Why does photovoltaic power generation mostly use dual split step-up transformers?
Writer： Hengfeng you electric Time：2023-03-31 views：times
"Why are dual split step-up transformers mostly used in photovoltaic applications? Why are dual split step-up transformers also used for energy storage? What is the difference between dual winding and dual split transformers?" What is the relationship between the two? What is the particularity of a double split transformer? Today, Hengfengyou Electrical Engineer EVAN will share with you. The following views only represent the personal views of Qingdao Hengfengyou Electrical Engineer EVAN.
1. Relationship between dual winding transformer and dual split transformer
Firstly, introduce the winding. Generally, the winding mainly corresponds to a voltage level, and one winding in a transformer corresponds to a voltage level (for example, if the transformation ratio of the main transformer is 132kv/31.5kv, there are two voltage levels, namely 132kV and 31.5kV). The transformers used in general engineering are divided into two winding transformers and three winding transformers, which contain two and three voltage levels, respectively.
Secondly, looking at a split transformer, the difference from an ordinary transformer is that it is divided into several branches with equal rated capacity in its low-voltage winding. There is no electrical connection between these branches, only weak magnetic connection, and there is a large impedance between each branch. Specifically, a three-phase dual winding dual split transformer has two windings, high voltage and low voltage, and splits the low voltage winding into two parts that are electrically disconnected from each other. The two split low-voltage systems can operate in parallel or separately. The three-phase three-winding transformer consists of three independent windings, namely, high voltage, medium voltage, and low voltage, with significant voltage level differences such as 132 kv/33 kv/11 kv.
2. Why does photovoltaic power generation mostly use dual split step-up transformers?
Double split transformers are often seen in large photovoltaic projects, but for photovoltaic power generation projects, the advantage of selecting double split transformers is very prominent.
Currently, large photovoltaic power stations use 500 kW as the basic power generation unit, and the mainstream inverter capacity on the market is also 500 kW. The connection between the inverter and the box type substation is a key step in the entire photovoltaic power generation system. Therefore, considering cost control, it is necessary to select a technically reasonable step-up scheme. Based on this, dual split transformers provide a perfect solution.
The connection between the power generation unit and the step-up transformer mainly refers to the connection between the inverter and the step-up transformer. There are generally three ways to connect:
Scheme 1: One 500kW power generation unit and one 500kVA dual winding step-up transformer form a power generation system - dual winding transformer unit wiring;
Scheme 2: Two 500kW power generation units and one 1000kVA dual winding step-up transformer form a power generation system - dual winding transformer expansion unit wiring;
Scheme 3: Two 500kW power generation units and one 1000kVA double split step-up transformer form a power generation system - double split transformer expansion unit wiring;
Comparison of advantages and disadvantages of the above three schemes:
Scheme 1: Each power generation unit corresponds to one step-up transformer, which has the advantages of simple unit wiring structure and high reliability. However, compared to Scheme 2 and Scheme 3, its cost disadvantage is self-evident. It is generally applicable to projects with relatively scattered power generation units. In order to reduce line losses and reduce wire costs, this connection method can be considered, but it is not suitable for applications in centralized photovoltaic power stations.
Option 2: Both Option 3 and Option 2 are expanded unit wiring methods, which are suitable for the application of large-scale centralized photovoltaic power plants. Compared to the dual winding transformer in Option 2, the dual split transformer in Option 3 has a high cost, but due to its structural advantages, it achieves electrical isolation between the two inverters, not only reducing electromagnetic interference and circulating current effects between the two branches, but also filtering the AC output of the two inverters through transformers, The output current harmonic is small, improving the output power quality. Considering the occurrence of a short circuit, when a short circuit occurs in one branch, in addition to effectively limiting the short circuit current, it can also maintain a certain level of voltage in the other branch without affecting the user's operation.
3. In summary, based on the above comparison between dual split step-up transformers and ordinary step-up transformers, it is obvious that dual split step-up transformers are the preferred step-up transformers for large-scale photovoltaic power generation and energy storage projects. If you have more questions about the photovoltaic double split step-up transformer, please visit www.hengfengyou.com to consult our sales personnel at Hengfengyou Electric.
