ECE 4600 Project Proposal Group 12 Wireless Firing Interface for Power Electronic Converters Authors: Brennan Martin Luchen Song Jason Gole Meng Wang Supervisors: Dr. Ani Gole Cyrus Shafai Date of Submission: Sept 27, 2013
ii Contents 1. Introduction...1 2. Project Specifications 2 2.1 Wireless Specifications...2 2.2 Control Board Specifications. 4 2.3 Converter Specifications 5 3. Milestones.6 4. Gantt Chart 7 5. Budget...8 6. References.9 List of Tables Table 1-Wireless specifications Table 2-Controller specifications Table 3-Converter specifications Table 4-Milestones/task distribution Table 5-Proposed budget List of Figures Figure 1: Proposed system topology Figure 2: ZigBee wireless network Figure 3: Chopper circuit with DC motor load
1 1. Introduction Power Electronic (PE) converters are a family of devices used to convert electricity from one form to another. Encompassing a variety of DC-DC, DC-AC, and AC-AC devices, all modern PE converters rely on the rapid switching of semiconductor devices to function. However, PE converters are not capable of generating their own control signals, necessitating the installation of either a hardwired control board, or a wired control system capable of transmitting them. However, both methods pose problems. Hardwired boards are small, cost effective and easily installed, but can only give a single output. Changing the output of the system would require a new board. On the other hand, wired systems give operators control and allow easy monitoring, but are expensive, and also require fiber-optic cables if the system is to remain electrically isolated. A wireless system would simultaneously be small, controllable, and electrically isolated. The goal of this project is to design and implement a wireless system that is capable of controlling a basic DC-DC PE converter. The system will accept user input on a PC based interface, transmit data to a control board connected to the converter, and allow a variety of DC outputs from the converter. To allow wireless control of the system, we will be utilizing the ZigBee wireless protocol. ZigBee offers a simple, reliable transmission protocol which is designed for low power usage, whilst giving access to a multitude of integrated transmitter/microcontroller (µc) units.
2 2. Project Specifications The project will be broken down into 4 primary components: A PC based user interface A Wireless ZigBee based transmitter/receiver system An IGBT (Insulated Gate Bipolar Transistor) driver board A DC-DC PE converter Figure 1: Proposed system topology Figure 1 gives an overview of the entire system. The user interface on a pc will allow the user to make changes to input control signals for the converter. The signal is then sent to out of the transmitter and picked up by the receiver. The receiver sends the signal to the IGBT driver, which controls the converter using the acquired signal. The output of the converter can then be used to power a load. 2.1 Wireless Specifications We will be using the ZigBee wireless protocol to send data from the user to the IGBT driver. ZigBee operates according to IEEE standard 802.15.4. The ZigBee protocol will allow us a wireless range of 10 to 100 meters [1]. Testing will need to be done to determine the exact range.
3 ZigBee allows one coordinator to send data out to one or more routers or end devices, as can be seen in Figure 2. The routers can then send data further to more routers or end devices. The use of multiple routers allows the signal to be relayed from one coordinator to several routers before reaching the desired end device, increasing the maximum range of the system. For the purposes of this project, only one coordinator and one end device will be used, with no intermediate routers. Figure 2: ZigBee wireless network [2] To communicate between the user and the IGBT driver, both a transmitter and a receiver are needed. The transmitter will be the coordinator node, while the receiver will be the only end device. The ZigBee module used will contain a built in antennae, as well as a microcontroller. Having built in components will reduce the complexity of the design and will allow us to use two identical ZigBee modules for both transmitter and receiver. Using the ZigBee protocol for our wireless communication will allow us to use a single 9 volt battery to power the microcontrollers. The use of a single battery is possible because the ZigBee wireless protocol uses very little power, especially when compared to other wireless standards such as Wi-Fi or Bluetooth. Other wireless standards have the advantage of transmitting data faster than ZigBee, but for the purposes of this project low power consumption is more important than speed of transmission.
4 The user interface will allow the duty cycle of the transmitted signal to be modified. The microprocessor within the receiver will send the signal to the IGBT driver with a frequency of 2 to 5 kilohertz. The exact value will be determined when tests concerning the losses and smoothness of the waveform have been conducted. Table 1-Wireless specifications Description Specification Wireless standard ZigBee (IEEE standard 802.15.4) Power Source 9 V Wireless range 10-100m Number of microcontrollers 2 Switching frequency 2-5 KHz 2.2 Control Board Specifications As a microcontroller cannot safely supply a sufficient amount of power to switch on an IGBT, we require a controller board to interpose between the microcontroller and the converter. The controller board must accept an input signal that can be safely generated by a low power microcontroller, output enough current and voltage to switch an IGBT, and accept a supply voltage that can be provided by a battery. Desirable but nonessential characteristics include low delay time, low power usage, and the presence of a low power or standby mode. Table 2-Control Board Specifications Description Specification Supply Voltage 6-12 V Input Voltage 2-5 V Input Current.1-.5 ma Output Current.25-1 A Delay Time 5 µs
5 2.3 Converter Specifications The DC-DC converter we are planning to use is called a chopper. The chopper is controlled by an IGBT power electronic switch. The IGBT is repeatedly switched on and off by a voltage pulse. The on time per voltage cycle can be controlled by controlling the on/off time ratio of IGBT, called the duty cycle. If the on time is D, and the IGBT is switched on/off during period T, then the off time is (1-D)*T. The average voltage output [3] is then: [ ] For the purposes of this project, we want to select a voltage that is high enough to be stepped down to a useful level, but still low enough that we do not need to use high voltage equipment. We also want enough power output to do useful work with the output, such as driving a DC motor. Table 3-Converter specifications Description Specification Input voltage 28 V Output voltage 12 24 V Output current 5 A Switching frequency 2-5 khz Figure 3: Chopper circuit with DC motor load [4]
6 3. Milestones Table 3 contains a list of project milestones and tasks, as well as the group members in charge of completing them. A number of administrative tasks are absent from this list, but are listed in the Gantt chart. Table 4-Milestones/task distribution Milestones and Tasks Individuals in charge Research ZigBee communications Jason & Luchen Coding language for µcs DC-DC converter Jason & Luchen Meng Design Design receiver PCB Jason Design transmitter PCB Code implementation DC-DC converter IGBT driver Luchen Jason & Luchen Meng Meng & Brennan Simulation Test receiver design Jason Test transmitter design DC-DC converter Luchen Meng Build Build receiver PCB Jason Build transmitter PCB Code µcs Connect µc to IGBT driver Connect µc to ZigBee transmitter DC-DC converter circuit Luchen Jason & Luchen Brennan Brennan Meng & Brennan Testing Wireless communication Jason & Luchen DC-DC converter circuit Meng & Brennan Implementation and final test Converter control with ZigBee Group
4. Gantt Chart 7
8 5. Budget Table 4 contains a list of required components for our design, as well as associated costs. The costs of shipping and taxes are included in the cost of each component. Our final cost is well below the $400 maximum cost of the project. This gives us $150 to be used for unforeseen costs, such as burnt out parts. Table 5-Proposed Budget Required part Number of parts Cost of parts ZigBee module 2 $80.00 9 volt battery 2 $15.00 PCB 2 $100.00 Passive components TBD $25.00 IGBT 2 $10.00 IGBT driver 1 $5.00 MISC components TBD $15.00 Total $250.00
9 6. References [1] ZigBee Alliance (2013) Specification FAQ [Online] Available: http://www.zigbee.org [Sep. 26, 2013] [2]RF Wireless World (2013) ZigBee Tutorial [Online] Available: http://www.rfwirelessworld.com/tutorials/zigbee_tutorial.html [Sep. 26, 2013] [3]Mohan, Undeland, Riobbins, Power Electronics, 3 rd Edition. Hoboken: Wiley, 2002. [4] Pedro Daniel Dinis Teodoro, Development of a simulation environment of an entertainment humanoid robot, MS Thesis, Dept. Mech. Eng., Instituto Superior Technico, Lisbon, Portugal, 2007.