Power Converter Discharge Loop for Common-Mode Voltage Grounding
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Solution Overview
Problem
Photovoltaic power generation systems face challenges in rapidly discharging common mode voltages to ground at the input terminal of a boost circuit, as these voltages often exceed safe voltage levels during system maintenance or emergencies, failing to meet discharge voltage requirements.
Innovation Solution
A power converter is designed with a boost circuit, inverter circuit, bridge circuit, and switching circuit, utilizing controllable switches to form a discharge loop that rapidly discharges common mode voltages to ground by short-circuiting the positive and negative input terminals of the boost circuit through the bridge and switching circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the optimizer or shutdown device enters safe mode to cut off or control input voltage within safe levels, then the input voltage is reduced to safe levels, but the common mode voltage to ground remains much higher than safe voltage and cannot meet discharge voltage requirement
Solution Approach 1:
The patent segments the voltage control function into two independent parts: (1) input voltage control through the optimizer/shutdown device, and (2) common mode voltage discharge through a separate discharge circuit. This discharge circuit includes a discharge switch connected between the positive and negative input terminals of the boost circuit, allowing independent control of common mode voltage without affecting the input voltage control mechanism.
Solution Approach 2:
The patent introduces a discharge switch as an intermediary component specifically for discharging common mode voltage. This switch acts as a mediator that provides a controlled discharge path for common mode voltage to ground, separating this function from the main input voltage control pathway and enabling independent management of the harmful common mode voltage.
2Device complexity
If conventional discharge methods are used without a dedicated discharge circuit, then the system structure remains simple, but the common mode voltage cannot be rapidly discharged to within safe voltage levels
Solution Approach 1:
The patent incorporates a discharge switch that can be pre-positioned and rapidly activated when common mode voltage discharge is needed. The switch is integrated into the circuit structure in advance, allowing immediate discharge action without requiring additional complex control mechanisms, thus achieving fast discharge while maintaining relatively simple system structure.
3Reliability
If the discharge voltage requirement is not met with common mode voltage remaining high, then additional discharge components are added, but the system complexity increases
Solution Approach 1:
The discharge switch serves multiple functions: (1) providing a discharge path for common mode voltage, (2) being controllable through existing control signals from the optimizer or shutdown device, and (3) integrating into the existing circuit topology without requiring completely separate control systems. This multi-functionality reduces the need for additional dedicated control components.
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 discharges common mode voltages to within safe voltage levels, meeting discharge voltage requirements by rapidly reducing voltages to within 30V within 30 seconds.
Implementation Method 1
The plurality of controllable switches are controlled to be switched on or switched off to form the discharge loop by the boost circuit, the bridge circuit, and the switching circuit, for discharging the common mode voltage to ground
Data Source
Figure 1~2
Figure 3~4a
Figure 4b~5
AI summary
Provided are a power converter, a method for controlling a power converter, and a power system. The power converter includes a boost circuit, an inverter circuit, a bridge circuit, a switching circuit, and a controller. The boost circuit has an input terminal connected to a direct current power supply and an output terminal connected to each of an input terminal of the inverter circuit and an input terminal of the bridge circuit. The switching circuit is connected to each of an output terminal of the bridge circuit and ground. The switching circuit at least includes a plurality of controllable switches. The controller is configured to control, subsequent to the direct current power supply entering an off state, the plurality of controllable switches to be switched on or switched off to form a discharge loop by the boost circuit, the bridge circuit, and the switching circuit, for discharging a common mode voltage to ground at the input terminal of the boost circuit to be within a safe voltage. In this way, a discharge voltage at the input terminal of the boost circuit can be satisfied.