Inverter Harmonic Voltage Injection Reduces DC Pulsation
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Solution Overview
Problem
High voltage inverters experience significant DC line voltage pulsation due to AC components in input and output power, leading to increased capacitance requirements, system volume, and cost, as well as reduced reliability.
Innovation Solution
The implementation of an inverter device with a converter unit, capacitor unit, and inverter unit, controlled by a converter controller and inverter controller, which includes an input line harmonic voltage generator and output line harmonic voltage generator to increase the pulsating power frequency, thereby reducing the DC line voltage pulsation and capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional DC line voltage control is used, then the inverter can operate with standard capacitor sizing, but the DC line voltage pulsation increases system volume and cost while reducing reliability
Solution Approach 1:
The patent introduces harmonic voltage components with specific frequencies (multiples of the fundamental frequency) into the converter control system. By changing the frequency parameters of the control voltage and injecting harmonic components at predetermined frequencies, the patent modifies the pulsation characteristics of the DC line voltage, shifting the pulsation frequency to values where the capacitor impedance is lower, thereby reducing the required capacitance value and volume.
Solution Approach 2:
The patent employs dynamic voltage injection where the harmonic voltage magnitude and frequency are adjusted based on operating conditions. The converter controller dynamically generates additional power with frequencies that are predetermined multiples of the fundamental frequency, adapting the control strategy to minimize DC line voltage pulsation across varying load and input conditions, thereby optimizing capacitor sizing dynamically.
2Stability of the object's composition
If higher capacitance is used to reduce DC line voltage pulsation, then voltage stability improves, but system volume and cost increase
Solution Approach 1:
Instead of increasing capacitance quantity, the patent changes the frequency parameters of the DC line voltage pulsation by injecting harmonic components. By transforming the pulsation frequency to higher values (predetermined multiples of fundamental frequency), the system achieves voltage stability with significantly reduced capacitance quantity, as capacitor impedance increases with frequency, allowing smaller capacitors to achieve the same filtering effect.
Solution Approach 2:
The patent introduces an intermediary harmonic voltage signal as a mediator between the converter and the DC line capacitor. This intermediary signal with specific frequency characteristics modifies the interaction between the converter and capacitor, allowing the system to achieve voltage stability without requiring large capacitance values. The harmonic injection acts as a bridge that transforms the voltage pulsation characteristics.
3Ease of manufacture
If standard converter control is used, then the system design is simple, but DC line voltage pulsation increases leading to larger capacitors and higher costs
Solution Approach 1:
The patent modifies the converter control parameters by injecting harmonic voltage components with predetermined frequencies (multiples of fundamental frequency). This parameter change in the control strategy transforms the DC line voltage pulsation characteristics, reducing the required capacitor volume without significantly complicating the manufacturing process. The control modification is implemented through standard power electronic control techniques.
Data Source
AI summary
An inverter device may include a converter unit configured to receive single phase AC power to output DC power; a capacitor unit configured to absorb the DC power; an inverter unit configured to synthesize the absorbed DC power to output the drive power of a load; and a converter controller configured to control the converter unit based on the AC power and the output DC power of the converter unit, wherein the converter controller includes a converter gate signal generator configured to control a plurality of gates contained in the converter unit; and an input line harmonic voltage generator configured to output converter additional power having a predetermined multiple of the frequency of the fundamental frequency component of the AC power with the same size as that of the fundamental frequency component of the AC power to an adder connected to the input side of the converter gate signal generator.