FI20195018A1 - A converter device and a method for controlling a converter device - Google Patents

A converter device and a method for controlling a converter device Download PDF

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Publication number
FI20195018A1
FI20195018A1 FI20195018A FI20195018A FI20195018A1 FI 20195018 A1 FI20195018 A1 FI 20195018A1 FI 20195018 A FI20195018 A FI 20195018A FI 20195018 A FI20195018 A FI 20195018A FI 20195018 A1 FI20195018 A1 FI 20195018A1
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FI
Finland
Prior art keywords
converter
switch
converter device
operational mode
control signals
Prior art date
Application number
FI20195018A
Other languages
Finnish (fi)
Swedish (sv)
Other versions
FI128738B (en
Inventor
Aleksi Mattsson
Pasi Nuutinen
Pasi Peltoniemi
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Zero Hertz Systems Oy
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Priority to FI20195018A priority Critical patent/FI128738B/en
Publication of FI20195018A1 publication Critical patent/FI20195018A1/en
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Publication of FI128738B publication Critical patent/FI128738B/en

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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
    • H02M7/493—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 the static converters being arranged for operation in parallel
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J5/00—Circuit arrangements for transfer of electric power between ac networks and dc networks
    • 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
    • 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

Abstract

A converter device comprises converter terminals (L1, L2, L3) for connecting to an external electric system, a first converter element (101) connected to the converter terminals, and a second converter element (102) connected to the converter terminals. The converter device comprises a switch controller (118), such as a PWM modulator, for producing switch-control signals suitable for running the first converter element as well as the second converter element. The converter device comprises a signal router (119) for controlling which of the converter elements receives the switch-control signals produced by the switch controller. Thus, the same switch controller can be used for both the converter elements.

Description

A converter device and a method for controlling a converter device Field of the disclosure The disclosure relates to a converter device for transferring electric energy between systems having different voltages.
The converter device can be, for example but not necessarily, an inverter for transferring electric energy between a direct voltage system and an alternating voltage system.
Furthermore, the disclosure relates to a direct voltage distribution system.
Furthermore, the disclosure relates to a method for controlling a converter device.
Background In many cases, there is a need to transfer electric energy between systems having different voltages.
A typical example is a case where one or more parts of an electricity distribution system based on three-phase alternating voltage, such as e.g. 230/400 V, 50 Hz alternating voltage, is/are replaced with direct voltage distribution. — In this exemplifying case, the utilization of the direct voltage distribution opens new possibilities for network development.
For example, with a same voltage drop and a same three-phase cable a 1.5 kV direct voltage system can transfer significantly more power than a 0.4 kV alternating voltage system.
A direct voltage distribution system comprises typically one or more transformers and one or more power electronic converters for transferring electric power between an alternating voltage > supply network and a direct voltage distribution network.
The alternating voltage N supply network can be for example but not necessarily a 20 kV, 50 Hz three-phase > network, and the direct voltage distribution network can be for example but not - necessarily a +750 V bipolar direct voltage network or a 1500 V unipolar direct E 25 voltage network.
The above-mentioned power electronic converters are = advantageously capable of bi-directional power transfer between the alternating 3 voltage supply network and the direct voltage distribution network.
Furthermore, the S direct voltage distribution system comprises one or more inverters for transferring electric power between the direct voltage distribution network and an alternating voltage network of each customer.
The above-mentioned inverters areadvantageously capable of bi-directional power transfer between the direct voltage distribution network and the alternating voltage networks of the customers.
Component prices of power electronics have constantly been decreasing in the last decades allowing power electronic devices to be used in greater number of applications.
This development has improved the cost efficiency of direct voltage distribution systems of the kind described above.
Furthermore, the direct voltage power distribution enables improvement of customer’s electricity quality with lower costs compared to alternating voltage distribution systems.
Direct voltage distribution systems of the kind described above are however not free from challenges.
One of the challenges is related to a requirement that an inverter of a direct voltage distribution system must be able to supply sufficiently high current to an alternating voltage network of a customer in peak-load and fault situations.
Typically, an inverter that can momentarily supply current substantially higher than nominal current has low efficiency at partial loads, and/or the price the inverter is high in terms of price per nominal power.
Therefore, there is a need for new inverter designs to further improve the cost efficiency of direct voltage distribution systems of the kind described above.
Summary The following presents a simplified summary in order to provide a basic understanding of some aspects of various embodiments.
The summary is not an o extensive overview of the invention.
It is neither intended to identify key or critical > elements of the invention nor to delineate the scope of the invention.
The following 5 summary merely presents some concepts in a simplified form as a prelude to a more = detailed description of exemplifying embodiments.
E 25 In accordance with the invention, there is provided a new converter device for = transferring electric energy between systems having different voltages.
The 3 converter device can be, for example but not necessarily, an inverter for transferring S electric energy between a direct voltage system and an alternating voltage system.
The direct voltage system can be for example a direct voltage distribution network and the alternating voltage system can be for example an alternating voltagenetwork of a customer i.e. an end-user of electricity. A converter device according to the invention comprises: - converter terminals for connecting to an electric system external to the converter device, e.g. an alternating voltage network of a customer, - at least one first converter element for converting one or more first voltages, e.g. a direct voltage, into one or more second voltages, e.g. three-phase alternating voltages, being at terminals of the first converter element connected to the converter terminals, - at least one second converter element for converting the one or more first voltages into one or more third voltages being at terminals of the second converter element connected to the converter terminals, - a switch controller, e.g. a pulse width modulator “PWM-modulator’, for producing one or more switch-control signals suitable for controlling first controllable power electronic switch or switches of the first converter element and suitable for controlling second controllable power electronic switch or switches of the second converter element, and - a signal router controllable to operate in a first operational mode where the signal router is configured to deliver the one or more switch-control signals to the first converter element without delivering the one or more switch- control signals to the second converter element, and in a second operational > mode where the signal router is configured to deliver the one or more switch-
O N control signals to the second converter element without delivering the one or <Q more switch-control signals to the first converter element.
z As the converter device comprises the above-mentioned signal router, the same a © 25 switch controller can be used for both the first and second converter elements. This 3 makes it possible to use a simpler and more cost-effective processing system for o D implementing the control of the controllable power electronic switches of the first
N and second converter elements.
The above-mentioned first converter element can be for example an inverter bridge that is optimized to transfer power with a good efficiency from e.g. a direct voltage distribution network to e.g. an alternating voltage network of a customer when the power is small or at least below a predetermined limit, whereas the second converter element can be another inverter bridge that is optimized to transfer power from the direct voltage distribution network to the above-mentioned alternating voltage network during situations where high current is needed, e.g. peak-load situations and/or fault situations.
In accordance with the invention, there is provided also a new direct voltage distribution system that comprises: - a direct voltage distribution network, - at least one network converter for transferring electric power between an alternating voltage supply network and the direct voltage distribution network, and - at least one converter device according to the invention, wherein the converter device is an inverter for transferring electric power between the direct voltage distribution network and at least one alternating voltage network of a customer.
In accordance with the invention, there is provided also a new method for controlling a converter device that comprises at least one first converter element for supplying > electric power to an electric system external to the converter device, at least one N second converter element for supplying electric power to the electric system, and a > switch controller producing one or more switch-control signals suitable for controlling - controllable power electronic switch or switches of the first converter element and E 25 suitable for controlling controllable power electronic switch or switches of the second = converter element. A method according to the invention comprises: 3 D - connecting the one or more switch-control signals to the second converter N element and disconnecting the one or more switch-control signals from the first converter element in response to a transition from a first operationalmode of the converter device to a second operational mode of the converter device, and - connecting the one or more switch-control signals to the first converter element and disconnecting the one or more switch-control signals from the 5 second converter element in response to a transition from the second operational mode of the converter device to the first operational mode of the converter device.
Various exemplifying and non-limiting embodiments are described in accompanied dependent claims.
Exemplifying and non-limiting embodiments both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying and non-limiting embodiments when read in conjunction with the accompanying drawings.
The verbs “to comprise” and “to include” are used in this document as open — limitations that neither exclude nor reguire the existence of unrecited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality. Brief description of figures o 20 Exemplifying and non-limiting embodiments and their advantages are explained in S greater detail below in the sense of examples and with reference to the 5 accompanying drawings, in which: > figures 1a, 1b, and 1c illustrate a converter device according to an exemplifying and E non-limiting embodiment, 0 3 25 figures 2a, 2b, and 2c illustrate a converter device according to another exemplifying > and non-limiting embodiment, figure 3 illustrates a direct voltage distribution system according to an exemplifying and non-limiting embodiment, andfigure 4 shows a flowchart of a method according to an exemplifying and non-limiting embodiment for controlling a converter device.
Description of exemplifying embodiments The specific examples provided in the description given below should not be construed as limiting the scope and/or the applicability of the appended claims.
Lists and groups of examples provided in the description given below are not exhaustive unless otherwise explicitly stated.
Figure 1a illustrates schematically a converter device 100 according to an exemplifying and non-limiting embodiment.
In this exemplifying case, the converter device 100 is an inverter suitable for transferring electric energy between a direct voltage system and an alternating voltage system.
The converter device 100 comprises a first converter element 101 for converting first voltage Upc into second voltages being at terminals a1, b1, and c1 of the first converter element 101. The converter device 100 comprises a second converter element 102 for converting the first voltage Upc into third voltages being at terminals a2, b2, and c2 of the second converter element 102. In this exemplifying case, the first voltage Upc is direct voltage and the converter elements 101 and 102 are inverter bridges configured to convert the direct voltage into three-phase alternating voltages.
It is also possible that a converter device according to an exemplifying and non-limiting embodiment is configured to convert direct voltage into single-phase alternating voltage.
Furthermore, it is also possible that a converter device according to an exemplifying © and non-limiting embodiment is configured to convert direct voltage into other direct N voltage, i.e. the converter device is a direct voltage-to-direct voltage “DC-DC” O converter.
Yet furthermore, it is also possible that a converter device according to - 25 an exemplifying and non-limiting embodiment is configured to convert one or more = alternating voltages into one or more other alternating voltages, i.e. the converter © device can be a frequency converter.
In this exemplifying case, the converter device 3 may comprise a converter element such as a rectifier for transferring electric energy > from an alternating voltage network to direct voltage capacitors.
The converter device 100 comprises converter terminals L1, L2, and L3 for connecting to an alternating voltage system external to the converter device.
In thisexemplifying case, the converter device 100 comprises a first filter 103 between the terminals a1, b1, and c1 of the first converter element 101 and the converter terminals L1-L3, and a second filter 104 between the terminals a2, b2, and c2 of the second converter element 102 and the converter terminals L1-L3. In exemplifying cases where the first and second converter elements 101 and 102 are operated in a temporally non-overlapping way, i.e. the first and second converter elements 101 and 102 are not run in parallel, and/or the first and second converter elements 101 and 102 are like each other, it is also possible that the terminals a1, b1, and c1 of the first converter element 101 are directly connected to the converter terminals L 1- 13, and correspondingly the terminals a2, b2, and c2 of the second converter element 102 are directly connected to the converter terminals L1-L3. Figure 1b shows the main circuit of the first converter element 101, and figure 1c shows the main circuit of the second converter element 102. As shown in figure 1b, the first converter element 101 is a three-level inverter bridge that comprises three inverter legs connected to the terminals a1, b1, and c1, and a fourth inverter leg 109 connected to a first middle-point voltage terminal n1. Correspondingly, as shown in figure 1c, the second converter element 102 is a three-level inverter bridge that comprises three inverter legs connected to the terminals a2, b2, and c2, and afourth inverter leg 110 connected to a second middle-point voltage terminal n2. As shown in figures 1b and 1c, the main circuit of the first converter element 101 comprises first controllable power electronic switches and diodes, and the main circuit of the second converter element 102 comprises second controllable power electronic o switches and diodes. In figure 1b, two of the controllable power electronic switches S of the first converter element 101 are denoted with references 105 and 106. In figure 5 25 1c, two of the controllable power electronic switches of the second converter - element 102 are denoted with references 107 and 108.
T E In a converter device according to an exemplifying and non-limiting embodiment, = the controllable power electronic switches of the first and second converter elements 3 101 and 102 have been selected so that the controllable power electronic switches N 30 of the first converter element 101 have smaller switching losses than controllable power electronic switches of the second converter element 102, and the controllable power electronic switches of the second converter element 102 have a greatermaximum allowable current than the controllable power electronic switches of the first converter element 101. Therefore, in this exemplifying case, the first converter element 101 can be used for transferring power with good efficiency when the power is small or at least below a predetermined limit, whereas the second converter element 102 can be used for transferring power during e.g. temporary peak-load situations and during fault situations where high current is needed.
The converter device 100 comprises a switch controller 118, e.g. a pulse width modulator “PWM-modulator’, for producing switch-control signals SwC that are suitable for controlling the controllable power electronic switches of the first converter element 101 and suitable for controlling the controllable power electronic switches of the second converter element 102. The converter device 100 comprises a signal router 119 controllable to operate in a first operational mode where the signal router is configured to deliver the switch-control signals SwC to the first converter element 101 without delivering the switch-control signals SwC to the second converter element 102, and in a second operational mode where the signal router 119 is configured to deliver the switch-control signals SwC to the second converter element 102 without delivering the switch-control signals SwC to the first converter element 101. Therefore, the same switch controller 118 can be used for both the first and second converter elements 101 and 102.
In a converter device according to an exemplifying and non-limiting embodiment, the signal router 119 is controllable to operate in a third operational mode where the signal router 119 is configured to deliver the switch-control signals SwC to both the = first and second converter elements 101 and 102. In a converter device according = to an exemplifying and non-limiting embodiment, a control system 114 is configured ? 25 to control the signal router 119 from the first operational mode to the second > operational mode via the third operational mode. In a converter device according to E another exemplifying and non-limiting embodiment, the control system 114 is = configured to control the signal router 119 from the second operational mode to the 3 first operational mode via the third operational mode. The operation time in the third N 30 operational mode is advantageously adjustable.
A converter device according to an exemplifying and non-limiting embodiment comprises a measurement system 115 for producing measurement data dependent on loading of the converter device 100. The measurement system 115 may comprise for example current and/or voltage transformers and/or e.g. Hall-sensor based transducers for measuring electrical quantities on the converter terminals L1- L3. The control system 114 can be configured to control the signal router 119 based on the measurement data for example so that the first converter element 101 is used for transferring power when the power is small or at least below a predetermined limit, whereas the second converter element 102 is used for transferring power during e.g. temporary peak-load situations and during fault situations where high current is needed.
A converter device according to an exemplifying and non-limiting embodiment comprises two or more first converter elements of the kind described above and/or two or more second converter elements of the kind described above. In a converter — device according to an exemplifying and non-limiting embodiment, the first converter elements can be run in parallel for transferring power when the power is small or at least below a predetermined limit, whereas the second converter elements can be run in parallel for transferring power during temporary peak-load situations and during fault situations where high current is needed.
A converter device according to an exemplifying and non-limiting embodiment comprises a direct voltage-to-direct voltage converter element, ie. a DC-DC converter element, for controlling the direct voltage supplied to the first and second = converter elements 101 and 102 shown in figure 1a. The DC-DC converter element = is not shown in figure 1a. In a converter device according to an exemplifying and ? 25 non-limiting embodiment, the above-mentioned DC-DC converter element is > configured to provide galvanic isolation. In this exemplifying case, a need for a E transformer between the converter device and an alternating voltage system can be = avoided in many applications where the converter device is arranged to transfer > electric energy between a direct voltage system and the alternating voltage system.
N Inthe exemplifying converter device 100 illustrated in figures 1a-1c, the controllable power electronic switches of the first converter element 101 are silicon carbide metaloxide field effect transistors “SiC MOSFET” and the controllable power electronic switches of the second converter element 102 are insulated gate bipolar transistors “IGBT”. For another example, the controllable power electronic switches of the first converter element 101 can be Gallium-Nitride “GaN” components and the controllable power electronic switches of the second converter element 102 can be IGBTs or SiC MOSFETs. In the above-mentioned exemplifying cases, the controllable power electronic switches of the first converter element 101 have a semiconductor structure different from a semiconductor structure of the controllable power electronic switches of the second converter element 102, i.e. the controllable power electronic switches of the first converter element 101 are of different type than the controllable power electronic switches of the second converter element
102. It is however also possible that the controllable power electronic switches of the first and second converter elements 101 and 102 are of a same type. For example, all the controllable power electronic switches can be IGBTs but the IGBTs of the first converter element 101 have been designed to have a smaller maximum current and thereby smaller switching losses than the IGBTs of the second converter element 102. In the exemplifying case illustrated in figures 1a-1c, each of the first and second converter elements 101 and 102 has many controllable power electronic switches. In an exemplifying case where a converter device according to an exemplifying and non-limiting embodiment is a DC-DC converter, each of the first and second converter elements can be, for example but not necessarily, a buck or boost converter having only one controllable power electronic switch. o In the exemplifying converter device 100 illustrated in figures 1a-1c, the first filter S 103 comprises first serial coils 111 connected between the first converter element 5 25 101 and the converter terminals L1-L3. Furthermore, in this exemplifying case, the —- first filter 103 further comprises capacitors 112 connected to the converter terminals E L1-L3. The second filter 104 comprises second serial coils 113 connected between co the second converter element 102 and the converter terminals L1-L3. In cases 2 where more damping is needed in addition to damping provided by losses of the > 30 serial coils 111 and 113, damping resistors can be added to be in series with the serial coils. The damping resistors are not shown in figure 1a. In many applications, inductances of the second serial coils 113 can be smaller than inductances of thefirst serial coils 111 because currents of the second serial coils 113 are greater than currents of the first serial coils 111. In cases where the coils have ferromagnetic cores, a linearizing airgap can be wider in the ferromagnetic cores of the second serial coils 113 than in the ferromagnetic cores of the first serial coils 111. Widening a linearizing airgap decreases the inductance but, on the other hand, increases a saturation limit i.e. the maximum current which does not saturate the ferromagnetic core.
Despite the greater currents of the second serial coils 113, the physical sizes of second serial coils 113 can be about the same as the physical sizes of first serial coils 111 because thermal loading of the second serial coils 113 is more bursty and occurs more rarely than that of the first serial coils 111. Thus, the heat capacity of materials can be utilized more in the thermal design of the second serial coils 113than in the thermal design of the first serial coils 111. In the exemplifying converter device 100 illustrated in figures 1a-1c, the above- mentioned capacitors 112 are star-connected.
The first middle-point voltage terminal n1 of the first converter element 101 is connected to a star-point of the star- connected capacitors via a coil 116, and the second middle-point voltage terminal n2 of the second converter element 102 is connected to the star-point via a coil 117. Furthermore, in the exemplifying converter device illustrated in figures 1a-1c, a middle point of a direct voltage capacitor system is connected to the star-point of the star-connected capacitors 112. In a case where the converter terminals L1-L3 are connected to star-connected transformer windings, a terminal N shown in figure 1a can be connected to a star-point of the transformer windings.
The first and/or o second middle-point voltage terminal n1 and/or n2 can be used for supplying current S when there is a non-symmetric load so that the sum of currents of the converter 5 25 terminals L1-L3 deviates from zero.
The coil 116 can be a part of a same mechanical —- device that implements the first serial coils 111. Correspondingly, the coil 117 can E be a part of a same mechanical device that implements the second serial coils 113. © It is also possible that the coil 116 is a separate device with respect to the coils 111 2 and/or the coil 117 is a separate device with respect to the coils 113. In exemplifying > 30 cases where the first and second converter elements 101 and 102 are operated in a temporally non-overlapping way and/or the first and second converter elements 101 and 102 are like each other, the coils 116 and 117 can be replaced with a singlecoil so that the first and second middle-point voltage terminals n1 and n2 are directly connected to each other and to a first terminal of the coil and a second terminal of the coil is connected to the terminal N and to the star-point of the star-connected capacitors 112.
Figure 2a illustrates schematically a converter device 200 according to an exemplifying and non-limiting embodiment. In this exemplifying case, the converter device 200 is an inverter for transferring electric energy between a direct voltage system and an alternating voltage system. The converter device 200 comprises a first converter element 201 for converting direct voltage Upc into three-phase alternating phase-voltages. The converter device 200 comprises a second converter element 202 for converting the direct voltage Upc into three-phase alternating voltages. The converter device 200 is otherwise like the converter device 100 but the first and second converter elements 201 and 202 are two-level inverter bridges whereas the converter elements 101 and 102 of the converter device 100 are three- level inverter bridges. Figure 2b shows the main circuit of the first converter element 201, and figure 2c shows the main circuit of the second converter element 202.
In addition to the elements illustrated in figures 1a-1c and 2a-2c, each of the converter devices 100 and 200 comprises, among others, driver circuits for driving the controllable power electronic switches in accordance with the switch control signals SwC received from the signal router 119. The driver circuits are not shown in figures 1a-1c and 2a-2c. The control system 114 can be implemented with one or more processor circuits each of which can be a programmable processor circuit, = e.g. a digital signal processor “DSP”, provided with appropriate software, a = dedicated hardware processor such as for example an application specific ? 25 integrated circuit “ASIC”, or a configurable hardware processor such as for example a field programmable gate array “FPGA”. Furthermore, the control system 114 may E comprise one or more memory circuits each of which can be for example a random- = access memory “RAM”. Correspondingly, the switch controller 118 can be 3 implemented with one or more processor circuits and with one or more memory N 30 circuits. The signal router 119 can be implemented with e.g. a controllable logic circuit.
Figure 3 illustrates a direct voltage distribution system according to an exemplifying and non-limiting embodiment.
The direct voltage distribution system comprises a direct voltage distribution network 350 and a network converter 351 for transferring electric power between an alternating voltage supply network 352 and the direct voltage distribution network 350. It is also possible that there are two or more network converters for transferring electric power between the alternating voltage supply network 352 and the direct voltage distribution network 350. The direct voltage distribution system comprises converter devices 300, 320, and 330 for transferring electric power between the direct voltage distribution network 350 and alternating voltage networks 354, 355, and 356 of customers.
In this exemplifying case, the converter device 300 is like the converter device 100 illustrated in figures 1a-1c.
The middle-point voltage terminals n1 and n2 of the converter device 300 are connected via coils 116 and 117 to a star-point of a transformer 353. The middle- point voltage terminals n1 and/or n2 can be used for supplying current when the alternating voltage network 354 loads the transformer 353 non-symmetrically so that the sum of phase currents deviates from zero.
The converter devices 320 and 330 can be for example like the converter device 100 illustrated in figures 1a-1c or the converter device 200 illustrated in figures 2a-2c.
In the exemplifying case illustrated in figure 3, the measurement system 115 of the converter device 300 is located atthe secondary side of the transformer 353. Figure 4 shows a flowchart of a method according to an exemplifying and non- limiting embodiment for controlling a converter device that comprises: at least one o first converter element for supplying electric power to an electric system external to S the converter device, at least one second converter element for supplying electric 5 25 power to the electric system, and a switch controller producing one or more switch- —- control signals suitable for controlling controllable power electronic switch or E switches of the first converter element and suitable for controlling controllable power co electronic switch or switches of the second converter element.
The method
2 comprises the following actions:
N 30 - action 401: connecting the one or more switch-control signals to the second converter element and disconnecting the one or more switch-control signals from the first converter element in response to a transition from a firstoperational mode of the converter device to a second operational mode of the converter device, and - action 402: connecting the one or more switch-control signals to the first converter element and disconnecting the one or more switch-control signals from the second converter element in response to a transition from the second operational mode of the converter device to the first operational mode of the converter device.
In a method according to an exemplifying and non-limiting embodiment, the transition from the first operational mode to the second operational mode is carried out via a third operational mode where the one or more switch-control signals are delivered to both the first and second converter elements.
In a method according to an exemplifying and non-limiting embodiment, the transition from the second operational mode to the first operational mode is carried out via the third operational mode.
A method according to an exemplifying and non-limiting embodiment comprises producing measurement data dependent on loading of the converter device and selecting between the first and second operational modes based on the measurement data.
The specific examples provided in the description given above should not be construed as limiting the applicability and/or the interpretation of the appended > claims. Lists and groups of examples provided in the description given above are a not exhaustive unless otherwise explicitly stated.
<Q j © a
N

Claims (10)

What is claimed is:
1. A converter device (100, 200, 300) comprising: - converter terminals (L1, L2, L3) for connecting to an electric system external to the converter device, - at least one first converter element (101, 201) for converting one or more first voltages into one or more second voltages being at terminals (a1, b1, c1) of the first converter element connected to the converter terminals, - at least one second converter element (102, 202) for converting the one or more first voltages into one or more third voltages being at terminals (a2, b2, c2) of the second converter element connected to the converter terminals, and - a switch controller (118) for producing one or more switch-control signals suitable for controlling first controllable power electronic switch or switches (105, 106) of the first converter element and suitable for controlling second controllable power electronic switch or switches (107, 108) of the second converter element, characterized in that the converter device comprises a signal router (119) controllable to operate in a first operational mode where the signal router is configured to deliver the one or more switch-control signals to the first converter o 20 element without delivering the one or more switch-control signals to the second > converter element, and in a second operational mode where the signal router is 5 configured to deliver the one or more switch-control signals to the second converter I element without delivering the one or more switch-control signals to the first = converter element. a = 25
2. A converter device according to claim 1, wherein the signal router (119) is
LO O controllable to operate in a third operational mode where the signal router is
O N configured to deliver the one or more switch-control signals to both the first and second converter elements.
3. A converter device according to claim 2, wherein the converter device comprises a control system (114) configured to control the signal router from the first operational mode to the second operational mode via the third operational mode.
4 A converter device according to claim 2 or 3, wherein the converter device comprises a control system (114) configured to control the signal router from the second operational mode to the first operational mode via the third operational mode.
5. Aconverter device according to any of claims 1-4, wherein the first controllable power electronic switch or switches has or have smaller switching losses than the second controllable power electronic switch or switches, and the second controllable power electronic switch or switches has or have a greater maximum allowable current than the first controllable power electronic switch or switches.
6. A converter device according to any of claims 1-5, wherein the converter device comprises a measurement system (115) for producing measurement data dependent on loading of the converter device, and a control system (114) for controlling the signal router based on the measurement data.
7. A converter device according to any of claims 1-6, wherein the converter device comprises a first filter (103) between the terminals (a1, b1, c1) of the first converter element and the converter terminals (L1, L2, L3), and a second filter (104) o between the terminals (a2, b2, c2) of the second converter element and the > converter terminals (L1, L2, L3). >
8. Aconverter device according to any of claims 1-7, wherein the first converter - element (101, 201) is a first inverter bridge and each of the one or more second E 25 voltages is alternating voltage, the second converter element (102, 202) is a second = inverter bridge and each of the one or more third voltages is alternating voltage. 3 S
9. Adirect voltage distribution system comprising: - a direct voltage distribution network (350),
- at least one network converter (351) for transferring electric power between an alternating voltage supply network (352) and the direct voltage distribution network, and - at least one converter device (300, 320, 330) according to claim 8 for transferring electric power between the direct voltage distribution network and at least one alternating voltage network (354, 355, 356) of a customer.
10. A method for controlling a converter device that comprises at least one first converter element for supplying electric power to an electric system external to the converter device, at least one second converter element for supplying electric power to the electric system, and a switch controller producing one or more switch-control signals suitable for controlling controllable power electronic switch or switches of the first converter element and suitable for controlling controllable power electronic switch or switches of the second converter element, characterized in that the method comprises connecting (401) the one or more switch-control signals to the second converter element and disconnecting the one or more switch-control signals from the first converter element in response to a transition from a first operational mode of the converter device to a second operational mode of the converter device, and connecting (402) the one or more switch-control signals to the first converter element and disconnecting the one or more switch-control signals from the second converter element in response to a transition from the second operational mode of the converter device to the first operational mode of the converter device. oO
O
N
S
I a a 0 Oo
LO o
O
N
FI20195018A 2019-01-11 2019-01-11 A converter device and a method for controlling a converter device FI128738B (en)

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Application Number Priority Date Filing Date Title
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FI20195018A1 true FI20195018A1 (en) 2020-07-12
FI128738B FI128738B (en) 2020-11-13

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