Current Estimating Device Gain Correction for Power Converter
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Solution Overview
Problem
Existing power converter systems face inaccuracies in estimating power source current due to variations in voltage detection circuit components and temperature characteristics, leading to errors in inverter control, especially when using across voltage of a reactor for estimation.
Innovation Solution
A power converter system that includes a voltage detection circuit with gain correction coefficients to accurately estimate power source current by multiplying detection results from a voltage divider circuit, ensuring the estimated current matches the actual current flowing through the capacitor, thereby correcting for individual component variations and temperature effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current detection sensor is used to detect power source current, then measurement precision is improved, but device complexity and cost increase due to additional components and arrangement space
Solution Approach 1:
The patent extracts the current detection function from the traditional current sensor approach and relocates it to the existing voltage detection circuit. By utilizing the voltage detection circuit that already exists for other purposes, the patent eliminates the need for separate current detection sensors while maintaining measurement capability through voltage-to-current calculation relationships.
Solution Approach 2:
The voltage detection circuit is designed to serve multiple functions: it detects both voltage signals for power source current estimation and provides signals for other control purposes. This multi-functional approach allows the same circuit components to be used for current detection without adding dedicated current sensor components, thereby reducing overall device complexity.
2Measurement precision
If a current detection circuit with shunt resistance and operational amplifier is used, then measurement precision is improved, but device complexity and cost increase due to larger number of components
Solution Approach 1:
The patent extracts the essential detection function from the complex current detection circuit and implements it through the simpler voltage detection circuit. By removing unnecessary components like shunt resistances and operational amplifiers, the patent achieves current detection using only the voltage detection circuitry already present in the system.
Solution Approach 2:
Instead of directly measuring current with complex circuits, the patent copies the voltage detection approach and applies it to current estimation by measuring voltage and calculating equivalent current values. This copying of the voltage measurement method to current measurement eliminates the need for complex direct current sensing components.
3Device complexity
If across voltage of reactor is detected without gain correction to simplify the circuit, then device complexity is reduced, but measurement precision deteriorates due to component variations and temperature characteristics
Solution Approach 1:
The patent applies gain correction coefficients to the voltage detection results before using them for current estimation. This preliminary correction action compensates for component variations and temperature effects in advance, ensuring accurate measurements without requiring complex circuit modifications. The correction is performed through calculation rather than hardware changes.
Solution Approach 2:
The patent changes the parameter of voltage detection results by applying gain correction coefficients to compensate for component variations. Instead of modifying the physical circuit components, the patent adjusts the electrical parameters (voltage values) through mathematical correction, maintaining circuit simplicity while improving measurement precision.
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 allows for accurate power source current estimation using a simple voltage detection circuit without current sensors, improving inverter control and reducing harmonics generation.
Implementation Method 1
a voltage detection circuit detecting voltages correlating with a power source voltage of the AC power source
Data Source
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AI summary
The voltage detection circuit (33) is a voltage divider circuit including a plurality of resistances (34a to 34c and 35a to 35c) and detects voltages (Vac1, Vac2) correlating with a power source voltage (Vin) of the AC power source (91). The calculation unit (40) obtains the across voltage (VL) of the reactor (29) using detection results (Vac1, Vac2) of the voltage detection circuit (33), and estimates a power source current (Iin) based on the across voltage (VL). The calculation unit (40) corrects gains of the detection results (Vac1, Vac2) so that a value correlating with an average value per predetermined time period of the estimated power source current (Iin) matches a value correlating with an average value per the predetermined time period of a current (Iinv) downstream of the capacitor (26), and obtains the across voltage (VL) using the detection results (Vac1, Vac2).