Solution to High Voltage Instantaneous Power Loss of High Voltage Inverter

1. Introduction:

In the context of energy conservation, consumption reduction, and environmental protection being the key focus of national work, the most effective energy-saving products, high-voltage frequency converters, are increasingly widely used. In order to meet the various requirements of users, the functions of frequency converters are becoming increasingly diverse. However, due to the fact that high-voltage frequency converters are mostly used in important occasions, problems in this link will cause varying degrees of losses. In various application places, there is a situation of high-voltage instantaneous power loss, For example, when switching between two power sources in a factory, or when the power grid malfunctions and instantly recovers, the general high-voltage frequency converter will protect and shut down after the input voltage drops for more than a certain period of time or after the input power drops, or at most after supporting operation for a few seconds. This phenomenon has occurred multiple times in China and led to unit shutdown (including some examples of using imported high-voltage frequency converters). The POWERSMART series high-voltage frequency converters have fully studied and considered the influence of this factor. After input drop or input power failure, as long as the voltage returns to normal within the set time (up to 30 seconds), they can start without impact and drag the motor to the state before operation without terminating subsequent production. Therefore, it is necessary for the frequency converter to have the function of "high-voltage instantaneous power loss restart".

2. Control composition of JZE high-voltage frequency converter

The control unit cabinet is mainly composed of main controller, temperature controller, fan protector, human-machine interface (color touch screen), PLC, embedded microcomputer, switching power supply, EMI module, isolation transformer, air switch, contactor, relay, analog module, switching value module, etc.

The main controller consists of a bus board, power supply unit, CPU unit, interface unit, three phase control units, and input and output submodules for switching and analog quantities. It is the control core of the frequency converter, consisting of two DSPs, multiple FPGAs, CLPD, etc. It transmits PWM signals to the power unit through high-quality optical fibers, thus achieving highly reliable control.

The temperature controller can be connected to three temperature sensing probes to test the temperature of the cutting transformer and provide alarms or protection nodes.

There are three fan protectors used to monitor the phase loss, overcurrent, etc. of the fan. Among them, there are 2 connected to the power unit cabinet and 1 split transformer cabinet.

PLC, with built-in PID adjustment module and program, can achieve closed-loop control. It also includes analog and switching modules, and the number of channels can be customized according to user requirements.

The human-machine interface is located on the front door of the control unit cabinet to provide settings, monitoring, and switching operations. It has Nixie tube mode and color touch screen mode, which can be selected according to user needs.

2. Characteristics of high-voltage instantaneous power loss restart function

The high-voltage instantaneous power loss restart function should have the following two stages

When the frequency converter loses power during operation and the recovery time is within 9 seconds, the frequency converter does not stop. When the high voltage is restored, it automatically returns to the original set frequency for operation.

2. When the inverter loses power instantly during operation and the recovery time exceeds 9 seconds, it will recover within 30 seconds, and the inverter will automatically restart to the set frequency.