Method and device for synchronising an output ac voltage of a power converter assembly having an input ac voltage of the power converter assembly

Abstract

The invention relates to a method for synchronising an output AC voltage of a power converter assembly (100) with an input AC voltage of the power converter assembly (100), comprising generating an output AC voltage, wherein an output AC voltage angular position (301) is specified depending on a target output frequency, an output AC voltage amplitude is specified, and the output AC voltage is generated according to the output AC voltage angular position (301) and the output AC voltage amplitude, specifying a first frequency as a target output frequency and generating the output AC voltage, and determining a frequency of the input AC voltage (201) as 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 AC voltage (201), a q-component (307) of the quadrature signal (211, 212) is determined by means of a d / q transformation as a function of the output AC voltage angular position (301), and the q-component (307) is minimised using a controller (401) with an integral component (402), wherein the output AC voltage frequency serves as controller output variable (403), wherein the integral component (402) is initialised with the first frequency (404).

Description

[0001] Description

[0002] title

[0003] Method and device for synchronizing an output AC voltage of a power converter arrangement with an input AC voltage of the power converter arrangement

[0004] The present invention relates to a method for synchronizing an output AC voltage of a power converter arrangement with an input AC voltage of the power converter arrangement as well as a computing unit and a computer program for carrying out the method.

[0005] Background of the invention

[0006] To synchronize alternating currents with different frequencies, e.g. when using inverters, so-called SOGI-based PLL structures can be used (SOGI, English Second-order Generalized Integrators; PLL, English phase-locked loop).

[0007] SOGI structures are essentially notch filters (bandpass) that can be easily tuned to an input frequency. Furthermore, they have the advantage of providing simultaneous access to both the filtered output and a square-shifted version of the same output (α- and β-axes). As such, they allow for a simple implementation, matching that of conventional dg-type PLLs (using the Park transform as the phase detector).

[0008] Disclosure of the Invention According to the invention, a method for synchronizing an AC output voltage of a power converter arrangement with an AC input voltage of the power converter arrangement, as well as a computing unit and a computer program for implementing the method, are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

[0009] The invention enables uninterrupted synchronization of an AC output voltage of the converter assembly with a frequency-differentiated AC input voltage of the converter assembly without frequency jumps. This protects connected loads from interference, overvoltages, etc. and can contribute to an increase in service life.

[0010] In particular, mobile power converters, such as integrated chargers (on-board chargers or OBCs) in electrically chargeable vehicles, should be capable of operating in a wide variety of grid configurations. For example, an OBC in Central European power grids can be connected to a single-, two-, or three-phase supply at 50 Hz, whereas in the USA, 60 Hz is common, and in Japan, both 50 and 60 Hz are common. On the other hand, such OBCs can also supply AC loads with a specific frequency, which may differ from the input voltage frequency and should be synchronized as seamlessly as possible, which is what the present invention achieves.

[0011] For this purpose, the invention advantageously uses an extension of a PLL structure using a generalized second-order integrator (SOGI), wherein the frequency and the angular position are used to minimize the q component in order to avoid frequency and angular discontinuities, wherein at least one integrator for the angular position value, preferably two integrators for the angular position value and frequency, are used in the minimization. The integral component is always assigned the current frequency or angular position value as a starting value and then gradually or continuously transitions to the new setpoint values. The minimization can have purely integrating behavior, i.e. be implemented as an I control element, or additionally have proportional behavior, i.e. be implemented as a PI control element.This advantageously results in the synchronization not occurring abruptly, but gradually reaching the target state due to the presence of at least one integrator.

[0012] A computing unit according to the invention, e.g. a control unit of a power converter or inverter, is configured, in particular in terms of programming, to carry out a method according to the invention.

[0013] The implementation of a method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps is also advantageous, since this entails particularly low costs, in particular if an executing control unit is also used for other tasks and is therefore already present. Finally, a machine-readable storage medium is provided with a computer program stored thereon, as described above. Suitable storage media or data carriers for providing the computer program are, in particular, magnetic, optical, and electrical memories, such as hard disks, flash memories, EEPROMs, DVDs, and others. Downloading a program via computer networks (Internet, intranet, etc.) is also possible. Such a download can be wired or cable-based or wireless (e.g., via a WLAN network, a 3G, 4G, 5G, or 6G connection, etc.).

[0014] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0015] The invention is illustrated schematically in the drawings using exemplary embodiments and is described below with reference to the drawing.

[0016] Short description of the drawings

[0017] Figure 1 shows a schematic block diagram of a power converter arrangement such as may form the basis of the invention. Figure 2 shows a schematic block diagram of a partial aspect of the method relating to determining a quadrature signal from the input AC voltage.

[0018] Figure 3 shows a schematic block view of a partial aspect of the method which concerns determining a q-component of the quadrature signal by means of a d / q transformation.

[0019] Figure 4 shows a schematic block view of a partial aspect of the method which concerns minimizing the q-component using a controller with an integral component.

[0020] Figure 5 shows a schematic block view of a change between different operating modes of a power converter arrangement.

[0021] Embodiment(s) of the invention

[0022] Short description of the drawings

[0023] Figure 1 shows a power converter arrangement, as may form the basis of the invention, in a schematic block diagram and designated overall by 100. In one embodiment, the power converter arrangement 100 can be designed as an internal charger, a so-called on-board charger, of an electric or hybrid vehicle and can be configured to convert an input AC voltage into an output DC voltage for charging an energy storage device in the vehicle. In the embodiment shown, the power converter arrangement 100 can further be configured to receive DC voltage from the energy storage device and convert it into an output AC voltage for supplying one or more AC voltage consumers 30, which can be connected, for example, to corresponding sockets of the power converter arrangement 100.

[0024] The power converter arrangement 100 in the present case comprises a first power converter 110 with a first AC voltage terminal 120 for applying the input AC voltage and with a first DC voltage terminal 130, wherein the first DC voltage terminal 130 is connected to a DC voltage intermediate circuit 140. In particular, a capacitor for voltage smoothing and energy storage can be arranged in the DC voltage intermediate circuit.

[0025] The input AC voltage can come from a power supply network 10 and be, for example, a 230V household AC voltage.

[0026] The power converter assembly 100 further comprises a DC-DC converter 150 with a second DC voltage terminal 160 and a third DC voltage terminal 170 for applying the DC output voltage, wherein the second DC voltage terminal 160 is also connected to the DC intermediate circuit 140. A DC voltage network 20 can be connected to the third DC voltage terminal 170, for example, a so-called high-voltage network of the electric vehicle with a high-voltage energy storage device that can be charged with the DC output voltage via the power converter assembly 100.

[0027] The power converter arrangement 100 further comprises a second power converter 180 with 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 to the DC voltage intermediate circuit 140.

[0028] Because, in the operating mode described above, the DC link 140 is simultaneously the sink of the first power converter 110 and the source of the second power converter 180, the voltage level in the DC link 140 depends on the behavior of both power converters. The design and service life of the capacitor in the DC link 140 (intermediate circuit capacitor) depend crucially on how the voltage and current ripples are designed. If the phase responses of the two power converters are not synchronized, an additional frequency component arises in the intermediate circuit voltage, resulting from the superposition of both frequencies. It is therefore crucial for the design and service life of the capacitor that the phase responses of the input AC voltage and the output AC voltage are synchronized.

[0029] In countries with different possible grid frequencies (such as Japan), synchronization cannot be achieved if the available 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 the majority of countries, the grid frequency is fixed (e.g., 50 Hz in Europe or 60 Hz in North America).

[0030] When the charging process is started, the grid frequency can be determined, in particular by using, for example, a PLL method. If the load 30 is connected later, the specified frequency and phase can be switched to those of the detected grid 10 by means of the second power converter 180. Synchronization can thus be implemented relatively easily. Another case occurs when the load 30 is supplied first and thus the specified frequency and phase will not correspond to those of the grid 10, since these are not known when the load 30 is first supplied. The energy to supply the load 30 initially comes from the DC voltage grid 20 by operating the DC-DC converter 150 in the opposite direction.

[0031] To supply the load 30, the power converter arrangement 100 generates an output AC voltage at the second AC voltage terminal 190. For this purpose, an output AC voltage angle position 0 is specified as a function of a target output frequency f=cü / 2iT. In particular, 0 runs from 0 to 360° or 2TT. The output AC voltage angle position 0 can be calculated based on the target output frequency. A clock or a pulse generator can be used for this purpose. Furthermore, an output AC voltage amplitude uinv is specified. The second power converter 180 is controlled such that it generates the output AC voltage u from the DC voltage (intermediate circuit voltage) present at the fourth DC voltage terminal 195. InvGen generated according to the output AC voltage angle position 0 and the output AC voltage amplitude uinv, in particular according to ui nvGen = u !nv * sin(0).

[0032] In the following, an embodiment of a method for synchronizing the output AC voltage u is described with reference to the figures. InvGen The converter arrangement 100 is described with the input AC voltage at which the load 30 does not need to be switched off. Synchronization reduces the ripple of the intermediate circuit voltage, allowing the intermediate circuit capacitor to be designed more efficiently and increasing its service life.

[0033] The embodiment expediently comprises determining a frequency of the input AC voltage as a second frequency, and in a further embodiment, determining a gradient of the frequency of the input AC voltage and determining the second frequency when the gradient falls below a gradient threshold. The gradient threshold can be predetermined and / or specifiable, e.g., by parameterizing the power converter arrangement or a computing unit controlling it. In particular, synchronization should only take place when the frequency of the input AC voltage is stable. This can be implemented, for example, by a PDT1 module that models the gradient.

[0034] In the power converter arrangement 100, the frequency of the input AC voltage can be determined using a PLL algorithm. As soon as the PLL algorithm is in its "locked" phase, certain criteria can be calculated and evaluated, based on which the input AC voltage is recognized as valid or suitable. For example, it can be assumed that, in addition to the frequency, values ​​of the effective voltage or amplitude also lie within a certain range. Figure 2 shows a schematic block diagram of a partial aspect of the method relating to determining a quadrature signal from the input AC voltage, using a second-order generalized integrator (SOGI). The input variables are the input AC voltage u gr id at 201 , an optionally desired gain factor k at 202 and the second frequency CÜ2 at 203 are used. The output variables are the quadrature signal with two components ua on 211 and u ß to 212. Further details can be found, for example, in Rafal, Krzysztof & Mozdzyhski, 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. The output u a synchronous with the input AC voltage, meaning that both the angular position and the frequency are congruent. The implementation shown comprises only difference formers 204, 206, multipliers 205, 208, 210, and integrators 207, 209 and is therefore easy to implement.

[0035] Figure 3 shows a schematic block diagram of a partial aspect of the method, which concerns determining a q-component of the quadrature signal by means of a d / q transformation, in particular a Park transformation, as a function of the output AC voltage angle position. The quadrature signal with two components u is used as input variables. a on 211 and u ß to 212 and the current output AC voltage angle position 0 to 301. The output variable is the q-component Q at 307. In particular, a transformation is used in which the Q-axis is placed on the a-axis. The implementation shown comprises only trigonometric functions 302, 303, multipliers 304, 305, and a summer 306 and is therefore easy to implement.

[0036] Figure 4 shows a schematic block diagram of a partial aspect of the method relating to minimizing the q-component using a controller 401 with an integral component 402 (1 / s), wherein an output AC voltage frequency is determined as the controller output variable 403. The integral component 402 is initialized with the first frequency 404. Minimizing the q-component can, in particular, include or result in minimizing the q-component to zero. A trigger signal can be supplied to an input, which is determined, for example, as described above, based on the stability or gradient of the second frequency. This trigger signal resets integrators 402, 405.

[0037] In this case, the controller 401 includes, in addition to the integral component 402, a proportional component 406, with both components being summed at 407 to determine the output AC voltage frequency 403, which is subsequently fed to a so-called anti-wind-up block 408. Therein, the output AC voltage frequency 403 (wUnlim) is limited to a value range between a minimum value 409 (wMin) and a maximum value 410 (wMax) and output as a limited output AC voltage frequency at 411 (wLimd). In other words, the limited output AC voltage frequency is set to the maximum value 410 if the (unlimited) output AC voltage frequency 403 exceeds the maximum value, and / or to the minimum value 409 if the (unlimited) output AC voltage frequency 403 falls below the minimum value. If the limiting of the controller output is effective, zero is output at output 412 (flgClamp).If the controller output limit is not effective, one is output at output 412. The output can be delayed by one calculation step.

[0038] Furthermore, it is provided that the integral component 402 of the controller 401 is not changed when the limiting of the controller output is in effect. For this purpose, the output 412 (zero or one) in the controller 401 is multiplied by the q-component 307 at 413. An optional gain 414 can also be provided in the controller 401.

[0039] In the embodiment shown, the output AC voltage angle position 301 is further determined from the - possibly limited - controller output variable 411 or the determined output AC voltage frequency using a further integration element 405, wherein an output value of the integration element 405 is initialized with the output AC voltage angle position 415 at the beginning of the variation step. By integrating or quasi-continuously summing with the - possibly limited - controller output variable 403, 411 or the determined output AC voltage frequency, which gradually approaches the second frequency, the output AC voltage angle position 301 (i.e., the angular position of the resulting output AC voltage) is gradually and continuously adjusted to the angular position of the input AC voltage 201.

[0040] The described method can be used in particular, as shown in Figure 5, to switch between different operating modes.

[0041] In particular, in a block 501, the power converter arrangement 100 can be operated in a first operating mode such that the DC-DC converter 150 converts an 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 power converter 180 converts the intermediate circuit voltage applied to the fourth DC voltage terminal 195 into an output AC voltage applied to the second AC voltage terminal 190 at the first frequency.

[0042] In a block 503, the power converter arrangement 100 is operated in a second operating mode such that the first power converter 110 converts an input AC voltage applied to the first AC voltage terminal 120 at the second frequency into an intermediate circuit voltage applied to the first DC voltage terminal 130, and the second power converter 180 converts the intermediate circuit voltage applied to the fourth DC voltage terminal 195 into an output AC voltage applied to the second AC voltage terminal 190 at the second frequency.

[0043] In a block 502, the power converter arrangement 100 switches between the first and second operating modes by changing the target output frequency from the first frequency to the second frequency, as described above. This includes, in particular, that after a stable input frequency is detected, the current angular position 415 of the AC output voltage is used as the initialization value for the integrator 405. At the same time, the angle specification of the AC output voltage, i.e., the AC output voltage angle position 301, is switched to the output of the integrator 405. This ensures that the AC output voltage does not experience a jump in frequency or angle at the moment of switching to another angle specification.

[0044] If grid synchronization is lost during operation, the system can switch back to the internal angle setting. The last known angular frequency is used as the setpoint frequency, and the angle is set to the last controlled angle. If the grid is reconnected and detected, the procedure described above applies. A typical application is supplying AC loads, then an additional charging process for an energy storage device begins, the charging process ends, and then the charging process resumes.

Claims

Claims 1 . A method for synchronizing an AC output voltage of a power converter arrangement (100) with an AC input voltage of the power converter arrangement (100), comprising: Generating an AC output voltage, comprising: o specifying an AC output voltage angular position (301) as a function of a desired output frequency; o specifying an AC output voltage amplitude; o generating the AC output voltage as a function of the AC output voltage angular position (301) and the AC output voltage amplitude; Specifying a first frequency as the target output frequency and generating the output AC voltage; Determining a frequency of the input AC voltage (201) as a second frequency; Changing the target output frequency from the first frequency to the second frequency, comprising: o determining a quadrature signal (211, 212) from the input AC voltage (201); o determining a q-component (307) of the quadrature signal (211, 212) by means of a d / q transformation as a function of the output AC voltage angular position (301); o minimizing the q-component (307) using a controller (401) with an integral component (402), wherein an output AC voltage frequency is determined as the controller output variable (403), wherein the integral component (402) is initialized with the first frequency (404).

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

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

4. The method according to claim 3, wherein the integral component (402) of the controller (401) is not changed when the limiting of the controller output variable (403) is effective (412).

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

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

7. Method according to one of the preceding claims, wherein the power converter arrangement (100) comprises: - a first power converter (110) having a first AC voltage terminal (120) for applying the input AC voltage and a first DC voltage terminal (130), wherein the first DC voltage terminal (130) is connected to a DC voltage intermediate circuit (140), - a DC-DC 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 to the DC voltage intermediate circuit (140), - a second power converter (180) having a second AC voltage terminal (190) for outputting the AC output voltage and a fourth DC voltage terminal (195), wherein the fourth DC voltage terminal (195) is connected to the DC voltage intermediate circuit (140), the method comprising the steps: - operating (501) the power converter arrangement (100) in a first operating mode such that -- that the DC-DC converter (150) converts an 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 -- that the second converter (180) converts the intermediate circuit voltage applied to the fourth DC voltage terminal (195) into an output AC voltage at the first frequency applied to the second AC voltage terminal (190), - operating (503) the power converter arrangement (100) in a second operating mode such that -- that the first power converter (110) converts an input alternating voltage at the first alternating voltage terminal (120) with the second frequency into an intermediate circuit voltage applied to the first direct voltage terminal (130), and -- that the second converter (180) converts the intermediate circuit voltage applied to the fourth DC voltage terminal (195) into an output AC voltage applied to the second AC voltage terminal (190) with the second frequency, - Switching (502) between the first and the second operating mode by changing the target output frequency from the first frequency to the second frequency.

8. Computing unit configured to carry out all method steps of a method according to one of the preceding claims.

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

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

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