Synchronous Converter Research Articles

Прогноз выработки электроэнергии инвариантных ветроэнергетических установок методом нечеткой логики

The current state of development of autonomous electric power supply systems, including objects of gas transmission systems is considered. Use in the combined generating complexes of alternative sources of the electric power on the basis of wind power installations is proved. Are offered options of structures of power supply networks for pipeline service consumers with use of wind power installations. Are analyses energy-efficient invariant systems on the basis of the combined installations according to the scheme "the synchronous generator-the frequency converter". The predicted power generation volumes are received by power sources at stochastic character of a wind stream.

Inducverters: PLL-Less Converters With Auto-Synchronization and Emulated Inertia Capability

Inspired by induction machines working principles, this paper presents the idea of phase-locked-loop-less (PLL-less) operation of grid-connected voltage source converters (VSCs) under new concept of inducverter. The proposed controller eliminates the need for a dedicated synchronization process and the related PLL, and therefore it offers a simpler and more reliable control strategy compared to the conventional methods. In addition, it represents an improved performance, as it provides real and true auto-start and auto-synchronization with a grid without the need for grid voltage information. A current damping/synchronization unit enables grid auto-synchronization by using local current information and can track grid voltage frequency, angle, and amplitude variations while feeding constant amount of power, which is of high-interest in frequency varying grids and also in the case of grid voltage angle jump. Another advantage of the inducverter is that it introduces virtual inertia to the grid to regulate frequency, which enhances frequency dynamics of smart grids. Beside the current synchronization unit, the proposed strategy has a single-loop controller core with control over both power and current, which is implemented in a hybrid dq and abc frame using a virtual adaptive lead or lag impedance. The controller also offers stable and high-performance synchronization and operation under unbalanced and/or distorted grid conditions. The work beside synchronous current converters gives a bird’s eye view to research in the new area of PLL-less and virtual inertia-based operation of VSCs and fulfill a unified set of controllers for the smart grid integration. Simulation, hardware-in-loop, and experimental results are presented to validate effectiveness of the controller.

Multivariable Droop Control of Synchronous Current Converters in Weak Grids/Microgrids With Decoupled <italic>dq</italic>-Axes Currents

Weak grids/microgrids are gaining considerable attention due to the installation of renewable power generation resources in areas that are remote from load centers. This paper presents a multivariable-droop synchronous current converter control strategy for current management of weak grid/microgrid applications, and offers a systematic and straight-forward design approach using the loop shaping technique. The controller integrates current regulation, management, and limitation that are applicable to weak grids and microgrids (MGs). The multivariable synchronous current converter enables superior decoupling of ${d}$ - and ${q}$ -axis currents in weak grids and/or resistive grids where these control variables are highly coupled due to converter operation at large load-angles. Therefore, stable connection of weak (high impedance) resistive MGs to utility grids is feasible. The multivariable droop concept also realizes real power sharing by simultaneous drooping of both frequency and voltage amplitude, which enhances load sharing accuracy in resistive and/or weak grids. Similar to its predecessor, synchronous converters, the controller can eliminate phase-locked loop (PLL) and provides a unified controller, PLL, and load manager in one simple control methodology. This can facilitate grid auto-synchronization, which can improve the stability of voltage source converters in weak grid applications. Also, the controller can participate in the power system frequency, and voltage regulation and control. To evaluate the performance of the controller, several simulations are conducted under various typical scenarios and conditions.

A Novel Research of ZVZCS Synchronous Rectification Converter Based on Phase-shifted Full-bridge Control

A Novel Research of ZVZCS Synchronous Rectification Converter Based on Phase-shifted Full-bridge Control

On-chip integrated power management MPPT controller utilizing cell-level architecture for PV solar system

An on chip integrated power management circuit with maximum power point tracking (PM-MPPT) control is proposed in this paper in order to achieve high efficiency Photovoltaic (PV) system. The proposed PM-MMPT circuit mitigates partial shading issues which exist in PV systems by utilizing cell-level distributed MPPT architecture, where each cell has its own MPPT circuit, in order for each cell to produce its own maximum power without affecting other cells or being affected by other cells. The proposed PM-MPPT circuit consists of two different parts. The first part is a high-efficiency synchronous power converter stage. The second part is an analog ripple correlation control (RCC) MPPT control circuit which provides faster and efficient MPP tracking, has less circuit complexity and low power consumption. HSPICE simulation model of the proposed PM-MPPT circuit is developed with a solar cell that has 0.5V open circuit voltage and 6A short circuit current. Simulation results show that the proposed PM-MPPT circuit rapidly tracks the MPP with a tracking efficiency larger than 99% over a wide range of irradiation levels and 92% system power conversion efficiency at a 2W power level. The detailed analog design of the power stage and the RCC MPPT circuits are presented and discussed in the paper based on 0.35μm CMOS technology. In addition, the PM-MMPT IC layout is presented and discussed. To validate the proposed technique and design, a comparison between the results of the proposed circuit and other reported techniques from the literature is provided. It is shown that the proposed circuit and system are able to operate with the lowest input voltage and the highest output power compared with other reported techniques. Moreover, the proposed design has the smallest size under 2W power level.

A bidirectional DC/DC converter charge/discharge controller for solar energy illumination system integrating synchronous rectification SEPIC converter and active clamp flyback converter

SummaryThis paper presents a novel bidirectional DC‐to‐DC converter charge/discharge controller for solar energy illumination system. The bidirectional converter architecture integrates the synchronous rectification Single Ended Primary Inductor Converter (SEPIC) converter and an active clamp flyback converter. In addition to fully use the properties of the shared components and compensate for the shortcomings of conventional two‐stage illumination systems, the proposed system has the advantages of soft‐switching, simple structure, and high efficiency. During daytime, a SEPIC converter with synchronous rectification function was used to charge the lead acid battery through three‐stage charging and maximum power point tracking. At night, the battery discharges, driving and dimming high‐brightness LEDs using the active clamp flyback converter. Finally, a solar energy illumination system with both a 160 W charge/discharge controller and an 80 W LED driver was implemented to verify the feasibility and practicality of the proposed system. Copyright © 2015 John Wiley & Sons, Ltd.

Maximum Power Point Tracking Converter Based on the Open-Circuit Voltage Method for Thermoelectric Generators

Thermoelectric generators (TEGs) convert heat energy into electricity in a quantity dependent on the temperature difference across them and the electrical load applied. It is critical to track the optimum electrical operating point through the use of power electronic converters controlled by a maximum power point tracking (MPPT) algorithm. The MPPT method based on the open-circuit voltage is arguably the most suitable for the linear electrical characteristic of TEGs. This paper presents an innovative way to perform the open-circuit voltage measure during the pseudonormal operation of the interfacing power electronic converter. The proposed MPPT technique is supported by theoretical analysis and used to control a synchronous Buck-Boost converter. The prototype MPPT converter is controlled by an inexpensive microcontroller, and a lead-acid battery is used to accumulate the harvested energy. Experimental results using commercial TEG devices prove that the converter accurately tracks the maximum power point during thermal transients. Precise measurements in the steady state show that the converter finds the maximum power point with a tracking efficiency of 99.85%.

Dynamics of supercapacitor bank with uncontrolled active balancer for engine starting

In this paper, analytical investigation of an actively balanced open-loop operated supercapacitor bank is presented. Supercapacitor unit is utilized for 28V auxiliary power unit diesel engine starting, allowing relieving the battery from multiple starting stresses. Dynamical equations of the system based on a synchronous bidirectional buck-boost converter are developed by splitting the solution into zero-input and zero-state responses. It is revealed that the system, which is typically nonlinear because of buck-boost converter presence, becomes linear when operated in open loop. Moreover, natural balancing is achieved when the converter is operated with 50% duty cycle. It is shown that balancing time is independent on initial conditions while system damping strongly depends on parasitic resistances especially in practical case of large capacitors and small inductance. Inductor current peak value and balancing time are obtained analytically and validated by simulations. It is revealed that while natural balancing is always achieved, excessive currents may arise when the initial voltage misbalance is significant. In addition, it is shown that one-switching-cycle averaged model is in close agreement with detailed switched model. The presented findings are fully supported by extended simulations.

New Family of Microgrid Control and Management Strategies in Smart Distribution Grids—Analysis, Comparison and Testing

This paper presents a new family of universal control and management strategies for microgrids in smart distribution grids. The paper also provides a general and computationally-efficient framework for modeling and analysis of power management strategies in a microgrid with multiple-distributed generation (DG) units which eases microgrid dynamic studies and controller parameters selection in large microgrids with multiple DG units. Three different approaches for real and reactive power management are proposed. The controllers offer the following advantages: 1) the proposed topologies can be applied to both voltage-controlled (VC) and current controlled (CC) voltage source converters (VSCs). 2) The controllers are universal and realize requirements of both grid-connected and islanded modes, i.e., they share real and reactive power during islanding with constant frequency operation and act as grid supporting VSCs in the grid connected mode. 3) The drooping variables can be either power or current, thus VC-power drooping, VC-current drooping and CC-power drooping are different available variants. 4) The concept of hybrid polar-vector control is developed in this paper. Thus, it can combine the benefits of both types of controllers in one augmented strategy. 5) The controller emulates the behavior of conventional synchronous generators (SGs) which in turn results in better integration of electronically-interfaced DG units into the power system and prevents instabilities due to interaction of fast response DGs and SGs. 6) The controllers realize seamless and robust transition to the islanding mode. The controllers are developed under new concept of synchronous converters. A theoretical analysis and simulation results show that the proposed controllers yield the aforementioned requirements in one compact structure.

Investigation of Modified Generalized Interline Power Flow Controller (GIPFC) and Performance Analysis

Nowadays in the restructured scenario, the main challenging objective of the modern power system is to avoid blackouts and provide uninterrupted quality power supply with dynamic response during emergency to improve power system security and stability. In this sense the convertible static compensator (CSC) that is the Generalized Inter line power flow controller (GIPFC), can control and optimize power flow in multi-line transmission system instead of controlling single line like its forerunner FACTS (Flexible AC Transmission System) controller. By adding a STATCOM (Static synchronous Shunt Converter) at the front end of the test power system and connecting to the common DC link of the IPFC, it is possible to bring the power factor to higher level and harmonics to the lower level and this arrangement is popularly known as Generalized Inter line power flow controller (GIPFC). In this paper a new concept of GIPFC based on incorporating a voltage source converter with zero sequence injection SPWM technique is presented for reinforcement of system stability margin. A detailed circuit model of modified GIPFC is developed and its performance is validated for a standard test system. Simulation is done using MATLAB Simulink.Index Terms—Convertible static controller, Flexible AC Transmission System (FACTS), Generalized Interline Power Flow Controller (GIPFC),STATCOM, SSSC, Reactive power compensation.

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Mode-Selectable High-Efficiency Low-Quiescent-Current Synchronous Buck DC–DC Converter

In this paper, a mode-selectable synchronous buck DC-DC converter with high efficiency and low quiescent current is proposed, which is suitable particularly for use as an Li-ion battery charger. The high efficiency is obtained by applying dynamic power management technology under light load, which makes some modules of the chip enter into sleep state and the quiescent current of the whole chip down to 45 μA. At the same time, power metal-oxide semiconductor (MOS) devices are also shut down to decrease the dissipation of the system. A simple loop compensation method is also proposed, which can eliminate the influence brought by the high equivalent resistance of the output's capacitor on the stability of the system loop. The converter has been made with a 0.5- μm complementary MOS process. Experimental results show that the peak efficiency is 94% at an output current of 100 mA when the supply voltage is 2.7 V. Moreover, the output voltage can recover within 14 μs at 400-mA load step.

Limiting Integral Loop Digital Control for DC–DC Converters Subject to Changes in Load Current and Source Voltage

A new digital control technique is proposed to improve the speed of both load current and source voltage transient responses for dc-dc converters operating in continuous conduction mode (CCM). The key structure of the proposed control technique is a combination of a limiting integral loop and related arithmetic operations to produce the desired switching sequence during transient condition. The limiting integral loop is built as a novel structure for capacitor charge balance operation. In contrast to previous approaches, the proposed control technique is valid for three basic converters: 1) buck; 2) boost; and 3) buck-boost. Moreover, since the transient period is forced to be an integer multiple of the switching cycle, the advantage of fixed switching frequency is inherently provided. Simulation and experimental results from a noninverting synchronous buck-boost converter prototype are given to validate the effectiveness of the proposed solution.

SYNCHRONOUS FLYBACK CONVERTER WITH SYNCHRONOUS BUCK POST REGULATOR

In general, conventional converter is used for converting the power level from one stage to another. But conventional type of converter has slightly more power losses & voltage drop, so efficiency is very sensitive for the low voltage specification and also cooling of dissipative elements floating at higher voltages is a difficult task. So high efficient scheme of synchronous flyback converter with synchronous buck post regulator was approached and low voltage drop, less power losses & very high efficiency was achieved. Where the secondary side of flyback converter including Synchronous buck post regulator floats on the very high voltage line (i.e. 10kV) for the Filament power supply heats the cathode to required temperature to emit electrons in TWT. Filament Power supply based on the Fly back Converter topology which is operated at 100 KHz in CCM mode The Pulse width modulation technique is used to maintain the voltage at desired value using IC. The Post regulator using Synchronous buck topology is implemented for regulating the output voltage of synchronous flyback converter (9.5V DC) to Regulated 6.3V @ 3.3A DC.

Active and reactive power regulation in grid connected wind energy systems with permanent magnet synchronous generator and matrix converter

This study presents a simple voltage oriented vector control scheme to regulate active and reactive power in a grid connected variable speed wind electrical system that consists of permanent magnet synchronous generator and matrix converter, which enables the maximum power tracking in wind electrical systems. The maximum extractable power from wind is derived from power curves and set as reference active power. Reactive power reference is chosen as zero. The deviations in powers are processed by proportional and integral (PI) controllers which vary the voltage gain of MC through which the desired regulation of powers is carried out. Since the relationship between wind speed and reference active power is nonlinear, single PI controller is insufficient, hence gain scheduling is required to adjust the controller parameters in response to changes in wind speeds. The controller parameter change is abrupt in conventional gain scheduling which leads to unstable performance. To avoid this, neural network-based PI (NN-PI) is designed which is more robust. In the presented work, both conventional gain scheduled PI and NN-PI are applied to validate the suggested voltage oriented control for power regulation. Simulation and experimental studies are presented to confirm the effective functionality of the system.

Determination of Synchronous Reactive Frequency Doublers EMFs Using Magnetic Field's Mathematical Simulation

In many spheres of human activities devices that work on increased frequency current are widely applied. 50 Hz current can be converted into increased frequency (100-400 Hz) current using synchronous reactive converters, which are based on exude and usage of higher harmonics.

Detailed Study of Closed Stator Slots for a Direct-Driven Synchronous Permanent Magnet Linear Wave Energy Converter

The aim of this paper is to analyze how a permanent magnet linear generator for wave power behaves when the stator slots are closed. The usual design of stator geometry is to use open slots to maintain a low magnetic leakage flux between the stator teeth. By doing this, harmonics are induced in the magnetic flux density in the air-gap due to slotting. The closed slots are designed to cause saturation, to keep the permeability low. This reduces the slot harmonics in the magnetic flux density, but will also increase the flux leakage between the stator teeth. An analytical model has been created to study the flux through the closed slots and the result compared with finite element simulations. The outcome shows a reduction of the cogging force and a reduction of the harmonics of the magnetic flux density in the air-gap. It also shows a small increase of the total magnetic flux entering the stator and an increased magnetic flux leakage through the closed slots.

Dynamical study of peak-current-mode controlled synchronous switching Z-source converter

Z-source converter can have a high voltage transmission ratio, reduce the losses of switching devices, and improve the efficiency of the system, etc., because of embedding the Z-source network into the system, which makes it find wide applications in DC conversion, inverters, etc. Nonlinear dynamics of the peak-current-mode controlled synchronous switching Z-source converter is studied for the first time so far as we know. The discrete iterated mapping model under continuous current mode is established, while the effects of the reference current on the stability of the system are analyzed by using the trajectories of eigenvalues, and the steady state operation parameter domain is schemed. Period-doubling bifurcation, border-collision bifurcation, tangent bifurcation and intermittent chaos are found in this converter based on the bifurcation diagram and the Lyapunov exponent diagram, and the evolvement and mechanism of the border-collision bifurcation and chaos are analyzed. Finally, the circuit simulation and the experimental results show that the theoretical analysis is correct. Results obtained indicate that with the increase of the reference current, the peak-current-mode controlled synchronous switching Z-source converter goes from period 1 into period 2 and period 4 through the period-doubling bifurcation, and moves into the intermittent chaos due to the border-collision bifurcation. Then the system exhibits a period-3 behaviour because of the tangent bifurcation. Finally, the converter moves into chaos due to the border-collision bifurcation again.

A Consideration on the Characteristics of Output, Loss, and Capacity Factor of Offshore Wind Farm

A number of offshore wind farms are being in operation in the world. It is important to evaluate the characteristics of losses and output power of a large scale wind generation system like an offshore wind farm. This technical note presents analyses about the output power and loss characteristics of an offshore wind farm composed of permanent magnet synchronous generators (PMSG), power converters, and high voltage transmission cables connected to the onshore grid, in which two types of transmission systems, that is, HVAC and HVDC systems, are considered. Comparative analysis between the wind farms with two transmission systems is performed about annual output energy, system losses, and capacity factor for some typical regions whose wind speed data are expressed by the probability density distribution function obtained from Local Area Wind Energy Prediction System (LAWEPS) in NEDO homepage in Japan.

Математическая модель активного выпрямителя в несимметричных режимах работы

Asymmetric voltage dips lead to disconnection of the main drives (MD) mills and as a consequence to operational delays. Modern MD is often performed on the basis of synchronous motors and frequency converters, consisting of active rectifier (AR) and voltage source inverter. Control systems of active rectifier usually not adapted to asymmetry of voltage or when the asymmetry AB passes the diode mode. Analysis of work MD 2000 cold rolling mill showed that when voltage asymmetry AR enters to the diode mode. However, this method is not very effective because often occur disconnection MD and equipment downtime. Since the known mathematical models of the AR does not allow to study the operation of AR in the diode mode, a mathematical model that allows it to do. Using the resultant model analyzes work MD mill 2000 at a voltage asymmetry in the absence of AR adaptation to unbalance in the case of switching the diode AR mode as well as in the case of feedforward control of negative sequence of current. The results show that AR with feedforward control current negative sequence most stable operating in asymmetrical modes.