电网频率

The simulated results show that the proposed method and the approximate algorithm can be readily put into practice.

结果表明，上述方法可有效地改进电网频率和谐波的测量准确度，具有工程应用价值。

According to the importance of frequen-cy in power system operation,the authors tested andcalculated the frequency attenuation time constant Tfand the static load frequency coefficient KL,whichcharacterinze the frequency variation of power system.

根据电网频率运行的要求，对表征电网频率特性的频率衰减时间常数Tf、静态负荷频率调节系数KL进行了试验研究和理论分析计算。

Characteristics of power system frequency abnormal distribution.

电网频率的非正态概率分布特性。

The capacitance capacitors and inductors of power grid form parallel resonance circuit .It's frequency may be related to the existing power grid close to the harmonic frequencies, If there is power grid harmonic current sources, harmonic resonance caused by enlarged so that the voltage and current waveform distortion even more serious.

电容器的电容和电网的电感形成并联谐振回路，其频率可能与电网中存在的谐波频率接近，如果电网存在谐波电流源，谐振引起的谐波放大使电压和电流波形畸变更为严重。

We choose the TMS320VC5402, digital signal processor, as the computing unit, filtering the sampled signal, truncating the harmonic whose frequence greater than 2500hz, then we use the window-interpolation FFT algorithm to get the refined frequence, amplitude, phase of harmonic in sampled voltage and current, other parameter such as harmonic ratio, active power, reactive power, power factor, three-phase unbalance can be also computed base one the result of window-interpolation FFT.

选用TMS320VC5402高速数字信号处理器作为运算单元，先对采样信号进行数字滤波，去除50次以上谐波分量，然后应用加窗双峰插值FFT算法计算电压电流的各次谐波频率、幅值和相位，以及谐波含有率、有功功率、无功功率、三相不平衡度等各项电能指标，同时利用锁相环电路硬件跟踪电网频率以减小采样失步度。

As a rule, the mains frequency is imposed on the wind turbine.

原则上，主电网频率是强施于风机上的。

In the case of wind turbines operating in parallel with the mains, a fixed mains frequency is assumed.

在风机与主电网并行运行情况下，应设定固定主电网频率。

When microgrid is operated in islanded mode, VSGs can be divided into non-frequency regulation units and frequency regulation units, the former can generate power and participates in primary frequency control according to dispatching to mitigate system frequency deviation due to disturbances; the latter can offer referential voltage of microgrid and use secondary frequency regulation to implement no-error frequency control.

微电网孤岛运行时，将虚拟同步发电机分为非调频发电单元和调频发电单元，前者既能按照功率调度指令发电，又能参与一次调频，缓解扰动情况下系统频率的波动，后者提供微电网参考电压，并利用二次调频实现频率的无差控制。

The following functions can be realized: Measuerment:the effective values of three phase current and voltage, power frequency, active power, reactive power, power factor etc. Motor control: direct starting, converse starting, star and triangle starting, self-starting. Protection:thermal overload protection, current leakage protection, open-phase protection, three-phase unbalance protection, over voltage protection, loss voltage protection, low load protection and fault warning and fault dates memory. Communication: communication of the computer in control room and the microcomputer monitor in the spots is realized by the interface of RS-485. The motor is not only controlled in the spots but also in control room. The dates, information and some functions are shared by the spots and control room too.

该电动机监控器以80C196KC单片机为核心，通过采样三相电流﹑电压信号来实现以下功能：三相电流﹑电压有效值，电网频率，有功功率，无功功率及功率因数等的测量；对电动机实现直接、正反转、星三角及自起动控制；对电动机实现热过载、漏电、断相、三相不平衡、过压、欠压及轻载保护，对故障进行报警及数据记忆；通过RS-485串行接口与中央控制室计算机实现通信功能，对电动机既可本地，也可远程控制；实现控制现场与控制室之间数据、信息、功能共享。

The simulating results indicated that the proposed wind power generation-flywheel system could supply steady output power, and could participate in the power grid frequency control.

结果表明，在飞轮辅助下，风力发电-飞轮系统可以按要求输出平稳的功率，并且可以像传统发电机组一样参与电网频率控制。

However, as the name（read－only memory）implies, CD disks cannot be written onorchanged in any way.

然而，正如其名字所指出的那样，CD盘不能写，也不能用任何方式改变其内容。

Galvanizes steel pallet is mainly export which suits standard packing of European Union, the North America. galvanizes steel pallet is suitable to heavy rack. Pallet surface can design plate type, corrugated and the gap form, satisfies the different requirements.

镀锌钢托盘多用于出口，替代木托盘，免薰蒸，符合欧盟、北美各国对出口货物包装材料的法令要求；喷涂钢托盘适用于重载上货架之用，托盘表面根据需要制作成平板状、波纹状及间隔形式，满足不同的使用要求。