What is voltage type and current type inverter?

Voltage inverter is an inverter that converts DC from a voltage source to AC, and the DC circuit is filtered by a capacitor;

Current type inverter is an inverter that converts DC from current source to AC, and its DC circuit is filtered by inductor.

The main difference between voltage type inverter and current type inverter

First of all, they both belong to AC to AC inverter, the main circuit is composed of rectifier, flat wave circuit and inverter. As the load is generally inductive, there must be reactive power transmission between it and the power supply, so in the middle of the DC link need to have buffer reactive power components, the difference between voltage type and current type is mainly shown as:

　　1, the difference between energy storage components; reactive energy buffer inverter load is an asynchronous motor, an inductive load, between the intermediate DC link and the motor in addition to the transmission of active power, there is also an exchange of reactive power. Since the power electronic switching device cannot store energy, the reactive power can only be buffered by the energy storage element (filter). The difference between the two types of inverters is what energy storage components to buffer the function.

　　2, regenerative braking two are very different.

　　3, the difference between the dynamic response; dynamic response when speed control current-type inverter DC voltage Ua can quickly change the size and direction, so the dynamic response of the speed control system powered by it is relatively fast. In contrast, the voltage inverter, by the dry filter capacitor charging and discharging action to make Ud changes slowly, so its dynamic response is also slow.

　　4, the difference in the scope of application: voltage type inverter is suitable for non-reversible speed control system and does not require frequent acceleration and deceleration occasions, and for multi-motor drive. The current type inverter is suitable for applications requiring fast braking and reversible operation.

The working principle of voltage type inverter and current type inverter　　

      What is the difference between voltage type and current type, for voltage type inverter, the output voltage can be filtered by large capacity capacitor . The structure of the rectifier is exactly the same as the inverter. The working principle is: PWM control is used to control the input current of the rectifier so that the input current waveform is approximately sinusoidal and in phase with the input voltage. When it works as a rectifier, it converts AC energy into DC energy and provides it to the load; it can also work as an active inverter, that is, it converts the feedback energy from the load into AC energy and sends it to the grid, here we call it a chopper rectifier or PWM rectifier.

　　It controls the size and phase of the AC current to make the input AC current close to a sinusoidal wave on the one hand and the power factor of the system close to 1 on the other hand, thus greatly reducing the reactive component of the grid and harmonic interference. At the same time, when the motor deceleration and braking returns regenerative power from the inverter to raise the DC voltage, the phase of the AC input current can be made opposite to the phase of the supply voltage to realize regenerative operation and feed the regenerative power back to the AC grid to keep the DC voltage at a constant value. In this case, the chopped rectifier operates in the active inverter state.

　　The inductor at the input of the rectifier is mainly used to filter out the high-frequency current, and its inductance value is not large, so the voltage drop of the frequency fundamental current on the inductor is very small relative to the grid voltage. Therefore, for the change of load, the control mode of modulation ratio unchanged and phase angle adjustment of input power can be used to achieve constant voltage at DC terminal.

　　For the voltage inverter, the output voltage can be filtered by large-capacity capacitors. Due to the large capacitance, electrolytic capacitors are generally used. In order to get the required withstand voltage value and capacity, the capacitors are often used in series and parallel according to the inverter capacity requirements. For current-type inverters, the DC intermediate circuit filters the output current through an inductor.