背靠背直流互联系统主动频率响应控制策略

相较于交流同步互联电网,低快速频率响应能力的直流异步互联电网频率稳定形势更为严峻。基于主动频率响应控制思想及其框架,提出大功率缺失下的背靠背直流互联系统主动频率响应控制策略。建立了背靠背直流互联系统网络结构模型及背靠背换流站控制系统模型,计及扰动后背靠背直流互联系统及频率响应动态特性,提出了一种基于模型预测算法的主动频率响应控制策略:频率下降阶段迅速调节非同步电网间直流传输功率;频率恢复阶段平抑和缓解频率振荡。算例分析表明:所提出的主动频率响应控制策略能够充分发挥背靠背直流互联系统调频能力,提高非同步电网间的频率响应支援能力。

基于减载控制的光伏电站主动频率响应方法

传统光伏发电系统通常运行在最大功率点,不对电网频率改变进行响应,不能为抑制电网频率变化提供有功功率,随着光伏渗透率的提升,对电网的安全稳定运行产生影响,因此光伏等新能源设备应具有响应系统频率变化的能力。文章采用减载控制,在不改变主电路结构、逆变器并网策略,不增设储能设备的情况下实现系统频率的响应。首先通过设置主从阵列得到当前最大功率运行点,实现减载控制;然后针对频率改变,通过设置频率-减载率对应关系,实现有功功率输出的改变,对系统进行有功支撑;最后通过半实物仿真平台进行仿真,验证了结果的有效性。

风电渗透率对接入电网频率调整特性的影响分析

部分地区超过20%的电网末端渗透率使得大功率风电注入电网时同步发电机调频压力极大,风电场参与电网一次调频已成必然,有必要对风电机组参与电网一次调频时的系统频率特性进行分析。在对双馈感应风力发电机（DFIG）超速减载的运行方式进行研究后,提出了频率响应的控制策略,并构建了相关的控制模块来实现DFIG风力机的调频功能,接着借助Matlab/Simulink仿真平台,在建立三机9节点模型的基础之上并入3台DFIG风力机构成的风电机组,模拟了风电场参与电网调频的情况,对不同调频渗透率下系统频率的变化规律进行了对比分析。该仿真提出了“调频渗透率”的概念,在同一模型不改变电网参数的情况下验证了不同调频渗透率时系统的频率特性,得出了调频渗透率的提高有助于促进系统频率稳定的结论。

基于新型无差拍电流控制的高速PMSM控制技术研究

通过对永磁同步电机驱动控制方法的研究,提出了一种新型的无差拍电流控制(dead beat current control,DBCC)策略。电机在高速或者需要高转矩响应时,为了减少转矩纹波,高带宽和高精度的控制电流环是必不可少的。无差拍电流控制是实现这些要求的首选之一。目前为止,国内外提出了多种无差拍电流控制方法。提出一种新型的考虑时间延时的DBCC方法,并且与传统的PI电流调节相比较,以进一步说明DBCC的优势。还提出了一种转子位置补偿的新算法,消除电机高速运行时的偏移误差。最后通过仿真和实验对该DBCC进行了验证。

A New Optimal Control System Design for Chemical Processes

Based on frequency response and convex optimization,a novel optimal control system was developed for chemical processes.The feedforward control is designed to improve the tracking performance of closed loop chemical systems.The parametric model is not required because the system directly utilizes the frequency response of the loop transfer function,which can be measured accurately.In particular,the extremal values of magnitude and phase can be solved according to constrained quadratic programming optimizer and convex optimization.Simulation examples show the effectiveness of the method.The design method is simple and easily adopted in chemical industry.

Vibration transmissibility characteristics of smart spring vibration isolation system

The objective of this work was to study the vibration transmissibility characteristics of the undamped and damped smart spring systems. The frequency response characteristics of them were analyzed by using the equivalent linearization technique, and the possible types of the system motion were distinguished by using the starting and ending frequencies. The influences of system parameters on the vibration transmissibility characteristics were discussed. The following conclusions may be drawn from the analysis results. The undamped smart spring system may simultaneously have one starting frequency and one ending frequency or only have one starting frequency, and the damped system may simultaneously have two starting frequencies and one ending frequency. There is an optimal control parameter to make the peak value of the vibration transmissibility curve of the system be minimum. When the mass ratio is far away from the stiffness ratio, the vibration transmissibility is small. The effect of the damping ratio on the system vibration transmissibility is significant while the control parameter is less than its optimal value. But the influence of the relative damping ratio on the vibration transmissibility is small.

Basic dynamic characteristics and seismic design of anchorage system

Based on some assumptions,the dynamic governing equation of anchorage system is established.The calculation formula of natural frequency and the corresponding vibration mode are deduced.Besides,the feasibility of the theoretical method is verified by using a specific example combined with other methods.It is found that the low-order natural frequency corresponds to the first mode of vibration,and the high-order natural frequency corresponds to the second mode of vibration,while the third mode happens only when the physical and mechanical parameters of anchorage system meet certain conditions.With the increasing of the order of natural frequency,the influence on the dynamic mechanical response of anchorage system decreases gradually.Additionally,a calculating method,which can find the dangerous area of anchorage engineering in different construction sites and avoid the unreasonable design of anchor that may cause resonance,is proposed to meet the seismic precautionary requirements.This method is verified to be feasible and effective by being applied to an actual project.The study of basic dynamic features of anchorage system can provide a theoretical guidance for anchor seismic design and fast evaluation of anchor design scheme.