Control method for tri-level inverter
A technology of a three-level inverter and control method, which is applied in the direction of converting irreversible DC power input to AC power output, can solve the problems of low switching frequency and output current distortion, and can solve the problem of excessive ripple current frequency range. big effect
Active Publication Date: 2011-01-19
SHENZHEN SINEXCEL ELECTRIC
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Depend on Figure 4 It can be seen that near the zero-crossing point of the inverter output voltage, because the switching frequency of the inverter is too low, the inductor current ripple of the inverter flows directly into the load, causing the output current to be distorted near the zero-crossing point of the inverter voltage.
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[0047] At any moment, the three-level inverter can send out +U bus , 0, -U bus One of three levels. According to Equation (2) and Equation (3) in the background technology section, it can be known that the switching frequency of the inverter is too low near the zero-crossing point of the inverter output voltage, because when the inverter outputs 0 level, the output voltage is very low. Small, the rate of change of the inverter inductor current is too small, resulting in low switching frequency of the inverter. One way to solve this problem is to not allow the three-level inverter to output 0 level near the zero-crossing point of the inverter output voltage. The inverter outputs +U through bus and -U bus Two levels are used to control the current fluctuation within the hysteresis bandwidth. At this time, the three-level inverter is used as a two-level inverter.
[0048] Figure 5 Shown is a simplified topological diagram of a three-phase two-level inverter.
[0049] ref...
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The invention relates to a control method of three-level inverters, comprising the following steps: within a first period of time of each cycle of output voltage Ua, leading the inverter to work in a two-level operating state; and within a second period of time of each cycle of the output voltage Ua, leading the inverter to work in a three-level operating state. The first period of time refers tothe period when an absolute value of the output value Ua of the inverter is smaller than a preset scale of a peak value of the output value Ua, while the second period of time refers to the period when an absolute value of the output voltage Ua of the inverter is larger than the preset scale of the peak value of the output voltage Ua. The control method of the three-level inverters leads the three-level inverters unlikely to output zero levels and the three-level inverters work under a two-level state if necessary, thus solving the problem of overlarge frequency ranges of the ripple current caused by the application of hysteretic current control technology in the three-level inverters.
Description
technical field [0001] The present invention relates to a control method of an inverter, more specifically, to a control method of a three-level inverter. Background technique [0002] The hysteresis current controller is a current controller that uses the instantaneous value comparison method. figure 1 (a) shows the schematic diagram of the current hysteresis controller. Its basic working principle is to control the corresponding IGBT on and off according to the direction of the current error, so that the controlled current is limited within a given error range. Such as figure 1 (b) shown. In the figure, i L * Given for the inductor current, i L is the inductor current, H is the hysteresis width, t on is the rise time of the inductor current, t off is the time for the inductor current to decrease. Depend on figure 1 (b) It can be seen that the switching period of the hysteresis current controller is T=t on +t off . When the inductor current is less than i L *...
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IPC IPC(8): H02M7/48
Inventor 冼成瑜魏晓亮
Owner SHENZHEN SINEXCEL ELECTRIC