EPE Association: EPE 2016 - DS1g: Power Electronics in Transmission and Distribution Systems

EPE 2016 - DS1g: Power Electronics in Transmission and Distribution Systems
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2016 ECCE Europe - Conference > EPE 2016 - Topic 06: Grids and Smart Grids > EPE 2016 - DS1g: Power Electronics in Transmission and Distribution Systems

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   A Novel Full Soft-switching Resonant Power Converter for Mid-feeder Voltage Regulation of Low Voltage Distribution Network
By Chao JI [View]
[Download]

Abstract: This paper presents a novel resonant based, high power density power electronics converter solutionfor mid-feeder voltage regulation of a low voltage (LV) distribution network. Owing to the use of highswitching frequency operation and a full soft-switching control strategy, the proposed converter iscapable of superimposing LV compensation into the feeder voltage, to achieve a significant systemeffect with a compact system volume and correspondingly smaller absolute power loss.

   A Novel Topology and Control Strategies for AC Solid State Power Controllers with Current-Limiting Function
By Li-gang RUAN [View]
[Download]

Abstract: This paper proposed a novel topology and control strategies for AC solid state power controllers (SSPC) in order to improve its capacity for starting large capacitive loads and enhance the security during short-circuit protection in high-power applications.

   A Survey on Configurations of Current-Limiting Circuit Breakers (CL-CB)
By Chunyang GU [View]
[Download]

Abstract: This paper presents a survey of topology configurations of current-limiting circuit breakers. Twelve different current-limiting topologies within four categories are detailed discussed and compared. It is concluded that active CL-CB may be a good choice for AC for its controllable reactive power capability to increase stability and multi-function protection.

   A Two-stage Efficient Model of Modular Multilevel Converter for Electromagnetic Transient Simulation
By Dewu SHU [View]
[Download]

Abstract: For modular multilevel converter, large number of switching elements introduce challenges to electromagnetic transient simulations. In order to improve the simulation efficiency, this paper proposes a two-stage modeling method of the MMC converter. The converter is represented as an extended state-space equation, which is more suitable for circulating current and control strategy studies. Then, the capacitor voltage of each submodule is updated on the second stage, which is based on each arm current adopting the backward Euler algorithm. Further, a fast simulation algorithm involving MMC converters is developed. It reduces the computational costs compared with the detailed model in PSCAD and provides accurate representation of MMC in both steady and transient states. Simulation results validate the accuracy and numerical performance of the proposed model with FSA algorithm.

   Analysis and Experimental Verification of Current Limiting Methods for Grid Converters under Unbalanced Load Conditions
By Hendrik JUST [View]
[Download]

Abstract: The impact of converter based generation systems on transmission and distribution grids is steadily increasing. Therefore, new control efforts regarding fault ride-through, fault current injection and voltage support are necessary. These grid services lead to high stress on the converter which has to be protected thoroughly in any operation mode. Especially conditions, where the grid voltages become unbalanced are critical for converter control. The tradeoff between grid requirements and converter protection requires robust control and limiting algorithms. In this paper, an advanced current limiting method is presented which minimizes the impact of the converter limits on the overall system support objective. The proposed strategy is verified in simulation and experiment. Fault ride-through requirements are considered and different power reference strategies like Average Active Power- (AARC), Balanced Positive Sequence- (BPSC) or Positive and Negative Sequence Control (PNSC) in combination with the limiting algorithm are investigated. A generalizable limiting concept for different applications like converter based generation units, FACTS or STATCOMs is achieved.

   Design of a Wide-Band Low-Voltage Grid Impedance Analyzer
By Sandro GUENTER [View]
[Download]

Abstract: In this paper the design and measurement results of a grid analysis and grid impedance measurementsystem are presented. The system is provided to measure the frequency dependent grid impedance indifferent PoCs to detect resonances and improve the power quality especially of grids with high amountof DERs. Moreover Active Filtering (AF) and reactive power feed-in are possible. It comprises alsomeasurement of the negative and zero sequence as well as of subharmonics. The design of the converteris discussed in detail, the chosen method of impedance measurement is explained briefly, calculationsfor the selection of the converter topology and the selection of power semiconductor devices are made.A special hysteresis current control for 3-level Active Neutral Point Clamped (ANPC) converters ispresented. Finally different measurement results are shown. These measurements of the grid impedanceinclude subsynchronous frequencies in the range of 0.1 Hz to 30 Hz and frequencies in the range of70 Hz to 10 kHz as well as measurements of the negative sequence and the zero sequence impedance ofdifferent low voltage grids.

   Efficient and Accurate Dynamic Average-Value Modeling of Current Source Modular Multilevel Converter
By Mukeshkumar BHESANIYA [View]
[Download]

Abstract: Current source modular multilevel converters (CSMMCs) in high-power applications can consist of largenumber of submodules. Simulations of such systems using full-size traditional detailed model in electromagnetic transient-type (EMT-type) simulation tools involve computational complexity and require verylarge computing time. This paper presents a computationally efficient and accurate average-value model(AVM) of CSMMC. In the proposed approach, the individual arm of CSMMC is represented by a controlledcurrent source and the dc-side of the converter is represented by the controlled voltage sources.The submodule inductances are represented by a single equivalent inductance on the dc-side. The harmoniccontents of the switching events are included using the modulation function in the arm level modelwhile the variations in the submodule inductor currents are ignored. To validate the proposed model, detailedsimulation studies of CSMMC based STATCOM is carried out with the proposed AVM and thetraditional model in PSCAD/EMTDC. The results of various studies, obtained from both the models,are compared. The close matching of the results proves the validity of the proposed AVM. Moreover,the comparison of simulation time of both the models clearly demonstrates very high computationalefficiency of the proposed AVM.

   Implementation and experimental set-up of a Modular Multilevel Converter in a Multi Terminal DC/AC transmission network
By Daniel SIEMASZKO [View]
[Download]

Abstract: In this paper the realization of a Multi Terminal DC pilot is presented. For the interaction with the medium voltage AC grid, a Modular Multilevel Converter has been designed for its features in low harmonic content, scalability, and flexibility. The Energy buffering of the converter will allow the converter to sustain either AC or DC grids. The operation of the converter is simulated together with the first experimental results of the implementation.

   Integration of AC and DC sources using Multi Source Fed Power Electronic Transformer (MSF-PET) for Modern Power Distribution System Applications
By Venkat Nag Someswar JAKKA [View]
[Download]

Abstract: Integration of power due to distributed renewable energy resources (DRERs) with the existing gridto supply electricity to both industrial and residential users is expected to have a significant impact onthe future power system. Power electronic transformer (PET) has emerged as one amongst the promisingtechnologies to achieve such requirement. In this paper, a multi-source fed power electronic transformer(MSF-PET) is proposed to integrate both ac and dc sources to supply the load power. The MSF-PETconsists of three stages: input, isolation, and output. The input stage consists of two power electronicconverters, viz. ac-dc and dc-dc converters, to integrate ac and dc sources, respectively. The outputs ofthese converters are connected to the inputs of two dual active bridge converters (DABs) of the isolationstage. The outputs of DABs are connected in parallel across the dc-link of the output stage inverter. Inthe proposed PET, the input and output ports are isolated from each other and interlinked by usingdifferent power electronic converters. Therefore, each port can be easily isolated by applying theappropriate gate signals to the associated converters. Further, the power can be supplied to the load fromboth sources simultaneously or independently. A detailed description of MSF-PET and its control arepresented. The theoretical analysis of MSF-PET is verified using PSCAD/EMTDC simulations. Thestudy results show that MSF-PET can be a promising topology for the modern distribution system tointegrate both the conventional ac grid and DRERs generating dc power.

   Novel Current-Limiting Strategy for Solid-State Circuit Breakers (SSCB) Without Additional Impedance
By Chunyang GU [View]
[Download]

Abstract: Current-limiting strategies for solid-state circuit breaker (SSCB) without adding impedance is introduced in this paper. With the current limitation of novel phase-shifting method, the advantages are simple hardware structure, relatively low cost, no heat generation, low weight and small size. Current-limiting capability is exploited with qualities of good control accuracy and robustness. The principle and theoretical analysis of phase-shifting current-limiting method are detailed introduced together with simulation/experimental verifications.

   Smart Distribution Transformer for Secondary Voltage Regulation and Load Modeling
By Josemar QUEVEDO [View]
[Download]

Abstract: The distribution networks have been subjected to increased demand for electricity and the inclusion of distributed generation (DG), which have affected the voltage regulation. In this work, it is proposed a smart distribution transformer, which encompasses an electronic on-load tap changer and a communication system. In addition to the automatic or remote voltage regulation, the system enables to identify the load model at the interface between primary and secondary distribution systems. These characteristics permit the enhancement of the power quality, along with the improvement of the distribution system operation, planning and revenue management. The main focus of this work is the load parameter identification, which is validated by a simulation tool and experimental results.

   Third-order Based Analytical Investigation of Nonlinear Interactions between Voltage Source Converters Interconnected to a Transmission Grid
By Tian TIAN [View]
[Download]

Abstract: Power electronics have been widely used in the transmission systems due to its capability to control the power flows as well as the voltages and currents. However, in the renewable energy transmission system, the weak-grid will make the VSCs work under nonlinear domain, where their behavior are quite different from the linear case. What's more, the interconnected VSCs are sometimes used to ensure more robust and flexible power transmission, leading to a multi-machine system, where the predominant nonlinear oscillations should be studied to suggest more information in designing the parameters of the system. This paper proposed a methodology to offer analytical results to predict nonlinear interaction for both oscillation amplitude and frequency-shift while avoiding numerical simulation of huge computational burden. Based on Normal Form theory, this methodology can be applied to large-scale power system that exhibits behavior of N coupled second-order oscillators. The nonlinear indices are then proposed to quantify the parameter impact on the nonlinear system dynamics.

   Using Variable DC Sources in order to Improve the Voltage Quality of a Multilevel STATCOM with Low Frequency Modulation
By Mohammadkazem BAKHSHIZADEH DOWLATABADI [View]
[Download]

Abstract: In this paper, a Selective Harmonic Elimination Pulse Width Modulation (SHE-PWM) method, which utilizes adjustable dc links, is presented for a Static Synchronous Compensator (STATCOM) based on Cascaded H-Bridge (CHB) multilevel converter. The proposed switching algorithm is able to fix the capacitors voltages at optimum and unequal values, while injecting the desired reactive power, in order to eliminate more low order harmonics. An indirect current control method is combined with a loss estimation block to control the dc link voltages that might have different losses. Moreover, by using unequal dc link voltages more levels at the output is achievable compared to the symmetrical multilevel converters that could be used in enhancing the power quality, while keeping the switching frequency near the fundamental (the maximum switching frequency can be kept below 150 Hz). The validity of the proposed method is verified by simulations in Matlab/Simulink environment.

EPE 2016 - DS1g: Power Electronics in Transmission and Distribution Systems
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2016 ECCE Europe - Conference > EPE 2016 - Topic 06: Grids and Smart Grids > EPE 2016 - DS1g: Power Electronics in Transmission and Distribution Systems
	[return to parent folder]

	A Novel Full Soft-switching Resonant Power Converter for Mid-feeder Voltage Regulation of Low Voltage Distribution Network By Chao JI	[View] [Download]
Abstract: This paper presents a novel resonant based, high power density power electronics converter solutionfor mid-feeder voltage regulation of a low voltage (LV) distribution network. Owing to the use of highswitching frequency operation and a full soft-switching control strategy, the proposed converter iscapable of superimposing LV compensation into the feeder voltage, to achieve a significant systemeffect with a compact system volume and correspondingly smaller absolute power loss.

	A Novel Topology and Control Strategies for AC Solid State Power Controllers with Current-Limiting Function By Li-gang RUAN	[View] [Download]
Abstract: This paper proposed a novel topology and control strategies for AC solid state power controllers (SSPC) in order to improve its capacity for starting large capacitive loads and enhance the security during short-circuit protection in high-power applications.

	A Survey on Configurations of Current-Limiting Circuit Breakers (CL-CB) By Chunyang GU	[View] [Download]
Abstract: This paper presents a survey of topology configurations of current-limiting circuit breakers. Twelve different current-limiting topologies within four categories are detailed discussed and compared. It is concluded that active CL-CB may be a good choice for AC for its controllable reactive power capability to increase stability and multi-function protection.

	A Two-stage Efficient Model of Modular Multilevel Converter for Electromagnetic Transient Simulation By Dewu SHU	[View] [Download]
Abstract: For modular multilevel converter, large number of switching elements introduce challenges to electromagnetic transient simulations. In order to improve the simulation efficiency, this paper proposes a two-stage modeling method of the MMC converter. The converter is represented as an extended state-space equation, which is more suitable for circulating current and control strategy studies. Then, the capacitor voltage of each submodule is updated on the second stage, which is based on each arm current adopting the backward Euler algorithm. Further, a fast simulation algorithm involving MMC converters is developed. It reduces the computational costs compared with the detailed model in PSCAD and provides accurate representation of MMC in both steady and transient states. Simulation results validate the accuracy and numerical performance of the proposed model with FSA algorithm.

	Analysis and Experimental Verification of Current Limiting Methods for Grid Converters under Unbalanced Load Conditions By Hendrik JUST	[View] [Download]
Abstract: The impact of converter based generation systems on transmission and distribution grids is steadily increasing. Therefore, new control efforts regarding fault ride-through, fault current injection and voltage support are necessary. These grid services lead to high stress on the converter which has to be protected thoroughly in any operation mode. Especially conditions, where the grid voltages become unbalanced are critical for converter control. The tradeoff between grid requirements and converter protection requires robust control and limiting algorithms. In this paper, an advanced current limiting method is presented which minimizes the impact of the converter limits on the overall system support objective. The proposed strategy is verified in simulation and experiment. Fault ride-through requirements are considered and different power reference strategies like Average Active Power- (AARC), Balanced Positive Sequence- (BPSC) or Positive and Negative Sequence Control (PNSC) in combination with the limiting algorithm are investigated. A generalizable limiting concept for different applications like converter based generation units, FACTS or STATCOMs is achieved.

	Design of a Wide-Band Low-Voltage Grid Impedance Analyzer By Sandro GUENTER	[View] [Download]
Abstract: In this paper the design and measurement results of a grid analysis and grid impedance measurementsystem are presented. The system is provided to measure the frequency dependent grid impedance indifferent PoCs to detect resonances and improve the power quality especially of grids with high amountof DERs. Moreover Active Filtering (AF) and reactive power feed-in are possible. It comprises alsomeasurement of the negative and zero sequence as well as of subharmonics. The design of the converteris discussed in detail, the chosen method of impedance measurement is explained briefly, calculationsfor the selection of the converter topology and the selection of power semiconductor devices are made.A special hysteresis current control for 3-level Active Neutral Point Clamped (ANPC) converters ispresented. Finally different measurement results are shown. These measurements of the grid impedanceinclude subsynchronous frequencies in the range of 0.1 Hz to 30 Hz and frequencies in the range of70 Hz to 10 kHz as well as measurements of the negative sequence and the zero sequence impedance ofdifferent low voltage grids.

	Efficient and Accurate Dynamic Average-Value Modeling of Current Source Modular Multilevel Converter By Mukeshkumar BHESANIYA	[View] [Download]
Abstract: Current source modular multilevel converters (CSMMCs) in high-power applications can consist of largenumber of submodules. Simulations of such systems using full-size traditional detailed model in electromagnetic transient-type (EMT-type) simulation tools involve computational complexity and require verylarge computing time. This paper presents a computationally efficient and accurate average-value model(AVM) of CSMMC. In the proposed approach, the individual arm of CSMMC is represented by a controlledcurrent source and the dc-side of the converter is represented by the controlled voltage sources.The submodule inductances are represented by a single equivalent inductance on the dc-side. The harmoniccontents of the switching events are included using the modulation function in the arm level modelwhile the variations in the submodule inductor currents are ignored. To validate the proposed model, detailedsimulation studies of CSMMC based STATCOM is carried out with the proposed AVM and thetraditional model in PSCAD/EMTDC. The results of various studies, obtained from both the models,are compared. The close matching of the results proves the validity of the proposed AVM. Moreover,the comparison of simulation time of both the models clearly demonstrates very high computationalefficiency of the proposed AVM.

	Implementation and experimental set-up of a Modular Multilevel Converter in a Multi Terminal DC/AC transmission network By Daniel SIEMASZKO	[View] [Download]
Abstract: In this paper the realization of a Multi Terminal DC pilot is presented. For the interaction with the medium voltage AC grid, a Modular Multilevel Converter has been designed for its features in low harmonic content, scalability, and flexibility. The Energy buffering of the converter will allow the converter to sustain either AC or DC grids. The operation of the converter is simulated together with the first experimental results of the implementation.

	Integration of AC and DC sources using Multi Source Fed Power Electronic Transformer (MSF-PET) for Modern Power Distribution System Applications By Venkat Nag Someswar JAKKA	[View] [Download]
Abstract: Integration of power due to distributed renewable energy resources (DRERs) with the existing gridto supply electricity to both industrial and residential users is expected to have a significant impact onthe future power system. Power electronic transformer (PET) has emerged as one amongst the promisingtechnologies to achieve such requirement. In this paper, a multi-source fed power electronic transformer(MSF-PET) is proposed to integrate both ac and dc sources to supply the load power. The MSF-PETconsists of three stages: input, isolation, and output. The input stage consists of two power electronicconverters, viz. ac-dc and dc-dc converters, to integrate ac and dc sources, respectively. The outputs ofthese converters are connected to the inputs of two dual active bridge converters (DABs) of the isolationstage. The outputs of DABs are connected in parallel across the dc-link of the output stage inverter. Inthe proposed PET, the input and output ports are isolated from each other and interlinked by usingdifferent power electronic converters. Therefore, each port can be easily isolated by applying theappropriate gate signals to the associated converters. Further, the power can be supplied to the load fromboth sources simultaneously or independently. A detailed description of MSF-PET and its control arepresented. The theoretical analysis of MSF-PET is verified using PSCAD/EMTDC simulations. Thestudy results show that MSF-PET can be a promising topology for the modern distribution system tointegrate both the conventional ac grid and DRERs generating dc power.

	Novel Current-Limiting Strategy for Solid-State Circuit Breakers (SSCB) Without Additional Impedance By Chunyang GU	[View] [Download]
Abstract: Current-limiting strategies for solid-state circuit breaker (SSCB) without adding impedance is introduced in this paper. With the current limitation of novel phase-shifting method, the advantages are simple hardware structure, relatively low cost, no heat generation, low weight and small size. Current-limiting capability is exploited with qualities of good control accuracy and robustness. The principle and theoretical analysis of phase-shifting current-limiting method are detailed introduced together with simulation/experimental verifications.

	Smart Distribution Transformer for Secondary Voltage Regulation and Load Modeling By Josemar QUEVEDO	[View] [Download]
Abstract: The distribution networks have been subjected to increased demand for electricity and the inclusion of distributed generation (DG), which have affected the voltage regulation. In this work, it is proposed a smart distribution transformer, which encompasses an electronic on-load tap changer and a communication system. In addition to the automatic or remote voltage regulation, the system enables to identify the load model at the interface between primary and secondary distribution systems. These characteristics permit the enhancement of the power quality, along with the improvement of the distribution system operation, planning and revenue management. The main focus of this work is the load parameter identification, which is validated by a simulation tool and experimental results.

	Third-order Based Analytical Investigation of Nonlinear Interactions between Voltage Source Converters Interconnected to a Transmission Grid By Tian TIAN	[View] [Download]
Abstract: Power electronics have been widely used in the transmission systems due to its capability to control the power flows as well as the voltages and currents. However, in the renewable energy transmission system, the weak-grid will make the VSCs work under nonlinear domain, where their behavior are quite different from the linear case. What's more, the interconnected VSCs are sometimes used to ensure more robust and flexible power transmission, leading to a multi-machine system, where the predominant nonlinear oscillations should be studied to suggest more information in designing the parameters of the system. This paper proposed a methodology to offer analytical results to predict nonlinear interaction for both oscillation amplitude and frequency-shift while avoiding numerical simulation of huge computational burden. Based on Normal Form theory, this methodology can be applied to large-scale power system that exhibits behavior of N coupled second-order oscillators. The nonlinear indices are then proposed to quantify the parameter impact on the nonlinear system dynamics.

	Using Variable DC Sources in order to Improve the Voltage Quality of a Multilevel STATCOM with Low Frequency Modulation By Mohammadkazem BAKHSHIZADEH DOWLATABADI	[View] [Download]
Abstract: In this paper, a Selective Harmonic Elimination Pulse Width Modulation (SHE-PWM) method, which utilizes adjustable dc links, is presented for a Static Synchronous Compensator (STATCOM) based on Cascaded H-Bridge (CHB) multilevel converter. The proposed switching algorithm is able to fix the capacitors voltages at optimum and unequal values, while injecting the desired reactive power, in order to eliminate more low order harmonics. An indirect current control method is combined with a loss estimation block to control the dc link voltages that might have different losses. Moreover, by using unequal dc link voltages more levels at the output is achievable compared to the symmetrical multilevel converters that could be used in enhancing the power quality, while keeping the switching frequency near the fundamental (the maximum switching frequency can be kept below 150 Hz). The validity of the proposed method is verified by simulations in Matlab/Simulink environment.