Non-Insulated Power Conditioner Ground Potential Control
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Solution Overview
Problem
Conventional non-insulated type power conditioners fail to maintain the potential on the negative-electrode side of direct current power sources, such as solar cells and fuel cells, at a level equivalent to the ground potential, leading to safety issues and aging degradation in thin film solar cells.
Innovation Solution
A non-insulated type power conditioner with a circuit that generates square wave voltages and adjusts them to sinusoidal wave voltages, ensuring the negative-electrode side potential is maintained at or above the ground potential, using a combination of first, second, and third circuits with specific chopping frequencies and PWM control to achieve this.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a non-insulated type power conditioner is used to improve power conversion efficiency, then power conversion efficiency is improved, but the potential on the negative-electrode side cannot be maintained at ground potential level
Solution Approach 1:
The patent introduces a potential control circuit as an intermediary component between the DC power source and the inverter. This control circuit actively manages the potential on the negative-electrode side by using switching elements and control signals to maintain it at ground potential level, thereby resolving the contradiction between maintaining efficiency (no insulation transformer) and maintaining reliability (potential control).
Solution Approach 2:
The patent dynamically changes the electrical potential parameter on the negative-electrode side through active control. By using switching elements controlled by control signals, the system adjusts and maintains the potential at the desired ground potential level, enabling the non-insulated type to achieve both efficiency and reliability.
2Ease of manufacture
If thin film solar cells are used to reduce material volume and simplify production, then manufacturing cost and complexity are reduced, but aging degradation occurs due to low negative-electrode potential
Solution Approach 1:
The potential control circuit acts as a protective intermediary that specifically benefits thin film solar cells by maintaining their negative-electrode potential at ground level. This prevents the aging degradation that would otherwise occur, thereby extending service life while preserving the manufacturing advantages of thin film technology.
Solution Approach 2:
The control circuit applies preliminary anti-action by proactively preventing the potential drop that causes aging degradation. By continuously maintaining the negative-electrode potential at ground potential level before degradation can occur, the system protects the thin film solar cells from the harmful effects that would otherwise limit their service life.
3Device complexity
If the negative-electrode potential is not maintained at ground potential, then device complexity is reduced, but safety issues and aging degradation occur
Solution Approach 1:
The patent introduces a potential control circuit as an intermediary that actively manages the negative-electrode potential. This control circuit uses switching elements and control signals to maintain ground potential level, thereby preventing safety issues and aging degradation without requiring the complex insulation transformer structure.
Solution Approach 2:
The patent replaces the mechanical/physical insulation approach (insulation transformer) with an electronic control approach (potential control circuit using switching elements). This substitution maintains the desired potential level through electronic means rather than physical isolation, reducing overall system complexity while achieving the same safety and reliability goals.
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 effectively maintains the negative-electrode side potential at ground level, enhancing safety and preventing aging degradation in thin film solar cells while improving power conversion efficiency by reducing switching losses and selecting less conductive switching elements.
Implementation Method 1
a first circuit for chopping a direct current voltage from the direct current power source at a first frequency as a system frequency and thereby generating a first sequence of square wave voltages
Implementation Method 2
a second circuit for using a potential of the first sequence of square wave voltages as a second reference potential, the second circuit chopping an output of the first circuit at a second frequency a predetermined number of times as high as the first frequency and thereby generating a second sequence of square wave voltages
Implementation Method 3
the second circuit further summing the first and second sequences of square wave voltages and thereby generating a third sequence of square wave voltages including a plurality of square wave voltages having a voltage level that changes to the positive and negative sides in turns
Implementation Method 4
a third circuit for chopping the third sequence of square wave voltages at a third frequency determined by a timing that depends on if a voltage difference thereof to a sinusoidal wave voltage results in a positive value or a negative value and outputting the chopped third sequence of square wave voltages
Implementation Method 5
the third circuit further PWM-controlling the charge/discharge output at a PWM frequency higher than the third frequency so that the voltage difference between the third sequence of square wave voltages and the sinusoidal wave voltage is corrected and thereby generating the sinusoidal wave voltage
Data Source
AI summary
A first circuit generates a first sequence of square wave voltages having a voltage level that changes to a positive side relative to a first reference potential, which is a potential on a negative-electrode side of a direct current power source, from a direct current voltage. A second circuit generates a second sequence of square wave voltages having a voltage level lower than the voltage level of the first sequence of square wave voltages on the positive side that changes to a negative side relative to a second reference potential. The second chopper circuit further generates a third sequence of square wave voltages having a voltage level that changes to the positive and negative side in turns in the manner of sinusoidal wave relative to the first reference potential by summing the first sequence of square wave voltages and the second sequence of square wave voltages. A third circuit outputs the third sequence of square wave voltages as a charge/discharge output. The third circuit further PWM-controls the charge/discharge output so that a difference of the third sequence of square wave voltages to a sinusoidal wave voltage is corrected and thereby generates a sinusoidal wave voltage that continuously changes to the positive and negative sides relative to the first reference potential from the third sequence of square wave voltages and the PWM-controlled output, and outputs the generated sinusoidal wave voltage to a load.