Tertiary Harmonic Wave Amplitude Control for Inverter Efficiency
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Solution Overview
Problem
The existing PWM control method for three-phase inverters limits the voltage utilization factor and conversion efficiency due to the amplitude constraints of the tertiary harmonic wave, which does not optimize the inverter's performance.
Innovation Solution
A power conversion device that includes a three-phase voltage inverter, a two-phase/three-phase converter, a tertiary harmonic wave generator, an adder, and a PWM controller, with a tertiary harmonic wave amplitude determining unit that adjusts the amplitude of the tertiary harmonic wave signal to minimize power loss and enhance conversion efficiency based on voltage amplitude and output power factor commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the amplitude of the tertiary harmonic wave is set to about 1/6 of the voltage command signal to enhance the voltage utilization factor, then the voltage utilization factor is improved, but the conversion efficiency of the inverter is not optimized
Solution Approach 1:
The patent applies dynamics by making the amplitude of the tertiary harmonic wave adjustable rather than fixed. The control device dynamically changes the amplitude according to operating conditions (output power, power factor) to optimize both voltage utilization factor and conversion efficiency simultaneously, resolving the contradiction between these two parameters.
Solution Approach 2:
The patent changes the parameter of tertiary harmonic wave amplitude from a fixed value (1/6) to a variable parameter that can be adjusted based on operating conditions. By optimizing this parameter according to output power and power factor, the system achieves both high voltage utilization factor and high conversion efficiency.
2Power
If the amplitude of the tertiary harmonic wave is increased to reduce peak values of the voltage command signal, then the maximum value of the fundamental wave component of the output voltage is increased, but the power loss in switching elements increases
Solution Approach 1:
The patent dynamically adjusts the tertiary harmonic wave amplitude based on operating conditions. At different output power levels and power factors, the optimal amplitude varies, and the system adapts accordingly to minimize power loss while maintaining high output voltage amplitude.
Solution Approach 2:
The patent optimizes the amplitude parameter of the tertiary harmonic wave by considering its impact on both output voltage and power loss. Through calculation and optimization, the system determines the optimal amplitude that balances output performance with power loss minimization.
Data Source
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AI summary
The present invention has an object to provide a power conversion device capable of enhancing the conversion efficiency of a three-phase voltage inverter. A power conversion device (1) according to an embodiment of the present disclosure includes a three-phase voltage inverter (5), a two-phase/three-phase converter (11), a tertiary harmonic wave generator (12), an adder (13), a PWM controller (14), and a tertiary harmonic wave amplitude determining unit (15a). The tertiary harmonic wave generator (12) generates a sinusoidal tertiary harmonic wave signal (Vh) synchronized with three-phase voltage command signals (Vu, Vv, Vw) and having a frequency which is three times as high as that of the three-phase voltage command signal. Furthermore, the tertiary harmonic wave generator (12) includes a tertiary harmonic wave amplitude determining unit for determining the amplitude of the tertiary harmonic wave signal Vh at which the power loss of a three-phase voltage inverter (5) is minimized, based on a voltage amplitude command value responding to two-phase voltage command signals (Vd, Vq) and an output power factor command value responding to an output request to a power system.