Inverter Control Phase Lead Compensation for Motor Stability
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Solution Overview
Problem
Existing inverter control systems face instability due to a reduction in phase margin attributed to the inherent characteristics of motors, leading to an unstable control system.
Innovation Solution
The inverter control device calculates a phase lead amount based on phase compensation time and motor rotational velocity, compensating the phases to maintain a stable control system by adjusting the phase lead amount to counteract the inherent motor characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional inverter control is used without phase compensation, then the control structure is simple, but the phase margin reduces due to inherent motor characteristics causing system instability
Solution Approach 1:
The patent applies preliminary action by calculating and applying phase lead compensation in advance based on predicted motor speed. The phase lead amount is computed before the control cycle using the formula Δθ = ω × tpm, where ω is the predicted motor speed and tpm is the phase compensation time. This pre-calculation compensates for the inherent motor characteristics that would otherwise cause phase margin reduction and instability, while maintaining a relatively simple control structure.
2Reliability
If phase compensation is applied to stabilize the control system, then control stability improves, but the computational complexity increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the phase lead amount Δθ based on the predicted motor speed ω. The compensation time tpm is set as a fixed parameter, while the phase lead amount varies with operating conditions. This approach stabilizes the control system across different speed ranges without requiring complex adaptive algorithms, as the relationship Δθ = ω × tpm provides a straightforward computational method that adapts to changing motor characteristics.
Data Source
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Figure 3(a)~3(b)
AI summary
An inverter control device including: an inverter 6 configured to convert direct-current power inputted from a direct-current power supply into alternating-current power, and to supply the alternating-current power to a motor; a command value calculation unit (1, 2, 3) configured to calculate a command value of an alternating-current voltage outputted from the inverter 6, on the basis of a detection value of an alternating current; a phase compensation unit (16) configured to compensate for the phase of the command value or the phase of the detection value; an inverter control unit (4) configured to control the inverter 6 on the basis of any of the command value and the detection value compensated for by the phase compensation unit; and a motor rotational velocity detection unit (9, 14, 11) configured to detect a rotational velocity (ω) of a motor 8. The phase compensation unit (16) calculates a phase lead amount (Δθ) on the basis of the rotational velocity (ω) and the phase compensation time (tpm) set for obtaining a predetermined phase margin, and compensates for the phase based on an inherent characteristic of the motor in accordance with the phase lead amount (Δθ).