Huawei SDS User Manual

Jointly issued by: National Energy Key Laboratory for Wind and

Solar Simulation, Testing and Certification, China General

Certification Center, and Huawei Technologies Co., Ltd.

November 2020

White Paper on SDS Intelligent

Joint Control Technology for

Inverters and Trackers

C

urrently, the smart DC system (SDS), an
intelligent joint control technology for inverters
and trackers developed by Huawei Technologies

Co., Ltd. (hereinafter referred to as "Huawei"),
has entered the large-scale application phase. Entrusted
by Huawei, China General Certification Center (CGC) has
carried out a comprehensive review and verification of
the SDS to verify its technical performance and
application effect. Based on the review and verification

results, the National Energy Key Laboratory for Wind

and Solar Simulation, Testing and Certification, CGC,
and Huawei jointly released the

White Paper on SDS
Intelligent Joint Control Technology for Inverters and
Trackers

. This white paper describes the development
background, technical features, and application effects of
the SDS in detail, helping the industry comprehensively
and deeply understand the technology.

Preface

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White Paper on SDS Intelligent Joint Control Technology
for Inverters and Trackers

01

Technology Development Background

The trackers have been used for a long time, but the
following issues may also exist in actual applications:

Traditional astronomical algorithms are used, in which
the impact of terrain conditions, blocking in the
morning and evening, and weather changes is not fully
considered. Due to miscalculations of the optimum
tracking angle, energy yield loss may occur in some
time periods and in special weather conditions. Figure
1-2 and Figure 1-3 show the examples.

Figure 1-2 Examples of shading between arrays in special

areas and in the morning and evening

Continuously improving the efficiency of PV power
systems is a sedulous pursuit in the industry. For this
purpose, at the device end, the main goal is to
improve the optical-to-electrical conversion efficiency
of PV modules and reduce the energy loss of other
devices. At the system end, the main goal is to
increase the radiation received at the surface of the
PV modules and reduce the efficiency loss.

In recent years, the efficiency improvement
achievements at the device end are remarkable, but
there is not much room for improvement.

The industry has shifted the focus on the system end.
The application percentage of various technologies,
especially the tracking technology, is increasing, aiming
to improve the radiation received by the PV module
surface. Figure 1-1 shows the application percentage of
trackers in bases of the second and third phases of PV
Forerunner, a PV demonstration project initiated by
National Energy Administration, in China. The figure
indicates that the application percentage of trackers
increased significantly in the third batch of bases. In
addition, according to the data released by GTM, the
shipments of trackers in 2017, 2018, and 2019 increased
by 34%, 36%, and 66% year on year. In 2019, the global
shipment of trackers was about 35 GW.

Total Installed
Capacity (MW)

600

500

400

300

200

100

0

70%

60%

50%

40%

30%

20%

10%

0%

Ruicheng

(Phase 2, 2017)

Xintai

(Phase 2, 2017)

Sihong

(Phase 3, 2018)

Dalad

(Phase 3, end of 2018)

13%

24%

33%

60%

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White Paper on SDS Intelligent Joint Control Technology
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Figure 1-1 Comparison of application scale and percentage of trackers

in the second and third batches of PV Forerunner bases (partially)

Tracker Installed
Capacity (MW)

Tracker Installation
Percentage

(1) Most tracking system algorithms are provided

by the tracker manufacturer.

(MV)

Figure 1-3 Difference of received radiation at

different angles on cloudy weather

As mentioned above, with the improvement of

reliability and cost-effectiveness, the application
percentage of the trackers, including the power
generation technology using the combination of
trackers and bifacial PV modules, will gradually
increase.

(2) To solve the problems in common astronomical

algorithms, the backtracking technology is used in
the industry. However, the tracker angle control is
relatively independent and is not associated with
the I-V perception or change of the PV strings or
control units. Therefore, refined adjustment or
precise control cannot be implemented.

(3) In recent years, the power generation technology

using the combination of trackers and bifacial PV
modules has become one of the mainstream
forms. This kind of system needs to dynamically

adjust the control policy according to the change

of external conditions. Figure 1-4 compares the
daily cumulative radiation of the front and rear
sides of a random 15-day period selected from the

3-month monitoring data of the CGC Inner Mongolia
empirical research system (horizontal single axis and
bifacial PV module power generation).

As shown in Figure 1-4, the ratio of the radiation
received from the front side to that from the rear side
varies greatly due to the weather. In special weather
conditions, the daily accumulated radiation on the rear
side is even higher than that on the front side. This
means that the angle of the PV modules needs to be
dynamically optimized and adjusted based on the
weather conditions for the bifacial tracking power
generation system, maximizing the control unit output.

Ratio of Daily Received Radiation on the
Front Side to the Reference Value

Ratio of Daily Received Radiation on the Rear Side to
Received Radiation on the Front Side on the Current Day

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

0

D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11 D12 D13 D14 D15

Ratio

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White Paper on SDS Intelligent Joint Control Technology
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Figure 1-4 Comparison of daily accumulated radiation on

the front and rear sides (horizontal single axis)

To solve the issues in the application of the trackers,
the big data and AI technologies are used to optimize
the inverter and tracker control linkage, further
improving the increase effect of the trackers. This has

become one of the development directions of the

tracking technology.

02

Technology Description

Figure 2-2 Logical block diagram of algorithm

design and angle optimization

Figure 2-1 and Figure 2-2 show the SDS block diagram, and logical block diagram of algorithm design and angle
optimization, respectively.

Figure 2-1 SDS block diagram

Signal Flow
Drive Signal

SmartLogger

WebUI

Inclination sensor

SmartLogger Inverter Tracking controller

Tracker motor

SmartPVMS (in

and outside China)

The SDS technology developed by Huawei has the
following features:

(1) The inverter is linked with the tracker control system

and performs closed-loop control to ensure that the
system runs with the maximum radiation volume
received by PV modules and optimal power output.

(2) No additional sensor device is required. AI technologies

are used to automatically detect shading and weather
changes and automatically optimize and control the
tracking angle, eliminating manual operations and

experience dependence.

(3) The inverter integrates the tracker communication

and power supply functions and the tracker power
supply cables and communication cables are
reduced thanks to MBUS.

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03

Technical Review and Application
Effect Verification

The SDS technology developed by Huawei is applicable
to monofacial and bifacial power generation systems in
tracking mode. This technology takes into account the
factors that affect the maximum utilization of solar
resources and the optimal power output under
different time points, weather, topography, and

installation conditions. By using the AI technology, the

energy yield of the tracking system is further improved
through the I-V perception of the inverter and the
linkage and closed-loop control with the tracker
control unit.

After the review, the verification team concludes
that the SDS technology developed by Huawei
complies with clear and specific technical
principles, the technical solution is reasonable and

feasible, the application cost is low, and the

increase effect is obvious.

3.1 Technical Review

To deeply understand the status and application effect
of Huawei SDS, entrusted by Huawei, a CGC
verification team was established to comprehensively
verify and evaluate Huawei SDS from February to May,

2020.

Figure 3-1 shows a block diagram of the verification

and evaluation process and contents.

Figure 3-1 Block diagram of the verification and evaluation process and contents

Review contents:

• SDS technical

principles, design
solutions, process

routes, and software

and hardware
configurations

Review purpose:

• Determine whether

the SDS is advanced,
feasible, and
reasonable.

Technical Review

Evaluation contents:

• Evaluate the increase

effect of the SDS in
different application

conditions and periods

through cases.

Evaluation purpose:

• Determine the SDS's

capability of achieving
the expected
objectives, application
scenarios, impact
factors, and
application costs.

Result Evaluation

Verification contents:

• Increase effect in the

test period; SDS angle
optimization

capability and control

precision; and running
status of SDS-related
devices

Test purpose:

• Determine the SDS's

capability of
identifying, optimizing,
and controlling various
factors and the
technology maturity.

Onsite Verification

Appraisal content:

• Whether the SDS is

advanced, feasible,
and reasonable

• Technical adaptability

and capability of
achieving expected
objectives

• Automatic

optimization and
control capabilities,
and technology
maturity

Overall Appraisal

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White Paper on SDS Intelligent Joint Control Technology
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Note: The trackers of the inverters numbered 503 and 504 use the common algorithm, and the trackers
corresponding to the inverters numbered 501, 502, 303, and 304 use the SDS algorithm. Inverters numbered 401,
402, 403, and 404 are not involved because they are installed in greenhouses and have different ground albedos.

Figure 3-3 Layout of the verification arrays

Figure 3-2 PV plant panoramas

3.2 Long-Term Application Effect
Verification and Evaluation

To verify the application effect of the SDS, two sample
PV plants were selected from the PV plants where
Huawei SDS technology was applied for demonstration,
and were tracked for a long time. The two PV plants
are located in Suixi County, Anhui Province (plant A)
and Luchuan County, Guangxi Province (plant B)
respectively. Plant A uses a bifacial horizontal single­axis tracking system, while plant B uses a monofacial
horizontal single-axis tracking system.

Long-Term Application Effect
Verification and Evaluation on Plant A

Figure 3-2 shows the PV plant panoramas, and Figure 3­3 shows the layout of the verification arrays.

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The project verification period is from July 2019 to
June 2020. July 2019 is the performance deviation
comparison test period between different arrays while
the common algorithm is used. The differences of
basic energy yields of arrays are collected as the
reference baseline. The comparison and verification
started in August 2019.

Figure 3-5 shows the monthly energy yield comparison
of the arrays. Figure 3-6 shows the energy yield
increase percentage of the SDS arrays after the
performance deviation is corrected.

Figure 3-5 Comparison of specific energy per month

between SDS arrays and common arrays

Calculation method for monthly energy yield increase:

Array energy yield after the SDS is used/Common array
energy yield – Baseline energy yield difference before
the SDS is used

During the entire verification period, the energy
yield of the arrays using the SDS algorithm
increases by 1.50%. In January 2020 when there
are many rainy days and scattering occurs
frequently, the energy yield of the SDS arrays
increases by 3.09%. In addition, in the months
with the smaller the solar elevation angle and the
greater the proportion of scattering light, the
more obvious the increase effect.

Figure 3-6 Monthly increase rate of the SDS arrays compared with the common arrays

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(kWh/kWp)

Long-Term Application Effect
Verification and Evaluation on Plant B

Figure 3-7 shows the PV plant panoramas, and Figure

3-8 shows the layout of the verification arrays.

Figure 3-7 PV plant panoramas Figure 3-8 Layout of the verification arrays

Note: The trackers of the inverters numbered 1, 2, 3, 4, 9, and 16

use the common algorithm, and the trackers of the inverters
numbered 6, 7, 8, 11, 12, and 14 use the SDS algorithm.

The project verification period is from April 2019 to June

2020. April to June 2019 is the performance deviation
comparison test period between different arrays while the
common algorithm is used. The comparison and verification
started in July 2019.

Figure 3-9 Comparison of specific energy per month between SDS arrays and common arrays

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Figure 3-9 shows the monthly energy yield
comparison of the PV arrays. Figure 3-10 shows
the energy yield increase percentage of the SDS
arrays after the performance deviation is
corrected.

(kWh/kWp)

Calculation method for monthly energy yield increase:

Array energy yield after the SDS is used/Common
array energy yield – Baseline energy yield
difference before the SDS is used

During the entire verification period, the energy
yield of the arrays using the SDS algorithm
increases by 1.43%. In March 2020 when there are
many rainy days and scattering occurs frequently,
the energy yield of the SDS arrays increases by

3.58%. In addition, in the months with the smaller
the solar elevation angle and the greater the
proportion of scattering light, the more obvious the

increase effect.

Figure 3-10 Increase rate

3.3 Onsite Verification

To further verify the increase effect and mechanism of

the SDS, plant A is tested based on the relationship of
"Angle – Radiation – Operating current – Output power".
A detection team dispatched by CGC performed onsite
comparison tests of the increase factors from September
16 to 23, 2020.

The onsite test scenarios include two weather
conditions: sunny and rainy. The following figure shows
the sample units selected during the test. The units
marked in red are SDS units, and the units marked in
yellow are common units. The comparison test data of
motor 5 (SDS) and motor 2 (common) is used for
scenarios 1 and 2.

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Note: The greenhouse area is not involved.

Scenario 1: sunny days

Verification focus: SDS control policy and effect for time-specific shading between arrays

Figure 3-11 shows the weather conditions of the current day and the inter-array and time-specific shading between
common arrays.

Figure 3-11 Weather conditions and time-specific shading between arrays

Figure 3-12 shows the position of the irradiation sensor for monitoring.

Figure 3-12 Position of the irradiation sensor

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Figure 3-14 Comparison of irradiance between SDS arrays and common arrays (front + rear sides)

Figure 3-15 Comparison of the operating current (average value) between SDS arrays and common arrays

Figure 3-13 Comparison of tracker angles

Figure 3-13, Figure 3-14, Figure 3-15, and Figure
3-16 show the trend of changes of SDS array
and common array tracker angles, irradiance on
the tilted surfaces (front + rear sides), and

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array output power in different time
periods based on the monitoring results
within 18 days (whole days).

Figure 3-16 Comparison of inverter average output power between SDS arrays and common arrays

Figure 3-17 Comparison of accumulated energy yields between SDS arrays and common arrays

As shown in the preceding figures, the SDS avoids

inter-array shading by adjusting the tracking angle
in the morning and evening. Compared with
common arrays, in a corresponding time period, the
irradiance on the tilted surfaces, branch average
operating current, and array output power of the
SDS arrays are improved, and changes of different
parameters are highly consistent. This indicates that
the SDS can improve the received irradiance on the
tilted surfaces by optimizing the tracking angle in
sunny weather conditions, thereby improving the
operating current of the PV strings and the output
power of the arrays.

Figure 3-17 shows the comparison of the accumulated
energy yields of inverters on the current day between
SDS arrays and common arrays. According to the

statistics, the energy yield gain rate of the SDS arrays

is 1.58% on the whole day. The energy yield gain
rate is 6.86% from startup time to 9:00, and is

11.69% from 16:30 to shutdown time. This indicates
that the energy yield gain is mainly reflected in the
morning and evening in sunny days.

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Scenario 2: rainy days or days when scattering frequently occurs

Verification focus: control policies and effects of the SDS on this kind of weather Figure 3-18 shows

the weather of the current day.

Figure 3-18 Weather

12:00 14:30

Figure 3-19 Comparison of tracking angle between SDS arrays and common arrays

Figure 3-19, Figure 3-20, Figure 3-21, and

Figure 3-22 show the trend of changes of SDS

array and common array tracker angles,
irradiance on the tilted surfaces (front + rear
sides), and array branch

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operating current (average value), and array output
power in different time periods based on the
monitoring results within 21 days (whole days).

Sudden jumps due to
blocking and cloudy days

Figure 3-20 Comparison of irradiance on the tilted surfaces (front + rear sides) between SDS arrays and common arrays

Figure 3-21 Comparison of the operating current (average value) between SDS arrays and common arrays

Figure 3-22 Comparison of the inverter power (average value) between SDS arrays and common arrays

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Figure 3-23 Comparison of the accumulated energy yields of inverters between SDS arrays and common arrays

As shown in the figures, the SDS optimizes and adjusts

the tracking angle for all time in rainy days or days
when scattering frequently occurs. Compared with
common arrays, the irradiance on the tilted surfaces
, branch average operating current, and array output
power of the SDS arrays are improved in multiple
time periods, and changes of different parameters
are highly consistent. This indicates that the SDS can
improve the received irradiance on the tilted
surfaces by optimizing the tracking angle in this
kind of weather conditions, thereby improving the
operating current of the PV strings and the output
power of the arrays.

Figure 3-23 shows the comparison of the accumulated
energy yields of inverters on the current day between
SDS arrays and common arrays. According to the
statistics, the energy yield gain rate of the SDS

arrays is 5.10% on the whole day. Compared with
common arrays, the energy yield gain ratio of the
SDS arrays is increased in multiple time periods.

3.4 Overall Appraisal

Based on the technical review and verification results,

(1) The SDS technology developed by Huawei has been

verified for a long time and has entered the large­scale application phase. It can be widely used in PV
power systems that use trackers. This technology
makes full use of the core function of the inverters.
The solution used is designed based on the logical
framework of "comprehensive monitoring or

perception of environment and operating parameters

– Optimal tracking angle – Maximum and balanced
received radiation – Optimal output parameters". The
closed-loop control with the tracker control unit
solves the deficiencies in the prior art, and further
improves the technical efficiency of the trackers.

(2) The technical solution adopted by the SDS is

scientific and reasonable, and has obvious operation
effect. According to the comparison and verification
results of the two sample plants in the past year,
the SDS increase rate reaches 1.50% and 1.43%
respectively. Based on the short-term comparison
test results, the SDS can implement the design

function of automatic monitoring or perception, and

automatic optimization and control. The control and
operation effects meet the expectation, especially in
the early morning, evening, and special weather
conditions.

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