Single-phase Voltage Source Inverter Research Articles

Optimal Performance Design Guideline of Hybrid Reference Frame Based Dual-Loop Control Strategy for Stand-Alone Single-Phase Inverters

The dual-loop control strategy in a hybrid reference frame (HRF) for single-phase voltage-source inverters in islanded operation mode is studied, which applies a capacitor voltage shaping loop in the synchronous reference frame (SRF) and a capacitor current shaping loop in the stationary reference frame (HRF-based $v+ i_{c}$ control strategy). This strategy is able to achieve the purpose of active damping, fast dynamic response, and zero reference tracking error. However, due to the inherent characteristics of SRF-based voltage loop and the digital control delay, the performance of the system is degraded and the control parameter design of the HRF-based $v+ i_{c}$ control strategy shows great difficulties. To overcome these shortcomings, in this paper, a systematic parameter design guideline for the HRF-based $v+ i_{c}$ control strategy is proposed to ensure the system stability and optimize the performance of the system under control delay condition. The mathematic model of the HRF-based $v+ i_{c}$ control strategy is established with the consideration of control delay in this paper. Based on this model, a satisfactory region of the system stability indexes can be obtained by stability specifications of the system, and the optimal control parameters can be calculated according to the stability indexes selected from the satisfactory region. By using this method, the system stability and robustness can be guaranteed. Finally, the experimental results are presented to validate the effectiveness of the presented optimal control parameter design methodologies.

Model-Based Predictive Current Control Method with Constant Switching Frequency for Single-Phase Voltage Source Inverters

Voltage source inverters operated by predictive control methods generally lead to a variable switching frequency, because predictive control methods generate switching operation based on an optimal voltage state selected at every sampling period. Varying switching frequencies make it difficult to design output filters of voltage source inverters. This paper proposes a predictive control algorithm with a constant switching frequency for the load current control of single-phase voltage source inverters. This method selects two future optimal voltage states used in the subsequent sampling period, which are a zero-voltage state and a future optimal voltage state, based on the slope of the reference current at each sampling period. After selecting the two future voltages, the proposed method distributes them to produce a constant switching frequency and symmetric switching pattern. The performance of the proposed method is validated with both simulation and experimental results for single-phase voltage source inverters.

A Novel CH5 Inverter for Single-Phase Transformerless Photovoltaic System Applications

Versatile single-phase voltage source inverters with unipolar voltage pulse and leakage current elimination capability have been extensively investigated for transformerless PV systems in the literature. However, the innovative current source inverters with leakage current elimination capability are not well explored. In this brief, a novel single-phase current source H5 (CH5) inverter is proposed. Only one extra IGBT is needed, but the leakage current can be significantly suppressed with a novel space vector modulation. Finally, the experimental tests are carried out on a single-phase CH5 inverter and the experimental results verify the effectiveness of the proposed topology and space vector modulation.

Performance and stability analysis of grid connected single phase inverters used in solar photovoltaic systems

Single-phase voltage source inverters (SP-VSIs) are widely used in grid connected solar photovoltaic (PV) systems. This paper deals with the dynamic modeling and stability analysis of single-phase grid connected PV inverters taking the PLL dynamics into account. The PLL structure employed in this paper includes two control branches; the main branch, known as phase estimation loop, extracts the phase and frequency of the grid voltage and the other branch, known as voltage peak estimation loop, determines the grid voltage amplitude. In this way, the paper first proposes design considerations for the dc-link voltage control and PLL control loops. Then, unified dynamic modeling of the SP-VSI system comprising PLL, dc-link dynamics and grid is presented and linearized block diagram of the whole system is extracted. The linearized block diagram depicts the interaction between the control loops of the PLL and dc-link system, where the PLL control loops consist of phase/frequency and amplitude estimation loops of the grid voltage. Next, the small signal stability of the full system is presented, and impacts of grid strength, operating point, and PLL closed loop bandwidth on the performance of SP-VSI are investigated by the modal analysis and time domain simulations.

Adaptive Notch Filter-Based Multipurpose Control Scheme for Grid-Interfaced Three-Phase Four-Wire DG Inverter

The power electronic converter and its control system form an integral part of distributed generation (DG) systems interfacing renewable energy sources to the utility network. This paper proposes an adaptive notch filter-based multipurpose control scheme for grid interfacing DG inverter under corrupted grid conditions. The proposed control scheme uses a frequency adaptive sequence components extractor, which is capable of extracting instantaneous symmetrical components and harmonic components of three-phase signals. The DG inverter in this study consists of three single-phase voltage source inverters with common dc bus and coupled to utility grid via three single-phase transformers. The proposed control scheme enables the DG inverter to perform multiple tasks such as reference power injection to grid, low voltage ride through, load reactive power support, and compensation of harmonic, unbalanced, and neutral currents. The efficacy of the proposed control scheme is evaluated through MATLAB/Simulink simulations and experimentally verified using a hardware-in-the-loop based system.

High‐efficiency voltage source converter with low switching power losses for application in islanded microgrids

In the conventional inverter, the switching power losses cause the inverter efficiency to decrease at high switching frequencies. In this study, a new structure of a single-phase voltage-source inverter with low switching losses is proposed, for application in islanded AC grids. This converter is composed of two single-phase series inverters, with different switching frequencies. The main feature of the proposed converter is that, the total losses of the proposed converter are fewer than the total losses of a conventional single-phase inverter, at high switching frequencies. The proposed converter is designed by the appropriate power transistors in the market. By providing a suitable method for calculating the transistor power losses, the switching and conduction losses of the proposed converter are calculated, and compared with losses of a conventional single-phase inverter. The mathematical model of the proposed converter is derived and used along with root-locus and frequency-response analysis, for designing the controllers. The performance of the proposed converter has been assessed using the simulation studies in MATLAB/SIMULINK software environment.

Sliding ModeControl of Dc/Dc Switching Converters for Photovoltaic Applications P

Maintaining good voltage regulation at output and having fast dynamic response under sudden load fluctuation are extremely important in distributed generation (DG) as well as uninterrupted power supply (UPS) systems. This paper presents a fixed frequency hysteresis current (FFHC) controller, which is implemented on the basis of sliding mode control (SMC) technique and fixed frequency current controller with a hysteresis band. The controller has the benefit of hysteretic current control having fast dynamic responses and reduces the disadvantages of the variable switching frequency. To overcome elliptical sliding surface was taken. These has been verified and compared with the carrier based pulse width modulated (PWM) voltage controller under the same load fluctuation. The proposed method is then applied to islanded single phase voltage source inverter (VSI) system. The results show that the dynamic response is quite faster than that of widely used PWM-controlled inverter systems. The DC voltage that is required for the inverter input is supposed to be given from the output of PV panel with buck converter. In PV system ,sliding mode control is used to track the maximum power point .Here inverter and buck converter connected to PV array are taken separately.

Grid synchronization and control of distributed generation unit with flexible load compensation capabilities using multi-output LMS-filter

This paper deals with grid synchronization and control of single-phase voltage source inverter in distributed generation (DG) systems using a multi-output adaptive filter. Besides the active power injection, the proposed control enables the inverter to compensate load harmonic and reactive currents based on the capacity of inverter. The currents to be compensated are obtained using a multi-output adaptive filter structure that operates on the principle of variable step size (VSS) least mean squares (LMS) algorithm. The main objective of VSS-LMS filter is to decompose the load current into harmonic and reactive current components and compute their RMS values. The currents extracted by the VSS-LMS filter are used in developing a flexible compensation based on load compensation factors. The load compensation factors are calculated based on the remaining capacity of the inverter and priority. Harmonic currents compensation is given first priority over the reactive currents. In addition to harmonic currents detection, the same VSS-LMS filter is used in developing a phase locked loop unit for synchronizing the inverter with fundamental point of common coupling (PCC) voltage. Synchronizing the DG inverter with fundamental PCC voltage would make the proposed control algorithm insensitive to grid voltage harmonics and frequency fluctuations. The feasibility and the efficacy of the proposed control algorithm are demonstrated using hardware-in-the-loop (HIL) based experiments.

Model Predictive Current Control of Single Phase Shunt Active Power Filter

A Model Predictive Current Control (MPCC) of single phase Shunt Active Power Filter (SAPF) is introduced in this paper. A single phase Voltage Source Inverter (VSI) is used as a SAPF to compensate the current harmonic and reactive power. A DC link capacitor voltage regulation based Proportional - Integral (PI) control algorithm is adopted for determining the reference current. A bridge rectifier with RL and RC loads are acting as a Non-Linear Loads (NLL). The harmonic compensation performance of SAPF and associated control methods like switch on response and transient responses were verified through a simulation with MATLAB software.

Analysis and MPPT control of a wind‐driven three‐phase induction generator feeding single‐phase utility grid

In this study, a three-phase diode bridge rectifier and a single-phase voltage source inverter topology has been proposed for feeding single-phase utility grid employing a three-phase induction generator fed from wind energy. A self-excited induction generator configuration has been chosen for wide speed operation of wind turbine system, which gives the scope for extracting maximum power available in the wind. In addition to maximum power point tracking (MPPT), the generator can be loaded to its rated capacity for feeding single-phase utility grid using a three-phase induction machine, whereas it is not possible with existing configurations because of the absence of power converters. For the proposed system, MPPT algorithm has been devised by continuously monitoring the grid current and a proportional resonant controller has been employed for grid synchronisation of voltage source inverter with single-phase grid. A MATLAB/Simulink model of the proposed system has been developed to ascertain its successful working by predetermining the overall performance characteristics. The present proposal has also been tested with sag, swell and distortion in the grid voltage. The control strategy has been implemented using field programmable gate array (FPGA) controller with modularised programming approach. The efficacy of the system has been demonstrated with the results obtained from an experimental set-up in the laboratory.

Design and experimental investigation of digital model predictive current controller for single phase grid integrated photovoltaic systems

Depletion of fossil fuel reserves has lead to identification of renewable sources of energy as alternative sources of energy for power generation. The photovoltaic plant is more prominent in present day scenario. The power electronic converters interfacing the photovoltaic generator with the grid gives rise to various power quality problems such as harmonics in current injected by the inverter into the grid and low output power factor. This paper focuses on the design, analysis and control of single phase grid integrated photovoltaic systems. In this paper a dual stage photovoltaic inverter system is simulated using MATLAB/SIMULINK software. A digital predictive current controller based on model predictive control theory with delay compensation technique is introduced for output current control of the single phase voltage source inverter integrating the photovoltaic generator with the grid. The proposed control strategy exhibits excellent steady state performance and attains a high output power factor. It also achieves very fast transient response during change in reactive power demands and grid voltage distortions. The efficacy of the proposed controller is validated by experimental implementation using low cost digital signal processor.

A Novel Current Control Technique for Photo Voltaic Integrated Single Phase Shunt Active Power Filter

In this paper, a Model Predictive Current Control (MPCC) of single phase Photo Voltaic (PV) integrated Shunt Active Power Filter (SAPF) is proposed. A PV integrated single phase Voltage Source Inverter (VSI) is used to generate a part of the real power and compensate harmonics, reactive power of a Non-Linear Load (NLL). In this paper, a DC link voltage regulation based PI control algorithm is adopted for determining the reference current at the filter side. The performance of SAPF with PV and associated control methods like switch on response and change of nonlinear load were carried out. Also, the performance of the controller has been examined with variation in irradiance, filter inductance value and variation in controller sampling time through a simulation in MATLAB software.

Power quality enhancement of single phase grid tied inverters with model predictive current controller

Recognition of renewable energy sources as alternative sources for power generation has augmented the number of distributed generation plants being incorporated into the conventional power distribution system. The single phase voltage source inverter allying the distributed generation plant with the grid has to address various issues related to the quality of current injected into the grid, output power factor, and power exchange between the plant and the grid. This paper focuses on the analysis, design, and implementation of a digital predictive current control technique known as model predictive current controller for the control of single phase power inverter integrating renewable energy based plant with the grid. The proposed controller is tested in diverse operating conditions and is compared with the existing proportional resonant current control scheme. The simulation and experimental results validate the efficacy of the proposed control technique.

Stand-alone photovoltaic system with grid interfacing capability

This paper presents a single-phase photovoltaic (PV) system consisting of a bi-directional dc-dc converter (BDC) converter and a single-phase voltage source inverter (VSI). A PV panel act as primary source and a battery bank act as secondary source. The PV panel is operated at its maximum power point (MPP) by a maximum power point tracking (MPPT) controller. The boosted dc output voltage of the BDC is maintained constant using a voltage controller. This voltage is converted to ac by the VSI. In the presence of grid power and PV power, the battery bank absorbs charging power from the PV panel. The excess power available on the PV panel is delivered to the utility grid. In the absence of grid power, the load absorbs power from the PV panel or battery bank based on the level of solar irradiation. The proposed system rated for 250 Wp, 34.4 V, 9 A has been analysed in MATLAB/SIMULINK and the performance is compared in open and closed loop modes for various irradiations. THD in the ac output voltage and current is minimized using a passive LC filter.

Sampled-Time-Domain Analysis of a Digitally Implemented Current Controlled Inverter

This paper presents a sampled-time-domain analysis to investigate the sampling effect on instantaneous switching frequency of a digitally implemented hysteresis current control (HCC) in a voltage source inverter (VSI). The generalized expression of the instantaneous switching frequency with the consideration of sampling frequency has been derived. The effect of variation in sampling frequency on effective hysteresis band and switching frequency has been analyzed. The difference between maximum to minimum switching frequency of a fixed-band HCC VSI depends on the sampling frequency of the digital controller. The sampling also generates a steady-state tracking error exceeding the fixed-band limit at the fundamental frequency for fixed hysteresis band operation. The analysis has been done to achieve fixed switching frequency with variable hysteresis band and with varying sampling period. The frequency spectrum of the load current is presented to show the effect of a digital controller. The sampling effect on the switching performance has been demonstrated for a single-phase VSI under different loading conditions. To verify the analytical results, the simulation and experimental results are obtained with the current controller implemented on a field programmable gate array-based digital controller.

A Cost-Effective Harmonic Cancellation Method for High-Frequency Silicon Carbide MOSFET-Based Single Phase Inverter

This paper introduces a combinational modulation method to be used in classic full-bridge single phase inverters. The proposed method eliminates even-order harmonics at the pulse width modulation (PWM) stage in the control section, unlike the conventional method of even order harmonic cancelation in the power stage, and offers a cost-effective design by switching one leg at high frequency. Using a low-cost digital signal controller platform, a regular sampling technique based on real-time calculation was employed to verify the feasibility of the proposed method on a 500-W single phase voltage source inverter. Performance characteristics, such as switching losses and harmonic distortions, are presented for the new approach and compared with a classic inverter modulation method.

Model predictive current controller for performance enhancement of grid-integrated single-phase photovoltaic distributed generation plants

Acknowledgement of renewable sources of energy as substitute energy sources for power production has expanded the number of distributed generation plants being incorporated into the conventional power distribution system. The single-phase voltage source inverter allying the photovoltaic plant with the grid has to address various issues identified with the quality of current injected into the grid, output power factor and power exchange between the plant and the grid. This paper concentrates on the investigation, design and implementation of a digital predictive current control technique known as the model predictive current controller for the control of single-phase photovoltaic distributed generation plants. The performance of the controller is evaluated under varied operating conditions. The proposed current controller is compared with the conventional proportional–integral controller in terms of its design methodology, steady state and dynamic response. The simulation and experimental results validates the effectiveness of the proposed model predictive current controller.

Single-Phase Inverter for Grid-Connected and Intentional Islanding Operations in Electric Utility Systems

Small distributed generation units are usually connected to the main electric grid through single-phase voltage source inverters. Grid operating conditions such as voltage and frequency are not constant and can fluctuate within the range values established by international standards. Furthermore, the requirements in terms of power factor correction, total harmonic distortion, and reliability are getting tighter day by day. As a result, the implementation of reliable and efficient control algorithms, which are able to adjust their control parameters in response to changeable grid operating conditions, is essential. This paper investigates the configuration topology and control algorithm of a single-phase inverter with the purpose of achieving high performance in terms of efficiency as well as total harmonic distortion of the output current. Accordingly, a Second Order Generalized Integrator with a suitable Phase Locked Loop (SOGI-PLL) is the basis of the proposed current and voltage regulation. Some practical issues related to the control algorithm are addressed, and a solution for the control architecture is proposed, based on resonant controllers that are continuously tuned on the basis of the actual grid frequency. Further, intentional islanding operation is investigated and a possible procedure for switching from grid-tied to islanding operation and vice-versa is proposed.

Distorted Waveform Balancing Using an Artificial Bee Colony (ABC) Based Optimal Control for Mitigating Total Harmonics in Single Phase Inverter

The main objective of this paper is to reduce the total harmonics in a single phase voltage source inverter using Artificial Bee Colony (ABC) optimization technique for critical load applications. Single phase inverter is a non-linear load using power electronic components causing distortions in the load voltage and current wave patterns from the sinusoidal waveforms due to harmonics. The mapping state space model for a full bridge voltage source inverter was developed using output load resistance. An optimal ABC technique has been designed and optimized values are estimated using a full bridge voltage controlled inverter using Proportional Integral Algorithm. The MATLAB/SIMULINK tool and Experimental setup were implemented and their THD values were estimated. Also this ABC scheme is compared with the previous results such as PI Algorithm, Fuzzy logic controller and Neuro-fuzzy controllers. From the simulation and experimental results using ABC algorithm, it is observed that the total harmonics are mitigated considerably compared to previous results with respect to the power quality standards such as IEEE-519 and IEC 61000.

Power-Electronics-Based Energy Management System With Storage

This paper demonstrates the functionality of a power-electronics-based energy management system (EMS). The EMS includes batteries and a digitally controlled single-phase voltage source inverter (VSI), which can be controlled as a current source or a voltage source depending on the status of the ac grid and the user's preference. The EMS guarantees that the critical loads are powered when the ac grid fails; in which case, the VSI is controlled as a voltage source. It also accomplishes peak power control by supplying battery power to the local loads while they are powered by the ac grid if the loads get large. The electricity cost savings accomplished by peak shaving are estimated. The EMS functionality is demonstrated by experimental measurements on a laboratory prototype. The control architecture and logic embedded in the EMS are discussed in detail.