Single-phase Current Source Inverter Research Articles

Research on the Modulation and Control Strategy for a Novel Single-Phase Current Source Inverter

Compared to the voltage source inverter, the current source inverter (CSI) can boost voltage and improve filtering performance. However, the DC side of CSI is not a real current source, and the DC input current comprises a DC power supply and an inductor. In the switching process, the DC-link inductor is charged or discharged and is in an uncontrollable state. This paper proposes a novel CSI topology containing five switching tubes and a modulation strategy based on the hysteresis control strategy of the DC-link current. Due to the conduction and switching loss being positive to the DC-link current, the calculation method for the least reference value of the DC-link current is derived to meet power requirements. By constructing a virtual axis, we then present the control strategy of the output voltage in a two-phase rotating reference frame. Finally, we carry out the simulation and experiment are to validate the proposed topology, modulation, and control strategy.

Modeling a Simple Single-phase Grid-connected Photovoltaic System Using Negative Conductance of Solar Cells

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.

Single-Phase Current Source Inverter with Reduced Ground Leakage Current for Photovoltaic Applications

Integrated power electronics for photovoltaic applications has attracted increasing interest, due to the possibility of having grid-connected photovoltaic modules with independent maximum power point tracking and high reliability. In this paper, a single-phase Current Source Inverter (CSI) is discussed for a photovoltaic application. The basic CSI topology will be explained for the sake of completeness, highlighting its main features and analyzing the ground leakage current problem, an important benchmark for photovoltaic application. A novel topology, called CSI5, is proposed in this work. The main feature is the presence of additional switches for ground leakage current reduction. The performance of the proposed topology is assessed by numerical simulation, and the experimental results confirm that this solution is able to strongly reduce the ground leakage current and conduction power losses.

Pure Sinusoidal Output Single-Phase Current-Source Inverter with Minimized Switching Losses and Reduced Output Filter Size

This paper proposes a novel single-phase current-source inverter that generates a pure sinusoidal waveform with minimized switching losses and using a small-size output filter capacitor. The proposed method is investigated by incorporating a conventional multilevel current-source inverter with a linear amplifier. The conventional multilevel technique uses fundamental switching frequency instead of using high-switching frequency modulation for the H-bridge circuit. The linear amplifier such as class-A or class-D types has a function to reform the staircase waveform generated by the multilevel inverter into a pure sinusoidal by using superimposition technique. As a result, pure sinusoidal output current is generated with a small ripple and the system only requires a small output filter capacitor for smoothing the waveform. Based on the simulation and experimental results, the proposed system presents not only the optimal configuration, but also an option as to whether to obtain excellent power efficiency or very low output harmonic. Implications of the results and future research directions are also presented.

High-level number multilevel single-phase current-source inverter with reduced switching device count

This paper proposes an advanced technique in generating a pure sinusoidal output current waveform for the high number multilevel lsingle-phase current-source inverter (CSI) with reduced switching device count. Previous multilevel CSI development proposed a new technique in generating pure sinusoidal output by compensating the staircase current with a linear current. This linear current compensation intends to reduce the output filter capacitor size without sacrificing inverter efficiency. However, this hybrid multilevel CSI would give higher efficiency and performance if applie in high number of levels. Consequently, the system needs high switching device count. Too many switching devices utilization will decrease the performance and the power density of the CSI as well. Therefore, this technique is introduced and only possible to be realized if the number of levels is higher than 5-level. By applying multilayer stagemethod while managing the DC current module activation sequences, the high number of levels CSI can be constructed with only using few DC current modules. As a result, according to the computer comparison simulation, the implementation of the proposed technique delivers relatively equal results compared to the conventional one just by utilizing fewers witching devices.

A Programmable Single-Phase Multilevel Current Source Inverter

The conventional single-phase multilevel current source inverters suffer from the high count of switches for increasing the levels. Therefore, how to generate more levels with reduced-count of switches is attractive. In this paper, a programmable single-phase current source inverter is presented. It can achieve the programmable level output with only five switches. Different from the existing single-phase reduced-count multilevel inverters, it has the advantages of a simple structure and programmable level output. Finally, the simulation and experimental tests are carried out. And, the experimental results verify the effectiveness of the proposed programmable multilevel inverter.

Multi-Port Current Source Inverter for Smart Microgrid Applications: A Cyber Physical Paradigm

This paper presents a configuration of dual output single-phase current source inverter with six-switches for microgrid applications. The inverter is capable of delivering power to two independent set of loads of equal voltages or different voltages at the load end. The control strategy is based on integral sliding mode control (ISMC). The cyber twin model-based test bench is developed to analyze the performance of the inverter. The cyber twin is a virtual model of the physical system to simulate behaviours. The performance of the inverter is analyzed with a cyber twin model and monitored through the remote system. Also, the inverter is analyzed with different voltage conditions.

A Transformerless Single-Phase Current Source Inverter Topology and Control for Photovoltaic Applications

Low power grid-tied photovoltaic (PV) generation systems increasingly use transformerless inverters. The elimination of the transformer allows smaller, lighter and cheaper systems, and improves the total efficiency. However, a leakage current may appear, flowing from the grid to the PV panels through the existing parasitic capacitance between them, since there is no galvanic isolation. As a result, electromagnetic interferences and security issues arise. This paper presents a novel transformerless single-phase Current Source Inverter (CSI) topology with a reduced inductor, compared to conventional CSIs. This topology directly connects the neutral line of the grid to the negative terminal of the PV system, referred as common mode configuration, eliminating this way, theoretically, the possibility of any leakage current through this terminal. The switches control is based on a hysteresis current controller together with a combinational logic circuitry and it is implemented in a digital platform based on National Instruments Technology. Results that validate the proposal, based on both simulations and tests of a low voltage low power prototype, are presented.

A New Single-Phase Transformerless Current Source Inverter for Leakage Current Reduction

A new single-phase transformerless current source inverter is proposed in this paper. The proposed inverter can achieve leakage current reduction, which is crucial for the conventional current source inverter. The basic concept of the proposed solution is to develop the new inverter by the duality principle from the voltage source inverter. The theoretical analysis is carried out to determine the switching states of the proposed inverter for the leakage current reduction. Also, a new modulation strategy is presented to achieve the optimized switching states. Finally, the experimental results are presented. Comparing with conventional single-phase current source inverter, the leakage current can be significantly reduced by the proposed inverter, which verifies the effectiveness of the proposed solution.

Single Phase Current Source Inverter With Multiloop Control for Transformerless Grid–PV Interface

In this paper, a modified single-phase current source inverter (CSI) with improved multiloop control is proposed for a transformerless grid-photovoltaic interface application. A split capacitor arrangement with the middle point connected to the grid neutral and a common mode choke are used to modify the conventional CSI structure to attenuate the ground leakage current. The proposed control method permits the use of reduced value of dc side inductor by maintaining the quality of the grid current as if a high value of input inductor is used. Furthermore, virtual resistance damping is incorporated in the control loop to reduce the effect of LC resonance without compromising the efficiency, thus proving the feasibility of using CSI for the grid interface. Rigorous study, analysis, and validation of the modified CSI structure with the proposed control technique are carried out with exhaustive simulations and experiments. The experimental results on a 250 W laboratory prototype using the controller TMS320F28335 prove the effectiveness of the proposed CSI structure and its control.

Analysis and Design of a Control Strategy for Tracking Sinusoidal References in Single-Phase Grid-Connected Current-Source Inverters

A novel control strategy for single-phase current-source inverters connected to an ac grid is proposed in this paper. The control strategy aims to inject maximum power to the grid under transient and steady-state conditions by the tracking of sinusoidal references. This paper presents the modeling and the design of the control strategy based on the exact linearization of the inverter model. Results are obtained by computational simulation and validated experimentally. By using error performance indexes in the analysis of the results, it is demonstrated that the proposed controllers achieve correct tracking of the sinusoidal reference while keeping a low switching frequency, which helps to minimize the commutation losses.

Performance analysis of a low-cost current-source 1-ph grid-connected PV inverter

This paper investigates the design and performance of a 150 W single-phase current-source grid-connected inverter topology that is based on a PV array and DC link inductor acting as a constant-current source. The inverter is implemented using a single boost switch, an H-bridge inverter, and a CL output filter. The inverter output current is simply controlled using the boost switch and open-loop or feedforward control. The dark I-V configuration is used to simulate two series PV modules. Comprehensive test results are obtained to validate the computer simulation results. Furthermore, the proposed inverter's ability to deliver a sinusoidal current to the grid while meeting the appropriate standards, i.e. total harmonic distortion and power factor requirements, is also examined for various modulation index values and irradiances.

A Single-Phase Current-Source PV Inverter With Power Decoupling Capability Using an Active Buffer

This paper proposes a new circuit configuration and a control scheme for a single-phase current-source inverter with a power decoupling circuit which is called as the active buffer. The proposed inverter achieves a low-dc-input voltage ripple and also provides a sinusoidal current that can achieve unity power factor, without large passive components in the dc bus such as smoothing inductors and electrolytic capacitors. These components are conventionally required in order to decouple the power pulsation caused by the single-phase power source. In this paper, the fundamental operations of the proposed inverter are demonstrated experimentally. From the experimental results, the input voltage ripple is 8.87%, and the output current total harmonic distortion is 4.24%. In addition, an output power factor of 99% and a maximum efficiency of 94.9% are obtained. Finally, it is confirmed that the maximum power densities of the conventional circuit and the proposed circuit are 2.75 kW/L at the switching frequency of 70 kHz and 4.86 kW/L at the switching frequency of 80 kHz, respectively.

Three-phase STATCOM based on a single-phase current source inverter

This paper presents a three-phase STATic synchronous COMpensator (STATCOM) based on a current source inverter. Instead of the typical three-phase current bridge inverter it is used a power converter topology with only a single-phase current bridge inverter. A dynamic model of the STATCOM in αβ coordinates is used as a basis for control design. The control system uses a cascade structure where a fast ac current inner loop and a slow dc current control outer loop is used. For the inner loop, is used a sliding mode technique to generate αβ space-vector modulation. This fast and robust controller the ac currents of the STATCOM are actively shaped, being possible to maintain the desired currents even with high ripple DC inductor current. For the outer loop, is used a PI controller. Computer simulations are presented allowing validating the proposed STATCOM and their control system.

Integral sliding-mode-based current-control strategy for single-phase current-source inverters

This paper proposes two current-control strategies adopting the sliding-mode concept for single-phase current-source inverters (CSI) feeding a resistive load. The first strategy is based on forming a general sliding surface using the error variables of the inductor current and capacitor voltage. However, it is observed that with this type of control there exists a steady-state error in the capacitor voltage. Therefore, an integral sliding-mode-based current control using an additional integral term of the error variables in the sliding surface is proposed. It is observed that the additional integral term alleviates the steady-state error in the capacitor voltage. The existence conditions for stability are determined for both control strategies. It is shown that the compliance of the existence conditions for full operating range of the CSI can be assured if the complete ranges of operating conditions are taken into consideration. In order to reduce the switching losses and improve the quality of the output voltage, the three-level hysteresis function is implemented as two separate two-level functions for the switching devices. Computer simulations are performed to verify the theoretical results and for comparison with existing methods. Experimental results are also presented to support the theoretical considerations.

A Configuration of Single-phase PWM Current Source Inverter Circuit with Step-Down Chopper

This paper presents a single-phase current source inverter with step-down chopper. The chopper circuit is connected to the inverter leg and its operation contributes to get a sinusoidal output current. This inverter is applied to the utility interactive photovoltaic generation system. The experimental result proves that the proposed inverter has the smooth dc current and the sinusoidal current under the small value of the dc reactor.

Digital simulation of a single phase current source inverter with a counter EMF inductive load

Abstract The steady state operation of a single phase current source inverter is analysed. A transition diagram for the modes is given. The equivalent circuits and differential equations for various modes are derived. A flow chart for the simulation of inverter operation with a counter EMF load is given. The results of simulation are given in detail in the form of normalised circuit waveforms. Experimental results are given for the inductive and the counter EMF (motor) type of loads.

Time domain analysis of a current source inverter

A single phase current source inverter feeding an inductive load is analysed in detail, and design criteria for the inverter are worked out. It is found that the commutating capacitance needed is proportional to the square of turn-off time of the thyristors and a low commutating capacitance will permit the circuit operation for higher frequencies.