RU2002112508A - Multilevel voltage inverter and method of its control - Google Patents

Claims (9)

1. A voltage inverter and a method for controlling it, comprising first and second terminals for connecting to the positive and negative terminals of a power source, respectively; n series-connected capacitors, where n> 1, each of which has positive and negative terminals, with the positive terminal of the first capacitor connected to the first terminal of the power source, the negative terminal of the first capacitor connected to the positive terminal of the second capacitor, forming the first midpoint of the capacitors, similarly connected the remaining capacitors, forming a total of n-1 midpoints of the capacitors, and the negative terminal of the n-th capacitor is connected to the second terminal of the power source; and one or more phase circuits, each of which contains n series-connected upper keys and n series-connected lower keys, each of which has positive and negative terminals and a control terminal, and the positive terminal of the first upper switch is connected to the first terminal of the power source, its negative the output is connected to the positive output of the second upper key, forming the first midpoint of the upper keys, similarly the remaining upper keys are connected, forming a total of n-1 midpoints of the upper keys; the negative terminal of the first lower key is connected to the positive terminal of the second lower key, forming the first midpoint of the lower keys, similarly the remaining lower keys are connected, forming a total of n-1 midpoints of the lower keys, and the negative terminal of the nth lower key is connected to the second terminal of the power supply , n-1 upper diodes and n-1 lower diodes, each of which has an anode and a cathode, the anode of each k-th upper diode connected to the k-th midpoint of the capacitors, and the cathode of the k-th upper diode connected to the κ-th middle point of the upper beak whose, the cathode of each kth lower diode is connected to the kth midpoint of the capacitors, and the anode of each kth lower diode is connected to the kth midpoint of the lower keys, where k takes values from 1 to n-1, characterized in that the inverter is equipped with additional upper and lower reverse diodes, each of which has an anode and a cathode, and positive and negative terminals for connecting the load, and the cathode of the upper reverse diode is connected to the first terminal of the power source, and its anode and negative terminal for connecting the load are connected to P positively the lower terminal of the first key; the anode of the lower reverse diode is connected to the second terminal of the power source, and its cathode and the positive terminal for connecting the load are connected to the negative terminal of the nth upper key, while setting an integer m from the range from -n to n, as well as an integer i , which for negative values of m can take values from 0 to n + m, and for non-negative values, from m to n, and determining the number j by the formula j = n + mi, and in the case i> 0, opening i of the upper keys closest to the positive terminal to connect the load, and in the case j> 0, opening j lower keys closest to the negative terminal for connecting the load, apply voltage to the load, without taking into account the voltage drops on the keys and the voltage difference across the capacitors, equal to

moreover, negative values are possible only if the load current flows, where U is the voltage of the power source. 2. The voltage inverter and its control method according to claim 1, characterized in that when changing by more than 1, the upper switches commute in series, and open them, starting from the nearest switches to the positive terminal to connect the load, and close them in the reverse order , with a time pause between switching, and when j changes by more than 1, the lower keys also commute sequentially, and open them, starting from the nearest keys to the negative terminal to connect the load, and close them in the opposite order, with the time pa narrow between switching. 3. The voltage inverter and its control method according to claims 1 and 2, characterized in that during the initial opening of the keys for applying a positive voltage to the load in the absence of current in the load, the first n + 1 keys are opened simultaneously. 4. The voltage inverter and its control method according to claims 1 to 3, characterized in that they generate current in the phase winding of the jet induction motor using a current controller containing a phase current sensor and a 2n + 1-level comparator, so that when with the current of the kth level, from below or from above, it is checked whether the current state of the keys corresponds to the phase voltage level equal to

and otherwise, by switching the corresponding key or several keys, they provide such a correspondence, where k is the comparator level number, taking values from 1 to 2n + 1. 5. The voltage inverter and its control method according to claims 1 to 3, characterized in that they generate current in the phase winding of the jet induction motor using a current controller containing a phase current sensor and a two-level comparator, so that when the phase current values are lower the first level, and a phase voltage less than U, at certain intervals by switching the corresponding keys increase the magnitude of the phase voltage by

when the values of the phase current are greater than the second level, and the phase voltage greater than -U- is reduced, and when the values of the phase current are equal to or between the two levels, they are not changed. 6. The voltage inverter and its control method according to claims 1-5, characterized in that when switching the keys, various combinations alternate, ensuring the same voltage levels at the load, but from different capacitors. 7. The voltage inverter and its control method according to claims 1-6, characterized in that the voltage across each capacitor is measured, and during switching, a combination of keys is determined which ensures that the load is connected to the highest positive voltage or the lowest negative voltage modulo. 8. The voltage inverter and its control method according to claims 1-7, characterized in that for a long time there is no need to change the voltage on the load, forced switching is performed by changing combinations of switch states providing the same voltage levels on the load, but from different capacitors. 9. The voltage inverter and its control method according to claim 7, characterized in that when decreasing the positive or increasing modulus of the negative supply voltage by an amount greater than the permissible deviation, forced switching is performed by changing the combinations of switch states providing the same voltage levels on the load, but with different capacitors.