Discrete Space Vector Modulation Research Articles

Modified MPC with extended VVs for grid‐connected rectifier

This article presents an alternative finite control set model predictive control (FCS-MPC) implementation to reduce the input current ripple of a two-level three-phase grid-connected rectifier. With the proposed approach, an improvement in the input current ripple is obtained by integrating the virtual vectors in the conventional FCS-MPC structure. The synthesis of the virtual vector is conceptualised from the discrete space vector modulation approach which combines several switching states during the sampling period to create new virtual voltage vectors. However, with this approach, the number of voltage vectors becomes higher, making it challenging to implement this algorithm in a standard control platform. To overcome this problem, a two-stage optimisation method is proposed to optimise the voltage vector selection process, avoiding evaluating all the feasible voltage vectors without any performance sacrifice. Experimental results are presented; showing that the proposed technique provides lower input current ripple compared to the conventional FCS-MPC with an acceptable computational effort.

Drive Direct Torque Control of Permanent Magnet Synchronous Motors Based on Discrete Space Vector Modulation

To solve the problems of unsmooth stator flux linkage locus, large torque ripples and big power loss in conventional direct torque control system of permanent magnet synchronous motor, the discrete space vector modulation technique is analyzed, and a new direct torque control method (DSVM-DTC) is proposed in this paper. PI controller and DSVM modulator are used to instead hysteresis controller and switch table in conventional DTC system, which increased the equivalent voltage vectors and selected accurate zero vectors in different sectors. Therefore, the errors of flux and torque can be compensated accurately. Simulation results prove that DSVM-DTC effectively improved the steady-state performance of the system, declined the switching loss, reduced torque ripple, and flux linkage locus is more smooth under the premise of ensuring constant switching frequency.

Deadbeat Model-Predictive Torque Control With Discrete Space-Vector Modulation for PMSM Drives

This paper proposes an alternative strategy of finite-control-set model-predictive torque control (MPTC) to reduce the computational burden and the torque ripple and decouple the switching frequency from the controller sampling time. An improved discrete space-vector modulation (DSVM) technique is utilized to synthesize a large number of virtual voltage vectors. The deadbeat (DB) technique is used to optimize the voltage vector selection process, avoiding enumerating all the feasible voltage vectors. With this proposed method, only three voltage vectors are tested in each predictive step. Based on the improved DSVM method, the three candidate voltage vectors are calculated by using a novel algebraic way. This new strategy has the benefits of both the MPTC method and the DB method. The effectiveness of the proposed strategy is validated based on a test bench.

Direct Torque Control of Induction Motors Based on Discrete Space Vector Modulation Using Adaptive Sliding Mode Control

—Direct torque control (DTC) with space vector modulation (SVM) ensures constant switching frequency and high-performance operation, both in the steady state and under transient conditions. This article is devoted to the presentation of a comparison study between two DTC-SVM approaches for electric propulsion systems applications: (i) DTC-SVM with controllers, and (ii) DTC-SVM with sliding mode controllers. Following the formulation of both DTC-SVM approaches, their implementation in the Matlab-Simulink environment has been treated. The transient behavior as well as the steady state features of the drive system under both approaches are compared and commented. The robustness with respect to parameter variations of the induction motor drive is also tested. Simulation results show the effectiveness and the robustness of the proposed DTC-SVM adaptive sliding mode control against variations of induction motor parameters.

Study on Direct Torque Control of Brushless Doubly-Fed Machine Based on Discete Space Vector Modulation

The paper introduces Working mode of brushless doubly-fed machine（BDFM） and mathematical model in the d-q coordinates for BDFM，a strategy of discrete space vector modulation in direct torque control for BDFM has been Proposed 。The paper uses Matlab / Simulink to model and simulate the system of the direct torque control for brush double-fed motor based on discrete Space Vector Modulation.Simulation results prove that the discrete space vector modulation technique can reduce the torque ripple of traditional direct torque control system for BDFM, and improve waveform of current and Flux of Control winding.

Minimization of powers ripple of direct power controlled DFIG by fuzzy controller and improved discrete space vector modulation

This paper presents a new direct power control (DPC) strategy for a double fed induction generator (DFIG) based wind energy generation system. The strategy of the discrete space vector modulation (DSVM) that is on the basis of the DPC, is implemented. The algorithm to select voltage vector can effectively change the response of the system. So, a new analysis is done and a new switching table is proposed. The proposed switching table is presented to optimize the performance of the voltage vectors by accurately designing the sequence of the voltage vectors. Rearranging the sequence of the voltage space vectors has an influence on active power ripple. To enhance the performance of the closed loop system, fuzzy system is proposed in place of the switching table and hysteresis system. The four variables, rotor speed, errors of the active and reactive powers and stator flux position are exerted to the fuzzy system and the output is the vector that should be implemented to the switching devices. The outperformance of the proposed method is demonstrated by performing simulations in Matlab Software.

A new control strategy for small wind farm with capabilities of supplying required reactive power and transient stability improvement

Abstract This paper presents a new control strategy for a small scale wind farm which is composed of both fixed and variable speed wind turbine generator systems. Fixed speed wind generators (FSWGs) are largely dependent on reactive power, so they require large reactive power when a short circuit fault occurs in the power system. Otherwise the FSWGs become unstable and have to be disconnected from the power system. In this paper, a new wind farm topology is considered, where series connected fixed speed WTGs are installed with variable speed wind turbine (VSWT) driven by doubly fed induction generators (DFIGs). A new direct power control (DPC) strategy based on discrete space vector modulation (DSVM) technique is applied for DFIG-based wind turbine system. No extra power or current control loops are required, simplifying the system design and improving transient performance. Simulation results clearly show that the proposed topology is a cost effective solution and simplified system design to minimize voltage fluctuation of both fixed and variable speed WTGs as well as to improve the transient stability of the wind farm.

Direct power control of DFIG based on discrete space vector modulation

This paper presents a new direct power control (DPC) strategy for a double fed induction generator (DFIG) based wind energy generation system. Switching vectors for rotor side converter were selected from the optimal switching table using the estimated stator flux position and the errors of the active and reactive power. A few number of voltage vectors may cause undesired power and stator current ripple. In this paper the increased number of voltage vectors with application of the Discrete Space Vector Modulation (DSVM) will be presented. Then a new switching table in supersynchronous and subsynchronous frames will be proposed. Simulation results of a 2 MW DFIG system demonstrate the effectiveness and robustness of the proposed control strategy during variations of active and reactive power, machine parameters, and wind speed.

Minimization of torque ripple of direct-torque controlled induction machines by improved discrete space vector modulation

In this paper, discrete space vector modulation (DSVM) technique for induction machine drives is developed, and then a fuzzy logic direct torque control (DTC) scheme based on the proposed DSVM technique is presented. In DSVM technique, new voltage vectors are synthesized by applying three standard voltage space vectors for three equal time intervals at each sampling period. Rearranging the sequence of the three voltage space vectors does not change final synthesized voltage vectors, but has an influence on torque ripple. By comparing torque waveforms in one sampling period, an analysis is carried out to determine the influence. Based on the analysis, new switching tables used in DSVM-DTC are defined. In the switching tables, the three components of each synthesized voltage vector are arranged in optimized sequence. Finally, a fuzzy logic controller is designed to select synthesized voltage vectors. Its control rules are established based on the proposed switching tables. The proposed scheme is verified by simulations. Simulation results show that a reduction of torque ripples is achieved in a whole speed range.

Implementation of a direct control algorithm for induction motors based on discrete space vector modulation

The basic concept of direct torque control of induction machines is investigated in order to emphasize the effects produced by a given voltage vector on stator flux and torque variations. The low number of voltage vectors which can be applied to the machine using the basic DTC scheme may cause undesired torque and current ripple. An improvement of the drive performance can be obtained using a new DTC algorithm based on the application of the space vector modulation (SVM) for prefixed time intervals. In this way a sort of discrete space vector modulation (DSVM) is introduced. Numerical simulations and experimental tests have been carried out to validate the proposed method.