How to realize green grid by inverter
While the world is trying to prevent catastrophic climate change, the power generation industry is recognized as the most important sector to eliminate carbon emissions.
For this reason, more than half of the states, including large states such as California, Texas, and New York, are obliged to supply electricity by renewable energy, and the same goals have been set in the EU renewable energy command.。The integration of renewable energy resources is a major issue for power companies, especially due to the intermittent and vulnerability of wind power and solar power.
The cost of wind power and solar power has dropped sharply in the past decade, and in many cases, especially in the grid scale, it will compete with fossil fuels.As can be seen from the fact that companies such as Wal -Mart, Targets, and Amazon have a large amount of solar panels in warehouses and retail stores, the installation on commercial and industrial scale is extremely economical.In addition, with the constant progress of offshore wind power generation and floating solar panel technology, the suitability of renewable energy has been expanded.
In addition to the expansion of residential solar power generation capacity, another challenge for power companies is the integration of distributed energy resources that are not under the company's management.Some states of the United States have a regulation that obliges the fixed-price purchase system (Feed-in Tariffs) for net meters and behind-THE-METER (consumer side), which makes management more complicated and affected by power companies.Give.
Another major issue is the safety and reliability of grid infrastructure related to climate change.Recent landmarks in California and PG & E are early indicators indicating how abnormal weather and climate changes affect the power network.PG & E is still planning to stop transmission power to protect facilities, customers, and forests.
Other equipment to be added to this is energy storage.There are many forms of energy storage, including pumping, large flywheels, underwater pressurized blades, or cranes that lift huge concrete blocks.Many of these options require considerable geographical characteristics, such as built on a very large scale to increase economics.
The most prominent and rapid growing energy storage technology is a storage battery.Storage batteries are very highly expandable and can be used from home size to power plant size.In addition, it can be deployed in almost every location without the enormous environmental evaluation, infrastructure construction, and regional regulations that must be considered on the conventional power plant site.
Finally, it demonstrates that various companies can introduce large -scale batteries in the shortest half a year.This is extremely contrasting with the decades of investment periods required to plan and repay fossil fuels.
Energy storage is particularly advanted by combining intermittent renewable energy.The most obvious usage of energy storage is the ruling trading of energy.The energy is stored when the electricity price is low, and it is released to the transmission network when the electricity price is high.On a sunny day when excessive power generation from the source of solar power (PV) occurs, electricity can be used to the storage elements and the resources that should be undertaken can be used to the fullest.In the evening, when solar power is stopped, it supplies power that has been lost in storage batteries while the base road power generation is increasing.Therefore, the solar cell firm has many large -scale battery facilities.
If PG & E blackout customers during the risk of fire, families and companies can survive the power outage using storage batteries and solar panels, preventing important processes interrupt or rotten.increase.In addition, electricity companies are currently coordinating distributed energy resources as "virtual power plants" that generate, store, and release electricity according to demand.In some cases, it also includes a demand response that shifts the power load when off -peak.
An important interface that connects wind, solar and storage battery resources into power grids.To put it simply, the inverter converts DC power into an exchange power that synchronizes to 60Hz frequency of the grid.Figure 1 is a simplified solar panel connected to the grid, focusing on the inverter structure.The inverter has multiple topology of single -direction, two -way, and multi -level inverters, each with its strengths and weaknesses, and can be used properly depending on the situation.The main device of the inverter is a power switch, showing the insulating gate bipolar transistor (IGBT) in the figure.
With microcesses, appropriate sensing and feedback, and appropriate algorithms, inverters can provide various services to the grid, not limited to the accumulation and discharge of electric energy.One example is the maintenance of power quality through voltage support, frequency adjustment, and harmonic reduction reduction.Distributed energy resources are used near the place where electrical energy is generated, so that the load on the transmission and distribution network can be reduced.This can reduce grid distortion and congestion and even postpone the update of power lines.
Since a large amount of power passes through the inverter, the inverter needs to convert between AC power and DC power very efficiently.In fact, the maximum efficiency of the commercially available inverter is 96-98 %.However, grid operators are seeking even higher efficiency, especially on power plants, as the slight changes in efficiency are significant power.
To achieve these efficiency levels, the power device loss must be extremely low.At present, IGBT is the best switch for these applications.Surprisingly, IGBT, which flows hundreds of A and blocks several thousand V, is manufactured from silicon using the same process used to manufacture high -performance computing chips for telephone and data centers.。
However, new materials promise to achieve higher performance, efficiency, and reliability.Specifically, a silicon carbide (SIC) is a future material.SIC Power Electronics Devices have lower conduction and switching losses than similar silicon devices.In the first stage of this migration, a free wheel diode that is connected in parallel to IGBT is used, as shown in Fig. 1.Replacing the silicon diode with a SIC diode reduces the loss, reducing overshots during switching, reducing the burden on the inverter.SIC diodes are more expensive than silicon diodes, but can reduce the total system cost by miniaturization of heat sinks and the entire system.
SIC MOSFET is the next stage of the migration.SIC MOSFET has a much higher advantage of the solar power generation system because it can switch much faster than silicon IGBT.In general, the output voltage of the solar panel is raised using a DC-DC converter.SIC MOSFET reduces the size of expensive passive elements such as inductors in the boosting stage by switching at high speed and improves efficiency.
On semiconductors provide a wide range of IGBT, SIC diodes, and SIC Mosfet that correspond to various voltage and current requirements of the inverter.The most popular is the power module, and the many different power switches and diodes are packaged, providing small, easy to design and efficient heat dissipation.On semiconductors have gate drivers, galvanic insulation, high -performance operational amplifiers, etc. in addition to the main power electronic devices.
summary
As the renewable energy and energy storage technology are improved and the cost is reduced, the grid "inverter" is increasingly accelerating.The inverter not only eliminates carbon emissions and pollution, but also enables more elastic participating grids with ambiguous boundaries between consumers and producers.Appropriate control and coordination allows power companies to improve power quality, reduce upgrade costs, and provide more reliable services.Power Electronics is a key to renewing important power generation equipment.