AN 995: Three-phase Boost Bidirectional AC-DC and LLC DC-DC Converter for EV Charging Design Example

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ID 784593
Date 9/15/2023
Public
Document Table of Contents
Document Table of Contents x
1. About the Three-phase Boost Bidirectional AC-DC and LLC DC-DC Converter for Electric Vehicle (EV) Charging Design Example 2. Getting started with the Design Example 3. Functional Description 4. Top-level VHDL Wrapper 5. Simulink Simulation Results 6. Document Revision History for AN 995: Three-phase Boost Bidirectional AC-DC and LLC DC-DC Converter for EV Charging Design Example
1. About the Three-phase Boost Bidirectional AC-DC and LLC DC-DC Converter for Electric Vehicle (EV) Charging Design Example x
AC-DC Converter LLC DC-DC Converter Six-switch boost converter 1.1. FPGA Resource Usage
2. Getting started with the Design Example x
2.1. Software Requirements 2.2. Hardware Requirements 2.3. Downloading the Design 2.4. Installing the Design Example Templates 2.5. Programming the Board with the Design 2.6. Generating HDL Code with MATLAB and HDL Coder
2.5. Programming the Board with the Design x
2.5.1. Running the Design
2.6. Generating HDL Code with MATLAB and HDL Coder x
2.6.1. Generating HDL and QPF Using MATLAB Scripts 2.6.2. Generating HDL and QPF Using MATLAB GUI Tools
3. Functional Description x
3.1. Simscape* Model 3.2. Simulink* Model 3.3. HDL Inputs, Outputs, and Parameters
3.2. Simulink* Model x
3.2.1. AC-DC Converter Controller 3.2.2. Power Electronics 3.2.3. Source Voltage Generator Block 3.2.4. LLC DC-DC Converter
3.2.1. AC-DC Converter Controller x
3.2.1.1. PWM Controller 3.2.1.2. PLL 3.2.1.3. Sample and Hold Block 3.2.1.4. Clarke and Park Transforms
3.2.2. Power Electronics x
3.2.2.1. Six-switch Power Converter 3.2.2.2. Inductors 3.2.2.3. Output Capacitor
1. About the Three-phase Boost Bidirectional AC-DC and LLC DC-DC Converter for Electric Vehicle (EV) Charging Design Example
2. Getting started with the Design Example
3. Functional Description
4. Top-level VHDL Wrapper
5. Simulink Simulation Results
6. Document Revision History for AN 995: Three-phase Boost Bidirectional AC-DC and LLC DC-DC Converter for EV Charging Design Example

1. About the Three-phase Boost Bidirectional AC-DC and LLC DC-DC Converter for Electric Vehicle (EV) Charging Design Example

This design example demonstrates a three-phase boost bidirectional AC-DC and inductor-inductor-capacitor (LLC) DC-DC converter for EV charging. It uses the MATLAB* HDL Coder to generate synthesizable VHDL code to control and emulate power electronics. The design targets Intel® MAX® 10 and Cyclone® V SoC FPGA Development Kits.

As transportation vehicles are electrified, attention switches from fuel consumption to electrical energy consumption and the efficiency and cost of power converters. Fixed-function chips (ASICs) or microcontrollers with limited update rates control several power converters.

FPGAs enable custom digital designs at very high frequencies. FPGAs reduce the size and cost of passive components required to stabilize voltage or change from traditional pulse width modulation (PWM) switching waveforms to other methods to reduce switching losses. These methods may be an advantage in heavily used high-voltage electric vehicle charging stations.

At a high level, the design shows two building blocks of an EV charging station, usually called the AC-DC conversion module and DC-DC conversion module.

In EV charging power stations, an AC-DC power converter unit can feed multiple DC-DC power converter units that ultimately charge the electric cars. Many EV charging manufacturers use this topology as modules, which you can buy and connect to as you desire.

Figure 1. Common EV Charger Power Architecture

The design example:

  • Simulates the three-phase boost bidirectional AC-DC and LLC DC-DC converter for EV charging on hardware from MATLAB Simulink* and Simscape Electronics*.
  • Examines on-chip signals using the Signal Tap logic analyzer.
  • Generates HDL code based on MATLAB HDL Coder and tools.
  • Includes files to program and run Intel® MAX® 10 and Cyclone® V SoC FPGA Development Kits.

The design helps you to:

  • Maximize the FPGA clock frequency to generate PWM waveforms.
  • Reduce the FPGA resource use by optimizing the fixed-point signal formats.
  • Simulate the interface to external sensors and transistors in a detailed manner.
  • Simulate the external sensors and ADCs.
  • Consider different control algorithms to the existing PI and PWM control to improve efficiency while limiting worst-case voltage error.
  • Extend the design from DC input to a single or three-phase AC input to simulate electric vehicle charging.
  • Use Signal Tap logic analyzer to acquire signals in real-time from the FPGA.
Figure 2. The Three-phase Boost Bidirectional AC-DC and LLC DC-DC Converter for EV Charging Design Example Blocks

The figure shows the design blocks and how an FPGA is incorporated to emulate power electronics and implement an actual PWM switching controller:

The charger electronics simulation has:

  • Three-phase active rectifier with PFC and DC boost simulation.
  • Bidirectional for vehicle to grid (V2G).
  • 20 MHz updates.
  • Vehicle represented by load current waveform.

The charger control has:

  • Simple voltage command profile
  • Control algorithm
  • Output transistor gate signals
  • 20 MHz updates

AC-DC Converter

The design's three-phase boost bidirectional AC-DC converter comprises three main parts.

  • Controller
  • Power electronics
  • Source voltage generator

A MATLAB Simulink* synthesized model mimics the 230 VRMS national power grid common in many European countries. This model generates HDL code to emulate the behavior of the three-phase grid within the FPGA.

In a real-product scenario, this controller and the LLC DC-DC converter controller are the only blocks in this design that you implement on FPGA. The controller generates PWM signals to drive the power transistors in the six-switch power converter and senses different currents and voltages so that it generates the desired DC output voltage.

The power electronics comprises a six-switch power converter and high-power electronics, such as capacitors or inductors. In an actual EV charging station, the FPGA controls this section of the system using PWM signals. A synthesized MATLAB* model emulates the behavior of power transistors, capacitors, inductors, and resistors in the FPGA.

LLC DC-DC Converter

The design's resonant LLC DC-DC converter comprises:

  • Controller
  • Power electronics

In a real-product scenario, this controller and the AC-DC converter controller are the only blocks that you implement in an FPGA. The controller generates the necessary signals to drive the gates of the power transistors in the DC-DC power electronics and senses the output voltage, so it generates the desired DC output voltage.

The resonant LLC DC-DC converter has the following specification:

  • 800 V DC input voltage
  • Output voltage of 500V
  • Output power of 100kW
  • High efficiency (>95%)
  • Minimal overshoot while maintaining quick settling time

The power electronics comprise a transistor bridge feeding a resonant capacitor and transformer primary winding. The transformer’s secondary winding drives a diode bridge and smoothing capacitor. In a real EV charger station, the FPGA controls this section of the system using PWM signals.

Six-switch boost converter

The six-switch boost converter is a three-phase AC-DC converter that allows bidirectional power flow. It has the following specifications:

  • Emulated 650 Vpeak-peak input voltage at 50 Hz to replicate 230 VRMS phase voltage in the national power grid
  • Output voltage of 800 V
  • Output power of 100 kW
  • High efficiency (>95%)
  • Minimal overshoot while maintaining quick-settling time
  • Very high frequency operation

Section Content
FPGA Resource Usage

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