DC-AC Inverter Research Articles

Characterizing the Effect of Conservation Voltage Reduction on the Hosting Capacity of Inverter-Based Distributed Energy Resources

The increased adoption of inverter-based distributed energy resources in the form of the mass deployment of renewable generation systems has been a focal goal of many jurisdictions worldwide. Actions taken by local governments have included adapted regulations, financial subsidies, and a variety of grants. This has spurred the proliferation of solar generation among residential customers in virtually all provinces of the United States and Canada. Needless to say, these small generators are interfaced with DC–AC inverters, which have evolved tremendously since the formation of working groups targeting the impact of inverter-based generation on the grid. Among the first rules and standards are California’s ISO Rule 21 and the UL1741 SA, which were published in September 2017. IEEE followed suit in 2018 with the revision of IEEE 1547, inspiring virtually all jurisdictions to either adopt these standards or adapt them as their own variants. Among many features, these standards mandate inverters to be fitted with autonomous performance functions, including the constant power factor, voltage-reactive power (Volt-VAR), voltage-active power (Volt-Watt), and grid support functions, as well as provisions for compatibility with control centers. These functions have been demonstrated to increase the nameplate hosting capacity. At the same time, grid modernization strategies have become more prevalent, one of which is the use of conservation voltage reduction. This grid modernization initiative has a great impact on the hosting capacity. Conversely, the increased penetration of distributed energy resources has a negative effect on the conservation voltage reduction, but surprisingly to only a limited extent. The characterization of these impacts is addressed in this paper, with a focus on a case with very high DER penetration and with very long daily sunlight hours.

Design of constant output voltage DC-AC inverter for batteryless solar PV system

This paper introduces a DC-AC inverter design that operates stand alone to deliver power from solar photovoltaic (PV) to the load directly without going through the battery. In batteryless solar PV, the output voltage of solar PV always varies according to solar irradiation, temperature, so that it becomes a challenge in modelling DC-AC inverter with constant output voltage. The design consists of a boost converter, h-bridge switching and driver, and LC filter to generate sinusoidal ac voltage as output to load. To ensure a constant inverter output voltage, the design equipped by a close loop PI controller based on voltage control mode. The design modelled and simulated by PSIM. PV dc input was set variation according to the irradiation value (W/m2) and the output connected to a load that has rated voltage of 220 Vac and 3.4 A of nominal current. The results show that in the irradiation variation 600-1500 W/m2, the inverter was able to maintain the output voltage of 220 Vac ± 0.91%, 50 Hz which is still in the voltage range based on standard. The efficiency produced by DC-AC inverter 97.7 % at 600 W/m2 and 83.6 % at 1500 W/m2.

Application of CUK and ZETA Dc-Dc Choppers for Power Factor Correction and Power Quality Improvement of BLDC Motor

For industrial, electrical vehicles, drives, and grid applications ac-dc based inverters with power factor correction is considered as a key element to meet the power system firm regulatory rules. Among these dc-ac inverters, bridgeless converters play a vital role. In this paper, Bridgeless cuk and zeta converter-fed brushless dc (BLDC) motor drive is studied for power factor correction (PFC) and power quality improvement. The major objectives of this work are (i) dc bulk capacitance and inductance use is decreased, so that permanence film capacitors can be utilized, (ii) overall efficiency of BLDC drive system is improved due to decreased losses in the switches and conducting devices and (iii) guaranteed high or unity source power factor. The motor and source parameters are examined in this study for PFC using CUK and ZETA based dc-dc converters with MATLAB software. The work is compared with bridgeless ZETA, CUK and

Single phase PV system operating under Partially Shaded Conditions with ABC-PO as MPPT algorithm for grid connected applications

Single phase transformerless grid connected Photovoltaic (PV) systems have become prevalent in recent years because of the reduced size & volume and enhanced working efficacy. A single phase two stage grid connected PV system is successfully implemented under Partially Shaded Condition (PSC), Standard Test Conditions (STC) and load variations in this work. The first stage includes the use of a MPPT controller-based DC–DC boost converter. Artificial Bee Colony integrated Perturb & Observe (ABC-PO) MPPT algorithm is used to obtain maximum power from the photovoltaic module. ABC-PO is capable of tracking Global Maximum Power Peak (GMPP) even under PSC. A DC–AC inverter along with LC filter and Phase Locked Loop (PLL) is used in the second stage to synchronize with the grid. A small scale grid connected solar power generation system with a maximum capacity of 1kW power output has been considered for analysis. The simulation results validate the efficient maximum power point tracking characteristics of ABC-PO algorithm over ABC algorithm for a grid connected network. Moreover, the successful synchronization of grid current with grid voltage under variations in irradiance as well as load has been carried out. The result shows the satisfactory performance of the entire system.

A NOVEL BIDIRECTIONAL QUASI Z SOURCE INVERTER FOR ELECTRIC VEHICLE APPLICATIONS

The fixed frequency sliding mode control method for this project is a single-phase grid-connected LCL filtered quasi-Z-source inverter (QZSI). In the proposed method, smoothing is applied to the function of the sliding surface, thereby eliminating jitter and achieving a fixed switching frequency. The smoothing process is performed by passing the function of the sliding surface through a narrow boundary layer. To mitigate steady state errors due to smoothing, a PIC controller is used to handle current grid errors and determine the capacitor voltage reference required in the SMC. The DC output of the battery is converted to AC using a DC AC inverter after withstanding or increasing demand. The inverter function must change the DC input voltage to the desired voltage and voltage as the asymmetric AC output voltage achieved through the control branches of Quasi by using simple boost control technology.

Seven‐level power conversion system for solar power generation system

This study proposes a seven-level power conversion system for a solar power generation system. This seven-level power conversion system consists of a DC–DC power converter and a cascade DC–AC inverter. The cascade DC–AC inverter comprises a full-bridge inverter and a T-type inverter. The T-type inverter generates a three-level quasi-square-wave voltage and the full-bridge inverter provides a three-level high-frequency pulse voltage. The amplitude of the three-level quasi-square-wave voltage is double that of the three-level high-frequency pulse voltage, so seven levels of AC voltage are synthesized. Only the full-bridge inverter with lower DC bus voltage uses high-frequency switching so switching losses are effectively reduced. The novelty of the proposed cascade DC–AC inverter is that the output power of T-type inverter is controlled by regulating the DC bus voltage, so no real power is supplied from the full-bridge inverter and an independent power source is not required to provide power to the full-bridge inverter. The negative terminal voltage for solar cell array keeps almost constant to reduce the leakage current of proposed seven-level power conversion system. A hardware prototype with a digital signal processor controller is developed to verify the performance of seven-level power conversion system for a solar power generation system.

High-performance single-input three-output DC–DC high gain converter for fuel cell-based electric vehicles

The electric vehicle (EV) requirement has various glitches and solutions in EV technology. Alternate energy that delivers the required power to the EVs is derived from the fuel cell with high performance. Nevertheless, the output voltage obtained from the fuel cell system is very less, and it is not enough to drive the motor of the EVs. The DC–DC converter increases the output voltage of the fuel cell system, and the EV also requires a different output voltage for the entire system. The DC–DC converter for fuel cell-based EVs requires high voltage gain with high conversion efficiency. However, the converter based on single-input three-output (SITO) DC–DC unidirectional converter can reduce loss and the cost of the system, and hence the overall efficiency. In this paper, a new single power-switch-based SITO converter topology is proposed to improve the voltage gain and conversion efficiency. The converter presented in this paper acts as a front-end DC–DC converter for the DC–AC inverter, and it supplies power to the auxiliary DC loads or for charging the auxiliary battery in EV. The converter has a single-stage voltage multiplier cell with a voltage clamp circuit to improve the voltage gain with soft-switching to reduce the loss, and hence the efficiency. The proposed converter is operated with a single MOSFET switch which delivers three different output levels with less voltage stress across the switch is the main feature of the proposed converter. The theoretical analysis is validated through the experimental results, and results verify that the proposed converter is best suitable for EV applications.

Dynamic Response of DC-DC and DC-AC Inverters Controlled with ZAD-FPIC

This article presents the behavior of an inverter in both DC-DC and DC-AC configurations controlled with a quasi-sliding control technique known as ZAD-FPIC. An analysis of transient behavior, disturbances in the load, changes in the reference signal, and disturbances in the power supply are presented, and control techniques have been designed to manage an inverter in real-time. The software has been designed to execute the controllers by using Simulink-MATLAB libraries and the ones provided when installing the DS1104 board. The digitally implemented ZAD-FPIC controllers use a DS1104 in order to control the converter and thus meet the requirements of fixed switching frequency, robustness, and good performance in DC signal regulation tasks. The controllers work well during the transient state because they dampen overshoots and reduce settling times. The results show that the system regulates well before changes of the reference and rejects disturbances in the load and the source voltage. Additionally, it has been observed that the regulation error varies depending on the reference voltage level.

Variable structure-based control of fuel cell-supercapacitor-battery based hybrid electric vehicle

• Fuel Cell-Supercapacitor-Battery based Hybrid Electric Vehicle ahas been considered. • Double Integral Sliding Mode non-linear controller for output voltage regulation of DC Bus in HEVs has been proposed. • Using Lyapunov Stability Theory, asymptotic stability of the proposed controller has been proved. • The comparison is done with other controllers in the literature has been given. Hybrid electric vehicles (HEVs) are getting attention due to their importance in the transport Industry. Clean energy generation and effective utilization is rapidly growing research area. Fuel cell based electric vehicles have many advantages over conventional vehicles. The fuel cell is a massive source of clean energy that overcomes the issues of conventional vehicles such as; global warming and high fuel cost. The hybrid energy storage system (HESS) of the proposed vehicle consists of three power sources; fuel cell (FC), battery, and a supercapacitor (SC) which are connected to the DC bus through the DC-DC power converters. DC bus is further connected to DC-AC inverter which is used to run the electric motor of vehicle. In this paper, three nonlinear controllers namely; Sliding Mode Controller (SMC), Integral sliding mode controller (ISMC) and Double integral sliding mode controller (DISMC) have been proposed to achieve the desired control objectives. The purpose of ISMC and DISMC is to eliminate the steady-state error and mitigate the chattering effect inherent in SMC. The main objectives of proposed controllers are; tracking of battery and supercapacitor currents to their reference values, voltage regulation of DC bus and the global stability of the system. The proposed controllers have then been simulated using MATLAB/Simulink to analyze their comparative performance. It is noted that DISMC could alleviate the steady-state error significantly.

Review of Control techniques in Distributed Power Generation Systems

In this document are revised different control techniques applied to distributed generation systems, including control of active-reactive power, load-frequency control and the identification and control of island mode operation of the generation units, which are the main themes identified. The different control strategies identified are PID, robust, predictive and fuzzy, with applications in the aforementioned subjects. Particularly, applications for the interconnection of generation units and the control of the electric power conversion system DC-AC (inverter) are observed.

Continuous dynamic sliding mode control strategy of PWM based voltage source inverter under load variations

For closed-loop controlled DC-AC inverter system, the performance is highly influenced by load variations and online current measurement. Any variation in the load will introduce unwanted periodic error at the inverter output voltage. In addition, when the current sensor is in faulty condition, the current measurement will be imprecise and the designed feedback control law will be ineffective. In this paper, a sensorless continuous sliding mode control (SMC) scheme has been proposed to address these issues. The chattering effect due to the discontinuous switching nature of SMC has been attenuated by designing a novel boundary-based saturation function where the selection of the thickness of boundary is dependent to the PWM signal generation of the inverter. In order to remove the dependency on the current sensor, a particle swarm optimization(PSO) based modified observer is proposed to estimate the inductor current in which the observer gains are optimized using PSO by reducing the estimation errors cost function. The proposed dynamic smooth SMC algorithm has been simulated in MATLAB Simulink environment for 0.2-kVA DC-AC inverter and the results exhibit rapid dynamic response with a steady-state error of 0.4V peak-to-peak voltage under linear and nonlinear load perturbations. The total harmonic distortion (THD) is also reduced to 0.20% and 1.14% for linear and non-linear loads, respectively.

Original Approach Toward Three-Phase Indirect Matrix Converters Through Hybrid PWM Modulation and DSP Implementation

Power electronic matrix converters are converters carrying out just one solitary transitional stage. AC-AC conversion automatism in matrix converters is attained through the exploitation of bidirectional controllable power switches associated with a structural matrix. The indirect matrix converter is an alternating preference to the direct matrix converter embodied by AC-DC converter and DC-AC inverter. In this paper, an assemblage of Pulse Width Modulation categories is used to control the dual stages of IMC. AC-DC converter is modulated through the well-known space vector algorithm, while DC-AC inverter is modulated through a novel algorithmic conception referred to as the digital scalar algorithm. Comparative analysis between the conventional DSVPWM modulation and the novel proposed modulation technique is escorted demonstrating that the latter is facilely comprehended and simply put into real-time practice. This paper comes forward with digital signal processor real-time enforcement, conceived for indirect matrix converter. Uniting both original approaches into one topological system entrained a significant decrease of 38% in real-time computation assesses. Throughout the paper, it is well proven that the proposed solution results in high-quality input/output waveforms, and averts from servicing supplementary devices that trigger silicon devices' gates. Numerous experimental enquires within the delivered research reveal advantageous aspects of the contemporary approach from overall simplicity to entire effectiveness.

DC-AC Inverter with Tap Changing Transformer

In this paper a new single phase seven and eleven level inverter based on a tap changer transformer is developed to generates seven and eleven non-equal voltage levels from two DC sources. The model of inverter thus presented does not suffer from voltage balancing issues. The DC sources are connected to the primary side of the tap changer transformer with the help of a microcontroller circuit (Arduino UNO), with several semiconductor switches offering sequential modality. At the secondary side of transformer, the output voltage is generative, and Proteus/Software manipulation is performed. This technique reduces the Total Harmonic Distortion (THD) of the output voltage significantly.

Decoupled Control of Three Phase Grid Connected Solar PV System

A reliable grid connected Photovoltaic (PV) system require effective control schemes for efficient use of solar energy. This paper presents a three-phase grid tied PV system with decoupled real and reactive power control to achieve desired power factor with Maximum Power Point Tracking (MPPT) controller to get maximum solar energy. The synchronous reference frame (dq) control along with decoupling concept is used to control the DC-AC inverter output, while the Phase Locked Loop (PLL) synchronization technique is used to monitor and synchronize the voltage and current at the grid side. The DC-DC converter with Incremental Conductance (InC) based MPPT model is also designed in this paper due to better accuracy compared to Perturb & Observe (P&O) algorithm. The simulation is performed in MATLAB/SIMULINK and a 31.5 kW PV system is modelled to get 30 kW power with the help of MPPT at Standard Test Conditions (STC). Any power factor value between 0.85 lagging to 0.9 leading can be obtained by changingreference q current in this inverter control strategy. The simulation results show that the change of reactive powerdoes not affecttheactive power values of the system, which verifies the effectiveness of the decoupled control strategy of the inverter.

Performance evaluation of grid-connected power conversion systems integrated with real-time battery monitoring in a battery energy storage system

This paper aims at investigating power conversion system (PCS) and lithium-ion (Li-ion) cells employed in a grid-connected battery energy storage system (BESS). For PCS, the work evaluates the efficiency performance among the four topologies commonly used in power grid using PSIM. The output power, DC link voltage, semiconductor devices’ configurations and pulse width modulation method are the four parameters which are set constant in order to obtain a fair comparison among the topologies. From the simulations, it was observed that direct DC–AC inverters (98.3–99.1%) yield better efficiency performance compared to conventional DC–AC inverters (98.1–99.0%). Besides, a Li-ion cell is monitored during its charge and discharge cycles where state of charge is estimated via the combination of Coulomb counting and open-circuit voltage method. State of health is predicted by measuring the battery capacity in an experimental setup which aims to predict battery remaining useful life, hence improving the reliability of a BESS.

Performance Assessment of Modular Multilevel Half Bridge Inverter for High Power PV Application

This paper presents three-level Modular Multilevel Half Bridge Inverter to achieve lower total harmonic distortion and improved efficiency. Compared to conventional inverter, multilevel inverters provide output voltage of high quality and current waveform while using the low switching frequency. The use of multilevel inverters reduces the switching losses, size of semiconductor switches and the number of harmonic filters as compared to the traditional DC-AC inverters. This paper investigates different classification of multilevel inverters suitable for photovoltaic applications of high power based on efficiency and THD of the output line voltage and current waveform. Multilevel Inverter topologies are simulated as the same environment using MATLAB/Simulink.

Impacts of Wide Band Gap Power Electronics on Photovoltaic System Design

The emergence of electrical conversion technologies utilizing silicon carbide and gallium nitride switches and diodes will enable the development of a whole new class of efficient, lightweight, and reliable power electronics based on wide band gap semiconductors for photovoltaic (PV) systems. This article presents the results of a study to model the value proposition of these devices when they are used in dc–ac inverters, medium voltage dc–dc converters, as well as solid state breakers and transformers. The conclusions illustrate the beneficial impact on energy generation, operation and maintenance, plant architecture simplification, and associated reduction in capital cost and levelized cost of electricity that these new solid state devices will enable for the future PV system developer.

A Gallium Nitride (GaN)-Based Single-Inductor Multiple-Output (SIMO) Inverter With Multi-Frequency AC Outputs

In this paper, a gallium nitride (GaN)-based single-inductor multiple-output (SIMO) dc–ac inverter, which generates multiple frequencies at the ac outputs, is introduced. The proposed time-multiplexed switching sequences enable the SIMO inverter to simultaneously generate sinusoidal-like outputs with different frequencies. In the absence of a parasitic body diode in the GaN transistor and with correct bias voltage, the proposed inverter requires no additional blocking diodes and/or cascaded power switches while still ensuring unidirectional flow of the inductor current for proper circuit operation. Compared with its silicon counterpart, this GaN-based inverter achieves a simplified circuit structure, reduced component count, small form factor, increased power density, and high efficiency. A practical application of this inverter is to act as a single wireless power transmitter which concurrently drives multiple transmitter coils at different frequencies for multi-standard wireless power transfer. A hardware prototype of a single-inductor three-output inverter producing three distinct resonant frequencies, namely, 100, 200, and 300 kHz, is constructed. The effectiveness of the proposed switching sequences and control method for this inverter is experimentally verified. No cross regulation is observed across the three individual ac outputs.

Novel DC–AC inverter based on phase‐shift shoot‐through controlled dual‐active‐bridge and high‐frequency pulse DC link

Bidirectional isolated DC–AC inverters are widely used in industrial applications, such as grid-connected uninterruptible power supply, renewable power energy system, electric vehicles and so on. In order to improve the conversion efficiency, realising soft switching will become the essential technology in the research of DC–AC inverters. Based on the commonly used two-stage isolated inverter, this study proposed a novel DC–AC inverter that combines dual-active-bridge (DAB) converter, switched capacitor and full-bridge inverter. Utilising the strategy of phase-shift shoot-through control, DAB will generate a high-frequency pulse DC link cooperated with switched capacitor. As a result, during the shoot-through period, when the DC link is in zero-voltage-stage, the full-bridge inverter could realise zero-voltage switching (ZVS) through discrete pulse modulation. Principles, characteristics and implementations of the proposed inverter and its control strategy are analysed in detail. A further analysis on the operation modes and ZVS constraint of DAB's secondary bridge and switched capacitor is completed. A 250 VDC to 150 VAC (peak value) 1.13 kW simulation and experimental prototype is presented to validate the ZVS of full-bridge inverter and the analysis of DAB converter and switched capacitor.

Predictive neural network based adaptive controller for grid-connected PV systems supplying pulse-load

This paper presents an adaptive controller for grid-tie DC-AC inverter in grid-connected Photovoltaic (PV) power system supplying a pulse AC load. The proposed controller oversees regulating the dc-bus voltage, managing the injected power to the grid, and minimizing the injected harmonics. The controller parameters are optimized and adaptively tuned using predictive neural network controller (PNNC). The PNNC predicts the control parameters by tracking the mean square errors of grid currents and dc-bus voltage and eliminating these errors in a very short finite time. The proposed controller was implemented in MATLAB environment and tested under different dynamic conditions, including step variation of irradiance level and the application of pulse loads. The controller performance was investigated in comparison with a base-case, in which the controller parameters are arbitrarily tuned. The results showed that the proposed adaptive controller offers faster dynamic response with less settling time and maximum overshoot for both current and voltage variables. Furthermore, the injected harmonics to the grid were significantly reduced showing a 1.97% total harmonic distortion (THD) in comparison with the conventional controller with 5.06% THD, which makes the PV system compatible with the requirements in the IEEE 519 international standard for harmonic control in electrical power systems.