In this paper particle swarm optimasation algorithm (PSO) based sliding mode controller(SMC) introduced to control invrters of Uniefied power quality Controllers(UPQC) to control and improve the power quality in microgrids through controlling the output power of the dis More
In this paper particle swarm optimasation algorithm (PSO) based sliding mode controller(SMC) introduced to control invrters of Uniefied power quality Controllers(UPQC) to control and improve the power quality in microgrids through controlling the output power of the distributed generation source. In the proposed control scheme, the standard sliding mode controller (SMC) is used as a robust nonlinear controller, with the addition of the particle swarm optimization (PSO) algorithm - to determine the optimal parameters of the SMC controller. Using PSO added extra advantages like reducing chattering problems and increasing accuracy and tracking capability to the commonly knowns SMC benefits. To confirm the accuracy of the proposed controller's performance, computer simulation is performed under different system load conditions in the MATLAB/Simulink software environment. The obtained results show the effectiveness of the proposed control compared to the standard sliding mode controller in reducing harmonics, reducing voltage imbalance and improving other power quality indicators.
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In this paper, a fourth-order, OTA-free, single-bit, low-consumption discrete-time (DT) delta-sigma (ΔΣ) modulator with CIFF structure is proposed for hearing aid applications. In portable medical devices such as hearing aids that are used permanently, the b More
In this paper, a fourth-order, OTA-free, single-bit, low-consumption discrete-time (DT) delta-sigma (ΔΣ) modulator with CIFF structure is proposed for hearing aid applications. In portable medical devices such as hearing aids that are used permanently, the battery life and energy dissipation are very important. In a typical delta sigma modulator, the power-hungry parts are the OTA. Therefore, the elimination of OTAs is a challenge, and the proposed modulator uses new differential parametric amplifiers, with dynamic thresholde in even stages and inverter-based amplifiers in odd delta sigma stages instead of the OTAs. The dynamic threshold PMOS technique has been used for the first time in differential MPA, and the theoretical analyzes and simulations performed show better performance than the traditional method. Also, a chopper circuit is used on the first fstage to reduce the harmonics and flicker noise. The proposed differential modulator is simulated using standard 180 nm CMOS technology, which achieves 90.5 dB SFDR and 64 dB SNDR with an input bandwidth frequency of 10 kHz and an oversampling ratio of 128. The power supply is 1V and the FOMW were obtained as 3.43 PJ/step.
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Solar energy is the world's most unique and affordable renewable energy source and can be converted into many other forms. In this article, it will be discussed in a long-term perspective the technical and economic feasibility of installing stand-alone solar power plant More
Solar energy is the world's most unique and affordable renewable energy source and can be converted into many other forms. In this article, it will be discussed in a long-term perspective the technical and economic feasibility of installing stand-alone solar power plant units with battery support to supply part of Baghdad's electricity. The objective function of this problem includes the cost of installation and maintenance of solar panels, batteries and inverter, which is solved with a certain interest rate in a 20-year perspective using IPSO and ALPSO methods. Furthermore, the load loss supplied and the charging/discharging limit are among the constraints. This article is unique in that it is implemented in the context of Baghdad city, and it also investigates the possible profit from selling power to main grid. Other features and innovations include the implementation of the new ALPSO algorithm. In this algorithm, the constraints of the problem are respected through a three-step adaptive search process. The results show that the proposed methods significantly reduce the lost load (especially in the ALPSO method), reduce the cost of maintenance and installation, and generally improve the performance of the system.
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Identifying the location, magnitude of nonlinear loads, and the effects of harmonics is one of the most important parts of maintenance planning, troubleshooting, and modification of power systems. Therefore to determine the keying pattern of selective deletion of harmon More
Identifying the location, magnitude of nonlinear loads, and the effects of harmonics is one of the most important parts of maintenance planning, troubleshooting, and modification of power systems. Therefore to determine the keying pattern of selective deletion of harmonics, a new salp congestion algorithm has been used which has been applied to a 7-levels inverter and the results have been investigated in different cases. In the following, first, we discuss how to simulate the 7-levels inverter and the harmonic produced by it in MATLAB software, and then the results of the proposed design are reviewed. The results show that using the proposed design since the output line voltage of the 3phase inverter is used, the harmonic is reduced by more than 5% compared to the ground state. In this case, the overall harmonic value of the line voltage is approximately 14%, which has been reduced by 8.73% by normal implementation with offline calculations and by 8.43% by online calculations, which shows the accuracy and the performance of the proposed algorithm is to reduce the harmonic distortion at the output voltage…
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Global warming and environmental concerns have led to increasing penetration of converter interfaced renewable energy resources. One of the main challenges of inverter interfaced islanded microgrids is the fault detection. This paper investigates the performance of tota More
Global warming and environmental concerns have led to increasing penetration of converter interfaced renewable energy resources. One of the main challenges of inverter interfaced islanded microgrids is the fault detection. This paper investigates the performance of total harmonic distortion (THD) based fault detection scheme when various inverter topologies, main current limiting strategies, and different reference frame are employed. Then, based on this analysis, the performance of THD based fault detection scheme is improved using the instantaneous saturation limit and independent control capability in the natural reference frame. The proposed scheme does not mal-operate in the presence of non-linear loads and can distinguish fault condition from load change. Also, using the auxiliary control system, the proposed fault detection scheme is capable of detecting single line to ground fault in three wire system when synchronous/stationary reference frame is employed. Various time-domain simulations verify the effectiveness of the proposed scheme in the case of symmetrical and unsymmetrical faults.
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The multilevel cascade inverter is one of the most widely used power-electronics based interfaces in electrical distribution systems. Due to high losses and harmonics, the switching frequency of the inverter should be low in medium and high power applications. For this More
The multilevel cascade inverter is one of the most widely used power-electronics based interfaces in electrical distribution systems. Due to high losses and harmonics, the switching frequency of the inverter should be low in medium and high power applications. For this reason, the conventional carrier wave-based sinusoidal pulse modulation (PWM) and space vector PWM that have high switching frequencies cannot be used in these applications. The optimal PWM methods for inverters with step modulation result in lower total harmonic distortion (THD) in output voltage than other common modulation methods. However, one of the major disadvantages of these methods is that the optimal switching angles should be determined using the switching table, limiting the application of the optimal PWM. This paper proposes a method for determination of switching angles by using the iterative quadratic programming method. In each iteration, the proposed method calculates the switching angles by solving the quadratic sub equations with equality constraints and linear equations. Also in the appropriate conditions, global and asymmetric convergences are faster, more accurate, and more efficient, and there is no need for much time and memory for switching angles determination. The optimum switching angles minimize the switching frequency, switching losses, and THD in voltage and current of a three-phase cascade multilevel inverter with step modulation. Also, the power circuit breakers are switched on and off only once in each period. The effectiveness of the proposed method is evaluated through simulation case studies in MATLAB environment.
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Since integration of solar photovoltaic (PV) sources into the power grid is increasing rapidly in recent years, the capability of photovoltaic source inverters can be an opportunity to improve the technical and economic indicators via reactive power management in low vo More
Since integration of solar photovoltaic (PV) sources into the power grid is increasing rapidly in recent years, the capability of photovoltaic source inverters can be an opportunity to improve the technical and economic indicators via reactive power management in low voltage distribution networks grids. This work proposes an optimal planning model to improve the voltage deviation index and increase the revenue sale electricity with the capability of PV inverters and fixed capacitors. In this regard, the optimal capacity of the PV inverter is determined simultaneously with the location and number of fixed capacitors to minimize investment (for PV inverter, fixed capacitor, operating cost) and maximize electricity sales revenue. For this purpose, an innovative model is presented that is able to calculate the annual technical-economic evaluation. To make the costs for investment, operation and maintenance of compensating devices more realistic, the lifespan and additional cost of inverter oversizing in the objective function are modelled. In this article, load flow equations along with technical constraints are integrated into a mixed-integer second-order conic programming model. Two real grids were simulated using MATLAB software in order to show the effectiveness of the proposed model. The comparison of the proposed RPM method with conventional methods confirmed considerable reduction of investment and energy losses in the low voltage distribution networks grids.
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In this paper, an ultra-low-power, second-order, discrete-time sigma-delta converter is proposed for hearing aids application. In portable biomedical devices such as hearing aids that permanently use, the battery lifetime and power dissipation are very considerable. In More
In this paper, an ultra-low-power, second-order, discrete-time sigma-delta converter is proposed for hearing aids application. In portable biomedical devices such as hearing aids that permanently use, the battery lifetime and power dissipation are very considerable. In a typical delta-sigma modulator, the OTAs are the most power-consuming parts. The OTAs elimination in the converters is now challenging. Therefore the converter with a self-biased fully differential inverter-based amplifier was designed with only 1.15 µw static power dissipation at a 1-volt power supply. The inverter-based amplifier was used instead of the OTAs in two stages of the modulator. The modulator’s structure is CIFB, single-loop, and single bit. The proposed differential modulator was designed and simulated using a standard 180 nm CMOS technology, which obtained SFDR and SNDR of 95.2878 dB and 64.004 dB, respectively. The sampling frequency is considered 2.56 MHz, and the input signal bandwidth is 10kHz. The modulator consumes power just about 5.1091 µW, and the FOMW achieves 0.197 pj/step.
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Reducing the number of voltage sources and the power electronics components while obtaining voltage boosting in the output voltage are the key parameters in the research area of the multilevel inverter design. A lesser number of components would ensure lesser cost while More
Reducing the number of voltage sources and the power electronics components while obtaining voltage boosting in the output voltage are the key parameters in the research area of the multilevel inverter design. A lesser number of components would ensure lesser cost while higher boosting ability increases its application potential. In this paper, a new H-bridge based single-source switched capa­citor multilevel inverter structure is introduced. The proposed structure including two K-type units (KTU) can produce nineteen voltage levels with a voltage boosting of 1.5 times the input voltage. This converter consists of fourteen switches, two diodes, one voltage source and five capacitors with self-balancing capability. A comprehensive comparative comparison with the recent presented topologies have been carried out to investigate the performance of proposed structure. The main features of the proposed structure are utilizing single DC voltage source, self-balancing of the capacitors the capability of the input voltage, reducing the power electronics components in terms of voltage level count, and thus reducing the overall cost. The simulation results in the Matlab/simulink environment and the experimental laboratory results are provided to verify the satisfactory operation of the propo­sed topology.
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Floating photovoltaic (FPV) systems are a new approach to the use of water-based photovoltaic (PV) systems. This system creates a new opportunity to increase the production capacity of solar PV systems, especially in the northern regions of Iran, where the price of land More
Floating photovoltaic (FPV) systems are a new approach to the use of water-based photovoltaic (PV) systems. This system creates a new opportunity to increase the production capacity of solar PV systems, especially in the northern regions of Iran, where the price of land is high. To enhance the efficiency of inverters connected to the network of FPV systems in the northern regions of Iran, we have combined the structure of a two-stage and a multi-string inverter in this paper. On the other hand, the perturb and observe (P&O) method is one of the most common methods for maximum power point tracking (MPPT) with a variety of disadvantages including algorithm fluctuations during sudden changes in radiation. Since these sudden changes during radiation occur abundantly in the northern regions of Iran due to cloudy weather, a modified P&O algorithm is proposed by adding a current change parameter to overcome this problem. In fact, the ZETA converter and the proposed algorithm are used in inverter and track the maximum power point and in the second stage, DC to AC conversion occurs. To evaluate the efficiency improvement, the proposed inverter is compared with a single-stage centralized inverter. This study also considered the effect of wind and water temperature on the production capacity of the FPV system. System simulation is performed using Matlab/Simulink software. The simulation results show that the proposed two-stage multi-string inverter produce an average of 18.88 kWh, which is an increase compared to the centralized single-stage inverter.
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In this paper, a novel approach for comprehensive state-space modelling of the grid connected multi-level inverters is proposed. Details of the developed method is presented using cascaded H-bridge converters, however it can be applied to other topologies of the grid co More
In this paper, a novel approach for comprehensive state-space modelling of the grid connected multi-level inverters is proposed. Details of the developed method is presented using cascaded H-bridge converters, however it can be applied to other topologies of the grid connected inverters as well. In multi-level converters, due to their nonlinear characteristic, application of the nonlinear controllers is more beneficial to ensure stability of the system in a wide range of operation. Hence, the state-space model is required to design a nonlinear controller. To achieve converter model, it is divided into some sub-circuits considering different operational intervals in a switching cycle. To verify accuracy and effectiveness of the obtained state-space model, a laboratory setup of a multi-level. Converter with two H-bridges has been designed and implemented. Also, results of the developed state-space model has been compared with the simulation/experimental results of the grid-connected converter. According to the simulation and experimental result, accuracy of the model is verified. It should be noted that all of the simulations have been performed by EMTDC/PSCAD toolbox.
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With increasing the capacity and number of distributed energy resources (DERs), it is necessary to keep them connected to the microgrid during the disturbances. Two of the most important measures for satisfying this requirement are to provide the high quality voltage fo More
With increasing the capacity and number of distributed energy resources (DERs), it is necessary to keep them connected to the microgrid during the disturbances. Two of the most important measures for satisfying this requirement are to provide the high quality voltage for feeding the critical loads and to limit the electronically-coupled DERs current and voltage. This paper investigates the performance of hierarchical control structure of islanded microgrids during and after the fault conditions. The primary control level of this control structure is equipped with the hybrid reference frame limiting strategy to limit the voltage-sourced converter (VSC) current and voltage. The effect of employing the concept of independent control of natural reference frame in both primary and secondary control levels and the influence of using the conditional integration method in the voltage controller of secondary control level on the microgrid performance during and after fault condition are investigated. The study results are demonstrated through several time-domain simulations of symmetrical and asymmetrical faults.
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In this paper, a second order universal filter with the ability of electronically tuning central frequency (ω0) and quality factor (Q), based on the inverter as transconductance block which realizes multi-mode responses (voltage, current, transconductance, transre More
In this paper, a second order universal filter with the ability of electronically tuning central frequency (ω0) and quality factor (Q), based on the inverter as transconductance block which realizes multi-mode responses (voltage, current, transconductance, transresistance) in sub-threshold region, is presented. Biasing transistors in sub-threshold region, reduces the power consumption of the proposed filter and the grounded capacitors are used to reduce the parasitic effects which is another advantage of the proposed filter circuit. Furthermore, low sensitivity of the performance of the proposed filter to the values of gmi , Ci is considered as another advantage of the proposed circuit. In addition, realizing the proposed filter based on the inverter circuit leads to a reduced value of layout area as well as power consumption. Finally, the proposed filter performance is simulated in HSPICE using 0.18 µm (LEVEL49) CMOS technology parameters. As it is shown in the paper, the proposed filter consumes only 64.69 nW power in a ±0.3V supply voltage.
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In this paper, a low voltage and low power (LV/LP) Operational Transconductance Amplifier (OTA) using FGMOS (Floating-Gate MOS) transistor is proposed. The relative tuning range of 50 is achieved in this OTA while only consumes 40 µW with 1.0 V supply voltage in T More
In this paper, a low voltage and low power (LV/LP) Operational Transconductance Amplifier (OTA) using FGMOS (Floating-Gate MOS) transistor is proposed. The relative tuning range of 50 is achieved in this OTA while only consumes 40 µW with 1.0 V supply voltage in TSMC 0.18 µm CMOS technology. The simulation results of the proposed OTA show an open loop gain of 30.2 dB and a unity gain frequency of 942 MHz. In comparison with previous works, the proposed OTA, with lower supply voltage, is provided the better frequency performance, higher output voltage swing, better linearity and lower power consumption. The proposed OTA is used in the second-order filter to show a good tuning range from 100 kHz to 5.6 MHz which is suitable for the wireless specifications of Bluetooth (650 kHz),CDMA2000 (700 kHz) and Wideband CDMA (2.2 MHz). The active area occupied by the designed filter on silicon is .
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Direct torque control with Current Source Inverter (CSI) instead of voltage source inverter is so appropriate because of determining the torque of induction motor with machine current and air gap flux. In addition, Space-Vector Modulation (SVM) is a more proper method f More
Direct torque control with Current Source Inverter (CSI) instead of voltage source inverter is so appropriate because of determining the torque of induction motor with machine current and air gap flux. In addition, Space-Vector Modulation (SVM) is a more proper method for CSI because of low order harmonics reduction, lower switching frequency and easier implementation. This paper introduces the SVM method for CSI and uses the proposed inverter for vector control of an induction motor. The simulation results illustrate fast dynamic response and desirable torque and speed output. Fast and accurate response to changes of speed and load torque reference completely proves the prominence of this method.
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Recently to eliminate the harmonics and improve the power factor of the power networks, much attention has been attracted to active filters. The advantages of these filters are lower volume and their better compensating characteristics than the passive filters. In conve More
Recently to eliminate the harmonics and improve the power factor of the power networks, much attention has been attracted to active filters. The advantages of these filters are lower volume and their better compensating characteristics than the passive filters. In conventional sliding mode controllers, the source current waveform is fluctuated in near to zero values. In this paper, using a new sliding technique, lower Total Harmonic Distortion (THD) in source current is obtained and the current waveform is improved. As well as, two novel control strategies for two types of active filters, VSI and CSI is proposed and then these two types of filters are compared to reduce THD value of source current.The proposed controlled strategies are simulated by MATLAB/Simulink. The Simulation results confirm that the proposed strategies reduce the THD of source current more than other strategies, and active filter based on CSI has a better performance than active filter based on VSI with a dead time area (for avoiding short circuit of the source) in high powers.
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A UPS inverter operates in wide load impedance ranges from resistive to capacitive or inductive load. At the same time, fast transient load response, good load regulation and good switching frequency suppression is required. The variation of the load impedance changes t More
A UPS inverter operates in wide load impedance ranges from resistive to capacitive or inductive load. At the same time, fast transient load response, good load regulation and good switching frequency suppression is required. The variation of the load impedance changes the filter transfer characteristic and thus the output voltage value. In this paper, an analysis and simulation of the single phase voltage source uninterruptible power supply (UPS) with fourth order filter (multiple-filter) in output inverter, based on the state space averaging and small signal linearization technique, is proposed. The simulation results show the high quality sinusoidal output voltage at different loads, with THD less than %5.
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