This document describes a simplified SPICE behavioral model for a maximum peak power tracker (MPPT) and DC/DC converter combination. The model focuses on the input/output relationships rather than circuit details, allowing long-term system simulation over 100 times faster than a cycle-to-cycle model. It is characterized by parameters like efficiency, input/output voltages, and current sensing that represent the converter's behavior. Transient simulations demonstrate how the MPPT tracks the solar cells' maximum power point under changing light intensity conditions.

1. Maximum Peak Power Tracker
(MPPT) + DC/DC Converter
Simplified SPICE Behavioral Model
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2. Contents
1. Model Overview
2. Benefit of the Model
3. Concept of the Model
4. MPPT+DC/DC Specification (Example)
5. Solar Cells Maximum Peak Power
6. Solar Cells System Transient Simulation
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3. 1.Model Overview
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• This MPPT + DC/DC Converter Simplified SPICE Behavioral Model
is for users who require the model of a converter that will be used
with their Photovoltaic system.
• The model focuses on the input/output relationships of the converter
block; therefore, it is not using high frequency models (e.g. oscillator
and noise models), and is not based on the electronic topologies of
the converter.
• The model enables long-term behavior simulation of the system
(e.g. in a Photovoltaic system simulation), which is increased
simulation speed more than 100 times compared to a cycle-to-cycle
model.

4. 2.Benefit of the Model
• Enable its input solar cells to work at their Maximum Power.
• Can be adjusted to your own DC/DC specifications, step-up or step-
down, by editing the model parameters.
• The simplified model is an easy-to-use, which can be provided
without the circuit detail.
• Time and costs are saved because only the necessary parts are
simulated.
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5. 3.Concept of the Model
The model is characterized by parameters n, Vo, Vin_min, Vin_max, and Isns
that represent the input-output-relationships of the converter. Isns is a current
sensing pin that probes the input current (that is the input Solarcells’ current),
together with VMPP the maximum power can be tracked.
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MPPT + DC/DC Converter
Efficiency (n) = POUT / PIN
= VOUT × IOUT / VIN ×IIN
VMPP = Input PV’s Vmp
IN+
Isns
OUT+
OUT-
between VIN,MIN~VIN,MAX )
VOUT (Vdc)
IIN = Input Solarcells’ Imp IOUT
VMPP ( value is
IN-

6. 4.MPPT+DC/DC Specification (Example)
MPPT + DC/DC Converter with VIN=20~30Vdc, VOUT=24Vdc, and
Efficiency=89%
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MPPT + DC/DC Converter
Efficiency (n) = 89%
IN+
Isns
OUT+
OUT-
between VIN,MIN=20V ~
VIN,MAX=30V )
VOUT =24VdcVMPP ( value is
IN-
Rsns=0.1Ω

7. V_ V1
0V 4V 8V 12V 16V 20V 24V 28V
V( U1: PLUS) * I ( Vs ens e)
0W
50W
100W
150W
5.Solar Cells Maximum Peak Power (1/2)
Solar Cells # VBHN120SJ21_130530: Power(W) vs. Voltage(V). The simulation
result shows the maximum power voltage (Vmp) at the different SOL values.
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Temp 25°C
SOL = 1,000W/m2
, Vmp=22.03V
Vmp decreases as SOL(W/m2
) decreases
SOL = 800W/m2
, Vmp=21.72V
SOL = 600W/m2
, Vmp=21.48V
SOL = 400W/m2
, Vmp=21.2V
SOL = 200W/m2
, Vmp=20.3V

8. 5.Solar Cells Maximum Peak Power (2/2)
*Analysis directives:
.DC LIN V_V1 0 26.4 0.01
.STEP LIN V_V3 200 1000 200
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+S O L
T E M P 1
U 1
V B H N 1 2 0 S J 2 1 _ 1 3 0 5 3 _ C S V
0
V 1
0 V d c
V 2
2 5
V 3
1 0 0 0
0
0
V s e n s e
0

9. Ti me
0s 2s 4s 6s 8s 10s 12s 14s
V( O)
0V
20V
40V
W( U1)
- 200W
- 100W
0W
V( MPPT)
20V
22V
24V
V( V3: +)
0V
0. 5KV
1. 0KV
SEL>>
6.Solar Cells System Transient Simulation (1/2)
When SOL(W/m2
) changes the MPPT will track for new maximum peak power
voltage (Vmp) as shown in the simulation result, the Vmp is changed to keep
track on the maximum power position for each SOL value.
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Temp 25°C
SOL = 200W/m2
400W/m2
600W/m2
800W/m2
1,000W/m2
Vmp = 20.35V
21.22V
21.86V
22.37V 22.8V
Pmax = 19.6W
43.6W 67.4W
90.1W 111.4W
VO = 24V

10. 6.Solar Cells System Transient Simulation (1/2)
*Analysis directives:
.TRAN 0 12.32s 0 1000u
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+S O L
T E M P 1
U 1
V B H N 1 2 0 S J 2 1 _ 1 3 0 5 3 _ C S V
M P P T
0
O
0
R 1
1 0 0
R 2
1 0 0
R s n s
0 . 1
V s e n s e _ s o la r c e ll
0
V 2
E : B e e Y 1 4 M P P T c a s e 2 C S V T 2 . c s v
V 3
E : B e e Y 1 4 M P P T c a s e 2 C S V G 2 . c s v
0
0
U 2
M P P T _ D C D C
V I N _ M I N = 2 0
V I N _ M A X = 3 0
N = 0 . 8 9
V O = 2 4
R S N S = 0 . 1
I N +
I N -
O U T +
O U T -
I S N S

11. U 2
M P P T _ D C D C
V I N _ M I N = 2 0
V I N _ M A X = 3 0
N = 0 . 8 9
V O = 2 4
R S N S = 0 . 1
I N +
I N -
O U T +
O U T -
I S N S
7.MPPT+DC/DC: Symbol & Parameters
RSNS is the value of the sensing resistor that is placed between minus pin of
solar cell and ground.
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