Surge Voltage Blocker Circuit for Grid Power Converters
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Solution Overview
Problem
Transformer-less grid-connected power conversion systems face protection challenges from lightning-induced overvoltage and overcurrent transients, particularly due to their sensitivity and exposure to grid-originated disturbances, which conventional methods like surge arrestors or metal-oxide varistors cannot adequately address when insulation strength is lower than protective levels.
Innovation Solution
A surge voltage blocker circuit is introduced, comprising series-coupled AC switch circuits with bidirectional switches and transient voltage suppression devices, along with a controller to manage voltage surges by charging a DC bus and bypassing current to ground, providing effective protection against voltage surges without an intervening low-frequency transformer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional surge arrestors or metal-oxide varistors (MOVs) are used for protection, then insulation requirements are met, but protection against overvoltage surges is insufficient when insulation strength is lower than MOV protective levels
Solution Approach 1:
The surge protection function is divided into multiple independent components: series-coupled AC switch circuits for voltage blocking, transient voltage suppression devices for clamping, and snubber circuits for transient management. Each component handles specific aspects of surge protection, providing layered defense where the AC switches block high-voltage surges before they reach sensitive equipment, while TVS devices provide secondary clamping protection.
Solution Approach 2:
The AC switch circuits act as intermediary protective elements positioned between the grid and the power conversion system. These switches can rapidly close to block surge currents from propagating to sensitive equipment, serving as an active mediator that dynamically intervenes to protect the system without requiring the sensitive equipment to have high insulation strength.
2Weight of stationary object
If transformer-less grid-connected power conversion systems are used, then volume and mass are reduced, but protection challenges from lightning-induced overvoltage increase
Solution Approach 1:
The system incorporates proactive protective measures including snubber circuits that are pre-configured to absorb and damp transient voltage spikes before they can damage sensitive components. The AC switch circuits are positioned upstream to block surge currents before they reach the power conversion system, providing advance cushioning against lightning-induced overvoltage without adding significant mass.
Solution Approach 2:
The protection system dynamically changes operational parameters by rapidly switching AC switches on/off in response to detected surges. The controller monitors voltage conditions and adjusts the switching state of protection circuits in real-time, changing the system's electrical parameters adaptively to respond to lightning-induced overvoltage events while maintaining the transformer-less compact design.
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 effectively protects grid-side power converters from lightning-induced surges by managing surge currents and voltages, ensuring reliable operation even when insulation strength is below MOV protective levels, thereby enhancing the reliability of transformer-less power conversion systems.
Implementation Method 1
a transient voltage suppression device coupled in parallel with the bidirectional switch. The surge voltage blocker circuit may provide lightning protection to the grid-side power converter
Implementation Method 2
a bidirectional switch formed of a first power transistor and a second power transistor
Implementation Method 3
at least some of the plurality of series-coupled AC switch circuits further comprise a snubber circuit in parallel with the bidirectional switch
Implementation Method 4
the controller is to control gate circuitry of the bidirectional switch of the plurality of series-coupled AC switch circuits
Implementation Method 5
The transient voltage suppression device is to pass at least a portion of a surge current to the power conversion system, where the surge current is to charge a DC bus
Implementation Method 6
In response to a voltage of the DC bus that exceeds a threshold, the controller is to control the switch circuitry to cause the surge current to bypass the DC bus and flow to a ground node
Data Source
AI summary
In one embodiment, an apparatus includes a surge voltage blocker circuit to couple between a distribution grid network and a grid-side power converter of a power conversion system. The surge voltage blocker circuit may include a plurality of series-coupled AC switch circuits, each including: a bidirectional switch formed of a first power transistor and a second power transistor; and a transient voltage suppression device coupled in parallel with the bidirectional switch.