Power Converter State Detection via DC Link Voltage Sampling
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Solution Overview
Problem
Current power converting apparatus configurations require multiple current and voltage detection circuits, leading to complexity and reduced accuracy in monitoring power source malfunctions, particularly when an inverter and PWM converter are connected in series.
Innovation Solution
A direct power converting apparatus with no power storage means between the converter and inverter, utilizing high-arm and low-arm side switching elements and synchronized operation of current-source and voltage-source converters to detect line voltages and currents with reduced circuit complexity and improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple current and voltage detection circuits are used to monitor power source malfunctions, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple detection functions into a single detection circuit that simultaneously measures both current and voltage. The detection circuit uses the DC voltage between power supply lines and switching element conduction patterns to derive both current information and voltage amplitude information, eliminating the need for separate detection circuits for each parameter.
Solution Approach 2:
The detection circuit is designed to perform multiple functions: it detects DC current through voltage measurement across the DC link, detects input voltage amplitude through DC voltage sampling at specific switching intervals, and monitors power source malfunctions. This multi-functional approach reduces the overall number of detection circuits required.
2Reliability
If separate current detection circuits are provided for both PWM converter and inverter, then current monitoring capability is improved, but device complexity increases
Solution Approach 1:
The patent merges current detection for both the PWM converter and inverter into a single detection mechanism. By measuring the DC voltage across the DC link and combining it with switching element conduction pattern information, the system derives current information for both converters without requiring separate current detection circuits.
Solution Approach 2:
The DC link voltage serves as an intermediary measurement that provides information about both the PWM converter and inverter currents. By sampling this intermediate voltage at specific switching intervals and combining it with switching state information, the system obtains current data for both converters through a single measurement point.
3Ease of operation
If DC voltage is detected to monitor power source amplitude, then voltage monitoring is achieved, but detection accuracy is reduced
Solution Approach 1:
The patent performs preliminary sampling of the DC voltage at specific switching intervals before using it for amplitude detection. By sampling the voltage at predetermined timing related to the switching cycle and combining it with conduction pattern information, the system prepares accurate voltage data in advance for subsequent amplitude calculation.
Solution Approach 2:
The system changes the parameter being measured from direct AC voltage to DC link voltage, which can be sampled more accurately. By detecting the DC voltage that results from rectified AC voltage and using switching interval information to relate it back to the input voltage amplitude, the system achieves higher detection accuracy through parameter transformation.
Data Source
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AI summary
The present invention is directed to a state quantity detection method for detecting a state quantity in a power converting apparatus with a simple configuration and with a high accuracy, and to the power converting apparatus. A current-source converter (20) includes high-arm side switching elements (Srp, Ssp, Stp) and low-arm side switching elements (Ssn, Srn, Stn). A voltage between the DC power supply lines (L1, L2) is detected as a line voltage of an input line, based on a conduction pattern of the high-arm side switching elements (Srp, Ssp, Stp) and the low-arm side switching elements (Srn, Ssn, Stn).