Yang Panfeng: Introduction to the Multi-energy Complementary Project in Qinghai Province

The final optimization result is that the total power abandonment rate of renewable energy is 5%, which includes the loss of peak-shaving power sources. We call it the generalized power abandonment rate, which is equivalent to calculating all of this. Through the multi-energy complementary system and long-term transactions, Qinghai can meet the DC power transmission needs. Now this research conclusion is controversial, but it is the conclusion of our research, because DC control is about to be implemented.

After comprehensive multi-energy complementation, the typical curves of power generation of various power sources in a week can be seen. For example, on the previous day, the power generation of new energy was better, and there was some power abandonment, and different combinations can be seen. I will not introduce it in detail here.

I just introduced the multi-energy complementarity in Qinghai Province, which meets the load of the whole province and the DC power transmission. The following is an introduction to the specific multi-energy complementarity projects. Haixi multi-energy complementarity is one of the first phase of integrated optimization demonstration projects of multi-energy complementarity announced by the state. It is located in Golmud City, Haixi Prefecture, with a total power supply scale of 700,000 kilowatts. At present, wind power and photovoltaic power generation have been completed, solar thermal power has started construction, and energy storage is being designed. It is planned to be fully connected to the grid for power generation by the end of December 2018. This is the first multi-energy complementarity project started by the National Energy Administration. The design of multi-energy complementarity is mainly aimed at the power supply of energy storage. It has two types of energy storage power sources, one is the solar thermal power station, and the other is the battery. These are two types of energy storage power sources. The design of these two types of energy storage power sources actually involves an optimization process. This is for the solar thermal power station. Because the large structure of the solar thermal power station includes energy storage and power generation. Only when the ratio between the three reaches an optimal level can the investment of the entire power station be minimized. From the perspective of the power station itself, each curve is a different mirror field area, and the corresponding horizontal axis is the heat storage time of the heat storage tank. It has the corresponding most economical point, the configuration of the proportion of the mirror field, energy storage and power generation system. In fact, judging from the power station itself, the final selected mirror field area is 660,000 square meters, which is 12 hours of energy storage.

If you participate in the entire multi-energy complementary system, this system has 400,000 wind power and 200,000 photovoltaic power, and there is a certain amount of power abandonment. This is the power generation process of the solar thermal power station on a sunny day. The top red line is the power of the mirror field, the bottom line is the power absorbed by the collector, and the bottom line is the heat absorption power of the heat tank. The heat tank has storage and discharge. If there is no sun later, it will be discharged through this. There are several main modes for the solar thermal power station to participate in peak regulation: 1. Reduced output mode. The Qinghai power grid is mainly in the noon photovoltaic peak period. The peak regulation capacity is insufficient, so the solar thermal power station needs to store energy. When the sun is better, try not to generate electricity. This is equivalent to reducing the actual power generation of the red part. The blue is the resource conditions, and this is moved to the later power generation. It is equivalent to reducing the output peak regulation. 2. Start-stop peak regulation. When the light resources are particularly good, the solar thermal power station is stopped and only energy storage is carried out. It is also moved to the second half of the night for power generation. 3. Shift. If it is predicted that today's energy storage can meet the conditions, power generation will be more flexible. The solar thermal power station will start a little later to avoid the noon process. I just introduced several heat storage processes.

The participation of CSP power stations in peak regulation is the same as that of batteries and conventional coal-fired units. The thermal efficiency at different working positions is also different. It has certain losses in participating in peak regulation, which means that its efficiency will be reduced, which will lead to a reduction in its own power generation. There is a loss of energy loss in the start and stop operation. When running at low load, the efficiency will also be reduced. Some numbers are listed here. CSP power stations have certain peak regulation advantages over conventional coal-fired power. First, the adjustment speed of CSP power stations is faster and the adjustment depth is greater than that of conventional coal-fired power units. Second, it is more convenient to start and stop. Start, stop and shift, CSP power station, you choose the heat storage time, for example, 14 hours, today the sun only has 14 hours of heat, which can be stored in full through energy storage, and you can generate electricity whenever you want, which means flexible scheduling. If the weather is good today, it may take more than 20 hours of power generation, so some electricity must be generated during the day. This involves the use of start-stop or shift peak regulation.

What I just introduced is the peak-shaving method of the CSP station. We calculated that if the CSP station participates in the peak-shaving, the amount of abandoned power of photovoltaic and wind power in its system will be reduced. It can be seen that the change in the energy storage time will reduce the amount of abandoned power in the multi-energy complementary system as it changes. When designing the CSP station, more energy storage is added to reduce the abandoned power of wind and photovoltaic power. We convert the abandoned power of photovoltaic and wind power into the CSP station according to our own grid-connected electricity price level, which is equivalent to letting the CSP station gain benefits. It can be seen that the CSP station does not peak-shaving and the CSP station peak-shaving, which requires the heat storage time of the CSP station, and the optimal heat storage time will be extended backward. For CSP stations, the heat storage time is better to be 12 hours, and if it participates in peak-shaving, it will take 13 hours. For the energy storage of CSP stations, we have studied other solutions. Through energy storage, when photovoltaic and wind power are in high demand, the problem of power abandonment cannot be solved. A part of the electric power can be directly stored in the heat storage device of the solar thermal power plant through electric heating. The heat storage tank of the heat storage power station is relatively large, which can further reduce the gas power in the power grid. In fact, it is similar to the heat storage of our electric boilers, but this heat still needs to generate electricity in the end. At present, we are combining the technical maturity and economic efficiency of the equipment to further demonstrate the feasibility of the electric heating solution.

As for storage batteries, Dr. Lu from the State Grid Energy Research Institute introduced them earlier. We think there are several applications for batteries. One is to smooth the output curve of wind power. In this system, how to make the curve smoother? The other is to reduce peaks and fill valleys, and participate in the peak regulation of the system. The second is to track the planned output curve, and the other is to participate in the frequency regulation of the system. When designing the system, we first want to analyze what role the storage battery will play. Different roles require different battery capacity choices. In this project, the Qinghai power grid has a high proportion of water points, which means that there is basically no problem with peak regulation. The power of hydropower can be adjusted very quickly, and there is no need for frequency regulation. The main application is still to be regarded as an energy type, with the function of reducing peaks and filling valleys. The positioning of the storage battery here is mainly energy type. In terms of assessment, it can be adjusted to the smooth output mode when the wind and solar power output is not limited. If the output curve reported by the power grid is inaccurate, it can be corrected through energy storage. The use of energy storage batteries is mainly for peak regulation, and the smooth output curve is supplemented.

The battery is mainly used to reduce wind and solar power curtailment. So, if we install a 50,000KW energy storage power station, we can see the different storage durations of energy storage batteries. Similar to solar thermal power, as the storage duration increases, the amount of wind power and photovoltaic power curtailment also gradually decreases. Now, from the engineering work, the overall economic return is relatively poor, because batteries are still relatively large as energy storage. It may be that the long time is chosen, and the rate of return is relatively poor. This means that the final choice of this project is 2 hours or 1 hour. When it was designed, it was done for 2 hours, and it is also possible to do it for 1 hour. This is the battery solution used by the energy storage power station, including power collection.

At that time, the research team also included the Institute of Electrical Engineering, which proposed the technology of virtual synchronous machine. Now, we have not seen any profit model, so we basically did not do so this time. This includes the frequency regulation and primary voltage regulation, and energy storage, because the inverter can be used as dynamic reactive power compensation, which was not mentioned by the previous speakers. It can be developed into the technology of virtual synchronous machine.