Variable frequency driving device of 3KV-10KV middle-high voltage multi-level three-phase AC motor

Abstract

The frequency conversion driving gear of the 3KV-10KV middle and high voltage multilevel three-phase alternating current motor belongs to the field of the high voltage converter technique. The main circuit is composed of the multi-winding assistant side phase shifting isolating transformer and several H bridge power units with the three levels of alternating-direct- alternating. The commutation part of every power unit is three-phase diode commutate with no controlling, the middle direct current tache connects with the capacitor parallelly and the inverted part is the three-level H bridge construction and adopts the diode clamp or the capacitor clamp three-level structure. The voltage of the unit clamping capacitor is controlled dynamicly. The main switch devices can choose the corresponding withstand voltage and current power semiconductor switch devices according to the difference of the grades of the output voltage and the current. Several groups of power unit output are in the form of Y after being connected in series. The controller takes the high performance digital signal microprocessor as the center to form the PWM control signal and dynamicly controls the balance of the voltage of the power unit clamping capacitor. It reduces the number of the assistant boarders of the phase shifting transformer and decreases the cost. The dynamic control policy adopted by the voltage of the clamping capacitor increases the performance.

Description

Technical field: [0001] The invention relates to a multi-level topology structure of power electronics, which belongs to a high-voltage variable-frequency drive device, in particular to a three-phase series structure with a voltage-type AC-DC-AC three-level H bridge as an independent power unit, and each three-level The clamp capacitor voltage of the unit adopts a dynamic control method. Background technique: [0002] The continuous growth of my country's economy will have a long-term demand for electricity. At the same time, 66% of my country's total power generation is consumed by electric motors, and more than half of them are used for various fans and pumps. By changing the rotational speed to adjust the flow and pressure, instead of the traditional windshield and valve adjustment method, it can save about 30% of electricity on average. In addition, the speed control drive can also improve the combustion of the boiler and save a lot of fuel. At present, the conventional ...

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Problems solved by technology

[0007] This kind of circuit also has great disadvantages when applied to medium and high voltages: high-voltage switching devices are used, and the output dv / dt is high. Generally, an output filter must be added, which increases the volume, cost and loss; the three-level structure is based on the current and future devices. Level, the output of 6KV cannot be achieved when the devices are not connected in series, and it can reach 6KV when the devices are connected in series, but there are inherent problems of switch synchronization and voltage equalization when large-capacity switching devices are connected in series, and the output still cannot reach 10KV

[0009] The disadvantage of this structure is also obvious: the higher the output voltage level, the more the number of power units in series. Generally, the output of 6KV is connected in series with 5-7 power units, and the output of 10KV is connected in series with 8-10 power units. The phase-shifting isolation transformer has many secondary windings, requiring 15 to 30 sets of secondary three-phase windings. Generally, the cost of the phase-shifting isolation transformer accounts for more than one-third of the system cost.

Therefore, the phase-shifting isolation transformer has a large volume, complex wiring, increased manufacturing difficulty, and a lot of cost increase, which has become a bottleneck

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