COMMON MODE VOLTAGE ELIMINATION IN THREE-PHASE FOUR-LEG INVERTERS UTILIZING PULSE DENSITY MODULATION

Common mode (CM) electromagnetic interference (EMI) is a phenomenon that negatively affects power electronics to include voltage source inverters. Typically, CM EMI reduction is achieved through passive measures such as CM chokes and passive filters. This thesis research explores removing the need for these passive devices in three-phase, four-leg grid-following inverters by eliminating CM EMI using pulse density modulation (PDM) in conjunction with model predictive control (MPC) and delta modulation. A physics-based model of the equipment under test (EUT), utilizing state-space modeling, was analyzed using computer simulations and a laboratory prototype, utilizing SiC switching devices, was designed to validate the model. The physics-based model of the proposed control system was converted to Verilog, a hardware description language (HDL) utilizing MATLAB HDL coder in order to control the laboratory prototype via a field-programmable gate array (FPGA). Simulated and experimental results demonstrate that both the unbalanced load requirements in MIL-STD-1399 and the conducted emission limits in MIL-STD-461G are met with the proposed controller, while the grid-following converter supplies a desired current to the load.Office of Naval Research, Arlington VA 22203-1995Outstanding ThesisLieutenant, United States NavyApproved for public release. Distribution is unlimited

Modular Multilevel Cascaded Flying Capacitor STATCOM for Balanced and Unbalanced Load Compensation

Voltage and current unbalance are major problems in distribution networks, particularly with the integration of distributed generation systems. One way of mitigating these issues is by injecting negative sequence current into the distribution network using a Static Synchronous Compensator (STATCOM) which normally also regulates the voltage and power factor. The benefits of modularity and scalability offered by Modular Multilevel Cascaded Converters (MMCC) make them suitable for STATCOM application. A number of different types of MMCC may be used, classified according to the sub-module circuit topology used. Their performance features and operational ranges for unbalanced load compensation are evaluated and quantified in this research. This thesis investigates the use of both single star and single delta configured five-level Flying Capacitor (FC) converter MMCC based STATCOMs for unbalanced load compensation. A detailed study is carried out to compare this type of sub-module with several other types namely: half bridge, 3-L H-bridge and 3-L FC half bridge, and reveals the one best suited to STATCOM operation. With the choice of 5-L FC H-bridge as the sub-module for STATCOM operation, a detailed investigation is also performed to decide which pulse width modulation technique is the best. This was based on the assessment of total harmonic distortion, power loss, sub-module switch utilization and natural balancing of inner flying capacitors. Two new modulation techniques of swapped-carrier PWM (SC-PWM) along with phase disposed and phase shifted PWM (PS-PWM) are analyzed under these four performance metrics. A novel contribution of this research is the development of a new space vector modulation technique using an overlapping hexagon technique. This space vector strategy offers benefits of eliminating control complexity and improving waveform quality, unlike the case of multilevel space vector technique. The simulation and experimental results show that this method provides superior performance and is applicable for other MMCC sub-modules. Another contribution is the analysis and quantification of operating ranges of both single star and delta MMCCs in rating the cluster dc-link voltage (star) and current (delta) for unbalanced load compensation. A novel method of extending the operating capabilities of both configurations uses a third harmonic injection method. An experimental investigation validates the operating range extension compared to the pure sinusoidal zero sequence voltage and current injection. Also, the superiority of the single delta configured MMCC for unbalanced loading compensation is validated

Comparative Analysis of Multilevel Converters for Medium-Voltage Applications

The electric energy demand has been steadily growing during the last century, and all forecasts indicate that it will keep growing in the following years. Within this frame, and due to all the problems that this demand increase generate in the environment, it is necessary improving the current techniques of electric energy conversion and transmission in order to increase the whole system efficiency. On the other hand, it is also necessary increasing the renewable energy resources exploitation through more efficient generation systems. According to these lines, the power electronics systems that have been installed in the last decades allowed to obtain better efficiency from the renewable natural resources like the wind or the solar power. These systems have also notably improved the quality of the power supplied, reducing the losses through what are known as power quality applications. Power converters are currently essential in any power electronics system. Within them, the multilevel converters specially suppose a breakthrough compared with the classical two level converters, as they allow obtaining voltage and current signals with lower harmonic content, what means fewer losses in high power medium voltage applications. In this Thesis a comparative study of some multilevel converter topologies normally used in high power medium voltage applications is done. The objective is analyzing in detail each topology and comparing it with the rest following different criteria, with the aim to know the advantages and drawbacks of each one and to realize which one is more suitable for each application

A Hybrid Method of Performing Electric Power System Fault Ride-Through Evaluations on Medium Voltage Multi-Megawatt Devices

This dissertation explores the design and analysis of a Hybrid Method of performing electrical power system fault ride-through evaluations on multi-megawatt, medium voltage power conversion equipment. Fault ride-through evaluations on such equipment are needed in order to verify and validate full scale designs prior to being implemented in the field. Ultimately, these evaluations will help in reducing the deployment risks associated with bringing new technologies into the marketplace. This is especially true for renewable energy and utility scale energy storage systems, where a significant amount of attention in recent years has focused on their ever increasing role in power system security and stability. The Hybrid Method couples two existing technologies together - a reactive voltage divider network and a power electronic variable voltage source - in order to overcome the inherent limitation of both methods, namely the short circuit duty required for implementation. This work provides the background of this limitation with respect to the existing technologies and demonstrates that the Hybrid Method can minimize the fault duty required for fault evaluations. The physical system, control objectives, and operation cycle of the Hybrid Method are analyzed with respect to the overall objective of reducing the fault duty of the system. A vector controller is designed to incorporate the time variant nature of the Hybrid Method operation cycle, limit the fault current seen by the power electronic variable voltage source, and provide regulation of the voltage at the point of common coupling with the device being evaluated. In order to verify the operation of both the Hybrid Method physical system and vector controller, a controller hardware-in-the-loop experiment is created in order to simulate the physical system in real-time against the prototype implementation of the vector controller. The physical system is simulated in a Real Time Digital Simulator and is controlled with the Hybrid Method vector controller implemented on a National Instruments FPGA. In order to evaluate the complete performance of the Hybrid Method, both a synchronous generator and a doubly-fed induction generator are modeled as the device under test in the simulations of the physical system. Finally, the results of the controller hardware-in-the-loop experiments are presented which demonstrate that the Hybrid Method is a viable solution to performing fault ride-through evaluations on multi-megawatt, medium voltage power conversion equipment

Direct current control for grid connected multilevel inverters

Control schemes for inverters of different topologies and various numbers of voltage levels are of great interest for many standard as well as special applications. This thesis describes a novel, robust and high-dynamic direct current control scheme for multilevel voltage source inverters. lt is highly independent from load parameters and universally applicable. The new control method is examined and validated with real measurements . The aim of the thesis is to establish and prove a new concept of a direct current control algorithm for multilevel inverter topologies for grid connected systems. This application is characterized by unknown grid conditions including failure modes and other distortions, complex inverter topologies and a large variety and complexity of current control algorithms for multilevel inverters. Therefore the complexity of the system needs to be reduced. Additionally , the advantages of multilevel inverters and the dynamic performance and robustness of direct current control techniques shall be combined. Starting from a detailed literature study on inverter topologies and direct as well as indirect current control methods, the thesis includes three chapters containing relevant contributions to the achievement of the objectives. A method reducing the control-complexity of multilevel converters has been developed. The simplification method is based on a transformation that converts any three-phase voltage (or current) into a non-orthogonal coordinate system. This choice minimizes the complexity and effort to determine the location of those discrete voltage space vectors directly surrounding the required reference voltage vector. A further improvement is achieved by scaling all coordinates to integer values. This is advantageous for further calculations on microprocessors or FPGA based control systems. The main contribution of this thesis is a new direct current control method minimizing the disadvantages of existing direct methods. At the same time advantages of other control algorithms shall be applied. The new method is based on a simple mathematical equation, that is, the solution of a scalar product, to always select the one inverter output voltage vector best reducing the actual current error. This results in the designation "Scalar Hysteresis Control - SHC". An advanced seeking algorithm ensures robust current control capability even in case of unknown, unsymmetrical or changing loads, in case of rapid set-point changes or in cases of unknown phase voltages . The new method therefore shows excellent properties in terms of simplicity , robustness, dynamics and independence from the inverter level count and the hardware topology . The properties of the control method are verified by means of simulations and real measurements on two-, three- and five-level inverters over the complete voltage operating range. Finally, all contributions are collected together and assessed with regard to the objectives. From the proposed control method new opportunities for future work, further developments and extensions are evolving for continuing scientific researchEls sistemes de control d'inversors de diferents topologies i diferent varis nivells de tensió són de gran interès per moltes aplicacions estàndard i també per aplicacions especials. Aquesta tesi investiga sobre un mètode de control directe de corrent per convertidors multinivell en font de tensió que es mostra robust i presenta una elevada dinàmica en el control de corrent. El mètode és molt robust davant de canvies als paràmetres de la càrrega i aplicable a qualsevol tipus de convertidor. En aquesta tesi s'analitza el mètode i es valida mitjançant resultats experimentals. L'objectiu d'aquesta tesi és establir i demostrar un nou de mètode i algorisme de control directe de corrent aplicat especialment a inversors connectats a la xarxa. L'aplicació es caracteritza per la desconeixença dels paràmetres de la xarxa, incloent diferents modes de falla i distorsions en la seva tensió i una varietat de tipologies de convertidors multinivell. El mètode de control busca simplificar l'algorisme i que pugui ser aplicat en aquest entorn de forma robusta, de forma que es pugui estendre l'ús dels convertidors multinivell sense afegir més complexitat als algorismes de control i modulació. La tesi aborda el problema iniciant amb un anàlisi de la literatura existent en aquest tipus de mètodes de control directe i indirecte del corrent i els convertidors multinivell, per continuar amb l'anàlisi del mètode proposat i la seva demostració mitjançant resultats de simulacions i experimentals. El mètode de simplificació està basat en una transformació que transforma qualsevol sistema trifàsic a un sistema de coordenades no-ortogonal. Escollir aquest sistema de coordenades redueix la complexitat i l'esforç per determinar la ubicació d'aquells vectors espacials que directament envolten el vector de referencia. A més, totes les coordenades s'escalen a valors enters, que permet la programació de l'algorisme en sistemes de control basats en microprocessadors o FPGAs. La principal contribució d'aquesta tesi és un nou mètode de control de corrent que intenta minimitzar els desavantatges dels mètodes indirectes existents a l'actualitat, al mateix moment que s'intenta incorporar els avantatges dels mètodes indirectes. El mètode proposat es basa en una equació matemàtica simple, la solució d'un producte escalar, per trobar el vector de tensió espacial que minimitza l'error de corrent, en el que s'anomena "Scalar Hysteresis Control" o SHC. L'algorisme assegura un control robust del corrent sense la necessitat de conèixer la tensió de fase, o les càrregues, tant si són desequilibrades o canviants. També presenta una dinàmica molt elevada en cas de canvies en la referència. El nou mètode mostra unes propietats excel·lents en termes de simplicitat, robustesa, dinàmica i independència de la tipologia del convertidor i, en el cas de convertidors multinivell, del nombre de nivells. Les propietats del mètode de control són verificades mitjançant simulacions i resultats experimentals en convertidors de dos, tres i fins a cinc nivells de tensió en tot el rang d'operació, fins i tot en la zona de sobremodulació. A partir del mètode de control proposat, s'estan desenvolupant noves aplicacions i extensions, continuant també la contribució a la recerca científica

Direct current control for grid connected multilevel inverters

Control schemes for inverters of different topologies and various numbers of voltage levels are of great interest for many standard as well as special applications. This thesis describes a novel, robust and high-dynamic direct current control scheme for multilevel voltage source inverters. lt is highly independent from load parameters and universally applicable. The new control method is examined and validated with real measurements . The aim of the thesis is to establish and prove a new concept of a direct current control algorithm for multilevel inverter topologies for grid connected systems. This application is characterized by unknown grid conditions including failure modes and other distortions, complex inverter topologies and a large variety and complexity of current control algorithms for multilevel inverters. Therefore the complexity of the system needs to be reduced. Additionally , the advantages of multilevel inverters and the dynamic performance and robustness of direct current control techniques shall be combined. Starting from a detailed literature study on inverter topologies and direct as well as indirect current control methods, the thesis includes three chapters containing relevant contributions to the achievement of the objectives. A method reducing the control-complexity of multilevel converters has been developed. The simplification method is based on a transformation that converts any three-phase voltage (or current) into a non-orthogonal coordinate system. This choice minimizes the complexity and effort to determine the location of those discrete voltage space vectors directly surrounding the required reference voltage vector. A further improvement is achieved by scaling all coordinates to integer values. This is advantageous for further calculations on microprocessors or FPGA based control systems. The main contribution of this thesis is a new direct current control method minimizing the disadvantages of existing direct methods. At the same time advantages of other control algorithms shall be applied. The new method is based on a simple mathematical equation, that is, the solution of a scalar product, to always select the one inverter output voltage vector best reducing the actual current error. This results in the designation "Scalar Hysteresis Control - SHC". An advanced seeking algorithm ensures robust current control capability even in case of unknown, unsymmetrical or changing loads, in case of rapid set-point changes or in cases of unknown phase voltages . The new method therefore shows excellent properties in terms of simplicity , robustness, dynamics and independence from the inverter level count and the hardware topology . The properties of the control method are verified by means of simulations and real measurements on two-, three- and five-level inverters over the complete voltage operating range. Finally, all contributions are collected together and assessed with regard to the objectives. From the proposed control method new opportunities for future work, further developments and extensions are evolving for continuing scientific researchEls sistemes de control d'inversors de diferents topologies i diferent varis nivells de tensió són de gran interès per moltes aplicacions estàndard i també per aplicacions especials. Aquesta tesi investiga sobre un mètode de control directe de corrent per convertidors multinivell en font de tensió que es mostra robust i presenta una elevada dinàmica en el control de corrent. El mètode és molt robust davant de canvies als paràmetres de la càrrega i aplicable a qualsevol tipus de convertidor. En aquesta tesi s'analitza el mètode i es valida mitjançant resultats experimentals. L'objectiu d'aquesta tesi és establir i demostrar un nou de mètode i algorisme de control directe de corrent aplicat especialment a inversors connectats a la xarxa. L'aplicació es caracteritza per la desconeixença dels paràmetres de la xarxa, incloent diferents modes de falla i distorsions en la seva tensió i una varietat de tipologies de convertidors multinivell. El mètode de control busca simplificar l'algorisme i que pugui ser aplicat en aquest entorn de forma robusta, de forma que es pugui estendre l'ús dels convertidors multinivell sense afegir més complexitat als algorismes de control i modulació. La tesi aborda el problema iniciant amb un anàlisi de la literatura existent en aquest tipus de mètodes de control directe i indirecte del corrent i els convertidors multinivell, per continuar amb l'anàlisi del mètode proposat i la seva demostració mitjançant resultats de simulacions i experimentals. El mètode de simplificació està basat en una transformació que transforma qualsevol sistema trifàsic a un sistema de coordenades no-ortogonal. Escollir aquest sistema de coordenades redueix la complexitat i l'esforç per determinar la ubicació d'aquells vectors espacials que directament envolten el vector de referencia. A més, totes les coordenades s'escalen a valors enters, que permet la programació de l'algorisme en sistemes de control basats en microprocessadors o FPGAs. La principal contribució d'aquesta tesi és un nou mètode de control de corrent que intenta minimitzar els desavantatges dels mètodes indirectes existents a l'actualitat, al mateix moment que s'intenta incorporar els avantatges dels mètodes indirectes. El mètode proposat es basa en una equació matemàtica simple, la solució d'un producte escalar, per trobar el vector de tensió espacial que minimitza l'error de corrent, en el que s'anomena "Scalar Hysteresis Control" o SHC. L'algorisme assegura un control robust del corrent sense la necessitat de conèixer la tensió de fase, o les càrregues, tant si són desequilibrades o canviants. També presenta una dinàmica molt elevada en cas de canvies en la referència. El nou mètode mostra unes propietats excel·lents en termes de simplicitat, robustesa, dinàmica i independència de la tipologia del convertidor i, en el cas de convertidors multinivell, del nombre de nivells. Les propietats del mètode de control són verificades mitjançant simulacions i resultats experimentals en convertidors de dos, tres i fins a cinc nivells de tensió en tot el rang d'operació, fins i tot en la zona de sobremodulació. A partir del mètode de control proposat, s'estan desenvolupant noves aplicacions i extensions, continuant també la contribució a la recerca científica.Postprint (published version

Development of an active power filter based on wide-bandgap semiconductors

Pla de Doctorat Industrial, Generalitat de CatalynuaElectrical and electronic equipment needs sinusoidal currents and voltages to function properly. Equipment such as computers, household appliances, electric vehicle chargers, and LED lights can distort the grid and worsen grid quality. Distorted electrical grids can cause malfunctions, reduce service life, and decrease the performance of connected equipment. Industry commonly solves these problems using active power filters, which can minimise the harmonics of the grid, eliminate undesirable reactive power, and restore balance to unbalanced power grids. This thesis deals with the design and implementation of an active power filter based on wide-bandgap semiconductors, which have properties that are superior to classical silicon devices. An active power filter’s design must take advantage of these benefits to build converters that are smaller, more efficient, and consume fewer resources. However, wide-bandgap semiconductors also present design challenges. Because the most commonly used active power filters in the industry are based on two-level voltage source converters, the research for this doctoral thesis focuses on this converter topology. Moreover, its main objective is to contribute new modulation techniques that are specially designed to work with wide-bandgap semiconductors. The proposed modulations consider different aspects, such as the computational cost of the algorithms, converter losses, and the electromagnetic distortion generated. First, this thesis presents a hexagonal sigma-delta (H-S¿) modulation based on sigma-delta (S¿) modulation. The properties of this modulation are studied, and the technique is compared with other widely used modulations. The comparison considers efficiency, harmonic distortion, the electromagnetic compatibility of the converter, and the type of wideband semiconductor used. In addition, a fast algorithm is mathematically developed to simplify the presented modulation and reduce its computational cost. Secondly, this thesis presents a family of sigma-delta modulations specially designed to improve electromagnetic compatibility: the reduced common-mode voltage sigma-delta (RCMV-S¿) modulations. These modulations avoid using the vectors that generate the maximum common-mode voltage, which significantly reduces the generated electromagnetic distortion without affecting the performance of the converter and its harmonic distortion. Finally, the proposed modulations are applied in a wide-bandgap power converter working as an active filter. Thus, it is verified that the techniques presented in this thesis will obtain satisfactory results when implemented in commercial active power filters.Els equips elèctrics i electrònics necessiten corrents i tensions sinusoïdals per funcionar correctament. Existeixen equips com els ordinadors, els electrodomèstics, els carregadors de vehicle elèctric o les llums LED, que poden distorsionar la xarxa i empitjorar la qualitat d'aquesta. Les xarxes elèctriques distorsionades poden causar el mal funcionament dels equips que s'hi connecten, reduir la seva vida útil i també empitjorar la seva eficiència. A la industria és habitual utilitzar filtres actius per a solucionar aquests problemes. Els filtres actius permeten minimitzar els harmònics presents a la Δxarxa, eliminar la potència reactiva no desitjada i equilibrar xarxes elèctriques desequilibrades. Aquesta tesi tracta sobre el disseny i la implementació d'un filtre actiu basat en semiconductors de banda ampla. Aquests semiconductors presenten propietats superiors als clàssics dispositius de silici. El disseny d'un filtre actiu ha d'aprofitar aquests avantatges per a construir convertidors més petits, eficients i que consumeixin menys recursos. Tanmateix, els semiconductors de banda ampla també presenten problemes que el disseny ha de solucionar. Els filtres actius més utilitzats en la indústria són els basats en convertidors de font de tensió (voltatge source converters) amb dos nivells. La recerca d'aquesta tesi doctoral està focalitzada en aquesta topologia de convertidor, i el seu principal objectiu és l’aportació de noves tècniques de modulació especialment dissenyades per treballar amb semiconductors de banda ampla. Les modulacions proposades tenen en compte diferents aspectes: el cost computacional dels algoritmes, les pèrdues del convertidor i la distorsió electromagnètica generada. En primer lloc, es presenta una modulació sigma-delta hexagonal (H-__) que es basa en la modulació sigma-delta (ΣΔ). S'estudien les propietats d'aquesta modulació i la tècnica es compara amb altres modulacions àmpliament usades. La comparativa realitzada considera l’eficiència, la distorsió harmònica, la compatibilitat electromagnètica del convertidor i el tipus de semiconductor de banda ampla emprat. Addicionalment, es desenvolupa matemàticament un algoritme ràpid per simplificar la modulació presentada i reduir el seu cost computacional. En segon lloc, es presenta una família de modulacions sigma-delta especialment dissenyades per millorar la compatibilitat electromagnètica: les modulacions sigmadelta amb tensió en mode comú reduïda (RCMV-ΣΔ ). Aquestes modulacions eviten fer servir els vectors que generen la màxima tensió en mode comú. D'aquesta manera es redueix significativament la distorsió electromagnètica generada sense afectar de forma notable al rendiment del convertidor ni a la seva distorsió harmònica. Finalment, les modulacions proposades s'apliquen en un convertidor de potència, basat en semiconductors de banda ampla, que treballa com a filtre actiu. Això es verifica que les tècniques presentades en aquesta tesi poden ser implementades en filtres actius comercials obtenint resultats satisfactoris.Postprint (published version

Improved control for multilevel inverters in grid applications

Control systems for three-phase grid connected voltage source inverters (VSI) play an important role in energy transformation systems . They are expected to be stable, robust and accurate during steady state as well as different grid faults and disturbances like voltage sags or unbalanced conditions. Caused by increasingly rising grid standards and efficiency requirements the use of multilevel inverter systems in grid connected low voltage applications are getting more and more attention. Nevertheless, the use of these inverter types leads to increased complexity of the control system and the hardware components. This thesis presents an improved control scheme for multilevel inverters in grid applications. The system combines a robust and high-dynamic direct current control scheme called scalar hysteresisEn molts casos i, cada cop més, els sistemes de transformació energètica estan basats en convertidors en font de tensió connectats a la xarxa elèctrica trifàsica. Aquests convertidors necessiten de sistemes de control per controlar els fluxos energètics. Els sistemes de control han de ser estables, però també robustos i precisos durant el seu funcionament normal, però també en condicions on la xarxa pot presentar defectes, com curtcircuits, sots de tensió o desequilibris en la tensió. Degut a l'increment dels requeriments tècnics de connexió i d'eficiència energètica, els convertidors multinivell estan guanyant molt d'interès en aquest tipus d'aplicacions connectades a la xarxa tot i que el seu control i els seus components siguin més complexes. Aquesta tesi presenta un mètode de control per convertidors multinivell connectats a la xarxa elèctrica. El mètode combina la robustesa davant de canvis en el sistema així com una alta capacitat dinàmica per controlar el corrent injectat a la xarxa. El mètode presentat esta basat en l'anomenat Scalar Hysteresis Control (SHC) i incorpora un sistema feedforward que li permet seleccionar acuradament el punt de treball i seleccionar al millor estat de commutació en cada moment. La combinació del SHC amb el feedforward garanteix un comportament robust amb una alta dinàmica en totes les condicions de funcionament. El concepte bàsic del mètode feedforward proposat no usa sensors i està basat en detectar la tensió de l'inversor que inclou les components harmòniques. El mètode està basat en l'ús d'integradors generalitzats de segon ordre (second order generatlized integrators, SOGI) per tal de detectar les components harmòniques de la tensió de sortida de l'inversor. El sistema pot operar sense sensor de tensió, fins i tot en situacions de defecte de la tensió. Fins i tot, la informació extreta del SOGI es pot usar per altres llaços de control d'ordre superior com el control de la potencia usant les components simètriques. Per a determinar els millors estats de commutació de l'inversor amb el menor esforç s'usa en el mètode proposat en aquesta tesi un canvi de coordenades que usa valor enters. Aixo permet l'ús de relacions matemàtiques senzilles que es poden implementar fàcilment i que requereixen una menor potencia de càlcul. A més, el mètode és fàcilment generalitzable . En la tesi es presenten simulacions i resultats experimentals en convertidors multinivell de tres i cinc nivells per tal d'investigar i demostrar les funcionalitats del sistema de control proposat. Tant les simulacions com els resultats experimentals es realitzen en totes les condicions possibles de la xarxa elèctrica, estat estacionari, sots i distorsions harmòniquesPostprint (published version

Development of a grid emulator for network integration studies

Includes bibliographical references.The economic and environmental side effects of fossil fuels have forced governments and authorities to investigate sustainable solutions. Main interest is focused on environment friendly benefits, provided by renewable energy sources. The growth rate of these energy sources has increased remarkably in the past few years. Correspondingly the research and development in the field of power electronics has also increased, especially in medium voltage and high power grid connected systems. The grid behaviour of the renewable energy systems is heavily influenced by the control techniques of these systems. For further development of these control methods the most basic and conventional way is to simulate, test and prove the system performance on a down-scaled lab test bench. The objective of this thesis is to develop a laboratory test bench grid emulator for network integration studies. Design and performance are investigated by introducing several kinds of unbalanced voltage conditions to test the behavior of connected systems. Voltage dips and swells are implemented to test the system’s performance