Working Principle and Applications of Bidirectional DC-AC Converters
Bidirectional AC-DC Converters: Principles and Applications
Bidirectional AC-DC converters (also referred to as bidirectional AC/DC converters or bidirectional AC-to-DC converters) offer several advantages, including high energy conversion efficiency, high power density, compact size, and low harmonic content, minimizing disturbances to the grid or load. These sophisticated bidirectional converters are essential for modern energy management.
A fundamental component within this system is the bidirectional DC-DC converter. A fundamental question is: what is a bidirectional DC-DC converter? It is a power electronic circuit that can regulate the flow of energy between two DC sources or a DC source and a DC bus in both directions, efficiently stepping the voltage up or down as required by the application. This functionality is crucial for managing the charge and discharge cycles of the battery within a bidirectional ac dc converter system.
This leads to the core question: what is the operating principle of the bidirectional charge and discharge module?
Core System Composition of a Bidirectional Converters
AC connection terminal: Connects to the grid, providing or receiving AC power.
Rectifier: This unit, implemented with a MOSFET bridge, functions as a bidirectional rectifier. Through controlled switching of the MOSFETs, it converts AC power to DC power.
DC-DC converter: This component is essentially a bidirectional DC-DC converter that regulates DC voltage, achieving step-up or step-down functions.
Inverter: Similarly constructed with a MOSFET bridge, this unit serves as the bidirectional inverter, converting DC power back to AC power. The design of this bidirectional inverter circuit is critical for performance.
Battery: Stores electrical energy.
- Control unit: This is the brain of the bidirectional converters, controlling overall operation, monitoring parameters in real-time, and managing communication signals.
Isolation transformer: Isolates the battery from the grid for safety.
Filter: Filters harmonics to improve output waveform quality.
Working Logic and Key Applications
The entire system, functioning as a set of highly efficient bidirectional ac to dc voltage source converters, finds extensive applications in energy storage systems, such as electric vehicles, solar energy storage systems, and wind energy storage systems. Through optimized design and control algorithms, these bidirectional converters ensure efficient and stable system operation.
Operational Mode 1: AC to DC Charging (Rectification)
AC Input: The process begins with AC input.
- Rectification: AC power is converted to DC by the rectifier. In this mode, the system operates as an AC DC bidirectional converter.
Pulse-Width Modulation (PWM) Generation: The controller monitors the AC power and generates the most suitable PWM signals.
PWM: Adjusts the MOSFET switching frequency and pulse width to stabilize the rectified DC output.
Filtering: The DC power is filtered to remove high-frequency ripple, resulting in a purer DC output.
Voltage Regulating: The stabilized DC power is adjusted by the DC-DC converter to the battery's required voltage for charging. The controller adjusts the duty cycle based on the battery's SOC to control the charging current.
The PWM signal is the key to realizing AC-DC conversion in a bidirectional ac dc converter, generated by three critical components: the controller, the control algorithm, and the PWM generator.
Operational Mode 2: DC to AC Discharge (Inversion)
- Voltage Regulating: During battery discharge, the DC power is stepped up or down by the DC-DC converter to match the grid voltage.
Pulse-Width Modulation (PWM) Generation: The controller, employing PLL technology, detects grid parameters in real-time and generates synchronized PWM signals.
PWM and Inversion: Using PWM control, the MOSFET switching is adjusted to convert DC to AC, synchronizing the output with the grid. This process is managed by the bidirectional inverter circuit.
Filtering: Used to eliminate harmonics, making the output AC waveform closer to a sine wave.
Isolation transformer: Provides safety isolation as the converted AC power is fed back to the grid, completing the DC/AC bidirectional power flow. The controller adjusts the inverter's duty cycle based on grid load and battery SOC.
The grid-connected control algorithm is mainly for the lock ring network control PLL. By sampling and processing the grid voltage, he accurately tracks the frequency and phase of the grid, provides the benchmark for the inverter PWM modulation according to the sampled reference signal, and ensures that the voltage and current output of the inverter are consistent with the phase of the grid.
AC coupled: Open source bidirectional charge and discharge battery
The system features an AC-coupled, open-source bidirectional charge and discharge battery. Bidirectional charging and discharging enables grid peak shaving, load leveling, and efficient demand-side management.
Convenient output
High conversion efficiency
Building block design
Open Hardware
- Intelligent Control
