浅谈给粉机变频调速

变频调速可靠性高,调速性能优越,随着变频器价格的下降,给粉机使用变频器调速已经成为可能。下面就结合车间三台锅炉24台给粉机的实际情况谈一下笔者对变频给粉机的认识。     

新型载波移相同步脉冲发生器的研究

提出一种新型载波移相同步脉冲发生器。该发生器基于工业以太网分布时钟,可以产生纳秒级的高精度同步脉冲信号,信号用来同步链式多电平逆变器所有阀体输出的PWM脉冲。该控制系统成功应用于10 k V/1 Mvar级静止同步补偿器（STATCOM）装置。     

基于负序电流注入的光伏并网逆变器孤岛检测方法

孤岛运行时光伏电源继续向负载供电,会给检修人员和用户设备带来安全隐患,快速有效地实现孤岛检测具有重要意义。提出了一种通过并网逆变器注入负序电流并检测公共连接点电压不平衡度的快速孤岛检测方法。通过合理投切负序电流注入降低了对电网的干扰,不受电网不对称故障的影响且无检测盲区。在光伏电源功率与负荷功率匹配、公共连接点电压和频率基本不发生偏移的情况下对该方法进行了仿真验证,结果表明即便在这种最不利于孤岛检测的情况下,该方法仍能快速准确地检测出孤岛运行状态。     

Prediction-based Deadbeat Control for Grid-connected Inverter with L-filter and LCL-filter

Abstract—In this article, an improved deadbeat control algorithm suitable for digital signal processor-based circuit implementation is proposed. The control algorithm allows the derivation of a nearly sine wave output current with a fixed switching frequency of a current-controlled voltage source inverter. Two low-pass output filters configurations are considered in this study: a simple inductance filter and an LCL-filter. By taking advantage of prior knowledge of the state variables’ shape, the improved deadbeat control algorithm is based on a simple prediction model to derive the expected duty cycle needed to switch on and off the power switches. The control study of the grid-connected inverter with L and LCL output filters has been considered using a co-simulation approach with (Powersim Inc., Rockville, Maryland, USA) and MATLAB software (The MathWorks, Natick, Massachusetts, USA). The obtained results show the improvement of both shape quality and tracking accuracy of the output current quantified by low ripple content and a nearly unity power factor.     

Seamless Transfer Control Strategy for Grid-Interactive Inverters

Abstract—Single-phase microgrids are widely used in residential houses. The energy storage system with grid-interactive inverters in these microgrids should operate in both grid-tied and standalone modes. In this article, proportional resonant controller for the single-phase grid-interactive inverter with LCL-filter is designed and implimented in the both operation modes. Also, a novel seamless transfer strategy based on hysteresis current control is proposed when off-grid transfer operation is needed. With the proposed method, the inverter is able to provide voltage support to the local critical loads during the whole transfer process when the grid fails. For the grid-tied transfer process, a phase difference eliminating method based on inverter frequency regulation is introduced in this article to eliminate the phase difference between the grid voltage and the inverter voltage when the grid recovers. Simulation and experiments are carried out and the results verify the effectiveness of the proposed control method.     

联网微型光伏逆变器分段混合控制方法研究

针对交错反激微型光伏逆变器在临界电流连续模式(BCM)控制下开关管频带宽、控制复杂和在电流断续模式(DCM)控制下变压器功率转换密度低、并网电流质量差等问题,提出了一种分段混合控制方法。该控制方法对微逆变器的工作周期进行了分段,使微逆变器在单个反激式的电流断续模式下和交错反激式的临界电流连续模式下交替工作。详细分析了分段混合控制下交错反激变换器产生正弦电流的原理,给出了具体实现方案的开关序列和波形。研究结果表明,分段混合控制方法作用下联网微逆变器可实现与电网电压同频、同相的并网电流输出,并提高微逆变器工作效率和功率转换量,该控制方法适合于微逆变器的各个功率等级。     

新型单相光伏并网逆变器共模电流抑制研究

针对现有非隔离单相光伏并网逆变器拓扑共模电流大、效率低等问题,提出一种新型非隔离单相光伏并网逆变器拓扑,该拓扑在单相全桥逆变器的基础上增加2个续流二极管,并将交流侧滤波电感移至逆变器下桥臂,使得开关周期内共模电压保持恒定,有效抑制了共模电流;同时高频开关管使用MOSFET,工频开关管使用IGBT,且避免引入额外的开关管,系统整体损耗降低.通过对3 kW系统的仿真和实验,验证了新型拓扑抑制共模电流的效果.     

考虑寄生电感的SiC MOSFET半桥电路串扰峰值预测方法

针对光伏并网逆变器中的串扰问题,提出一种考虑寄生电感影响的非开尔文封装SiC MOSFET串扰峰值预测算法。以TO-247-3封装SiC MOSFET构成的半桥电路为研究对象,首先分析各个阶段的串扰电压数学模型,并推导串扰电压的微分表达式;其次提出串扰峰值的预测算法,建立预测峰值所需参数的数学模型;最后搭建实验平台,验证理论的正确性和算法的有效性,为设计光伏并网逆变器的驱动和保护电路提供参考依据。     

一种改进的频率正反馈无功电流扰动孤岛检测研究

孤岛检测技术能保证逆变型光伏发电系统并网对电力系统安全运行和稳定工作。基于对传统无功电流扰动方法的分析,提出了一种改进的频率正反馈的无功电流扰动孤岛检测方法。通过周期性地施加无功扰动电流和扰动函数的正反馈作用,加大无功扰动量,使频率越限,从而实现防孤岛效应保护功能。通过Matlab/Simulink仿真软件搭建了仿真模型,实验结果表明,该方法对电能质量影响小,不向电网注入谐波,具有无检测盲区、检测速度快的优点。     

弱电网下并网逆变器锁相环优化方法

针对弱电网条件下并网逆变器锁相环精度易受电网电压畸变、频率偏移、三相电压不平衡以及直流电压偏置等工况影响的问题,本文提出一种适用于弱电网下并网逆变器的解耦双同步坐标系锁相环(DDSRF-PLL)优化方法。首先在建立DDSRF-PLL模型的基础上,从理论角度证明电网电压畸变和直流电压偏置是影响传统DDSRF-PLL锁相精度的关键因素;而后利用傅里叶变换具备抗谐波和抗直流偏置干扰的优点,提出基于滑动傅里叶变换(SFT)的频率自适应鉴相器,继而构建适用于并网逆变器的优化解耦双同步坐标系锁相环。在电网电压发生畸变时本文所提锁相环在20 ms内可以完成对电压相位跟踪,在电网电压存在直流偏置的情况下本文所提锁相环能在10 ms内快速跟踪电压相位,且相位超调量在1°以内。实验结果表明,本文所提锁相环在弱电网环境下能快速准确的提取电网电压的频率和相位信息,有助于并网逆变器在电网电压畸变、电网电压直流偏置和电网电压不平衡等复杂工况下降低输出电流谐波含量。