Voltage Conversion Control Device for Multi-Motor Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In vehicle systems with multiple motors, reducing the capacitance of smoothing capacitors is necessary for cost and size reduction, but this leads to increased pulsation in DC high voltage due to insufficient smoothing ability, especially when the carrier frequency of inverter control is lowered, causing instability in voltage boost control.
Innovation Solution
A voltage conversion control device that samples the input DC voltage at the timing of the crest or trough of the carrier signal for each motor, allowing for stable voltage conversion control by selecting the target voltage based on the carrier signal of the motor with the largest pulsation effect, thereby reducing the difference between expected and actual voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the capacitance of the smoothing capacitor is reduced to lower cost and size, then the capacitance value decreases, but the smoothing ability becomes insufficient causing large voltage fluctuation and pulsation in the DC high voltage
Solution Approach 1:
The patent applies preliminary action by predicting the DC high voltage value in advance based on the carrier signal phase information before actual voltage measurement. The control device calculates expected voltage values at different carrier signal phases and uses these predictions to determine optimal sampling timing, allowing the system to compensate for voltage pulsation effects before they impact control accuracy. This enables stable voltage boost control even with reduced capacitor capacitance.
Solution Approach 2:
The patent implements feedback by continuously monitoring the actual DC high voltage and comparing it with predicted values based on carrier signal phase. The control device adjusts the sampling timing of the voltage sensor based on feedback from the carrier signal phase information, creating a closed-loop system that compensates for voltage pulsation. This feedback mechanism allows the system to maintain stable control despite using a smaller smoothing capacitor.
2Loss of energy
If the carrier frequency of inverter control is lowered to reduce switching noise, then the switching frequency decreases, but the pulsation component increases and is superimposed on the DC high voltage causing instability
Solution Approach 1:
The patent uses preliminary action by determining the optimal voltage sampling timing in advance based on the carrier signal phase before actual voltage measurement occurs. The control device predicts where voltage pulsation will be minimal by analyzing the carrier signal phase relationship, and sets the sampling timing accordingly. This allows the system to avoid sampling during high-pulsation periods even when operating at lower carrier frequencies.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the voltage sampling timing parameter based on the carrier signal phase. Instead of using fixed sampling timing, the system varies the sampling phase angle according to the detected carrier signal phase, shifting the sampling point to coincide with moments of minimal voltage pulsation. This parameter adjustment enables stable control across different carrier frequencies.
3Power
If the target voltage is set high to meet motor driving requirements, then the output voltage increases, but the voltage difference between DC high voltage and motor induced voltage increases causing larger pulsation component
Solution Approach 1:
The patent applies preliminary action by predicting the DC high voltage value based on the carrier signal phase before performing voltage boost control. The control device calculates expected voltage values at different carrier phases in advance, allowing it to determine the optimal sampling timing that minimizes pulsation effects. This prediction capability enables accurate voltage control even when operating at high target voltages that would otherwise generate large pulsation components.
Solution Approach 2:
The patent implements feedback by using the carrier signal phase information to continuously adjust the voltage sampling timing. The system monitors the relationship between carrier phase and voltage pulsation, and dynamically adjusts sampling timing to minimize the impact of pulsation on control accuracy. This feedback mechanism allows the system to maintain stable control at high output voltages by compensating for pulsation effects in real-time.
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
This approach enables stable voltage conversion control even with pulsation in the input DC voltage, allowing for reduced capacitance and cost-effective design of multi-motor systems by minimizing the pulsation component on the motor current.
Implementation Method 1
a voltage (a DC high voltage after boosting by the voltage boost converter) across both ends of the smoothing capacitor is detected by a voltage sensor
Implementation Method 2
a voltage conversion circuit between a motor control circuit controlling a plurality of motors and a power supply configured to convert a DC voltage of the power supply to an input DC voltage necessary for driving the motor
Data Source
AI summary
Disclosed is a control device which performs voltage conversion control for a voltage conversion circuit between motor control circuits which control a plurality of motors and a power supply. The control device includes sampling means for sampling a DC voltage after voltage conversion, target voltage setting means for setting target voltages of the plurality of motors, selection means for selecting a target voltage to be converted by the voltage conversion circuit from among the plurality of target voltages, generation means for generating a sampling timing on the basis of a carrier signal of one of the motors having the unselected target voltage, and control means for performing voltage conversion control using the DC voltage sampled by the sampling means in response to the sampling timing for each sampling timing request of voltage conversion control.