AC-Side Chopper Bypass Circuit for Harmonic Suppression
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Solution Overview
Problem
Existing power conversion devices face challenges in suppressing harmonic current while maintaining low loss and simplicity, particularly due to the need for expensive DC switches and inefficiencies when bypassing chopper circuits.
Innovation Solution
A power conversion device configuration that includes a switch and reactor connected in parallel before the chopper circuit unit, with a control unit that stops switching when the switch is open, effectively suppressing harmonic current and reducing losses by using an AC switch and reactor in parallel with the rectifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a chopper circuit unit is bypassed with a relay to reduce loss, then loss is reduced, but the reactor connected between power supply and smoothing capacitor is also bypassed making it difficult to suppress harmonic current
Solution Approach 1:
The invention divides the bypass function into two separate components: a switch for bypassing the chopper circuit unit and a relay for bypassing the reactor. This segmentation allows independent control of each bypass function, enabling the chopper circuit to be bypassed for loss reduction while the reactor remains connected for harmonic current suppression.
Solution Approach 2:
The invention introduces an intermediary control mechanism where the control unit coordinates the switch and relay operations. The control unit acts as an intermediary that manages the bypassing process, ensuring that when the chopper circuit is bypassed, the reactor remains active to suppress harmonic current, thus resolving the contradiction between loss reduction and harmonic suppression.
2Ease of manufacture
If two DC switches are used to bypass the chopper circuit, then the chopper circuit can be bypassed, but the cost is high compared to using an AC switch
Solution Approach 1:
The invention changes the parameter of the switch from DC to AC type. By using an AC switch instead of DC switches, the system achieves the bypass function while reducing cost, as AC switches are generally more economical than DC switches. This parameter change resolves the contradiction between bypass capability and cost.
3Object-generated harmful factors
If the chopper circuit unit is always active to suppress harmonic current, then harmonic current is suppressed, but loss increases
Solution Approach 1:
The invention makes the chopper circuit bypass dynamic by introducing a controllable switch. The switch can be turned on or off based on operating conditions, allowing the system to dynamically switch between using the chopper circuit for harmonic suppression and bypassing it for loss reduction. This dynamic control resolves the contradiction between harmonic suppression and loss.
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
This configuration achieves low loss and effective harmonic current suppression with a simple setup, reducing costs and improving efficiency in motor drive control devices for applications like air conditioners and compressors.
Implementation Method 1
a reactor that is disposed on a side closer to the AC power supply than the chopper circuit unit
Implementation Method 2
a switch disposed on a side closer to the AC power supply than the chopper circuit unit; a reactor that is disposed on a side closer to the AC power supply than the chopper circuit unit, and is connected in parallel to the switch
Data Source
AI summary
A power conversion device is configured to have reactors and is configured to have chopper circuit units, connected in series, that chop the output of a rectifier configured to rectify an AC voltage from an AC power supply. The power conversion device includes: an AC switch disposed on a side closer to the AC power supply than the chopper circuit units; an AC reactor that is connected in parallel to the AC switch; and a switching control unit that stops the switching of the switching elements when the contact of the AC switch is open.