CA2269346A1 - Dc energy flow direction control using reverse blocking devices in dc-ac inverters - Google Patents
Dc energy flow direction control using reverse blocking devices in dc-ac inverters Download PDFInfo
- Publication number
- CA2269346A1 CA2269346A1 CA002269346A CA2269346A CA2269346A1 CA 2269346 A1 CA2269346 A1 CA 2269346A1 CA 002269346 A CA002269346 A CA 002269346A CA 2269346 A CA2269346 A CA 2269346A CA 2269346 A1 CA2269346 A1 CA 2269346A1
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- CA
- Canada
- Prior art keywords
- inverter
- output
- source
- energy
- reverse blocking
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0048—Circuits or arrangements for reducing losses
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Inverter Devices (AREA)
Abstract
A DC-AC inverter is defined as an electrical instrument to convert a DC
(direct current) source to an AC (alternating current) output. In such an instrument, the electric energy can flow from the DC source to the AC output, or from the AC output to the DC source. But the latter energy-flow direction is not the intentional design direction for the inverter. This phenomenon exists when the voltage level at the DC source is lower than the voltage level at the AC
output, for example, when the inverter is used in the wind energy conversion systems at low wind conditions, or when the inverter is used in the photovoltaic solar energy conversion systems at cloudy time. In such systems, the AC output is connected to the electric power lines, or the electric grid as the technical term used by electric utilities. The energy-flow from the AC to the DC can cause substantial reactive power, usually in lagging form, interference with the electric power delivery, increasing energy losses and reducing the energy conversion efficiency of the wind energy conversion systems or photovoltaic solar energy conversion systems.
In this invention, the electric energy-flow unique direction from the DC to the AC is secured by adding a reverse blocking device, for example, a diode in series connection in between the DC
source and the inverter. By adding such a reverse blocking device, for example a diode, defined as the blocking diode, the electric energy-flow is confined only from the DC
source to the AC output no matter what the DC voltage level is. As a result, the reactive power output of the inverter and energy losses are reduced, and the system energy conversion efficiency is increased. A small fraction of the previous DC capacitance will be moved to the position after the reverse blocking device, or an additional capacitor will be added at the position after the reverse blocking device to smooth the inverter current commutation and reduce the voltage tension on the inverter switching devices. Other options to reduce the voltage tension may also include a parallel connected switch with the reverse blocking device and a voltage varistor.
(direct current) source to an AC (alternating current) output. In such an instrument, the electric energy can flow from the DC source to the AC output, or from the AC output to the DC source. But the latter energy-flow direction is not the intentional design direction for the inverter. This phenomenon exists when the voltage level at the DC source is lower than the voltage level at the AC
output, for example, when the inverter is used in the wind energy conversion systems at low wind conditions, or when the inverter is used in the photovoltaic solar energy conversion systems at cloudy time. In such systems, the AC output is connected to the electric power lines, or the electric grid as the technical term used by electric utilities. The energy-flow from the AC to the DC can cause substantial reactive power, usually in lagging form, interference with the electric power delivery, increasing energy losses and reducing the energy conversion efficiency of the wind energy conversion systems or photovoltaic solar energy conversion systems.
In this invention, the electric energy-flow unique direction from the DC to the AC is secured by adding a reverse blocking device, for example, a diode in series connection in between the DC
source and the inverter. By adding such a reverse blocking device, for example a diode, defined as the blocking diode, the electric energy-flow is confined only from the DC
source to the AC output no matter what the DC voltage level is. As a result, the reactive power output of the inverter and energy losses are reduced, and the system energy conversion efficiency is increased. A small fraction of the previous DC capacitance will be moved to the position after the reverse blocking device, or an additional capacitor will be added at the position after the reverse blocking device to smooth the inverter current commutation and reduce the voltage tension on the inverter switching devices. Other options to reduce the voltage tension may also include a parallel connected switch with the reverse blocking device and a voltage varistor.
Description
Specif canon This invention relates to the energy conversion efficiency improvement and the reduction of reactive power output and energy losses of DC-AC inverters. This invention is especially intended to the wind energy electric conversion systems and the photovoltaic solar energy electric conversion systems.
A typical single-phase DC-AC inverter diagram is shown in Figure I (see page 6/8). The switching devices shown, T1, T2, T3, and T4, are, but not necessary, transistors as shown here just for describing convenience. The switching devices can be any type, for example, thyristors, GTOs (gate turned-off thyristors), and IGBTs (insulated gate bipolar transistors), etc. On the
A typical single-phase DC-AC inverter diagram is shown in Figure I (see page 6/8). The switching devices shown, T1, T2, T3, and T4, are, but not necessary, transistors as shown here just for describing convenience. The switching devices can be any type, for example, thyristors, GTOs (gate turned-off thyristors), and IGBTs (insulated gate bipolar transistors), etc. On the
2/8 other hand, this invention is intended not only on single-phase inverters, as shown in Figure 1, but also intended on the multi-phase inverters such as 3-phase inverters as shown in Figure 3 (see page 7/8). In Figure 1, the DC source represents any sources which can be used to generate the DC output, for example, a DC battery or any rectifiers' output, controlled or uncontrolled, controllable or uncontrollable, etc. Capacitor Cd is normally used in the DC-AC inverters, and functioned as: (1) a filter to smooth the DC source; (2) a part of inverter current commutation circuit. Diodes D1, D2, D3, and D4 are the other part of inverter current commutation circuit.
If the DC voltage Vdc is higher than the AC voltage vo at any time, the DC
energy can be directed from the DC source to the AC output by controlling the switching devices T1, T2, T3, and T4. But if Vdc is lower than vo at some time during the cycle and the AC
output is connected to the electric power lines, such as in the case of wind energy electric conversion systems, the AC
electric power will flow back to the DC source through D1, D2, D3, and D4.
This energy-flow-back introduces substantial reactive power to the power lines from the inverter, making significant energy losses, reducing energy conversion efficiency, and resulting in less DC
source energy converted and directed to the electric power lines.
I have found that these disadvantages may be overcome by adding a reverse blocking device DO
such as a diode in series connection in between the DC source and the inverter as shown in Figure 2 (see page 6/8) or in Figure 4 (see page 7/8). The diode, defined as the blocking diode, confines the electric energy-flow uniquely from the DC source to the AC output, and there is no way to allow the AC energy to flow back to the DC. The above disadvantages can therefore be overcome.
This blocking diode may cause the inverter current commutation dill'lculty.
This di~culty depends on the switching algorithms - normally defined as the pulse width modulation (P~
techniques. However, no matter what switching algorithms are employed, the diil'lculty introduced by the blocking diode may be overcome by splitting the previous DC
capacitor Cd into two parts, Cdl= (1-m/n)Cd and Cd2=(m/n)Cd and connecting two parts ofthe capacitor at the positions before and after the blocking diode as shown in Figure 2 or Figure 4. Where n and m are positive numbers (n>0, m>0), n is larger than m (n>m). The numbers n and m can be properly selected by computer simulation. For example, n=1-20/1000, m=20/1000. The second method to overcome the current commutation difficulty due to the blocking diode is that the previous capacitor Cd is kept at the position before the blocking diode as Cdl, and adding the other capacitor Cd2 after the blocking diode. The capacitance of Cd2 can be selected by computer simulation. Cd2 may not be necessary if certain type of PWM techniques are employed. I have found that a snubber capacitor (high frequency, high Q, low loss, non-inductance or low inductance) type may be selected for Cd2. To select a proper Cd2, I have found the following principle. A small value of Cd2 will help to overcome the disadvantages caused by the low DC
voltage -- the smaller the Cd2 value, the better, but will introduce a higher voltage tension on the switching devices T 1 through T4. A larger Cd2 will help to reduce the voltage tension but is not good to overcome the disadvantages. Therefore, a compromise may be required to decide the value of Cd2.
If the DC voltage Vdc is higher than the AC voltage vo at any time, the DC
energy can be directed from the DC source to the AC output by controlling the switching devices T1, T2, T3, and T4. But if Vdc is lower than vo at some time during the cycle and the AC
output is connected to the electric power lines, such as in the case of wind energy electric conversion systems, the AC
electric power will flow back to the DC source through D1, D2, D3, and D4.
This energy-flow-back introduces substantial reactive power to the power lines from the inverter, making significant energy losses, reducing energy conversion efficiency, and resulting in less DC
source energy converted and directed to the electric power lines.
I have found that these disadvantages may be overcome by adding a reverse blocking device DO
such as a diode in series connection in between the DC source and the inverter as shown in Figure 2 (see page 6/8) or in Figure 4 (see page 7/8). The diode, defined as the blocking diode, confines the electric energy-flow uniquely from the DC source to the AC output, and there is no way to allow the AC energy to flow back to the DC. The above disadvantages can therefore be overcome.
This blocking diode may cause the inverter current commutation dill'lculty.
This di~culty depends on the switching algorithms - normally defined as the pulse width modulation (P~
techniques. However, no matter what switching algorithms are employed, the diil'lculty introduced by the blocking diode may be overcome by splitting the previous DC
capacitor Cd into two parts, Cdl= (1-m/n)Cd and Cd2=(m/n)Cd and connecting two parts ofthe capacitor at the positions before and after the blocking diode as shown in Figure 2 or Figure 4. Where n and m are positive numbers (n>0, m>0), n is larger than m (n>m). The numbers n and m can be properly selected by computer simulation. For example, n=1-20/1000, m=20/1000. The second method to overcome the current commutation difficulty due to the blocking diode is that the previous capacitor Cd is kept at the position before the blocking diode as Cdl, and adding the other capacitor Cd2 after the blocking diode. The capacitance of Cd2 can be selected by computer simulation. Cd2 may not be necessary if certain type of PWM techniques are employed. I have found that a snubber capacitor (high frequency, high Q, low loss, non-inductance or low inductance) type may be selected for Cd2. To select a proper Cd2, I have found the following principle. A small value of Cd2 will help to overcome the disadvantages caused by the low DC
voltage -- the smaller the Cd2 value, the better, but will introduce a higher voltage tension on the switching devices T 1 through T4. A larger Cd2 will help to reduce the voltage tension but is not good to overcome the disadvantages. Therefore, a compromise may be required to decide the value of Cd2.
3/8 Another option to overcome the voltage tension difficulty is to use a bypass switch, S 1, connected in parallel with the reverse blocking device DO as shown in Figure 5 and Figure 6 (see page 8/8).
The switch S 1 can be any type, for example, the mechanical type, the electro-magnetic type, the solid type, and the semiconductor's type, etc. At low DC voltage conditions when the voltage tension on the switching devices is low, the bypass switch S 1 will be open to secure the DC
energy-flow direction from the DC source to the AC output. At high DC voltage conditions when the voltage tension is high, S 1 can be closed to reduce the voltage tension.
A high DC voltage will actually produce the correct energy-flow direction from the DC source to the AC output.
A voltage varistor, VR, as shown in Figure S and Figure 6, connected in parallel with the Cd2 can provide another option to reduce the voltage tension on the switching devices due to the introduction of the reverse blocking device.
The switch S 1 can be any type, for example, the mechanical type, the electro-magnetic type, the solid type, and the semiconductor's type, etc. At low DC voltage conditions when the voltage tension on the switching devices is low, the bypass switch S 1 will be open to secure the DC
energy-flow direction from the DC source to the AC output. At high DC voltage conditions when the voltage tension is high, S 1 can be closed to reduce the voltage tension.
A high DC voltage will actually produce the correct energy-flow direction from the DC source to the AC output.
A voltage varistor, VR, as shown in Figure S and Figure 6, connected in parallel with the Cd2 can provide another option to reduce the voltage tension on the switching devices due to the introduction of the reverse blocking device.
4/8
Claims (6)
1. A reverse blocking device D0, such as a diode, added at the position in series connection in between the DC source and the inverter, to make a unique energy-flow direction only from the DC source to the AC output through the inverter.
2. The capacitor Cd is split into two parts either as Cd1=(1-n/m)Cd and Cd2=(n/m)Cd, n>m>0, and these two parts are positioned and connected at before and after the reverse blocking device as described in claim 1.
3. The capacitor Cd is kept at the position before the blocking diode as described in claim 1, and adding the second capacitor Cd2 at the position after the blocking diode as described in claim 1.
4. A bypass switch connected in parallel with the reverse blocking device as described in claim 1.
5. A voltage varistor connected in parallel with the Cd2 as described in claim 2 and claim 3.
6. A DC-AC inverter including the configurations as described in claim 1, claim 2, claim 3, claim 4, and claim 5.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002269346A CA2269346A1 (en) | 1999-04-14 | 1999-04-14 | Dc energy flow direction control using reverse blocking devices in dc-ac inverters |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002269346A CA2269346A1 (en) | 1999-04-14 | 1999-04-14 | Dc energy flow direction control using reverse blocking devices in dc-ac inverters |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2269346A1 true CA2269346A1 (en) | 2000-10-14 |
Family
ID=29588804
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002269346A Abandoned CA2269346A1 (en) | 1999-04-14 | 1999-04-14 | Dc energy flow direction control using reverse blocking devices in dc-ac inverters |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2269346A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2254231A1 (en) * | 2009-05-06 | 2010-11-24 | Robert Bosch GmbH | Inverter assembly |
| CN111384726A (en) * | 2020-01-21 | 2020-07-07 | 国网安徽省电力有限公司六安供电公司 | High-permeability photovoltaic power distribution network partition voltage regulation method |
-
1999
- 1999-04-14 CA CA002269346A patent/CA2269346A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2254231A1 (en) * | 2009-05-06 | 2010-11-24 | Robert Bosch GmbH | Inverter assembly |
| CN111384726A (en) * | 2020-01-21 | 2020-07-07 | 国网安徽省电力有限公司六安供电公司 | High-permeability photovoltaic power distribution network partition voltage regulation method |
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| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |