Three level neutral point clamped converter with improved voltage balancing
AssigneeRaytheon Company
InventorDavid C. Lewis
Life of this patent
Estimating the term…
Abstract
An NPC converter is controlled by estimating current flow during the short vector periods of a space vector modulation drive signal. The current estimation is used to close a first order inner current regulator loop that steers current to either the upper capacitor or the lower capacitor of a DC link. An outer voltage regulator measures the voltage imbalance across the capacitors and drives the inner current loop. By managing the associated duty cycle of each vector a bias current is formed that balances the capacitor voltages.
Claims18
A converter, comprising:
- a neutral point clamped (NPC) converter module comprising:
- a plurality of phase legs, each phase leg comprising a plurality of switches coupled in series with one another between a first node and a second node, each phase leg further comprising an AC node positioned between two adjacent switches;
- a current sensor coupled to each AC node and configured to measure an amount of current flowing into, or out of, each respective AC node;
- and
- a controller, coupled to the NPC converter module and the current sensor, configured to:
- generate a space vector pulse width modulated (SVPWM) signal to control a respective on/off condition of each of the plurality of switches as a function of:
- a short vector current signal generated as a function of a value of the current sensed at the respective AC nodes during short vector periods of the SVPWM signal;
- and
- a respective voltage differential between a first voltage on the first node and a second voltage on the second node, each with respect to a third node.
A method of operating a multi-level neutral point clamped converter comprising:
- measuring AC current flowing in the converter;
- generating a short vector current signal representing a component of the measured AC current during a short vector period of a space vector pulse width modulated (SVPWM) driving signal;
- measuring a voltage difference between respective voltages on each of two capacitors in a DC link portion of the converter;
- and
- modifying the SVPWM driving signal as a function of the generated short vector current signal and the measured voltage difference.
A non-transitory computer readable media comprising instructions stored thereon that, when executed by a processing apparatus, cause the processing apparatus to implement a method of operating a multi-level neutral point clamped converter, the method comprising:
- measuring AC current flowing in the converter;
- generating a short vector current signal representing a component of the measured AC current during a short vector period of a space vector pulse width modulated (SVPWM) driving signal;
- measuring a voltage difference between respective voltages on each of two capacitors in a DC link portion of the converter;
- and
- modifying the SVPWM driving signal as a function of the generated short vector current signal and the measured voltage difference.
Dependencies are inferred from the claim text.