The Greatzhou Edison dream

One hundred years ago, in the struggle for the technical line of communication and direct current, Edison's direct current was eventually lost to Tesla's alternating current. From then on, the one hundred years of AC power system began. But........

there are amplitude, frequency and phase alternating current three quantities need to be controlled, and only need to control the DC voltage, more simple and stable, and the actual use of the final link of electrical equipment is mostly DC (just because of the modern power system is to communicate, so the vast majority of electrical equipment set alternating current in fact, the power supply input, the final part is DC, this point to subvert the intuitive feeling, everyone to explain). But why was AC current lost to DC? The reason is that the power transmission transformer voltage will need to be able to raise and lower the technical conditions at the time, the AC transformer soon to be developed, but DC transformer has been found not to, until the power electronics technology in recent years of development, let the DC transformer become possible, it makes DC have a chance although, this night is one hundred years, but the future trend of power grid will inevitably gradually DC, Edison era will come again.

DC microgrid advantages

1, no reactive problems

The DC system does not exist in the reactive current component in the situation, provide the same power, the amplitude of DC current and the corresponding loss is smaller when the AC system, two times the DC micro grid voltage of AC line voltage, active power loss of the DC line is only the AC line 15%-50%. There is no reactive power problem, and the voltage distribution is independent of the inductance and capacitance parameters of the line, which is more advantageous to voltage control;

2, no phase problems

In AC power network equipment (mainly for power) is closely related with switching phase and phase sequence and frequency of AC DC micro features, online equipment without considering the phase problem, switching easier, stability has also been enhanced;

3. Simple structure

Since most of the new energy generation is DC power, if it is incorporated into the DC bus, only one level conversion is needed, and many converter links are omitted, which reduces the loss, saves funds and improves the reliability;

4, small size

The DC/DC converter adopts high switching frequency, so the power density of the device is much larger than that of the power frequency converter, and the volume is smaller;

5 、 high quality power supply

Since most of the energy storage is direct current, the DC micro grid is easier to access the energy storage devices, thereby providing high quality power supply;

6, green, environmental protection

Direct current does not produce alternating electromagnetic fields, so the electromagnetic radiation is small and more environmental friendly.

Of course, there are some technical problems that need to be solved urgently, such as DC circuit breaker and so on. The implementation process is complicated and the cost is higher.

Application area of DC microgrid

Due to the excellent characteristics of the DC micro grid, its application scene is gradually widened, and the demand for various fields is increasing. From a broad definition, the future expectations will be widely used in the following areas:

1, industrial energy conservation areas

Data center, communication control center, communication base station;

Semiconductor, textile, papermaking and chemical widely used inverter scene;

Substation, metallurgy and other large power electricity;

2. Transportation

Electric drive vehicles, vehicle power system and charging system;

Rail transit power supply;

3, military and national defense

Aerospace power;

Military vehicle power supply;

Ship integrated power supply;

4, civil

DC architecture building, building integrated DC power supply;

Family business, DC micro grid;

Exploration and practice of Shanghai large area DC microgrid

By analyzing the characteristics of a variety of new energy generation and energy storage, and the number of DC micro grid specific needs and practice of refining, Shanghai week high power bi-directional DC-DC converter as a starting point, and gradually extended to the energy management and system design. Painstaking research developed a DCDC converter with high ratio and low voltage high current two series, with independent intellectual property rights of the energy management system PowerNex-EMS, and relying on the related project to verify the results of system planning.