Matrix Converter Current Control With Feed Forward Phase Alignment
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Solution Overview
Problem
Traditional matrix converters operating in voltage control mode are limited to providing output voltages no greater than 86.6% of the input voltage without distortion due to the presence of input inductor-capacitor circuits, which restricts their ability to create short circuits between phases and risks damage to switching elements.
Innovation Solution
A matrix converter system operating in current control mode (CCM) that eliminates input inductor-capacitor circuits, utilizing internal inductances of a generator to generate reactive currents for charging output capacitors, allowing operation in a boost mode to achieve output voltages greater than the input voltage, and employs feed forward signals to adjust currents and minimize PWM controller saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a matrix converter operates in voltage control mode with sinusoidal PWM, then the control implementation is simpler, but the dynamic response is slower and distorted voltage waveforms occur during overmodulation
Solution Approach 1:
The patent changes the control parameter from voltage control mode to current control mode, and from sinusoidal PWM to space vector PWM. This parameter transformation enables both fast dynamic response and accurate control without the limitations of overmodulation, as the space vector modulation strategy optimizes the utilization of available voltage vectors to maintain waveform quality across all modulation levels.
2Speed
If space vector PWM is used in current control mode, then fast dynamic response and accurate control are achieved, but distorted current waveforms occur during overmodulation
Solution Approach 1:
The patent implements a feedback mechanism where the actual output currents are measured and fed back to the controller. The controller compares the actual currents with the reference currents and adjusts the switching signals accordingly. This closed-loop feedback ensures that current waveform accuracy is maintained even during overmodulation conditions by continuously correcting deviations.
Solution Approach 2:
The patent employs dynamic current control where the modulation strategy adapts in real-time based on the operating conditions. During overmodulation, the controller dynamically adjusts the switching patterns and modulation depth to maintain current waveform quality, transitioning smoothly between different control regions to prevent distortion while preserving fast dynamic response.
3Device complexity
If the angular position of the voltage output vector is not adjusted, then the control system is simpler, but the system cannot track the variable frequency reference signals accurately
Solution Approach 1:
The patent calculates the required angular position adjustment of the voltage output vector in advance based on the reference frequency and the phase difference between input and output vectors. This preliminary calculation of the adjustment amount allows the system to proactively compensate for frequency variations, ensuring accurate tracking without adding complex real-time adjustment mechanisms.
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3B
AI summary
A matrix converter system (10) having a current control mode operation is provided. The system includes a matrix converter (22) having a switching matrix (S). The matrix converter is coupled at its low-voltage side to a generator (416) and at its output load side to a load (412). A controller (26) having a pulse width modulation (PWM) control circuit is configured to control the matrix converter via its switching matrix to increase energy within the internal inductances of the generator when the switching matrix causes a short circuit. A feed forward calculator (419) is configured to calculate a feed forward output phase angle. The feed forward output phase angle is an estimation of an angle between an output current vector and an output voltage vector that represent feedback signals of current and voltage output by the matrix converter. The angular position of the voltage output vector is adjusted as a function of the feed forward output phase angle to align angular position or phase angle of the voltage output vector that represents the voltage output with a selected angular position or phase angle.