In modern society, more and more devices – whether smartphones, laptops, LED lamps, rooftop photovoltaic panels and electric vehicles – are essentially using direct current (DC). However, they have to go through an awkward "energy hurdle" when they are connected to the grid: the direct current output from the photovoltaic panels needs to be converted into alternating current (AC) through an inverter and fed into the grid, and then converted back to DC power through a charger or adapter for use by the equipment. This process often results in energy losses ranging from 5% to 20%, which not only affects efficiency but also drives up system costs.
It is in this context that the DC microgrid (DC microgrid) has emerged as a new power supply architecture. By building a localized and unified DC power network, it realizes the efficient direct connection of power generation, energy storage and power consumption, and greatly reduces the loss of energy in the process of transmission and conversion with the help of advanced power semiconductor devices and control systems, bringing structural changes to the energy system.
Ⅰ. Definition and architecture: the basic framework of DC microgrid
So, what is a DC microgrid? DC microgrids are small-scale energy networks that rely primarily on direct current, typically serving buildings, industrial parks, data centers, islanded systems, or remote communities. Its core components include:
* DC power supply: such as photovoltaic, battery, fuel cell, wind power (rectified), etc.
* DC loads: such as servers, LEDs, electric vehicles, electronic equipment, etc.;
* Power converters: such as DC/DC step-up, step-down converters and bidirectional AC/DC converters;
* DC bus system: as the backbone of energy transmission;
* Intelligent Energy Management System (EMS): Scheduling optimization based on semiconductor control chips;
* External interface: Bidirectional interaction with the traditional AC grid through the converter.
This localized power grid structure maximizes the advantages of DC power terminals, improves the overall system energy efficiency and control accuracy, and the core technical support is the wide application of semiconductor power devices in various nodes.
Figure: Popular Science Article: Exploring the Rise of DC Microgrids
Ⅱ. System anatomy: six drive modules
The efficient operation of the DC microgrid depends on the synergy of six core modules, all of which are inseparable from the support of power semiconductor technology:
1. Distributed DC power supply
* Photovoltaic modules: direct current output, connected to the bus after voltage optimization by DC/DC converter (based on IGBT or MOSFET);
* Wind turbine: the output is variable frequency alternating current, which needs to be converted to DC through a rectifier bridge (diode or IGBT based);
* Fuel cell system: Native output DC, suitable for direct connection applications.
2. Energy storage system
* Lithium-ion battery pack: Charge and discharge control is completed by a bidirectional DC/DC converter (usually SiC MOSFET), and the functions of voltage matching and energy regulation are realized.
3. DC load
* Data center: Server CPUs and GPUs are all DC powered, and traditional solutions require multi-stage conversion, which is inefficient.
* Electric vehicle fast charging pile: high-power DC output is used to achieve faster energy replenishment;
* LEDs & Consumer Electronics: Typical DC end-users.
4. Power electronic converters
* DC/DC converter: support buck-boost, isolation and multi-port functions, using Si, SiC, GaN and other devices;
* Bidirectional AC/DC converter: the interface connected to the main network, widely used in IGBT modules.
5. DC bus platform
* Common voltage levels are 380V, 750V, 1500V, etc., with standardization, high stability and low loss, relying on high-speed semiconductor switches and bus control strategies to ensure smooth power.
6. Energy Management System (EMS)
* Integrated ARM processor, FPGA, DSP and other control chips, responsible for scheduling distributed energy resources, energy storage units and loads, to achieve real-time optimization of energy flow.
Ⅲ. Advantages are highlighted: four major system improvements
1. Energy efficiency improvement
* Avoid repeated AC-DC conversion, and improve the overall efficiency of the system by 10%-20%;
* High-frequency SiC devices achieve a conversion efficiency of more than 99%, especially suitable for high-energy consumption scenarios such as electric vehicles and data centers.
2. System simplification
* Significantly reduce intermediate links such as inverters and adapters;
* Integrated DC/DC power modules can be used to improve reliability and reduce maintenance complexity.
3. Renewable energy friendly
* DC output solar and energy storage systems can be directly connected to the microgrid;
* SiC/GaN devices provide fast dynamic response capability, realize millisecond-level power adjustment, and adapt to distributed energy fluctuations.
4. Power supply stability is enhanced
* Eliminate the problem of frequency fluctuations in traditional AC power grids;
* Using IGBT and PWM control technology, high-precision voltage regulation and load adjustment are used to ensure high-precision power demand.
Ⅳ. Key application scenarios: Promote commercial implementation
1. Green Data Center
* Google, Facebook, and other companies have begun to deploy a 48V/380V DC power supply architecture to avoid multiple AC-DC conversions, and the PUE (energy usage efficiency) can be optimized to less than 1.2.
2. Integrated system of optical storage and charging
* Demonstration projects in China and Europe adopt the path of "photovoltaic DC - energy storage DC - electric vehicle fast charging DC" to reduce conversion losses and improve infrastructure utilization;
* The SiC power module supports ultra-fast charging of more than 350kW and can charge 400 km in 10 minutes.
3. Semiconductor manufacturing plants
* Chip production equipment has extremely high requirements for power supply quality, and DC microgrid reduces the interference caused by fluctuations by stabilizing bus voltage and fast adjustment technology.
4. Off-grid and remote power systems
* In Africa, Southeast Asia and other regions, DC microgrids built by photovoltaic + cells replace diesel power generation;
* Semiconductor converter improves system reliability, independent operation and adaptive load adjustment.
Ⅴ. Development bottlenecks: three major challenges that need to be broken through urgently
1. DC disconnect technology
* The DC system lacks a natural zero-crossing point, and it is easy to generate continuous arcing during the circuit breaking;
* Solid-state circuit breaker (based on IGCT or SiC device) is required to achieve microsecond fast cut-off.
2. Standards and Compatibility
* The voltage platform has not been unified, 380V/750V/1500V coexists;
* The degree of standardization of communication protocols and control interfaces is not high, which limits the interoperability of multi-vendor equipment.
3. Cost of power devices
* Compared with traditional silicon-based devices, the price of SiC/GaN is still high;
* The cost of high-power DC/DC conversion module accounts for 25%-35% of the overall cost of the system, which restricts large-scale deployment.
According to > Wood Mackenzie, the global DC microgrid market size has reached $10.7 billion in 2023 and is expected to exceed $22 billion by 2030, growing at a compound annual growth rate of 12.3%.
Ⅵ. Future prospects: the synergistic revolution of DC and semiconductors
As the cost of third-generation semiconductor (SiC, GaN) devices continues to decline, the performance of control algorithm chips improves, and the supporting standard system is gradually improved, DC microgrids will accelerate into the stage of large-scale deployment
* At the household level: form a DC self-circulation system of "photovoltaic + energy storage + electric vehicle";
* At the city level: support for building-level DC distribution and bus fast charging infrastructure;
* Industrial level: help semiconductor and precision manufacturing enterprises realize full DC energy systems and reduce the risk of interference and surges.
This semiconductor-driven "DC power revolution" is reshaping the entire chain from power generation, transmission, storage to terminal power consumption. In the future, when every electron emitted by solar panels can reach your mobile phone battery without barriers, the true efficient energy transmission will be realized - this is the intelligent evolution path that semiconductor technology gives to the power system.
> The future belongs to DC, and it belongs to the chip technology that controls DC.
