Aug 13, 2020
Introduction to several specifications of photovoltaic inverters
1. Divided according to the nature of the source
Active inverter: It is an inverter that connects the current in the current circuit to the grid on the AC side without directly connecting to the load.
Passive inverter: An inverter that directly connects the current in the current circuit to the load without connecting to the grid on the AC side (that is, inverting the DC power into a certain frequency or adjustable frequency AC power supply load).
2. According to the grid type
Divided into off-grid inverter and grid-connected inverter.
Divided into two-level inverter, three-level inverter, multi-level inverter.
According to power level
Divided into high-power inverter, medium-power inverter, low-power inverter.
3. Common types
1), small and medium power
Small and medium power inverter power supply is one of the important links in the household independent AC photovoltaic system. Its reliability and efficiency are vital to the promotion of photovoltaic systems, effective energy use, and reduction of system costs. Therefore, photovoltaic experts from various countries have been working hard to develop An inverter power supply suitable for household use to promote better and faster development of the industry.
2), multiple series type
Multiple series inverters have many advantages when applied to electric vehicles. The series structure output voltage vector types are greatly increased, which enhances the flexibility of control and improves the accuracy of control; at the same time, it reduces the fluctuation of the neutral point voltage of the motor. The bypass feature of the inverter can improve the flexibility of charging and regenerative braking control.
As people are increasingly concerned about the urban environment, the development of electric vehicles has a rare opportunity. In urban transportation, electric buses have become a priority for development due to their large capacity and high comprehensive benefits. Most electric buses use three-phase AC motors. Due to the high power of the motors, the components in the three-phase inverters need to withstand high voltage and high current stress. Higher dv/dt makes electromagnetic radiation serious and requires good Heat dissipation.
The high-power inverter with a multiple series structure reduces the voltage stress of a single device and reduces the requirements for the device; reduces the dv/dt value, reduces electromagnetic radiation, and greatly reduces the heating of the device; due to the output The level types increase, and the control performance is better.
Multiple series inverters are suitable for high-power electric vehicle drive systems. The use of multiple series-connected structures can reduce the risk of multiple batteries in series, reduce the switching stress of the device and reduce electromagnetic radiation. But the number of batteries required has increased by a factor of 2.
The multiple series structure output voltage vector types have greatly increased, thereby enhancing the flexibility of control and improving the accuracy of control; at the same time, it reduces the fluctuation of the neutral point voltage of the motor. In order to maintain the balance of the power of each battery, it is necessary to ensure that the battery discharge time is consistent during operation. Through the bypass mode, the battery pack can be charged flexibly, and the regenerative braking torque can also be controlled.