Photovoltaic Inverter Discharging Circuit for Rapid Voltage Reduction
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Solution Overview
Problem
Existing photovoltaic systems face challenges in rapidly reducing voltage to ensure safety during maintenance, as the large capacitance of direct current bus capacitors and small resistance in passive discharging circuits result in high discharging power, leading to increased volume and cost of photovoltaic inverters.
Innovation Solution
The introduction of a discharging circuit with smaller capacitance Y capacitors and larger resistance, where the insulation resistance detection circuit doubles as a discharging circuit, reduces the volume and cost of the photovoltaic inverter by efficiently discharging electrical energy through a larger resistance, achieving rapid voltage reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a passive discharging circuit with a discharge resistor is used to discharge the direct current bus capacitor, then the voltage can be reduced to below 30V within 30 s, but the discharging power is large resulting in a large volume of the inverter
Solution Approach 1:
The patent segments the capacitor group into multiple capacitors (first capacitor, second capacitor, third capacitor, fourth capacitor) with different capacitance values. The discharging circuit selectively discharges specific capacitors based on the shutdown scenario, avoiding the need to discharge the entire large-capacitance direct current bus capacitor group, thereby reducing the required discharging power and allowing for a smaller inverter volume.
Solution Approach 2:
The patent changes the capacitance parameters of individual capacitors within the bus capacitor group. By using capacitors with different capacitance values (C1, C2, C3, C4) instead of a single large capacitor, the system can control the discharging power by selecting which capacitors to discharge, thus reducing the inverter volume while maintaining the voltage reduction requirement.
2Speed
If the direct current bus capacitor directly discharges electrical energy through a discharge resistor with small resistance, then rapid voltage reduction is achieved, but the discharging power is large increasing the cost of the photovoltaic system
Solution Approach 1:
The patent segments the capacitor group into multiple capacitors (first capacitor, second capacitor, third capacitor, fourth capacitor) with different capacitance values. The discharging circuit selectively discharges specific capacitors based on the shutdown scenario, avoiding the need to discharge the entire large-capacitance direct current bus capacitor group, thereby reducing the required discharging power and allowing for a smaller inverter volume.
Solution Approach 2:
The patent changes the capacitance parameters of individual capacitors within the bus capacitor group. By using capacitors with different capacitance values (C1, C2, C3, C4) instead of a single large capacitor, the system can control the discharging power by selecting which capacitors to discharge, thus reducing the inverter volume while maintaining the voltage reduction requirement.
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 solution reduces the volume and cost of the photovoltaic inverter while ensuring rapid voltage reduction to below 30V within 30 seconds, enhancing safety and efficiency during shutdowns.
Implementation Method 1
The first discharging circuit is configured to discharge electrical energy of the port capacitor
Data Source
AI summary
A photovoltaic inverter, a photovoltaic system, and a method for controlling discharging are provided. The photovoltaic inverter includes a first DCDC converter, an inverter circuit, a first discharging circuit, and a controller. A port capacitor is connected between a positive input end and a negative input end of the first DCDC converter. The port capacitor includes an X capacitor and a first group of Y capacitors. The first discharging circuit is connected between a common terminal of the first group of Y capacitors and a direct current bus, where the common terminal of the first group of Y capacitors is grounded. The controller is configured to control, when receiving a rapid shutdown instruction, the first discharging circuit to operate. The first discharging circuit is configured to discharge electrical energy of the port capacitor.