Bidirectional CLLC Circuit Smooth Direction Switching
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Solution Overview
Problem
The bidirectional resonant CLLC circuit lacks the capability for smooth switching of operation direction, limiting its application in scenarios requiring fast and stable switching, such as energy storage equipment scheduling and V2G technology, due to its reliance on frequency conversion control which is insufficient for reducing power transmission effectively.
Innovation Solution
A method combining frequency conversion control and phase shift control is implemented, allowing the bidirectional resonant CLLC circuit to switch operation directions by increasing switch frequency and adjusting phase angle differences between primary and secondary bridges, enabling smooth switching without additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If frequency conversion control is used in bidirectional resonant CLLC circuit, then the circuit can transmit power, but smooth switching of operation direction cannot be achieved
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The controller dynamically adjusts the switching frequency of the resonant circuit based on the desired power transmission level, enabling the circuit to operate efficiently across a wide range of power levels while achieving smooth bidirectional switching. This dynamic frequency adjustment resolves the contradiction by allowing the circuit to adapt its operating parameters in real-time.
Solution Approach 2:
The patent changes the key operating parameter (switching frequency) to resolve the contradiction. By varying the switching frequency within a specific range, the circuit can control power transmission continuously and achieve smooth operation direction switching. The parameter change approach allows the circuit to transition between different operating states without abrupt changes, thereby enabling both power transmission and smooth directional switching.
2Power
If switching frequency is increased to reduce power transmission, then power can be reduced to small extent, but operation switch frequency is limited and smooth switching cannot be achieved
Solution Approach 1:
The patent uses dynamic frequency adjustment to control power transmission smoothly. Instead of relying solely on increasing switching frequency to reduce power, the system dynamically modulates the frequency within an optimized range while using phase shift control to achieve continuous power adjustment. This dynamic approach allows smooth power reduction without hitting the limits of switching frequency.
Solution Approach 2:
The patent applies preliminary action by pre-setting the switching frequency within an optimized range before operation begins. The controller is configured with predetermined frequency limits that ensure smooth switching capability is maintained. By establishing the frequency range in advance, the system prevents operation near the limits where smooth switching would fail, thereby ensuring continuous bidirectional switching capability throughout operation.
3Ease of operation
If bidirectional active bridge circuit is used to achieve smooth switching, then operation direction can be switched smoothly, but large off-current and circulating current problems occur
Solution Approach 1:
The patent uses the resonant circuit as an intermediary between the primary and secondary bridges. The resonant CLLC circuit acts as a medium that transfers power with minimal circulating current, unlike the direct coupling in bidirectional active bridge circuits. This intermediary resonant circuit enables smooth bidirectional switching while significantly reducing the harmful circulating currents and off-currents associated with direct bridge-to-bridge coupling.
Solution Approach 2:
The patent exploits resonant vibration at the operating frequency of the CLLC circuit to achieve efficient power transfer with minimal losses. By operating at or near the resonant frequency, the circuit minimizes circulating current and maximizes power transfer efficiency. The resonant oscillation enables smooth bidirectional switching without the large circulating currents that plague non-resonant bidirectional bridge circuits.
Data Source
AI summary
Provided is a method for controlling smooth switching of an operation direction of a bidirectional resonant CLLC circuit, which applies to the bidirectional resonant CLLC circuit. The method includes the following steps: Step 1: detecting a current circuit state and controlling the bidirectional resonant CLLC circuit to operate in a forward operation state by means of a primary bridge and a secondary bridge, by a controller; Step 2: performing Step 3 when an externally transmitted reference signal received by the controller or an internal preset reference signal in the controller is an operation direction switching signal; Step 3: performing frequency conversion control, by the controller; Step 4: performing preparation of phase shift control and generating a driving signal of the secondary bridge, by the controller; Step 5: performing the phase shift control, by the controller; and Step 6: switching a circuit operation state to an inverse operation mode.