Motor Voltage Conversion Control Device for Pulsation Reduction
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Solution Overview
Problem
The existing motor voltage conversion control systems face instability due to pulsation in the input DC voltage caused by motor current pulsation, especially when the capacitance of the smoothing capacitor is reduced, leading to increased system losses and pulsation in the boosted DC high voltage, which affects the stability of boost control.
Innovation Solution
A motor voltage conversion control device that includes a sampling unit, a target voltage setting unit, a selection unit, and a control unit to sample and stabilize the input DC voltage by selecting the appropriate target voltage and adjusting the sampling timing based on the gate signal of the motor with the target voltage not selected as the system's target voltage, thereby reducing the pulsation and enhancing stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the capacitance of the smoothing capacitor is reduced to reduce cost and size, then the system cost and size are reduced, but the voltage pulsation increases causing instability in boost control
Solution Approach 1:
The patent applies preliminary action by predicting the input DC voltage value in advance based on the relationship between motor current pulsation and voltage pulsation. The prediction unit calculates the expected voltage drop caused by capacitor charge/discharge and predicts the input DC voltage before the sampling moment, allowing the control system to compensate for voltage pulsation effects and maintain stable boost control even with reduced capacitance
Solution Approach 2:
The patent implements feedback by using the predicted input DC voltage to adjust the sampling timing and control parameters. The prediction unit continuously monitors motor current and capacitor voltage relationships, and the control unit uses this feedback information to dynamically adjust the sampling moment, ensuring accurate voltage measurement despite pulsation effects from reduced capacitance
2Device complexity
If the sampling timing is not synchronized with voltage pulsation patterns, then the sampling system is simpler, but the sampled voltage deviates from expected value causing control instability
Solution Approach 1:
The patent determines the optimal sampling moment in advance by calculating when the voltage pulsation will occur based on motor current patterns. The prediction unit computes the timing when voltage sampling should occur to capture the expected voltage value, allowing the system to maintain measurement precision without complex real-time adjustment mechanisms
Solution Approach 2:
The patent makes the sampling timing dynamic by adjusting it based on varying motor operating conditions. The prediction unit continuously adapts the sampling moment according to changes in motor current and load conditions, ensuring that sampling always occurs at the optimal point regardless of operating state, thereby maintaining measurement accuracy without fixed complex timing circuits
3Object-affected harmful factors
If the carrier frequency is reduced to reduce switching noise, then the switching noise decreases, but the ON/OFF period increases causing larger pulse components on voltage
Solution Approach 1:
The patent uses feedback by continuously monitoring the relationship between motor current and capacitor voltage to determine the actual voltage pulsation pattern. The prediction unit uses this feedback to accurately predict input DC voltage under various carrier frequency conditions, allowing the system to maintain voltage stability even when carrier frequency is reduced and pulse components increase
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution allows for stable voltage conversion control by sampling the input DC voltage close to its expected value, reducing system losses and capacitance requirements, thus minimizing the size and cost of the system.
Implementation Method 1
A smoothing capacitor is provided between the boost converter and the inverter and a voltage sensor detects the voltage (DC high voltage boosted by the boost converter) between both ends of the smoothing capacitor
Data Source
AI summary
A control device performs voltage conversion control on a voltage conversion circuit between a power supply and motor control circuits which control a plurality of motors. The control device includes sampling units for sampling a DC voltage after voltage conversion, target voltage setting units for setting target voltages VHT1 and VHT2 of the plurality of motors, selection unit for selecting a target voltage VHT to be converted by the voltage conversion circuit from a plurality of target voltages VHT1 and VHT2, generating unit for generating a sampling timing TS on the basis of a gate signal GS1 or GS2 of one of the motors with the target voltage which has not been selected, and control unit for performing the voltage conversion control using the DC voltage sampled by the sampling units at the sampling timing TS in response to each sampling timing request DS in the voltage conversion control.