Validation of current source inverter with lesser input inductor for grid integrated photovoltaic system

This work deals with analyzing the performance of Electronically Commuted Motor (ECM) driven water pumping system powered by a Solar Photovoltaic (SPV) array with Z- Source Inverter (ZSI) and quasi-Z source inverter (q-ZSI). The Induction motor (IM) driven water pumps can be replaced by the ECM driven water pumps due to its several advantages over IM. Also, the ZSI and q-ZSI have various advantages over Current Source Inverter (CSI) and Voltage Source Inverter (VSI) as it provides better shoot through states which in turn provides a single stage power conversion. The propriety of systems is cleared through its simulation analysis using MATLAB.

This paper presents an analysis of current source inverter (CSI)-based unified power quality conditioner (UPQC) to improve the electric power quality at distribution levels. In recent years unified power quality conditioner (UPQC) is being used as a universal active power conditioning device to mitigate both voltage as well as current harmonics in a polluted power system network. Fabrication of UPQC is done implying both current source and voltage source inverter. Current source UPQC has unique advantages over generalised voltage source-based UPQC. Reference and switching signals are derived using a simple PI controller and robust hysteresis band PWM technique respectively. The resultant compensation system eliminates voltage as well as current harmonics with good dynamic response. Extensive simulation results using MATLAB/Simulink and SimPowerSystems software for R-L load connected through an uncontrolled bridge rectifier is presented for performance evaluation.

Current source inverter (CSI) features simple converter structure and inherent voltage boost capability. In addition, it provides low instantaneous rate of voltage change with respect to time in comparison to voltage source inverter (VSI) and multilevel inverter (MLI). Nonetheless, CSI does not outshine as grid interfacing unit in photovoltaic (PV) generation system. This is because of requirement of large sizing of dc-link inductor and sluggish performance during light load condition. Contemplating both advantages and disadvantages of CSI, this work is aimed to investigate and analyze the superiority of CSI in PV system. The proposed system employs direct regular-sampled pulse width modulation (DRSPWM) as modulator and multi-loop proportional-integral (PI) in synchronous frame as the controller. The grid-connected CSI system is further evaluated along with photovoltaic maximum power point tracking (PV-MPPT) control. Simulation verification highlighted that the option of using CSI as medium power PV grid integration unit in exchanging active-reactive power with grid network is very satisfactory. In addition, balanced sinusoidal output currents with acceptable harmonic limit are successfully achieved; like other topologies in PV grid integration. The proposed CSI system is proved to be able to track the references in event of varying input condition from PV array. The theoretical equations and modeling are described, and the simulation are conducted in MATLAB / Simulink platform.

Solar energy, which is abundant, easier to obtain and non-pollution etc, has a broad application prospect in photovoltaic power generation system. In traditional photovoltaic grid-connected power generation system, voltage source inverter(VSI) which needs extra voltage-boost link to achieve grid-connected criterion, is more used, not only increasing the power dissipation but also making the circiut structure more complex. However, the current source inverters(CSI) feature voltage-rise itself, which can both realize the maximum power point tracking and grid-connected criterion. This paper focuses on the single-phase current source inverter. Single-Phase current-source PWM grid-connected inverter is established for the research and the linear quadratic(LQ) optimal control method is applied to this inverter, which solved the transient oscillation defect of current source inverter. Through the method combined by computer simulation and experimental study, a laboratory prototype of 400W current source inverter has been implemented and tested. Results of simulation and experiment show that this method can make output AC currents sinusoidal and in phase with grid voltages.

The operation of a distributed maximum power point tracking (DMPPT) photovoltaic (PV) system with a current source inverter (CSI) is confirmed. We proposed a current-linked distributed PV system instead of a voltage-linked one. All the previous studies of DMPPT PV systems use a voltage source inverter (VSI). Moreover, all commercial power optimizers that are provided by Solar Edge, Solar Magic, Tigo Energy, and so on are assumed to be connected to a VSI. The drawback of the power conditioning system (PCS) with a VSI is that it has to carry an electrolytic capacitor, which determines the life span of the PCS. By using a CSI, the reliability of the PCS is greatly improved; moreover, the module integrated converter (MIC) can consist of a buck-only converter. In this paper, we implemented two cascaded MICs with a CSI and confirmed the operation of the entire current-linked distributed PV system. The experimental results agree strongly with the theory and it proves the validity of the proposed system.

This paper introduces a novel circuit configuration of multilevel current-source inverter (CSI) that has many steps with fewer power switches. In this new topology, an H-bridge CSI is connected with current-cell circuits working to generate the intermediate level currents of multilevel current waveform. Using the proposed topology, the switching power device count, isolated gate drive circuits and inductor conduction losses can be reduced. Moreover, in order to reduce the inductor size of the multilevel CSI, chopper based DC current sources are presented. Five-level and seven-level PWM inverter configurations are examined through computer simulations. Furthermore, an experimental prototype of a five-level CSI is setup and is tested. The results show that the circuit works properly to generate the multilevel output current waveform with low harmonic currents and small inductors which proves feasibility of the proposed multilevel CSI.

This paper represents the new topology and hardware modeling of Embedded-Z (EZ) source feed industrial drives and comparative analysis of Z source and EZ-source inverter. In industrial application conventionally there are two converters used for ASD systems i.e. Voltage Source Inverter (VSI) and Current Source Inverter (CSI), but they have a limited output voltage range. Conventional VSI and CSI support only either buck or boost DC-AC power conversion and need a relatively complex modulator. The problems in traditional source converters can be overcome by Z source inverter. In this LC impedance are employed for fast power conversion. Due to requirement of additional LC filter the cost of operation also increases. Therefore, instead of using an external LC filter in Z-source inverters, this paper gives an alternative family of Z-source inverters i.e. EZ-source inverter. In which input DC source has embedding between LC impedance, which perform the current and voltage filtering operation in current type and voltage type EZ source inverter. This paper illustrate the hardware design of EZ source inverter fed induction motor which overcome problems of conventional VSI and CSI inverters. And it gives the smooth speed control of induction motor.

Traditionally, current source (CS) inverters have been adopted for use in medium and high power industry applications. These inverters, however, support only current-buck dc-ac power conversion and need a relatively complex modulator, as compared to conventional voltage source (VS) inverters. To address these limitations, this paper presents an integration of the buck-boost Z-source power conversion concept to the CS inverter topology to develop single- and three-phase Z-source CS inverters. For their efficient control, the paper starts by evaluating different carrier-based reference formulations to identify different inverter state placement possibilities. The paper then proceeds to design appropriate "reference-to-switch" assignments or logic equations for mapping out the correct CS gating signals, allowing a simple carrier-based modulator to control a Z-source CS inverter with complications such as commutation difficulties and "many-to-many" state assignments readily resolved. The developed system can be implemented using a digital signal processor with an embedded VS pulse-width modulator and an external programmable logic device, hence offering a competitive solution for medium power single and three-phase buck-boost power conversion. Theory, simulation, and experimental results are presented in the paper

In this paper, a nonlinear adaptive controller for regulating the grid of a current source inverter (CSI) based three-phase grid-connected photovoltaic (PV) system is proposed. The proposed control structure is composed with an outer control loop-responsible for controlling the DC-side inductor current and the inner current control loop-responsible for controlling injected current into the utility grid. The proposed adaptive controller is designed recursively by considering external disturbances within the system and these unknown external disturbances are estimated through the adaption laws. The overall stability of the whole CSI based three-phase grid-connected PV system is verified by formulating the control Lyapunov functions (CLFs) at different stages throughout the design process of the proposed controller. Finally, the performance of the designed controller is tested on a similar CSI based three-phase grid-connected PV system under different atmospheric conditions. Simulation results demonstrate that the proposed control scheme can effectively meet the desired control objectives as compared to the existing controller in terms of settling time and power quality.

To enlarge the use of grid-connected PV systems, the cost, performance, and life expectancy of the power electronic interface needs to be improved. The current-source inverter (CSI) offers advantages over VSI in terms of inherent boosting and short-circuit protection capabilities, direct output current controllability, and ac-side simpler filter structure. Research on CSI-based DG is still in its infancy. This paper focuses on transient performances of a PV system based on CSI during the rigorous LL and TPG (Three- phase- to-ground) faults. It also performs a comparative analysis of CSI-based PV systems for severe LL and TPG (Three-phase- to- ground) faults under transient conditions. The control structure consists of two current control loops. An MPPT provides the reference for the outer dc-side current control loop. The inner current control loop is designed to control the current that is injected into the grid. Using a case study of grid-side faults i.e., LL, TPG, the designed controller is able to fulfill all the requirements of a PV system grid interface besides limiting the dc- side current, irrespective of the severity of the fault, unlike a VSI-based PV system. The fault studies included line-to-line and three-phase-to-ground faults.The case study of this paper is presented by using a Mat lab / Simulink environment, the respective results also shows the differences between the behaviour of a system at the time of encountering faults. Keywords - Current source inverter (CSI), Controller, Faults, Grid, PV System, transient conditions.

The paper proposes a new circuit configuration of multilevel current-source inverter (CSI). In this new topology, a basic H-Bridge CSI working as a main inverter is connected in parallel with inductor-cells operated as auxiliary circuits. The inductor cell is composed by four unidirectional power switches with an inductor across the cell circuit. The inductor-cells work generating the intermediate level currents to obtain a multilevel current waveform without additional external DC power sources. A simple PI controller is applied to control the intermediate level currents of multilevel output waveform. Five-level and nine-level PWM inverter configurations, with chopper based DC current source, are verified through computer simulations. Furthermore, an experimental prototype of a five-level CSI is setup and is tested. The results show that the proposed circuit works properly to generate the multilevel output current waveform with low harmonics distortion by using small inductors.

The design and simulation results of three-phase differential current-source inverter is presented in this paper. It is shown that three modules of current-source converter could be configured and controlled to obtain a symmetrical three-phase at the output. The current source inverter could be used with lower voltage sources. It could also be possible to integrate all three transformers and reduce the 60 Hz component saturation effect. The structure is modular and can be used as three dc-dc converter in parallel, one symmetrical three phase inverter, single-phase inverter or split-phase inverter based on the application.

A photo-voltaic (PV) system based grid-connected current source inverter has been investigated in this paper. In this paper, a photovoltaic (PV) system based grid-connected current source inverter has been investigated. For obtaining the maximum power from the PV system, we have developed a Lyapunov energy function-based control scheme. Operation of the system under unbalanced grid voltage condition has been reported and a methodology to extract maximum power from the PV system is articulated. In addition, to achieve optimal performance of the Lyapunov energy function based power controller, an existing parameter update scheme is employed and an optimal performance of the overall system is achieved. Detailed analysis of the proposed power controller with the feature to operate successfully under unbalanced grid voltage condition has been substantiated and discussed along with the effect of parameter update on the overall control architecture. The proposed system is verified via software simulations in MATLAB/Simulink and PLECS domain and various case study results are presented which corroborate the efficacy of the proposed framework.

Traditionally, current source (CS) inverters have been adopted for use in medium and high power industry applications. These inverters however support only current-buck dc-ac power conversion and need a relatively complex modulator, as compared to conventional voltage source (VS) inverters. To address these limitations, this paper presents an integration of the buck-boost Z-source power conversion concept to the CS inverter topology to develop single and three-phase Z-source CS inverters. For their efficient control, the paper starts by evaluating different carrier-based reference formulations to identify different inverter state placement possibilities. The paper then proceeds to design appropriate "reference-to-switch" assignments or logic equations for mapping out the correct CS gating signals, allowing a simple carrier-based modulator to control a Z-source CS inverter with complications such as commutation difficulties and "many-to-many" state assignments readily resolved. The developed system can be implemented using a digital signal processor with an embedded pulse-width modulator and an external programmable logic device, hence offering a competitive solution for medium power single and three-phase buck-boost power conversion. Theory, simulation and experimental results are presented in the paper.

This paper presents the simulation of a simple single-phase grid-connected photovoltaic (PV) system using the PSPICE model. The modeling system consists of a PV string, a single-phase current source inverter (CSI), load, and a grid voltage source. The system uses the PV string as the current source. The single-phase CSI was controlled by the grid AC voltage. The operation of the system employs the negative conductance characteristics of the PV string. We studied the voltage and current waveform at the inverter output terminal, the current waveform at the load, the AC power with various open-circuit voltages and temperatures of the PV string. The result showed the current waveform at the inverter output terminal follows the I-V characteristics of the PV string. The current waveform at the load depends on its impedance characteristics. The AC power increased with the open circuit voltage. We found that the maximum efficiency of the AC power conversion system was 63.3% at the peak of the AC voltage source, which was equal to the maximum power voltage of the PV string. In addition, the prototype was built for testing and testing verified the simulation results. The experimental results showed the current waveform at the inverter terminal and load were similar to the simulation results.