Power Converter

Abstract

An electrical converter (100) for converting an AC signal having three phase voltages into a DC signal comprises three phase terminals (A, B, C), a first DC terminal (P) and a second DC terminal (N), a first converter stage (11) configured to convert between the AC signals at the at least three phase terminals and a first signal at a first intermediate node (x) and a second intermediate node (y), and a second converter stage (12) operable to convert between a second signal at a third and fourth intermediate node (r, s) and a DC signal at the first and second DC terminals (P, N), the second converter stage comprising at least one active switch (S xm , S my and a second converter stage (12) comprising a first intermediate node (x) and a third intermediate node (r) and a fourth intermediate node (s). The links connect the first intermediate node (x) to the third intermediate node (r) and the second intermediate node (y) to the fourth intermediate node (s). The current injection circuit comprises a second active switch. The controller (40) controls the at least one first active switch (S xm , S my The controller (40) implements a first operating mode in which the third and fourth intermediate nodes (r, s) are continuously connected to the first and second DC terminals (P, N), respectively, such that the second converter stage (12) is inoperative and the second active switch is operated by pulse width modulation.

Description

[Technical Field]

[0001] The present invention relates to the field of power conversion, and in particular to an electrical converter and a method for operating an electrical converter. [Background technology]

[0002] When an electric vehicle's battery is charged, AC voltage from the electric grid is converted by an electrical converter to DC voltage, which is then provided to the battery being charged. For example, the electrical converter may convert the three-phase AC voltage to a DC voltage across a DC bus to which the vehicle's high-voltage (e.g., 800 V) battery can be connected. Wireless charging systems for electric vehicles, or gradient amplifiers for magnetic resonance imaging (MRI) scanners, also typically require such three-phase AC-to-DC conversion to create a high-voltage DC bus from which power can be drawn.

[0003] Typically, for example, when a load draws power from the DC output of an electrical converter, the current drawn by the electrical converter from each phase of a three-phase grid must be substantially sinusoidal and substantially in phase with the sinusoidal voltage of that particular phase, resulting in a power factor substantially equal to unity. Thus, three-phase AC-DC conversion advantageously requires a three-phase power factor correcting (PFC) electrical AC-DC converter. In addition, such PFC converters typically require low distortion of the grid current, e.g., low total harmonic distortion (THD).

[0004] Typically, when the voltage across the DC bus terminals is higher than the full-wave rectified AC voltage, a boost-type electrical converter with a boost PFC stage having a DC output of 700-800V is used.

[0005] The output of the boost PFC converter is typically delivered to a series-connected, galvanically isolated DC-DC converter stage, which generates the final output voltage and / or battery charging current. The operation and control of both converter stages are often separated, allowing the two stages to be commissioned separately. However, when the required output voltage is low, which may be the case when the battery is heavily depleted, the isolated DC-DC converter stage must fully absorb the high voltage ratio, which places stress on the converter components and requires them to be larger in size, shortening their useful life and increasing their cost. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO2020 / 035527 Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is to provide a converter system of the above type, and in particular to provide an electrical converter for three-phase boost PFC AC-DC conversion that makes it possible to overcome the above-mentioned drawbacks. [Means for solving the problem]

[0008] According to a first aspect of the present invention there is therefore provided an electrical converter as set out in the accompanying claims.

[0009] The electrical converter according to the present invention converts an AC signal having three phase voltages into a DC signal, preferably a DC voltage. The electrical converter comprises three phase terminals, a first DC terminal and a second DC terminal, a first converter stage, a second converter stage, a current injection circuit, and a control unit. The electrical converter optionally comprises a neutral terminal for connecting a neutral conductor of the grid. The first converter stage is operably coupled to the three phase terminals and comprises a first intermediate node and a second intermediate node. The first converter stage is configured to convert between the AC signals at the three phase terminals and a first signal at the first intermediate node and the second intermediate node. The first signal can be a (switched) voltage or a current. The second converter stage is operably coupled to the first and second DC terminals and comprises a third intermediate node and a fourth intermediate node. The second converter stage comprises at least one first active switch and is operable to convert between a second signal, e.g., a (switched) voltage or current, at the third and fourth intermediate nodes and a DC signal at the first and second DC terminals.

[0010] Links connect the first intermediate node to the third intermediate node and the second intermediate node to the fourth intermediate node, and the links may be DC links and may include electrical energy storage elements such as capacitors and / or inductors, or alternatively may not include electrical energy storage elements.

[0011] The current injection circuit is operable to connect between the phase terminal having the smallest instantaneous absolute voltage value of the three phase voltages and the first and second DC terminals, or between the phase terminal having the smallest instantaneous absolute voltage value and the first and second intermediate nodes via the second active switch.

[0012] The control unit (or controller) implements a first operating mode in which at least one first active switch and a second active switch are operated by pulse-width modulation. The second converter stage comprises or is constituted by a voltage boost circuit, enabling the electric converter to obtain a DC voltage at the first and second DC terminals higher than the instantaneous full-wave rectified voltage of the phase voltages of the AC signal in the first operating mode. This can be obtained by operating the first active switch and possibly the second active switch (of the current injection circuit) by pulse-width modulation (via the control unit).

[0013] According to the present invention, the control unit is configured to implement a second operating mode in which the second active switch is operated with pulse width modulation (via the control unit) while the second converter stage, e.g., the boost circuit, is not operating and, in particular, the third and fourth intermediate nodes are continuously connected to the first and second DC terminals, respectively, so that DC voltages at the first and second DC terminals equal to the instantaneous full-wave rectified voltages of the phase voltages of the AC signal can be obtained.

[0014] One advantage of the present invention is that the second operating mode allows the average DC bus voltage to be reduced when a lower voltage is required by the load. This reduces stress on any converter stages connected to the DC terminals. Another advantage is that by continuously operating the current injection circuit during the second operating mode, a sinusoidal current and unity power factor can be obtained on the AC side while the DC signal is a pulsating voltage (and current). This is especially true when a third converter stage, such as a (galvanically isolated) DC / DC converter or DC / AC converter, advantageously operated in constant power mode, is connected to the first and second DC terminals.

[0015] The current injection circuit can be implemented in various ways. One implementation includes a phase selector including a third active switch configured to selectively connect three phase terminals to a fifth intermediate node, and a second active switch operable to connect the fifth intermediate node to the first DC terminal and the second DC terminal. The control unit is configured to control the switching of the third active switch according to a switching pattern in which the phase terminal with the lowest instantaneous absolute voltage value is continuously connected to the fifth intermediate node. An alternative implementation integrates the current injection circuit into an active bridge converter of the first converter stage. By active (pulse-width modulation) control of the active switches of the active bridge converter, the phase terminal with the lowest instantaneous absolute voltage value can be connected to the first and second intermediate nodes.

[0016] An electrical converter according to the present invention may include one or more voltage measurement sensors for measuring phase voltages of the AC signal and / or voltages at the first and second DC terminals and / or voltages at the first and second intermediate nodes. The controller may be operably coupled to the voltage measurement sensors and may include a first input for receiving a third signal representing the set or measured voltage at the first and second DC terminals. The controller may be configured to determine a threshold value representing an instantaneous full-wave rectified voltage value of the AC signal and, based on a comparison between the third signal and the threshold value, automatically switch operation to the second operating mode, for example, if the (voltage) value of the third signal is equal to or less than the threshold value.

[0017] According to a second aspect of the present invention, there is provided a battery charging system, an electric motor drive system, or a magnetic resonance imaging apparatus, comprising a power supply unit, the power supply unit comprising the electric converter of the first aspect.

[0018] According to a third aspect, a method for converting a three-phase AC input to a DC output is described herein, the method being advantageously implemented in the electrical converter as described above.

[0019] One aspect of the present invention relates to an electrical converter that can be used to convert a three-phase AC voltage from an electrical grid, which can be low voltage (e.g., 380-400 Vrms at 50 Hz frequency), to a high DC output voltage (e.g., 800 V).

[0020] Aspects of the present invention will now be described in more detail with reference to the accompanying drawings, in which like reference numerals refer to like features, and in which: [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 illustrates a schematic diagram of an electrical transducer that is unidirectional, according to one embodiment of the present invention. [Figure 2A] 1 is a diagram with voltages over a 360° period of an AC mains voltage, illustrating the overall operating principle of an electrical converter according to an embodiment of the present invention; FIG. [Figure 2B] 1 is a diagram with voltages over a 360° period of an AC mains voltage, illustrating the overall operating principle of an electrical converter according to an embodiment of the present invention; FIG. [Figure 2C] 1 is a diagram with voltages over a 360° period of an AC mains voltage, illustrating the overall operating principle of an electrical converter according to an embodiment of the present invention; FIG. [Figure 2D] 1 is a diagram with currents during a 360° period of an AC mains voltage, illustrating the overall operating principle of an electrical converter according to an embodiment of the present invention; FIG. [Figure 2E] 1 is a diagram with currents during a 360° period of an AC mains voltage, illustrating the overall operating principle of an electrical converter according to an embodiment of the present invention; FIG. [Figure 2F] 1 is a diagram with switching states of a phase selector switch during a 360° period of an AC mains voltage, illustrating the overall operating principle of an electrical converter according to an embodiment of the present invention; FIG. [Figure 2G] FIG. 1 is a diagram showing the switching states of the switches of the boost circuit (upper and lower) and the boost / buck circuit during a 360° period of the AC mains voltage, illustrating the overall operating principle of an electrical converter according to an embodiment of the present invention. [Figure 3]1 is a block diagram of an advantageous implementation of a central control unit and a control method according to an embodiment of the present invention; [Figure 4A] 1 is a diagram showing the voltage, current, and switching states of the boost bridge legs (upper and lower) and the buck-boost bridge legs of an electric converter within five consecutive switching cycles, illustrating PWM modulation of these bridge legs according to one embodiment of the present invention. [Figure 4B] 1 is a diagram showing the voltage, current, and switching states of the boost bridge legs (upper and lower) and the buck-boost bridge legs of an electric converter within five consecutive switching cycles, illustrating PWM modulation of these bridge legs according to one embodiment of the present invention. [Figure 4C] 1 is a diagram showing the voltage, current, and switching states of the boost bridge legs (upper and lower) and the buck-boost bridge legs of an electric converter within five consecutive switching cycles, illustrating PWM modulation of these bridge legs according to one embodiment of the present invention. [Figure 5] FIG. 1 illustrates a schematic diagram of a bidirectional electrical transducer according to an embodiment of the present invention. [Figure 6] FIG. 2 shows a schematic diagram of an electrical converter that is unidirectional and has an input filter located before the first converter stage instead of after it, according to an embodiment of the present invention. [Figure 7A] 3A to 3C show different variants of the first converter stage that can be used in the electrical converter of the present invention; [Figure 7B] 3A to 3C show different variants of the first converter stage that can be used in the electrical converter of the present invention; [Figure 8A] FIG. 10 shows another variant of the first converter stage that can be used in the electrical converter of the present invention. [Figure 8B] FIG. 10 shows another variant of the first converter stage that can be used in the electrical converter of the present invention. [Figure 9]FIG. 1 illustrates an electrical converter according to an embodiment of the present invention that is unidirectional and includes a connection terminal for connection to a grid neutral conductor (fourth phase). [Figure 10A] 1 is a diagram showing three-phase mains voltages va, vb, and vc. [Figure 10B] 1 is a diagram illustrating the output voltage VDC across the output terminals P, N and the corresponding output current iDC, together with the BoostOn signal for controlling whether the boost circuits 19, 20 are operated. [Figure 11] 1 is a diagram showing the DC terminals of an electrical converter according to the invention to which isolated DC / DC converter stages are connected. [Figure 12] FIG. 10 illustrates a topology of an electrical converter according to another embodiment of the present invention. [Figure 13A] 1 is a diagram showing three-phase mains voltages va, vb, and vc. [Figure 13B] 1 is a diagram illustrating the output voltage VDC (also called VPN) across the output terminals P, N and the corresponding output current IDC, together with the BoostOn signal for controlling whether the boost circuits 19, 20 are operated. [Figure 14] FIG. 1 illustrates a battery charging system according to an aspect of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0022] 1 shows an electrical converter 100, called a Dutch rectifier, comprising two converter stages 11, 12 in the form of a three-phase active phase selector 11 and a DC / DC stage 12. The electrical converter 100 further comprises an input filter 13 and an output filter 15.

[0023] The electrical converter 100 is an AC-DC converter having three phase inputs A, B, C connected to the three-phase voltage of a three-phase AC grid 21 and two DC outputs P, N which may for example be connected to a DC load 22 such as a high voltage (e.g. 800V) battery of an electric vehicle.

[0024] The first converter stage 11 comprises three phase connections a, b, c connected to three phase inputs A, B, C, and three outputs x, y, z, which may be considered as an upper intermediate voltage node x, a lower intermediate voltage node y, and a middle intermediate voltage node z.

[0025] The first converter stage 11 comprises two passive semiconductor devices (diode D for leg 16) connected in a half-bridge configuration. ax and D ya , D for Leg 17 bx and D yb , D for Leg 18 cx and D yc ) each having three bridge legs 16, 17, 18; and three selector switches (S aza , S bzb , and S czc and a phase selector 25 comprising a phase selector 25a, 25b, 25c, 25d, 25e, 25f, 25g, 25g, 25h, 25h, 25g ...

[0026] The DC / DC stage 12 comprises or consists of two stacked boost bridge legs 19, 20 and one buck-boost bridge leg 14. Each boost bridge leg (19, 20) includes a boost switch (S for the upper boost bridge leg 19) connected in a half-bridge configuration. xm , and S for the lower boost bridge leg 20 my ) and the boost diode (D for the upper boost bridge leg 19 xP , and D for the lower boost bridge leg 20 NyThe buck-boost bridge leg 14 comprises two buck-boost switches (S Pz and S zN The middle node r of the upper boost bridge leg 19 is connected to the upper boost inductor L x and the middle node s of the lower boost bridge leg 20 is connected to the intermediate voltage node x via the lower boost inductor L y and the middle node t of the buck-boost bridge leg 14 is connected to the middle buck-boost inductor L z is connected to the intermediate voltage node z via

[0027] The common node m of the upper and lower boost bridge legs 19 and 20 is advantageously connected to a mid-voltage node q of the output filter 15 to form two stacked two-level boost circuits. The output filter 15 includes two output filter capacitors C connected in series between the upper and lower output nodes P and N. Pm , C mN and capacitor C Pm and capacitor C mN and a mid-voltage node q forming an intermediate node between

[0028] The upper boost bridge leg 19 is connected between the upper output node P and the common node m (i.e., the upper output filter capacitor C Pm ) and switch S xm When the diode D is open (not conducting, in the off state), xP Current can flow from the intermediate voltage node x to the upper output node P through the switch S xm When switch S is closed (conducting, on state), xm The boost switch (S) of the boost bridge leg 19 is arranged so that current can flow from the intermediate voltage node x to the common node m (or vice versa) through the xm ) is an actively switchable semiconductor device, such as a MOSFET.

[0029] The lower boost bridge leg 20 is connected between the common node m and the lower output node N (i.e., the lower output filter capacitor C mN ) and switch S my When the diode D is open (not conducting, in the off state), Ny Current can flow from the lower output node N to the intermediate voltage node y through the switch S my When switch S is closed (conducting, on state), my The boost switch (S) of the boost bridge leg 20 is arranged so that current can flow from the common node m to the intermediate voltage node y (or vice versa) through the my ) is an actively switchable semiconductor device, such as a MOSFET.

[0030] The buck-boost bridge leg 14 is connected between the upper output node P and the lower output node N (i.e., in parallel with the DC load 22), and the switch S zN is open (not conducting, off state), switch S Pz When is closed (conducting, on state), current flows from the intermediate voltage node z to the upper output node P (or vice versa), and the switch S Pz is open (not conducting, off state), switch S zN The buck-boost switch (S) of the buck-boost bridge leg 14 acts as a current injection circuit arranged to allow current to flow from the intermediate voltage node z to the lower output node N (or vice versa) when it is closed (conducting, on state). Pz , S zN ) are actively switchable semiconductor devices, e.g., MOSFETs, that are controlled in a complementary manner (i.e., one is closed while the other is open, or vice versa).

[0031] Advantageously, three high frequency (HF) filter capacitors C are part of the input filter 13. x , C y , C zinterconnects the intermediate voltage nodes x, y, and z in a star-connected configuration. In general, to load the AC grid symmetrically, three capacitors C x , C y , C z Advantageously, have substantially equal values.

[0032] According to one aspect of the present invention, the controller is configured to operate according to a first operating mode, referred to as normal operation, and a second operating mode, referred to as democratic operation, as further described herein.

[0033] The central control unit 40 advantageously controls all the controllable semiconductor devices (switches) of the electrical converter 100 and sends control signals to each switch via the communication interface 50. In particular, the semiconductor devices S aza , S bzb , S czc , S xm , S my , S Pz , S zN is controlled by the controller 40. Furthermore, the control unit 42: AC grid phase voltage v a , v b , v c , 43: Inductor current i Lx , i Ly , i Lz , 44: DC bus voltage V DC , 45: DC bus midpoint voltage V mN =-V Nm Measurement input ports (42, 43, 44, 45) for receiving measurements of the desired DC output voltage V * PN The operation of the controller is particularly dependent on the inductor current i during normal operation. Lx , i Ly , i Lz This allows a piecewise sinusoidal shape to be achieved.

[0034] The electrical converter 100 shown in FIG. 1 is unidirectional because the input stage 11 and output power stage 12 include diodes, allowing power to be drawn from the electrical AC grid 21 and only to provide this power to a load 22 at the output. On the other hand, FIG. 5 shows a bidirectional electrical converter 200 in accordance with the present invention. The electrical converter 200 is bidirectional because the input stage 11 and output power stage 12 include diodes, allowing power to be drawn from the electrical AC grid 21 and only to provide this power to a load 22 at the output. ax , D bx , D cx , D ya , D yb , D yc ) and the diode (D xP , D Ny ) respectively correspond to the controllable semiconductor switches (S xa , S xb , S xc , S ay , S by , S cy ) in the output power stage 12 and (S yN , S Px ) is replaced by converter 100.

[0035] The electrical converter 200 may comprise a switching device 23 connected between the upper node of the bridge converter 24 and the upper intermediate node x. The switching device 23 makes it possible to interrupt the electrical connection between the bridge rectifier 24 and the upper intermediate node x. The switching device 23 is provided as a semiconductor switch, for example a MOSFET, but may alternatively be any suitable switching device, such as a relay switch. The switching device 23 is advantageously operably connected to the controller 40. Alternatively, or in addition, a switching device identical to the device 23 may be provided between the lower node of the bridge converter 24 and the lower intermediate node y.

[0036] 6, an electrical converter 300 is shown which differs from converter 100 in that the input filter 13 is placed before (rather than after) the first converter stage 11, i.e., the input filter 13 is connected between the phase input terminals A, B, C and the first converter stage 11. The first converter stage 11 is connected to the corresponding inductor L of the input filter 13. a , L b , L c The phase input terminals A, B, and C are connected to the intermediate nodes x, y, and z through the capacitor C. a , C b , C c is placed between the phase input terminal and the inductor. As in the previous example, the capacitors are connected in a star configuration, with the star point advantageously connected to the midpoint of the output filter 15. Alternatively, the capacitor C a , C b , C c can be arranged in a delta configuration across the three phase input lines. It may be useful to note that in the example of Figure 6, the voltages at switch nodes r, s, and t are identical to the voltages at intermediate nodes x, y, and z, so the voltage signals at the three intermediate nodes x, y, and z are somewhat different compared to the previous examples (Figures 1 and 5). As a result, high frequency currents flow through the first converter stage 11, whereas in the previous examples (Figures 1 and 5), high frequency currents only occur in the output power stage downstream of the input filter 13.

[0037] In any of the electrical converters 100, 200, and 300, the diodes may be replaced with actively switchable semiconductor devices to allow for bidirectional power flow in the electrical converters.

[0038] In any of the electrical converters 100, 200, and 300, the HF capacitor C x , C y , C z (or C in the case of Figure 6) a , C b , C c) are connected in a star configuration. The voltage at the star point connection can be controlled by controlling the voltage at the common node m.

[0039] 7A and 7B show different variations of the first converter stage 11 that can be used in the electrical converter of any of FIGS.

[0040] 8A-8B further variants of the first converter circuit 11 are shown. In these variants, the three bridge legs 16, 17 and 18 of the phase selector are arranged as half-controlled thyristor legs (FIG. 8A), i.e. the thyristors Thy and Thy are arranged in the bridge leg parts connected to the upper intermediate node. ax , Thy bx , Thy cx and with a diode in the other bridge leg portion connected to the lower intermediate node (or vice versa), or arranged as a full control thyristor leg (FIG. 8B), i.e., with a thyristor Thy in each bridge half leg instead of a diode. ax , Thy bx , Thy cx , Thy ya , Thy yb , Thy yc Such a phase selector can be used to selectively charge the output filter capacitor C without the need for additional pre-charge circuitry. Pm , C mN , or C PN This allows the input to be controllably precharged.

[0041] Referring to FIG. 9 , electrical converter 400 differs from electrical converters 100, 200, or 300 in that it includes a connection terminal n for connecting the neutral conductor of a three-phase AC grid. In some applications, such as charging electric vehicles, it is often necessary to be able to independently control the amplitude of the sinusoidal current drawn from each phase of the three-phase grid so that the load on a particular phase can be reduced so that other consumer devices can still draw power from that particular phase while charging the vehicle's battery without overloading the phase. In this case, connection terminal n is advantageously connected to the neutral conductor of the three-phase grid, allowing a return current substantially equal to the sum of the three phase currents to return to the grid's neutral conductor. In one advantageous embodiment, the three phase currents can be completely independently controlled by providing a common node connected to the input neutral conductor.

[0042] The neutral connection terminal n is advantageously connected to an AC capacitor C x , C y , C z and to the common node m of the stacked boost bridges 19, 20 (and therefore also to the midpoint of the output filter 15). This results in a fully symmetrical converter structure. In this case, the voltages at the star point and at the common node are equal to the voltage of the grid neutral conductor.

[0043] Normal operation of the electrical converter During normal operation, switching device 23 is kept closed (conducting) to apply the phase input with the highest voltage by bridge rectifier 24, if present, to upper intermediate node x.

[0044] Figure 1 (or diode D ax , D bx , D cx , D ya , D yb , D yc , and D xP , D Ny The references to the active switch S xa , S xb , S xc, S ay , S by , S cy , and S Px , S yN 5), the bridge leg of bridge rectifier 24 connected to phase input A, B, or C having the highest voltage of the three-phase AC input voltage is switched so that the corresponding phase input A, B, or C is connected to the upper intermediate voltage node x. To accomplish this, the bridge legs are switched by the bridge leg's corresponding selector switch (S aza , S bzb , S czc ) is open (not conducting, OFF state), the corresponding phase connection a, b, or c is connected to the upper diode (D ax , D bx , D cx ) to node x. The bridge leg of rectifier 24 connected to phase input A, B, or C having the lowest voltage of the three-phase AC input voltage is switched so that the corresponding phase input A, B, or C is connected to the lower intermediate voltage node y. To accomplish this, the bridge legs are switched by the bridge leg's corresponding selector switch (S aza , S bzb , S czc ) is open (not conducting, in the OFF state), the corresponding phase connection a, b, or c is connected to the lower diode (D ya , D yb , D yc ) to node y. Phase inputs A, B, or C having a voltage between the highest and lowest voltages of the three-phase AC input voltage are connected to the mid-level intermediate voltage node z by phase selector 25. To accomplish this, phase selector 25 connects the corresponding phase connection a, b, or c to a closed (conducting, on) selector switch (S aza , S bzb , S czc ) to node z.

[0045] In a three-phase AC grid with substantially balanced phase voltages, for example as shown in FIG. 2A, a three-phase AC input voltage (shown in FIG. 2A) is balanced into three intermediate DC voltages (v) provided between an upper intermediate voltage node x, a lower intermediate voltage node y, and a middle intermediate voltage node z. xz , v zy , v xy 2B). These DC voltages therefore exhibit a piecewise sinusoidal waveform. The conversion of the three-phase AC input voltage into three intermediate DC voltages is the result of the operation of the first converter stage 11, as explained above. The selector switch (S aza , S bzb , S czc ) are shown in FIG. 2F. It can be seen that the switches are continuously "on" or "off" throughout a particular 60° sector within the 360° period of the AC mains voltage. Also, the diodes of bridge rectifier 24 are "conducting" or "not conducting" throughout a particular sector, e.g., 60°, within the 360° period of the AC mains voltage. The combination of switch and diode states is unique for each 60° sector of the three-phase AC input voltage and depends on the voltage values ​​of the phase inputs (A, B, C). The sequence of six unique switch and diode states repeats itself every 360° period of the AC mains voltage.

[0046] Looking from the viewpoint of the intermediate voltage nodes x, y, and z towards the output terminals P and N, the HF filter capacitor C x and the upper boost inductor L x , the upper boost bridge leg 19, and the upper output capacitor C Pm The input voltage of this high-order boost circuit is supplied to the capacitor C x voltage across v Cx (shown in FIG. 2C), and the output voltage of this upper boost circuit is a voltage value (V Pm ≒V DC / 2) with the upper output capacitor C Pm Voltage V across PmThe upper boost circuit is formed by the upper boost inductor L x To control the current at a specified, possibly variable, switching frequency f s Switch S in xm It can be operated by PWM modulation.

[0047] Looking from the viewpoint of the intermediate voltage nodes x, y, and z towards the output terminals P and N, the HF filter capacitor C y and the lower boost inductor L y , the lower boost bridge leg 20, and the lower output capacitor C mN A conventional "inverting" (negative input voltage and negative output voltage) DC-DC boost circuit (lower boost circuit) is formed, which has an input voltage of a capacitor C y voltage across v Cy (shown in FIG. 2C), and the output voltage of this lower boost circuit is a voltage value substantially equal to minus half of the total DC bus voltage (V Nm ≒-V DC / 2) with the lower output capacitor C mN Voltage V across Nm The formed lower boost circuit is y To control the current at a specified, possibly variable, switching frequency f s Switch S in my It can be operated by PWM modulation.

[0048] Looking from the viewpoint of the intermediate voltage nodes x, y, and z towards the output terminals P and N, the HF filter capacitor C z and the intermediate buck-boost inductor L z , the buck-boost bridge leg 14, and the output capacitor C Pm , C mN A conventional DC-DC buck-boost circuit (mid-level buck-boost circuit) is formed with a series connection of a capacitor C. This DC-DC buck-boost circuit can be seen as similar to a single-phase half-bridge voltage-source converter (VSC). The input voltage of this mid-level buck-boost circuit is connected to a capacitor C. zvoltage across v Cz (shown in FIG. 2C), and the output voltage of this intermediate buck-boost circuit is Pm , C mN The output voltage V across a series connection of DC The intermediate buck-boost circuit is formed by the intermediate buck-boost inductor L z To control the current at a specified, possibly variable, switching frequency f s Switch S in Pz , S zN It can be operated by PWM modulation.

[0049] Figure 2G shows the switch S in the upper boost bridge leg 19. xm and the state of switch S in the lower boost bridge leg 20. my and the state of switch S in middle buck-boost bridge leg 14. Pz The state of the switch S zN The state of switch S Pz (Note that this is the complement of the state of switch S.) xm , S my , S Pz , S zN are all PWM modulated as can be seen from the black colored bars which indicate the PWM modulation of the corresponding switches.

[0050] Inductor L x , L y , L z Current i at Lx , i Ly , i Lz An example of the three sinusoidal AC phase currents i shown in Figure 2E is shown in Figure 2D. As can be seen, these currents are controlled to have a piecewise sinusoidal shape, i.e., the operation of the first converter stage 11 results in the three sinusoidal AC phase currents i a , i b , converted to ic.

[0051] Figure 3 shows a block diagram of an advantageous implementation of the central control unit 40 of Figure 1 during a first operating mode, referred to as normal operation. The electrical converter 100 is shown in Figure 3 as a "single-wire" equivalent circuit, with the annotations of the elements corresponding to those given in Figure 1. The three slashes in the signal lines indicate the bundling of the three phase signals and may represent a transition to vector representation.

[0052] The control unit 40 targets the output voltage V PN the requested setpoint V received from the external unit via input port 41. * PN and, for example, the lower output capacitor C mN By controlling the voltage across the two output capacitors C to be substantially equal to half the DC bus voltage, Pm and C mN In addition, the currents drawn from the phase inputs (a, b, c) must be controlled to be substantially sinusoidal in shape and substantially in phase with the corresponding phase voltages. As explained previously, this means that the phase currents i a , i b , i c Instead of directly controlling the inductor current i Lx , i Ly , i Lz This can also be achieved by controlling the HF filter capacitor (C x , C y , C z ) controls the low-pass filtered value of the inductor current.

[0053] Output voltage V DCThe control of is advantageously performed using a cascade control structure comprising an outer voltage control loop 60 and an inner current control loop 70. The setpoint of the output voltage is input to a comparator 61 via an input port 41 and compared with a measured output voltage obtained from a measurement processing unit 95 (e.g., comprising a low-pass filter). The output of the comparator 61 is a control error signal for the output voltage, which is further input to a control element 62 (e.g., comprising a proportional-integral control block) which outputs instantaneous setpoint values ​​of the amplitudes of the phase currents. These amplitudes are input to a multiplier 63 where they are multiplied by a signal obtained from a calculation element 64 which outputs a normalized instantaneous value of the phase voltage. The input of the calculation element 64 is the measured phase voltage obtained from the measurement processing unit 93 (e.g., comprising a low-pass filter). The output of the multiplier 63 is the instantaneous, e.g., low-pass filtered, phase current i a , i b , i c Set value for i * a , i * b , i * c and is substantially sinusoidal and substantially in phase with the corresponding phase voltage. * a , i * b , i * c is input to the current controller 70 after passing through a summing element 67 and a selection element 81, the functions of which are explained in more detail in the following text.

[0054] The current controller 70 is divided into three individual current controllers 71 , 74 , 77 . The individual current controller 71 controls the middle buck-boost inductor L z This control is used to control the current in switch S of the mid-buck-boost circuit including mid-buck-boost bridge leg 14. Pz , S zNAs a result of the operation of the first converter stage 11, the controller 71 controls the currents of the phase inputs A, B, C to have voltages between the highest and lowest voltages of the three-phase AC voltage. The individual current controller 74 controls the upper boost inductor L x This control is used to control the current in switch S of the upper boost circuit, including upper boost bridge leg 19. xm As a result of the operation of the first converter stage 11, the controller 74 accordingly controls the current in the phase input A, B, C having the highest voltage of the three-phase AC voltage. The individual current controller 77 controls the lower boost inductor L y This control is used to control the current in the switch S of the lower boost circuit, including the lower boost bridge leg 20. my As a result of the operation of the first converter stage 11, the controller 77 accordingly controls the current in the phase input A, B, C having the lowest voltage of the three-phase AC voltage.

[0055] The selector element 81 selects a set value i for the instantaneous phase current depending on the voltage values ​​of the phase inputs (A, B, C). * a , i * b , i * c (shown in Figure 2D) to the correct individual current controllers (71, 74, 77), resulting in the inductor current setpoint i for each inductor current controller. * Lx , i * Ly , i * Lz (shown in Figure 2E) was obtained. The setpoints of the phase currents of the phase inputs A, B, and C having the highest voltages of the three-phase AC voltages are sent to the individual current controllers 74, resulting in the setpoints i * Lx is obtained, The setpoints of the phase currents of the phase inputs A, B, and C having the lowest voltage of the three-phase AC voltage are sent to the individual current controllers 77, resulting in the setpoints i * Ly is obtained, The setpoints of the phase currents of the phase inputs A, B, and C having voltages between the highest and lowest voltages of the three-phase AC voltage are sent to the individual current controllers 71, so that the setpoints i * Lz is obtained.

[0056] In each individual current controller, the received set value for the instantaneous inductor current (i * Lx , i * Ly , i * Lz ) is input to a comparator, e.g., comparator 72 of individual current controller 71, and compared with the measured inductor current obtained from measurement value processing unit 94 (e.g., comprising a low-pass filter). The output of the comparator is a current control error signal, which is further input to a control element, e.g., control element 73 of individual current controller 71, the output of which is input to a PWM generating element, e.g., PWM generating element 54 of individual current controller 71. The PWM generating elements of the individual current controllers generate PWM modulated control signals for controllable semiconductor switches of the PWM controlled bridge legs, i.e., upper boost bridge leg 19 of the upper boost circuit, lower boost bridge leg 20 of the lower boost circuit, and middle buck-boost bridge leg 14 of the middle buck-boost circuit. These PWM modulated control signals are transmitted to the appropriate bridge legs via communication interface 50.

[0057] The selector switches of the first converter stage 11 are either "on" or "off" during each 60° selector of the three-phase AC input voltage depending on the voltage values ​​of the phase inputs (A, B, C). The control signals for the selector switches are generated by switch signal generators 51, 52, 53.

[0058] The DC bus midpoint balancing is performed by multiplier 63 using the instantaneous, e.g., low-pass filtered, phase current i a , i b , i c Set value for i * a , i * b , i * c The offset value may be achieved by adding an offset value to the measured DC bus midpoint voltage obtained from the measurement processing unit 96 (e.g., comprising a low-pass filter) using the comparator 65, relative to a set value (e.g., V DC / 2) and feeding the error signal output by the comparator 65 to the control element 66.

[0059] The phase current i shown in Figure 2E a , i b , i c is obtained by controlling the electrical converter 100 using such a control unit 40 and control method described in the preceding paragraphs. Figure 2E shows an example of an instantaneous, e.g., low-pass filtered, phase current i as input to the selector element 81 shown in Figure 3. a , i b , i c Set value for i * a , i * b , i * c As explained above, the phase current i a , i b , i c are indirectly controlled, i.e., they are controlled by the inductor current i Lx , i Ly , i Lz 2D) and the operation of the first converter stage 11. The set value for the inductor current (i * Lx , i * Ly , i * Lz ) is set by selector element 81 to a set value i based on the measured phase voltage.* a , i * b , i * c is derived from

[0060] 4A-4C show five successive switching cycles (i.e., each 1 / f s The switching period T is equal to s and f s is the switching frequency). Within this sector, the selector switches and diodes of the first converter stage 11 are in the following switching states: Switch S aza =0 (off), diode D ax =1 (conducting), diode D ya =0 (blocked), phase connection a is connected to node x; Switch S bzb =0 (off), diode D bx =0 (blocking), diode D yb =1 (conducting), phase connection b is connected to node y; Switch S czc =1 (on), diode D cx =0 (blocking), diode D yc =1 (conducting), phase connection c is connected to node z is located.

[0061] The diagrams in Figures 4A-4C show voltage, current, and switching signals over a time axis of milliseconds. Figure 4A corresponds to the operation of the upper boost circuit, and the corresponding inductor current i Lx (and this current setting i * Lx ) and the inductor voltage v Lx and the control signal S of the switch of the PWM modulated upper boost bridge leg 19. xm FIG. 4B shows the operation of the lower boost circuit and the corresponding inductor current i Ly (and this current setting i *Ly ) and the inductor voltage v Ly and the control signal S of the switch of the PWM modulated lower boost bridge leg 20. my FIG. 4C shows the operation of the intermediate buck-boost circuit and the corresponding inductor current i Lz (and this current setting i * Lz ) and the inductor voltage v Lz and the control signal S of the upper switch of the PWM modulation bridge leg 14. Pz The control signal S of the lower switch of the PWM modulation bridge leg 14 is zN is the control signal S Pz Note that this is the complement of

[0062] To minimize the total harmonic distortion (THD) of the AC input current of the electrical converter, the phase current i a , i b , i c High frequency ripple in the .times. ...

[0063] An advantage of the electrical converter 100 is that the half-switching-period volt-second area of ​​the upper boost inductor and the half-switching-period volt-second area of ​​the lower boost inductor are smaller than those of the boost inductors of a conventional six-switch boost PFC rectifier. This is because the voltage applied to these inductors is lower than that of the boost inductors of a conventional six-switch boost PFC rectifier. For the middle buck-boost inductors, the applied voltage is not necessarily lower, but the current flowing through them is smaller than that of the inductors of a conventional six-switch boost PFC rectifier. As a result, smaller inductors with less magnetic energy storage are possible, resulting in a higher power-to-volume ratio for the electrical three-phase AC-DC converter 100 provided by the present invention.

[0064] For converter 200 including switching device 23, at start-up, switching device 23 is opened to interrupt conduction between the upper node of bridge rectifier 24 and upper intermediate node x. Current flows through inductor L xHere, the phase selector 25 selects at the intermediate node z the (instantaneous) output voltage V across the output terminals P, N for a finite amount of time (e.g., 1 μs). PN By doing so, the voltage at the intermediate node z and the output voltage V are equal for a limited amount of time. DC The positive voltage difference between the inductor L z is applied to the switch S between the switch node t and the terminal P. Pz (Internal) anti-parallel diode D connected to zP When the inductor L z and then to the upper output terminal P. Therefore, the current path is from the intermediate node z through the switch node t and the anti-parallel diode D zP through the capacitor C of the output filter 15. Pm , C mN , back to the lower intermediate node y, and back to the grid phase through one of the lower corresponding diodes of the bridge rectifier 24. By doing so, the output voltage V PN can be gradually increased.

[0065] Democratic control of electrical converters. In accordance with the present invention, the controller 40 controls the desired and / or measured output voltage V DC is the instantaneous full-wave rectified AC line voltage, i.e., max{v a ,v b ,v c}-min{v a ,v b ,v c In the second mode of operation, the upper boost bridge leg 19 and the lower boost bridge leg 20 are not operated and the switch S xm , S my is open (not conducting). In this case, diode D xP , D Nyis conducting and connects the intermediate nodes r, s to the output terminals P, N. As in the converter 200 of FIG. xP , D Ny is the active switch S Px , S yN , then of course these are advantageously set in a closed / conducting state to improve efficiency.

[0066] In the second operating mode, the first converter stage 11 and the current injection circuit 14 operate in the same way as during normal operation.

[0067] By doing so, a reduced voltage is obtained at the output terminals P, N, which in steady state is equal to the rectified mains voltage, as shown in section II of Figure 10B. Section I refers to normal operation, referred to as Mode I operation, in which the upper and lower boost bridge legs are operated to provide a higher output voltage, and thus the electrical converter 100 operates as a normal boost converter.

[0068] Section III of FIG. 10B refers to a transition mode that may be advantageously applied to transition between operating mode I and operating mode II and / or to obtain an average output voltage intermediate between the average output voltage of mode 1 and the average output voltage of mode II.

[0069] The transition mode is the transition between the desired and / or measured output voltage V as indicated by the "BoostOn" signal in FIG. 10B, where a high value indicates that the boost bridge legs 19, 20 are activated and a low value indicates that the circuits 19, 20 are not activated. DC The upper and lower boost bridge legs (switch S xm , S my ) to obtain the

[0070] In Mode II operation, a pulsating output voltage is obtained, e.g., 150 Hz pulsation for a 50 Hz mains frequency, which can be easily absorbed by an additional DC / DC converter stage connected to the output terminals P, N, in particular a galvanically isolated DC / DC converter stage 26 as shown in FIG. 11 , which is typically provided in a (vehicle) battery charging system. The converter stage 26 is connected in series between the DC terminals P, N and the load 22. An important advantage of Mode II operation is that the (isolated) DC / DC converter stage 26 can operate at a reduced voltage ratio when a lower output voltage is required (e.g., when the battery is empty). This reduces stress on the (isolated) DC / DC converter stage, allowing it to be smaller and more efficient.

[0071] Advantageously, the additional DC / DC converter stage 26 is operated in a constant power mode during Mode II operation, and possibly during Mode I operation and / or transition Mode III. When the converter stage 26 is operated in a constant power mode, the relationship between the power P, the current I, and the voltage v, i.e., i * With v=P, the current i obtained at DC terminals P and N DC is shown in FIG. 11B, i.e., i DC * V DC = constant. In constant power mode operation of the DC / DC converter stage 26, a sinusoidal current can be obtained on the AC mains side 21, making it possible to obtain a power factor of unity. In this case, during mode II operation, the current injection circuit 14 is advantageously operated.

[0072] During Mode II operation, switching device 23 (see FIG. 5), if present, is kept closed (conducting) to apply the phase input with the highest voltage by bridge rectifier 24 to upper intermediate node x.

[0073] Yet another exemplary embodiment of an electrical converter 500 is depicted in Figure 12. Electrical converter 500 differs from converters 100, 200, 300, and 400 in that it lacks phase selector 25 and current injection circuit 14. Instead, third harmonic current injection is provided directly via switches in bridge legs 16, 17, and 18, which are provided as active bridge legs allowing bidirectional operation.

[0074] Alternative Converter Topologies The electrical converter 500, called a Belgian rectifier, comprises a first converter stage in the form of a three-phase active rectifier stage 11 and a DC / DC stage 12. The electrical converter 500 further comprises an input filter 13 and an output filter 15.

[0075] The electrical converter 500 is an AC-DC converter having three phase inputs a, b, c that are connected to the three-phase voltage of a three-phase AC grid 21, two DC outputs P, N that may be connected to a DC load 22, such as a high-voltage (e.g., 800 V) battery of an electric vehicle, and a terminal n for connecting the neutral conductor of the AC grid 21.

[0076] The two converter stages 11, 12 can be considered as one "integrated" converter stage, since no high frequency filter capacitors are present between the two power stages and both stages use a common energy storage inductor (boost inductor). In particular, the phase inductor L of the input filter 13 a , L b , L c is used as a boost inductor and is shared between both converter stages 11, 12.

[0077] The rectifier stage 11 is connected to the phase inductor L of the input filter 13. a , L b , L c Three phase inputs connected to three phase inputs A, B, C via

[0078]

number

[0079] ,

[0080]

number

[0081] ,

[0082]

number

[0083] and two outputs

[0084]

number

[0085] ,

[0086]

number

[0087] These outputs are connected to the upper intermediate voltage node 11, which indicates the "switched" potential caused by the switching of the DC / DC stage 12.

[0088]

number

[0089] and lower mid-voltage nodes

[0090]

number

[0091] It can be seen as.

[0092] The rectifier stage 11 is comprised of three bridge legs 16, 17, 18, each of which has two actively switchable semiconductor devices with respect to leg 16 connected in a half-bridge configuration.

[0093]

number

[0094] and

[0095]

number

[0096] and Leg 17

[0097]

number

[0098] and

[0099]

number

[0100] and Leg 18

[0101]

number

[0102] and

[0103]

number

[0104] Each switchable semiconductor device has an anti-parallel diode. In this example, metal oxide field effect transistors (MOSFETs) are used for the actively switchable semiconductor devices, each of which includes an internal anti-parallel body diode that can replace the external anti-parallel diode.

[0105] The output power stage consists of two stacked boost bridges 19, 20. Each boost bridge has boost switches (with respect to the upper boost bridge 19) connected in a half-bridge configuration.

[0106]

number

[0107] and the lower boost bridge 20

[0108]

number

[0109] ) and boost diode (for the upper boost bridge 19

[0110]

number

[0111] and the lower boost bridge 20

[0112]

number

[0113] The middle node of the upper boost bridge 19 is an intermediate voltage node

[0114]

number

[0115] , and the middle node of the lower boost bridge 20 is connected to the intermediate voltage node

[0116]

number

[0117] The common node m of both boost stages is connected to the midpoint of the output filter 15, which has two output filter capacitors C connected in series between the upper output node p and the lower output node n. Pm , C mN Equipped with.

[0118] The upper boost bridge 19 is connected between the upper output node p and the middle output node m (i.e., via an upper output filter capacitor C Pm (in parallel with) and the intermediate voltage node

[0119]

number

[0120] But the switch

[0121]

number

[0122] and the switch is arranged so that it can be alternately connected to the middle output node m and the upper output node P by controlling

[0123]

number

[0124] When is open (not conducting), the diode

[0125]

number

[0126] via the intermediate voltage node

[0127]

number

[0128] Current can flow from the switch to the upper output node P.

[0129]

number

[0130] When is closed (conducting), the switch

[0131]

number

[0132] via the intermediate voltage node

[0133]

number

[0134] Current can flow from node m to the intermediate output node m (or vice versa).

[0135] The lower boost bridge 20 is connected between the middle output node m and the lower output node N (i.e., the lower output filter capacitor C mN (in parallel with) and the intermediate voltage node

[0136]

number

[0137] But the switch

[0138]

number

[0139] and the switch is arranged so that the node m can be alternately connected to the middle output node m and the lower output node N by controlling the switch

[0140]

number

[0141] When is open (not conducting), the diode

[0142]

number

[0143] From the lower output node N to the intermediate voltage node

[0144]

number

[0145] current can flow through the switch

[0146]

number

[0147] When is closed (conducting), the switch

[0148]

number

[0149] From the intermediate output node m to the intermediate voltage node

[0150]

number

[0151] Current can flow through it (and vice versa).

[0152] Boost switch of the boost bridge (

[0153]

number

[0154] ,

[0155]

number

[0156] ) is an actively switchable semiconductor device. In the example of Figure 12, a MOSFET is used.

[0157] Three AC capacitors C that are part of the input filter 13 a , C b , C c interconnects the phase inputs a, b, and c in a star-connected configuration. In general, three capacitors C a , C b , C c Advantageously, the s and t have substantially equal values ​​in order to load the AC grid symmetrically.

[0158] If available, the neutral conductor of the three-phase AC grid may be connected to the neutral connection terminal n of the converter 500. This neutral connection terminal N is connected to the AC capacitor C a , C b , C c and to the common node m of the stacked boost bridges 19, 20 (and therefore also to the midpoint of the output filter 15). This results in a fully symmetrical converter structure.

[0159] The bridge leg of the rectifier stage 11 connected to the phase input A, B, or C having the highest voltage of the three-phase AC input voltage is connected such that the corresponding phase input A, B, or C is coupled to the corresponding phase inductor (L a , L b , or L c ) through the upper mid-voltage node

[0160]

number

[0161] As a result, the AC capacitor (C a , C b , or C c ) and the phase inductor of the phase with the highest voltage (L a , L b , or L c ), the upper boost bridge 19, and the upper output capacitor C Pm A conventional DC / DC boost converter (upper boost converter) is formed by the voltage v of the phase input A, B, or C with the highest voltage level. a , v b , or v c The output voltage of this upper boost converter is Pm Voltage V across Pm and has a voltage value substantially equal to half the total DC bus voltage (V Pm ≒V DC The upper boost converter is formed by connecting the phase inductor (L a , L b , or L c ) at a specific, possibly variable, switching frequency f s Switch in

[0162]

number

[0163] It can be operated by PWM modulation.

[0164] The bridge leg of the rectifier stage 11 connected to the phase input A, B, or C having the lowest voltage of the three-phase AC input voltage is connected such that the corresponding phase input A, B, or C is coupled to the corresponding phase inductor (L a , L b , or L c ) through the lower intermediate voltage node

[0165]

number

[0166] To achieve this, the bridge legs are switched to be connected to the corresponding phase inputs

[0167]

number

[0168] ,

[0169]

number

[0170] ,or

[0171]

number

[0172] the node

[0173]

number

[0174] As a result, the AC capacitor (C a , C b , or C c) and the phase inductor of the phase with the lowest voltage (L a , L b , or L c ), a lower boost bridge 20, and a lower output capacitor C mN This forms a conventional "inverting" (negative input voltage and negative output voltage) DC / DC boost converter (lower boost converter). The input voltage of this lower boost converter is the voltage v of the phase input A, B, or C with the lowest voltage level. a , v b , or v c and the output voltage of this lower boost converter is mN Voltage V across Nm and has a voltage value substantially equal to minus one-half of the total DC bus voltage (V Nm ≒-V DC The lower boost converter is formed by connecting the phase inductor (L a , L b , or L c ) at a specific, possibly variable, switching frequency f s Switch in

[0175]

number

[0176] It can be operated by PWM modulation.

[0177] The bridge legs of the rectifier stage 11 connected to a phase input A, B, or C having a voltage between the highest and lowest voltages of the three-phase AC input voltage are connected such that the corresponding phase input A, B, or C is coupled to a corresponding phase inductor (L a , L b , or L c ) through the upper mid-voltage node

[0178]

number

[0179] and the lower mid-voltage node

[0180]

number

[0181] To achieve this, the bridge legs are switched so that they are alternately connected to the corresponding phase inputs.

[0182]

number

[0183] ,

[0184]

number

[0185] ,or

[0186]

number

[0187] the node

[0188]

number

[0189] and

[0190]

number

[0191] The bridge legs of the rectifier stage 11 connected to the phase inputs A, B, or C having voltages between the highest and lowest voltages of the three-phase AC input voltage may be switched in a manner similar to a single-phase half-bridge voltage source converter (VSC), with the phase inductors (L) of the phases having voltages between the highest and lowest voltages of the three-phase AC input voltage being switched.a , L b , or L c ) at a specific, possibly variable, switching frequency f s The inverter is operated by PWM modulation of the switches in the bridge legs.

[0192] In summary, two of the three bridge legs of the rectifier stage 11 are in the "selected state" and which AC capacitor (C a , C b , or C c ) and phase inductor (L a , L b , or L c ) is connected to the upper boost bridge 19 and the upper output capacitor C Pm and the phase inductor (L a , L b , or L c ) and which AC capacitor (C a , C b , or C c ) and phase inductor (L a , L b , or L c ) is connected to the lower boost bridge 20 and the lower output capacitor C mN and the phase inductor (L a , L b , or L c ) is part of the lower step-up converter used to control the current in the rectifier stage 11. The remaining bridge legs of the rectifier stage 11 are in an "active switching state" and can be operated in a manner similar to a single-phase half-bridge voltage source converter (VSC). It selects the remaining phase inductor (L) of phase input a, b, or c that has a voltage between the highest and lowest voltages of the three-phase AC input voltage. a , L b , or L c ) and the remaining phase capacitors (C a , C b , or Cc ) and the remaining switching circuit, which consists of two output capacitors C Pm , C mN and a phase inductor (L a , L b , or L c ) is used to control the current in

[0193] The controller 40 is configured to operate a bridge leg to which an AC phase input having a minimum instantaneous absolute voltage (a voltage between the highest and lowest voltages of the three-phase AC input voltages) is applied by pulse width modulation to alternately connect this phase to the upper intermediate node x and the lower intermediate node y.

[0194] Similar to converter 100, controller 40 of electrical converter 500 may implement the above-described Mode II operation. In Mode II operation, boost bridge legs 19, 20 are not operated and the first converter stage operates normally. Referring to FIG. 12B, Mode II operation makes it possible to obtain a reduced voltage similar to that obtainable for converter 100. Alternative suitable converter topologies capable of implementing the operation modes described herein are described in WO2020 / 035527.

[0195] 14 , the battery charging system 700 includes a power supply unit 704. The power supply unit 704 is coupled to an AC grid via terminals A, B, and C on the one hand, and is coupled to an interface 702 (at terminals P′, N′) on the other hand, which includes a switch device that allows the power supply unit 704 to be connected to, for example, a battery 703. The power supply unit 704 includes any one of the above-described electrical converters 100 having first and second converter stages and a third converter stage 701, which in this system is a DC-DC converter. The power supply unit 704 may further include a pair of coils inductively coupled through air (not shown), such as in the case of wireless power transmission. In some cases, the interface 702 may include a plug and socket, for example, in wired power transmission. Alternatively, a plug and socket may be provided at the input (e.g., nodes A, B, and C). [Explanation of symbols]

[0196] 11 Three-phase active phase selector, converter stage, first converter stage, input stage, first converter circuit, three-phase active rectifier stage, rectifier stage 12 Converter stage, second converter stage, DC / DC stage, output power stage 13 Input Filter 14 Buck-boost bridge leg, middle buck-boost bridge leg, current injection circuit 15 Output Filter 16 Leg, Bridge Leg 17 Leg, Bridge Leg 18 Leg, Bridge Leg 19 Boost bridge leg, upper boost bridge leg, PWM modulation upper boost bridge leg, boost bridge, upper boost bridge, boost circuit, circuit 20 Boost bridge leg, lower boost bridge leg, PWM modulation lower boost bridge leg, boost bridge, lower boost bridge, boost circuit, circuit 21 3 Phase AC Grid, Electrical AC Grid, AC Mains Side, AC Grid 22 DC load, load 23 Switching Devices, Devices 24 Three-phase bridge rectifier, bridge converter, bridge rectifier, rectifier 25 Phase Selector 26 DC / DC converter stage, converter stage 40 Central control unit, controller, control unit 41 input ports 42 Measurement value input port 43 Measurement value input port 44 Measurement input port 45 Measurement value input port 50 Communication Interface 51 Switch signal generator 52 Switch signal generator 53 Switch Signal Generator 54 PWM generation elements 60 Outer voltage control loop 61 Comparator 62 Control Elements 63 Multiplier 64 Computational elements 65 Comparator 66 Control Elements 67 Additive Elements 70 Inner current control loop, current controller, current control loop 71 Individual Current Controller, Controller, Current Controller 72 Comparator 73 Control Elements 74 Individual Current Controller, Controller, Current Controller 77 Individual Current Controller, Controller, Current Controller 81 Selection elements, selector elements 93 Measurement Processing Unit 94 Measurement Processing Unit 95 Measurement Processing Unit 96 Measurement value processing unit 100 Electrical converter, electrical three-phase AC-DC converter, converter 200 Electrical converters, converters 300 Electrical converters, converters 400 Electrical converters, converters 500 Electrical converters, converters 700 Battery Charging System 701 Converter Stage 702 Interface 703 Battery 704 Power Supply Unit

Claims

1. An electrical converter (100, 200, 300, 400, 500) for converting an AC signal having three phase voltages into a DC signal, Three phase terminals (A, B, C), a first DC terminal (P) and a second DC terminal (N), a first converter stage (11) operably coupled to the three phase terminals and comprising a first intermediate node (x) and a second intermediate node (y), the first converter stage (11) being configured to convert between the AC signals at at least the three phase terminals and a first signal at the first intermediate node (x) and the second intermediate node (y); a second converter stage (12) operatively coupled to the first and second DC terminals (P, N) and comprising a third intermediate node (r) and a fourth intermediate node (s), the second converter stage comprising a boost circuit (19, 20) operable to convert between a second signal at the third and fourth intermediate nodes (r, s) and the DC signal at the first and second DC terminals (P, N), the boost circuit comprising at least one first active switch (S xm , S my a second converter stage (12) comprising: a link connecting the first intermediate node (x) to the third intermediate node (r) and the second intermediate node (y) to the fourth intermediate node (s); a current injection circuit operable to connect, via a second active switch, the phase terminal having the smallest instantaneous absolute voltage value among the at least three phase terminals and the first and second DC terminals (P, N) or between the phase terminal having the smallest instantaneous absolute voltage value and the first and second intermediate nodes; The at least one first active switch (S xm , S my ) and a controller (40) implementing a first operating mode in which the second active switch is operated by pulse width modulation; Equipped with the electrical converter further comprises a third converter stage operatively coupled to the first and second DC terminals (P, N) and operable to convert the DC signals at the first and second DC terminals into fourth signals at at least two third terminals (P', N'); the controller (40) is configured to implement a second operating mode in which the third and fourth intermediate nodes (r, s) are continuously connected to the first and second DC terminals (P, N), respectively, and the second converter stage (12) is inactive, the second active switch is operated by pulse width modulation, and the third converter stage is operated in a constant power mode. An electrical converter (100, 200, 300, 400, 500), 1. An electric converter, wherein the controller comprises a first input for receiving a third signal representative of a set or measured voltage at the first and second DC terminals, the controller being configured to determine a threshold representative of an instantaneous full-wave rectified voltage value of the AC signal, and to operate in the second operating mode based on a comparison between the third signal and the threshold.

2. The electrical converter of claim 1 , wherein the controller is configured to operate in the second operating mode when the third signal is less than or equal to the threshold value.

3. 3. The electric converter according to claim 1, wherein the controller is configured to transition between the first and second operation modes by intermittent operation of the boost circuit (19, 20).

4. 4. An electric converter according to any one of claims 1 to 3, wherein the third converter stage comprises at least one DC / DC converter (26) or a DC / AC converter.

5. 5. The electrical converter of claim 4, wherein the third converter stage comprises a galvanically isolated DC / DC converter (26).

6. The boost circuit comprises a first boost circuit (19) and a second boost circuit (20) stacked between the first DC terminal (P) and the second DC terminal (N), the first and second boost circuits comprising a common node (m), and each of the first and second boost circuits being connected to the first active switch (S xm , S my 6. The electrical converter according to claim 1, comprising at least one of:

7. The current injection circuit includes a third active switch (S) configured to selectively connect the three phase terminals to a fifth intermediate node (z). aza , S bzb , S czc ) and the second active switch (S Pz , S zN 7. The electric converter (100, 200, 300, 400) of claim 1, wherein a third active switch (300) is operable to connect the fifth intermediate node (z) to the first DC terminal (P) and the second DC terminal (N), and the controller (40) is configured to control switching of the third active switch according to a switching pattern in which the phase terminal having the smallest instantaneous absolute voltage value of the three phase voltages is continuously connected to the fifth intermediate node (z).

8. In the second operating mode, the controller (40) controls the second active switch (S) by pulse width modulation. Pz , S zN 8. The electrical converter of claim 7, configured to operate a

9. 7. The electric converter (500) of claim 1, wherein the first converter stage comprises a bridge converter having three active bridge legs for converting between the AC signal at the three phase terminals and the first signal at the first intermediate node (x) and the second intermediate node (y), and the controller (40) is configured to operate, by pulse width modulation, one of the three active bridge legs corresponding to the phase voltage of the AC signal having the smallest instantaneous absolute voltage value to function as the second active switch of the current injection circuit.

10. 10. The electric converter of claim 9, wherein the bridge converter is configured such that the phase terminal corresponding to the phase of the AC signal having the highest instantaneous voltage value is continuously connected to the first intermediate node, and the phase terminal corresponding to the phase of the AC signal having the lowest instantaneous voltage value is continuously connected to the second intermediate node.

11. A battery charging system comprising a power source, the power source comprising an electrical converter according to any one of claims 1 to 10.

12. 11. An electric motor drive system comprising a power supply, the power supply comprising an electric converter according to any one of claims 1 to 10.

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