Voltage boost module for a power converter

Abstract

In one aspect, a power converter includes: an energy storage device; an inverter that is electrically coupled to the energy storage device; and a voltage boosting system that is designed to: to determine a modulation index based on a DC voltage of the energy storage device and a target output voltage of the inverter; and, based on the modulation index, to determine whether the target output voltage lies within a voltage boost range; if the target output voltage lies within the voltage boost range: to determine an adjustment value based on the modulation index; and, based on the adjustment value, to adjust either the target output voltage and / or an associated output voltage phase angle.

Description

TECHNICAL FIELD

[0001] This disclosure relates to a voltage boost module for a power converter. BACKGROUND

[0002] An electrical device, such as a variable-speed drive, a variable-speed drive, or an uninterruptible power supply, may be connected to a high-power alternating current (AC) distribution system, such as a power grid. The electrical device drives, operates, and / or controls a machine or non-machine load. The electrical device includes an electrical grid that converts AC power to direct current (DC) power and can also convert DC power to AC power. SUMMARY

[0003] In one aspect, a power converter includes: an energy storage device; an inverter electrically coupled to the energy storage device; and a voltage boost system configured to: to determine a modulation index based on a DC voltage of the energy storage device and a target output voltage of the converter; and to determine, based on the modulation index, whether the target output voltage is in a voltage boost range; if the target output voltage is within the voltage boost range: determine an adjustment value based on the modulation index; and adjust either the target output voltage and / or an associated output voltage phase angle based on the adjustment value.

[0004] Implementations may include one or more of the following properties.

[0005] The voltage boost system may be configured to: determine an inverter gate command based on the target output voltage and the associated target output phase angle; and provide the inverter gate command to the inverter.

[0006] In some implementations, if the target output voltage is within the voltage boost range, the voltage boost system is configured to determine whether the target output voltage is within either a first voltage boost range or a second voltage boost range. Furthermore, in some implementations, if the target output voltage is within the first voltage boost range, the voltage boost system is configured to adjust the target output voltage based on the adjustment value; and if the target output voltage is within the second voltage boost range, the voltage boost system is configured to adjust the associated target output voltage phase angle based on a second adjustment value.

[0007] The adjustment value may be an adjustment angle that is a function of the modulation index. The voltage boost system may be configured to determine the adjustment value from a predetermined lookup table.

[0008] The power converter may also include a rectifier electrically connected to the energy storage device. The power converter may also include a filter system electrically connected to the energy storage device, wherein the filter system is configured to electrically connect to an alternating current (AC) power source. In these implementations, the voltage boost system may be configured to: determine an inverter gate command based on the target output voltage and the associated target output phase angle; and provide the inverter gate command to the inverter to control the inverter to produce the target output voltage with the target output voltage phase angle, and wherein the peak voltage of the target output voltage is equal to or greater than the peak voltage of the AC power source.

[0009] In another aspect, a control system for an inverter includes: a boost module configured to: access a target output voltage and a target output phase angle of the inverter; determine a modulation index based on a DC bus voltage of an inverter and the target output voltage of the inverter; determine, based on the modulation index, whether the target output voltage is in a linear range of the inverter or in a voltage boost range of the inverter; if the target output voltage is in the voltage boost range: determine an adjustment value based on the modulation index; and, based on the adjustment value, adjust either the target output voltage and / or the target output voltage phase angle; and if the target output voltage is in the linear range of the inverter, the boost module is configured not to adjust the target output voltage and the target output phase angle.The control system also includes a command module configured to: determine an inverter command based on the target output voltage and the target output voltage phase angle; and control the inverter based on the inverter command.

[0010] In another aspect, a method includes: determining a modulation index based on a measured DC bus voltage of an inverter and a target output voltage of the inverter; determining, based on the modulation index, whether a target output voltage of an inverter is within a linear space vector modulation (linear SVPWM) range; if the target output voltage of the inverter is outside the linear range, determining an angle adjustment value based on the modulation index; and, based on the angle adjustment value, adjusting either the target output voltage or the target output phase angle; and if the target output voltage of the inverter is in the linear range, not adjusting the target output voltage or the target output phase angle.

[0011] Implementations may include one or more of the following properties.

[0012] Determining the angle adjustment value based on the modulation index may include determining the angle adjustment value from a lookup table that relates the angle adjustment value to the modulation index. Generating the lookup table may include varying the angle adjustment value for a plurality of different values ​​of the target output phase angle.

[0013] The method may also include determining an inverter command based on the target output voltage and the target output voltage phase angle; and controlling the inverter based on the inverter command. Controlling the inverter based on the inverter command may cause the inverter to output the target output voltage, and the target output voltage has a peak voltage equal to or greater than a peak voltage of an AC input.

[0014] Implementations of any of the techniques described herein may include a device, an apparatus, a system, a control system, machine-executable instructions, and / or a method. The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings and from the claims. DESCRIPTION OF THE DRAWING FIG: 1 is a block diagram of an example of a system including a power converter. FIG: 2 is a schematic diagram of an example of a system including a power converter. Fig. 3 is a block diagram of an example control scheme. Fig. Figure 4 shows an example of an operating hexagon of an inverter. Fig. 5 is a block diagram of an example of a voltage boost module. Fig. Figure 6A is a flowchart of an example of a voltage boost process performed by the voltage boost module of Fig. 5 can be implemented. Fig. Figure 6B shows another example of an operating hexagon of a converter. Fig. 7 shows a flowchart of a process 700A, which is an example of a process for generating a lookup table, and a flowchart of a process 700B, which is an example of a process for obtaining a value of an adjustment parameter from the lookup table. Fig. 8 is a flowchart of an example of a process for generating an inverter gate command. Fig. Figures 9-12 show examples of simulated data. DETAILED DESCRIPTION

[0015] On Fig. 1, a block diagram of a system 100 is shown. The system 100 includes an electrical device or power converter 110 electrically connected to an alternating current (AC) electrical power distribution network 101 and a load 102. The electrical device 110 generates a command signal 104 for the load 102 based on electrical power 105 from the distribution network 101. For example, the electrical device 110 may be a variable speed drive (VSD) or an adjustable speed drive (ASD), and the load 102 may be a machine-type load, such as an induction machine, an induction motor, or a synchronous permanent magnet machine, operating at a speed and torque determined by the command signal 104.In some implementations, the electrical device 110 is an uninterruptible power supply (UPS) that supplies electrical power to a non-machine type load 102, such as a lighting system.

[0016] The electrical device 110 includes a rectifier 117, a direct current (DC) intermediate circuit 118, and an inverter 119. The rectifier 117 includes electronic switches (e.g., diodes) arranged to convert alternating current into direct current, which is stored in the DC intermediate circuit 118. The inverter 119 includes controllable switches (e.g., transistors) controlled to modulate the energy stored in the DC intermediate circuit 118 into the drive signal 104 based on a space vector pulse width modulation (SVPWM) technique.

[0017] A filter system 116 is connected in series with the rectifier 117 between an input node 114 of the device 110 and the distribution network 101. During operation of the electrical device 110, a voltage drop may be present across the filter system 116. As the demand of the load 102 increases, the voltage drop may become significant, reducing the voltage of the drive signal 104 and therefore reducing the voltage available to the load 102. As a result, the operation of the load 102 and / or systems driven by the load 102 and / or dependent on the operation of the load 102 may be impaired.

[0018] Furthermore, although controlling the inverter 119 using an SVPWM technique results in the voltage of the drive signal 104 being approximately 15% higher than a drive signal generated by controlling the inverter 119 with sinusoidal PWM, SVPWM may also face challenges under some circumstances. For example, as the demand of the load 102 increases, the voltage drop across the filter system 116 and the electrical device 110 also increases, reducing the voltage available to the load 102. Furthermore, even if the filter system 116 is removed, if the load 102 is operated in a manner that increases the current drawn (e.g., operating the load 102 beyond one or more of its rated parameters), the conventional SVPWM may not generate sufficient output voltage to sustain the operation of the load 102.

[0019] On the other hand, and as discussed in more detail below, the control system 130 implements a voltage boost module 180 that provides dynamic voltage compensation, enabling more effective use of the inverter 119 and efficiently improving the performance of SVPWM. The voltage boost module 180 is a signal processing-based approach that does not involve any additional hardware and can be used to retrofit existing systems.

[0020] Furthermore, the voltage boost module 180 is computationally efficient. The inverter 119 has a linear operating region and a nonlinear operating region. Outside the linear operating region, the output voltage waveform of the inverter 119 may be distorted and the magnitude of the output voltage waveform may be less than a reference or target voltage, and the voltage available to the load 102 may be reduced. To address this challenge and enable the inverter 119 to generate sufficient voltage throughout its operating range, the control system 130 includes the voltage boost module 180. The voltage boost module 180 is computationally efficient because it uses a single variable (an adjustment value (α), discussed further below) to account for all conditions in the nonlinear region.The voltage boost module 180 provides a unified solution that efficiently transitions from operation of the inverter in the linear region 119 to operation of the inverter in the non-linear region 219 and then to six-step operation.

[0021] The electrical power distribution network 101 may, for example, be a multi-phase electrical power network that supplies electricity to industrial, commercial, and / or residential customers. The AC electrical power distribution network 101 distributes alternating electrical power having, for example, a fundamental frequency of 50 or 60 hertz (Hz). The distribution network 101 may have an operating voltage of, for example, up to 690 V. The network 101 may, for example, include one or more transmission lines, distribution lines, power distribution or substation transformers, electrical cables, and / or any other mechanism for transmitting electricity.

[0022] The electrical device 110 is housed in a housing or enclosure 111. The housing 111 is a three-dimensional body made of a strong and robust material that protects the electrical device 110. The input node 114 is accessible from an exterior of the housing 111 so that the electrical device 110 can be connected to the distribution network 101. The electrical device 110 also includes an output terminal (not shown) accessible from an exterior of the housing 111. The load 102 is connected to the electrical device 110 at the output terminal.

[0023] Fig. 2 is a schematic diagram of a system 200. The system 200 includes an electrical device or power converter 210 connected to a three-phase AC electrical power distribution network 201 and a load 202. The system 200 also includes an inverter 219 that provides a three-phase drive signal 204 to the load 202 and a control system 230 that controls the inverter 219 to generate the drive signal 204 based on a control scheme 306. The control scheme 306 is based on SVPWM technology and includes a voltage boost module 380 that provides dynamic voltage compensation when the inverter 219 is operated outside its linear operating range (for example, when the voltage demand of the load 202 increases).

[0024] An overview of the system 200 is provided prior to a more detailed discussion of the control scheme 306 and the boost module 380.

[0025] In the example of Fig. 2, the load 202 is a three-phase motor 202, such as an induction motor or a synchronous permanent magnet excitation machine. The motor 202 includes a stator 209 that is spatially fixed and a rotor 208 that rotates relative to the stator 209 when the drive signal 204 is applied. The stator 209 includes one electrical winding per phase: 209a, 209b, and 209c. Loads other than a motor may be used in the system 200.

[0026] The electrical power distribution network 201 distributes alternating electrical power having, for example, a fundamental frequency of 50 or 60 hertz (Hz). The distribution network 201 may have an operating voltage of up to 690 V. The distribution network 201 may include, for example, one or more transmission lines, distribution lines, electrical cables, and / or any other mechanism for transmitting electricity. The distribution network 201 includes three phases, referred to as a, b, and c.

[0027] The electrical device 210 includes input nodes 214a, 214b, 214c, each of which is electrically coupled to a respective one of the three phases a, b, c of the distribution network 201 via a respective filter system 216a, 216b, 216c. Each filter system 216a, 216b, 216c may be an inductor.

[0028] The electrical device 210 includes a rectifier 217, a DC link 218, and the converter 219. The rectifier 217 is a three-phase six-pulse bridge that includes six electronic switches. In the example of Fig. Figure 2 shows the six electronic switch diodes D1-D6. Each diode D1-D6 includes a cathode and an anode and is associated with a forward bias voltage. Each diode D1-D6 allows current to flow in the forward direction (from the anode to the cathode) when the anode voltage is at least the bias voltage greater than the cathode voltage. If the voltage difference between the anode and cathode is less than the forward bias voltage, the diode does not conduct current in the forward direction.

[0029] Input node 214a is electrically connected to the anode of diode D1 and the cathode of diode D4. Input node 214b is electrically connected to the anode of diode D3 and the cathode of diode D6. Input node 214c is electrically connected to the anode of diode D5 and the cathode of diode D2. Diodes D1-D6 rectify the input currents ia, ib, ic into a direct current id.

[0030] Diodes D1-D6 are also electrically connected to the DC link 218. The cathode of each diode D1, D3, D5 is electrically connected to the DC link 218, and the anode of each diode D2, D4, D6 is electrically connected to the DC link 218. The DC link 218 includes a capacitor network C. The rectified current id flows into the capacitor network C and is stored. The capacitor network C includes one or more capacitors that store electrical energy when the rectified current id is flowing from the rectifier 217 and discharge the stored electrical energy when the rectified current id is not flowing from the rectifier 217.

[0031] The converter 219 converts the DC power stored in the capacitor network C into a three-phase AC drive signal 204, which is delivered to the load 202. The converter 219 includes a network of electronic switches SW1-SW6 controlled by the control system 230 to generate the drive signal 204. Each of the switches SW1-SW6 can be, for example, a power transistor. The three-phase drive signal 204 has phase components 204u, 204v, 204w, each of which is provided to each of the three phases of the load 202.

[0032] The system 200 also includes a sensor system 238 that measures and / or estimates characteristics or parameters of the drive signal 204 and / or the motor 202. The sensor system 238 may, for example, include current sensors that measure the amount of current drawn in each phase of the motor 202 and / or voltage sensors that measure the voltage of each phase component 204u, 204v, 204w of the drive signal 204. The sensor system 238 may also include sensors that measure the angular position of the rotor 208 of the motor 202 and / or the angular velocity of the rotor 208. In some implementations, the control system 230 uses data from the sensor system 238 (apart from directly measured position data) to estimate the angular position and / or angular velocity of the rotor 208 based on a sensorless technique.

[0033] The control system 230 controls the switching pattern of the switches SW1-SW6 to generate the drive signal 204 with certain characteristics (e.g., amplitude, frequency, and / or phase). The control system 230 implements an SVPWM control scheme 306 that includes the voltage boost module 380, both of which are Fig. 3 are discussed.

[0034] The control system 230 includes an electronic processing module 232, an electronic memory 234, and an input / output (I / O) interface 236. The electronic processing module 232 includes one or more electronic processors. The electronic processors of the module 232 may be any type of electronic processor and may or may not include a general-purpose central processing unit (CPU), a graphics processing unit (GPU), a microcontroller, a field-programmable gate array (FPGA), a complex programmable logic device (CPLD), and / or an application-specific integrated circuit (ASIC).

[0035] Electronic memory 234 may be any type of electronic memory capable of storing data and instructions in the form of computer programs or software, and electronic memory 234 may include volatile and / or non-volatile components. Electronic memory 234 and processing module 232 are coupled such that processing module 232 can access, read, and write data to electronic memory 234. Electronic memory 234 stores instructions that, when executed, cause electronic processing module 232 to analyze data and / or retrieve information. Electronic memory 234 may also store information about system 200. For example, electronic memory 234 may store information about motor 202 or inverter 219.

[0036] In addition, the electronic memory 234 may store executable instructions that implement the control scheme 306 and the voltage boost module 380. The electronic memory 234 may also store data and / or information used in the control scheme 306 and / or the voltage boost module 380. For example, the electronic memory 234 may store thresholds and / or limits associated with operating modes of the inverter 219. The electronic memory 234 also stores lookup tables 285 and 286, which are described in more detail with respect to Fig. 6A, Fig. 6B and Fig. 7. Lookup tables 285 and 286 are used in control scheme 306 and / or boost module 380.

[0037] The I / O interface 236 may be any interface that enables a human operator and / or an autonomous process to interact with the control system 230. The I / O interface 236 may include, for example, a display (such as a liquid crystal display (LCD)), a keyboard, audio input and / or output (such as speakers and / or a microphone), visual output (such as lights, light-emitting diodes (LEDs)) in addition to or instead of the display, a serial or parallel port, a Universal Serial Bus (USB) connection, and / or any type of network interface, such as Ethernet. The I / O interface 236 may also enable communication without physical contact through, for example, an IEEE 802.11, Bluetooth, or a near-field communication (NFC) connection.For example, the control system 230 may be operated, configured, modified, or updated via the I / O interface 236.

[0038] The I / O interface 236 may also enable the control system 230 to communicate with components within the system 200 and with systems external to and remote from the system 200. For example, the I / O interface 236 may control a switch or switching network (not shown) or a circuit breaker within the system 200 that allows the electrical device 210 to be disconnected from the distribution network 201. In another example, the I / O interface 236 may include a communications interface that enables communication between the control system 230 and a remote station (not shown) or between the control system 230 and a separate monitoring device. The remote station or monitoring device may be any type of station through which an operator can communicate with the control system 230 without making physical contact with the control system 230.The remote station may be, for example, a computer-based workstation, a smartphone, a tablet, or a laptop computer connected to the control system 230 via a service protocol, or a remote controller connected to the control system 230 via a radio frequency signal.

[0039] Fig. Figure 3 is a block diagram of control scheme 306. Control scheme 306 includes voltage boost module 380, which generates inverter gate command 351 to control switches S1 through S6 of inverter 219. Inverter 219 generates three-phase drive signal 204 in response to being controlled by inverter gate command 351.

[0040] The control scheme 306 includes a comparator 359 that compares a target angular velocity (ω*) of the motor 202 with an observed angular velocity (ωo) of the rotor 208 and provides the difference (Δω) to a speed controller 352. The observed angular velocity (ωo) is determined by providing a measured or estimated angular position (θo) of the rotor 208 to a derivation block 358. The observed angular position (θo) of the rotor 208 is output by an angular position block 367, which determines the observed angular position (θo) from a position sensor in the sensor system 238 or by employing a sensorless angular position estimation technique. The derivation block 358 determines the observed angular velocity (ωo) by calculating the rate of change in the angular position (θo) over time.

[0041] The sensor system 238 also measures the current drawn by each phase (each stator winding 209a, 209b, 209c) of the motor 202. The measured currents are ia, ib, and ic. The measured currents ia, ib, ic are provided to a modulation block 356, which implements the Clarke transform to transform the three-phase currents (ia, ib, ic) into two orthogonal current components: a component iα along the α-axis and a component iβ along the β-axis (which is orthogonal to the α-axis). The Clarke transformation projects a three-phase quantity (such as the current flowing in the windings 209a, 209b, 209c of the stator 209 or the voltage applied to the windings 209a, 209b, 209c of the stator 209) into a two-dimensional stationary coordinate system defined by the α-axis and the β-axis. The Clarke transformation is shown in equation (1): iαβ=23[1−12−12032−32][iaibic] where ia, ib, ic are the instantaneous currents in the stator windings 209a, 209b, 209c and i αβ is a vector that includes a component along the α-axis (365) and a component along the β-axis (366). Vectors 365 and 366 are provided to a modulation block 364 that implements the Park transform. The Park transform rotates the stationary α, β-axes at a frequency ω.

[0042] The Park transformation is shown in equation (2): idq=[cos(θ)sin(θ)−sin(θ)cos(θ)][iαiβ] where i dq is a vector including a component along the d-axis (ido, or the observed d-axis current) and a component along the q-axis (iqo, or the observed q-axis current), and 0 is the observed angular position (θo) of the rotor 208 of the motor 202.

[0043] The speed controller 352 generates a torque command Te*, which is provided to a current command generator block 353. The current command generator block 353 generates a d-axis current command id* and a q-axis current command iq*. The d-axis current command id* is compared with the observed d-axis current (ido) at a comparator 357 to determine a difference (Δid) between id* and ido*, and the difference (Δid) is provided to a d-axis current controller 354d. The q-axis current command iq* is compared with the observed q-axis current (iqo) at a comparator 361 to determine a difference (Δiq) between iq* and iqo*, and the difference (Δiq) is provided to a q-axis current controller 354q.

[0044] The d-axis current controller 354d is a PI controller (proportional-integral controller) with a predetermined gain constant Kd. The q-axis current controller 354q is a PI controller with a predetermined gain constant Kq. The d-axis current controller 354d determines a d-axis voltage command ud* that represents the d-axis current error (Δi d ). The q-axis current controller 354q determines a d-axis voltage command uq* that minimizes the q-axis current error (Δiq).

[0045] The d-axis voltage command ud* and the q-axis voltage command uq* are provided to a modulation block 355 that implements the inverse Park transform. The inverse Park transform projects the d-axis and q-axis voltage commands (ud*, uq*) into the stationary α, β reference frame. The outputs of the modulation block 355 are uα* and uß*, which are the components of the voltage to be applied to the stator 209 in the stationary α, β reference frame.

[0046] The voltage commands uα* and uß* are provided to the voltage boost module 380. The voltage boost module 380 implements an SVPWM-based overmodulation control to generate the inverter gate command 351 based on the voltage commands ua* and uß*.

[0047] Inverter 219 includes controllable switches S1 through S6, each of which can be controlled to be in an ON state or an OFF state. For example, each switch S1 through S6 can be turned ON or OFF by controlling the voltage at the switch's gate. The state of switches S1 through S6 is timed and changed in a switching pattern defined by inverter gate command 351. Switches S1, S3, and S5 are the upper switches, and switches S4, S6, and S2 are the lower switches. There are eight valid switching configurations or state combinations for switches S1, S3, and S5. The switching states are represented by space vectors U1 through U8. The switching states U1 through U8 for the upper switches S1, S3, and S5 are shown in Table 1: Raumvektor S1 S3 S5 U1 1 0 0 U2 1 1 0 U3 0 1 0 U4 0 1 1 U5 0 0 1 U6 1 0 1 U7 0 0 0 U8 1 1 1

[0048] At any given time, the state of each lower switch S4, S6, S2 is the opposite state of the respective upper switch S1, S3, S5, so there are eight SVPWM switching configurations or combinations for the inverter 219.

[0049] On Fig. 4 Referring to Figure 4, the six non-zero vectors (U1 to U6) define a hexagon 439 and six sectors (1 to 6) in a rectangular coordinate system (Re, Im). The angle between any two adjacent non-zero vectors (U1 to U6) is 60 degrees (°). The two zero vectors (U7 and U8) are located at the origin. Hexagon 439 represents the operating limit of the converter 219. The switching states U1 to U8 are combined to approximate a voltage vector of any magnitude and angle within hexagon 439. For example, a desired inverter output voltage with a magnitude represented by the vector Vref and a phase angle θref that places the voltage vector in sector 1 is achieved by a switching sequence that employs two adjacent switching states (U1 and U2 in this example) for a specified time period and a zero vector (U7 or U8) for the remainder of the period.

[0050] The voltage commands uα* and uß* input to the voltage boost module 380 define the vector Vref at a phase angle (θref) in Fig. 4. The voltage vector (Vref) and the angle (θref) are referred to as the target or reference voltage and the target or reference angle. The length of the vector Vref is characterized by the modulation index (M), which is determined by equation (3): M=Vref2πVdc where M is the modulation index, Vref is the amplitude of the reference or target voltage (the length of the vector Vref in Fig. 4) and Vdc is the measured voltage across the DC link 218.

[0051] Fig. 4 also includes a first circle 441 (dashed line) inscribed within hexagon 439 and a second circle 443 (dash-dotted line) having a larger radius than the first circle 441. The first circle 441 defines the linear operating range 448 of the inverter 219. Reference voltages having a smaller modulation index (M) than the radius of the first circle 441 are within the linear operating range 448 of the inverter 219. In the linear operating range 448, the inverter 219 acts as a linear amplifier when controlled with SVPWM. For reference voltages (Vref) with modulation indices (M) within the circle 441, the output voltage of the inverter 219 can be modeled as a linear function of the inverter gain, the voltage of the DC link 218, and the target voltage Vref. The radius of the first circle 441 may, for example, correspond to a modulation index (M) of 0.906.In this example, target voltages associated with a modulation index of less than 0.906 are within the linear operating range 448 of the 219 inverter.

[0052] Reference voltages that have a modulation index greater than the radius of the first circle 441 are not within the linear operating range 448 of the converter 219. For example, reference voltages with a modulation index (M) in the ring between the first circle 441 and the second circle 443 or outside the second circle 443 are outside the linear operating range 448 of the converter 219. The portion of the ring between the first circle 441 and the second circle 443 is a first nonlinear region 445 (or a first voltage boost region 445), and the area outside the second circle 443, which is within the hexagon, is a second nonlinear region 447 (or a second voltage boost region 447). The radius of the second circle 443 may correspond to a modulation index (M) of 0.951.

[0053] A conventional SVPWM technique cannot command the inverter 219 in a manner that allows the inverter 219 to generate sufficient voltage to reach the reference voltage Vref outside the linear operating range 448. Outside the linear operating range 448, the output voltage waveform of the inverter 219 is distorted, and the magnitude of the output voltage waveform is less than the reference or target voltage (Vref). To address this challenge and enable the inverter 219 to generate sufficient voltage throughout its operating range, the control system 230 includes the voltage boost module 380.

[0054] Fig. Figure 5 is a block diagram of the voltage boost module 380. The voltage boost module 380 includes a correction module 381 and a command module 382. The correction module 381 determines a voltage command V* and a phase angle θ* based on the reference or target voltage Vref, the reference or target phase angle θref, and the voltage at the DC link 218 (VDC). The command module 382 determines the inverter gate command 351 based on an SVPWM technique that uses the voltage command V*, the phase angle θ*, S (the SVPWM sector determined by the phase angle θ*), and the voltage of the DC link 218 (VDC) as inputs. The inverter gate command 351 includes components CMP1, CMP2, CMP3, each of which is a calculated comparison value that defines a switching pattern for a phase of the inverter 219.

[0055] The correction module 381 is described in more detail with regard to Fig. 6A and Fig. 6B. The command module 382 is discussed in more detail with respect to Fig. 8 discussed.

[0056] On Fig. Referring to Figure 6A, a flow diagram of a process 600 is shown. The process 600 is an example of a voltage boost process that may be implemented by the correction module 381. The process 600 may be implemented as executable instructions stored in the electronic memory 234 and executed by the electronic processing module 232. The process 600 may be implemented as software and may be programmed into a control system in an existing power converter. Furthermore, the process 600 may be implemented as a control system or controller installed in an existing power converter as a software update or as part of a firmware update.

[0057] The process 600 begins, and the modulation index (M) is determined (610) using equation (3). To determine the modulation index (M) using equation (3), the voltage of the DC link 218 (VDC) is a measured value of the voltage at the DC link 218, and Vref is the reference voltage associated with the voltage commands (uα*, uβ*) provided by the modulation block 355 ( Fig. 3) are issued.

[0058] The modulation index (M) is compared to a linear operating range limit to determine if the inverter 219 can generate the reference voltage (Vref) in the linear operating range 448 using conventional SVPWM (615). If the modulation index (M) associated with the reference voltage (Vref) is equal to or less than the radius of the circle 441, the inverter 219 can generate the reference voltage (Vref) while operating in the linear operating range 448. The process 600 proceeds to (620), and the reference voltage (Vref) and the reference phase angle (θref) are output by the correction module 381 as the output voltage (V*) and the output phase angle (θ*). In other words, if the modulation index (M) is less than or equal to the linear operating range limit, no modification or adjustment of the reference voltage (Vref) or the reference phase angle (θref) occurs.

[0059] If it is determined at (610) that the modulation index (M) is not within the linear operating region 448, the process 600 proceeds to (625) to determine whether the inverter 219 would operate in the first nonlinear region 445 or the second nonlinear region 447 to produce the target output voltage. If the modulation index (M) has a value between the radius of the first circle 441 and the radius of the second circle 443, the inverter 219 would operate in the first nonlinear region 445 to produce the reference voltage Vref. If the modulation index (M) has a value greater than the radius of the second circle 443, the inverter 219 would operate in the second nonlinear region 447 to produce the reference voltage Vref.

[0060] If the inverter 219 were to operate in the first nonlinear region 445 or the second nonlinear region 447 to generate the reference voltage Vref, an adjustment value (α) is determined based on the modulation index (M). The adjustment value (α) is a specific angle value that adjusts the reference voltage (Vref) and / or the phase angle (θref) so that the inverter 219 can accurately output the reference voltage Vref. Fig. Figure 6B shows a graphical example of an adjustment value (α). In the example of Fig. 6B, the reference voltage (Vref) has a modulation index (M) that lies within the first nonlinear region 445. Circle 649 (long dashed line style) is the ideal curve defined by the reference voltage Vref. However, curve 649 exceeds the operating hexagon 439 of inverter 219 at some points. The adjustment value (α) defines an adjusted curve 687 (bold line) that achieves the same base voltage as curve 649 and does not exceed the operating hexagon 439 of inverter 219.

[0061] The first lookup table 285 relates the adjustment value (α) and the modulation index (M) in the first nonlinear region 445. The second lookup table 286 relates the adjustment value (α) and the modulation index (M) in the second nonlinear region 447.

[0062] To Fig. Returning to Figure 6A, if the converter 219 were operating in the first nonlinear region 445, the adjustment value (α) for the modulation index (M) determined in (610) is obtained (627) from the first lookup table 285. The first lookup table 285 contains an adjustment value (α) for each of a plurality of modulation index values ​​(M) in the first nonlinear region 445. An example of the first lookup table is shown in Table 2: α (Radianten) Modulationsindex (M) 0 0,95142615 0,00068569 0,95136157 0,03205707 0,95117309 0,04274276 0,95045491

[0063] The modulation index (M) determined in (610) is provided to the lookup table 285, and the adjustment value (α) corresponding to this modulation index (M) is returned as output. If the modulation index (M) determined in (610) is not contained in the lookup table 285, the adjustment value (α) is determined by interpolating between adjustment values ​​for other modulation indices (M) contained in the lookup table 285. In other implementations, a function or functions can be derived from the values ​​of the adjustment value (α) in the lookup table 285 and used to estimate the adjustment value (α) for other modulation indices. The development of the lookup table 285 is described with respect to Fig. 7 discussed.

[0064] The obtained adjustment value (α) is applied to the reference voltage (Vref) and the reference phase angle (θref) (630). Equations (4) and (5) show the adjustment for the first nonlinear region 445: V∗=33VDCcos(π6−α) θ∗=θrefmod(π3) where in equation (4), V* is the adjusted voltage command, VDC is the measured voltage at the DC link 218, and α is the adjustment value obtained in (627). In equation (5), θ* is the adjusted phase angle, θref is the reference phase angle, and mod is the modulo operation. The adjusted voltage command (V*) and the adjusted phase angle (θ*) determined in equations (4) and (5) are the outputs of the correction module 381 (620).

[0065] Returning to (625), if the converter 219 were operating in the second nonlinear region 447 to generate the reference voltage (Vref), the adjustment value (α) is obtained from the second lookup table 286 (632). The second lookup table 286 includes an adjustment value (α) for each of a plurality of modulation index values ​​(M) in the second nonlinear region 447. An example of the second lookup table 286 is shown in Table 3, with the adjustment value (α) in the left column and corresponding modulation index values ​​(MI) in the right column: α (Radianten) Modulationsindex (MI) 0 0,951473244 0,010685689 0,953426394 0.021371379 0,955377105 0,032057068 0,957322935 0,042742757 0,959261446 0,053428446 0,961190198 0,064114136 0,963106756 0,074799825 0,965008682

[0066] To obtain the adjustment value (α), the modulation index (M) determined in (610) is provided to the second lookup table 286, and the adjustment value (α) corresponding to this modulation index (M) is returned as output. To provide a more specific example based on Table 3, if the modulation index (M) determined in (610) is equal to 0.953426394, the correction module 381 accesses the second lookup table 286 and returns a value of 0.010685689 as the adjustment value (α).

[0067] The adjustment value (α) is used to determine the adjusted voltage command (V*) and the phase angle (θ*) (635). The voltage command adjustment for the second nonlinear region 447 is shown in equation (6): V∗=23VDC where V* is the adjusted voltage command and VDC is the voltage at the DC link 218. The adjusted reference phase angle (θ*) is determined from one of equations (7), (8), (9), depending on the value of the adjustment value (α) determined in (632). θ∗=0 θ∗=π3 θ∗=h[(θrefmod(π3)−α)] where h=11−(6απ)

[0068] Equation (7) applies if the value of (α) is greater than or equal to θrefmodπ3 Equation (8) is valid if the size (θrefmodπ3) greater than or equal to the size (π3−α) Otherwise, equation (9) applies. The adjusted voltage command (V*) and the adjusted phase angle (θ*) are the outputs of the correction module 381 (620).

[0069] In addition to outputting the voltage command (V*) and the phase angle (θ*), the correction module 381 may also output the SVPWM sector (S) associated with the phase angle (θ*). The sectors (S) are Fig. 4 and are determined as follows: Sector 1: θ* = 0° to 60°; Sector 2, 60° < θ* ≤ 120°; Sector 3: 120° < θ* ≤ 180°; Sector 4: 180° < θ* ≤ 210°; Sector 5: 210° < θ* ≤ 270°; and Sector 6: 270° < θ* ≤ 360°.

[0070] Fig. 7 is a flow diagram of a process 700A for creating a lookup table relating the adjustment parameter (α) to the modulation index (M). Fig. 7 also includes a flowchart of a process 700B for obtaining a value of the adjustment parameter using the lookup table generated by process 700A. Processes 700A and 700B are performed by control system 230. Process 700A may be performed before process 600 to generate lookup tables 285 and 286 before process 600 begins. Other implementations are possible. For example, process 700A may be performed with process 600. For example, process 700A may be called at (627) and / or (632) to obtain the value of the control parameter (α) without necessarily creating lookup tables 285 and / or 286 before initiating process 600. Process 700B is performed after the lookup table has been created by process 700A.

[0071] The voltage command (V*) is expressed as follows: V∗=1π∫02πf(θ)cos(θ)dθ which can also be expressed as shown in equation (12): V∗=4π∫0αf1(θ)cos(θ)dθ+∫απ3−αf2(θ)cos(θ)dθ+∫π3−απ3+αf3(θ)cos(θ)dθ+∫π3+ααf4(θ)cos(θ)dθ

[0072] When the converter 219 operates in the first non-linear range 445: f1=(33VDCcos(π6−α))cos(θ) f2=(33VDCcos(π6−θ))cos(θ) f3=(33VDCcos(π6−α))cos(θ) and f4=(33VDCcos(π2−θ))cos(θ)

[0073] When the converter 219 operates in the second non-linear region 447: f1=23VDC f2=(33VDCcos(π6−θ'))cos(θ') where θ' = h(θ-α) and h is defined as shown in equation (10), f3=13VDC and f4=(33VDCcos(π2−θ'))cos(θ')

[0074] To prepare the first lookup table 285, the adjustment value (α) is set to a specific numerical value (710). The adjustment value (α) can be set to the specific numerical value randomly or intentionally. The voltage command (V*) is determined using equation (12) and equations (13) to (16) for the specific numerical value of (α) (720). The modulation index (M) is determined using equation (3), where V* from (720) is used as the value of Vref (730). This modulation index (M) is associated with the specific numerical value used for (α). The modulation index (M) is stored (740) along with the specific numerical value used as (α) as an entry in the first lookup table 285.If more entries are to be added to the first lookup table (745), process 700A returns to (710) and repeats (710) through (740) until the lookup table 285 is complete (745). Any criterion may be used to determine whether the first lookup table 285 is complete. For example, the number of entries for the first lookup table 285 may be a predetermined number of entries, and the first lookup table 285 is determined to be complete when this number of entries has been calculated and entered into the lookup table 285. If the lookup table 285 is complete (245), process 700A outputs the lookup table 285, for example, by storing the lookup table in the electronic memory 234.

[0075] Process 700B is an example of using the first lookup table 285. To use the first lookup table 285, the lookup table 285 is accessed (750), and a value of the modulation index (M) in the first nonlinear region 445 is provided as the input to the first lookup table 285 (755). The adjustment value (α) corresponding to this modulation index (M) is returned as the output (760). Process 700B may be called at (627) to obtain the adjustment value for the first nonlinear region 445.

[0076] The second lookup table 286, which relates the adjustment value (α) to the modulation index (M) in the second nonlinear region 447, is also created using process 700A, with the exception of the voltage command (V*), which is determined for the determined numerical value of (α) using equation (12) and equations (17) through (20). After the voltage command (V*) for the determined value of (α), the modulation index (M) is determined using equation (3). The determined modulation index (M) is associated with the determined value of (α). By repeatedly varying (α) and determining the modulation index (M) associated with each value of (α), and storing the value of (α) in conjunction with its corresponding modulation index (M), the entries for the second lookup table 286 are generated until the second lookup table 286 is complete.

[0077] The process 700B is used to obtain a value of (α) for a particular modulation index (M) in the second nonlinear region 447.

[0078] Fig. 8 is a flow diagram of a process 800 implemented by the command module 382 to generate the inverter gate command 351 using the outputs of the correction module 381.

[0079] Variables (d1, d2) are determined based on the voltage command (V*) and phase angle (θ*) output by correction module 381 (810). Variables d1 and d2 are the calculated dwell ratios for each active voltage vector used to compose voltage during a switching cycle in SVPWM. The sum of d1 and d2 (d1+d2) should not be greater than 1 for inverter 219 to operate within hexagon 439, which defines the operating limit of inverter 219. If the sum of d1 and d2 is greater than 1, a scaling adjustment is performed using process 800.

[0080] The variables d1 and d2 are determined as follows: d1=3V*VDCsin(π3−θ*) d2=3V*VDCsin(θ*) where V* is the voltage command (V*) from the correction module 381, 0* is the phase angle from the correction module 381, and VDC is the voltage at the DC link 218. The variables are summed and compared to a threshold value of 1 to ensure that the output voltage vector does not exceed the operating limit of the converter. If the sum of d1 and d2 is greater than the threshold, a scaling adjustment (820) is performed for the values ​​of variables d1 and d2 as follows: d1'=d1d1+d2 d2'=d2d1+d2 The value of d1 is set to d1' and the value of d2 is set to d2'.

[0081] If the sum of d1 and d2 does not exceed the threshold, the values ​​of variables d1 and d2 are not adjusted.

[0082] The inverter gate command 351 is determined (825) based on the variables d1 and d2 and the sector (S) of the voltage command (V*). The inverter gate command 351 defines a switching pattern for each phase of the inverter 219 (CMP1, CMP2, CMP3). One of equations (25) to (31) is used to determine the inverter gate command 351, with the appropriate equation being selected based on the sector (S) of the voltage command (V*).

[0083] For a voltage command (V*) with S = 1, equation (25) determines the inverter gate command 351 as follows: CMP1: (1-d1-d2)*TB, CMP2: (1+d1-d2)*TB, CMP3: (1+d1+d2)*TB.

[0084] For a voltage command (V*) with S = 2, equation (26) determines the inverter gate command 351 as follows: CMP1: (1+d2-d1)*TB, CMP2: (1-d1-d2)*TB, CMP3: (1+d1+d2)*TB.

[0085] For a voltage command (V*) with S = 3, equation (27) determines the inverter gate command 351 as follows: CMP1: (1+d1+d2)*TB, CMP2: (1-d1-d2)*TB, CMP3: (1+d1-d2)*TB.

[0086] For a voltage command (V*) with S = 4, equation (28) determines the inverter gate command 351 as follows: CMP1: (1+d1+d2)*TB, CMP2: (1+d2-d1)*TB, CMP3: (1-d1-d2)*TB.

[0087] For a voltage command (V*) with S = 5, equation (29) determines the inverter gate command 351 as follows: CMP1: (1+d1-d2)*TB, CMP2: (1+d1+d2)*TB, CMP3: (1-d1-d2)*TB.

[0088] For a voltage command (V*) with S = 6, equation (30) determines the inverter gate command 351 as follows: CMP1: (1-d1-d2)*TB, CMP2: (1+d1+d2)*TB, CMP3: (1+d2-dl)*TB.

[0089] If the sector (S) is unknown, equation (31) determines the inverter gate command as follows: CMP1 = CMP2 = CMP3 = 0*TB = 0.

[0090] In equations (25) to (31), TB is a value equal to the timer base period divided by two. The timer base period is the timer counter value fixed for a specific switching frequency of switches S1 to S6.

[0091] Fig. 9 and Fig. 10 shows data from a simulation of a system using a conventional SVPWM technique without the voltage boost module 380. Fig. 11 and Fig. 12 shows data from a simulation of the same system when using the voltage boost module 380. The simulated system was a power converter with a structure similar to that shown in Fig. 2. The input voltage was 342 V at 50 Hz, the 700 microhenry (µH) AC inductors were connected in series with the rectifier, and the load was a motor with a torque of 86 newton meters (Nm) and a modulation index (M) of 1. Therefore, the converter did not operate in the linear operating region in the simulation.

[0092] Fig. Figure 9 shows the output voltage between two phases (in volts) of each phase as a function of time, which was approximately 338 V at the most (less than the input voltage). In addition, the output voltage ( Fig. 9) heavily distorted. Fig. Figure 10 shows the output reference phase angle (in radians) as a function of time. Fig. 9 and Fig. 10 have the same time axis and show the same time period. The voltage boost module 380 was not used in the simulation, which Fig. 9 and Fig. 10 generated the data shown.

[0093] Fig. Figure 11 shows the three-phase voltage output as a function of time when using the voltage boost module 380. Fig. Figure 12 shows the output reference phase angle as a function of time when using the boost module 380. Fig. 11 and Fig. 12 have the same time axis and show the same time period. As in Fig. As shown in Figure 11, the peak voltage output between two phases with the boost module 380 was approximately 353 V, which is higher than the input voltage (342 V in this example). Therefore, the voltage boost module 380 was able to increase the output voltage so that the system provided a sufficient output voltage even at a modulation index (M) of 1 (where the converter is not in the linear range). In addition, although the output voltage waveform ( Fig.11) is not purely sinusoidal, the output voltage has lower distortion than the output waveform generated without the voltage boost module 380 and has been maximized in a six-step operation without PWM switching events.

[0094] These and other implementations are within the scope of the claims.

Claims

[1] Power converter, comprising: an energy storage device; an inverter electrically coupled to the energy storage device; and a voltage boosting system designed to: to determine a modulation index based on a DC voltage of the energy storage device and a target output voltage of the converter; and to determine whether the target output voltage is within a voltage boost range based on the modulation index; If the target output voltage is within the voltage boost range: determine an adjustment value based on the modulation index; and adjust either the target output voltage and / or an associated output voltage phase angle based on the adjustment value. [2] The power converter of claim 1, wherein the voltage boost system is configured: to determine an inverter gate command based on the target output voltage and the associated target output phase angle; and to provide the inverter gate command to the inverter. [3] The power converter of claim 1, wherein, if the target output voltage is in the boost voltage range, the boost voltage system is configured to determine whether the target output voltage is in either a first boost voltage range or a second boost voltage range. [4] The power converter of claim 3, wherein, if the target output voltage is in the first voltage boost range, the voltage boost system is configured to adjust the target output voltage based on the adjustment value; and if the target output voltage is in the second voltage boost range, the voltage boost system is configured to adjust the associated target output voltage phase angle based on a second adjustment value. [5] The power converter of claim 1, wherein the adjustment value comprises an adjustment angle that is a function of the modulation index. [6] The power converter of claim 5, wherein the voltage boost system is configured to determine the adjustment value from a predetermined lookup table. [7] The power converter of claim 1, further comprising a rectifier electrically connected to the energy storage device. [8] The power converter of claim 7, further comprising a filter system electrically connected to the energy storage device, wherein the filter system is configured to electrically connect to an alternating current (AC) power source, and wherein the voltage boost system is designed to determine an inverter gate command based on the target output voltage and the associated target output phase angle; and provide the inverter gate command to the inverter to control the inverter to generate the target output voltage with the target output voltage phase angle, and wherein the peak voltage of the target output voltage is equal to or greater than the peak voltage of the AC source. [9] Control system for a converter, the control system comprising: a lifting module designed to: access a target output voltage and a target output phase angle of the inverter; to determine a modulation index based on a DC bus voltage of an inverter and the target output voltage of the inverter; to determine, based on the modulation index, whether the target output voltage lies in a linear range of the converter or in a voltage boost range of the converter; if the target output voltage is within the voltage boost range: to determine an adjustment value based on the modulation index; and to adjust the target output voltage and / or the target output voltage phase angle based on the adjustment value; and if the target output voltage is within the linear range of the converter, the boost module is designed not to adjust the target output voltage and the target output phase angle; and a command module designed to: to determine an inverter command based on the target output voltage and the target output voltage phase angle; and to control the inverter based on the inverter command. [10] Method comprising: Determining a modulation index based on a measured DC bus voltage of an inverter and a target output voltage of the inverter; Determine, based on the modulation index, whether a target output voltage of an inverter lies in a linear space vector modulation range (linear SVPWM range); If the target output voltage of the inverter is outside the linear range: Determining an angle adjustment value based on the modulation index; and Adjusting either the target output voltage or a target output phase angle based on the angle adjustment value; and If the inverter's target output voltage is in the linear range, do not adjust the target output voltage or the target output phase angle. [11] The method of claim 10, wherein determining the angle adjustment value based on the modulation index comprises determining the angle adjustment value from a lookup table relating the angle adjustment value to the modulation index. [12] The method of claim 11, further comprising: generating the lookup table by varying the angle adjustment value for a plurality of different values ​​of the target output phase angle. [13] The method of claim 10, further comprising: Determining an inverter command based on the target output voltage and the target output voltage phase angle; and Control the inverter based on the inverter command. [14] The method of claim 13, wherein controlling the inverter based on the inverter command causes the inverter to output the target output voltage, and the target output voltage has a peak voltage equal to or greater than a peak voltage of an AC input.

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