A frequency you can count on
生活中几乎没有常数，但是很少有可能包括死亡，税收和美国电网频率的变化不超过±0.5 Hz。但是，由于可再生能源为电网提供动力的可再生能源的增长，网格频率的确定性受到质疑。
The problem is that renewable sources such as solar panels and wind turbines have little in the way of inertia. Inertia in power systems refers to the kinetic energy stored mainly in large rotating generators. Inertia lets generators remain rotating despite temporary interruptions such as a glitch in the fuel supply. Energy arising from inertia can be particularly valuable as it can temporarily make up for power lost from a generator that fails. Inertia energy—typically available for a few seconds—gives power plant controls time to detect and respond to the failure.
But inertia doesn’t just keep power plants online. Inertia resists a drop in grid frequency, which is a measure of the balance of the supply of electricity and demand. Inertia basically gives the grid time to rebalance supply and demand and keep the grid frequency stable.
惯性在较小的网格中往往更为重要。考虑英国的电网，高峰需求约为30吉瓦，不到Ercot（德克萨斯电气可靠性委员会）的一半，该网格是美国增强其惯性的最小网格，英国最近安装了一对大约200吨的飞轮以500 rpm旋转。较小的飞轮，速度为1,500 rpm的速度将在今年晚些时候上线，并计划更多。这些措施是必要的，因为英国电网目前从惯性的风和阳光中获得了大约30％的功率。
In the U.S., the ERCOT grid has the most worries about inertia partly because of its size but also because it contains a large amount of wind energy, accounting for 23% of the state’s power. So far, ERCOT has compensated for declining inertia by adopting several inexpensive methods such as shedding fast-responding noncritical loads in response to changes in frequency.
Eventually, even managers of large grids will need to worry about inertia with the growth of renewable energy sources. A few renewable energy schemes do, in fact, have some built-in inertia. They include biomass-powered generators, concentrating solar power plants, and of course hydropower.
您可能会认为，风力涡轮机在旋转的叶片，轴和发电机的旋转质量中会具有很多动能，这些能量可能会增加网格惯性。但是，大多数现代风力涡轮机不会携带同步发电机，即固有的频率变化。但是，风力涡轮机的动能在将来可能会有所帮助，通过给涡轮机积极地感知电网频率，从而可以对其发电机进行编程以临时提高输出，从而超出稳态风速支持的输出。
Solar panels can also provide inertia-like properties—sort of. The idea is to operate the panel such that its output is below that available based on instantaneous weather conditions, basically so it has power in reserve. The panel inverter can then rapidly increase output to provide frequency support.
Problem is, the panel must have some reserve capacity to provide this kind of support, so there’s an economic tradeoff between providing energy and being able to respond to imbalances. On the bright side, generators that incorporate inverters can respond more quickly to frequency dips than conventional rotating generators.
关于惯性的最后一句话不在。但是，可能需要实验室测试必须将交流线频率添加到必须验证而不是假设的项目列表中。
Leland Teschler•执行编辑
提交以下：EE世界数字问题，，，，DIGITAL ISSUES
