Method and device for synchronizing output AC voltage of converter device with input AC voltage of converter device

Abstract

The invention relates to a method for synchronizing an output AC voltage of a converter arrangement (100) with an input AC voltage of the converter arrangement (100), comprising: generating an output AC voltage, an output AC voltage angular position being preset according to a target output frequency (301); presetting an output AC voltage amplitude; and generating the output AC voltage as a function of the output AC voltage angular position (301) and the output AC voltage amplitude; presetting a first frequency as a target output frequency and generating the output AC voltage; determining a frequency of the input AC voltage (201) as a second frequency; and changing the target output frequency from the first frequency to the second frequency, wherein a quadrature signal (211, 212) is determined from the input alternating voltage (201); determining a q component (307) of the quadrature signal (211, 212) by means of a d / q transformation from the output AC voltage angular position (301); and minimizing the q-component (307) by using a regulator (401) having an integration part (402), in which an output AC voltage frequency is determined as a regulator output quantity (403), in which the integration part (402) is initialized with the first frequency (404).

Description

Technical Field

[0001] The present invention relates to a method for synchronizing the output AC voltage of a converter device with the input AC voltage of the converter device, as well as a computing unit and a computer program for performing the method. Background Technology

[0002] To synchronize alternating currents with different frequencies, such as when using an inverter, a so-called SOGI-based PLL structure can be used (SOGI stands for Second-order Generalized Integrators; PLL stands for phase-locked loop).

[0003] The SOGI structure is essentially a notch filter (bandpass) that can be easily tuned to the input frequency. Furthermore, an advantage of the SOGI structure is that it can simultaneously access the filtered output and its quadrature-shifted version (α-axis and β-axis). Therefore, the SOGI structure can be easily implemented, matching the implementation of a traditional dq-type PLL (using the Park transform as a phase detector). Summary of the Invention

[0004] According to the present invention, a method for synchronizing the output AC voltage of a converter device with the input AC voltage of the converter device, having the features of the independent claim, is provided, along with a computing unit and a computer program for performing the method. Advantageous designs are those described in the dependent claims and hereinafter.

[0005] This invention enables the output AC voltage of a converter device to be synchronized seamlessly with the input AC voltage, which has a different frequency than the converter device, without frequency jumps. This protects the connected load from interference, overvoltage, etc., and can help extend its service life.

[0006] In particular, mobile converters, such as integrated charging devices (on-board chargers or OBCs) in rechargeable vehicles, should be able to operate under many different grid configurations. Thus, for example, an OBC can be connected at 50Hz in a single-phase, two-phase, or three-phase configuration in the Central European grid, while 60Hz is common in the United States, and 50Hz and 60Hz are common in Japan. On the other hand, such OBCs can also supply AC loads at a specific frequency, which may deviate from the frequency of the input voltage, and should be synchronized as uninterruptedly as possible—this is precisely what this invention addresses.

[0007] To this end, the present invention, in an advantageous design, utilizes an extension of the PLL structure using a second-order generalized integrator (SOGI). To avoid discontinuities in frequency and angle, frequency and angular position are used when minimizing the q-component. At least one integrator is used for the angular position value during minimization, preferably two integrators for both the angular position value and the frequency. The integration part starts with either the current frequency or angular position value and then gradually or continuously transitions to the new target value. Minimization can have purely integral behavior, i.e., implemented as an I-regulation element, or it can also have additional proportional behavior, i.e., implemented as a PI-regulation element. This advantageously results in synchronization not occurring abruptly, but rather gradually reaching the target state through the presence of at least one integrator.

[0008] The computing unit according to the invention, such as the control device for a converter or inverter, is configured, in particular, using programming techniques, to execute the method according to the invention.

[0009] It is also advantageous to implement the method according to the invention in the form of a computer program or a computer program product having program code for performing all method steps, as this results in particularly low cost, especially when the control device performing the action is also used for other tasks and therefore exists anyway. Finally, a machine-readable storage medium is provided on which the computer program as described above is stored. Suitable storage media or data carriers for providing the computer program are, in particular, magnetic, optical, and electrical memories, such as hard disks, flash memory, EEPROM, DVDs, etc. The program can also be downloaded via a computer network (Internet, intranet, etc.). Such downloading can be performed via wired or wireless means (e.g., via WLAN networks, 3G connections, 4G connections, 5G connections, or 6G connections, etc.).

[0010] Other advantages and design solutions of the present invention will become apparent from the specification and drawings. Attached Figure Description

[0011] The present invention is illustrated schematically with reference to the accompanying drawings, and is described below with reference to the drawings.

[0012] Figure 1 The converter device on which the present invention is based is illustrated in a schematic block diagram.

[0013] Figure 2 A schematic block diagram illustrates one aspect of the method, which involves determining an orthogonal signal from an input AC voltage.

[0014] Figure 3 A sub-aspect of the method is illustrated in a schematic block diagram, which involves determining the q-component of an orthogonal signal using a d / q transform.

[0015] Figure 4A sub-aspect of the method is illustrated in a schematic block diagram, which involves minimizing the q-component using a regulator with an integral part.

[0016] Figure 5 The switching between different operating modes of the converter device is illustrated in a schematic block diagram. Detailed Implementation

[0017] exist Figure 1 In this schematic block diagram, the converter device on which the present invention is based is shown and generally designated as 100. In one design, the converter device 100 can be configured as an internal charging device for an electric or hybrid vehicle, i.e., a so-called on-board charger, and is configured to convert an input AC voltage to an output DC voltage to charge an energy storage device in the vehicle. In an improved embodiment shown, the converter device 100 can also be configured to receive DC voltage from the energy storage device and convert it to an output AC voltage to power one or more AC loads 30, which can be connected, for example, to corresponding outlets on the converter device 100.

[0018] The converter device 100 here has a first converter 110, which has a first AC voltage terminal 120 for applying an input AC voltage and a first DC voltage terminal 130, wherein the first DC voltage terminal 130 is connected to a DC intermediate circuit 140. In particular, capacitors for voltage smoothing and energy storage can be arranged in the DC intermediate circuit.

[0019] The input AC voltage can come from the power grid 10, and can be, for example, 230V household AC voltage.

[0020] The converter device 100 also includes a DC voltage converter 150 having a second DC voltage terminal 160 and a third DC voltage terminal 170 for applying an output DC voltage, wherein the second DC voltage terminal 160 is also connected to the DC intermediate circuit 140. The third DC voltage terminal 170 can be connected to a DC power grid 20, such as the so-called high-voltage grid of an electric vehicle having a high-voltage energy storage device, which can be charged via the output DC voltage from the converter device 100.

[0021] The converter device 100 also has a second converter 180, which has a second AC voltage terminal 190 for outputting an AC voltage and a fourth DC voltage terminal 195, wherein the fourth DC voltage terminal 195 is connected to a DC intermediate circuit 140.

[0022] Since the DC intermediate circuit 140 serves as both the load (Senke) of the first converter 110 and the power source (Quelle) of the second converter 180 in the aforementioned operating mode, the voltage level in the DC intermediate circuit 140 depends on the behavior of both converters. The design and lifespan of the capacitors in the DC intermediate circuit 140 (intermediate circuit capacitors) critically depend on how the voltage and current ripples are designed. If the phase characteristics of the two converters are not synchronized, an additional frequency component is generated in the intermediate circuit voltage, caused by the superposition of the two frequencies. Therefore, it is essential that the phase characteristics of the input AC voltage and the output AC voltage be synchronized for the design and lifespan of the capacitors.

[0023] In countries with varying grid frequencies (such as Japan), synchronization is impossible if the current external grid frequency does not match the frequency required by the load (e.g., a 50 Hz grid with a 60 Hz load). However, in most countries, the grid frequency is fixed (e.g., 50 Hz in Europe or 60 Hz in North America).

[0024] When the charging process begins, the grid frequency is determinable, especially by using, for example, a PLL method. If load 30 is subsequently connected in time, preset values ​​of frequency and phase can be switched to the frequency and phase of the identified grid 10 using the second converter 180. Therefore, synchronization can be achieved relatively easily. Alternatively, load 30 is powered first, and the preset values ​​of frequency and phase therefore do not correspond to the preset values ​​of grid 10, since the preset values ​​of grid 10 are unknown when power is initially supplied to load 30. In this case, the energy used to power load 30 initially comes from the DC grid 20, i.e., through the reverse-running DC-DC converter 150.

[0025] To power load 30, an output AC voltage is generated at the second AC voltage terminal 190 via converter device 100. For this purpose, the output AC voltage angle position θ is preset according to the target output frequency f = ω / 2π. Specifically, θ ranges from 0 to 360° or 2π. The output AC voltage angle position θ can be calculated based on the target output frequency. In this case, a clock or clock generator can be used. Furthermore, the output AC voltage amplitude u is preset. Inv .

[0026] The second converter 180 is controlled such that it adjusts according to the output AC voltage angle position θ and the output AC voltage amplitude u. Inv Especially according to u InvGen =u Inv*sin(θ) generates the output AC voltage u from the DC voltage (intermediate circuit voltage) applied to the fourth DC voltage terminal 195. InvGen .

[0027] The following description, with reference to the accompanying drawings, describes the method for converting the output AC voltage u of the converter device 100. InvGen One embodiment of the method for synchronizing with the input AC voltage does not require shutting off the load 30. Synchronization reduces intermediate circuit voltage ripple, allowing for more economical design of intermediate circuit capacitors and extending their lifespan.

[0028] This implementation appropriately includes determining the frequency of the input AC voltage as a second frequency, and in further design options, includes determining the gradient of the input AC voltage frequency, and determining the second frequency when the gradient is below a gradient threshold. The gradient threshold can be preset and / or presettable, for example, preset by parameterization of the converter device or the computational unit controlling the converter device. In particular, synchronization should only be performed when the frequency of the input AC voltage is stable. This can be achieved, for example, by a PDT1 module that models the gradient.

[0029] In the converter device 100, the frequency of the input AC voltage can be determined using a PLL algorithm. Once the PLL algorithm is in its "locked" phase, specific criteria can be calculated and evaluated to identify whether the input AC voltage is valid or applicable. For example, preconditions can be set such that, in addition to the frequency, the effective voltage or amplitude value is also within a specific range.

[0030] Figure 2 A schematic block diagram illustrates one aspect of the method, which involves determining an orthogonal signal from an input AC voltage, using a second-order generalized integrator (SOGI). The input AC voltage u is used in 201 as the input quantity. grid In step 202, an optional desired gain factor k is used, and in step 203, a second frequency ω2 is used. As the output quantity, a value with two components u is obtained. α (in 211) and u β Orthogonal signals (at 212). More details on this can be found in, for example, Rafal, Krzysztof & , Kamil & Bobrowska-Rafal, Malgorzata. (2014), Application of the second order generalized integrator in digital control systems (Archives of Electrical Engineering 63. 2014. 10.2478 / aee-2014-0031). Here, output u α Synchronized with the input AC voltage, i.e., the angular position and frequency coincide. The implementation shown only includes subtractors 204 and 206, multipliers 205, 208 and 210, and integrators 207 and 209, and is therefore easy to implement.

[0031] Figure 3 A schematic block diagram illustrates one aspect of the method, which involves determining the q-component of the quadrature signal using a d / q transform (specifically, a Park transform) based on the angular position of the output AC voltage. As input quantities, two components u are provided at 211 and 212. α and u β The orthogonal signals at 301 provide their respective current output AC voltage angular positions θ. The q component Q is obtained as the output quantity at 307. In particular, a transformation is used here where the Q-axis is positioned on the α-axis. The implementation shown only includes trigonometric functions 302 and 303, multipliers 304 and 305, and adder 306, and is therefore easy to implement.

[0032] Figure 4 A schematic block diagram illustrates one aspect of the method, which involves minimizing the q-component using a regulator 401 with an integral portion 402 (1 / s), wherein the frequency of the output AC voltage is determined as the regulator output quantity 403. Here, the integral portion 402 is initialized with a first frequency 404. Minimizing the q-component may, in particular, include minimizing the q-component to zero or causing it to be zero. A trigger signal may be supplied at the input, which is determined, for example, based on the stability or gradient of the second frequency as described above. This trigger signal resets the integrators 402 and 405.

[0033] Here, regulator 401 includes a proportional portion 406 in addition to the integral portion 402, where the two portions are added at 407 to determine the output AC voltage frequency 403, which is then fed to a so-called anti-integral saturation module 408. In this anti-integral saturation module, the output AC voltage frequency 403 (wUnlim) is limited to a value between a minimum value 409 (wMin) and a maximum value 410 (wMax), and is output as a restricted output AC voltage frequency (wLimd) at 411. In other words, if the (unrestricted) output AC voltage frequency 403 exceeds the maximum value, the restricted output AC voltage frequency is set to the maximum value 410; and / or if the (unrestricted) output AC voltage frequency 403 is below the minimum value, the restricted output AC voltage frequency is set to the minimum value 409. If the limitation of the regulator output is effective, zero is output at output terminal 412 (flgClamp). If the limitation of the regulator output is not effective, one is output at output terminal 412. The output can be delayed by one calculation step.

[0034] Furthermore, it is stipulated that when the limit on the regulator output is in effect, the integral portion 402 of the regulator 401 is not changed. Therefore, the output 412 (zero or one) is multiplied by the q-component 307 at 413 in the regulator 401. An optional gain 414 may also be provided in the regulator 401.

[0035] In the illustrated embodiment, the output AC voltage angle position 301 is also determined from the—possibly limited—regulator output 411 or the determined output AC voltage frequency using another integrator 405, wherein the output value of the integrator 405 is initialized with the output AC voltage angle position 415 at the start of the change step. By integrating or quasi-continuously summing the—possibly limited—regulator outputs 403, 411 or the determined output AC voltage frequency (which gradually approaches a second frequency), the output AC voltage angle position 301 (i.e., the angle position of the output AC voltage being established) is gradually and continuously adjusted to the angle position of the input AC voltage 201.

[0036] The described method can be particularly as follows Figure 5 The diagram shows how to switch between different operating modes.

[0037] In particular, in block 501, the converter device 100 can operate in a first operating mode, such that the DC voltage converter 150 converts the input DC voltage applied to the third DC voltage terminal 170 into an intermediate circuit voltage applied to the second DC voltage terminal 160, and the second converter 180 converts the intermediate circuit voltage applied to the fourth DC voltage terminal 195 into an output AC voltage with a first frequency applied to the second AC voltage terminal 190.

[0038] In block 503, converter device 100 operates in a second operating mode, such that first converter 110 converts an input AC voltage with a second frequency applied to first AC voltage terminal 120 into an intermediate circuit voltage applied to first DC voltage terminal 130, and second converter 180 converts the intermediate circuit voltage applied to fourth DC voltage terminal 195 into an output AC voltage with a second frequency applied to second AC voltage terminal 190.

[0039] In block 502, by changing the target output frequency from a first frequency to a second frequency as described above, the converter device 100 switches between first and second operating modes. This specifically includes: after identifying a stable input frequency, using the current angular position 415 of the output AC voltage as the initialization value for the integrator 405. Simultaneously, the preset angle value of the output AC voltage, i.e., the output AC voltage angle position 301, is switched to the output terminal of the integrator 405. Therefore, the output AC voltage does not jump in frequency or angle at the instant it switches to another preset angle value.

[0040] If grid synchronization is lost during operation, the system can switch back to the internal angle preset value. In this case, the last known angular frequency is used as the preset frequency, and the angle is set to the last controlled angle. If the grid re-establishes and is identified, the above method applies. Typical applications include supplying AC voltage loads, subsequently initiating a separate charging process for the energy storage device, the completion of that charging process, and recharging.

Claims

1. A method for synchronizing the output AC voltage of a converter device (100) with the input AC voltage of the converter device (100), comprising: - Generate output AC voltage, including: ○ The output AC voltage angle position (301) is preset according to the target output frequency; ○ Preset output AC voltage amplitude; ○ The output AC voltage is generated based on the output AC voltage angle position (301) and the output AC voltage amplitude; - A first frequency is preset as the target output frequency, and the output AC voltage is generated accordingly; - Determine the frequency of the input AC voltage (201) as the second frequency; - Changing the target output frequency from the first frequency to the second frequency includes: ○ Determine the quadrature signals (211, 212) from the input AC voltage (201); ○ The q component (307) of the orthogonal signal (211, 212) is determined by means of d / q transformation based on the angular position (301) of the output AC voltage. ○ The q component (307) is minimized by using a regulator (401) with an integral part (402), wherein the output AC voltage frequency is determined as the regulator output quantity (403), wherein the integral part (402) is initialized with the first frequency (404).

2. The method according to claim 1, wherein the output AC voltage angle position (301) is determined from the determined output AC voltage frequency by using an integrator (405), wherein the output value of the integrator (405) is initialized with the output AC voltage angle position at the start of the change (415) step.

3. The method according to claim 1 or 2, wherein the regulator output (403) is limited to a range of values ​​between a minimum value (409) and a maximum value (410).

4. The method according to claim 3, wherein when the limitation of the regulator output (403) is effective (412), the integral portion (402) of the regulator (401) is not changed.

5. The method according to any one of the preceding claims, wherein the determination of the orthogonal signals (211, 212) is performed by using a second-order generalized integrator.

6. The method according to any one of the preceding claims, wherein determining the frequency of the input AC voltage (201) as a second frequency comprises: - Determine the gradient of the frequency of the input AC voltage, and determine the second frequency when the gradient is below a gradient threshold.

7. The method according to any one of the preceding claims, wherein the converter device (100) comprises: - A first converter (110) having a first AC voltage terminal (120) and a first DC voltage terminal (130) for applying the input AC voltage, wherein the first DC voltage terminal (130) is connected to a DC intermediate circuit (140). - a DC voltage converter (150) having a second DC voltage terminal (160) and a third DC voltage terminal (170), wherein the second DC voltage terminal (160) is connected with the DC intermediate circuit (140), - a second converter (180) having a second AC voltage terminal (190) for outputting the output AC voltage and a fourth DC voltage terminal (195), wherein the fourth DC voltage terminal (195) is connected with the DC intermediate circuit (140), The method comprises the following steps: - operating (501) the converter device (100) in a first operating mode such that -- the DC voltage converter (150) converts an input DC voltage applied on the third DC voltage terminal (170) to an intermediate circuit voltage applied on the second DC voltage terminal (160), and -- the second converter (180) converts the intermediate circuit voltage applied on the fourth DC voltage terminal (195) to an output AC voltage having a first frequency applied on the second AC voltage terminal (190), - operating (503) the converter device (100) in a second operating mode such that -- the first converter (110) converts an input AC voltage having a second frequency applied on the first AC voltage terminal (120) to an intermediate circuit voltage applied on the first DC voltage terminal (130), and -- the second converter (180) converts the intermediate circuit voltage applied on the fourth DC voltage terminal (195) to an output AC voltage having the second frequency applied on the second AC voltage terminal (190), - switching (502) between the first operating mode and the second operating mode by changing the target output frequency from the first frequency to the second frequency.

8. A computing unit configured to perform all method steps of the method according to any one of the preceding claims.

9. A computer program which, when executed on a computing unit, causes the computing unit to perform all method steps of the method according to any one of claims 1 to 7.

10. A machine-readable storage medium having stored thereon the computer program according to claim 9.

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