Power Conversion Device Frequency Update Prediction
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Solution Overview
Problem
General-purpose power conversion devices face challenges in updating frequency signals, particularly when the signal period extends, leading to delayed synchronization and difficulty in achieving motor control synchronization, especially when operating at low frequencies.
Innovation Solution
A power conversion device with a calculating unit that includes a period converting unit, a period calculating unit, and a control unit, which converts input signals into period signals, calculates the frequency, and outputs a command frequency by predicting the pulse train input before acquiring pulse edges, allowing for early updates in frequency even when the period signal is not acquirable for an extended period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the power conversion device waits to acquire the period signal before updating frequency, then the frequency update is accurate, but the update timing is delayed especially at low frequencies
Solution Approach 1:
The patent applies preliminary action by calculating the period length from the current pulse signal and using it to predict when the next pulse edge will occur. This allows the system to proactively prepare for the frequency update before the actual pulse edge arrives, rather than passively waiting for the pulse signal. The period calculation unit computes T = 1/f using the currently acquired frequency, and this predicted period information is used to anticipate the timing of the next pulse edge, enabling the control unit to update the frequency command in advance.
2Use of energy by moving object
If the device operates at very low frequencies (0.09 Hz or less), then energy consumption is reduced, but pulse arrival intervals extend to 10 seconds or more causing synchronization difficulties
Solution Approach 1:
The patent enables the control unit to update the frequency command value in advance based on the period length calculated from the current frequency. This preliminary update mechanism ensures that even when pulse intervals extend to 10 seconds or more at low frequencies like 0.09 Hz, the slave power conversion device maintains accurate synchronization with the master device without requiring continuous pulse arrivals.
Solution Approach 2:
The system dynamically adjusts its operation based on the acquired frequency. At low frequencies, the period calculation unit calculates a longer period T, and the control unit utilizes this extended time window to update the frequency command earlier, maintaining synchronization reliability across varying operational conditions including very low frequency modes.
Data Source
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AI summary
In a general-purpose power conversion device, there is a problem that, when a pulse signal period becomes longer, an edge interval becomes longer and a period of updating a command frequency is extended. In order to solve this problem, there is provided a power conversion device having an AC converting unit that performs power conversion and a calculating unit that controls the AC converting unit, in which the calculating unit includes a period converting unit that converts an input signal into a period signal, a period calculating unit that calculates an acquired frequency from the period signal, and a control unit that outputs an output command according to the acquired frequency, and in a case where the period signal is not acquirable during a period longer than the period of the period signal acquired from the period converting unit at a preceding time, the period calculating unit is configured to calculate a time period during which the period signal is not acquirable, and to output the time period as the acquired frequency.