GaN‐Based Three‐Phase Voltage and Current Sources for Power Relay Testing

Nonlinear loads are always needed to operate electrical equipment. Example, motor drives, inverters, rectifiers, etc. However nonlinear loads can create electrical power quality problems such as harmonic. Harmonics has two sources, voltage source and current source. To reduce voltage harmonic distortion, a shunt passive filter can be used. Meanwhile, to reduce harmonic current distortion can use a series passive filter. What if there is harmonic case that has voltage and current source, a combination of series and shunt passive filters is needed. There are two types of passive filters, namely single tuned shunts and C-type passive filters. The first model uses combination of series and shunt single tuned passive filter. Next this combination is called HPF1. The second model uses combination of series and C-type passive filters. Next this combination is called HPF2. The third model uses Harmonic Power Sharing (HPS). Then all of these combinations are tried in case studies. The results of the experiment are that HPF2 has the best results of all models in reducing THD and IHD-V, but HPF1 has the best results than all models in reducing TDD and IHD-I. Although the TDD values are not too much different.

Modern societies would not survive without electricity and at the same time electrical faults could cause and have caused many catastrophes—mainly deadly fires—to our societies. There are two types of electricity sources: the voltage source such as generators, charged batteries and capacitors, and the current source such as charged inductors, current-regulated rectifiers, and superconducting magnetic energy storage. An “ideal” voltage source—that is often-sought-or-intentionally engineered—generates a constant voltage irrespective of its load current, and an “ideal” current source injects a constant current irrespective of its load voltage. However, two problems exist: (1) voltage or current sources do not represent many emerging natural/renewable energy sources such as wind turbine generators, photovoltaic cells, and fuel cells, whose output voltage and current are strongly dependent on each other, and (2) a short-circuit fault to an artificially-made and controlled “ideal” voltage source or an open-circuit fault to an “ideal” current source can cause catastrophic failures of the source itself and its surrounding circuits due to large (theoretically infinite) short-circuit current or open-circuit voltage. Here we introduce an impedance source concept to represent, characterize, and model those electricity sources whose output voltage and current are strongly dependent on each other. First, we found that many electric sources with no feedback (or active) control of their output voltage and/or current are a natural impedance source with inherent fault protection at short-circuit or open-circuit faults. Second, any electrical source can be artificially controlled to mimic a natural impedance source. Finally, we show how to apply natural impedance sources and nature-mimicking artificially-controlled sources to the electricity grid—the most complex machine ever made by human beings—to realize electricity grids that are naturally stable, self-protected against electrical faults, and resilient to natural and human-made events.

Many combinatorial optimization problems such as the min cost flow problem are equivalent to the solution of appropriate DC circuits made up of positive resistors, voltage sources, current sources and ideal diodes. Simulating the DC circuit is an alternative approach to the approximate solution of such problems. However, conventional simulators such as SPICE are too slow for this purpose. This paper describes the structure and performance of a fast DC analyzer built at EE department, IIT Bombay specifically for solving large circuits consisting of positive resistors, voltage sources, current sources and diodes. Using the simulator, we have analyzed circuits composed of diodes, positive resistors, current and voltage sources of size up to 700,000 nodes and 1.2 million edges on a 3.0 GHz, 1GB RAM, PIV processor in at most 1.2 hrs. We also report a comparative study of the performance of our DC analyzer with that of fastest commercial simulator.

This paper describes a method to avoid the singular problem at the “S‐control” algorithm. The “S‐control” is proposed to determine the correct operating state in any bipolar transistor network (BTN). Each diode of the Ebers‐Moll model is replaced with a directional switch called an S‐branch which has “on” and “off” states. The switch status is changed by the S‐control algorithm. However, the matrix singular problem occurs in the process of the S‐control. The singular matrix is formed by a cutset of only current sources or a loop of only voltage sources. The singular problem is solved by the signdiscrimination method by which the sign of each node voltage is judged by the introduction of small immittances in cutset (loop) of only current (voltage) sources formed in process of the S‐control. The S‐control algorithm will be continued to obtain the next switch state unless the limit cycle is not generated.

– We propose a fast simulation model of wind generator with a frequency converter, such as a doubly-fed type. The aim of the model is to provide a model that can evaluate an impact of wind generator system (WG) on utility side in both transient and relatively long term normal operation. Through, some simulation software based on root mean square value, for example EUROSTAG, provides a unified method that can handle both short-term and long-term analysis. But it is difficult for RMS based model to handle with a behavior of WG with a frequency converter under system fault condition. So we have developed an instantaneous value based fast simulation model that can handle with both short-term and relatively longer-term analysis.. Keywords : Wind power generation, Fast simulation model, Simplification for converter 1. Introduction The integration of wind generator system (WG) has large influences over a variety of operational conditions. These operational conditions vary from short-term, such as a transient behaviour during a fault, to longer-term, such as power fluctuation under a normal operation. In order to harness WG successfully, the impact of WG must be analyzed in both short and long term. As a result, both short-term and long-term simulation models for WG are required, and it is high burden in view of cost and maintenance. For longer-term analysis, the focus point is mainly active and reactive power swing due to wind fluctuation, and a simulation model based on root mean square value (RMS) is suitable. There are already some RMS based simulation tools that can handle with both long and short term analysis, such as MATLAB. But, in short-term analysis, a simulation model for WG should be represented in detail manner, and a model based on an instantaneous value is appropriate. Because, under a fault condition, WG with FRT(fault ride through) function acts in complex manner, and the behavior during a fault condition could have a large impact over a subsequent longer-term situation. It means that a simulation model for WG based on an instantaneous value is suitable. But it is very time consuming to conduct a long-term analysis with a model based on an instantaneous value. To solve this problem, we have developed and evaluate a fast simulation model for WG based on an instantaneous value that can handle with relatively longer-term analysis. In this study, we first developed a simulation model for WG to conduct both short-term and long-term analysis. Our aim of the model is to evaluate an impact of WG on utility side. The developed model is doubly-fed type. It includes pitch control, frequency conversion, start-up and shut-down function, and FRT(Fault Ride Through) so that we can evaluate WG under a various operational conditions. Then we applied a simplification method to the simulation model so that the model can handle with relatively longer-term analysis. The method of simplifica-tion is to model self-commutated converters in frequency converter as a pair of voltage and current source. The AC side of converter is represented as a voltage source, whereas the DC side of converter is represented as a current source. Through this kind of simplification may be popular in simplifying a self-commutated converters, we do not see any report that evaluates this simplification method under various operational conditions of WG. So, we evaluate this simplification method in this study.

This paper deals with the implementation of an indirect current control of a parallel hybrid filter (PHF) system with rectifier load to eliminate generated harmonics. The compensation principle, design, and PHF implementation are discussed in detail. The proposed control enhances the performance of the passive filters (PFs) under unbalanced situations that are existing in the PFs under fault conditions. Moreover, due to a limited capacity of voltage source inverter, an upper limit for such compensation may be imposed by the proposed indirect current control based on synchronous reference frame employing decomposition of current in synchronously rotating reference frame that is used to control PHF. The PHF is controlled using decomposition of load and source currents. The implementation of the control scheme is carried out on dSpace with digital signal processor for developed prototype of the PHF. PFs are developed keeping in view its operation with the PHF, so that the total harmonic distortion in the source current gets minimized along with minimized fundamental-frequency current sinking through the filter section. The design has been carried out by genetic algorithm, which optimizes the solution for multiple constraints. The operation of the PHF under dynamic change of load is also investigated through simulations under MATLAB and through experimentation.

If the renewable source is connected to utility, a current source (CS) is required. The conventional converter design is based on a voltage source (VS). A voltage source has a dual relationship with a source, so this paper takes the dual principle as the basis and uses the dual approach to propose converters based on the current source. The duality theory can be used to convert the switched inductor (SI) structure into a switched capacitor (SC) structure, that is convert a step-up voltage topology into a step-up current topology.In this paper, taking the Single Ended Primary Inductive Converter (SEPIC) converter as an example, the conventional voltage source SEPIC converter is converted into a current source SEPIC converter, and then the capacitor is replaced by a step-down switched capacitor structure to form a current source switched capacitor (CSSC) converter. The input current of the proposed topology is Iin=1 A~5 A, and the switching frequency is 100 kHz. Maximum output current Io is 15 A, and the output power is 1125 W. The efficiency can be at least 90.62 %.

Standard converter topologies are usually presented with a voltage source as the input supply to the converters. However, a photovoltaic (PV) array has the I-V characteristics of a current source not a voltage source. This thesis details the design process of modifying the standard Buck and synchronous Buck converter topologies to function with either a voltage or current source input, making them universal DC-DC step down converters. This is accomplished by placing a capacitor at the converter's input to supply the pulsating current required for the Buck topologies to function properly. The equations for determining the capacitor's size and RMS current rating are derived, and a prototype of each topology was constructed and analyzed. Also, the issues that arose during the integration of the converter's into the SuPER system are discussed. The Cal Poly Sustainable Power for Electrical Resources (SuPER) project seeks to build a stand alone photovoltaic (PV) unit that can supply the energy needs of a single family home. Before the start of this thesis the SuPER project was using an off-the-shelf DC-DC converter to step down the PV array's voltage, perform maximum power point tracking, and act as a charge controller for the battery. One goal of the project is to have a Cal Poly built DC-DC converter that can perform all the functions of the off-the-shelf DC-DC converter currently being used.

The solar energy has become an easily accessible source for electricity generation due to its characteristics preventing pollution, decreasing the carbon emission, and lower manner of maintenance requirements. The most significant components of a photovoltaic (PV) power conversion system is the inverter that can be configured in central, string or micro topologies. Nowadays, the micro inverters which brings advantages and drawbacks are one of the most extensively researched devices. In this study, the micro inverter which is comprised by flyback converter and H-bridge sections is designed and analyzed in terms of reliability and efficiency. The switching control of flyback converter is performed by using Incremental Conductance based Maximum Power Point Tracking (IC MPPT) algorithm while switching pulses of H-bridge are generated with Sinusoidal Pulse Width Modulation (SPWM). Both simulation and implementation of the designed micro inverter have been realized in this study. The input voltage of flyback micro inverter is obtained from a single PV module at 50 V dc whereas output voltage is generated at 220 V ac 50 Hz for single-phase lines. The proposed flyback micro inverter which has LC filter is firstly simulated with MATLAB Simulink software. The efficiency and THD ratio of simulated micro inverter are respectively obtained as 0.35 and 94%. The performance of implemented flyback micro inverter is investigated with LC and LCL filters in terms of output voltage quality. The THD ratios of output voltage are acquired 4.41% and 2.57% with LC and LCL filters while the efficiency of designed flyback micro inverter is measured around 82.3%.

A novel control strategy for mode seamless switching of PV converter in DC microgrid based on double integral sliding mode control

In the multi-output high-voltage isolated power supply for solid-state switches, LCL resonant network is used to obtain the constant current source on the bus, and the bus current is independent of the load. Therefore, the secondary side of the toroidal transformer needs to use the current input voltage regulator circuit. When the input is a current source instead of a voltage source, the traditional voltage regulator circuit is no longer applicable. Therefore, this paper focuses on the study of dc voltage regulated circuit with current source input. Compared with the traditional linear regulated power supply, switching power supply has the advantages of high efficiency, large output power, small size, light weight and low cost. In this paper, pulse width modulation (PWM) technology is used to control the switching on and off, and UC3843 is used to design a switch type regulated power supply with small size, simple circuit, adjustable output and over voltage protection function. Tina-TI software was used for simulation analysis, and the main circuit and control circuit were built. The current source of 1.25A and 40kHz output by the secondary side of the toroidal transformer is converted into a stable 10V DC voltage source, which verified the correctness of the design. Tina-TI software can be used to analyze and design power supply with different requirements, improve power efficiency, reduce design complexity, and thus shorten development cycles.

A newly investigated technique for the tuning of the tunnel resistance of nanogaps using electromigration method induced by a field emission current is presented to reduce the power consumption during the process. The method is called "activation" and is demonstrated with a current source. Planar-type initial nanogaps of Ni separated by 20-80 nm were defined on SiO2/Si substrates via electron-beam lithography and the lift-off process. Then, a bias current was applied to the initial nanogaps at room temperature, using a current source. The applied current was slowly ramped up until it reached the preset value. As a result, the process time of the current-source-based activation was 16 times shorter than activation using a voltage source. Furthermore, the tunnel resistance of the nanogaps was reduced from 100 T ohms to 70 M ohms by increasing preset current I(s) from 1 nA to 3.5 microA. Regarding the average power required for current-source-based activation, it can be successfully suppressed compared with that of voltage-source-based activation. These results imply that the current source directly and precisely tunes the field emission current passing through the nanogaps, and effectively causes the migration of atoms across the nanogaps, resulting in the successful control of the tunnel resistance of the nanogaps.

Although the circuit in the conventional switched capacitor (SC) current source (SCCS) is extremely simple, the output current ripple incresaes if the input frequency is reduced. This paper proposes a new reduced ripple SC current source (RRSCCS) in which an integrator circuit is added to the conventional circuit to reduce the ripple. The output current from the proposed circuit can be determined by the voltage, frequency and capacitance as in the conventional circuit. In addition, no current ripple occurs theoretically in the new circuit. As examples of applications, a frequency‐controlled voltage source (FCVS) and a current source proportional to the square of the frequency (F2CCS) are constructed. In the present FCVS, the output voltage can be made proportional to or inversely proportional to the frequency depending on the input frequency and the control frequency. Since the output voltage is determined by the capacitance ratio, frequency ratio and voltage, it is of high precision. Next, it is shown that the present F2CCS is useful for linear control of gm of the MOS‐type OTA. Good results have been obtained by experiments using individual components.

Most inverters designed to date can only perform either voltage-buck or boost operation with buck-boost mode usually attained by introducing additional active semiconductor devices and passive components to the inverters. Although effective, adding active switches will complicate the inverter control, and push up the overall system costs. Therefore, alternative topological solutions are of interest, and should preferably be implemented using only passive LC elements and diodes, connected as unique impedance networks. A number of possible network configurations are now investigated in this paper, and are respectively named as Z-source, H-source, EZ-source and their respective inverted variants. The presented impedance networks can either be used with a traditional voltage- source or current-source inverter, and can either be powered by a voltage or current source. All impedance networks are shown to produce the same voltage gain under the same operating conditions, but structurally, they have their respective advantages and disadvantages, which are thoroughly described throughout the paper. Experimental results captured using a laboratory prototype are also presented for confirming the practicalities and performances of the described impedance networks.

Peculiarities of the time dependence of the plasma parameters of a pulsed discharge with a hollow cathode in low-pressure argon were experimentally determined when using two types of pulsed high-voltage power sources – voltage and current sources (pulse duration up to 10 ms, voltage up to 10 kV). It is shown that the use of pulsed current sources provides significantly more stable discharge glow in the working range of argon pressure variations (2.5…10)10-4 Torr. At the same time, the temperature of plasma electrons of the discharge which was powered by a voltage source, was several times higher and could reach 40 eV.