Three-Phase Inverter Topology for Sinusoidal Output Without Filters
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Solution Overview
Problem
Existing three-phase inverters with non-sinusoidal PWM output voltage cause overvoltages, leading to motor burnout, harmonic distortions, and electromagnetic interference, which result in premature failures, increased temperature, and reduced motor life.
Innovation Solution
A three-phase frequency inverter with sinusoidal output voltage, no passive output filters, and the ability to connect ECD inverters in parallel, featuring a strategic arrangement of diodes, capacitors, inductors, and semiconductor switches, along with closed-loop PWM control with hysteresis, to produce low total harmonic distortion and prevent overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-sinusoidal PWM voltage output is used, then control and efficiency are improved, but overvoltages occur causing motor burnout and reliability deteriorates
Solution Approach 1:
The patent introduces an intermediary circuit between the inverter and motor consisting of series-connected capacitors and anti-parallel diodes. This intermediary structure filters the non-sinusoidal PWM voltage, preventing overvoltages from reaching the motor while maintaining the efficiency benefits of PWM control. The capacitors smooth voltage fluctuations and the diodes prevent reverse current flow, thereby protecting the motor.
Solution Approach 2:
The inverter output circuit is segmented into multiple functional components: switching elements for PWM generation, series capacitors for voltage smoothing, and anti-parallel diodes for current direction control. This segmentation allows each component to perform its specific function optimally, achieving both efficient control and motor protection.
2Object-generated harmful factors
If passive filters are added to minimize PWM effects, then harmonic distortion is reduced, but device complexity and cost increase
Solution Approach 1:
The patent extracts only the essential filtering elements (series capacitors and anti-parallel diodes) needed to mitigate PWM effects, rather than implementing complete passive LC filters. This selective extraction reduces component count and circuit complexity while still effectively minimizing harmonic distortion and protecting the motor.
Solution Approach 2:
The inverter's switching elements and basic circuit components are made to serve dual functions: the capacitors and diodes not only filter harmonics but also protect against overvoltages and prevent motor burnout. This self-service approach eliminates the need for separate protection circuits, reducing overall system complexity.
3Reliability
If robust motors or cable changes are implemented to withstand overvoltage, then motor reliability is improved, but cost and logistics complexity increase
Solution Approach 1:
Instead of making the motor more robust to withstand overvoltages, the patent inverts the approach by protecting the motor from overvoltages in the first place. The series capacitors and anti-parallel diodes prevent overvoltage conditions, allowing standard motors to be used without requiring robust designs or special cable specifications.
4Power
If inverters are connected in parallel to supply high-power motors, then power capacity is increased, but resonances and difficulty in adjustment occur
Solution Approach 1:
The patent makes each inverter unit homogeneous by incorporating identical series capacitor and anti-parallel diode configurations in parallel connections. This homogeneity ensures that all inverters operate with the same electrical characteristics, eliminating resonance issues and simplifying adjustment. Each unit can be independently configured and then connected in parallel without requiring complex synchronization or tuning.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides efficient and reliable power to motors and loads, reducing the risk of motor burnout, harmonic-related stress, and electromagnetic interference, while enabling parallel operation of inverters and minimizing energy losses.
Implementation Method 1
The use of non-sinusoidal three-phase inverters in industrial processes introduces a significant layer of complexity into electrical systems. These inverters with their PWM pulse voltage output offer advantages in terms of control and efficiency
Implementation Method 2
There are also inverters with non-sinusoidal PWM output that have a passive filter at their output, which tries to minimize the effects of the PWM output on the power supply to the loads, filtering out unwanted harmonics and delivering a voltage close to sinusoidal
Implementation Method 3
six inductors (L1, L2, L3, L4, L5, L6); nine diodes (D1, D2, D3, D4, D5, D6, D7, D8, D9); three depolarized capacitors (C1, C2, C3)
Implementation Method 4
three depolarized capacitors (C1, C2, C3)
Implementation Method 5
closed-loop PWM control with hysteresis, to produce low total harmonic distortion and prevent overshoot
Data Source
AI summary
The present invention relates to an electronic arrangement of a three-phase frequency inverter with sinusoidal output and variable frequency that output voltage with low total harmonic distortion, absence of overshoot in the output voltage for any load variation and thus with its precursor, and does not require the use of passive output filters. Put another way, the innovation involves topology providing sinusoidal output voltage, eliminating the need for passive output filters and mitigating problems such as burning of the motor related to overvoltages resulting from conventional PWM switching, premature bearing failures, helps reduce excessive vibrations and temperature increases caused by harmonics, has the ability to supply unbalanced loads, reduces irradiated and conducted noise-EMI, mainly in the feeders (cables) that feed the motors, among other benefits.