A control strategy to improve the stability of a large wind farm using a Static Reactive Power Compensator (STATCOM) and Dynamic Braking Resistor (DBR) is proposed and investigated. The STATCOM supplies the reactive power demand of the wind farm dynamically in order to maintain the network voltage. The DBR is controlled by Liapunov's stability criterion to absorb the active power of the wind farm during the network fault. The performance of the STATCOM and DBR, applied to a large wind farm (60MW), is studied in PSCAD/EMTDC. The simulation results show that effective control of the STATCOM and DBR together can enhance the stability of large wind farms.

Pulse generator for three-level converter is one of the important elements of the unified custom power conditioner (UCPC). In this paper, the successfully developed high quality pulse generator for three-level converter based on digital signal processing (TMS320C31) and space voltage vector pulse width modulation (PWM) is introduced. The basic theory of the three-level space voltage vector PWM and the relevant key problems are analyzed. The latter includes the principle of selecting and optimizing the pulse vector, the method of dividing the sector region, the method of controlling the neutral point voltage and the method of avoiding the narrow pulse, etc. The basic hardware structure and the method of its implementation as well as the experimental results are also presented.

Controlling technology is the key problem to realize compensation of power quality with a converter. A new method was proposed for the control of the three-phase tri-level voltage source shunt power quality conditioner. The mathematical model of the tri-level converter is addressed in detail. Reference current is calculated under synchronous d-q frame and advanced deadbeat control with voltage space pulse width modulation is used to trace the reference current. Results of computer simulation under MATLAB show good dynamic performance of the proposed scheme to compete the function of compensating harmonics, reactive current and imbalance

Parallel compensation unit is the basic one of universal custom power conditioner (UCPC). Study on it is useful to the research of UCPC because of the symmetry between the topology of parallel unit and serial one. Design of main circuit based on tri-level converter is presented to solve the problems of voltage sustainability, voltage harmonic and current harmonic. The hardware of control system based on dual-DSP is also presented to realize real-time calculation of control algorithm of dead-beat control and voltage space vector PWM. The principle and simulation result of control are presented, and the capability of parallel unit to compensate VAR, harmonic and unbalances is proved in this paper. The validity of the main circuit and control algorithm is proved by experimental result.

Based on the concept of customer power, the paper proposed a new device that is universal custom power conditioner (UCPC). The UCPC has series and shunt power converters with a battery energy storage system (BESS) for multi-function operation to compensate the voltage variation, flicker, reactive power, harmonics, imbalance, uninterruptible power supply, peak load power supply, active and reactive power control in transmission systems. The circuit and control topologies are addressed. A control structure based on dual DSP TMS320C32 and synchronous A/D sampling technology are discussed

In this paper, a unified approach to simplify the traditional distribution system compensators is proposed and investigated. Distribution System Unified Conditioner (DS-UniCon) is a unified device that combines all the individual compensators such as active filters, VAr compensators and uninterruptible power supply (UPS) in order to compensate harmonics, reactive power, asymmetry, voltage variation and power supply interruption by using state-of-art of power electronics. DS-UniCon offers a higher effective and economic means to improve power quality

In this article, the voltage unbalance between the inner and outer IGBT of the NPC (neutral-point-clamping) three level converter is studied in detail. The keys of this task are to use a method-“step-by-step method” and to understand the basic conception that the parasitic inductance is relevant to the dimension of the loop and the value in proportion. It can be seen that the very reasons for the unbalance are the unique structure of NPC three level circuit and the parasitic inductance in the snubber circuit. Finally the designing tips for testing the snubber circuit are given. The simulation and experimental results demonstrate the validity of the analysis

Based on the concept of switching function (SF) and space vector (SV), and introduced the coordinate transformation matrix on space reference frame in the unified theory of an AC motor, a new mathematical model of the three level PWM reversible rectifier was presented. The validity of the mathematical model was verified by simulation.

Based on the concept of switching function (SF) and space vector (SV), and cited the coordinate transformation matrix on space reference frame in the unified theory of an AC motor, a new mathematical model of the tri-level PWM reversible rectifier was presented in detail. The synchronous reference frame model was used to achieve the dq decoupling control of the converter. All control algorithms were implemented in dual digital-signal processors (DSP). The validity of the system model was verified by the results of computer-aided simulation and experiment

In this paper, a general powerful circuit of a universal custom power conditioner (UCPC), which is used to improve power reliability and quality applied to distribution networks, is presented in detail. The UCPC is based on series and shunt tri-level PWM converters with a battery energy storage system (BESS) for multi-function operations such as harmonic elimination, reactive power control, voltage sags compensation and uninterruptible power supply (UPS). The basic algorithm of system is deadbeat control with a repetitive compensation strategy based on the voltage space vector PWM method. Some simulation results are use to verify that UCPC can synthetically fulfill different compensation functions

本文提出空间矢量PWM脉宽调制方式应用于新型三电平高频整流器系统,可以优化开关矢量,降低开关频率,提高直流侧电压利用率,减小交流侧输入电流的谐波畸变;并充分考虑了例如GTO开关元件的最小脉宽限制,采用电压反馈补偿的方法来控制中点电位.最后通过基于MATLAB语言及SIMULINK仿真环境对三电平PWM高频整流器的系统仿真,证明了理论分析的正确性.

详细地阐述了死区累积效应这一非线性因素造成PWM高频整流器系统波形畸变的机理,着重分析了死区基波电压对系统输入侧线电流波形的负面影响,并提出相应的改进电压空间矢量PWM调制方式.数字仿真的结果验证了分析的正确性.

研究了一种新型高功率因数变流器,采用TL494对开关器件进行PWM控制,可实现输入电流波形近似正弦波,功率因数接近为1.在介绍电路工作原理基础上,重点对其输入电流进行了分析,给出了计算机仿真与实验结果.

In this paper, a novel voltage space vector (NVSV) method used for 3-phase pulse width modulation voltage source reversible rectifier (PWM VSR) is described in detail. Based on the conventional voltage space vector (CVSV) method and its geometry topology, the actual switching time has a very simple form. With the /spl alpha//spl beta/-coordinate transformation, the NVSV can be easily realized. Its effect is exactly the same as the CVSV method. Thus, the NVSV method can be simply implemented by using a common microprocessor. It has the attractive features such as short execution time and little memory size compared with the method. Furthermore, every phase of the converter can have its switching stopped for 120/spl deg/ in one period, so the switching loss of the power device can be minimized by about 33%. The proposed method is implemented by an 80c196KC and its performance has been proved by a 15 kW IGBT laboratory prototype.