DC-DC Converter and Inverter Control for Solar Power Conversion
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Solution Overview
Problem
The existing power conversion systems face inefficiencies due to voltage drops across semiconductor devices, leading to errors in bus voltage determination and increased power conversion losses in inverters when converting DC power from solar cells to AC power.
Innovation Solution
A power conversion system comprising a DC-DC converter and an inverter, controlled by separate controllers to manage step-up operations and maintain optimal bus voltage, reducing conversion losses by comparing bus voltage with reference values and adjusting operations accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the bus voltage is controlled to be close to the system voltage to reduce power conversion loss, then the power conversion loss in the inverter is reduced, but the operating voltage point of the solar cell cannot reach the optimal value when the optimal point is in a zone equal to or higher than the bus voltage
Solution Approach 1:
The patent applies dynamics by making the control mode of the DC-DC converter switchable between step-up operation and non-step-up operation based on the relationship between input voltage and bus voltage. This dynamic adjustment allows the system to adapt to different operating conditions, enabling the solar cell to operate at its optimal voltage point while maintaining efficient power conversion to the grid.
2Measurement precision
If the reference value is increased by a margin to compensate for voltage drop errors, then the measurement accuracy of bus voltage is improved, but the bus voltage increases which reduces the loss reduction effect
Solution Approach 1:
The patent introduces an intermediary correction value that represents the voltage drop across semiconductor devices. This correction value is subtracted from the measured bus voltage to obtain the accurate input voltage of the solar cell. By using this intermediary correction mechanism, the system achieves precise voltage measurement without needing to increase the reference value margin, thus avoiding increased power conversion loss.
3Ease of operation
If separate controllers are used for the step-up converter and inverter, then the device complexity is reduced and ease of operation is improved, but communication is required between controllers which increases device complexity
Solution Approach 1:
The patent applies self-service by enabling each controller to independently determine its own control mode based on locally available voltage information. The first controller uses the bus voltage and correction value to determine step-up converter operation, while the second controller uses the same information to determine inverter operation. This self-service approach eliminates the need for inter-controller communication, maintaining simplicity while achieving coordinated control.
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 approach reduces inverter conversion losses and maximizes solar cell electricity generation by accurately controlling the DC-DC converter and inverter operations based on bus voltage, minimizing errors from semiconductor devices.
Implementation Method 1
a DC-DC converter that converts a DC power supplied from a solar cell into a DC power of a different voltage
Implementation Method 2
an inverter that converts the DC power input from the DC bus into an AC power
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A DC-DC converter 11 converts a DC power supplied from a solar cell 2 into a DC power of a different voltage and outputs the DC power to a DC bus 30. An inverter 21 converts the DC power input from the DC bus 30 into an AC power and outputs the AC power to a system 3. A first controller 12 controls the DC-DC converter 11 to perform a step-up operation when a voltage on the DC bus 30 is lower than a first reference voltage and controls the DC-DC converter 11 to suspend the step-up operation when the voltage is equal to or higher than the first reference voltage. A second controller 22 controls the inverter 21 to maintain the voltage on the DC bus 30 constant when the voltage on the DC bus 30 is lower than a second reference voltage and controls the inverter 21 to maximize an output power of the inverter 21 when the voltage is equal to or higher than the second reference voltage.