Split-Phase Inverter Compensation for Transformer Current Unbalance
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Solution Overview
Problem
The integration of single-phase distributed power sources into transformer areas leads to unbalanced load currents across three-phases, causing excessive overloads and potential failure of distribution transformers, as existing methods like single-phase active power filters are inefficient and require additional equipment and costs.
Innovation Solution
A system and method utilizing a distributed power supply and a three-phase full-bridge inverter connected through a reactor, which outputs compensation currents to balance the phases, with filter capacitors and hysteresis control to adjust unbalanced currents, ensuring balanced distribution transformer currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single-phase active power filters are used to compensate zero-sequence currents, then three-phase balance can be achieved, but additional equipment and costs are required
Solution Approach 1:
The inverter is designed to perform multiple functions: it not only integrates distributed power sources but also compensates for zero-sequence currents and achieves three-phase balance. By making the inverter multi-functional, the patent eliminates the need for separate active power filter equipment while maintaining the three-phase balance capability.
Solution Approach 2:
The patent combines the functions of distributed power source integration and zero-sequence current compensation into a single inverter system. The inverter simultaneously handles power conversion and current compensation, merging what were previously separate functions into one unified device, thereby reducing equipment complexity.
2Power
If distributed power sources are integrated into transformer areas, then power supply capacity is improved, but three-phase current balance deteriorates
Solution Approach 1:
The control system continuously monitors the three-phase currents and calculates the zero-sequence current components. Based on this feedback, the inverter dynamically adjusts its output to compensate for the unbalance caused by distributed power sources, thereby maintaining three-phase balance while allowing flexible integration of distributed power.
Solution Approach 2:
The patent changes the control parameters of the inverter to actively compensate for the unbalance. By adjusting the inverter's output current parameters based on the detected zero-sequence components, the system maintains three-phase balance despite the variable power injection from distributed sources.
3Reliability
If inverter outputs compensation currents through three-phase reactor, then three-phase unbalance adjustment is achieved, but equipment complexity increases
Solution Approach 1:
The inverter is designed to perform multiple functions: it not only integrates distributed power sources but also compensates for zero-sequence currents and achieves three-phase balance. By making the inverter multi-functional, the patent eliminates the need for separate active power filter equipment while maintaining the three-phase balance capability.
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 balances three-phase currents, reducing the risk of transformer overload and failure, while optimizing the use of distributed power sources and reducing equipment costs by using existing photovoltaic power supplies for compensation.
Implementation Method 1
a three-phase full-bridge inverter provided with a positive inverter input terminal, a negative inverter input terminal, an inverter a-phase output terminal, an inverter b-phase output terminal, and an inverter c-phase output terminal, wherein the positive inverter input terminal is connected to the positive power output terminal, the negative inverter input terminal is connected to the negative power output terminal, the inverter a-phase output terminal, the inverter b-phase output terminal, and the inverter c-phase output terminal are connected to the a-phase line, the b-phase line, and the c-phase line, respectively, through a three-phase reactor
Implementation Method 2
a first filter capacitor connected to the positive inverter input terminal and the positive power output terminal; a second filter capacitor connected in series with the first filter capacitor, wherein the second filter capacitor is connected to the negative inverter input terminal and the negative power output terminal
Data Source
AI summary
In the present invention, a system and a method for unbalance adjustment for inverter split-phase controlling and distribution transformer current are provided, in which the system for unbalance adjustment for inverter split-phase controlling and distribution transformer current includes a distributed power supply and a three-phase full-bridge inverter. The three-phase full-bridge inverter is connected to the distributed power supply, and the three-phase full-bridge inverter is connected to a three-phase line through a three-phase reactor. When an unbalance degree corresponding to the three-phase line is greater than a preset starting value, a three-phase compensation current reference value is obtained according to the present front-end three-phase load current, back-end three-phase load current and capacitor voltage control component, such that the three-phase full-bridge inverter can output the three-phase compensation current based on the three-phase compensation current reference value. Therefore, in embodiments of the present invention, the three-phase full-bridge inverter can use the output power of the distributed power supply to output the compensation current required for each phase of the three-phase line, realizing the unbalanced control in the three-phase current of the distribution transformer, so that the three-phase current of the distribution transformer reaches balance.