Output Voltage Of Converter Research Articles

Robust sliding mode controller for buck DC converter in off-grid applications

This paper presents a robust sliding mode controller of DC-DC buck converter for renewable energy applications, such as photovoltaic systems in off-grid configurations. Photovoltaic systems in off-grid configuration are exposed to significant variations in input voltage and power loads. The proposed sliding mode controller presents a simple and efficient method of continuously updating the duty cycle of a pulse width modulation unit (PWM) of a buck converter. The PWM unit is operated at constant switching frequency of 10 kHz carrier signal and varying duty cycle. The differences in input voltage and power load are treated as two bounded uncertainties, thus eliminating the need for input voltage sensor and output current sensors leaving the system with a single sensor required to measure the converter output voltage. That is, measured output voltage is compared with the reference voltage to continuously update the average duty cycle value of PWM unit. Adjustment of PWM duty cycle is performed while maintaining the sliding condition always fulfilled. The simulation results of the proposed controller showed robustness and accuracy against power load fluctuation, changes in desired output voltage, and variations in the input supply voltage that may result from the varying level of irradiance and temperature.

Linear Active Disturbance Rejection Control of New Double Full-Bridge ZVZCS Converter for Beam Supply

In view of the unstable output voltage of the new double full bridge ZVZCS converter of beam power supply when it is disturbed by external disturbance or internal parameter change in practical application, combined with the characteristics of the beam power supply system model, this paper proposes a beam power supply control strategy based on linear active disturbance rejection control (LADRC). Firstly, the working principle of the new double full bridge ZVZCS converter of beam power supply is analyzed, and considering the parasitic parameters and effective duty cycle of circuit components, the small signal equivalent model under two working modes is established. Secondly, combined with the system model and linear active disturbance rejection control theory, a double closed-loop controller is designed, which takes the second-order LADRC as the outer voltage loop and PI control as the inner current loop. Finally, the simulation and experimental results show that the designed controller has stronger robustness, anti-interference and better dynamic response speed than the traditional double closed-loop PI controller in load switching and dual-mode switching, and has a good development prospect.

ZETA Converter as a Voltage Stabilizer with Fuzzy Logic Controller Method in The Pico Hydro Power Plant

The development of the use of renewable energy that is environmentally friendly has been widely carried out, one of which is the use of energy as a turbine drive in the Pico Hydro Power Plant. The main problem in using energy, especially water energy, is the flow of water which can affect the flow of water used to rotate the turbine, so that the voltage on the DC link cannot be kept constant. Therefore, in this paper, we will design and simulate the charging process for a lead acid battery with a DC-DC converter and a Pico Hydro Power Plant as the main source. The type of generator used in the Pico Hydro Power Plant is a DC generator. The output voltage of the DC generator is still fluctuating, so to keep the output voltage constant, a DC-DC converter is needed, namely the ZETA Converter, so that its efficiency will be better when compared to using other types of converters. The ZETA converter with a DC generator as a source will be used for the battery charging process using the Fuzzy Logic Controller so that the output voltage of the ZETA converter can be kept stable or constant. The results obtained in the close loop simulation test are that the output voltage is constant at 14.4 V and the output current is 6.64 A so that it can be used for the battery charging process that will be used for household lighting.

КОМБІНОВАНА ТРАНСФОРМАТОРНО-КЛЮЧОВА ВИКОНАВЧА СТРУКТУРА ДВОФУНКЦІЙНОГО ПЕРЕТВОРЮВАЧА З ДИСКРЕТНО-РАЗОВИМ КЕРУВАННЯМ

Power supply systems with transformer-and-switches executive structures have a prominent place in the power supply systems of electrical and electro technological equipment. Voltage converters based on them with discrete-time control of semiconductor switches are characterized by high energy performance and the absence of distortions in the operating states of the output voltage and input current. The constant increase in the range and number of electricity consumers that require the use of such converters for their standardized operation, encourages their appropriate improvement, in particular to expand functionality. The peculiarities of forming a combined transformer- and-switches executive structure of a two-function converter for a rectified current power supply system, which is characterized by increased efficiency of semiconductor devices and lower losses in them, are investigated. Possible and expedient ranges of regulation of output voltage of such converters are defined. References 12, tables 2, figures 4.

DC-DC High-Step-Up Quasi-Resonant Converter to Drive Acoustic Transmitters

This paper proposes a quasi-resonant step-up DC-DC converter to provide the DC-link voltage for piezoelectric transmitters (PZETs). The resonance not only provides a soft-switching condition for the converter switches, but also helps to decrease the converter element sizes for marine applications. Operation modes of the proposed converter are discussed. The current and voltage of the converter components are derived analytically, and hence the converter gain is obtained. The performance of the proposed high-step-up, high-power density converter is examined through a comprehensive simulation study. The simulation results demonstrate the soft-switching operation and short transient time required for the converter to reach the reference output voltage. The converter output voltage remains unchanged when an inverter with a passive filter is placed at its output while supplying the PZET. The proposed DC-DC converter is prototyped to validate the converter gain and soft-switching operation experimentally. The converter gain and soft-switching results in simulation are well matched with those of the experimental tests. The converter efficiency in three different switching frequencies is obtained experimentally. The power density of the proposed topology is determined via the designing of a printed circuit board. The experimental results demonstrate the appropriate gain and efficiency of the converter in the tested power range.

Performance Assessment of Eight-Switch 11-Level Packed U Cell Converter Under Dynamic Solar Photovoltaic Environment

This article presents a new 11-level packed U cell (PUC) converter with less active switches for solar photovoltaic (PV) applications. This PUC converter comprises eight active switches with two capacitors and a PV array. Compared to the existing topology, the proposed topology has the ability to attain 11 levels in converter output voltage, with fewer active switches. The operating modes of the 11-level PUC converter are discussed. A single-phase active and reactive power (PQ) control with the capacitor voltage balancing is incorporated for grid-tied configuration. The maximum power point tracking (MPPT) using perturb and observe is used from the PV array. The balancing of floating capacitors is achieved by proportional–integral (PI) controllers. This helps in achieving desired converter voltage levels. Conduction and switching losses are calculated for the efficiency of the system. Eleven-level PUC converter performance is analyzed in steady-state and dynamic conditions using the OPAL-RT test bench.

An Efficient High-Frequency Discrete Controller for Solar Powered Boost Converter

In this paper, Delta operator based Discrete Sliding Mode Fuzzy Control (Delta-DSMFC) strategy is introduced for solar powered boost converter so that the output tracks the reference even at high-frequency. Furthermost methods realized to find MPPT have some disadvantage like the fluctuation around the operating point. Therefore, there is a requirement to obtain maximum solar energy by tracking the maximum power point robustly. This paper proposes a discrete control technique that is implemented to boost converter in order to overcome this problem. It is well established that the Discrete Sliding Mode Controller could be successfully used to control output voltage of the DC-DC converters where the system response is slow and introduces chattering problem. However, there may be a possibility of loss of information during fast sampling. In order to address the performance issue and avoid the loss of information when operating under high frequency, delta operator has been introduced. With the use of this operator, which has distinct mathematical property, the response of the converter is improved even at faster sampling rate. One more advantage of using delta operator is that it can convert analog signal to digital and vice-versa at high efficiency. The chattering problem is overcome by the introduction of fuzzy controller to tune the gain. Overall benefit of using this control technique is that it improves the overall efficiency by reducing the ripple current and improving rise time of the system. With the usage of renewable resource, the system is economical.

An Output Feedback Discrete-Time Controller for the DC-DC Buck Converter

This paper presents a discrete-time output feedback controller to regulate the output voltage of a DC-DC buck converter. The proposal’s main feature is the application of a discrete-time equivalent of the robust exact filtering differentiator. First, the document exposes a theoretical analysis of the closed-loop system, where it is considered the problem of implementing a real-time differentiator with a good relationship between exactness and noise filtration performance. Hence, secondly, the controller in a laboratory setup is presented. The first experimental results suggest that the proposed controller exhibits good robustness against noise and maintains the asymptotic accuracy, even with saturated control inputs, as in the case of the DC-DC buck converter. Consequently, aiming to verify the features of the proposed method, the controller is validated through multiple experiments, showing satisfactory voltage tracking accuracy, good suppression of instantaneous load and supply voltage disturbances, and robustness against bounded measurement noise.

Scott-Tied Magnetically Linked Solar Multilevel Converter in Varying Environmental Conditions

Recently, multilevel converters (MLCs) have given promising solutions for medium-power and high-power renewable energy systems. However, voltage level enhancement leads to a higher device count, especially for three-phase configurations. A megawatt-scale three-phase 27-level converter with a Scott-connected arrangement is used for medium-voltage applications to address such issues. The Scott transformer uses 1:3:9 turn ratios between the windings to have 27-level output converter voltage with the advantage of two-phase to three-phase conversion. Moreover, the transformers enable the converter output voltage to medium-voltage levels (typically 11 to 33 kV). Traditional three-phase systems have cascaded power converter modules in each phase. However, this system provides an alternative solution for solar power injection into the grid with minimum cascaded voltage source converters forming a two-phase network. The quadrature displaced nearest level modulation strategy fundamentally switches phase A and B legs. Moreover, the solar photovoltaic (SPV) system is modeled at a megawatt-scale and tested in various environmental conditions. Thermal, cost, and leakage-inductance models are presented for the Scott-tied solar MLC. Obtained results demonstrate the satisfactory observation and control of the SPV system for renewable energy applications.

Бесступенчатое управление индексом модуляции трехфазного преобразователя электропривода в режиме «flat-top»

The article discusses one of the ways of stepless overmodulation in a semiconductor three-phase voltage inverter implemented according to the B6 scheme. In the review part of the article, the features of the PWM and overmodulation (“flat-top”) modes are briefly considered. The formation of the maximum possible values of the output voltage of the converter is possible due to the maximum values of the modulation index and the voltage inverter coefficient. It is shown that a variable-modulation index in the "flat-top" mode has a number of significant advantages over a fixed one, formed, for example, by "mixing" the PWM reference signal with additional harmonic signals. The geometric interpretation of the positions of the inverter output voltage vectors on the plane and their connection with the PWM reference signal made it possible to synthesize a high-precision (basic) non-linear characteristic in the inverter reference voltage path and to form a linear stepless control law for the inverter output voltage when the “flat-top” of the specified voltage coefficient is activated. The results of comparison of the basic variant of converter output voltage control with a simpler one obtained by approximating the basic equations using numerical methods of mathematics and computer simulation are presented. The absolute error of the modulation index in the case of approximation is no more than one percent in the entire "flat-top" range. The hodographs of the output voltage of the inverter in the X-Y axes are given for three different coefficients of the converter during the transition from PWM to "flat-top". The advantages of the method include the simplicity of its implementation in a new or existing space-vector PWM, the implementation of which is carried out exclusively by a software product. This aspect makes this method particularly attractive in low budget drives.

Implementation of a Programmable Electronic Load for Equipment Testing

This paper presents the implementation of an AC three-phase programmable electronic load (PEL) that emulates load profiles and can be used for testing equipment in microgrids (MGs). The implemented PEL topology is built with a voltage source inverter (VSI) which works as a current controlled source and a Buck converter which permits the dissipation of active power excess. The PEL operation modes according to the interchange of active and reactive power and its operation in four quadrants were determined. The power and current limits which establish the control limitations were also obtained. Three control loops were implemented to independently regulate active and reactive power and ensure energy balance in the system. The main contribution of this paper is the presentation a detailed analysis regarding hardware limitations and the operation of the VSI and Buck converter working together. The PEL was implemented for a power of 1.8 kVA. Several experimental results were carried out with inductive, capacitive, and resistive scenarios to validate the proper operation of the PEL. Experimental tests showed the correct behavior of the AC three-phase currents, VSI input voltage, and Buck converter output voltage of the PEL for profile changes, including transient response.

Partial Discharge Inception Characteristics of Twisted Pairs Under Single Voltage Pulses Generated by Silicon-Carbide Devices

Partial discharge (PD) is a major cause of degradation of motor winding insulation. It is a challenge to the successful electrification of all types of ground, sea, and aerial vehicles. However, the mechanism of PD under pulsewidth modulated voltages is not fully understood. This article studies PD inception characteristics in twisted pairs under single voltage pulses with reduced voltage overshoot, aiming to study the PD inception characteristics and mechanism without the influences of memory effects and voltage overshoot. The tests are conducted with a lab-designed 10-kV silicon carbide (SiC) device-based voltage pulse generator. The generator can produce voltage pulses with variable rise/fall times and pulse widths to emulate the output voltages of both silicon (Si) and SiC device-based power electronics converters. The voltage overshoot in this study has been limited to less than 5%. In addition, single voltage pulses are utilized as the excitation to remove charge memory effects. PD inception voltages, PD current magnitudes, and PD time delays of twisted pair samples are measured under various test conditions. It is found that the partial discharge inception voltage (PDIV) of the test sample decreases with reduced voltage rise time and increased voltage pulsewidth. Based on the test results, the impacts of voltage rise/fall times and pulse widths on PD behavior are explained using the extended volume-time theory. The relationships between PDIV, voltage rise/fall time, and pulsewidth are presented through empirical equations. Test results and analysis provide insights on the impacts of emerging wide bandgap devices in applications on motor winding insulations.

Fuzzy based MPPT Control System in Grid Connected Solar Plant

The increase in demand for the electricity system is increasing. Thus, enviromentally friendly technologies such as new and renewable energy are needed, one of which is a power plant with Photovoltaic as the main component. Solar power plant has enviromentally friendly properties. The design of this solar power plant uses Fuzzy Logic Controller and PI Controller methods, where both methods are used to find the maximum power peak point used for fast charges and MPPT, which is simulted using MATLAB/Simulink. The things presented in developing the generating system using these two methods are solar radiation intensity, temperature and Photovoltaic module. The model developed will make it possible to examine the characteristics of solar power plant and predict the amount of energy generated by solar panels in a particular location and compare the effectiveness of Fuzzy Logic and PI methods. The results shows that Fuzzy method produces a boost converter output voltage in the range of 600 V with result that are still not good and less stable, but the irradiation of 100 W/m2 voltage is stable, while the boost converter output voltage controller by the PI method is very good and stable in all conditions. Radiation and voltage are also in the range of 600 V.

SIMULATION OF CLOSED LOOP VOLTAGE CONTROL OF SEPIC CONVERTER

In this study, a robust output SEPIC DC-DC converter is designed and simulated. The studied single ended primary inductor converter (SEPIC) output voltage is regulated to a constant value regardless of its input. A double loop PI controller is designed and tuned for the voltage and current control which yields a control technique that results in simple implementation by reducing complexity. The multiloop control technique is used to improve converter behavior in case of wide system parameter variations. The controller parameters and design procedure are provided for the SEPIC converter for non zero current operation mode. The proposed implementation of the controlled SEPIC converter has been simulated in Matlab/Simulink environment. The simulations have been done with various operating conditions. Results show that the PI-controlled SEPIC rejects the disturbances and provides good tracking performance

Fuzzy-PI Control for Buck Converter Output Voltage Stabilizer

This paper presents a hybrid control between Fuzzy and PI to solve the problem of stability of the output voltage on the Buck Converter, especially in small power applications. This paper makes two main contributions. The first is the design of a simple Fuzzy-PI output voltage control design of a buck converter in Matlab. The second is the result of comparing the response of the traditional PI control system with the designed Fuzzy-PI hybrid control. The method used is a simulation with 3 stages. This process starts from the design of the Fuzzy-PI controller, simulation test with 3 scenarios, and verification with a comparison, namely the PI controller. The purpose of the simulation is to see the response of the system to changes in input voltage, reference voltage, and load resistance. Based on the test results, it is known that the Fuzzy-PI control is better than the PI control in maintaining the stability of the buck converter output voltage at every parameter change.

An efficient online energy distribution management system based on predictive control

An efficient online energy-distribution management system (EMS) that ensures cells operate under optimized conditions, is critical for the high performance and long-term service of large energy storage or generation systems. In this work, a novel two-level structure EMS based on model predictive control (MPC) is proposed to achieve fast energy balance with high-efficiency. The topology of the EMS is that cells are divided into several modules and each module connected in parallel with a bi-directional DC-DC converter, where the outputs of DC-DC converters are serially connected to obtain a higher DC bus voltage. Then the issues of energy deviations among cells are resolved by a two-level structure EMS which consists of an energy-distributing intra-group balance layer and a cell package current-distributing inter-group balance layer. Based on the EMS topology, an MPC is employed in each module to improve the balance speed while maintaining the stability of the DC-DC converter output voltage. Moreover, the parameters of the controller are optimized via simulation study. Finally, the EMS performance is validated by a hardware-in-loop platform and compared with existing EMS. The experimental results show that the proposed EMS can realize quick and accurate energy balance with low energy loss.

Online Efficiency Optimization of a Closed-Loop Controlled SiC-Based Bidirectional Boost Converter

This article presents an online efficiency optimization strategy for a digitally controlled, wide operating range silicon carbide based boost converter with bidirectional power flow. The proposed strategy minimizes switching losses at any given operating point by adjusting the converter switching frequency and dead times to optimally set the peak synchronous rectifier turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> current. This results in the converter achieving zero-voltage switching quasi-square wave (ZVS-QSW) operation with minimum inductor current ripple. The optimal timing parameters are determined online by fit functions based on sensed input/output voltages and inductor current, and applied to the converter in a low-bandwidth feed-forward loop operating in conjunction with closed-loop regulation of the converter output voltage. The fit functions are developed from multivariate curve fitting of the analytical solutions of the minimum-conduction ZVS-QSW state plane over the complete range of operation. The proposed approach enables bidirectional operation with efficiencies greater than 97.5% for input voltages ranging from 200 to 400 V, step-up conversion ratios up to 2.5, and power levels between 2 and 8 kW. The converter also achieves efficiencies greater than 99% over wide power levels at boost conversion ratios lower than 2.

SPACE VECTOR PWM IN A MULTILEVEL VOLTAGE CONVERTER

The present article considers the voltage forming by multilevel converters. Multilevel converters are widely used in industry applications with medium voltages up to 20 kV. An example is the oil industry, where multilevel converters are installed in electric drives of pumping units on pipeline systems. The location of the pipelines in isolated areas implies weak net connections for power system and expects increased requirements for the efficiency of the use of electricity. In this regard, for a multilevel voltage converter, an energy-efficient vector method of pulse-width modulation is proposed. With vector pulse-width modulation, the optimal number of voltage level switching occurs in the phases of the converter, which leads to the lowest harmonic distortion of the voltage, compared with other modulation methods. The features of vector pulse-width modulation in multilevel voltage converters caused by the increased number of basic voltage vectors of a static multilevel converter are analyzed. A step-by-step method of vector pulse-width modulation in a multilevel converter is proposed, including determining the base vectors of the converter closest to a reference voltage vector, calculating the time for each of the base vectors, maintaining the switching order between the base vectors. The method is considered in detail for a multilevel converter with five voltage levels in a phase. In conclusion, the results of modeling control system of this converter with the proposed method of vector pulse-width modulation are presented. According to the obtained time diagrams of voltage formation, a hodograph of the resulting vector of the output voltage of a multilevel static converter was constructed.

Fuzzy gain Scheduled PID Controller for Power Quality Enhancement in Grid Connected Hybrid Solar PV-PEMFC Energy System

Power quality improvement is inevitable due to the presence of power converters and non-linear loads in grid connected renewable based hybrid energy system (HES). The harmonics introduced by the distributed energy systems may lead to output voltage distortion andequipment failure which may lead to system losses. It may also cause for direct and indirecteconomic impacts. Development of active filter, passive filter and hybrid filter for harmonics mitigation would be an expensive solutions. Therefore, various DC/AC converter switchingschemes are proposed for power quality improvements in grid connected Solar Photovoltaic(PV) and fuel cell based HES. Initially, Solar PV and Proton Exchange Membrane Fuel cell (PEMFC) are modeled using MATLAB/Simulink. Further the harmonic behavior withProportional plus Integral (PI), Proportional plus Integral plus Derivative (PID) and Fuzzygain scheduled PID controllers are demonstrated using Pulse Width Modulator (PWM).Converter output voltage waveform, frequency spectrum and total harmonics distortion (THD) values at the Point of Common Coupling (PCC) have witnessed that the fuzzy gain scheduled PID controller suppresses the voltage distortions completely. It also yields 4 percentage THD value which satisfies the harmonic level recommended by IEEE 519 standard. Comparative analysis shows that the fuzzy gain scheduled PID control scheme exhibits superior performance than the traditional PI and PID controllers. Therefore, it is identified as an effective control scheme for power quality improvement in hybrid renewable energy system.

Research on Cascaded Single Phase PFC Based on Predictive PI Control

In order to improve the charging speed and reduce the occupied volume of an electric vehicle charger, a single-phase boost power factor corrector (PFC) system with cascade CHB (cascaded H-bridge) topology was adopted. Due to the periodic fluctuation of single-phase AC input, there is a large double power frequency ripple component in the output voltage of an AC-DC converter. When capacitor voltage is used as output for feedback control, the control system has the characteristics of a non-minimum phase system. In light of these factors that affect the dynamic stability of the system, a control method is proposed to improve the dynamic characteristics of the system without affecting its steady-state performance. The predictive PI control strategy was adopted to predict the error input signal of the lag process to attenuate the jitter in the control system and improve the dynamic performance and anti-interference of the system. Finally, the feasibility of the scheme was verified by experiments.