How can renewable energy be integrated at a high proportion into the power system? What is the path to achieving a significant share of renewable energy in the grid? The requirements for inverters differ at each stage. Currently, the approach involves combining distributed energy with storage to form microgrids, and automation at different stages requires completely different inverter technologies.
The application of high-proportion renewable energy is generally divided into four stages: distributed photovoltaic development, distributed + energy storage, multi-energy complementary microgrids, and regional energy management platforms. In recent years, distributed PV has seen rapid growth. Integrating distributed generation with the grid helps reduce transmission losses. However, distributed systems are small in scale, numerous, geographically dispersed, and difficult to manage. They are also hard to schedule and deliver instantly, which can be challenging for the grid. Some areas have exceeded their capacity, but regulations limit it. In many regions, only 25% of the park’s electricity is connected to the grid, and when clusters are connected, only 10% is exchanged.
Distributed PV must be paired with energy storage. But how much storage is needed? Simply adding storage isn't enough. One major challenge is dealing with the volatility of wind and solar power. Today, new energy is replacing traditional sources, and solving this volatility requires traditional methods. You need to prepare a plan. As the percentage of renewables increases, it becomes harder to manage without technological breakthroughs. Energy storage costs remain high, so reducing electricity costs is crucial. Lowering system costs is key. The biggest issue is the cost of power supply. How can we improve system efficiency? In the same system, an energy storage system can operate efficiently at 85%, while lithium batteries can reach up to 90%. Electricity costs are still a big concern. Many batteries degrade over time, and managing them online is essential. We’ve made progress in Shanghai, where fixed costs have dropped to about 0.5 yuan, and the peak-to-valley price difference is 0.91 yuan. In Tibet, using lead-carbon and lithium batteries reduced electricity costs to 0.45 yuan. However, the conditions from the local power bureau were favorable, with a PV on-grid price of 1.15 yuan, allowing us to gain some profit. For energy storage systems to be profitable, focusing on electricity cost is critical.
The market potential is vast. Battery manufacturers believe that battery costs will drop below 50% in three years, making electricity costs as low as three cents. This opens up huge opportunities. High renewable penetration requires solving volatility issues, not relying on traditional power plants. Using distributed systems, the grid is still centralized. The future of power is moving towards decentralized and compound development. Security and stability are now top concerns. Beyond energy storage, the next step is to address multi-energy complementarity and microgrid solutions. A simple PV + storage model may work for a year, but without effective monitoring, battery failures can cause problems.
Multi-energy systems are complex. What does the energy management system solve? It deals with photovoltaics, storage, wind, gas, voltage and current sources, power electronics, and synchronous generators. Fluctuations in generation and load, along with differences in storage, require more advanced inverter capabilities. In 2013, a 7.2 MW PV and 28 MWh storage system was completed in Qinghai, operating smoothly for three years. We used a mix of lithium and lead-acid batteries, and the system worked well. Inverters had to support multiple units in parallel. At that time, one inverter was 500 kW, and we used eight to create a 4 MW system. We completed three projects in Qinghai, with 4 MW PV and 40 MWh storage. Economics is essential; without it, projects won’t succeed. We’re planning to acquire an energy storage project in California, which serves the grid. However, we found that the PCS 5 could only charge/discharge at 0.25C, limiting its ability to respond to grid needs. Grid services like peak shaving and frequency modulation require different capabilities. Solving these issues improves system economics significantly. Pure peaking may yield less than 6% ROI globally, but with frequency modulation, it can reach 10%.
In Tibet, we have 18 devices running in parallel, totaling 20 MWh. Replacing traditional energy with renewables is the way forward. When communities can complement each other and reduce grid dependence, it becomes more sustainable. This model can scale if it’s economically viable. The shift to renewables is inevitable. In California, they focus on solar, aiming to leave a cleaner future. In Canada, gas plants use storage for frequency modulation and peak shaving. We need breakthroughs in milliseconds-level control.
The key to large-scale renewable integration is energy storage. While technology exists, improving cost performance is vital. Intelligent inverters allow multiple units to run in parallel, ensuring flexibility. If you don’t convert online, your system can’t keep up with fluctuations. Managing large-scale storage is important. We need to transition from distributed to centralized storage. With falling battery costs, especially lithium and lead-carbon, this trend is clear.
We’ve piloted projects in the U.S., Canada, and Australia, and have several in China. Beijing has set up a department, and investment is growing rapidly. Over two months, over 5 billion yuan was invested by interested companies. Research and development are critical to advancing this technology.
Multi-energy microgrids require optimizing portfolios, combining different energy sources, and developing smart control strategies. Mixed storage systems, like lithium and lead-carbon batteries, offer flexibility. In Tibet, we mix storage to handle fluctuations effectively. Lead-carbon batteries can charge and discharge over four hours, offering different cost structures. Control models must adapt, and fault tolerance is essential. Online updates and improvements ensure system stability.
Traditional storage systems struggle with volatility, requiring changes on the supply side. Many microgrid challenges lie in energy storage. Cost analysis shows that lead-carbon batteries are cheaper than lithium. The core of multi-energy complementarity is the energy management system, which ensures stability, economy, and long-term optimization. Early microgrids need stable and economical operation strategies with learning functions. Control strategies must adjust automatically based on user behavior and data.
Regional energy management platforms are essential. Even large grids can face instability. Controlling microgrid groups improves reliability. Homes with rooftop microgrids can trade energy. Multiple microgrids working together enhance stability and reduce grid reliance. As the grid exchanges less energy, renewable integration becomes smoother.
High renewable penetration demands advanced inverters and virtual synchronous generator testing. Certification platforms with open networks and cloud-based systems are key. Technological breakthroughs and market demand drive success.
Demand-side response policies are crucial. In Australia and California, electricity prices fluctuate frequently, creating opportunities for charging and discharging. Germany’s daily price variations show the impact of pricing mechanisms. China’s grid-based pricing system is evolving. The shift from centralized to distributed energy is not just a market move but a survival necessity. We must continue pushing in new energy fields. I believe high-renewable energy use is achievable.
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