

Modelling and Control Design of Pitch-Controlled Variable Speed Wind Turbines

This chapter provides an overall perspective of modern wind power systems, including a discussion of major wind turbine concepts and technologies. More specifically, of the various wind turbine designs, pitch-controlled variable speed wind turbines controlled by means of power electronic converters have been considered. Among them, direct-in-line wind turbines with full-scale power converter and using direct-driven permanent magnet synchronous generators have increasingly drawn more interests to wind turbine manufactures due to its advantages over the other variable-speed wind turbines. Based on this issue, major operating characteristics of these devices are thoroughly analyzed and a three-phase grid-connected wind turbine system, incorporating a maximum power point tracker for dynamic active power generation is presented. Moreover, a simplified state-space averaged mathematical model of the wind turbine system is provided. An efficient power conditioning system of the selected wind turbine design and a new three-level control scheme by using concepts of instantaneous power in the synchronous-rotating d-q reference frame in order to simultaneously and independently control active and reactive power flow in the distribution network level are proposed. Dynamic system simulation studies in the MATLAB/Simulink environment is used in order to demonstrate the effectiveness of the proposed multi-level control approaches in d-q coordinates and the full detailed models presented. The fast response of power electronic devices and the enhanced performance of the proposed control techniques allow taking full advantage of the wind turbine generator.Fil: Molina, Marcelo Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Mercado, Pedro Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; Argentin