Grid-connected solar inverter designed with dsPIC33F

This article introduces the main features of the dsPIC33F series, the series product block diagram and the 220W solar micro inverter reference design connected to the grid, including the main features and indicators, reference design block diagram, design board circuit diagram and bill of materials (BOM).

The dsPIC33F series is a high-performance 16-bit digital signal controller (DSC) that uses an improved Harvard architecture and a C compiler-optimized instruction set. It has a 16-bit wide data bus and 24-bit wide instructions, and an operating speed of 40MIPS at 3.0-3.6V. It is suitable for multi-circuit switching power supplies (SMPS) and other digital power converters such as AC/DC converters, DC/DC converters, power factor correction (PFC), uninterruptible power supplies (UPS), inverters, embedded power controllers and digital lighting.

High-Performance 16-bit Digital Signal Controller Main Features:

Operating Range:

• Up to 40 MIPS operating speed (at 3.0-3.6V):

- Industrial temperature range (-40℃ to +85℃)

- Extended temperature range (-40℃ to +125℃)

High-Performance Digital Signal Controller (DSC) CPU:

• Modified Harvard architecture

• C compiler optimized instruction set

• 16-bit wide data bus

• 24-bit wide instructions

• Addressable linear program memory space of up to 4M instruction words

• Addressable linear data memory space of up to 64 KB

• 83 basic instructions: most of them are single-word/single-cycle instructions

• Two 40-bit accumulators with rounding and saturation options

• Flexible and powerful addressing modes:

- Indirect addressing

- Modulo addressing

- Bit-reversed addressing

• Software stack

• 16 x 16-bit fractional/integer multiplication

• 32/16-bit and 16/16 Bit-wise division operation

• Single-cycle multiply-accumulate operation:

- Accumulator write-back operation for DSP operations

- Dual data fetch operation

• Up to 40 bits of data can be shifted left or right by up to 16 bits

Digital I/O:

• Peripheral pin select capability

• Up to 35 programmable digital I/O pins

• Wake-up/interrupt-on-change capability on up to 30 pins

• Output pins can drive 3.0V to 3.6V

• Open-drain configuration, up to 5V output

• Digital input pins are 5V tolerant (except RB5)

• All PWM pins source/sink 16 mA On-chip Flash and SRAM:

• Flash program memory (up to 16 KB)

• Data SRAM (up to 2 KB)

• Boot and general security for Flash program memory Peripheral Features:

• Timer/Counter, up to 3 16-bit timers

- can be paired up to 1 32-bit timer

• Input capture (up to 2 channels):

- Capture on rising, falling, or rising/falling edges

- 16-bit capture input capability

- 4-level deep FIFO buffer for each capture channel

Output Compare (up to 2 channels):

- Single or double 16-bit compare modes

- 16-bit glitch-free PWM mode

4-wire SPI:

- Frame support for I/O interface with simple codecs

- 1-level deep FIFO buffer

- Supports 8-bit and 16-bit data

- Supports all serial clock formats and sampling modes

I2C™:

- Full multi-master slave mode support

- 7-bit and 10-bit addressing

- Bus collision detection and arbitration

- Integrated signal conditioning

- Slave address masking

UART:

- Interrupt on address bit detection

- Interrupt on UART error

- Wake-up from Sleep on Start bit detection

- 4-character deep transmit and receive FIFO buffers

- LIN bus support

- Hardware IrDA® encoding and decoding

- High-speed baud rate mode

- Uses CTS and RTS Hardware flow control

Interrupt controller:

• 5-cycle interrupt latency

• 118 interrupt vectors

• Up to 35 interrupt sources

• Up to 3 external interrupts

• 7 programmable priority levels

• 4 processor exceptions

High-speed PWM module features:

• Supports up to 4 PWM generators, providing 4-8 outputs

• Each of the 8 PWM outputs has an independent time base and duty cycle

• Rising and falling edge dead band

• Duty cycle resolution is 1.04 ns

• Dead band resolution is 1.04 ns

• Phase shift resolution is 1.04 ns

• Frequency resolution is 1.04 ns

• Supported PWM modes:

- Standard edge alignment

- True independent output

- Complementary

- Center alignment

- Push-pull

- Multi-phase

- Variable phase

- Fixed off-time

- Current reset

- Current limit

• Independent fault/current-limit inputs for eight PWM outputs

• Output override control

• Special event trigger

• PWM capture function

• Prescaler for input clock

• Dual trigger signals from PWM module to ADC (analog-to-digital converter, ADC)

• PWMxL and PWMxH output pin swapping

• PWM4H and PWM4L pins can be remapped

• PWM frequency, duty cycle, and phase shift can be changed on the fly

• Disable of each individual PWM generator

• Leading-Edge Blanking (LEB) function High-Speed ​​Analog Comparators

• Up to four analog comparators:

- 20 ns response time

- 10-bit DAC associated with each analog comparator

- DACOUT pin for DAC output

- Programmable output polarity

- Selectable input signal source

- ADC sample and convert function

• Interface to PWM module:

- PWM duty cycle control

- PWM period control

- PWM Fault Detection

High-Speed ​​10-Bit ADC

• 10-Bit Resolution

• Up to 12 Input Channels Grouped into 6 Conversion Pairs

• Two Internal Reference Voltage Monitor Inputs Grouped into a Pair of Internal Analog Inputs

• Successive Approximation Register (SAR) Converters for Parallel Conversion of Analog Input Pairs:

- 4 Msps for Devices with Two SARs

- 2 Msps for Devices with One SAR

• Dedicated Result Buffer for Each Analog Channel

• Independent Trigger Source for Each Analog Input Conversion Pair

Power Management:

• On-Chip 2.5V Regulator

• Real-Time Clock Source Switching

• Idle, Sleep, and Doze Modes with Fast Wake-Up

CMOS Flash Technology:

• Low-Power, High-Speed ​​Flash Technology

• Fully Static Design

• 3.3V (±10%) Operating Voltage

• Industrial and Extended Temperature

• Low Power

System Management:

• Flexible Clock Selection:

- External Oscillator, Crystal, Resonator, and Internal RC Oscillator

- with 120 MHz Phase-Locked Loop (PLL) with Voltage Controlled Oscillator (VCO)

- Main crystal in the range of 3 MHz to 40 MHz

- Internal Low-Power RC (LPRC) oscillator at 32 kHz

- Internal Fast RC (FRC) oscillator at 7.37 MHz

• Power-on Reset (POR)

• Brown-out Reset (BOR)

• Power-up Timer (PWRT)

• Oscillator Start-up Timer (OST)

• Watchdog Timer with its own RC oscillator

• Fail-Safe Clock Monitor (FSCM)
• Multiple reset sources

• In-Circuit Serial Programming™ (ICSP™)

Packages:

• 18-pin SOIC

• 28 Pin SPDIP/SOIC/QFN-S

• 44-pin TQFP/QFN


Figure 1. dsPIC33F Family Block Diagram Grid-Connected Solar Micro Inverter Reference Design This reference design demonstrates the flexibility and power of SMPS dsPIC®

Digital Signal Controllers in Grid connected power conversion systems. This reference design works with any photovoltaic (PV) panel of maximum 220 Watts having open circuit voltage between 25V to 55V DC. This reference design ensures maximum power tracking for PV panel voltage between 25V to 45V DC. Two versions of this reference design is available to support 110V and 220V Grid. Figure 2. Grid-Connected Solar Family Block Diagram







This reference design is implemented using a single dsPIC33F “GS” digital-power DSCs from Microchip that provides the full digital control of the power conversion and system management functions. As shown in this reference design the dsPIC33F 'GS' devices enable designers to easily and cost effectively create products using advanced switching techniques that lower switching losses and enable efficiencies as high as 95%. Grid-Connected Solar

Micro Inverter Reference Design is royalty free when used in accordance with the licensing agreement. Main design features:

Peak efficiency of 95%

Output current THD < 5%

Power factor >0.95

Maximum power point tracking

Grid voltage and frequency tracking

Protection against various current and voltage faults

Night time power consumption <1W

System Islanding to detect grid failure

Full Digital Control

Grid-connected solar microinverter reference design specifications:

Micro Inverter for individual PV Module up to 220W

Wide PV Panel voltage : 25V to 55V DC

Maximum Power Point Tracking voltage: 25V to 45V

Maximum DC short circuit current: 10A

Grid Frequency range:

47 – 53 Hz for 220V systems

57 – 63 Hz for 110V systems

Grid voltage range:

90V – 140V for 110V systems

180V – 264V for 220V systems

230V solar micro-inverter system specifications :

• Maximum output power = 185 watt

• Nominal output voltage = 230V

• Nominal output current = 0.8A

• Output voltage range = 180 VAC-264 VAC

• Output frequency nominal frequency = 50 Hz

• Output frequency range = 47 Hz-53 Hz

• Power factor = >0.95

• Total harmonic distortion = <5%

• Efficiency

- Peak efficiency = 95%

- Maximum Power Point tracking = 99.5%

- Minimum efficiency>0.8

110V Solar Micro Inverter System Specifications:

• Maximum output power = 185 watt

• Nominal output voltage = 110V

• Nominal output current = 1.7A

• Output voltage range = 90 VAC-140 VAC

• Output frequency nominal frequency = 60 Hz

• Output frequency range = 57 Hz-63 Hz

• Power factor = >0.95

• Total harmonic distortion = <2%

Figure 3. Grid-connected solar microinverter reference design outline

Figure 4. Grid-connected solar microinverter reference design block diagram (1)

Figure 5. Grid-connected solar micro-inverter reference design block diagram (2)

Figure 6. Grid-connected solar micro-inverter reference design board outline Figure

7. Grid-connected solar micro-inverter reference design board Circuit diagram (1)

Figure 8. Grid-connected solar microinverter reference design board circuit diagram (2)

Figure 9. Grid-connected solar micro-inverter reference design board circuit diagram (3)

Figure 10. Grid-connected solar micro-inverter reference design board circuit diagram (4)

Figure 11. Grid-connected solar micro-inverter reference design board circuit diagram (5 ）