Grid-Connected Power Converter Control Using Voltage Observer
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Solution Overview
Problem
Grid-connected power converter systems face challenges in accurately estimating grid voltage without sensors, which are prone to noise and failure, affecting system reliability and efficiency.
Innovation Solution
The system estimates a d-axis grid voltage and q-axis grid voltage using modified current and voltage inputs, along with filter inductive reactance, and an observer q-axis grid voltage, eliminating the need for grid voltage sensors by generating gate control signals for efficient power conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If grid voltage sensors are used to measure grid voltage, then measurement accuracy is improved, but system reliability deteriorates due to sensor noise and failure
Solution Approach 1:
The patent extracts the voltage measurement function from physical sensors and implements it through mathematical estimation using current measurements and system parameters. The grid voltage is calculated as v_grid = L * di/dt + R * i + v_dc, removing the vulnerable sensor component while maintaining measurement capability through algebraic relationships in the circuit model.
Solution Approach 2:
The patent introduces an intermediary mathematical model that relates grid voltage to measurable quantities (current and its derivative) through the known circuit parameters (inductance L and resistance R). This intermediary relationship allows indirect measurement of grid voltage without direct sensor contact, eliminating sensor-related reliability issues.
2Difficulty of detecting and measuring
If grid voltage sensors are installed for voltage detection, then voltage detection capability is improved, but device complexity increases
Solution Approach 1:
The patent makes the existing current measurement system serve multiple functions: it simultaneously provides current control information and enables grid voltage estimation. The same current sensors and processing circuitry used for power factor correction and current control are also used to calculate grid voltage, eliminating the need for separate voltage sensing hardware.
Solution Approach 2:
The system uses its own operational parameters (current measurements and circuit characteristics) to determine grid voltage without external sensing equipment. The power converter system essentially measures its own impact on the grid through current measurements and back-calculates the grid voltage from this information.
Data Source
AI summary
For grid-connected power converter control, a method estimates a d-axis grid voltage from a d-axis reference current modified with a d-axis current and a q-axis current modified with a filter inductive reactance. The method generates a q-axis current error from a direct current (DC) voltage input and a DC bus voltage. The method estimates an observer q-axis grid voltage from a q-axis voltage output. The q-axis grid voltage observer estimates the q-axis grid voltage in a direct/quadrature (dq) reference frame equivalent to an ABC to DQ reference frame transform. The method determines a d-axis voltage output as a function of a d-axis current error and a q-axis current modified with a filter inductive reactance. The method determines a q-axis voltage output as a sum of the q-axis current controller output and the observer q-axis grid voltage.