Delta-Connected H-Bridge Converter Modules for Grid Stability
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Solution Overview
Problem
Renewable energy systems, such as wind power, face challenges in maintaining grid stability due to high reactive power demands, leading to decreased power factor, voltage drops, and increased line losses, which existing solutions like static var compensators struggle to address effectively, especially with the generation of high-order harmonics.
Innovation Solution
A power compensation apparatus and method utilizing delta-connected converter modules with H-bridge circuits and energy storage units to provide reactive and active power regulation, converting DC voltage to AC voltage, allowing for capacitive or inductive reactive power compensation and active power balancing, thereby stabilizing the electrical grid and addressing unbalanced loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a static var compensator (SVC) with thyristor-controlled reactor is used for reactive power compensation, then the voltage can be adjusted rapidly and smoothly, but high-order harmonics are generated requiring special filters
Solution Approach 1:
The patent replaces the thyristor-controlled mechanical switching system with an H-bridge circuit using power electronic switches (IGBTs or MOSFETs) that can rapidly change state without generating high-order harmonics. The H-bridge circuit synthesizes AC voltage from DC through pulse-width modulation, eliminating the harmonic generation inherent in thyristor-based SVC systems while maintaining fast response capability.
Solution Approach 2:
The patent changes the operating parameters by using pulse-width modulation (PWM) control to generate variable frequency and variable voltage output from the H-bridge circuit. This allows the system to dynamically adjust reactive power compensation while avoiding fixed-frequency harmonic generation, solving both the speed requirement and harmonic elimination requirement.
2Power
If induction generators are used in wind power systems, then the generator capacity is reduced, but reactive power consumption increases by 25%-30% of generator capacity
Solution Approach 1:
The H-bridge circuit is designed to perform multiple functions: it provides reactive power compensation to offset the 25%-30% reactive power consumption of induction generators, simultaneously enables active power regulation to balance grid output, and can operate in both capacitive and inductive modes. This multi-functionality resolves the contradiction by making a single device capable of addressing all power quality issues.
Solution Approach 2:
The patent introduces an H-bridge circuit as an intermediary device between the induction generator and the electrical grid. This intermediary actively manages power flow, providing the necessary reactive power to the generator while regulating active power to the grid, thereby resolving the reactive power consumption issue without affecting generator capacity.
3Productivity
If active power output varies with wind speed in wind power systems, then renewable energy generation is optimized, but frequency stability of the electrical grid deteriorates
Solution Approach 1:
The patent implements feedback control through the H-bridge circuit that continuously monitors grid frequency and active power demand. When wind speed variations cause frequency deviations, the control system adjusts the active power output through PWM modulation of the H-bridge circuit, providing frequency stabilization while maintaining optimized renewable energy generation based on wind availability.
4Adaptability or versatility
If converter modules are connected in delta configuration for power compensation, then unbalanced loads can be compensated, but the system complexity increases
Solution Approach 1:
The patent divides the power compensation system into three independent converter modules, each with its own H-bridge circuit and control system. Each module can independently handle one phase or combination of phases, allowing modular deployment and simplified maintenance while providing comprehensive unbalanced load compensation capability through the delta configuration.
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
The solution effectively maintains grid voltage and frequency stability, provides low voltage ride-through capabilities, and compensates for unbalanced loads without generating high-order harmonics, enhancing the overall stability and efficiency of renewable energy systems.
Implementation Method 1
an H-bridge circuit connected to the capacitor in parallel for converting the DC voltage into an AC voltage
Data Source
AI summary
A power compensation apparatus for a renewable energy system includes a plurality of converter modules positioned between any two phases of a three-phase AC electrical grid, each converter module including a plurality of inverter circuits connected in series. Each inverter circuit includes an energy storage unit for providing a direct current (DC) voltage; a capacitor connected to the energy storage unit; and an H-bridge circuit converting the DC voltage into an alternating current (AC) voltage. The converter modules perform reactive power compensation and active power regulation on the electrical grid in a delta connection. A plurality of converter modules are respectively positioned between any two phases of the electrical grid in a delta connection, so as to keep the voltage of the electrical grid continuously stable when the voltage of the electrical grid fluctuates, and also compensate load current when system load is not balanced.