Switching Device Control for DC Converter Voltage Range
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Solution Overview
Problem
Conventional photovoltaic installations face limitations in extending the working voltage range of switching devices, leading to increased power losses and costs due to overvoltages and high losses in switching operations, especially when operating close to the breakdown voltage of transistors, which restricts the maximum direct current voltage to 1000 V.
Innovation Solution
A control system for switching devices that dynamically modifies switch-on and switch-off conditions by controlling the current derivative through the gate voltage, particularly during switch-off, using a voltage source, capacitance, and gate resistors to manage overvoltages and reduce switching losses, allowing operation closer to breakdown voltages without unnecessary losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the maximum direct current voltage is increased to extend the working voltage range, then the power of the converter is increased, but overvoltages during switching operations exceed the breakdown voltage of switching devices
Solution Approach 1:
The control system proactively reduces the current derivative through the switching device before overvoltages can develop during switching operations. By controlling di/dt through gate voltage modulation and using a capacitance connected via a connecting element, the system prevents overvoltage formation in advance, allowing safe operation at higher DC voltages that increase converter power capability.
Solution Approach 2:
A capacitance is introduced as an intermediary element between the DC voltage source and the switching device. This capacitance, when activated through the connecting element, acts as a buffer that limits current derivative and prevents overvoltage formation, enabling the switching device to operate safely at higher voltages without direct exposure to voltage spikes.
2Ease of manufacture
If conventional switching techniques are used at 1000 V DC, then the installation cost is reduced, but overvoltages damage converters with 1200 V switching devices
Solution Approach 1:
The capacitance serves as a protective intermediary that filters harmful overvoltages during switching operations. By placing this capacitance in the circuit and activating it through the connecting element controlled by the control unit, overvoltages are prevented from reaching the switching device, enabling safe operation at 1000 V DC with standard 1200 V devices without additional expensive protective equipment.
Solution Approach 2:
The control system uses its own control unit to manage the connecting element that activates the capacitance when needed. This self-service approach allows the system to autonomously protect itself from overvoltages during switching operations without requiring external protective devices, maintaining cost-effectiveness while preventing damage.
3Loss of energy
If the direct current voltage is increased to reduce Joule-effect losses, then the efficiency is improved, but the switching devices work close to their physical limits
Solution Approach 1:
The control system proactively manages the current derivative through gate voltage control before switching operations occur. By pre-configuring the capacitance and control logic to limit di/dt, the system enables operation at higher DC voltages that reduce Joule losses, while simultaneously preventing overvoltages that would erode the voltage margin of switching devices.
4Device complexity
If standard switching devices with fixed breakdown voltages are used, then the device complexity is reduced, but the working voltage range cannot be extended
Solution Approach 1:
The system dynamically adjusts the switching conditions by controlling the current derivative through gate voltage modulation. The capacitance is selectively activated through the connecting element based on real-time switching needs, creating a dynamic protection mechanism that allows standard switching devices to operate safely across an extended voltage range without requiring custom high-voltage devices.
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 enables safer operation of switching devices at higher direct current voltages, reducing overvoltages and switching losses, thereby increasing the maximum direct current voltage range and enhancing the efficiency and cost-effectiveness of photovoltaic installations.
Implementation Method 1
controlling a derivative of current with respect to time through a switching device (1) by means of a gate voltage of the switching device (1), particularly during a switch-off of the switching device (1)
Implementation Method 2
A control system for switching devices that dynamically modifies switch-on and switch-off conditions by controlling the current derivative through the gate voltage, particularly during switch-off, using a voltage source, capacitance, and gate resistors
Data Source
Figure 1a~1b
Figure 1c
Figure 2
AI summary
The present invention relates to a control system and control method for controlling a switching device (1) integrated in an electronic converter, the object of which is to extend the working voltage range of the switching devices and thus increase the power of the electronic DC/AC converter which prepares the energy produced by a energy generating system and injects it into the electrical grid. It basically comprises a voltage source (3), a capacitance (7), a first gate resistor (21) and a second gate resistor (22), a first circuit formed by a series resistor (6) 10 with a first diode (5), a second circuit formed by a second diode (4) and a connecting element (8) controlled by a control unit (12) that controls the opening and closing thereof. Another object of the present invention is a switching cell for an electronic converter comprising said control system.