EMC’14/Tokyo
15P-B3
CISPR limits for the Conducted Disturbances
of DC ports of PV-GCPCs
Yasutoshi Yoshioka
Technology Development Dept.
Corporate R&D Headquarters, Fuji Electric Co., Ltd.
Abstract— This paper reports standardization activities in
CISPR and introduces newly developed limits and measurement
method of conducted disturbances at the DC ports of Grid
Connected Power Converters (GCPCs) applied to solarphotovoltaic power (PV) generating systems. First, background
of standardization activities on the development of the limits and
measurement method is described. Second, the two proposals on
the measurement method and the two approaches for the
derivation of the limits are reported. Third, the derivation of the
limits based on the two approaches is shown in detail. Finally, the
process of reaching an agreement in respect of the limits is
reported, and the derived limits are shown.
Keywords—Internatinal standard; CISPR; Grid Connected
Power Converters; DC ports; disturbance voltage
I.
INTRODUCTION
Grid connected power converters (GCPCs) are
indispensable components for solar-photovoltaic (PV) power
generating systems in order to feed DC electric power energy
generated by PV modules into AC mains networks or loads.
On the other hand, there are concerns that GCPCs cause
electromagnetic (EM) disturbances due to switching operation
of semiconductor switching devices which make up GCPCs.
Limits of electromagnetic disturbance are prescribed by the
International Special Committee on Radio Interference
(CISPR). However, there were not an international standard
regarding EM disturbances for GCPCs applied to PV systems.
CISPR has been considering the limits and measurement
method of EM disturbance caused by GCPCs since 2008 and
issued two drafts of standards regarding conducted
disturbances at DC ports of GCPCs in 2012. This paper reports
standardization activities in CISPR and introduces newly
proposed limits and measurement method of conducted
disturbances at the DC ports of GCPCs.
II.
the AC mains network. The GCPC consists of semiconductor
switching devices in order to convert DC to AC. Switching
operation of the devices causes radiated emissions from GCPC
itself and conducted emissions from the AC ports of GCPC as
well as its DC ports. The conducted emissions cause radiated
disturbances due to an antenna effect of cables, and there are
some concerns that PV modules and DC cables show a large
antenna effect.
B. New work item proposal in CISPR
CISPR requires that all of electrical equipments should
control conducted and radiated emissions for the protection of
radio services. However, CISPR did not prescribe the limits
and measurement method of conducted and radiated emission
generated by the PV systems, and one of Japanese experts
proposed to start considerations of the development of those in
about 2004 at the CISPR sub-committee B meeting. CISPR/B
has responsibility for standardization in the field of limits and
particular methods of measurement for control of radio
frequency disturbances from industrial, scientific and medical
electrical equipment. CISPR11 is an international standard
which has been published by CISPR/B and covers emission
requirements related to radio-frequency (RF) disturbances in
the frequency range of 9 kHz to 400 GHz.
CISPR/B realized that limits of radiated emissions and
conducted emissions at AC power ports prescribed in CISPR11
could be applicable for the PV system, but that the CISPR11
has not specified the limits and measurement method of
conducted emissions at the DC ports of GCPC which causes
radiated disturbances to the radio services. Therefore, CISPR/B
has stared the maintenance of CISPR11 regarding conducted
disturbances at the DC ports of GCPC since 2008. A
maintenance team has been also established since then.
BACKGROUND OF STANDARDIZATION ACTIVITIES
A. Electromagnetic disturbances cuased by GCPCs
Fig.1 shows a simple configuration diagram of a PV system.
The PV system consists of PV modules which generates DC
electric power energy and GCPC which converts the DC
electric power energy to the AC. The PV modules are
connected by electrical cables to DC ports of GCPC. AC ports
of GCPC are connected by electrical cables to AC mains
network to feed the converted AC electric power energy into
Copyright 2014 IEICE
585
Fig. 1. Simple diagram of a photovoltaic power generating system
EMC’14/Tokyo
15P-B3
Tasks of the maintenance team are the development of the
limits of disturbance voltage at the DC ports and a test method
to measure disturbance voltage at the DC ports.
III.
STANDARDIZATION ACTIVITIES IN CISPR/B
A. Measurement method of disturbance voltage
Fig. 2 shows simple circuit diagram for the measurement of
disturbance voltage at the AC and DC ports of GCPC. It was
agreed that both the DC and AC ports were terminated with
artificial networks to provide the defined termination
impedance at the respective ports and decoupling networks
which could protect these terminations from disturbances
generated by the laboratory DC power source and the
laboratory AC mains within the desired frequency range.
Japanese experts proposed to use the existing artificial
delta-network for the measurement of common mode (CM)
disturbance voltage at the DC ports. That is because they
considered that CM conducted emission predominantly caused
radiated disturbance and needed to be controlled to mitigate it.
On the other hand, German experts proposed to use the newly
developed artificial delta-network, which is described in [1],
for the measurement of unsymmetrical mode (UM) disturbance
voltage at the respective DC port which is voltage between the
respective DC port and a specified ground reference. That is
because they considered that conducted emission at the AC
ports was assessed with UM disturbance voltage, and
conducted emission at the DC ports needed to be assessed in
the same way as that at the AC ports.
Japanese experts commented that the conducted emission at
the AC ports needed to be controlled to protect the radio
services from both conducted and radiated disturbance, but the
conducted CM emission at the DC ports needed to be
controlled in order to protect the radio services from only
radiated disturbance caused by the conducted CM emission.
That is because equipment for radio services was not connected
to the DC ports of GCPC. Eventually, they agreed that the
choice of the artificial network used for the measurement of
disturbance voltage at the DC ports was left to the discretion of
the user of CISPR11. Japanese experts agreed that differential
mode (DM) disturbance voltage should be measured as well as
CM, and they accepted that compliance with CISPR11 should
be verified for measured disturbance voltage of both modes.
approach in order to use the newly developed artificial deltanetwork for the measurement of UM disturbance voltage at the
DC port. This approach was proposed by the German experts.
The second approach is the current-to-voltage conversion
approach in order to use the existing artificial delta-network for
the measurement of CM disturbance voltage at the DC ports,
and this approach was proposed by the Japanese experts.
The proportional relation approach assumes that GCPC
floats completely to the ground and that there is perfect
coupling in between the AC and DC ports of the GCPC. Under
this assumption, it is expected that the CM current flows
through the termination impedances of the AMN and the DCAN as shown in Fig.3. The relational expression of CM
disturbance voltage at the AC ports and the DC ports can be
derived simply according to the proportional relation of the
CM impedances of the AMN and the DC-AN as in (1).
According to (1), German experts proposed (2) in order to
derive the limits of UM disturbance voltage at the DC ports by
referring to the existing limits of UM disturbance voltage at the
AC port prescribed in CISPR11.
VCM-DCAN / VCM-AMN = ZCM-DCAN / ZCM-AMN
(1)
VLimit-DCAN = VLimit-AMN (ZCM-DCAN / ZCM-AMN)
(2)
However, the derived set of limits of disturbance voltage at
the DC ports is affected by the number of the AC ports because
the value of the CM impedance at the AC ports varies with the
number of the AC ports. For example, a set of limits of
disturbance voltage at the DC ports of a single-phase GCPC is
different from that of a three-phase/four-wire GCPC.
The current-to-voltage conversion approach allows for
consideration of the GCPC as a black box as shown in Fig 4
and derives the limits of conducted disturbance voltage of the
DC ports by considering only the CM emission current Idc
flowing from the DC port to the CM termination impedance of
the DC-AN. The DC-AN provides the defined CM termination
impedance, and if a set of the limits of the CM emission
currents is given, this approach can derive a single set of the
limits of CM disturbance voltage by multiplying the CM
current by CM impedance. This approach can derive only a
single set of the limits of conducted disturbance voltage at the
DC ports even if the GCPCs have different numbers of AC
ports. Moreover, even for the GCPC which has multiple DC
ports as shown in Fig. 5, only a single set of the limits can be
developed with the current-to-voltage conversion approach.
Fig. 2. Simple circuit diagram for the measurement of disturbance voltage
B. Approaches for the derivation of the limits
Two approaches for developing the limits of conducted
disturbance voltage at the DC ports of GCPC have been
proposed. The first approach is the proportional relation
Copyright 2014 IEICE
Fig. 3. Common mode current path for the propotional relation approach
586
EMC’14/Tokyo
DC
Power
Supply
15P-B3
DC-ports
DC-AN
Decoupling
Network
ZCM-DCAN
AC-ports
GCPC
AMN
Decoupling
Network
Black Box
Iac
Idc
impedance of the newly developed artificial delta-network is
designed to be 150 Ohm. These values are used to calculate the
limits of the UM disturbance voltage at the DC ports for any
types of GCPC. The derived limits for the UM disturbance
voltage at the DC port for class A and class B GCPCs are
shown in Table III and Table IV. The limits of the disturbance
voltage shown in Table IV were adjusted according to IEC
61000-6-3 Ed.1, and finally Table V was proposed as the limits
for the UM disturbance voltage at the DC port for class B
GCPCs.
AC
Power
Supply
ZCM-AMN
Fig. 4. A circuit diagram for the measurement of one DC port of GCPC
DC
Power
Supply
DC-ports1
AC-ports
GCPC
DC-AN
AMN
Decoupling
Network
ZCM-DCAN
DC
Power
Supply
TABLE III.
AC
Power
Supply
Frequency
Rang
MHz
0.15 – 0.5
0.5 – 5
5 – 30
Decoupling
Network
Iac
Idc1
THE LIMITS OF THE UM DISTURBANCE VOLTAGE AT THE DC
PORTS FOR CLASS A GCPCS
ZCM-AMN
Black Box
Rated power up to
20kVA
Rated power over
20kVA
Quasi-peak dB(μV)
Quasi-peak dB(μV)
95
89
89
116
102
a
106 to 89
DC-ports2
a.
TABLE IV.
Decoupling
Network
ZCM-DCAN
Idc2
THE LIMITS OF THE UM DISTURBANCE VOLTAGE AT THE DC
PORTS FOR CLASS B GCPCS
Frequency Rang MHz
0.15 – 0.5
0.5 – 5
5 – 30
TABLE V.
DERIVATION OF THE LIMITS BASD ON EACH APPROACH
A. Proportional relation approach
The existing limits of the disturbance voltage at the AC
ports for class A or class B equipment are found in Table 2 and
3 of CISPR 11 Ed.5.1 as shown below. Class B means
residential use, and class A means other than that.
TABLE I.
THE LIMITS OF THE DISTURBANCE VOLTAGE AT THE AC
PORTS FOR CLASS A IN TALBE 2 OF CISPR11 ED.5.1
Frequency
Rang
MHz
0.15 – 0.5
0.5 – 5
5 – 30
Rated power up to
20kVA
Rated power over
20kVA
Quasi-peak dB(μV)
Quasi-peak dB(μV)
79
73
73
100
86
a
90 to 73
a.
(decreasing linearly with logarithm of frequency)
TABLE II.
THE LIMITS OF THE DISTURBANCE VOLTAGE AT THE AC
PORTS FOR CLASS B IN TALBE 3 OF CISPR11 ED.5.1
Frequency Rang MHz
0.15 – 0.5
0.5 – 5
5 – 30
82 toa 72
72
76
(decreasing linearly with logarithm of frequency)
THE MODIFIED LIMITS OF THE UM DISTURBANCE VOLTAGE
AT THE DC PORTS FOR CLASS B GCPCS
Frequency Rang MHz
0.15 – 0.5
0.5 – 5
5 – 30
Quasi-peak dB(μV)
84 toa 74
74
74
a.
(decreasing linearly with logarithm of frequency)
B. Current-to-voltage conversion approach
The proposed limits based on the current-to-voltage
conversion approach are described. Because the limits of CM
disturbance current are required to derive the disturbance
voltage limits, the limits of CM disturbance current found in
CISPR 22 Table 3 and Table 4 are referred. The CM
impedance of the existing artificial delta-network is 150 Ohm.
According to the limits of the CM current and the CM
impedance, the limits of conducted CM disturbance voltage at
the DC ports can be derived as shown in Table VI and Table
VII. These derived limits are identical with the limits of CM
disturbance voltage found in CISPR 22 because the CM
termination impedance of the usual AAN used for termination
of telecommunication ports is 150 Ohm.
Quasi-peak dB(μV)
66 toa 56
56
60
a.
TABLE VI.
(decreasing linearly with logarithm of frequency)
In order to derive the limits of disturbance voltage at the
DC ports by using (2), the CM termination impedances of the
AMN and the DC-AN need to be selected. The CM impedance
of the single-phase / two-wire AMN is selected, and the CM
Copyright 2014 IEICE
Quasi-peak dB(μV)
a.
Fig. 5. A circuit diagram for the measurement of multiple DC ports of GCPC
IV.
(decreasing linearly with logarithm of frequency)
DC-AN
587
THE LIMITS OF THE CM DISTURBANCE VOLTAGE AT THE DC
PORTS FOR CLASS A GCPCS
Frequency Rang MHz
0.15 – 0.5
0.5 – 30
Quasi-peak dB(μV)
97 toa 87
87
a.
(decreasing linearly with logarithm of frequency)
EMC’14/Tokyo
TABLE VII.
15P-B3
THE LIMITS OF THE CM DISTURBANCE VOLTAGE AT THE DC
PORTS FOR CLASS B GCPCS
Frequency Rang MHz
0.15 – 0.5
0.5 – 30
Quasi-peak dB(μV)
84 toa 74
74
a.
V.
(decreasing linearly with logarithm of frequency)
CONSENSUS ON THE DERIVATION OF THE LIMITS
At a meeting in February 2011, agreement was settled in
respect of the limits of the disturbance voltage at the DC ports
for class B GCPCs, and for class A GCPCs with a rated
throughput power up to 20 kVA. Consideration was given to
the limits for class A GCPCs with over 20 kVA.
class A GCPCs with a rated throughput power up to 20 kVA.
In 2011, the German and Japanese experts could not reach a
settlement for the limits in the range 5 MHz to 30 MHz for
class A GCPCs with a rated throughput power over 20 kVA.
At a meeting in January 2013, the addition of alternative
measurement method shown in Fig. 6 was agreed, and all
experts agreed on the limits of disturbance voltage and current
for Class A GCPCs over 20kVA as well as over 75kVA shown
in Table X. The modified draft proposing the limits of
measurement method for class B and class A up to 20kVA
GCPCs was issued in February 2013, and another new draft
proposing those for class A GCPCs over 20kVA and over
75kVA also was issued in parallel.
A. Class B
For class B, the experts agreed on the limits in Table VIII,
which are identical with the limits in Table V (proposed by
German experts) and Table VII (proposed by Japanese
experts).
TABLE VIII.
THE LIMITS OF THE DISTURBANCE VOLTAGE AT THE DC
PORTS FOR CLASS B GCPCS
Frequency Rang MHz
0.15 – 0.5
0.5 – 30
Quasi-peak dB(μV)
84 toa 74
74
a.
(decreasing linearly with logarithm of frequency)
B. Class A with a rated throughput power up to 20 kVA
For class A with a rated throughput power up to20 kVA,
the experts looked for a compromise and the limits in Table IV
and Table VI were finally adjusted to meet the expectations of
all involved parties for an agreeable set of limits.
Consequently, the limits for class A GCPCs were settled as
shown in Table IX.
TABLE IX.
Fig. 6. Simple circuit diagram of the alternative measurement method
TABLE X.
Frequency
Rang
MHz
THE LIMITS OF THE DISTURBANCE VOLTAGE AT THE DC
PORTS FOR CLASS A GCPCS
Frequency Rang MHz
0.15 – 0.5
0.5 – 30
0.15 – 5
5– 30
Quasi-peak dB(μV)
(decreasing linearly with logarithm of frequency)
After a meeting in February 2012, the limits of Table VIII
and Table IV were incorporated in the first draft of a part of the
next edition of CISPR11.
C. Class A with a rated throughput power over 20 kVA
For class A GCPCs with a rated throughput power over 20
kVA, the German experts initially proposed the limits. These
limits had been derived using the proportional relation
approach only and referencing the limits for the disturbance
voltage at the AC port as specified in CISPR 11 Table 2 for
class A equipment with a rated input power over 20 kVA.
Because the Japanese experts did not have their own proposals
for the limits of this category of GCPCs, they agreed on the
proposal of the German experts made during the meeting in
2011 that the limits for GCPCs with a larger rated throughput
power might be relaxed further, for reasons of cost-efficient
construction of series-produced GCPCs. However, they also
suggested looking for a compromise based on the limits for
Copyright 2014 IEICE
Rated power
over 20kVA
up to 75kVA
Rated power
over 75kVA
Quasi-peak dB(μV)
Quasi-peak dB(μV)
Voltage
Current
Voltage
Current
116 toa 106
106 toa 89
72 toa 62
62 toa 45
132 toa 122
122 toa 105
88 toa 78
78 toa 61
a.
97 toa 89
89
a.
THE LIMITS OF THE DISTURBANCE VOLTAGE AT THE DC
PORTS FOR CLASS A GCPCS
VI.
(decreasing linearly with logarithm of frequency)
CONCLUSION
At the CISPR/B meeting in October 2013, it was agreed
that committee drafts would proceed to the next stage for
voting by national committees. It was also decided to continue
the maintenance team to extend the scope of the proposed
limits and measurement method to other types of GCPCs.
ACKNOWLEDGMENT
The development of the limits and measurement method
has been working in the CISPR/B/WG1/MT-GCPC. Author
would like to thank a convener of MT-GCPC, Mr. Inoue and
its members, i.e. Mr. Kodama, Mr. Hayashi, Mr. Hayes, and Dr.
Sisolefsky.
REFERENCES
[1]
588
H. Haeberlin, “New DC-LISN for EMC-Measurements on the DC side
of PV systems: Realisation and first Measurements at Inverters,” 17th
Eurpoe Photovoltaic Solar Energy Conference, Munich, Germany, Oct.
22 – Oct. 26, 2001