Combined voltage oriented control and direct power control based on backstepping control for four-leg PWM rectifier under unbalanced conditions

The present paper proposes a combined voltage-oriented control and direct power control (VOC-DPC) method associated with the backstepping control technique for a three-phase four-wire grid-connected four-leg rectifier in the synchronous rotating frame without using phase locked loop (PLL) and Parks transformation under balanced and unbalanced load and grid conditions. This control method is proposed in order to remove the drawbacks of the conventional VOC based on the PLL technique .The proposed control method is able to enhance the control performance and dynamic responses of the system when considering slow dynamics and instability issues of the PLL in several cases and can decrease the computational burden due to the absence of PLL and Park transformation. In addition, the performance of the proposed VOC-DPC method is enhanced by using backstepping control (BSC) based on Lyabonov theory for both the input currents and DC-bus voltage loops. As a consequence, constant DC-bus voltage, unit power factor, sinusoidal input currents, and neutral current minimization can be accurately carried out under both DC-bus voltage and load variations. Furthermore, robustness against filter inductance variations can also be achieved. The effectiveness, superiority, and performance of the proposed control method for a four-leg rectifier based on BSC in the dq0-frame are validated by several processor-in-the-loop (PIL) co-simulation tests sing the STM32F407 discovery development board

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

Design of new robust backstepping control for three-phase grid-connected fourleg source voltage PWM converters

Due to high performance demands of grid-connected pulse-width modulation (PWM) converters in power applications, backstepping control (BSC) has drawn wide research interest for its advantages, including high robustness against parametric variations and external disturbances. In order to guarantee these advantages while providing high static and dynamic responses, in this work, a robust BSC (RBSC) with consideration of grid-connected PWM converter parameter uncertainties is proposed for three-phase grid-connected four-leg voltage source rectifiers (GC-FLVSR). The proposed RBSC for GC-FLVSR is composed of four independent controllers based on the Lyabonov theory that control DC bus voltage and input currents simultaneously. As a result, unit power factor, stable DC-bus voltage, sinusoidal four-leg rectifier input currents with lower harmonics and zero-sequence (ZS), and natural currents can be accurately achieved. Furthermore, the stability and robustness against load, DC capacitor, and filter inductance variations can be tested. The effectiveness and superiority of the proposed RBSC compared to the PI control (PIC) have been validated by processor-inthe- loop (PIL) co-simulation using the STM32F407 discovery-development-board as an experimental study

GWO-super-twisting integral sliding mode control of 60 KW PV system based on interleaved boost converter

The energy provided by the PV system is strongly influenced by climatic conditions such as solar radiation and cell temperature. A suitable DC /DC converter and a robust control strategy combined with the maximum power point tracking (MPPT) algorithm are required to harness the maximum power of the panel. This paper proposes a super-twisting integral sliding mode control (ST-ISMC) for four legs interleaved boost converter (FLIBC) as an interface to the MPPT algorithm for a 60 KW PV system. The FLIBC has been used to overcome the drawbacks of the conventional boost converter (CBC). The ST-ISMC is proposed to maintain the PV voltage track the reference provided by the MPPT algorithm and ensure the equal sharing of input current between legs. The controller gains of the proposed ST-ISMC have been calculated using the grey wolf optimization algorithm for better performance. The simulation results prove the excellent performance of the proposed controller over the conventional controller

Sliding mode controller for four leg shunt active power filter to eliminating zero sequence current, compensating harmonics and reactive power with fixed switching frequency

In this paper, the four leg inverter controlled by the three dimensional space vector modulation (3D SVM) is used as the shunt active power filter (SAPF) for compensating the three phase four wire electrical network, by using the four leg inverter with 3D SVM advantages to eliminated zero sequence current, fixed switching frequency of inverter switches, and reduced switching losses. This four leg inverter is employed as shunt active power filter to minimizing harmonic currents, reducing magnitude of neutral wire current, eliminating zero sequence current caused by nonlinear single phase loads and compensating reactive power, and a nonlinear sliding mode control technique (SMC) is proposed for harmonic currents and DC bus voltage control to improve the performances of the three phase four wire four leg shunt active power filter based on Synchronous Reference Frame (SRF) theory in the dq0 axes, and to decoupling the four leg SAPF mathematical model

Genetic algorithm-super-twisting technique for grid-connected PV system associate with filter

This study proposes an intelligent robust controller to improve the performance of the multifunctional grid-connected photovoltaic (PV) system using the phase-locked loop (PLL). The novelty of this research is the use of a new strategy, called super-twisting algorithm (STA) based on genetic algorithm (GA) to improve the performance of the direct power control (DPC) with PLL technique and maximum power point tracking (MPPT), where DPC-STA-GA is used to control the active power filter. This proposed nonlinear technique is used to increase the power quality of the PV system under different conditions (variation of the nonlinear load, random nature of the irradiance solar and temperature,…etc). On the other hand, the STA-GA controller is successfully applied to control the DC link voltage of the multi-functional voltage source inverter. Durability and ease of implementation are among the most prominent features of the DPC-STA-GA with PLL technique to reduce the reactive and active power ripples compared to the DPC technique. The suggested intelligent nonlinear control ensures the harmonic current compensation and the transmission of PV energy to the electric grid and or the nonlinear load with high quality. To implement and verify the proposed controls with the PLL technique, Matlab software is used for this purpose, with the study of the behavior of the proposed controls based on STA-GA controllers with the PLL compared with the DPC in different conditions. The simulation results demonstrated the contribution of the DPC-STA-GA with the PLL in improving the performance, efficiency, effectiveness, and durability of the system under normal and abnormal conditions, where the proposed control reduced overshoot value in DC bus voltage by 100% compared to proportional-integral controller. In addition to reducing the value of THD of current compared to DPC and DPC-STA by 18.82% and 43.33%, respectively, in the case of solar radiation equal 1000 W/m2

Improved DTC strategy of doubly fed induction motor using fuzzy logic controller

International audienceThis paper presents an improved Direct Torque Control (DTC) strategy for a Doubly Fed Induction Machine (DFIM) powered by two voltage source inverters (VSI) at two levels. This strategy is based on the fuzzy logic controller. The main objective is to improve the performance of the system by reducing electromagnetic torque ripples and improving the currents shape by optimization of the total harmonic distortion (THD). The hysteresis regulators and voltage vectors selection table of the conventional DTC are replaced by fuzzy logic blocks to realize fuzzy DTC control. The two control strategies are simulated in the MATLAB/SIMULINK environment followed by a comparative analysis to validate the effectiveness of the proposed strategy. Many improvements in term of rise time, torque ripples, flux ripples and current harmonics have been done, namely stator and rotor flux ripple and torque ripple have been reduced more than 50%, 69.2% and 47.7% respectively. The stator and rotor currents THD have been reduced around 84.5% and 84.3% respectively