This paper presents a review of the most popular control and modulation strategies studied for matrix converters (MCs) in the last decade. The purpose of most of these methods is to generate sinusoidal current on the input and output sides. These methods are compared considering theoretical complexity and performance. This paper concludes that the control strategy has a significant impact on the resonance of the MC input filter.

A Review of Control and Modulation Methods for Matrix Converters

In order to solve the parameter dependence problem in model predictive control, an improved model predictive current control (MPCC) method based on the incremental model for surface-mounted permanent-magnet synchronous motor drives is proposed in this paper. First, the parameter sensitivity of a conventional MPCC method is analyzed, which indicates that the parameter mismatches would cause prediction current error and inaccurate delay compensation. Therefore, an incremental prediction model is introduced in this paper to eliminate the use of permanent magnetic flux linkage in a prediction model. Among the parameter of the incremental prediction model, only inductance mismatch contributes to the prediction error, since the influence of resistance mismatch on the control performance is very small. Therefore, in order to improve the antiparameter-disturbance capability of the MPCC method, an inductance disturbance controller, which includes the inductance disturbance observer and inductance extraction algorithm, is presented to update accurate inductance information for the whole control system in real time. Finally, simulation and experimental results both show that the proposed method can effectively eliminate the influence of the parameter mismatches on the control performance and reduce the parameter sensitivity of the MPCC method.

Model Predictive Current Control for PMSM Drives With Parameter Robustness Improvement

Hybrid ac-dc microgrid architecture is attracting special attention since it combines the benefits of both ac and dc systems. Control of hybrid microgrid presents a significant research and engineering challenge and hence needs increased research efforts. This paper attempts to review control strategies that are reported in the literature for the hybrid ac-dc microgrid. At first, typical and emerging hybrid microgrid power topologies are presented briefly. Various types of interlinking converters proposed for connecting ac and dc subgrids are discussed subsequently. Following this, a detailed discussion on control strategies for satisfying various control objectives is taken up. Control strategies have been systematically reviewed focusing on each of the broad aspects of control namely modeling, power management, coordinated control, stability analysis, power quality, and protection strategies. Finally, the research gaps observed during the review process and possible solution approaches are outlined.

Hybrid AC–DC Microgrid: Systematic Evaluation of Control Strategies

Conventional model predictive current control (MPCC) is a powerful control strategy for three-phase inverters that has the advantages of simple concept, quick response, easy implementation, and good performance. However, MPCC is sensitive to machine parameter variation, and the performance degrades substantially if a mismatch exists between the model parameters and real machine parameters. Model-free predictive current control (MFPCC) based on an ultralocal model, which uses only the input and output of the system without considering any motor parameters, has been proposed to solve this problem in this article. Since parameters are not required, the robustness of the control system is improved. However, conventional MFPCC based on an ultralocal model uses many control parameters, which increases the tuning work. Furthermore, the control performance is not ideal at low sampling frequency. This article proposes an improved MFPCC based on the extended state observer of PMSM drives that does not require motor parameters and needs less tuning work and lower computational time while achieving the better performance in terms of current harmonics, tracking error, and dynamic overshoot. The proposed method is compared to conventional MPCC and MFPCC, and the effectiveness is confirmed by the simulation and experimental results.

Model-Free Predictive Current Control of PMSM Drives Based on Extended State Observer Using Ultralocal Model

This paper proposes a new topology of a hybrid ac/dc microgrid, where there are multiple subgrids connected to the common bus by bidirectional ac/dc converters (BADCs) and bidirectional dc/dc converters (BDDCs) in the system The rated ac frequencies in different ac subgrids and the rated dc voltages in different dc subgrids can be different for different applications All the storages in the system are concentrated to form a storage subgrid for convenient management and high efficiency, which maintains the common bus voltage To ensure the hybrid microgrid operates well, a proper power management method is necessary to control the power flow among multiple subgrids This paper proposes a decentralized power management method for the hybrid microgrid to make the interacted subgrids operate in coordination and support each other First, taking the characteristics of the common bus configuration into consideration, a ${P_{{\rm{dc}}}} - v_{{\rm{dc}}}^2$ droop control strategy is proposed to maintain the common bus voltage and to realize power sharing among storages in the storage subgrid Second, as the interaction among multiple subgrids is more complicated compared to the conventional hybrid, a coordinated power control strategy based on the common bus voltage, ac subgrid frequency, and dc subgrid voltage is designed for the BADCs and BDDCs to realize the power interaction among different subgrids Furthermore, the proposed strategy takes the capacities and load types of each subgrid into consideration; hence, it is still suitable when the capacities of subgrids are mismatched and it can ensure the power quality of the subgrids with high proportion of critical loads The effectiveness of the proposed power management method is verified by the real-time hardware-in-loop tests

Power Management for a Hybrid AC/DC Microgrid With Multiple Subgrids

In order to optimize the current-control performance of the permanent-magnet synchronous motor (PMSM) system with model parameter mismatch and one-step control delay, an improved deadbeat predictive current control (DPCC) algorithm for the PMSM drive systems is proposed in this paper. First, the performance of the conventional predictive current control, when parameter mismatch exist, is analyzed, and then a stator current and disturbance observer (SCDO) based on sliding-mode exponential reaching law, which is able to simultaneously predict future value of stator current and track system disturbance caused by parameter mismatch in real time, is proposed. Based on this SCDO, prediction currents are used for replacing the sampled current in DPCC to compensate one-step delay, and estimated parameter disturbances are considered as the feedforward value to compensate the voltage reference calculated by deadbeat predictive current controller. Thus, a composite control method combining the DPCC part and current prediction and feedforward compensation part based on SCDO, called DPCC + SCDO method, is developed. Moreover, based on conventional exponential reaching law, a novel sliding-mode exponential reaching law is proposed to further improve the performance of the DPCC + SCDO method. Simulation and experimental results both show the validity of the proposed current control approach.

Deadbeat Predictive Current Control of Permanent-Magnet Synchronous Motors with Stator Current and Disturbance Observer

Today, interests on hybrid ac/dc microgrids, which contain the advantages of both ac and dc microgrids, are growing rapidly. In the hybrid ac/dc microgrid, the parallel-operated ac/dc bidirectional interfacing converters (IFCs) are increasingly used for large capacity renewable energy sources or as the interlinking converters between the ac and dc subsystems. When unbalanced grid faults occur, the active power transferred by the parallel-operated IFCs must be kept constant and oscillation-free to stabilize the dc bus voltage. However, under conventional control strategies in unbalanced grid conditions, the active power transfer capability of IFCs is affected due to the converters’ current rating limitations. Moreover, unbalanced voltage adverse effects on IFCs (such as output power oscillations, dc-link ripples, and output current enhancement) could be amplified by the number of parallel converters. Therefore, this paper investigates parallel operation of IFCs in hybrid ac/dc microgrids under unbalanced ac grid conditions and proposes a novel control strategy to enhance the active power transfer capability with zero active power oscillation. The proposed control strategy employs a new current sharing method which introduces adjustable current reference coefficients for parallel IFCs. In the proposed control strategy, only one IFC, named as redundant IFC, needs to be designed and installed with higher current rating to ensure the constant and oscillation-free output active power of parallel IFCs. Simulation and experimental results verify the feasibility and effectiveness of the proposed control strategy.

Parallel Operation of Bidirectional Interfacing Converters in a Hybrid AC/DC Microgrid Under Unbalanced Grid Voltage Conditions

In order to integrate renewable energy into the utility grid with high penetration, AC/DC hybrid microgrids have obtained much attentions in recent years since they feature both advantages of AC microgrids and DC microgrids. In an AC/DC hybrid microgrid, the parallel-operated AC/DC bi-directional interfacing converters (IFCs) are key elements to connect AC bus and DC bus. When unbalanced grid faults occur at the AC bus, the active power transferred by the parallel-operated AC/DC interfacing converters is desired to be maintained constant and oscillation-free to ensure the stable operation of DC bus. However, with conventional control strategies in unbalanced grid conditions, the active power transfer capability of IFCs will be affected due to the current rating limitations. Therefore, the parallel operation of IFCs in a hybrid microgrid under unbalanced AC grid conditions is studied, and a control strategy, which enhances the active power transfer capability with zero active power oscillation, is proposed. Adjustable reference current coefficients for parallel IFCs are introduced in the proposed control strategy to enable the flexible current sharing among IFCs. By utilizing the proposed control strategy, only one IFC needs to be designed and installed with higher current rating to ensure the constant and oscillation-free output active power. Simulations and experiments have verified the feasibility and effectiveness of the proposed strategy.

Parallel operation of bi-directional interfacing converters in a hybrid AC/DC microgrid under unbalanced grid conditions

In order to satisfy the requirements of common leg for both motors at the same time, an optimized modulation method is proposed for a five-leg voltage source inverter for dual Induction motor drives. In this method, pulse widths of voltage vectors are calculated according to space vector pulse width modulation (SVPWM) theory, and the distribution of vectors is adjusted and optimized, especially the extra zero vectors are considered and inserted while the needs of the common leg for both motors collide. Simulation results show that two motors operate at different speeds with different loads, which means the five-leg-inverter is controlled effectively by using the proposed method. Moreover, compared with the conventional half-cycle PWM method, switching frequency of the inverter is reduced and the driving capability of the dual induction motor drive system fed by a five-leg-inverter is improved by the proposed method.

An optimized modulation method for a five-leg-inverter for dual Induction motor drives

Three-phase to single-phase matrix converter (3-1 MC) is a direct AC power conversion device to feed single phase AC facilities and supplied by three phase generator or grid lines, also can be considered as a part of conventional three-phase to three-phase matrix converter (3-3 MC). Different from 3-3 MC, space vector modulation can not be applied on 3-1 MC directly. In order to realize sinusoidal output current, a improved low frequency switching function modulation strategy based on Alesina-Venturini theory is proposed for 3-1 MC. Experimental tests have been carried out on a 3kW 3-1 MC prototype, which demonstrate the feasibility and validity of proposed modulation strategy. Reverse blocking IGBT (RB-IGBT) is employed to construct bi-directional switches in 3-1 MC prototype for power loss reduction.

Yang Mei

Papers

Deadbeat Predictive Current Control of Permanent-Magnet Synchronous Motors with Stator Current and Disturbance Observer

Parallel Operation of Bidirectional Interfacing Converters in a Hybrid AC/DC Microgrid Under Unbalanced Grid Voltage Conditions

Parallel operation of bi-directional interfacing converters in a hybrid AC/DC microgrid under unbalanced grid conditions

An optimized modulation method for a five-leg-inverter for dual Induction motor drives

Improved switching function modulation strategy for three-phase to single-phase matrix converter