H-bridge Voltage Source Converter Research Articles

Fifth-Order Generalized Integrator for a Double-Stage Single-Phase Grid-Interfaced Photovoltaic Supply System

This paper presents a fifth-order generalized integrator (FOGI) as an orthogonal signal generator (OSG) to obtain a grid synchronization signal for a double-stage single-phase grid-interfaced photovoltaic supply system (GIPVSS). The proposed GIPVSS consists of a single-ended primary inductor converter (SEPIC) and a H-bridge voltage source converter (HBVSC) to transfer solar power to the grid system. The SEPIC controls maximum power delivery (MPD) from the Photovoltaic (PV) array and feeds that power to the grid via an HBVSC. In this study, all energy storage elements (inductors and capacitors) of SEPIC are considered with their effective series resistance (ESR). The dynamic modeling of SEPIC is obtained using a small signal analysis. The control of VSC allows harmonics’ mitigation and power factor improvements. A FOGI and a second-order adaptive filtering approach are used in controling VSC. The FOGI is used to obtain a grid synchronization signal from sensed grid voltage under disturbances. The second-order adaptive filtering approach is used to obtain an active load current component. The comparative analysis of FOGI with other reported algorithms is carried out under harmonics in sensed grid voltage. The effectiveness of the proposed system and its control is validated in a laboratory prototype using a Launch Pad TMS320F28379D digital signal processor (DSP).

High Gain Non Isolated DC Converter Employed in Single-Phase Grid-Tied Solar Photovoltaic Supply System

This article presents a high gain non isolated dc converter (HGNIDC) employed in single-phase grid-tied solar photovoltaic supply system (SPSS). In the proposed power optimized architecture based SPSS, each photovoltaic (PV) module is connected through HGNIDC to the common dc bus. The HGNIDC boosts up the low PV voltage as well as facilitates to harvest the maximum solar energy. For maximum power harvesting, fuzzy logic control (FLC) is used. The FLC enables high conversion efficiency at different weather conditions, fast dynamic response, reduced PV voltage oscillation, and does not require system specifications. For delivering the power to the ac grid from the common dc bus, an H-bridge voltage source converter (VSC) is used. The synchronization of VSC with the utility grid is carried out using an enhanced third-order generalized integrator (ETOGI). The ETOGI is able to extract fundamental grid voltage even under grid polluted conditions such as voltage sag, swell, higher dc-offsets, and harmonics. The performance of the proposed control approaches is validated using MATLAB/Simulink platform. The real time implementation is obtained using DSP board TMS320F28379D on the developed laboratory prototype.

Fundamental switched MW‐size multilevel converter for large‐scale solar PV plant

The requirement of high power (MW-size) power conditioning unit (PCU) has increased to minimise the plant balance of system cost due to a continuous increase in solar photovoltaic (PV) plant capacity. Traditionally used high-frequency pulse-width modulated two/three-level PCUs have high device switching losses and lower conversion efficiency and are not suitable for high power PCU application as high switching losses lead to high heat generation within the converter, which is very difficult to manage, and lower conversion efficiency leads to less revenue realisation. In the present work, fundamental switching selective harmonic elimination (SHE) modulated 11-level cascaded H-bridge voltage source converter is utilised for high power MW-size PCU application, as it has lower switching losses, higher conversion efficiency, and higher AC/DC voltage ratio. The PV plant configuration for a 40 MW (AC) capacity is developed in the MATLAB/Simulink environment and implemented in real-time simulator OPAL-RT to validate the design and control. Harmonics, steady-state, and dynamic performances are demonstrated at constant and changing solar irradiance levels. The converter conduction and switching losses and conversion efficiency at different loading conditions are presented. The converter control with the capacitor voltage balancing method for fundamental switched SHE is presented in detail.

Frequency Control of Offshore Wind Farm With Diode-Rectifier-based HVdc Connection

This paper presents a direct frequency control for offshore wind farms (OWFs) connected to the diode-rectifier-based (DR-based) high voltage direct current (HVDC) link. The frequency control is guaranteed through reactive power balance at the DR station without a capacitor bank placed at the DR station; while AC-voltage magnitude is clamped by the DR, provided that the HVDC link voltage is imposed by the onshore inverter. The control system is implemented by a voltage source converter (VSC) connected to the DR station. The VSC is also used to compensate harmonic currents, leading to passive AC-filters being also removed from the DR station. The proposed control system provides comparative advantages in terms of DR station volume and OWF installation cost with other centralized controls where besides a VSC, a high-voltage large capacitor bank is needed to be placed at the DR station. A new average-value model (AVM) of the DR system is derived to test the proposed frequency control, while the stability of the system is evaluated through a small-signal analysis. The proposed control system performance and the accuracy of the proposed AVM are verified through a detailed switching model of the system using operation of a cascaded H-bridge VSC.

A modified H-bridge voltage source converter with Fault Ride Capability

Power conversion systems are used in wind turbine to improve the quality of the generated power without harmonic distortion which is utilized for transmission through grid intended for variable wind speed. However due to the variations of wind leads to evolving of high voltage and low voltage which leads to inconsistency in feeding power to grid. Inorder to provide quality constant harmonic distortionless power to grid from wind turbine an efficient Magnet Synchronous Generator (MSG) connected to the Modified H-bridge series connected Voltage Source Convertor (MHSVSC) is framed out. This converter can draw the input voltage with low distortion and thereby provides the output voltage with low harmonic distortion by LCL filter. Also, to meet the inconsistency in voltage supply to the grid, a fault ride requirement capability based on the M-controller is provided for the dc-link voltage to manage the voltage drop and over voltage in the grid. Thus, the power, which is to be supplied to the grid, is done cost efficiently, consistently, reduced harmonic distortion and errors by utilizing the MHSVSC with Fault Ride Capability. The proposed methodology implemented in the MATLAB platform.

Design and performance analysis of generalised integrator-based controller for grid connected PV system

ABSTRACTThis article discusses the design and control of a single-phase grid-connected photovoltaic (PV) system. A 5-kW PV system is designed and integrated at the DC link of an H-bridge voltage source converter (VSC). The control of the VSC and switching logic is modelled using a generalised integrator (GI). The use of GI or its variants such as second-order GI have recently evolved for synchronisation and are being used as phase locked loop (PLL) circuits for grid integration. Design of PLL circuits and the use of transformations such as Park’s and Clarke’s are much easier in three-phase systems. But obtaining in-phase and quadrature components becomes an important and challenging issue in single-phase systems. This article addresses this issue and discusses an altogether different application of GI for the design of compensator based on the extraction of in-phase and quadrature components. GI is frequently used as a PLL; however, in this article, it is not used for synchronisation purposes. A new controller has been designed for a single-phase grid-connected PV system working as a single-phase active compensator. Extensive simulation results are shown for the working of integrated PV system under different atmospheric and operating conditions during daytime as well as night conditions. Experimental results showing the proposed control approach are presented and discussed for the hardware set-up developed in the laboratory.

Control of a multilevel frequency converter of a power-efficient electric drive

The paper is devoted to an investigation of the control algorithms of a high-voltage electric drive, the converting part of which is represented by the well-known multilevel Series Connected H-Bridge Voltage Source Converter (SCHB VSC) topology. The control algorithm in the framework of the method forming a Space Vector Pulse-Width Modulation (SPWM) is based on the known principle of choosing the three nearest vectors on the voltage diagram of the converter and calculation of the durations of their switching per modulation cycle. A technique that is the same for all converters of creation of a switching algorithm of power valves based on this principle was proposed. The technique uses the principle of a “centered” SPWM with minimization of switching component of the losses in IGBT inverters of the converter cells. The technique of uniform distribution of the switching load by the cells in the phases of the converter and the method of estimation of the power efficient of a high-voltage electric drive and comparison of SPWM based on the results of the computer modeling were proposed. Results of the integrated simulating and modeling test of a 17-level SCHB VSC composed of a high-voltage variable-frequency electric drive, showing a decrease in the total power losses in the power modules of the converter with a modulator of the developed structure of the space-vector PWM by 43–46% compared to the traditional algorithm of sinusoidal PWM, were obtained.

Sliding Mode Control of H Bridge Inverter Based DSTATCOM for Reactive Power Compensation

Reactive power compensation plays a key role in reducing distribution losses by improving power factor. A three phase three wire DSTATCOM consisting of a five level H-bridge Voltage Source Converter (VSC) is proposed for improving power factor in the distribution system at the Point of Common Coupling (PCC) when the load is continuously changing. The sliding mode control algorithm is used for reactive power compensation and achieve unity power factor. To accomplish this DSTATCOM is controlled to supply or absorb reactive power at PCC. Sinusoidal PWM method is used for obtaining the switching pulses for the cascaded H-bridge converter. The performance of the DSTATCOM controlled distribution system is validated by simulations using MATLAB/Simulink software and Power System block set toolboxes.

Analysis of the Internal Electrical Characteristics of Electronic Power Transformers

The modularized subunit of an electronic power transformer (EPT) is a series connection of two H-bridge voltage-source converters and a DC-DC converter with a high-frequency isolation transformer (HFIT). On the basis of cascading and paralleling the modularized subunits, EPT can be used in high-voltage and large-current applications in the power system. This paper discusses the steady state analysis of the modularized subunit of EPT. Theoretical analysis considers the influences of the two H-bridge voltage-source converters on the two sides of the DC-DC converter. We deduce the formulas of the theoretical calculation on the internal electrical characteristics of EPT (e.g., the voltages of the DC-bus capacitor and the primary side peak current of the HFIT). This paper provides guidance on the design and selection of EPT key elements (e.g., the DC-bus capacitors and HFIT). Experimental results are obtained from a single subunit of a laboratory model rated at 962 V, 15 kVA. All calculations, simulations, and experiments confirm the theoretical analysis of the subunit of EPT.

Comparison of 2.3-kV Medium-Voltage Multilevel Converters for Industrial Medium-Voltage Drives

This paper compares the expense of power semiconductors and passive components of a (2.3 kV, 2.4 MVA) two-level, three-level neutral-point-clamped, three-level flying-capacitor, four-level flying-capacitor, and five-level series-connected H-bridge voltage source converter on the basis of the state-of-the-art 6.5-, 3.3-, 2.5-, and 1.7-kV insulated gate bipolar transistors for industrial medium-voltage drives. The power semiconductor losses, the loss distribution, the installed switch power, the design of flying capacitors, and the components of an sine filter for retrofit applications are considered.