Boost module of power converter

Abstract

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

Description

Technical Field

[0001] The present disclosure relates to a boost module for a power converter. Background Art

[0002] Electrical equipment (such as variable speed drives, adjustable speed drives, or uninterruptible power supplies) can be connected to an alternating current (AC) high power distribution system (such as the power grid). Electrical equipment drives, supplies power, and / or controls machine or non-machine type loads. Electrical equipment includes power grids that convert AC power to direct-current (DC) power and vice versa. Summary of the invention

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

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

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

[0006] In some embodiments, if the target output voltage is in the boost region, the boost system is configured to determine whether the target output voltage is in the first boost region or in the second boost region. In addition, in some embodiments, if the target output voltage is in the first boost region, the 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 boost region, the boost system is configured to adjust the associated target output voltage phase angle based on the second adjustment value.

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

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

[0009] On the other hand, the control system of the inverter includes: a boost module configured to: access the target output voltage and the target output phase angle of the inverter; determine the modulation index based on the DC bus voltage of the inverter and the target output voltage of the inverter; determine whether the target output voltage is in the linear region of the inverter or the boost region of the inverter based on the modulation index; if the target output voltage is in the boost region: determine the adjustment value based on the modulation index; and adjust one or more of the target output voltage and the target output voltage phase angle based on the adjustment value; and if the target output voltage is in the linear region 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] On the other hand, a method includes: determining a modulation index based on a measured inverter DC bus voltage and a target output voltage of the inverter; determining whether the target output voltage of the inverter is in a space vector pulse width modulation (SVPWM) linear region based on the modulation index; if the target output voltage of the inverter is outside the linear region: determining an angle adjustment value based on the modulation index; and adjusting one of the target output voltage and the target output phase angle based on the angle adjustment value; and if the target output voltage of the inverter is in the linear region, not adjusting the target output voltage or the target output phase angle.

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

[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 further 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 greater than or equal to the peak voltage of the AC input.

[0014] Embodiments of any technology described herein may include devices, apparatus, systems, control systems, machine executable instructions, and / or methods. Details of one or more embodiments are set forth in the accompanying drawings and the following description. Other features will be apparent from the specification and drawings, as well as from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a block diagram of an example of a system including a power converter.

[0016] Figure 2 is a schematic diagram of an example of a system including a power converter.

[0017] Figure 3 is a block diagram of an example control scheme.

[0018] Figure 4 An example of an operating hexagon involving an inverter.

[0019] Figure 5 is a block diagram of an example of a boost module.

[0020] Fig. 6A It can be Figure 5 An example flow chart of a boost process implemented by a boost module.

[0021] Figure 6B Another example of an operating hexagon involving an inverter.

[0022] Figure 7 An example flow chart of a process 700A for generating a lookup table and an example flow chart of a process 700B for obtaining a value of an adjustment parameter according to the lookup table are shown.

[0023] Figure 8 is an example flow chart of a process for generating inverter gate commands.

[0024] Figure 9-12 An example of simulated data is shown. DETAILED DESCRIPTION

[0025] refer to Figure 1, which shows a block diagram of a system 100. The system 100 includes an electrical device or power converter 110 that is electrically connected to an alternating current (AC) power distribution network 101 and a load 102. The electrical device 110 generates a drive signal 104 for the load 102 based on power 105 from the distribution network 101. For example, the electrical device 110 can be a variable speed drive (VSD) or an adjustable speed drive (ASD), and the load 102 can be a machine type load, such as, for example, an induction motor, an induction motor, or a synchronous permanent magnet machine, which operates at a speed and torque determined by the drive signal 104. In some embodiments, the electrical device 110 is an uninterruptable power supply (UPS) that provides power to a non-machine type load 102 (e.g., a lighting system).

[0026] The electrical device 110 includes a rectifier 117, a direct current (DC) link 118, and an inverter 119. The rectifier 117 includes an electronic switch (e.g., a diode) for converting AC power into DC power and storing it in the DC link 118. The inverter 119 includes a controllable switch (e.g., a transistor) that is controlled to modulate the energy stored in the DC link 118 into the drive signal 104 based on a space vector pulse width modulation (SVPWM) technique.

[0027] The filter system 116 is connected in series with the rectifier 117 between the input node 114 of the device 110 and the distribution network 101. During operation of the electrical device 110, a voltage drop may occur across the filter system 116. As the demand of the load 102 increases, the voltage drop may become significant, thereby reducing the voltage of the drive signal 104 and, therefore, the voltage available to the load 102. As a result, the operation of the load 102 and / or the operation of a system driven by and / or dependent on the operation of the load 102 may be affected.

[0028] Furthermore, although using SVPWM techniques to control inverter 119 results in a drive signal 104 having a voltage that is approximately 15% higher than a drive signal produced using sinusoidal PWM to control inverter 119, SVPWM may also present challenges in certain circumstances. For example, as the demands of load 102 increase, the voltage drop across filter system 116 and electrical device 110 may also increase, thereby reducing the voltage available to load 102. Furthermore, even if filter system 116 is removed, conventional SVPWM may not be able to generate sufficient output voltage to maintain operation of load 102 when load 102 is operated in a manner that increases the current draw (e.g., operating load 102 in a manner that exceeds one or more of its rated parameters).

[0029] On the other hand, as discussed in more detail below, the control system 130 implements a boost module 180 that provides dynamic voltage compensation, thereby allowing more efficient use of the inverter 119 and improving the performance of the SVPWM in an efficient manner. The boost module 180 is a signal processing-based approach that does not involve additional hardware and can be used to retrofit existing systems.

[0030] In addition, the 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 amplitude of the output voltage waveform is less than the reference voltage or target voltage, and the voltage available to the load 102 may be reduced. To address this challenge and allow the inverter 119 to generate sufficient voltage throughout its entire operating range, the control system 130 includes a boost module 180. The boost module 180 is computationally efficient because it uses one variable (adjustment value (α), discussed further below) to account for all conditions in the nonlinear region. The boost module 180 produces a unified solution that effectively transitions from the linear region operation of the inverter 119 to the nonlinear region operation of the inverter 219, and then to the six-step operation.

[0031] The power distribution network 101 may be, for example, a multiphase power grid that provides power to industrial, commercial, and / or residential customers. The AC power distribution network 101 distributes AC power having a fundamental frequency of, for example, 50 or 60 Hertz (Hz). The operating voltage of the distribution network 101 may be up to, for example, 690 V. The network 101 may include, for example, one or more transmission lines, distribution lines, distribution or substation transformers, power cables, and / or any other mechanism for transmitting power.

[0032] The electrical device 110 is enclosed in a housing or enclosure 111. The housing 111 is a three-dimensional object made of a strong and durable material that protects the electrical device 110. An input node 114 is accessible from the outside 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 port (not shown) that is accessible from the outside of the housing 111. The load 102 is connected to the electrical device 110 at the output port.

[0033] Figure 2is a schematic diagram of a system 200. The system 200 includes an electrical device or power converter 210 connected to a three-phase AC 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 based on a control scheme 306 to generate the drive signal 204. The control scheme 306 is based on SVPWM technology and includes a boost module 380 that provides dynamic voltage compensation when the inverter 219 operates outside its linear operating region (e.g., when the voltage demand of the load 202 increases).

[0034] Before discussing the control scheme 306 and the boost module 380 in more detail, an overview of the system 200 is provided.

[0035] exist Figure 2 In the example of , the load 202 is a three-phase motor 202, such as, for example, an induction motor or a permanent magnet synchronous machine. The motor 202 includes a stator 209 (which is fixed in space) and a rotor 208, which 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 motors can be used in the system 200.

[0036] The power distribution network 201 distributes AC power having a fundamental frequency of, for example, 50 or 60 Hertz (Hz). The operating voltage of the distribution network 201 can be up to 690V. The distribution network 201 can include, for example, one or more transmission lines, distribution lines, power cables, and / or any other mechanism for transmitting power. The distribution network 201 includes three phases, referred to as a, b, and c.

[0037] The electrical device 210 comprises 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 through a respective filtering system 216a, 216b, 216c. Each filtering system 216a, 216b, 216c may be an inductor.

[0038] The electrical device 210 includes a rectifier 217, a DC link 218, and an inverter 219. The rectifier 217 is a three-phase six-pulse bridge including six electronic switches. Figure 2 In the example of FIG. 1 , the six electronic switches are diodes D1 to D6. Each diode D1 to D6 includes a cathode and an anode and is associated with a forward bias voltage. When the voltage at the anode is greater than the voltage at the cathode by at least the bias voltage, each diode D1 to D6 allows current to flow in the forward direction (from the anode to the cathode). When the voltage difference between the anode and the cathode is less than the forward bias voltage, the diode does not conduct current in the forward direction.

[0039] 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, and input node 214c is electrically connected to the anode of diode D5 and the cathode of diode D2. Diodes D1-D6 rectify input currents ia, ib, ic into direct currents id.

[0040] 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, and when the rectified current id flows out of the rectifier 217, the capacitor stores electrical energy, and when the rectified current id does not flow out of the rectifier 217, the capacitor releases the stored electrical energy.

[0041] The inverter 219 converts the DC power stored in the capacitor network C into a three-phase AC drive signal 204 provided to the load 202. The inverter 219 includes an electronic switch SW1-electronic switch SW6 network controlled by the control system 230 to generate the drive signal 204. Each switch SW1-SW6 can be, for example, a power transistor. The three-phase drive signal 204 has phase components 204u, 204v, 204w, each phase component provided to one of the three phases of the load 202.

[0042] The system 200 also includes a sensor system 238 that measures and / or estimates properties or parameters of the drive signal 204 and / or the motor 202. For example, the sensor system 238 may include a current sensor that measures the amount of current drawn in each phase of the motor 202, and / or a voltage sensor that measures the voltage of each phase component 204u, 204v, 204w of the drive signal 204. The sensor system 238 may also include a sensor that measures the angular position of the rotor 208 of the motor 202 and / or the angular velocity of the rotor 208. In some embodiments, the control system 230 estimates the angular position and / or angular velocity of the rotor 208 based on sensorless techniques using data from the sensor system 238 (rather than directly measured position data).

[0043] The control system 230 controls the switching pattern of the switches SW1-SW6 to generate a drive signal 204 having specific characteristics (eg, amplitude, frequency, and / or phase). The control system 230 implements a SVPWM control scheme 306 including a boost module 380, both of which refer to Figure 3 A discussion was held.

[0044] 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 processor of the module 232 can be any type of electronic processor, which 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).

[0045] Electronic memory 234 may be any type of electronic memory capable of storing data and instructions in the form of a computer program or software, and electronic memory 234 may include volatile and / or non-volatile components. Electronic memory 234 is coupled to processing module 232 so that processing module 232 can access or read data in electronic memory 234 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 related to system 200. For example, electronic memory 234 may store information related to motor 202 or inverter 219.

[0046] In addition, electronic memory 234 may store executable instructions for implementing control scheme 306 and boost module 380. Electronic memory 234 may also store data and / or information for control scheme 306 and / or boost module 380. For example, electronic memory 234 may store thresholds and / or boundary values ​​associated with the operating mode of inverter 219. Electronic memory 234 also stores lookup tables 285 and 286, which will be combined with Fig. 6A , Figure 6B and Figure 7 The lookup tables 285 and 286 are used in the control scheme 306 and / or the boost module 380 .

[0047] The I / O interface 236 can be any interface that allows a human operator and / or an autonomous process to interact with the control system 230. The I / O interface 236 can include, for example, a display (e.g., a liquid crystal display (LCD)), a keyboard, audio input and / or output (e.g., a speaker and / or a microphone), a visual output that supplements or replaces the display (e.g., a light, a light emitting diode (LED)), a serial or parallel port, a Universal Serial Bus (USB) connection, and / or any type of network interface, such as, for example, Ethernet. The I / O interface 236 can also allow for non-physical contact communication through, for example, IEEE802.11, Bluetooth, or near-field communication (NFC) connections. For example, the control system 230 can be operated, configured, modified, or updated through the I / O interface 236.

[0048] The I / O interface 236 may also allow the control system 230 to communicate with components in the system 200 and with systems external and remote to the system 200. For example, the I / O interface 236 may control a switch or switching network (not shown) or circuit breaker within the system 200, allowing the electrical device 210 to be disconnected from the distribution network 201. In another example, the I / O interface 236 may include a communication interface that allows 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 physically contacting the control system 230. For example, the remote station may be a computer-based workstation, a smart phone, a tablet, or a laptop computer connected to the control system 230 via a service protocol, or a remote control connected to the control system 230 via a radio frequency signal.

[0049] Figure 3 3 is a block diagram of a control scheme 306 including a boost module 380 that generates an inverter gate command 351 for controlling switches S1 to S6 of an inverter 219. In response to the control of the inverter gate command 351, the inverter 219 generates a three-phase drive signal 204.

[0050] The control scheme 306 includes a comparator 359 that compares the target angular velocity (ω*) of the motor 202 with the observed angular velocity (ωo) of the rotor 208 and provides the difference (Δω) to the 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 derivative block 358. The observed angular position (θo) of the rotor 208 is output from an angular position block 367, which determines the observed angular position (θo) based on a position sensor in the sensor system 238 or by using a sensorless angular position estimation technique. The derivative block 358 determines the observed angular velocity (ωo) by calculating the rate of change of the angular position (θo) over a period of time.

[0051] 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 the modulation block 356, which implements the Clarke transformation to transform the three-phase current (ia, ib, ic) into two orthogonal current components: a component iα along the α axis and a component iβ along the β axis (orthogonal to the α axis). The Clark 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) onto a two-dimensional stationary coordinate system defined by the α axis and the β axis. The Clark transformation is shown in formula (1):

[0052] Formula (1),

[0053] Where, ia, ib, ic are the instantaneous currents in the stator windings 209a, 209b, 209c, i αβ is a vector including a component along the α axis (365) and a component along the β axis (366). Vector 365 and vector 366 are provided to a modulation block 364 which implements a Park transform. The Park transform rotates the stationary α, β axes with a frequency ω.

[0054] Park transformation is shown in formula (2):

[0055] Formula (2),

[0056] Among them, i dq is a vector that includes a component along the d-axis (ido, or observed d-axis current) and a component along the q-axis (iqo, or observed q-axis current), and θ is the observed angular position (θo) of the rotor 208 of the motor 202 .

[0057] The speed controller 352 generates a torque command Te*, which is provided to the 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 comparator 357 compares the d-axis current command id* with the observed d-axis current (ido) to determine the difference (Δid) between id* and ido*, and provides the difference (Δid) to the d-axis current controller 354d. The comparator 361 compares the q-axis current command iq* with the observed q-axis current (iqo) to determine the difference (Δiq) between iq* and iqo, and provides the difference (Δiq) to the q-axis current controller 354q.

[0058] The d-axis current controller 354d is a proportional-integral (PI) controller having a predetermined gain constant Kd. The q-axis current controller 354q is a PI controller having a predetermined gain constant Kq. The d-axis current controller 354d determines the d-axis current error (Δi d ) minimizes the d-axis voltage command ud*. The q-axis current controller 354q determines the q-axis current error (Δi q ) minimizes the q-axis voltage command uq*.

[0059] The d-axis voltage command ud* and the q-axis voltage command uq* are provided to a modulation block 355 that implements an inverse Park transform. The inverse Park transform projects the d-axis and q-axis voltage commands (ud*, uq*) onto a stationary α, β reference frame. The outputs of the modulation block 355 are uα* and uβ*, which are the voltage components to be applied to the stator 209 in the stationary α, β reference frame.

[0060] The voltage commands uα*, uβ* are provided to the boost module 380. The boost module 380 implements SVPWM-based overmodulation control to generate the inverter gate command 351 according to the voltage commands uα*, uβ*.

[0061] The inverter 219 includes controllable switches S1 to S6, each of which can be controlled to be in an on state or an off state. For example, each switch S1 and S6 can be turned on or off by controlling the voltage at the switch gate. The state of switches S1 to S6 is controlled and changes over time, and its switching mode is defined by the inverter gate command 351. Switches S1, S3 and S5 are upper switches, and switches S4, S6 and S2 are lower switches. Switches S1, S3 and S5 have eight valid switch configurations or state combinations. The switch state is represented by space vectors U1 to U8. The switch states U1 to U8 of the upper switches S1, S3, S5 are shown in Table 1:

[0062] Table 1.

[0063] Space Vector 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

[0064] At any given time, the state of each lower switch S4 , S6 , S2 is opposite to the state of the corresponding upper switch S1 , S3 , S5 , so that there are eight SVPWM switching configurations or combinations for the inverter 219 .

[0065] Also refer to Figure 4 , six non-zero vectors (U1 to U6) define a hexagon 439 and six sectors (1 to 6) in a rectilinear coordinate system (Re, Im). The angle between any two adjacent non-zero vectors (U1 to U6) is 60 degrees (°). Two zero vectors (U7 and U8) are located at the origin. Hexagon 439 represents the operating limits of inverter 219. Switching states U1 to U8 are combined to approximate voltage vectors of arbitrary amplitude and angle within hexagon 439. For example, a desired inverter output voltage having an amplitude represented by vector Vref and a phase angle θref that places the voltage vector in sector 1 is achieved by utilizing a switching sequence that uses two adjacent switching states (U1 and U2 in this example) for a specified time period and a zero vector (U7 or U8) for the remaining time periods.

[0066] The voltage commands uα* and uβ* input to the boost module 380 define Figure 4 The vector Vref at the phase angle (θref) in the Re, Im coordinate system is shown. The voltage vector (Vref) and angle (θref) are called the target or reference voltage and angle. The length of the vector Vref is characterized by the modulation index (M), which is determined by formula (3):

[0067] Formula (3),

[0068] Where M is the modulation index and Vref is the amplitude of the reference or target voltage ( Figure 4 ), and Vdc is the voltage measured on the DC link 218.

[0069] Figure 4Also included is a first circle 441 (dashed line) inscribed in the hexagon 439 and a second circle 443 (dotted line) having a radius greater than the first circle 441. The first circle 441 defines a linear operating region 448 of the inverter 219. A reference voltage whose modulation index (M) is less than the radius of the first circle 441 is located within the linear operating region 448 of the inverter 219. In the linear operating region 448, the inverter 219 acts as a linear amplifier when controlled with SVPWM. For a reference voltage (Vref) whose modulation index (M) is located 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 can correspond to a modulation index (M) of 0.906, for example. In this example, the target voltage associated with a modulation index less than 0.906 is located in the linear operating region 448 of the inverter 219.

[0070] The reference voltage whose modulation index is greater than the radius of the first circle 441 is not in the linear operation region 448 of the inverter 219. For example, the reference voltage whose modulation index (M) is in the ring between the first circle 441 and the second circle 443 or outside the second circle 443 is outside the linear operation region 448 of the inverter 219. The ring portion between the first circle 441 and the second circle 443 is the first nonlinear region 445 (or the first boost region 445), and the region within the hexagon outside the second circle 443 is the second nonlinear region 447 (or the second boost region 447). The radius of the second circle 443 may correspond to a modulation index (M) of 0.951.

[0071] Conventional SVPWM techniques cannot command the inverter 219 in a manner such that the inverter 219 can generate sufficient voltage to meet the reference voltage Vref outside the linear operating region 448. Outside the linear operating region 448, the output voltage waveform of the inverter 219 is distorted and the amplitude of the output voltage waveform is less than the reference or target voltage (Vref). To address this challenge and allow the inverter 219 to generate sufficient voltage throughout its operating range, the control system 230 includes a boost module 380.

[0072] Figure 5380 is a block diagram of a boost module 380. The 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 a reference or target voltage Vref, a reference or target phase angle θref, and a voltage (VDC) on the DC link 218. The command module 382 determines an inverter gate command 351 based on an SVPWM technique that uses a voltage command V*, a phase angle θ*, S (SVPWM sector determined by the phase angle θ*), and a voltage (VDC) of the DC link 218 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 one phase of the inverter 219.

[0073] Correction module 381 combines Fig. 6A and Figure 6B The command module 382 will be combined with Figure 8 for a more detailed discussion.

[0074] refer to Fig. 6A , a flow chart of process 600 is shown. Process 600 is an example of a boost process that can be implemented by correction module 381. Process 600 can be implemented as executable instructions stored on electronic memory 234 and executed by electronic processing module 232. Process 600 can be implemented as software and can be programmed into a control system in an existing power converter. In addition, process 600 can be implemented as a control system or controller that is installed in an existing power converter as a software update or as part of a firmware update.

[0075] Process 600 begins and a modulation index (M) is determined using equation (3) (610). To determine the modulation index (M) using equation (3), the voltage of the DC link 218 (VDC) is the measured value of the voltage on the DC link 218, and Vref is the value obtained from the modulation block 355 ( Figure 3 ) is the reference voltage related to the output voltage command (uα*, uβ*).

[0076] The modulation index (M) is compared to the linear operation region boundary to determine whether the inverter 219 can accurately generate the reference voltage (Vref) in the linear operation region 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) when operating in the linear operation region 448. The process 600 proceeds to (620), and the reference voltage (Vref) and the reference phase angle (θref) are output from 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 operation region boundary, no modification or adjustment is made to the reference voltage (Vref) or the reference phase angle (θref).

[0077] If it is determined at (610) that the modulation index (M) is not within the linear operation region 448, the process 600 proceeds to (625) to determine whether the inverter 219 is operated in the first non-linear region 445 or the second non-linear region 447 to generate 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 will operate in the first non-linear region 445 to generate the reference voltage Vref. If the modulation index (M) has a value greater than the radius of the second circle 443, the inverter 219 will operate in the second non-linear region 447 to generate the reference voltage Vref.

[0078] If the inverter 219 operates in the first non-linear region 445 or the second non-linear region 447 to generate the reference voltage Vref, the 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. Figure 6B A graphical example of the adjustment value (α) is shown. Figure 6B In the example of FIG. 4 , the reference voltage (Vref) has a modulation index (M) in the first nonlinear region 445. Circle 649 (long dashed style) is the ideal trajectory set by the reference voltage Vref. However, trajectory 649 exceeds the operating hexagon 439 of the inverter 219 at some points. The adjustment value (α) sets an adjustment trajectory 687 (bold line) that achieves the same fundamental voltage as trajectory 649 and does not exceed the operating hexagon 439 of the inverter 219.

[0079] The first lookup table 285 associates the adjustment value (α) in the first non-linear region 445 with the modulation index (M), and the second lookup table 286 associates the adjustment value (α) in the second non-linear region 447 with the modulation index (M).

[0080] return Fig. 6A , if the inverter 219 operates in the first non-linear region 445, an adjustment value (α) (627) of the modulation index (M) determined in (610) is obtained from the first lookup table 285. The first lookup table 285 includes an adjustment value (α) for each of a plurality of modulation index values ​​(M) in the first non-linear region 445. An example of the first lookup table is shown in Table 2:

[0081] Table 2.

[0082] α (radians) Modulation index (M) 0 0.95142615 0.00068569 0.95136157 0.03205707 0.95117309 0.04274276 0.95045491

[0083] The modulation index (M) determined in (610) is provided to the lookup table 285, and the adjustment value (α) corresponding to the modulation index (M) is returned as an output. If the modulation index (M) determined in (610) is not included in the lookup table 285, the adjustment value (α) is determined by interpolating between the adjustment values ​​of other modulation indices (M) included in the lookup table 285. In other embodiments, one or more functions may be derived from multiple values ​​of the adjustment value (α) in the lookup table 285 and used to estimate the adjustment values ​​(α) of other modulation indices. The development of the lookup table 285 will refer to Figure 7 Have a discussion.

[0084] 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:

[0085] Formula (4),

[0086] Formula (5),

[0087] Wherein, in formula (4), V* is the adjusted voltage command, VDC is the voltage measured on the DC link 218, and α is the adjustment value obtained in (627). In formula (5), θ* is the adjusted phase angle, θref is the reference phase angle, and mod is the modulus operation. The adjusted voltage command (V*) and the adjusted phase angle (θ*) determined in formulas (4) and (5) are the outputs (620) of the correction module 381.

[0088] Returning to (625), if the inverter 219 is to operate in the second non-linear 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 non-linear region 447. An example of the second lookup table 286 is shown in Table 3, where the adjustment value (α) is in the left column and the corresponding modulation index (MI) value is in the right column:

[0089] Table 3.

[0090]

[0091] 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 the modulation index (M) is returned as an 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).

[0092] The adjustment value (α) is used to determine the adjusted voltage command (V*) and phase angle (θ*) (635). The voltage command adjustment for the second non-linear region 447 is shown in equation (6):

[0093] Formula (6),

[0094] Where V* is the adjusted voltage command and VDC is the voltage on the DC link 218. The adjusted reference phase angle (θ*) is determined according to one of equations (7), (8), (9), depending on the value of the adjustment value (α) determined in (632).

[0095] Formula (7),

[0096] Formula (8),

[0097] Formula (9),

[0098] in

[0099] Formula (10).

[0100] When the value of (α) is greater than or equal to When , use formula (7). Equivalent ( Greater than or equal to the amount ( -α), use equation (8). Otherwise use equation (9). The adjusted voltage command (V*) and phase angle (θ*) are the outputs (620) of the correction module 381.

[0101] In addition to outputting the voltage command (V*) and the phase angle (θ*), the correction module 381 can also output the SVPWM sector (S) related to the phase angle (θ*). Figure 4 As shown, and 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°; sector 6: 270°<θ*≤360°.

[0102] Figure 7 is a flow chart of a process 700A for creating a lookup table relating an adjustment parameter (α) to a modulation index (M). Figure 7 Also included is a flow chart of process 700B for obtaining the 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 can be performed before process 600 to generate lookup table 285 and lookup table 286 before process 600 begins. Other embodiments are also possible. For example, process 700A can be performed together with process 600. For example, process 700A can be called at (627) and / or (632) to obtain the value of the control parameter (α) without having to create lookup table 285 and / or lookup table 286 before starting process 600. Process 700B is performed after process 700A generates the lookup table.

[0103] The voltage command (V*) is expressed as:

[0104] Formula (11),

[0105] It can also be expressed as shown in formula (12):

[0106]

[0107] Formula (12).

[0108] When the inverter 219 operates in the first non-linear region 445:

[0109] Formula (13),

[0110] Formula (14),

[0111] Formula (15),

[0112] as well as

[0113] Formula (16).

[0114] When the inverter 219 is in the second non-linear region 447:

[0115] Formula (17),

[0116] Formula (18),

[0117] Where θ' = h(θ-α), h is defined as shown in formula (10),

[0118] Formula (19),

[0119] as well as

[0120] Formula (20).

[0121] To prepare the first lookup table 285, the adjustment value (α) is set to a specific value (710). The adjustment value (α) can be set to a specific value randomly or intentionally. A voltage command (V*) is determined for a specific value of (α) using equation (12) and equations (13) to (16) (720). A modulation index (M) is determined using equation (3), where V* in (720) is used as the value of Vref (730). The modulation index (M) is associated with the specific value used for (α). The modulation index (M) is stored as an entry in the first lookup table 285 in association with the specific value used for (α) (740). If more entries are to be added to the first lookup table (745), the process 700A returns to (710) and repeats (710) to (740) until the lookup table 285 is completed (745). Any criteria may be used to determine whether the first lookup table 285 is complete. For example, the number of entries of first lookup table 285 may be a predetermined number of entries, and first lookup table 285 is determined to be complete when that number of entries have been calculated and entered into lookup table 285. If lookup table 285 is complete (245), process 700A outputs lookup table 285 by, for example, storing the lookup table on electronic storage 234.

[0122] 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 the modulation index (M) value in the first non-linear region 445 is used as an input (755) to the first lookup table 285. An adjustment value (α) corresponding to the modulation index (M) is returned as an output (760). Process 700B can be called at (627) to obtain the adjustment value for the first non-linear region 445.

[0123] A second lookup table 286 is also generated using process 700 A, which associates the adjustment value (α) with the modulation index (M) in the second nonlinear region 447, except that the voltage command (V*) is determined for a specific value of (α) using equation (12) and equations (17) to (20). After the voltage command (V*) is determined for the specific value of (α), the modulation index (M) is determined using equation (3). The determined modulation index (M) is associated with the specific value of (α). Entries of the second lookup table 286 are generated by repeatedly changing (α) and determining the modulation index (M) associated with each value of (α), and associatively storing the values ​​of (α) and their corresponding modulation index (M) until the second lookup table 286 is complete.

[0124] The process 700B is used to obtain a value of (α) for a particular modulation index (M) in the second non-linear region 447 .

[0125] Figure 8 Flow diagram of process 800 , which is implemented by command module 382 to generate inverter gate commands 351 using the output of correction module 381 .

[0126] The variables (d1, d2) are determined based on the voltage command (V*) and the phase angle (θ*) output by the correction module 381 (810). The variables d1 and d2 are the calculated dwell time ratios of each effective voltage vector used for voltage synthesis within one switching cycle in the SVPWM. The sum of d1 and d2 (d1+d2) should not be greater than 1 so that the inverter 219 operates within the hexagon 439 that defines the operating limits of the inverter 219. If the sum of d1 and d2 is greater than 1, the scaling adjustment is performed using the process 800.

[0127] The variables d1 and d2 are determined as follows:

[0128] Formula (21),

[0129] Formula (22),

[0130] Where V* is the voltage command (V*) from the correction module 381, θ* is the phase angle from the correction module 381, and VDC is the voltage on 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 limits of the inverter. If the sum of d1 and d2 is greater than the threshold, the values ​​of variables d1 and d2 are scaled (820) as follows:

[0131] Formula (23),

[0132] Formula (24).

[0133] The value of d1 is set to d1', and the value of d2 is set to d2'.

[0134] If the sum of d1 and d2 does not exceed the threshold, the values ​​of variables d1 and d2 are not adjusted.

[0135] The inverter gate command 351 is determined based on the variables d1 and d2 and the sector (S) of the voltage command (V*) (825). The inverter gate command 351 defines the switching pattern of each phase of the inverter 219 (CMP1, CMP2, CMP3). The inverter gate command 351 is determined using one of the equations (25) to (31), where the appropriate equation is selected based on the sector (S) of the voltage command (V*).

[0136] For a voltage command (V*) of 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.

[0137] For the voltage command (V*) of S=2, formula (26) determines the inverter gate instruction 351 as follows: CMP1: (1+d2-d1)*TB, CMP2: (1-d1-d2)*TB, CMP3: (1+d1+d2)*TB.

[0138] For the voltage command (V*) of S=3, formula (27) determines the inverter gate instruction 351 as follows: CMP1: (1+d1+d2)*TB, CMP2: (1-d1-d2)*TB, CMP3: (1+d1-d2)*TB.

[0139] For the voltage command (V*) of S=4, formula (28) determines the inverter gate instruction 351 as follows: CMP1: (1+d1+d2)*TB, CMP2: (1+d2-d1)*TB, CMP3: (1-d1-d2)*TB.

[0140] For the voltage command (V*) of S=5, formula (29) determines the inverter gate instruction 351 as follows: CMP1: (1+d1-d2)*TB, CMP2: (1+d1+d2)*TB, CMP3: (1-d1-d2)*TB.

[0141] For the voltage command (V*) of S=6, formula (30) determines the inverter gate instruction 351 as follows: CMP1: (1-d1-d2)*TB, CMP2: (1+d1+d2)*TB, CMP3: (1+d2-d1)*TB.

[0142] If the sector (S) is unknown, equation (31) determines the inverter gate command as follows: CMP1 = CMP2 = CMP3 = 0*TB = 0.

[0143] In equations (25) to (31), TB is the value of the timer base period divided by 2. The timer base period is the timer counter value set for a specific switching frequency of switches S1 to S6.

[0144] Fig. 9 and Fig.10 Simulation data for a system using conventional SVPWM techniques without the boost module 380 is shown. Fig.11 and Fig.12 Figure 3 shows simulation data for the same system using a boost module 380. The system simulated is a system with Figure 2 The power converter of the system shown in the figure has a similar structure. The input voltage is 342V, the frequency is 50Hz, the AC inductor of 700μH is connected in series with the rectifier, and the load is a motor with a torque of 86 Newton meters (Nm) and a modulation index (M) of 1. Therefore, the inverter does not operate in the linear operation region in the simulation.

[0145] Fig. 9 The line-to-line output voltage (in volts) for each phase is shown as a function of time, with a maximum of approximately 338V (thus less than the input voltage). In addition, the output voltage ( Fig. 9 ) is seriously distorted. Fig.10 The output reference phase angle (in radians) is shown versus time. Fig. 9 and Fig.10 have the same timeline and display the same time period. Fig. 9 and Fig.10 The data shown were simulated without using the boost module 380 .

[0146] Fig.11 The change of three-phase voltage output over time when using the boost module 380 is shown. Fig.12 The variation of the output reference phase angle over time when the boost module 380 is used is shown. Fig.11 and Fig.12 have the same timeline and display the same time period. Fig.11 As shown, when using the boost module 380, the peak line voltage output is about 353V, which is higher than the input voltage (342V in this example). Therefore, the boost module 380 is able to increase the output voltage so that the system can provide sufficient output voltage even when the modulation index (M) is 1 (the inverter is not in the linear region). In addition, although the output voltage waveform ( Fig.11 ) is not pure sinusoidal, but the output voltage distortion is less than the output waveform produced when the boost module 380 is not used, and reaches a maximum value in the six-step operation without PWM switching events.

[0147] These and other implementations are within the scope of the following claims.

Claims

1. A power converter, comprising: Energy storage equipment; an inverter electrically coupled to the energy storage device; as well as A boost system configured to: determining a modulation index based on a DC voltage of the energy storage device and a target output voltage of the inverter; as well as determining whether the target output voltage is in a boost region based on the modulation index; If the target output voltage is in the boost region: determining an adjustment value based on the modulation index; and adjusting one or more of the target output voltage and a related target output voltage phase angle based on the adjustment value.

2. The power converter according to claim 1, wherein the boost system is configured as: determining an inverter gate command based on the target output voltage and the associated target output voltage phase angle; and The inverter gate command is provided to the inverter.

3. The power converter according to claim 1, wherein: If the target output voltage is within the boost region, the boost system is configured to determine whether the target output voltage is within one of a first boost region and a second boost region.

4. The power converter according to claim 3, wherein: If the target output voltage is in the first boost region, the boost system is configured to adjust the target output voltage based on the adjustment value; as well as If the target output voltage is in the second boost region, the 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 as a function of the modulation index. 6 . The power converter of claim 5 , wherein the boost system is configured to determine the adjustment value according to 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 according to claim 7, further comprising a filter system electrically connected to the energy storage device, the filter system being configured to be electrically connected to an AC power source, and wherein: The boost system is configured to determine an inverter gate command based on the target output voltage and the associated target output voltage phase angle; and The inverter gate command is provided to the inverter to control the inverter to generate the target output voltage at the target output voltage phase angle, and a peak voltage of the target output voltage is equal to or greater than a peak voltage of an AC power source.

9. A control system for an inverter, the control system comprising: The boost module is configured as: Obtaining a target output voltage and a target output voltage phase angle of the inverter; determining a modulation index based on a DC bus voltage of an inverter and the target output voltage of the inverter; determining whether the target output voltage is in a linear region of the inverter or a boost region of the inverter based on the modulation index; If the target output voltage is in the boost region: determining an adjustment value based on the modulation index; and adjusting one or more of the target output voltage and the target output voltage phase angle based on the adjustment value; as well as If the target output voltage is in the linear region of the inverter, the boost module is configured not to adjust the target output voltage and the target output voltage phase angle; as well as The command module is configured to: determining an inverter command based on the target output voltage and the target output voltage phase angle; as well as The inverter is controlled based on the inverter command.

10. A method comprising: determining a modulation index based on a measured DC bus voltage of the inverter and a target output voltage of the inverter; determining whether a target output voltage of the inverter is in a space vector pulse width modulation linear region based on the modulation index; If the target output voltage of the inverter is outside the linear region: determining an angle adjustment value based on the modulation index; as well as adjusting one of the target output voltage and the target output voltage phase angle based on the angle adjustment value; as well as If the target output voltage of the inverter is in the linear region, the target output voltage or the target output voltage phase angle is not adjusted.

11. The method of claim 10, wherein determining the angle adjustment value based on the modulation index comprises: The angle adjustment value is determined from a lookup table that relates angle adjustment values ​​to modulation indices.

12. The method according to claim 11, further comprising: The lookup table is generated by varying the angle adjustment value for a plurality of different values ​​of the target output voltage phase angle.

13. The method according to claim 10, further comprising: determining an inverter command based on the target output voltage and the target output voltage phase angle; as well as The inverter is controlled based on the inverter command. 14 . The method of claim 13 , wherein the inverter is controlled based on the inverter command so that the inverter outputs 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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