Re: Grid 2 Limited Edition Multi 8 Crack [UPDATED]
Indira Rossetto
To run the grid reliably and affordably, we need new cost-effective technologies capable of storing electricity for multiple days. Our first commercial product is an iron-air battery capable of storing electricity for 100 hours at system costs competitive with legacy power plants.
Apart from this, the multi-threading facility works in the same way as the Grid facility. The solve statement generates the model and passes it to the solver in a separate thread, then a handle of the model instance may be stored using the model attribute handle and the grid handle functions may be used to collect the solution and deal with the model instance, namely handleCollect, handleDelete, handleStatus and readyCollect.
To adapt to the characteristics of new energy long-distance transmission, this paper proposes a scheme of multi-fed voltage source converter grid connection and line-commutated converter transmission for a regional large energy base. First, the feasibility of this multi-infeed direct current (DC) transmission scheme is discussed. Then, the performance characteristics of the multi-infeed DC and other traditional transmission technologies are compared and analysed. In addition, the economic benefits of the multi-infeed DC project are evaluated. To study the characteristics of new energy multi-infeed DC power transmission mode, a long-distance energy transmission system based on multi-infeed DC power transmission mode is built using DIgSilent software. On the basis of the continuous power flow method, the static characteristics of the system are studied. Based on the time-domain simulation method, the transient characteristics of the system are studied. The results show that multi-infeed DC has great advantages in large-scale regional new energy long-distance transmission.
A large amount of literature has investigated new energy consumption. By improving the peak shaving capacity of the system, building a complete DC transmission project, and rationally configuring the layout and power structure of new energy, the new energy consumption can be improved (Niu et al., 2016). Power grid commutation DC transmission has the advantages of large transmission capacity, the transmission length not being affected by distance, low cost and so on (Li et al., 2017). A large number of ultra-high-voltage (UHV) and DC transmission topologies make AC/DC hybrid power systems more and more common. A large number of DC terminals and grid structures interconnected in the form of DC appear in the grid (Tang et al., 2013). Comparing with the traditional DC transmission mode, flexible DC transmission can achieve independent active and reactive power control and black start without commutation failure (Zheng et al., 2013). Using VSC flexible DC transmission technology, many wind farms and photovoltaic power stations are joined together to form a regional DC power grid, which promotes the regional complementarity of new energy sources to a certain extent, and then LCC-DC and DC/DC transformers can be used to realise large-scale outward transmission of new energy. This multi-feed DC power grid topology will become an important structure of future DC power grids (Liu et al., 2014a), However, this paper does not demonstrate this in detail. For large-scale wind farms connected to the grid by VSC-DC, the seamless switching between the operation modes of AC and DC parallel systems can be realised by adjusting their operation control strategies (Li et al., 2015; Wang et al., 2014). However, when many large-scale wind farms are scattered in a large geographical area, multi-infeed DC is more suitable to connect with the grid. The research on multi-infeed DC systems mainly focuses on the important components such as topology, control strategy and converter station. The designed system lacks overall coordination and cannot reflect the dynamic characteristics of each part of the whole system. The AC transmission model and economic analysis method can be improved and applied to flexible DC transmission (Liu et al., 2018). In order to facilitate the advantages of DC transmission and save engineering costs, it is proposed to change the existing AC line to a DC line. However, the original grid structure and its scale need to be considered in this scheme (Liu et al., 2013; Peng et al., 2017; Yang et al., 2014).
The performance comparison results of the above three grid connection modes are shown in Table 1. Through the analysis of AC transmission technology, flexible DC transmission technology and multi-infeed DC transmission technology (Li et al., 2016, 2018; Yang et al., 2014), the data in Table 1 are obtained. According to Table 1, the performance of the LCC-DC grid connection mode is far lower than other two grid connection modes. The transmission capacity of VSC has been greatly improved. It has obvious advantages in the application of new energy DC grid connection and high feasibility in terms of engineering. Due to the small initial investment, an AC grid-connected system has certain advantages. In practical engineering, the factors such as grid conditions, scale of wind farm construction, project cost, operation and maintenance, system loss and so on should also be taken into account.
The normal steady-state conditions of the simulated new energy multi-feed into the grid are verified by quasi-dynamic simulation. The transmission power curves of the three new energy bases are shown in Figure 3. According to Figure 3, the trend of power transmission in the three new energy bases is different. The actual output of new energy through VSC grid connection is significantly higher than that of AC grid connection.
The power of each large wind farm and photovoltaic power station converges at the LCC converter station. Due to the fluctuation of new energy sources, the LCC rectifier station needs to supplement power from the AC system. In an AC grid-connected system, the main network needs to supplement more active power, and the main network provides a large amount of reactive power for LCC DC commutation. When multi-feed VSC is connected to the grid, the loss of new energy is very small, and reactive power compensation is provided by itself, which relies less on the AC system. Figure 4 shows the amount of electricity absorbed from the AC system by new energy sources due to insufficient volatility output.
The output of the DC channel in this scenario is shown in Figure 6. When an AC grid-connected mode fails, the voltage of an AC bus in the rectifier side of the LCC DC channel decreases, and the rectifier side enters the fixed minimum trigger angle control to improve DC voltage. The inverter side adopts the fixed DC current control and reduces the setting current. The system reaches a new balance point. However, the power shortage, the power supply reduction and the recovery occur after the fault clearance. When the multi-feed VSC is connected to the grid, the fault has little effect on the AC system voltage. Because the DC short-circuit current recovers quickly, it only causes the short-term power fluctuation of the system. Then the system voltage returns to normal, and the LCC DC channel returns to normal transmission power.
The transient characteristics of photovoltaic power plants caused by faults are similar to those of wind farms. Generally, the fault-recovery ability of the system is affected by the grid connection mode. The long-distance transmission network of AC system is weak and its stability is poor. The VSC DC system has the advantages of small loss, flexible control strategy, strong fault voltage and current-regulation ability. By adjusting the parameters through simulation, it is concluded that the stability of the system is mainly affected by the grid-connected mode, control strategy, multi-feed-in AC system and the strength of the receiving-end AC system. In an VSC DC grid-connected system, each component needs to have a short-term overvoltage and overcurrent tolerance. In the follow-up study, power flow control devices and improved control strategies can be considered to enhance the stability of the system.
The geographical distance between the energy-rich areas in north-west China and the economically developed areas in south-east China is far. In this case, if the traditional AC outgoing mode is adopted, there are some problems, such as small capacity, large loss and great influence on the regional AC system. For this reason, this study proposes a scheme of multi-fed VSC grid connection and LCC transmission for a regional large energy base.
The transient characteristics and static characteristics of multi-infeed DC and traditional AC grid-connected modes in fault process are compared and analysed. The results show that the multi-infeed DC grid-connected mode, which is used for a large number of regional new energy grid-connected systems, can suppress the intermittent fluctuation of new energy, increase the consumption of new energy and reduce the dependence of the traditional LCC DC transmission end on the AC power grid.
The time-domain simulation analysis is carried out for the multi-regional large-scale new energy base which adopts multi-feed DC grid connection and traditional AC grid connection. The results show that the new energy can be more complementary in time and region by using multi-feed DC grid connection and three-stage stabilisation. At this time, the consumption of new energy has increased by about 25%, and the dependence on the AC system at both ends has been weakened. Under the conditions of the traditional AC grid-connected systems in a new energy base, the transient process of fault short-circuit current takes a long time and fluctuates greatly. When the new energy base adopts multi-feed DC grid connection, the fault short-circuit current only oscillates for a short time and recovers very quickly.
Looking ahead, Form Energy projects New York will require at least 3 GW per year of new multi-day storage capacity between 2030 and 2040. Near term policy action to establish incentives, market mechanisms and contract structures will give the private sector needed market signals to invest in manufacturing and project development for emerging technologies like iron-air batteries. Then these resources can be deployed at scale to maximize cost savings and grid reliability as New York pursues its ambitious decarbonization timeline.
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