Sebastian Stynski

Control of Three-Level PWM Converter Applied to Variable-Speed-Type Turbines

This paper proposes advanced control of a three-phase three-level neutral-point-clamped pulsewidth-modulated (PWM) converter connecting a permanent-magnet synchronous generator to a grid. The control scheme is mainly based on active and reactive power loops and contains the following additional blocks: virtual flux and filter-capacitor voltage estimators for sensorless operation, active damping (AD) of possible resonances in the LCL filter that connects the converter to the grid, and a PWM modulator with dc-link voltage balancing and minimization of switching losses. It is shown that the proposed control method exhibits several features such as sensorless operation, robust algorithm, minimization of switching losses, and simple tuning procedure of AD. The simulation and experimental results have proven an excellent performance and verified the validity of the proposed system.

Control of Variable-Speed Type Wind Turbines Using Direct Power Control Space Vector Modulated 3-Level PWM Converter

This paper presents implementation of system for variable-speed wind turbine based on permanent magnet synchronous generator (PMSG). System consists of six-pulse diode rectifier, dc/dc boost converter and 3-level neutral point clamped (npc) converter. Control scheme is mainly based on active and reactive power loops and contains following additional blocks: virtual flux and filter-capacitor voltage estimators for sensorless operation, active damping (AD) of possible resonances in LCL filter connecting converter to the grid, PWM modulator with DC link voltage balancing and minimization of switching losses. It is shown that the proposed control method exhibits several features as: sensorless operation, robust algorithm, minimization of switching losses as well as simple tuning procedure of AD. Simulation and experimental results have proven a good performance and verified the validity of the proposed system.

Novel Control of Three-Phase Active Front-End Converter With Compensation of Unknown Grid-Side Inductance

This paper proposes improvements to the control method based on the complete dynamical model published by Kömürcügil and Kükrer, which is very simple by operation in the stationary reference frame and lacks ac-line-current sensors. Nevertheless, the basic control method is very sensitive to variations of the line inductances, which provide difficulties in many industry applications. The modifications proposed in this paper overcome this disadvantage using a fuzzy logic controller to tune parameters and do more robust the basic control in view of line inductance parameters variations. Unfortunately, the new tuning method needs information about the reactive line current; therefore, ac-line-current reconstruction algorithm based on the dc-link current measurement has been included to keep the same number of sensors as the basic solution. Simulation and experimental results have proved the correct system operation at wide variations of the line inductance.

DSP/FPGA Control for Variable-Speed Wind Turbines

This paper proposes an advanced control of three-phase three-level neutral point clamped (3L-NPC) PWM converter connecting a parallel connected generators to a grid. Control scheme is mainly based on active and reactive power loops and contains following additional blocks: virtual flux and filter-capacitor voltage estimators for sensorless operation, active damping (AD) of possible resonances in LCL filter connecting converter to the grid, PWM modulator with DC link voltage balancing and minimization of switching losses. It is shown that the proposed control method exhibits several features as: sensorless operation, robust algorithm, minimization of switching losses as well as simple tuning procedure of AD. Simulation and experimental results have proven an excellent performance and verified the validity of the proposed system

Simulation of Single-Phase Cascade Multilevel PWM Converters

Paper presents simulation of novel single-phase cascade multilevel PWM converter topology. Solution is based on series connection of 5-level FLC modules, what gives possibility for flexible operation of converter at various high voltage and high power conditions. The new cascaded solution provide a high number of output levels and high modularity (Power Electronics Building Blocks-PEBB). Moreover paper describes hybrid modulation, which based on simultaneous square-wave operation of one converter with triangle carrier-based PWM modulation of another. It gives chance to use low frequency switching devices in one of the converters. Several simulation results are presented, which confirm the validity of the proposed approach and possibility to reach high quality output voltage.

Analysis of multilevel PWM converter based on FLC modules for an AC traction application

The paper presents simulation of multilevel PWM front-end converter based on 5-level flying capacitor (FLC) modules for an AC traction application. Two possibilities of parallel connected FLC modules with common and separated DC bus (where each module can provide different DC voltage level) have been analyzed in this paper. Several simulations are presented for both solutions, what confirm usefulness of the proposed approach for high power traction application.

Hardware methods for detecting global maximum power point in a PV power plant

Conventional maximum power point tracking (MPPT) algorithms are designed under assumption that all modules are uniformly insulated and therefore can be characterized by a single maximum power point (MPP). At increasing power level PV arrays become larger in area. Moreover, to achieve a reasonable voltage level modules are connected in series, creating strings. These two factors make any array susceptible for any mismatch in their current-voltage characteristics. Under partial shading condition (PSC), when PV modules receive different insulation, multiple maxima occur in power curve of the array. This leads to a tracking error of the MPP and results in significant decrease in efficiency of the system. This paper describes Global Maximum Power Point Searching (GMPPS) methods which are designed specifically for searching global MPP (GMPP). Three hardware methods, which are based on fast sweeping of the characteristics via additional circuitry are described and compared. Three-level boost (TLB) converter is utilized as a DC-DC converter performing GMPPS. Simulation results are provided with 15 kWp PV string model.

Advanced DSP Control of 3-Level DC/AC Converter for Variable-Speed PMSG

This paper proposes an advanced control of three-phase three-level neutral point clamped (3L-NPC) PWM converter connecting a permanent magnet synchronous generator (PMSG) to a grid. Control scheme is mainly based on active and reactive power loops and contains following additional blocks: virtual flux and filter-capacitor voltage estimators for sensorless operation, active damping (AD) of possible resonances in LCL filter connecting converter to the grid, PWM modulator with DC link voltage balancing and minimization of switching losses. It is shown that the proposed control method exhibits several features as: sensorless operation, robust algorithm, minimization of switching losses as well as simple tuning procedure of AD. Simulation and experimental results have proven a good performance and verified the validity of the proposed system.

Simple scanning methods for a Global-MPP determination in a PV string

Partial shading and/or mismatch of photovoltaic (PV) modules can cause multiple maxima to occur in their power-voltage curves which can mislead conventional Maximum Power Point Tracking (MPPT) algorithms. This relates both to residential installations and large-scale power plants and can result in significant drop in the overall energy yield. To overcome this problem, a new approach generally referred to as Global Maximum Power Point Searching (GMPPS) has emerged. GMPPS methods based on power-voltage curve scanning are able to obtain optimum operating point in a very short time, regardless of the irradiation profile. This paper presents two methods utilizing external circuitry in order to scan the power-voltage curve of the PV string and determine its maximum power. First method utilizes a MOSFET acting as variable resistive load, whereas the latter is based on forcing the PV current using an switched inductor. Simulation study followed by the experimental verification is presented for both methods.

Power management in four-leg converter interfacing RES with the grid

This paper presents operation of the four-leg three-level Flying Capacitor Converter (FCC) interfacing renewable energy source (RES) with the grid. Such converter with proposed control method enables work in association of electrical grid disturbances by switching all legs separately to stand-alone or grid connected mode of operation, what allows for energy transfer between them. Four-leg FCC with described control method may be treat as DC microgrid supplied from three independent AC sources and RES. Therefore, very popular in last few years, hierarchical control [1] can be adapted to make power management of such system. Paper describe proposed control method and hierarchical control for such solution. Experimental results are shown and discussed.