From 2018, no matter abroad or domestic, the application proportion of 1500V system is getting larger and larger. According to IHS statistics, the application volume of 1500V for large foreign ground power stations in foreign countries exceeded 50% in 2018; according to preliminary statistics, among the third batch of front runners in 2018, the proportion of 1500V applications was between 15% and 20%.
Can the 1500V system effectively reduce the cost of electricity for the project? This paper makes a comparative analysis of the economics of the two voltage levels through theoretical calculations and actual case data.
I. Basic design scheme
分析 In order to analyze the cost level of the 1500V system, a conventional design scheme is used to compare the project cost with the traditional 1000V system cost.
1, calculation premise
1) Ground power station, flat terrain, installed capacity is not limited by land area;
2) Extreme temperature and extreme low temperature of the project site shall be considered according to 40 ℃ and -20 ℃.
3) The key parameters of selected components and inverters are shown in the table below.
2, Basic design scheme
1) 1000V series design scheme
22 310W double-sided photovoltaic modules form a 6.82kW branch, 2 branches form a square array, 240 branches total 120 square arrays, and enters into 20 75kW inverters (1.09 times over-distribution at the DC side, gain on the back side) Considering 15%, it is 1.25 times over-provisioning) to form a 1.6368MW power generation unit.
The component is installed horizontally in accordance with 4 * 11, and the front and rear double-post fixed brackets.
2) 1500V series design scheme
34 310W double-sided photovoltaic modules form a 10.54kW branch, 2 branches form a square matrix, 324 branches have a total of 162 square arrays, and 18 175kW inverters are installed (1.08 times over-distribution at the DC side, gain on the back Considering 15%, it is 1.25 times over-provisioning) to form a 3.415MW power generation unit.
The component is installed horizontally in accordance with 4 * 17, and the front and rear double-post fixed brackets.
Second, the impact of 1500V on the initial investment
According to the design scheme above, a comparative analysis of the engineering quantity and cost of the 1500V system and the traditional 1000V system is as follows.
Table 3: Investment composition of 1000V system
Table 4: Investment composition of 1500V system
对比 Through comparative analysis, it is found that compared with the traditional 1000V system, the 1500V system saves about 0.1 yuan / W of system cost.
Third, the impact of 1500V on power generation
Using the same components, there will be no difference in power generation due to differences in components; assuming flat terrain, there will be no shadow occlusion due to terrain changes;
差异 The difference in power generation is mainly based on two factors: mismatch loss between components and strings, DC line loss, and AC line loss.
1, mismatch loss between components and strings
数量 The number of series components of a single branch has been increased from 22 to 34. Due to the power deviation of ± 3W between different components, the power loss between 1500V system components will increase, but it cannot be quantitatively calculated.
The number of access paths of a single inverter has been increased from 12 to 18, but the number of MPPT tracking paths of the inverter has been increased from 6 to 9 to ensure that 2 branches correspond to 1 MPPT. The MPPT loss does not increase.
2, DC and AC line loss
公式 Calculation formula of line loss
Q loss = I2R = (P / U) 2R = ρ (P / U) 2 (L / S)
1) Calculation of DC line loss
Table: DC line loss ratio of a single branch
Through the above theoretical calculations, it is found that the DC line loss of the 1500V system is 0.765 times that of the 1000V system, which is equivalent to reducing the DC line loss by 23.5%.
2) Calculation of AC line loss
Table: AC line loss ratio of a single inverter
According to the above theoretical calculations, it is found that the DC line loss of the 1500V system is 0.263 times that of the 1000V system, which is equivalent to reducing the AC line loss by 73.7%.
3) Actual case data
Since the mismatch loss between components cannot be calculated quantitatively, and the actual environment is more responsible, the actual case will be used for further explanation.
This article uses the actual power generation data of the third batch of a front runner project. The data collection time is from May to June 2019, a total of 2 months of data.
Table: Comparison of power generation between 1000V and 1500V systems
From the table above, it can be found that at the same project site, using the same components, inverter manufacturers' products, and the same bracket installation method, during May to June 2019, the power generation hours of the 1500V system were 1.55% higher than the 1000V system.
It can be seen that although the increase in the number of single string components will increase the mismatch loss between components, but because it can reduce the DC line loss by about 23.5% and the AC line loss by about 73.7%, the 1500V system can increase the power generation of the project.
Fourth, comprehensive analysis
Through the analysis above, we can find that compared with the traditional 1000V system, the 1500V system,
1) Can save about 0.1 yuan / W system cost;
2) Although the increase in the number of single string components will increase the mismatch loss between the components, but because it can reduce the DC line loss by about 23.5% and the AC line loss by about 73.7%, the 1500V system will increase the power generation of the project.
Therefore, the cost of power can be reduced to a certain extent.
According to Dong Xiaoqing, president of Hebei Energy Engineering Institute, more than 50% of the ground photovoltaic project design schemes completed by the institute selected 1500V; it is expected that the national 1500V share of ground power stations in 2019 will reach about 35%; it will be further increased in 2020.
IHS Markit, a well-known international consulting agency, gave a more optimistic forecast. In their 1500V global photovoltaic market analysis report, they pointed out that the global 1500V photovoltaic power plant scale would exceed 100GW in the next two years.
Figure: Forecast of the proportion of 1500V in global ground power stations
Without doubt, as the global photovoltaic industry's de-subsidization process accelerates, and the ultimate pursuit of cost of electricity, 1500V, as a technical solution that can reduce the cost of electricity, will be increasingly used