Adaptive Dead-Time Control in Power Converters for Stable Hysteresis Current

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Solution Overview

Problem

In hysteresis current control methods for power electronics converters, dead time introduces disturbances that cause the inductance current to exceed the defined hysteresis band, leading to frequency fluctuations and instability, as existing compensation techniques are complex and costly, with many components increasing hardware costs and reducing reliability.

Innovation Solution

A dead time control method that calculates the hysteresis band adaptively using digital values from an ADC, generating auxiliary control signals to manage the application of dead time between upper and lower switches, ensuring the current remains within the band by recalculating the band value at each sampling time and applying dead time only when necessary.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If dead time is set between drive signals to prevent short-circuit, then element safety is improved, but current control precision deteriorates causing current to exceed hysteresis band

Engineering Contradiction:

Improveelement safetyVSAvoidcurrent control precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies preliminary anti-action by predicting the current value at the end of dead time period using the measured voltage and current slopes. This prediction allows the hysteresis band to be adjusted in advance to compensate for the dead time effect, preventing current from exceeding the band while maintaining the necessary dead time for element safety.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The patent performs preliminary action by calculating and storing the voltage and current slopes before dead time occurs. These pre-calculated slope values are then used during dead time compensation to determine the predicted current value, enabling accurate compensation without adding complex real-time calculation requirements during the dead time period.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If complex dead time compensation techniques are used, then current control precision is improved, but device complexity and hardware cost increase

Engineering Contradiction:

Improvecurrent control precisionVSAvoidhardware complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies self-service by using the inverter's own measured voltage and current values, along with their calculated slopes, to perform dead time compensation. This eliminates the need for external complex compensation circuits or additional sensors, as the system uses its own operational data to compensate for dead time effects.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces complex mechanical or analog compensation circuits with a digital calculation approach. By using microprocessor-based slope calculation and prediction algorithms, the system achieves accurate dead time compensation without requiring complex analog circuitry, reducing hardware complexity while maintaining precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Stability of the object's composition

If dead time is applied to compensate for current distortion, then current control stability is improved, but switching frequency varies causing frequency instability

Engineering Contradiction:

Improvecurrent control stabilityVSAvoidswitching frequency

Core Design Contradiction:

Stability of the object's compositionVSSpeed

Solution Approach 1:

The patent applies dynamics by making the hysteresis band variable rather than fixed. The band width is dynamically adjusted based on the predicted current value that accounts for dead time effects. This dynamic adjustment maintains current control stability while allowing the switching frequency to remain consistent, as the compensation is seamlessly integrated into the control loop.

Inventive Principle:

Principle #15Dynamics

4Ease of operation

If hysteresis band is fixed, then control simplicity is improved, but current remains outside band during dead time causing control disruption

Engineering Contradiction:

Improvecontrol simplicityVSAvoidcurrent control accuracy

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by modifying the hysteresis band width parameter dynamically. Instead of using a fixed band, the band is adjusted based on the predicted current value that compensates for dead time. This maintains the simplicity of the hysteresis control structure while improving current control accuracy through parameter adaptation.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11757376B2Dead-time control method for power electronics converters and a circuit for the application of this method

Publication Date: 2023.09.12 YILDIZ TEKNIK UNIVSI

AI summary

A dead time control method (100) comprising the steps of: converting the DC link voltage, output current and output voltage to digital values with an ADC (Analog to Digital converter) (102); calculating the hysteresis band for adaptive hysteresis current control using the values read by the ADC and updating the band value via recalculating it at each sampling time (103); calculating the IrefH and IrefL values using the hysteresis band and Iref (103a); generating the PWM signal by hysteresis current control (104), generating two auxiliary control signals as VP, VN (105); in the region where VP=1 and VN=0, applying of the drive signal of T1 without setting dead time wherein T1 is the conduction duration of an upper switch, and not applying the drive signal of T2 wherein T2 is the turn off duration of said upper switch and is the conduction duration of a lower switch (106).