A stochastic mixed integer linear optimization scheduling model minimizing system operation costs and treating load and wind power production as stochastic inputs is presented. The schedules are updated in a rolling manner as more up-to-date information becomes available. This is a fundamental change relative to day-ahead unit commitment approaches. The need for reserves dependent on forecast horizon and share of wind power has been estimated with a statistical model combining load and wind power forecast errors with scenarios of forced outages. The model is used to study operational impacts of future high wind penetrations for the island of Ireland. Results show that at least 6000 MW of wind (34% of energy demand) can be integrated into the island of Ireland without significant curtailment and reliability problems.

This paper presents a comprehensive review on the unified power quality conditioner (UPQC) to enhance the electric power quality at distribution levels. This is intended to present a broad overview on the different possible UPQC system configurations for single-phase (two-wire) and three-phase (three-wire and four-wire) networks, different compensation approaches, and recent developments in the field. It is noticed that several researchers have used different names for the UPQC based on the unique function, task, application, or topology under consideration. Therefore, an acronymic list is developed and presented to highlight the distinguishing feature offered by a particular UPQC. In all 12 acronyms are listed, namely, UPQC-D, UPQC-DG, UPQC-I, UPQC-L, UPQC-MC, UPQC-MD, UPQC-ML, UPQC-P, UPQC-Q, UPQC-R, UPQC-S, and UPQC-VA(min). More than 150 papers on the topic are rigorously studied and meticulously classified to form these acronyms and are discussed in the paper.

Thermal design of the converter can be optimized if the power losses are precisely known. The device’s conduction and switching characteristics are very sensitive to the temperatures, so the influence of junction temperatures must be taken into consideration when calculating the power losses. In this paper, a practical loss calculation method is derived based on the analysis of the conduction and switching principles of the neutral point clamping three-level converters. Using thermal resistance equivalent circuit, the devices junction temperatures are acquired. An 1MVA NPC converter is tested in inverter and rectifier operating modes, and the infrared thermal imager is used to measure the devices temperatures. The error rates between measured and calculated temperatures are within 5% range and thus the validity of the loss calculation method is verified.

Thermal design of the converter can be optimized if the power losses are precisely known. The device’s conduction and switching characteristics are very sensitive to the temperatures, so the influence of junction temperatures must be taken into consideration when calculating the power losses. In this paper, a practical loss calculation method is derived based on the analysis of the conduction and switching principles of the neutral point clamping three-level converters. Using thermal resistance equivalent circuit, the devices junction temperatures are acquired. An 1MVA NPC converter is tested in inverter and rectifier operating modes, and the infrared thermal imager is used to measure the devices temperatures. The error rates between measured and calculated temperatures are within 5% range and thus the validity of the loss calculation method is verified.

The result of the research on the loss of the modular multilevel converter (MMC) based valve for HVDC power transmission is seldom reported. Due the distinctive feature of MMC topology, the methods to calculation the loss of traditional loss calculation methods for thyristors and insulate gate bipolar transistors (IGBT) cannot be directly applied to MMC valve. Combining with the switching characteristic of the distinctive semiconductor devices of the sub-module of MMC valve, the physical process of switching on/off the sub-module of MMC valve is analyzed; considering the topological structure of the converter and equivalent-area modulation algorithm, the relation among the loss of MMC valve and its valve current, and modulation algorithm voltage under typical operating condition is derived. The research result is available for reference to the loss reduction design for MMC-HVDC transmission systems.

The result of the research on the loss of the modular multilevel converter (MMC) based valve for HVDC power transmission is seldom reported. Due the distinctive feature of MMC topology, the methods to calculation the loss of traditional loss calculation methods for thyristors and insulate gate bipolar transistors (IGBT) cannot be directly applied to MMC valve. Combining with the switching characteristic of the distinctive semiconductor devices of the sub-module of MMC valve, the physical process of switching on/off the sub-module of MMC valve is analyzed; considering the topological structure of the converter and equivalent-area modulation algorithm, the relation among the loss of MMC valve and its valve current, and modulation algorithm voltage under typical operating condition is derived. The research result is available for reference to the loss reduction design for MMC-HVDC transmission systems.

在兆瓦级直驱风电系统中，发电机定子电压等级通常采用较低的690?V，而定子电流等级则很高，给全功率变流器的设计和制造造成了的困难，特别是效率问题比较突出。提出一种基于直驱多相永磁同步发电机和三电平混合式变流器的技术方案，用以替代传统的三相发电机和两电平变流器并联方案，具有更好的谐波性能和效率。讨论不同变流器拓扑在方案中的应用及其参数设计方法，并在谐波、效率和成本方面进行了比较。

在兆瓦级直驱风电系统中，发电机定子电压等级通常采用较低的690?V，而定子电流等级则很高，给全功率变流器的设计和制造造成了的困难，特别是效率问题比较突出。提出一种基于直驱多相永磁同步发电机和三电平混合式变流器的技术方案，用以替代传统的三相发电机和两电平变流器并联方案，具有更好的谐波性能和效率。讨论不同变流器拓扑在方案中的应用及其参数设计方法，并在谐波、效率和成本方面进行了比较。

For variable-speed drives, the interaction of the machine and the converter is becoming increasingly important, especially for high-speed applications, mainly due to the effect of the converter modulation on the machine losses. The allocation of the losses to different components of the drive system needs to be known in order to choose the ideal machine and modulation combination. In this paper, individual models are introduced for calculating the rotor, copper, and core losses of the machine as well as the inverter losses, taking the modulation type into account. These models are developed by considering two typical high-speed permanent-magnet synchronous motor topologies (slotted and slotless machines) driven by pulse-amplitude modulation (PAM) and pulsewidth modulation (PWM) converters. The models are applied to two off-the-shelf machines and a converter operating with either PAM or PWM. The test bench used to experimentally verify the models is also described, and the model results are compared to the measurements. The results show that PAM produces a higher overall efficiency for the high-speed machines considered in this paper. However, PWM can be used to move the losses from the rotor to the converter at the expense of decreasing the overall drive efficiency. The possible benefits of these results are discussed.

模块化多电平换流器（MMC）的子模块（SM）冗余配置问题是MMC工程应用急需解决的难点之一。文中对MMC及其SM结构进行了阐述，分析了SM和MMC的可靠性，提出了一种有效的MMC的SM冗余配置计算方法，并提供了SM的2个工程冗余参考值。当MMC的SM冗余配置数量在这2个冗余参考值之间时，冗余SM的增加能够使MMC的可靠性更快增加，在此基础上定义了冗余和可靠性指标，用其可以衡量不同MMC的冗余SM的可靠性效率。最后，通过工程实例计算证明了所提出的MMC的SM冗余配置计算方法和所定义指标的合理性和有效性。

模块化多电平换流器（MMC）的子模块（SM）冗余配置问题是MMC工程应用急需解决的难点之一。文中对MMC及其SM结构进行了阐述，分析了SM和MMC的可靠性，提出了一种有效的MMC的SM冗余配置计算方法，并提供了SM的2个工程冗余参考值。当MMC的SM冗余配置数量在这2个冗余参考值之间时，冗余SM的增加能够使MMC的可靠性更快增加，在此基础上定义了冗余和可靠性指标，用其可以衡量不同MMC的冗余SM的可靠性效率。最后，通过工程实例计算证明了所提出的MMC的SM冗余配置计算方法和所定义指标的合理性和有效性。

风电变流器的可靠运行是风能转换系统中的重要关注对象。然而现有文献评估器件结温对变流器可靠性的影响时，却没有重视结温波动的影响，以致往往高估了风电变流器的可靠性。该文基于永磁同步风力发电机工作的恶劣环境，分别从切入运行风速、额定风速、切除停机风速、开关频率及功率因数的变化，造成变流器中器件结温幅值及其波动差别的角度出发，利用Coffin-Manson器件可靠性评估模型，评估网侧变流器可靠性的差异。以1 MW风机结合实际风速数据为例进行分析论证，结果验证了理论分析的正确性。统计数据结果表明，额定风速及开关频率的变化对变流器可靠性的影响比较大。为了实现变流器的高可靠运行，风机宜在低风速切入运行，尽可能高的风速切除停机。

风电变流器的可靠运行是风能转换系统中的重要关注对象。然而现有文献评估器件结温对变流器可靠性的影响时，却没有重视结温波动的影响，以致往往高估了风电变流器的可靠性。该文基于永磁同步风力发电机工作的恶劣环境，分别从切入运行风速、额定风速、切除停机风速、开关频率及功率因数的变化，造成变流器中器件结温幅值及其波动差别的角度出发，利用Coffin-Manson器件可靠性评估模型，评估网侧变流器可靠性的差异。以1 MW风机结合实际风速数据为例进行分析论证，结果验证了理论分析的正确性。统计数据结果表明，额定风速及开关频率的变化对变流器可靠性的影响比较大。为了实现变流器的高可靠运行，风机宜在低风速切入运行，尽可能高的风速切除停机。

Oriented to a converter under vector control, a model of its fault diagnosis with the three-phase current signals as characteristic parameters is established. The output current signals, from which noise is further reduced with wavelet analysis theory, are also used in the statistic calculation for characteristic fault vector with FFT transform. The characteristic fault vector acts as input to neutral network. Through the training of neutral network, the network parameters can be decided and the analysis of fault data will be finished, which lead to a successful fault diagnosis. The fault diagnosis model, as well as its application into converters with SVPWM scheme, is proven to be workable with experiments.

Oriented to a converter under vector control, a model of its fault diagnosis with the three-phase current signals as characteristic parameters is established. The output current signals, from which noise is further reduced with wavelet analysis theory, are also used in the statistic calculation for characteristic fault vector with FFT transform. The characteristic fault vector acts as input to neutral network. Through the training of neutral network, the network parameters can be decided and the analysis of fault data will be finished, which lead to a successful fault diagnosis. The fault diagnosis model, as well as its application into converters with SVPWM scheme, is proven to be workable with experiments.

This paper presents a three-phase unified power-quality conditioner based on current source converters (CSC-UPQC), including the design guidelines of the key components, an appropriate control scheme, and a selection procedure of the dc current level. Particularly, the ridethrough capability criterion is used to define a minimum dc current level so that the CSC-UPQC achieves the same characteristics as a UPQC based on voltage-source converters in terms of voltage disturbance compensation in the point of common coupling (PCC) and load power factor compensation. A 1.17 MVA load fed from a 3.3 kV system is used to show the proposed design procedure, and a laboratory prototype is implemented to show the system compensating sags and swells using low switching frequency in the CSC and maintaining a unitary displacement power factor in the PCC.

This study proposes control and design methods for a current source united power-quality conditioner (CS-UPQC). Unipolar modulation and parameter design methods are proposed for the series CS converter. The proposed modulation method doubles the equivalent switching frequency, which makes it possible to reduce the filter size and improve the control dynamics. Modified repetitive control schemes are presented for the voltage and current compensation strategies, which provide large open-loop control gains at the integral multiple of the fundamental frequency and guarantee good harmonics compensation performance. A fault current limiting scheme is also presented, which limits the fault current effectively by utilising the large DC link inductor of the CS-UPQC. Simulation results in Matlab/Simulink are presented to clarify the theory and feasibility of the proposed approaches.

This paper presents an innovative approach to formulate a customer-oriented demand response (DR) program in the electricity market using the analytic hierarchy process (AHP). AHP could represent the mutual importance degrees of load reduction criteria from the various viewpoints of load-holders. Thus, the proposed DR program (DRP) could provide the reasonable decision-support process for load-holders, because the participation or nonparticipation is determined by the incentive payments corresponding to the specific load reduction conditions. The proposed DRP has the objective to maintain the system reliability at the emergency period, and it is designed as an incentive-based program (IBP) considering the real-time and by-directional operation. The modified IEEE 24-bus system for the case study is used to demonstrate the usefulness and applicability of the proposed approach, and the load profiles with the proposed DRP and the required incentive payments are obtained. The results show not only the enhancement to the system reliability but also the economic benefits within Pareto-improvement.

Multilevel converter has been found widely application in high power drive system. In this paper, the development of the multilevel converter is reviewed, and the relationship between different topologies are analyzed, and then the rules which should be obeyed are summarized when the different topologies are deduced from the generalized topology. Based on this, two novel topologies are presented, and the operating concept and control algorithm are studied. Simulation results show the feasibility of the proposed topologies.

Multilevel converter has been found widely application in high power drive system. In this paper, the development of the multilevel converter is reviewed, and the relationship between different topologies are analyzed, and then the rules which should be obeyed are summarized when the different topologies are deduced from the generalized topology. Based on this, two novel topologies are presented, and the operating concept and control algorithm are studied. Simulation results show the feasibility of the proposed topologies.