Power Electronic Transformer (PET), also known as Electronic Power Transformer (EPT), Solid State Transformer (SST), and Flexible Transformer (FT), is a new type of transformer that achieves energy transfer and power transformation through power electronics technology. By analyzing and summarizing the existing topology of power electronic transformers, the following definition can be made: a power electronic transformer is a static power equipment that combines power electronic transformation technology with high-frequency energy transformation technology based on electromagnetic induction principles to achieve the transformation of one power characteristic into another power characteristic. The electrical characteristics of electrical energy referred to here mainly refer to the amplitude, frequency, phase, number of phases, phase sequence, and waveform of voltage (or current)
Electronic transformer is a new type of electrical energy conversion equipment, which not only has the basic functions of voltage conversion, electrical isolation, and energy transfer that traditional power transformers have, but also can achieve other additional functions such as power quality regulation, system flow control, and reactive power compensation. The reason why power electronic transformers can achieve these additional functions is mainly because they can flexibly process and control the amplitude and phase of the voltage or current of the primary and secondary sides of the transformer through the introduction of power electronic transformation technology and control technology, and can control the power flow of the system according to actual needs. Therefore, power electronic transformers can achieve more stable and flexible transmission, solve many problems in today’s power system, and their application prospects will also be very broad. [1]
Compared with traditional power transformers, PET has the following characteristics:
① Small in size and light in weight;
② It can be cooled with air, without the need for insulation oil for isolation, reducing pollution, and is easy to maintain with good safety;
③ Can make the secondary side of the transformer output a constant amplitude voltage;
④ It can improve power quality, obtain sinusoidal input current and output voltage, and achieve unit power factor. The voltage and current on both sides of the transformer are controllable, so the power factor can be adjusted arbitrarily;
⑤ With the function of a circuit breaker, high-power power electronic devices can instantaneously (in microseconds of time) turn off large fault currents, eliminating the need for relay protection devices.
In addition, power electronic transformers also have some special applications, such as: after being connected to batteries, they can improve the reliability of power supply; Capable of achieving special transformation functions from three-phase to two-phase or three-phase to four equal; Capable of outputting both AC and DC power simultaneously. In the literature, the author conducted a simulation comparison and analysis of conventional power transformers and self balancing power electronic transformers. The literature mainly conducted simulation research on five working conditions. From the simulation results, PET has good input-output characteristics under conditions such as full load rated operation, one phase disconnection on the low-voltage side, three phase short circuit, as well as three-phase voltage imbalance and harmonic pollution on the high-voltage side, It can avoid the impact of imbalance on one side of the system on the other, and therefore has better performance than conventional power transformers
