Design of Battery Module Tester
Pölönen, Ville-Matti (2018)
2018
Sähkötekniikka
Tieto- ja sähkötekniikan tiedekunta - Faculty of Computing and Electrical Engineering
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Hyväksymispäivämäärä
2018-06-06
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-201805241832
https://urn.fi/URN:NBN:fi:tty-201805241832
Tiivistelmä
Diesel use as fuel is decreasing due to climate change. New replacement power sources are hybrid and fully electric uses to minimize carbon dioxide emissions. The battery modules, which are used for these applications, need to be tested to guarantee their proper operation. The actual testing procedure is not in the scope of this thesis.
The main targets are to compare different alternatives for the power supply, implement the control system and choose the most suitable solution to this study. The maximum power is 75 kW which creates its own challenges to component design. The main parameters are voltage and current. The input fuse, which is connected straight to the grid, must be at least 100 A since the maximum charging and discharging current for the battery modules is 600 A while voltage of the battery modules varies within 24 VDC and 125 VDC depending on the amount of battery modules in series. Isolation from the main grid is important because of harmonics and filtering the common-mode noise. The power flow can be unidirectional or bidirectional in grid perspective. Three alternatives for the power supply structure and control are presented in this thesis.
Since batteries are used, accurate control is a challenge for voltage is low and current high. The control needs to be done carefully, to achieve a stable system. Temperature is a very critical factor, because of lithium-ion batteries. Current and voltage supplied to the battery modules have to be limited on a level which is approved by the manufacturer.
Conventional battery chargers have a constant-voltage constant-current (CCCV) charging method. There are normally two stages in this charging method, the constant cur-rent -phase is applied for most of the charging and as the battery capacity increases close to its maximum, the constant voltage -phase is applied to load the battery fully. Since the tests which are done to the battery modules are based on varying the current reference, only the constant-current charging method with changing reference is deployed. The target is not to charge the battery modules fully, but rather adjust the current.
The thesis starts with an introduction in chapter 1, followed by battery modeling in chapter 2. Batteries are studied in a relevant manner to introduce problems and characteristics in control perspective. Different topologies are considered for the AC-DC interface in chapter 3 and control of the battery module tester is introduced in chapter 4. The control chapter includes pulse-width modulation (PWM), PID-controller and feedback systems. The justifications of the simulation model and component dimensioning are presented in chapter 5. All components used are chosen according to the calculations presented in this thesis. Chapter 6 is about practical issues related to the battery module tester including an optocoupler coupling example and controller design. The last chapter is conclusions wrapping the whole thesis in couple of pages in chapter 7.
The main targets are to compare different alternatives for the power supply, implement the control system and choose the most suitable solution to this study. The maximum power is 75 kW which creates its own challenges to component design. The main parameters are voltage and current. The input fuse, which is connected straight to the grid, must be at least 100 A since the maximum charging and discharging current for the battery modules is 600 A while voltage of the battery modules varies within 24 VDC and 125 VDC depending on the amount of battery modules in series. Isolation from the main grid is important because of harmonics and filtering the common-mode noise. The power flow can be unidirectional or bidirectional in grid perspective. Three alternatives for the power supply structure and control are presented in this thesis.
Since batteries are used, accurate control is a challenge for voltage is low and current high. The control needs to be done carefully, to achieve a stable system. Temperature is a very critical factor, because of lithium-ion batteries. Current and voltage supplied to the battery modules have to be limited on a level which is approved by the manufacturer.
Conventional battery chargers have a constant-voltage constant-current (CCCV) charging method. There are normally two stages in this charging method, the constant cur-rent -phase is applied for most of the charging and as the battery capacity increases close to its maximum, the constant voltage -phase is applied to load the battery fully. Since the tests which are done to the battery modules are based on varying the current reference, only the constant-current charging method with changing reference is deployed. The target is not to charge the battery modules fully, but rather adjust the current.
The thesis starts with an introduction in chapter 1, followed by battery modeling in chapter 2. Batteries are studied in a relevant manner to introduce problems and characteristics in control perspective. Different topologies are considered for the AC-DC interface in chapter 3 and control of the battery module tester is introduced in chapter 4. The control chapter includes pulse-width modulation (PWM), PID-controller and feedback systems. The justifications of the simulation model and component dimensioning are presented in chapter 5. All components used are chosen according to the calculations presented in this thesis. Chapter 6 is about practical issues related to the battery module tester including an optocoupler coupling example and controller design. The last chapter is conclusions wrapping the whole thesis in couple of pages in chapter 7.