Electric Drive Control with Dead-Beat Voltage Limiter
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Solution Overview
Problem
Existing electric drive control methods face challenges in efficiently controlling stator current and torque in induction machines, often resulting in oscillations and overshooting due to limitations in voltage setting and feedback mechanisms.
Innovation Solution
A time-discrete control structure for an electric motor fed by a converter, incorporating a setpoint limiter and pilot control, which adjusts voltage to prevent voltage limit exceedance and incorporates a dead-beat controller with a time delay to achieve precise setpoint reaching without oscillations, using a limiter that suppresses feedback and oscillations by considering the motor's transfer function and control limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional flux controller structure is used to control the stator current, then the control structure can be implemented, but voltage setting limits are exceeded and oscillations occur
Solution Approach 1:
The patent applies preliminary action by introducing a pre-control mechanism that calculates and applies the necessary voltage change in advance based on the setpoint deviation. The pre-control variable V is computed as V = K * (I_setpoint - I_actual), where K is a proportionality factor. This preliminary voltage adjustment is applied before the main controller acts, allowing the system to reach the setpoint in exactly one time step without oscillations or overshooting, while respecting voltage limits.
Solution Approach 2:
The patent changes the control parameter from direct current control to voltage control with a pre-calculated voltage variable. By transforming the control approach to work with voltage settings rather than directly manipulating current, the system can respect voltage limits while achieving precise current control. The controller output variable U is transformed into a voltage setting that accounts for system parameters and limits.
2Productivity
If the setpoint is changed quickly to improve response time, then productivity increases, but overshooting and oscillations occur due to feedback mechanisms
Solution Approach 1:
The pre-control mechanism calculates the exact voltage adjustment needed to reach the new setpoint in one time step. When the setpoint changes, the pre-control variable V immediately reflects this change and applies the appropriate voltage adjustment, eliminating the need for gradual feedback-based adjustments. This allows rapid setpoint tracking without overshooting or oscillations.
Solution Approach 2:
The patent introduces a time delay element as an intermediary between the setpoint specification and the controller input. This delay element holds the setpoint value for one time step, allowing the pre-control mechanism to properly calculate and apply the voltage adjustment. This intermediary structure enables fast response while maintaining stability by coordinating the timing of setpoint changes with control actions.
3Reliability
If voltage setting limits are enforced to prevent hardware damage, then reliability improves, but the setpoint cannot be reached quickly due to control constraints
Solution Approach 1:
The patent transforms the control parameter to voltage settings that inherently respect hardware limits. The controller output variable U is converted into a voltage setting that accounts for maximum and minimum voltage limits. By working with voltage parameters rather than direct current commands, the system can enforce hardware protection while achieving rapid response through the pre-control mechanism.
Solution Approach 2:
The pre-control variable V is calculated in advance with full knowledge of the system state and voltage limits. This preliminary calculation ensures that the voltage adjustment needed to reach the setpoint is both optimal and within hardware limits. The controller applies this pre-calculated voltage setting directly, achieving the fastest possible response that respects hardware constraints.
Data Source
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AI summary
Drive and method, comprising an electric motor, powered by a converter, said converter comprising a time-discrete control structure, controlling the stator current of the electric motor by means of adjusting the motor supply voltage, wherein the motor current is recorded in a time-discrete manner and the control structure comprises a regulator, the actual value of which is a first current component of the current, the set value output of the regulator being fitted with at least one in-series set value limiter.