Line-interactive UPS on Arduino - Part 2. Controller core. 

Arduino IDE

Arduino Nano

<html><body>This is the continuation of the article on the <a href="https://projecthub.arduino.cc/abratchik/line-interactive-ups-on-arduino-part-1-bcd89b">Arduino-based line-interactive UPS </a>. In the previous chapter, we briefly touched upon the concept of the UPS and its components. Now let's have a deep dive into the UPS Controller. The schematic diagram of the controller is represented below: <figure><img src="https://projects.arduinocontent.cc/307cf5a9-3d2a-4f6c-b9ad-9e10623467bf.png"/><figcaption></figcaption></figure>The diagram is drawn around the core chip of the Arduino Nano board (Atmega 328P). For the sake of clarity, I'm omitting all other circuitry of the Arduino Nano board, which is non-essential for understanding. The mapping between the chip and the board pins and explanation of the inputs and outputs is as follows: <figure><img src="https://projects.arduinocontent.cc/9f4f9d3a-3f7c-4695-9f59-fb2ad0d8c580.png"/><figcaption></figcaption></figure>Transistors U8, U9 are working as repeaters of the PWM charge managing signal. The lines CH1 and CH2 are to be connected to the MOSFET drivers (U1, U3) on the EGS002 board so that the lower part of the H-bridge could charge and maintain the battery when the UPS is connected to the AC mains. The fragment of the EGS002 schematic below shows where the CH1 and CH2 need to be connected: <figure><img src="https://projects.arduinocontent.cc/19390195-8d5f-446d-bdfc-dc9a4a44a18b.png"/><figcaption></figcaption></figure> As mentioned above, the charging is activated only when the inverter is off (EG8010 chip is disabled, SPWMEN ( managed through INV signal from the UPS controller) is set to low). In this case, the transistors U8, U9 are working as emitter repeaters forming the PWM signal on the resistors R31, R35 of the inverter. When the inverter is on, the CH_PWM output is set to LOW so the transistors U8, U9 remain closed thus having no effect on the its logic. <h3>Line-interactive logic implementation concepts</h3>The core logic of the line-interactive UPS is implemented within the main Arduino cycle ( <code class="code">loop() </code>function). The loop is non-blocking - that is, no delays are allowed. The switching between the modes of the UPS is happening based on the sensor values and external commands, which are received through the Serial RX/TX line. In order to meet de-facto industry standards, the serial communication with the UPS Core controller is implemented in accordance with the <a href="https://networkupstools.org/protocols/voltronic.html#line-mode">Voltronic protocol </a>, with some minor extensions and modifications, which we will discuss in subsequent chapters. Sensors are polled and display is refreshed using the Timer 0 of the Atmega chip. The timer is configured for 490Hz, which is the discretization frequency for all the analog signals such as input and output AC voltages. Timer 1 is used to generate the PWM signal for charging. <h3>Previous chapters</h3><a href="https://projecthub.arduino.cc/abratchik/line-interactive-ups-on-arduino-part-1-bcd89b">Line-interactive UPS on Arduino - Part 1 </a><h3>To be continued ...</h3> </body></html>

Line-interactive UPS on Arduino - Part 2. Controller core.

Line interactive UPS core controller on Arduino Nano