Direct Power Control With Space Vector Modulation Research Articles

Voltage sensorless based virtual flux control of three level NPC back-to-back converter dfigunder grid fault

In this paper, a harmonic elimination of grid and stator currents of doubly fed induction generator (DFIG) in case of grid fault without line voltage sensors is proposed . This can be achieved by compensating power based on virtual flux voltage sensorless technique. Direct power control with space vector modulation (DPC-SVM) is used to control both grid-side (GSC)and rotor-side converters (RSC). To achieve the control objective, compensated active and reactive powers are calculated based on virtual flux technique with balanced and harmonic free current as a control target. A theoretical analysis of active and reactive powers under unbalanced voltage source is clearly demonstrated and the effect of grid fault on the performance of DFIG is profoundly discussed. Simulation results verified the effectiveness of the modified control strategy.

Direct Power Control of Pulsewidth Modulated Rectifiers Without DC Voltage Oscillations Under Unbalanced Grid Conditions

Direct power control with space vector modulation (DPC-SVM) features simple structure, fast dynamic performance, and little tuning work. However, the conventional DPC-SVM cannot achieve accurate power control under unbalanced grid conditions. A modified DPC-SVM is thus proposed for accurate power control under both ideal and unbalanced grid conditions. Though the power control accuracy is improved when compared with the conventional DPC-SVM, it still suffers highly distorted grid current and dc voltage oscillations with an unbalanced network. Therefore, a power compensation method is subsequently derived aiming at the following targets: eliminating dc voltage oscillations, achieving sinusoidal grid current, and obtaining unity power factor. To that end, average grid-side reactive power and oscillations in converter-side active power are controlled as zero by simply adding a compensation to original power reference. Additionally, the proposed method does not require extraction of a positive sequence or negative sequence component of grid voltage. Compared with the conventional DPC-SVM in an ideal grid, only additional compensation of power reference is required. As a result, control performance can be significantly improved without substantial increase in complexity. The superiority of the proposed method over the prior DPC-SVM is validated by both simulation and experimental results obtained on a two-level pulsewidth modulation voltage source rectifier.

Direct Power Control of Three-phase Voltage Source Converters Using Feedback Linearization Technique

This paper describes the direct power control (DPC) of a three-phase voltage source converter (VSC) using feedback linearization technique. This technique transforms nonlinear model of the VSC into a linear one so that the controller design is easy and independent of the operating point. The problem is formulated in the DPC framework. The DPC with space-vector modulation (DPC-SVM) is adopted because of its constant switching frequency operation. The control scheme is implemented on a STM32F4DISCOVERY board. The validity of the scheme has been verified through experiment which shows that the proposed control strategy provides the VSC operation with wide operating range and fast transient responses.

Study on DPC-SVM Rectifier Based on Power Feedforward

In this paper, on the basis of the mathematic model of the three-level PWM rectifier, a power feedforward based control strategy is proposed combining with direct power control with space vector modulation (DPC-SVM) control principle. Feedforward control can reduce or even eliminate the impact on the system causing by load disturbance to improve dynamic performance. The simulation results show that the control method makes the system response speed faster and the dynamic performance better, it largely improved the system rectifier capacity against load disturbances.

DSP-Based Control of Grid-Connected Power Converters Operating Under Grid Distortions

Power electronic Grid-Connected Converters (GCCs) are widely applied as grid interface in renewable energy sources. This paper proposes an extended Direct Power Control with Space Vector Modulation (DPC-SVM) scheme with improved operation performance under grid distortions. The real-time operated DPC-SVM scheme has to execute several important tasks as: space vector pulse width modulation, active and reactive power feedback control, grid current harmonics and voltage dips compensation. Thus, development and implementation of the DPC-SVM algorithm using single chip floating-point microcontroller TMS320F28335 is described. It combines large peripheral equipment, typical for microcontrollers, with high computation capacity characteristic for Digital Signal Processors (DSPs). The novelty of the proposed system lies in extension of the generic DPC-SVM scheme by additional higher harmonic and voltage dips compensation modules and implementation of the whole algorithm in a single chip floating point microcontroller. Overview of the laboratory setup, description of basic algorithm subtasks sequence, software optimization as well as execution time of specific program modules on fixed-point and floating-point processors are discussed. Selected oscillograms illustrating operation and robustness of the developed algorithm used in 5 kVA laboratory model of the GCC are presented.