Direct power control of a DFIG fed by a two level inverter using SVM algorithm

This paper discusses an existing Direct Power Control algorithms for three-phase three-level with neutral-point clamped (NPC) rectifiers. Direct Power Control, or DPC, implies the creation of the control algorithm in order to directly control both the active and reactive powers consumed by the rectifier, increasing the grid's power factor and reducing its current total harmonic distortion. Throughout this document, we will focus on one control algorithm directly related to DPC, through which we can achieve the rectifier control. The chosen method is the virtual flux based on DPC with space vector modulation. We will develop the mathematical model stemming from this algorithm and its operation under variable load. These tests and implementations will allow us to assert the superiority of virtual flux DPC with space vector modulation algorithm over conventional control techniques, verify the results obtained through the studied literature, and demonstrate the capacity of the algorithm to abide by the requirements and constraints. These tests will valorize, when working with medium to high power loads, the advantages of a multi-level inverter.

Modulation strategy plays an important role in the good performance of modular multilevel converter (MMC). Since MMC has a special structure as well as a large number of submodules (SMs), it is almost impossible to apply the conventional multilevel space vector modulation (SVM) algorithm in it. In this study, a simplified SVM implementation method is proposed by grouping SMs. With the presented method, the high‐level SVM process for MMC can be easily done by implementing multiple two‐level or three‐level SVM algorithm, while the complicated offline or online efforts/tasks about mapping switching states or sequences in the conventional multilevel SVM are not necessary any more. In order to improve the harmonic characteristics, the sampling time of different subunits (SUs), each of which is formed by grouping a few SMs, is staggered evenly, which helps to achieve a higher equivalent switching frequency and less low‐order harmonics. Further, the capacitor voltage balance of SMs is improved by rotation strategies between SUs or inside each SU even without any capacitor voltage detecting or sorting. Since the presented method is independent of the number of SMs, it can be very easily expanded into a high‐level MMC. These propositions are verified by experiment.

The variable-speed wind turbines are gaining more prominence due to their ability to generate power for a wide range of wind speeds. This class of turbines requires a fraction of the power be drawn from the grid in order to deliver the promised power when there is a deficiency in wind speed. For this purpose, a Doubly-Fed Induction Generator (DFIG) with a bidirectional converter (AC-DC-AC) on the rotor side is employed. The back-to-back converter controls the flow of energy from the machine to the grid and vice-versa. The Direct Power Control algorithm is used to control the power delivered by the stator to the grid. In this paper, the Space Vector Modulation (SVM) technique using the PI-controllers is used for controlling active and reactive powers. The SVM algorithm triggers the power electronic devices of the converter resulting in improved input current waveform. The paper discusses the simulation results of 1.5 MW DFIG machine connected to the grid via back-to-back converter.

This paper presents a direct power control (DPC) method for a doubly-fed induction generator (DFIG) used in variable-speed wind power systems, combining sliding mode control (SMC) with space vector modulation (SVM). The proposed SMC-based DPC with SVM (SMC-DPC_SVM) achieves decoupled power control through flux orientation, enhancing performance through the robustness of SMC and the precision of SVM. Simulation results demonstrate the effectiveness of this control strategy. The conventional direct power control (C-DPC) approach delivers fast and robust power response, and a comparative analysis between C-DPC and the proposed SMC-DPC_SVM strategy highlights the advantages of the latter. Robustness was evaluated under varying machine parameters, confirming system stability. The proposed control method was implemented and validated using MATLAB/Simulink, achieving a total harmonic distortion (THD) of less than 5%, indicating high-quality power delivery to the electrical grid.

This paper deals with direct control of active and reactive powers in a doubly fed induction generator (DFIG). The stator flux space vector is firstly estimated in the stationary reference frame and then transformed to the rotor reference frame. The suitable rotor voltage space vector is calculated using a switching table based on the errors in stator active/reactive powers. The ordinary direct power control (DPC) method uses six active voltage vectors together with two zero vectors. It suffers from variable switching frequency. The proposed method uses the space vector modulation scheme to supply the rotor with optimal voltage vectors in order to minimize the power errors. Simulations are performed to compare the proposed DPC method with the ordinary method, which show the superiority of the proposed method in terms of lower power ripple and Total Harmonic Distortion (THD).

Sliding mode direct power control of RSC for DFIGs driven by variable speed wind turbines

• A new water pumping system configuration is proposed, based on the DFIG. • The Fuzzy INC MPPT technique is used to extract the maximum power available from the PV array, while the TSR-based MPPT optimizes the available wind energy; • Advanced FDTC control to enhance the dynamic performances by minimizing the stator flux and torque ripple of the SCIM. • Proposing an energy management algorithm employing the self-powering feature of the DFIG to charge the batteries. This paper introduces a promising structure incorporating renewable energies to meet the water needs of a small-scale manufacturing system. The innovative design provides a continuous water supply. The proposed configuration is an effective and eco-friendly solution for the water pumping application. This novel structure includes a Variable Wind Energy Conversion System (VWECS) based on a Doubly Fed Induction Generator (DFIG), a Photovoltaic (PV) system, and batteries serve as a storage unit. Furthermore, the Squirrel Cage Induction Motor (SCIM) is used to drive the centrifugal pump in the water pumping system. Moreover, an Energy Management System (EMS) is proposed to ensure the seamless synergy among all the components of the new structure. The particularity of this latter includes the unique feature of self-powering of the DFIG. The stator power is employed in the DC bus to fulfill the energy requirement in the deficiency mode. This allows the batteries to recharge even in the case of a deficiency. Additionally, the proposed algorithm supervises the batteries to avoid deep discharges and excessive overcharges. On the other hand, Advanced non-linear techniques such as Fuzzy Twelve Direct Torque Control (F12DTC) and Fuzzy Twelve Direct Power Control (F12DPC) are applied to the back-to-back inverter instead of the conventional methods, Direct Torque Control (DTC) and Direct Power Control (DPC) to enhance the dynamic performances of the two-level back-to-back converter in terms of the ripples and Total Harmonic Distortion (THD) shortcomings of the controlled variables (torque, flux, active and reactive powers) by the combination of the Fuzzy Logic controller (FLC), and the twelve sector methodology for accurate voltage selection. In addition, the DTC exhibits significant ripples of the stator torque and the flux magnitudes in the water pumping system. Therefore, the Fuzzy Direct Torque Control (FDTC) is used to drive the SCIM. The powerful tool FLC is employed to replace the hysteresis controllers and handle uncertainties of the controlled variables. The simulation findings by MATLAB/Simulink demonstrate the effectiveness and robustness of the EMS in decision-making and utilize the self-powering feature to recharge the batteries. In addition, successfully supervises the batteries in the optimal range of 20 % and 90 %. Thus, extending the life span and reducing the depth of charge of the batteries. Finally, the simulation results validate the higher performance of the proposed advanced techniques in mitigating the drawbacks of the conventional methods. The F12DTC technique reduces rotor flux and torque ripples by 68 % and 67 %, respectively. The F12DPC ensures efficient power control, minimizing active and reactive power ripples to over 50 % with a minimum total harmonic distortion of 1.69 % for the grid side converter currents, which conforms to the IEEE 519 standards.

This paper proposes a new direct power control (DPC) for wind turbine system driven by permanent synchronous generator (PMSG) in order to track maximum absorbable power in different wind speeds. The desired optimum power is determined for per wind speed by lookup table. Then new direct power control (DPC) employs second order sliding mode(SOSM) nonlinear controller for robust control of active and reactive power and obtaining maximum power from wind turbine. Also constant switching frequency and required pulse for converters is achieved by using space vector modulation (SVM). Simulation results on 5.7-kw wind turbine are provided. Results show that the proposed controller has low error for tracking maximum power in presence wind speed variation.

This paper proposes a direct virtual power control algorithm based on the direct power control with space vector modulation (DPC-SVM) for offshore wind farm connected VSC converter. This control algorithm extends the scope of the traditional DPC. By introducing the virtual power, the DPC can work before the wind farm starts up when the AC side of VSC is open and the voltage stability is achieved as well. The calculation of the algorithm is simple by using most of the original DPC-SVM modules. It maintains the controller structure unchanged before and after the wind farm starts up. The correctness and effectiveness of the proposed control algorithm is verified through simulation in PSCAD/EMTDC software.

The Chapter “AC‐DC‐AC converters for distributed power generation systems” is devoted to various topologies of AC‐DC‐AC converters and its components design. List of presented topologies are: classical three‐phase/three‐phase transistor‐based AC‐DC‐AC converters (2‐level and 3‐level Diode Clamped Converters (DCC) and Flying Capacitors Converters (FCC)), and simplified AC‐DC‐AC converters (2‐level and 3‐level three‐phase/one‐phase and three‐phase/three‐phase DCC). All presented topologies are compared briefly.The space vector modulation and control algorithms are selected and described. Solutions for DC‐link capacitors voltage balancing in DCC and flying capacitors voltage balancing in FCC are presented. Then, an approach related with controllers (machine side converter: flux, torque, and speed; grid‐side converter: current, power, DC‐link voltage) design are given. Finally, an improvement of power flow dynamics between machine‐side converter and grid‐side converter are proposed by active power feed‐forward (APFF) loop. The APFF allows for 10 times reduction of the DC‐link capacitance and provides better active power flow control accuracy in the AC‐DC‐AC converter. The laboratory results example is presented for control algorithm Direct Power and Torque Control with Space Vector Modulations of AC‐DC‐AC converter with APFF.

This paper presents a new fuzzy direct power control of double-fed induction generators (DFIG) in the wind power system. The most important issue in the application of DFIG generators is proper control of the active and reactive powers of these generators, which are generally carried out by vector control or direct torque/power control methods. Direct power control (DPC) directly controls the active and reactive powers of the stator, and stems from results from direct torque control. To use the vector control method, it is necessary to use conventional PI controllers the main disadvantage being the controller robustness due to the nonlinear behavior of the wind turbine and blade oscillations, and it is unavoidable that after a while, the controller's coefficients need to be updated. Therefore, the main purpose of this paper is to present a direct power control method based on fuzzy construction to overcome the mentioned problem. Simulation results of the proposed strategy are extracted under different performance conditions, and these results are compared with the conventional vector-oriented control method. These comprehensive results exhibit the effectiveness of the proposed fuzzy DPC method for the DFIGs based wind power systems.

In this article, we present two techniques of commands DTC (direct torque control) and DPC (direct power control), applied to in the system for converting wind energy with storage. The use of the wind generator is based on a double fed induction Generator (DFIG) where the stator is connected directly to the network and the rotor is connected to the network through the power converter. The Flywheel Energy Storage System (FESS) based on a flywheel, an induction machine (IM) and an electronic power converter is associated with the wind generator via the DC bus. The two converters side DFIG and the (FESS) are controlled by the DTC. The three-level converter side electricity grid which ensures constant DC bus voltage is controlled by the DPC. In the literature, this control strategy has been frequently used for the two levels converter. The direct control of these systems has purpose to eliminate the block of pulse width modulation and loops of regulations internal controlled variables. The use of switching table makes the system more efficient from the technical and economic view.

The study suggests a comprehensive approach to modeling and controlling variable-speed wind turbine systems that utilize doubly fed induction generators (DFIGs). To make sure that energy is transferred efficiently between the DFIG rotor and the grid, a two-level inverter with perfect bidirectional switches is used. Using the tip speed ratio algorithm and taking into consideration the randomness in wind speed, the maximum power at the wind turbine is optimized. Then, the control strategy utilizes direct power control (DPC) due to its various advantages. The advantages of employing this control technique are manifold. Firstly, it eliminates the necessity for rotor current control loops. Secondly, it obviates the need for controllers such as PI controllers to manage torque and flux. Furthermore, it has yielded exceptional simulation results when implementing direct power control (DPC) within the MATLAB/Simulink environment, specifically in the context of a doubly fed induction generator (DFIG) wind power system.

This paper investigates the impedance modeling and stability analysis of doubly-fed induction generator (DFIG) system based on direct power control (DPC) strategy without phase-locked loop (PLL). In order to avoid the stability problem caused by the PLL, the DPC without PLL is established in the virtual dq reference frame. Based on the developed impedance model, the impedance differences between the DPC without PLL and conventional vector control is first revealed, and then the stability influence on DFIG system will be analyzed by using single input single output (SISO) impedance model, especially when DFIG is connected to the weak grid. Simulation results will be given to validate the correctness of the theoretical analysis.

This Paper Analysis the matrix rectifier topology and the current space vector modulation(SVM) algorithm of matrix rectifier under balanced three-phase input voltage condition, According to the imbalanced three-phase input voltage and voltage drop conditions will do a effort to the output DC voltage, adopted a feedback control strategy based on current space vector modulation(SVM) algorithm. Through testing the output voltage value and compare to the target voltage, and then using PI control to dynamically adjust the modulation factor to ensure that the average output voltage equal to the target value, while suppressing the ripple. A practical simulation model of matrix rectifier was built up with Matlab/Simulink and simulated under the condition of balanced three-phase input voltage, imbalanced three-phase input voltage and drop voltage conditions. The simulation results show the correctness and effectiveness of the control strategy.