Carrier-based modulation methods for a matrix converter

Abstract

A method of carrier-based modulation with a dual gate bidirectional switch includes the steps of receiving a sine triangle pulse width modulation (PWM) signal; converting the received sine triangle PWM signal from a voltage source inverter (VSI) input to a current source inverter (CSI) output involving vector matching; converting the CSI output to internal model control (IMG) signal pulses; generating a PWM signal for each dual gate bidirectional switches based on the IMG signal pulses; generating two gate signals for each dual gate bidirectional switch; and selectively applying a phase shift or delay between the gate signals applied to a high side of the dual gate bidirectional switch relative to a low side of the dual gate bidirectional switch.

Description

[0001] CARRIER-BASED MODULATION METHODS FOR A MATRIX CONVERTER

[0002] REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 560.360 filed on March 1, 2024. The entire content of this priority application is incorporated herein by reference in its entirety.

[0004] GOVERNMENT INTEREST

[0005] This invention was made with government support under the DE- EE0009869 contract, awarded by the United States Department of Energy, Energy Efficiency & Renewable Energy EE-1 Office. The U.S. Government has certain rights in the invention.

[0006] TECHNICAL FIELD

[0007] The present application relates to power electronics control and, more particularly, to control of stationary vehicle battery chargers

[0008] BACKGROUND

[0009] Modern power electronics can use complicated control systems to implement modulation techniques. For example, direct current (DC) fast chargers and other power electronics applications can use space vector modulation and calculation of vector modulation based on voltage or current vector selection and time calculation. The execution of these calculations can consume significant computational resources and negatively affect high- frequency operation.

[0010] SUMMARY

[0011] According to one aspect of the disclosure, a method of carrier-based modulation with a dual gate bidirectional switch includes the steps of receiving a sine triangle pulse width modulation (PWM) signal; converting the received sine triangle PWM signal from a voltage source inverter (VSI) input to a current source inverter (CSI) output involving vector matching; converting the CSI output to internal model control (IMC) signal pulses; generating a PWM signal for each dual gate bidirectional switches based on the IMC signal pulses; generating two gate signals for each dual gate bidirectional switch; and selectively applying a phase shift or delay between the gate signals applied to a high side of the dual gate bidirectional switch relative to a low side of the dual gate bidirectional switch.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a block diagram depicting an implementation of an electrical system capable of using the carrier-based modulation methods;

[0014] Figure 2 is a flow chart depicting an implementation of method of carrierbased modulation carried out by a control system;

[0015] Figure 3 is a table depicting an implementation of sector wise CSI switching period calculations;

[0016] Figure 4 is a graph depicting a comparison of intended IMC gate signals to leg voltages of SVPWM;

[0017] Figure 5 is a table depicting an implementation of SVPWM dwell time!

[0018] Figure 6 is a table depicting an implementation of AQCTL settings in ePWM modules; and

[0019] Figure 7 is a table depicting an implementation of register values.

[0020] DETAILED DESCRIPTION

[0021] This disclosure aims to simplify an implementation of complicated modulation techniques through simple sine pulse width modulation (PWM) applicable to a single-stage matrix converter topologies used in power electronics application (e.g., DC fast charger, grid-connected inverter, solid-state transformer). As noted above, the conventional modulation technique uses space vector modulation (SVM) and a relatively complicated calculation of vector modulation based on voltage or current vector selection and time calculation. This calculation may consume heightened computational resources and potentially becomes a limiting factor for high frequency operation. In contrast, the proposed method uses a simplified sine PWM method to generate six gate signals with a unique sequence and relationship with the conventional modulation technique. Once the sequence is identified, the 6 gate signals and 6 additional signals for both top and bottom switches can be directly implemented in a single digital signal processor (DSP) without additional computation and field programmable gate arrays (FPGAs). The direct implementation can optimize power factor correction performance compared to existing modulation techniques without second-order harmonics at low computation power using a single microcontroller.

[0022] Figure 1 depicts an implementation of an electrical system 10 capable of use with the modulation techniques disclosed here. The system 10 includes an electrical grid 12 and a battery electric vehicle (BEV) 14 that can receive electrical power from the grid 12. The electrical grid 12 can include any one of a number of electrical power generators and electrical delivery mechanisms. Electrical generators (not shown) create AC electrical power that can then be transmitted a significant distance away from the electrical generator for residential and commercial use. The electrical generator can couple with the electrical grid 12 that transmits the AC electrical power from the electrical generator to an end user, such as a residence or business.

[0023] The BEV 14 includes one or more rotating electrical machines 16 (also referred to as electric motors) that include a stator having stator windings and a rotor that can be angularly displaced relative to the stator (not shown). In one implementation, the rotating electrical machine 16 is a permanent magnet synchronous electrical machine, which includes a rotor having a plurality of angularly-spaced permanent magnets. The permanent magnets can be made from any one of a number of different materials, one example of which is a neodymium alloy or other rare earth element.

[0024] BEV service equipment 20, also referred to as a BEV charging station, can receive AC electrical power from the grid 12 and provide the electrical power to the BEV 14. The BEV service equipment 20 can include an input terminal that receives the AC electrical power from the grid 12 and communicates the AC electrical power to an on-board vehicle battery charger included on the BEV 14. The on-board vehicle battery charger can include a control system 18 regulating the AC electrical power received from the grid 12 that is supplied to a vehicle battery 24.

[0025] The control system 18 can include a matrix converter that receives AC electrical power from the electrical grid 12, converts the received AC electrical power from one frequency to another frequency, and then rectifies the AC electrical power into DC electrical power that is supplied to the BEV 14. These electronics may include a plurality of MOSFETs that switch on and off according to a choreographed order and timing at the direction of a motor controller to induce rotor angular movement. One example of the matrix converter is disclosed in U.S. Patent Application No. 18 / 197,539 having the title “Seven- Switch Indirect Matrix Converter,” the entire contents of which are incorporated by reference. The switches included in the matrix converter can include a plurality of dual gate bidirectional switches, in one implementation six of the dual gate bidirectional switches. The control system 18 can include a digital signal processor (DSP) for carrying out the method steps disclosed here.

[0026] An electrical cable 22 can detachably connect with an electrical receptacle on the BEV 14 and electrically link a BEV charging station with the BEV 14 so that AC electrical power can be communicated between the charging station and the BEV 14. The BEV charging station can be classified as “Level 2” BEV service equipment that receives 240VAC from the grid 12 and supplies 240VAC to the BEV 14. It is possible the level of AC electrical power input to a charging station and / or the level of AC electrical power output from a charging station is different in other implementations.

[0027] The term “battery electric vehicle” or “BEV’ can refer to vehicles that are propelled, either wholly or partially, by rotating electrical machines or motors. BEV can refer to electric vehicles, plug-in electric vehicles, hybrid-electric vehicles, and battery-powered vehicles. The vehicle battery 24 can supply DC electrical power, that has been converted from AC electrical power, to the electrical machine(s) 16 that propel the BEV. As noted above, the control system 18 can convert the DC electrical power into AC electrical power to induce angular movement of the rotor relative to the stator. The vehicle battery 24 or batteries are rechargeable and can include lead-acid batteries, nickel cadmium (NiCd), nickel metal hydride, lithium-ion, and lithium polymer batteries, to name a few. A typical range of BEV battery voltages can range from 200 to 800V of DC electrical power (VDC).

[0028] Figure 2 depicts an implementation of a method 200 of carrier-based modulation carried out by the control system 18. The control system 200 can directly compare an input reference waveform to an internal triangular carrier waveform and generate gate signals based on this comparison. The control system 200 involves a synchronous reference frame (dq) controller and sine pulse width modulation (PWM) and can initially create a sine triangle PWM signal at step 210. The step 210 can involve determining a state of active power control or reactive power control. The V<i and Vqcommands can be generated, a reference phase voltage (Va, Vb, Vc) can be determined, and the sine triangle PWM signal can be outputted. The waveforms of the sine triangle PWM signal can vary.

[0029] The gate signals can be generated in three separate stages. In one implementation, the method 200 can control dual gate bidirectional six switches (G1-G6). Each of the switches (G1-G6) can have a high side or high switch (indicated with the letter “a” such as Gia) and a low side or a low switch (indicated with the letter “b” such as Gib). A first stage (step 220 of method 200) can involve vector conversion from a voltage source inverter (VSI) input to a current source inverter (CSI) output involving vector matching. A second stage (step 230 of method 200) can convert CSI output to internal model control (IMC) signal pulses. Step 230 involves repetitive voltage pulses at a switching frequency. The step can determine whether a synchronous pulse is greater than zero. If so, a positive pulse can be generated. If the synchronous pulse is not greater than zero, a negative vector can be generated. A PWM signal can be generated using the positive / negative vectors for each of the dual gate bidirectional switches (G1-G6). A third stage (step 240) involves deadtime insertion. At step 240, dual gate signals for each of the switches (G1-G6) can be generated for the “a” side and the “b” side. A determination whether transformer current is positive (polarity) can be made and, if transformer current is positive, the swap of gate signals can be prevented; if the transformer current is negative, the swap of gate signals can be permitted. A modulation of a delay for the gate signals can be carried out at step 240. Using switch Gias a example, the high side of the switch (Gia) can have a gate signal subject to a delay, while the low side of the switch (Gib) can have a delay that is modulated, such that the delay is turned on and off. The method 200 ends.

[0030] The DSP (not shown) can be used to implement the method 200 described above. An implementation of such a DSP can be the TMS320F28379D manufactured by Texas Instruments. Such a DSP can use enhanced pulse width modulation (ePWM) to generate PWM signals. DSPs such as this may be designed to directly compare an input reference waveform to an internal triangular carrier waveform and generate gate signals based on this comparison. With the proposed VSI to CSI to IMC transformation, the transformations can occur after interaction with a carrier waveform, which is not supported by the ePWM. The DSP can still be used for controlling switches such that modulation uses transformation from VSI but is created through limitations of the ePWM. This process can be realized by comparing IMC gate signals to traditional VSI dwelbtime calculations. Six general gate signals can be created, corresponding to six dual gate bidirectional switches, then the internal deadtime module can be used to create twelve gate signals with appropriate overlap and deadtime.

[0031] IMC switching pulses can follow a particular switching sequence, given a group of three switches G1-G3, of the high side or “a” side of the switches, Gia can conduct for a 50% switching period, G2a can conduct for a variable duty cycle, D. and G3a can conduct for the remainder of the switching period. A similar pattern for the lower leg or lower side of switches G1-G3 can be observed with a phase shift (< >) for Glb’GSb with respect to Gla-G3a. A similar pattern exists with respect to G4-G6. A table is shown in Figure 3 depicting an implementation of a sector-wise OSA switching period calculation. The switching states determined through the VSI to CSI to IMC conversion can be compared with conventional leg voltages of the space vector pulse width modulation (SVPWM). SVPWM parameters Ti and T2 can be related to the IMC switching state parameters duty (D), and phase shift such that D=Ti / 2 and < >= 2 / 2. An implementation of a comparison of intended IMC gate signals to leg voltages is shown in Figure 4. The duty cycle (D) and the phase shift (< >) can be calculated using SWPWM parameters an implementation of which is shown in the table of Figure 5.

[0032] Turning to Figure 6, a pattern is shown depicting how an ePWM module of a DSP with an up -down count mode carrier waveform at a switching frequency can be implemented. ePWM modules can be configured using an action qualifier control register (AQCTL), which can have four available registers for each module. The up -down count mode can create the first two registers, one at the zero crossing of the triangular waveform and the other at the peak of the waveform (period P), which can occur at half of the switching frequency. The remaining registers, compare A (CMP A) and compare B (CMPB), can be counters defined at any value less than the switching period and used during the up or down count portion. These action qualifiers can be used to create a 50% duty signal patterns shown in Figure 6.

[0033] The CMPA and CMPB registers can be defined using the duty ratio (D) and an additional variable, overlap time (OT) shown in Figure 7. The overlap time (OT) variable can be included to allow for an appropriate deadtime insertion when creating the final twelve PWM signals. The six signals can be created from action qualifiers, register values, and phase shift for a single switching period in sector one.

[0034] It is to be understood that the foregoing is a description of one or more embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims. As used in this specification and claims, the terms "e.g. " “for example,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open- ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.

Claims

What is claimed is:

1. A method of carrier-based modulation with a dual gate bidirectional switch, comprising the steps of:(a) receiving a sine triangle pulse width modulation (PWM) signal;(b) converting the received sine triangle PWM signal from a voltage source inverter (VSI) input to a current source inverter (CSI) output involving vector matching;(c) converting the CSI output to internal model control (IMC) signal pulses;(d) generating a PWM signal for each dual gate bidirectional switches based on the IMC signal pulses;(e) generating two gate signals for each dual gate bidirectional switch;(f) selectively applying a phase shift or delay between the gate signals applied to a high side of the dual gate bidirectional switch relative to a low side of the dual gate bidirectional switch.

2. The method of claim 1, further comprising the step of determining whether a synchronous pulse is greater than zero.

3. The method of claim 1, wherein a delay is applied to the gate signal applied to the high side of the switch and a phase shift is applied to the gate signal applied to the low side of the switch.

4. The method of claim 1, wherein the gate signals are provided to six dual gate bidirectional switches.

5. The method of claim 1, further comprising the step of determining whether a transformer current is greater than zero and applying the gate signals originally intended for the high side of the dual gate bidirectional switch to the low side of the dual gate bidirectional switch.

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