Bus energy consumption for multilevel signals

A comprehensive analysis of energy consumption for voltage-mode multilevel signals on a nanometer-technology bus is presented. A transition-dependent model is used which allows simplified calculation of the energy consumption. The accuracy of the approach is demonstrated using circuit simulations of three different electrical models of the bus, namely, lumped-C, distributed-RC, and distributed-RLC networks. We also verify that bus energy consumption is independent of driver resistance, as predicted by the model. Finally, we present a comparative analysis of power consumption for multilevel and binary buses

An Energy-Efficient Reconfigurable Mobile Memory Interface for Computing Systems

The critical need for higher power efficiency and bandwidth transceiver design has significantly increased as mobile devices, such as smart phones, laptops, tablets, and ultra-portable personal digital assistants continue to be constructed using heterogeneous intellectual properties such as central processing units (CPUs), graphics processing units (GPUs), digital signal processors, dynamic random-access memories (DRAMs), sensors, and graphics/image processing units and to have enhanced graphic computing and video processing capabilities. However, the current mobile interface technologies which support CPU to memory communication (e.g. baseband-only signaling) have critical limitations, particularly super-linear energy consumption, limited bandwidth, and non-reconfigurable data access. As a consequence, there is a critical need to improve both energy efficiency and bandwidth for future mobile devices.;The primary goal of this study is to design an energy-efficient reconfigurable mobile memory interface for mobile computing systems in order to dramatically enhance the circuit and system bandwidth and power efficiency. The proposed energy efficient mobile memory interface which utilizes an advanced base-band (BB) signaling and a RF-band signaling is capable of simultaneous bi-directional communication and reconfigurable data access. It also increases power efficiency and bandwidth between mobile CPUs and memory subsystems on a single-ended shared transmission line. Moreover, due to multiple data communication on a single-ended shared transmission line, the number of transmission lines between mobile CPU and memories is considerably reduced, resulting in significant technological innovations, (e.g. more compact devices and low cost packaging to mobile communication interface) and establishing the principles and feasibility of technologies for future mobile system applications. The operation and performance of the proposed transceiver are analyzed and its circuit implementation is discussed in details. A chip prototype of the transceiver was implemented in a 65nm CMOS process technology. In the measurement, the transceiver exhibits higher aggregate data throughput and better energy efficiency compared to prior works

GaN-Based Modular Multilevel Converter for Low-Voltage Grid Enables High Efficiency

Gallium Nitride (GaN) semiconductors with low inductance packages enable low switching losses and high efficiency. In this paper we present a compact arm PCB design with low loop inductance, allowing for fast and efficient switching. The PCB includes four full-bridge cells for a 7 kW Modular Multilevel Converter (MMC) for low-voltage grid applications

Review on Multi Level Inverter Topologies and Control Strategies for Solar Power Conversion

Nowadays solar power has become an alternate method of power generation for standalone systems for both urban and rural electrification. The Power Electronics converters used for the power conversion should provide quality AC output to have near sinusoidal voltage. The inverter topology and the PWM technique of the inverter play a vital role in providing quality output. This paper reviews recent contribution to establish the current status and development of the technology to provide reader with an insightful review of multilevel inverters and its control strategy. A brief overview of Multi Level Inverters (MLI) topology and advantages of Cascaded H-Bridge Multi Level Inverter (CHBMLI) for solar power conversion is presented and the various control strategies for CHBMLI are discussed with view point of quality output.  Among the different PWM techniques discussed, the Elliptical Multi Carrier PWM (EMC PWM) control strategy is the new modulation technique which successfully improves the DC bus utilization without over-modulation and without adding third harmonic to fundamental frequency. Also, the technique is successful in reducing the %THD at the output voltage. The control strategy is simple even with increased   level of output voltage, which is not possible in SVPWM technique.  Hence, the EMC PWM technique is having better performance when compared to Multi Carrier PWM (MCPWM) technique, Space Vector PWM (SVPWM) technique and Third Harmonic Injection PWM (THIPWM) technique.&nbsp

An Efficiency-Focused Design of Direct-DC Loads in Buildings

Despite the recent interest in direct current (DC) power distribution in buildings, the market for DC-ready loads remains small. The existing DC loads in various products or research test beds are not always designed to efficiently leverage the benefits of DC. This work addresses a pressing need for a study into the development of efficient DC loads. In particular, it focuses on documenting and demonstrating how to best leverage a DC input to eliminate or improve conversion stages in a load’s power converter. This work identifies how typical building loads can benefit from DC input, including bath fans, refrigerators, task lights, and zone lighting. It then details the development of several prototypes that demonstrate efficiency savings with DC. The most efficient direct-DC loads are explicitly designed for DC from the ground up, rather than from an AC modification

Comparative Analysis of Medium Voltage AC and DC Network Infrastructure Models

An increasing amount of consumer devices and end-use applications of electricity at the low voltage level that require a direct current (DC) power source have continued to advance in modern day society. At the same time the existing alternating current (AC) infrastructure that has served so well over the past century is beginning to show its age and vulnerability, leading to increased outages and reduced reliability. Also, the amount of high voltage direct current (HVDC) transmission system installations continue to increase around the world because of their proven superiority to high voltage alternating current (HVAC) in certain scenarios. However, with the widespread development and maturation in recent years of low voltage DC devices and systems, as well as large scale HVDC systems, no DC-based infrastructure or delivery system exists to efficiently connect the two together. Such an infrastructure would be developed through a medium voltage DC (MVDC) architecture. In order to properly analyze the benefits of a MVDC infrastructure for power distribution networks, a comparison between MVDC and MVAC architectures is necessary to identify advantages and disadvantages of both approaches. Investigating an architecture that would supply DC power to loads that is not much different in function to the existing AC grid system used today may bring with it increased efficiencies, therefore leading to economic operational and reliability benefits. To the author's knowledge, this thesis provides the first system scale comparative analysis of this nature comparing MVAC and MVDC. The preliminary design for such a system to supply DC power was created in this thesis using the PSCAD software package. The system analyzed utilizes a medium voltage DC bus rated at 20kV with a set of interconnected loads and generation. The DC system, while complicated with its wide array of power electronic converters, grants the ability to control power flow into the system from the different generation sources and to the loads. While the infrastructure design created is an initial step for a larger system, it lays the foundation for the future development of a DC distribution system for real world applications

Power Interface Design and System Stability Analysis for 400 V DC-Powered Data Centers

The demands of high performance cloud computation and internet services have increased in recent decades. These demands have driven the expansion of existing data centers and the construction of new data centers. The high costs of data center downtime are pushing designers to provide high reliability power supplies. Thus, there are significant research questions and challenges to design efficient and environmentally friendly data centers with address increasing energy prices and distributed energy developments. This dissertation work aims to study and investigate the suitable technologies of power interface and system level configuration for high efficiency and reliable data centers. A 400 V DC-powered data center integrated with solar power and hybrid energy storage is proposed to reduce the power loss and cable cost in data centers. A cascaded totem-pole bridgeless PFC converter to convert grid ac voltage to the 400 V dc voltage is proposed in this work. Three main control strategies are developed for the power converters. First, a model predictive control is developed for the cascaded totem-pole bridgeless PFC converter. This control provides stable transient performance and high power efficiency. Second, a power loss model based dual-phase-shift control is applied for the efficiency improvement of dual-active bridge converter. Third, an optimized maximum power point tracking (MPPT) control for solar power and a hybrid energy storage unit (HESU) control are given in this research work. The HESU consists of battery and ultracapacitor packs. The ultracapacitor can improve the battery lifetime and reduce any transients affecting grid side operation. The large signal model of a typical solar power integrated datacenter is built to analyze the system stability with various conditions. The MATLAB/Simulink™-based simulations are used to identify the stable region of the data center power supply. This can help to analyze the sensitivity of the circuit parameters, which include the cable inductance, resistance, and dc bus capacitance. This work analyzes the system dynamic response under different operating conditions to determine the stability of the dc bus voltage. The system stability under different percentages of solar power and hybrid energy storage integrated in the data center are also investigated

Power Interface Design and System Stability Analysis for 400 V DC-Powered Data Centers

The demands of high performance cloud computation and internet services have increased in recent decades. These demands have driven the expansion of existing data centers and the construction of new data centers. The high costs of data center downtime are pushing designers to provide high reliability power supplies. Thus, there are significant research questions and challenges to design efficient and environmentally friendly data centers with address increasing energy prices and distributed energy developments. This dissertation work aims to study and investigate the suitable technologies of power interface and system level configuration for high efficiency and reliable data centers. A 400 V DC-powered data center integrated with solar power and hybrid energy storage is proposed to reduce the power loss and cable cost in data centers. A cascaded totem-pole bridgeless PFC converter to convert grid ac voltage to the 400 V dc voltage is proposed in this work. Three main control strategies are developed for the power converters. First, a model predictive control is developed for the cascaded totem-pole bridgeless PFC converter. This control provides stable transient performance and high power efficiency. Second, a power loss model based dual-phase-shift control is applied for the efficiency improvement of dual-active bridge converter. Third, an optimized maximum power point tracking (MPPT) control for solar power and a hybrid energy storage unit (HESU) control are given in this research work. The HESU consists of battery and ultracapacitor packs. The ultracapacitor can improve the battery lifetime and reduce any transients affecting grid side operation. The large signal model of a typical solar power integrated datacenter is built to analyze the system stability with various conditions. The MATLAB/Simulink™-based simulations are used to identify the stable region of the data center power supply. This can help to analyze the sensitivity of the circuit parameters, which include the cable inductance, resistance, and dc bus capacitance. This work analyzes the system dynamic response under different operating conditions to determine the stability of the dc bus voltage. The system stability under different percentages of solar power and hybrid energy storage integrated in the data center are also investigated

Implementation of control schemes on a DC-AC terminal based on a HVDC-MMC

Los sistemas de transmisión de energía eléctrica a alta tensión en corriente directa o High Voltage Direct Current (HVDC) se han convertido en una solución atractiva para la integración de fuentes de energía renovables cómo las granjas eólicas que se encuentran alejadas de los centros de consumo.Tradicionalmente esta energía es transmitida mediante enlaces de corriente alterna (ac) lo que acarrea costos técnicos y económicos muy elevados. Los sistemas HVDC reducen las pérdidas que están asociadas a los efectos capacitivos de las líneas de transmisión ya que no dependen de la frecuencia y la distancia a la cual se transmite la energía por lo tanto no existe la necesidad de sistemas de compensación, utilizan un espacio más reducido para la ubicación de torres y las pérdidas de energía por conducción se reducen considerablemente. Los sistemas HVDC en su estructura topológica cuentan con estaciones convertidoras que realizan el proceso de conversión de energía ac-dc y dc-ac respectivamente, estas estaciones convertidoras se basan en la electrónica de potencia cuya configuración permite realizar la conversión de la energía y ser transmitida a largas distancias. Los sistemas de control requeridos por las estaciones convertidoras son de alta complejidad y no es una tarea sencilla diseñarlos debido a que el número de variables a regular es bastante alto, cómo las corrientes circulantes por los brazos, corrientes de salida, tensión en los capacitores entre otras. El objetivo principal de este proyecto es diseñar una técnica de control adecuada para un terminal HVDC basado en Modular Multilevel Converter (MMC), que garantice la estabilidad del sistema frente a pequeñas perturbaciones en las principales variables eléctricas, cómo por ejemplo cuando se presentan desbalances en la tensión y corriente de la red eléctrica, desbalance de tensión en los capacitores, reducción de las corrientes circulantes y el balance de energía en el terminal MMC. En el proyecto se realizará el modelado de un terminal MMC teniendo en cuenta el comportamiento dinámico del sistema, también se desarrollarán simulaciones del modelo en MATLAB Simulink para realizar la validación del modelo y diseñar las diferentes técnicas de control requeridas para cada tipo de variable.High voltage direct current or High Voltage Direct Current (HVDC) electric power transmission systems have become an attractive solution for the integration of renewable energy sources such as wind farms that are far from consumption centers. Traditionally, this energy is transmitted through alternating current (ac) links, which entails very high technical and economic costs. HVDC systems reduce the losses that are associated with the capacitive effects of the transmission lines since they do not depend on the frequency and the distance at which the energy is transmitted, therefore there is no need for compensation systems, they use a space smaller for the location of towers and energy losses by conduction are considerably reduced. HVDC systems in their topological structure have converter stations that carry out the AC-DC and DC-AC energy conversion process respectively, these converter stations are based on power electronics whose configuration allows energy to be converted and transmitted. a long distance. The control systems required by the converter stations are highly complex and it is not an easy task to design them because the number of variables to regulate is quite high, such as the circulating currents through the arms, output currents, voltage in the capacitors between others. The main objective of this project is to design a suitable control technique for an HVDC terminal based on the Modular Multilevel Converter (MMC), which guarantees the stability of the system against small disturbances in the main electrical variables, such as when there are imbalances in the voltage and current of the electrical network, voltage imbalance in the capacitors, reduction of circulating currents and the energy balance in the MMC terminal. In the project, the modeling of an MMC terminal will be carried out taking into account the dynamic behavior of the system, simulations of the model will also be developed in MATLAB Simulink to carry out the validation of the model and design the different control techniques required for each type of variable. The design will be implemented in a digital signal processor or Digital Signal Processing (DSP) to be validated in a prototype of the proposed system.MaestríaMagíster en Ingeniería EléctricaContents pág. 1 Introduction 2 Objectives 3 2.1 General Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2 Specific Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3 Literature Review 5 3.1 High Voltage Direct Current (HVDC) . . . . . . . . . . . . . . . . . . . 5 3.1.1 Advantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1.2 Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2 Most essential projects of HVDC systems . . . . . . . . . . . . . . . . . 8 3.2.1 ABB implementations [1] . . . . . . . . . . . . . . . . . . . . . . 8 3.2.2 Siemens Implementation [2] . . . . . . . . . . . . . . . . . . . . 8 3.3 HVDC Topologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.3.1 Bipolar Set-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.3.2 Homopolar Set-Up . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.3.3 Back to Back Set-Up . . . . . . . . . . . . . . . . . . . . . . . . 11 3.3.4 Pole to Pole Set-Up . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.4 Power Electronics Converters . . . . . . . . . . . . . . . . . . . . . . . 12 3.5 Line Commutated Converter (LCC) . . . . . . . . . . . . . . . . . . . . 12 3.5.1 LCC Components . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.6 Voltage Source Converter (VSC) . . . . . . . . . . . . . . . . . . . . . . 15 3.6.1 VSC Components . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4 Modular Multilevel Converter 19 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.2 Submodule Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.3 Operating Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.3.1 Currents Relation . . . . . . . . . . . . . . . . . . . . . . . . . . 22 4.3.2 Circulating Current . . . . . . . . . . . . . . . . . . . . . . . . . 23 4.4 System Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 4.4.1 MMC Averaged Dynamic Model . . . . . . . . . . . . . . . . . 24 4.4.2 Dynamic Performance of the MMC . . . . . . . . . . . . . . . . 26 4.4.3 Selection of the Mean Sum Capacitor Voltages . . . . . . . . . . 27 4.4.4 Averaging Principle . . . . . . . . . . . . . . . . . . . . . . . . . 28 4.5 Design Considerations of the MMC . . . . . . . . . . . . . . . . . . . . 31 4.5.1 Design of The Submodule Capacitance CSM . . . . . . . . . . . 31 4.5.2 Arm Inductance Design . . . . . . . . . . . . . . . . . . . . . . 35 4.6 Modulation Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 4.6.1 Carrier Disposition PWM . . . . . . . . . . . . . . . . . . . . . 37 4.6.2 Carrier Phase Shifted PWM . . . . . . . . . . . . . . . . . . . . 38 5 Control Schemes Applied to an MMC Terminal 41 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 5.2 Proportional Integral Control (PI) . . . . . . . . . . . . . . . . . . . . . 41 5.2.1 Active and Reactive Power Control . . . . . . . . . . . . . . . . 43 5.2.2 Internal Current Control . . . . . . . . . . . . . . . . . . . . . . 44 5.2.3 Average Voltage Control . . . . . . . . . . . . . . . . . . . . . . 46 5.2.4 Single Voltage Control . . . . . . . . . . . . . . . . . . . . . . . 48 5.2.5 Reference Signal . . . . . . . . . . . . . . . . . . . . . . . . . . 48 5.3 Proportional Integral Resonant Control (PIR) . . . . . . . . . . . . . . 49 5.3.1 Time Delays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 5.3.2 Output Current Control . . . . . . . . . . . . . . . . . . . . . . 52 5.3.3 Circulating Current Control . . . . . . . . . . . . . . . . . . . . 56 5.3.4 Reference Signal . . . . . . . . . . . . . . . . . . . . . . . . . . 59 5.3.5 Hybrid Voltage Control . . . . . . . . . . . . . . . . . . . . . . . 60 5.3.6 Phase Locked Loop (PLL) . . . . . . . . . . . . . . . . . . . . . 63 5.4 Model Predictive Control (MPC) . . . . . . . . . . . . . . . . . . . . . 65 6 Simulation and Results 71 6.1 Output Voltage Response . . . . . . . . . . . . . . . . . . . . . . . . . 73 6.2 Output Current Response . . . . . . . . . . . . . . . . . . . . . . . . . 73 6.3 SM Capacitor Voltage Response . . . . . . . . . . . . . . . . . . . . . . 76 6.4 Circulating current Response . . . . . . . . . . . . . . . . . . . . . . . . 76 6.5 Small Signal Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 7 Experimental Results on a Scale Down MMC Prototype 83 7.1 Design Considerations for the Experimental MMC . . . . . . . . . . . . 85 7.1.1 MMC Submodule . . . . . . . . . . . . . . . . . . . . . . . . . . 85 7.2 Measurement Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 7.2.1 Current Transducer . . . . . . . . . . . . . . . . . . . . . . . . . 88 7.2.2 Voltage Transducer . . . . . . . . . . . . . . . . . . . . . . . . . 89 7.3 Control Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 7.4 Experimental Waveforms of the MMC . . . . . . . . . . . . . . . . . . 94 8 Conclusion and Remarks 99 References 10

System configuration, fault detection, location, isolation and restoration: a review on LVDC Microgrid protections

Low voltage direct current (LVDC) distribution has gained the significant interest of research due to the advancements in power conversion technologies. However, the use of converters has given rise to several technical issues regarding their protections and controls of such devices under faulty conditions. Post-fault behaviour of converter-fed LVDC system involves both active converter control and passive circuit transient of similar time scale, which makes the protection for LVDC distribution significantly different and more challenging than low voltage AC. These protection and operational issues have handicapped the practical applications of DC distribution. This paper presents state-of-the-art protection schemes developed for DC Microgrids. With a close look at practical limitations such as the dependency on modelling accuracy, requirement on communications and so forth, a comprehensive evaluation is carried out on those system approaches in terms of system configurations， fault detection, location, isolation and restoration