Apparatus and method for controlling two-stage bi-directional AC-DC power converter

Abstract

A two-stage bidirectional AC-DC power converter with a controller includes a main control loop and an auxiliary control loop. The main control loop regulates the output of the DC-DC converter stage. The auxiliary control loop receives a converter signal that includes information about a ripple generated by the AC-DC converter stage on an external DC power source. The converter signal is band-pass filtered to isolate the ripple information, and loop compensation is applied to the filtered signal. And carrying out band-pass filtering on the compensated signal again to generate a ripple control signal. In the inverter mode, the ripple control signal is subtracted from the main control signal, thereby reducing the loop gain of the main control loop only at the ripple frequency. In the rectifier mode, the ripple control signal is added to the main control signal, thereby increasing the loop gain of the main control loop only at the ripple frequency.

Description

Technical Field

[0001] The present invention generally relates to a power conversion device and a control method for a switched power converter. Background Art

[0002] A bidirectional AC-DC power converter is typically formed by coupling multiple converter stages together. For example, an AC-DC switched converter stage can be coupled with a regulated DC-DC switched converter stage to form a two-stage bidirectional AC-DC power converter. The use of a bidirectional converter topology in each stage enables the two-stage AC-DC power converter to operate as an inverter or a rectifier.

[0003] Typically, it is very important to avoid applying ripple on the DC power supply side of the converter. Ripple is harmful to batteries or other DC power supply devices connected to the DC side of the power converter. The occurrence frequency of the ripple is usually twice the line frequency of the AC power supply, and the ripple appears as voltage ripple or current ripple on the DC side of the converter.

[0004] Some traditional solutions reduce the ripple by increasing the capacitance on the DC bus. This reduces the power density of the converter and limits the dynamic performance. Other solutions are designed to operate only in one direction, i.e., in the inverter mode or the rectifier mode, but not in both modes simultaneously. There are also some complex control strategies, but they are difficult to implement and increase the number of components.

[0005] Therefore, improved devices and methods are needed that can control the bidirectional power flow in a two-stage AC-DC power converter using a single simplified control scheme that reduces the number of components and the ripple on the DC power supply. Accordingly, it is desirable to provide methods and devices that solve at least some of the above problems. Summary of the Invention

[0006] The present invention relates to a device and a method for controlling a two-stage bidirectional AC-DC power converter. The disclosed embodiments use a single simplified control scheme that reduces the number of components and the ripple on the DC power supply to control the rectifier power flow and the inverter power flow in the two-stage bidirectional AC-DC power converter.

[0007] According to a first aspect, the above and other implementations and advantages are obtained by a device. The device includes: a bidirectional AC-DC switched converter stage configured to transfer power between an external AC power supply and a DC bus power supply; a bidirectional DC-DC switched converter stage configured to receive a converter control signal (x c ) and transfer power between the DC bus power supply and an external DC power supply, wherein the power is based on the converter control signal (x c)Transmission; a controller, the controller including a main controller and an auxiliary controller. The main controller is configured to: receive a first converter signal (s1) and a reference signal (V ref ); generate a converter error signal (e ref ) based on the first converter signal (s1) and the reference signal (V c ); generate a main control signal (x c ) by applying main compensation to the converter error signal (e m ). The auxiliary controller includes: a first band - pass filter configured to extract a ripple signal (r) based on a second converter signal (s2); auxiliary compensation configured to generate a ripple control signal (x r ) by applying the auxiliary compensation to the ripple signal (r); a second band - pass filter configured to generate an auxiliary control signal (x r ) based on the ripple control signal (x a ). The controller is configured to generate the converter control signal (x m ) by combining the main control signal (x a ) with the auxiliary control signal (x c ).

[0008] In a possible implementation, the first converter signal (s1) and the second converter signal (s2) include one or more of the voltage (V bus ) of the DC bus, the voltage (V DC ) of the external DC power supply, and the current (I DC ) of the external DC power supply. The above - mentioned signals can enable bidirectional power flow to be controlled by a single control scheme independent of the converter topology of the bidirectional DC - DC switched - converter stage.

[0009] In a possible implementation, the first band - pass filter and the second band - pass filter are configured to attenuate frequencies above and below a ripple frequency (f r ), where the ripple frequency (f r ) is twice the line frequency (f L ) of the external AC power supply. Limiting the frequencies included in the auxiliary control signal can enable the auxiliary control signal to be used to modify only the loop gain of the main controller at the ripple frequency, thus avoiding reducing the transient or dynamic behavior of the main control loop.

[0010] In a possible implementation, one or more of the main compensation and the auxiliary compensation include a proportional - integral compensation algorithm. The PI controller provides a stable controller design that is easy to understand, implement, and analyze.

[0011] In one possible implementation, the main compensation and the auxiliary compensation include the same control algorithm. The main controller and the auxiliary controller adopt the same control algorithm, which simplifies the tuning of the system.

[0012] In one possible implementation, the first band - pass filter includes a first plurality of band - pass filters, and the outputs generated by each of the first plurality of band - pass filters are added together to generate the ripple signal (r). The center frequency of each of the first plurality of band - pass filters is an integer multiple (n*2f L ) of twice the line frequency. The second band - pass filter includes a second plurality of band - pass filters, and the outputs generated by each of the second plurality of band - pass filters are added together to generate the auxiliary control signal (x a ). The center frequency of each of the second plurality of band - pass filters is the same as the center frequency of the corresponding one of the first plurality of band - pass filters. Using multiple harmonics in generating the ripple signal and the auxiliary control signal can better reduce the ripple when driving a non - linear AC load.

[0013] In one possible implementation, the device operates as an inverter; the first converter signal is the voltage (V bus ) of the DC bus; the second converter signal (s2) is the current (I DC ) of the external DC power supply; the main controller is configured to subtract the auxiliary control signal (x m ) from the main control signal (x a ). Using the current of the external DC power supply provides ripple information for the controller, and subtracting the auxiliary control signal from the main control signal reduces the loop gain of the main control loop only at the ripple frequency.

[0014] In one possible implementation, the device operates as a rectifier; the first converter signal (s1) is the voltage (V DC ) of the external DC power supply, the second converter signal (s2) is the voltage (V DC ) of the external DC power supply, and the main controller is configured to add the auxiliary control signal (x a ) to the main control signal (x m ). When operating as a rectifier, the voltage of the external DC power supply provides appropriate ripple information for the auxiliary controller, and adding the auxiliary control signal to the main control signal increases the loop gain of the main control loop only at the ripple frequency.

[0015] According to a second aspect, the above and other implementations and advantages are obtained by a method. The method is for controlling a power converter, where the power converter includes: a bidirectional AC-DC switched converter stage configured to transfer power between an external AC power supply and a DC bus power supply; a bidirectional DC-DC switched converter stage configured to receive a converter control signal (x c ) and transfer power between the DC bus power supply and an external DC power supply according to the converter control signal (x c ). The method includes: generating a converter error signal (e ref ) by comparing a first converter signal (s1) with a reference signal (V c ); generating a main control signal (x c ) by applying a main control algorithm to the converter error signal (e m ). The method includes: generating a ripple signal (r) by band-pass filtering a second converter signal (s2); generating a ripple control signal (x r ) by applying an auxiliary control algorithm to the ripple signal (r); generating an auxiliary control signal (x r ) by band-pass filtering the ripple control signal (x a ). The method includes: generating the converter control signal (x m ) by combining the main control signal (x a ) with the auxiliary control signal (x c ).

[0016] In a possible implementation, the first converter signal (s1) and the second converter signal (s2) include one or more of the voltage (V bus ) of the DC bus, the voltage (V DC ) of the external DC power supply, and the current (I DC ) of the external DC power supply. The selected signals above can control the bidirectional power flow through a single control scheme independent of the converter topology used in the bidirectional DC-DC switched converter stage.

[0017] In a possible implementation, the band-pass filtering includes: attenuating frequencies above and below a ripple frequency (f r ), where the ripple frequency (f r ) is twice the line frequency (f L ) of the external AC power supply. Limiting the frequencies included in the auxiliary control signal can enable the auxiliary control signal to be used to modify only the loop gain of the main controller at the ripple frequency, thereby avoiding changing the transient or dynamic behavior of the main control loop.

[0018] In one possible implementation, the band-pass filtering includes: attenuating frequencies greater than or less than a predetermined frequency range, where the predetermined frequency range is centered on the ripple frequency (f r ). Using a frequency range avoids ripple signal distortion that may occur when using a narrow passband.

[0019] In one possible implementation, one or more of the main control algorithm and the auxiliary control algorithm include a proportional-integral control algorithm. The PI controller provides a stable controller design that is easy to understand, implement, and analyze.

[0020] In one possible implementation, the main control algorithm and the auxiliary control algorithm include the same control algorithm. The main controller and the auxiliary controller adopt the same control algorithm, which simplifies the tuning of the system.

[0021] These and other aspects, implementations, and advantages of the exemplary embodiments will become apparent from the embodiments described herein when considered in conjunction with the accompanying drawings. However, it should be understood that these descriptions and drawings are for illustrative purposes only and should not be construed as limitations on the disclosed invention; any limitations on the present invention should be referred to the appended claims. Additional aspects and advantages of the present invention will be set forth in the following description, and some aspects and advantages will be apparent from the description, or may be learned by practicing the present invention. In addition, the various aspects and advantages of the present invention may be realized and obtained by means or combinations particularly pointed out in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In the following detailed description of the present invention, the present invention is explained in more detail with reference to the exemplary embodiments shown in the accompanying drawings, where like reference numerals represent like elements, and:

[0023] Figure 1 is a block diagram of an exemplary two-stage bidirectional AC-DC power converter incorporating aspects of the disclosed embodiments;

[0024] Figure 2 shows an exemplary controller configured to regulate the inverter operation of a two-stage bidirectional AC-DC switched power converter incorporating aspects of the disclosed embodiments;

[0025] Figure 3 shows an exemplary controller configured to regulate the rectifier operation of a two-stage bidirectional AC-DC switched power converter incorporating aspects of the disclosed embodiments;

[0026] Figure 4 shows an exemplary controller configured to reduce ripple in a power converter that exhibits non-linear load behavior incorporating aspects of the disclosed embodiments;

[0027] Figure 5 It is a flowchart of an exemplary method for controlling a two - stage bidirectional AC - DC power converter that combines aspects of the disclosed embodiments. Detailed implementation

[0028] Figure 1 It is a block diagram of an exemplary power conversion device 100 that combines aspects of the disclosed embodiments. Aspects of the disclosed embodiments use a single simplified control scheme that reduces the number of components and the ripple on the DC power supply to control the rectifier power flow and the inverter power flow in a two - stage bidirectional AC - DC power converter.

[0029] As Figure 1 shown in the example in, the device 100 includes a bidirectional AC - DC switch converter stage 102. The converter stage 102 is configured to transfer power between an external AC power supply 108 and a DC bus power supply 110. The bidirectional DC - DC switch converter stage 104 is configured to receive a converter control signal (xc) and transfer power between the DC bus power supply 110 and an external DC power supply 112 according to the converter control signal (xc).

[0030] The device 100 further includes a controller 106. The controller 106 includes a main controller 114 and an auxiliary controller 122. The main controller 114 is configured to: receive a first converter signal (s1) and a reference signal (Vref); generate a converter error signal (ec) according to the first converter signal (s1) and the reference signal (Vref); generate a main control signal (xm) by applying a main compensation (116) to the converter error signal (ec).

[0031] In one embodiment, as Figure 1 shown, the auxiliary controller 122 includes a first band - pass filter 130, and the first band - pass filter 130 is configured to generate a ripple signal (r) according to a second converter signal (s2). The auxiliary controller 122 further includes an auxiliary compensation 126, and the auxiliary compensation 126 is configured to generate a ripple control signal (xr) by applying the auxiliary compensation 126 to the ripple signal (r). A second band - pass filter 124 is configured to generate an auxiliary control signal (xa) according to the ripple control signal (xr). The controller 106 is configured to generate a converter control signal (xc) by combining the main control signal (xm) and the auxiliary control signal (xa).

[0032] In one embodiment, the two-stage bidirectional AC-DC switched power converter 150 in the apparatus 100 is operated by an improved controller 106. The controller 106 is configured to regulate the output of the converter 150 while reducing the ripple imposed on the DC power supply 112. These improvements and advantages are obtained in part by employing the improved controller 106, which includes a main controller 114 and an auxiliary controller 122, to provide a simplified control scheme capable of controlling bidirectional power flow while reducing the ripple on the external DC power supply 112 and reducing the total number of components.

[0033] In the exemplary apparatus 100, the two-stage bidirectional AC-DC switched power converter 150 includes: a bidirectional AC-DC switched converter stage 102 coupled between an external AC power supply 108 and a DC bus power supply 110, also referred to herein as the AC-DC converter stage 102; a bidirectional DC-DC switched converter stage 104 coupled between the DC bus power supply 110 and an external DC power supply 112, also referred to herein as the DC-DC converter stage 104. The DC-DC converter stage 104 receives a converter control signal x from the controller 106 c , and is used to regulate the power flowing between the DC bus power supply 110 and the external DC power supply 112, where the power is regulated according to the converter control signal x c . If desired, the DC-DC converter stage can be configured to maintain a substantially linear relationship between the power flowing through the DC-DC converter stage 104 and the magnitude of the converter control signal x c .

[0034] The external AC power supply 108 can be any suitable AC power supply, for example, the European power grid with a line frequency f of 50 Hertz (50 Hz) L , the North American power grid with a line frequency f of 60 Hertz (60 Hz) L , or, if desired, any other AC power supply with any suitable line frequency f L and voltage v ac .

[0035] The term "ripple" as used herein refers to the unwanted AC component superimposed on a DC signal. The main frequency component f of the ripple r is equal to twice the line frequency f of the external AC power supply 108 L . When the two-stage bidirectional AC-DC switched power converter 150 operates as an inverter, the ripple can be a ripple current on the DC power supply, and when the two-stage bidirectional AC-DC switched power converter 150 operates as a rectifier, the ripple can be a ripple voltage, and so on. The ripple can also appear on other signals, for example, on the signals within the controller 106.

[0036] Any suitable bidirectional AC-DC converter topology capable of bidirectional power transfer between an external AC power supply 108 and a DC bus power supply 110 can be advantageously used as the bidirectional AC-DC switch converter stage 102. For example, in the illustrated apparatus 100, the switch network 132 is included in the bidirectional AC-DC switch converter stage 102, and the bidirectional AC-DC switch converter stage 102 is configured to operate as an inverter or a rectifier to transfer electrical energy between the external AC power supply 108 and the DC bus power supply 110. In certain embodiments, semiconductor switching devices such as metal oxide semiconductor field effect transistors (MOSFETs), bipolar junction transistors (BJTs), diodes, or other suitable types of semiconductor switching devices are used to control the power flow within the bidirectional AC-DC switch converter stage 102.

[0037] Any suitable bidirectional DC-DC converter topology capable of bidirectional power transfer between a DC bus power supply 110 and an external DC power supply 112 can be advantageously used as the bidirectional DC-DC switch converter stage 104. For example, in the illustrated apparatus 100, the DC-DC converter stage 104 includes a first switch network 134 and a second switch network 138 coupled together through an energy storage network 136. The first switch network 134 is configured to transfer electrical energy between the DC bus power supply 110 and the energy storage network 136, and the second switch network 138 is configured to transfer electrical energy between the energy storage network 136 and the external DC power supply 112.

[0038] The first switch network 134 and the second switch network 138 can include any suitable arrangement of switching devices configured to transfer electrical energy to and from the energy storage network 136. The energy storage network 136 can include any suitable arrangement of energy storage devices, such as inductors and capacitors, configured to support power conversion between the DC bus power supply 110 and the external DC power supply 112. In certain embodiments, the energy storage network 136 can include a transformer, which can be configured to provide electrical isolation between the DC bus power supply 110 and the external DC power supply 112 if needed.

[0039] The modulator 140 is included in the DC-DC converter stage 104, where the modulator 140 is configured to receive a converter control signal x c and operate the first switch network 134 and the second switch network 138 to transfer electrical energy according to the received converter control signal x cPower is transferred between the DC bus power supply 110 and the external DC power supply 112. The modulator 140 operates the switch networks 134, 138 to provide a power flow corresponding to the converter control signal x c so that the power flow through the two-stage bidirectional AC-DC power converter 150 is regulated by the controller 106.

[0040] The power flow through the two-stage bidirectional AC-DC switched power converter 150 (more specifically, the power flowing through the DC-DC converter stage 104) is regulated by the controller 106, where the controller 106 is configured to receive one or more converter signals s1, s2 and generate a converter control signal x c . The two-stage bidirectional AC-DC switched power converter 150 is capable of transferring power in either direction between the external AC power supply 108 and the external DC power supply 112. When operating as an inverter, the two-stage bidirectional AC-DC switched power converter transfers power from the external DC power supply 112 to the external AC power supply 108, and when operating as a rectifier, the two-stage bidirectional AC-DC switched power converter 150 transfers power from the external AC power supply 108 to the external DC power supply.

[0041] The controller 106 includes a main controller 114 and an auxiliary controller 122. The main controller 114 is configured to receive a first converter signal s1 and generate a main control signal x m , where the main control signal x m is used to drive the output of the DC-DC converter stage 104 to a desired output value. The auxiliary controller 122 is configured to receive a second converter signal s2 and generate an auxiliary control signal x a , where the auxiliary control signal x a is configured to reduce the ripple on the external DC power supply 112.

[0042] The main controller 114 receives a first converter signal s1 representing the actual output of the DC-DC converter stage 104 and a reference signal V ref representing the desired output of the DC-DC converter stage 104. The main controller 114 generates a converter error signal e ref based on the first converter signal s1 and the reference signal V c . If desired, the error signal e c can be generated by subtracting the first converter signal s1 from the reference signal V ref to generate a converter error signal e c , where the converter error signal e c represents the error or difference between the actual converter output and the desired converter output.

[0043] The main control signal x mBy applying a main compensation 116 (also referred to as a main control algorithm 116) to the converter error signal e c to generate. As further discussed below, the main compensation 116 can include any suitable control algorithm, for example, a proportional plus integral (PI) type control algorithm, a PI control algorithm with gain adjustment, a proportional plus integral plus derivative (PID) control algorithm, or other suitable control algorithms.

[0044] The main control signal x m is adjusted by the main controller 114 to minimize the converter error signal e c , thereby maintaining the actual converter output at or near the desired output value indicated by the reference signal V ref . However, the external AC power supply 108 can cause ripples on the external DC power supply 112, where the ripple frequency f r is substantially twice the line frequency f L of the external AC power supply 108.

[0045] Some conventional controllers attempt to reduce such ripples by incorporating a larger bus capacitor C bus or by reducing the bandwidth of the main controller. Increasing the bus capacitor C bus increases the cost and reduces the power density of the converter. Using a large bus capacitor also reduces the bandwidth of the main control loop, resulting in a slow dynamic response of the DC bus voltage V bus to changes in the external AC power supply 108. To avoid these drawbacks, an auxiliary controller 122 configured to reduce ripples is included in the exemplary controller 106.

[0046] As detailed below, the auxiliary controller generates an auxiliary control signal x a , which is used to minimize the ripples on the external DC power supply 112. The auxiliary control signal x a is combined with the main control signal x m such that the loop gain of the main controller 114 is modified only near the ripple frequency f r .

[0047] The auxiliary controller 122 receives a second converter signal s2, where the second converter signal s2 includes information about the ripples on the external DC power supply 112. Examples of converter signals suitable for use as the second converter signal s2 include the current I DC of the external DC power supply 112 and the voltage V DC of the external DC power supply 112.

[0048] Within the auxiliary controller 122, a first bandpass filter 130 receives a second converter signal s2 and generates a ripple signal r based on the second converter signal s2. The first bandpass filter 130 is configured to pass a primary ripple frequency f r , and attenuate frequencies above and below the ripple frequency f r , thereby generating a ripple signal r corresponding to the primary frequency component of the ripple present on the external DC power supply 112.

[0049] As used herein, the term "bandpass filter" refers to a system component that attenuates frequency components of a signal outside a desired frequency range and passes frequency components within the desired frequency range without significant attenuation. The frequency range that is passed without significant attenuation is referred to herein as the pass band. Frequencies above and below the pass band are attenuated and effectively removed from the filtered signal. A bandpass filter can be described as having a center frequency, where the center frequency is the frequency of interest located at or near the center of the pass band of the bandpass filter.

[0050] A bandpass filter can be implemented using analog circuitry configured to operate on analog signals. Optionally, a bandpass filter can be implemented using digital filtering techniques or entirely within software executed by a processor and configured to operate on digitized signals.

[0051] A ripple control signal x r is generated by applying an auxiliary compensation 126 to the ripple signal r. In some embodiments, the auxiliary compensation 126 can add unwanted frequency components to the ripple control signal x r . For example, the integral term in a PI control algorithm can add a DC component or a low-frequency component, which may not be beneficial if these components are included in the auxiliary control signal x a . A second bandpass filter 124 is included in the auxiliary controller 122 to remove unwanted frequency components from the ripple control signal x r and produce a final auxiliary control signal x a . If desired, the first bandpass filter 130 can be configured to have a center frequency and pass band similar to or the same as that of the second bandpass filter 124. Optionally, the first bandpass filter 130 and the second bandpass filter 124 can be configured to have different pass bands.

[0052] The controller 106 generates a converter control signal x m based on a main control signal x a and the auxiliary control signal x c . In one embodiment, for example, when the converter operates as an inverter, the auxiliary control signal x aSubtracted from the main control signal x m Optionally, for example, when the converter operates as a rectifier, the auxiliary control signal x a is added to the main control signal x m .

[0053] Then, the converter control signal x c is applied to the DC-DC converter stage 104, where the modulator 140 regulates the power flow through the two-stage bidirectional AC-DC switched power converter 150 according to the converter control signal x c .

[0054] Figure 2 An exemplary controller 200 configured to regulate the inverter operation of a two-stage bidirectional AC-DC switched power converter incorporating aspects of the disclosed embodiments is shown. The exemplary controller 200 is suitable for use as the controller 106 described above and in conjunction with Figure 1 described, and is similar to the controller 106, where like reference numerals represent like elements.

[0055] For purposes of aiding understanding, diagrams 210, 212, 214, 216, 218, and 220 are provided to illustrate various signals within the controller 200. In each diagram, time increases to the right along the horizontal axis, and signal amplitude increases upward along the vertical axis. The purpose of diagrams 210, 212, 214, 216, 218, 220 is not to provide specific information about the signals, such as specific amplitudes or specific times, but only to provide an understanding of the general characteristics of each signal.

[0056] In the following discussion, the inverter mode operation of the exemplary controller 200 will be described in conjunction with the two-stage bidirectional AC-DC switched power converter 150 described above and shown in Figure 1 . Those skilled in the art will readily recognize that the exemplary controller 200 is not so limited and can be advantageously used to operate any suitable two-stage bidirectional AC-DC power converter.

[0057] The exemplary controller 200 includes: a main control loop as shown in bracket 206, configured to regulate the output of the DC-DC converter stage 104; and an auxiliary control loop as shown in bracket 208, configured to reduce the ripple on the external DC power supply 112.

[0058] When operating as an inverter, the output of the DC-DC converter stage 104 is the DC bus voltage V bus . Using the DC bus voltage V bus or a signal corresponding to the DC bus voltage V bus as the first converter signal s1 enables the main control loop 206 to regulate the DC bus voltage V according to the reference signal V ref ​bus .

[0059] Ripple on the external DC power supply 112 can be accurately measured by the external DC current I DC . Using the external DC current I DC or the signal corresponding to the external DC current I DC as the second converter signal s2 can enable the auxiliary control loop 208 to reduce the ripple on the external DC power supply 112.

[0060] The external AC power supply 108 generates a ripple component on the DC bus voltage V bus , resulting in a ripple on the DC voltage in the first converter signal s1 corresponding to the DC bus voltage V bus , as shown in Chart 220. Subtracting the first control signal from the DC reference signal V ref generates a converter error signal e c , and applying the main loop compensation 116 to the converter error signal e c generates a main control signal x that generates a ripple on the DC component m , as shown in Chart 218.

[0061] The second converter control signal s2 corresponding to the external DC current I DC includes a ripple component generated on the DC value, as shown in Chart 210. The auxiliary control loop 208 applies the first band-pass filter 130 to the second converter signal s2 to generate a ripple signal r without a DC component, as shown in Chart 212.

[0062] For the sake of understanding, the auxiliary control loop 208 includes a summing node 224 used in the feedback control loop. Ripple is unwanted, so the reference signal of the auxiliary control loop is set to zero 0. Subtracting any signal from zero generates the inverted version of the signal, so the output of the summing node is just the reciprocal of the ripple signal r. To maintain consistency of notation, the second converter signal s2 is shown as the reciprocal of the external DC current I DC , and the output of the summing node becomes the non-inverted ripple signal r.

[0063] Applying the auxiliary compensation 126 to the ripple signal r generates a ripple control signal x r . The application of the auxiliary compensation 126 can generate unwanted frequency components in the ripple control signal x r . For example, a PI controller can generate a DC component or other low-frequency components that do not exist in the input signal of the PI controller. The second band-pass filter 124 is applied to the ripple control signal x r to generate an auxiliary control signal x that only includes the ripple component and has no DC component a , as shown in Chart 214.

[0064] In some embodiments, the primary compensation 116 includes a primary control algorithm 202 and a primary gain K m , and the secondary compensation 126 includes a secondary control algorithm and a secondary gain K a . By using the same control algorithm, e.g., a PI control algorithm, for both the primary control algorithm 202 and the secondary control algorithm 204, the controller 200 can be conveniently tuned. When the primary control algorithm 202 and the secondary control algorithm 204 are the same, the controller 200 can be tuned by adjusting the primary gain K m and the secondary gain K a .

[0065] Subtracting the secondary control signal x m from the primary control signal x a results in a substantially ripple-free converter control signal x r , as shown in plot 216. Subtracting the secondary control signal x m from the primary control signal x a reduces the loop gain of the primary control loop 206 only at the ripple frequency f r without affecting the transient or dynamic response of the DC bus voltage V bus .

[0066] Figure 3 Illustrated is an exemplary controller 300 configured to regulate the rectifier operation of a two-stage bidirectional AC-DC switched power converter incorporating aspects of the disclosed embodiments. The exemplary controller 300 is suitable for use as the controller 106 described above and in connection with Figure 1 and is similar to the above-described exemplary controller 200, where like reference numerals represent like elements.

[0067] For purposes of illustration, plots 302, 304, 306, 308, and 310 are provided to illustrate various signals within the controller 300. In each plot, time increases to the right along the horizontal axis and signal amplitude increases upward along the vertical axis. The plots 302, 304, 306, 308, and 310 are not intended to provide specific information about the signals, e.g., specific amplitudes or specific times, but rather to provide an understanding of the general characteristics of each signal.

[0068] In the following discussion, the rectifier mode operation of the exemplary controller 300 will be described in connection with the above description and the two-stage bidirectional AC-DC switched power converter 150 shown in Figure 1 . Those skilled in the art will readily recognize that the exemplary controller 300 is not so limited and can be advantageously used to operate any suitable two-stage bidirectional AC-DC power converter.

[0069] When operating as a rectifier, power flows from an external AC power supply 108 to an external DC power supply 112 through a two-stage bidirectional AC-DC switched power converter 150, and the output of the DC-DC converter stage 104 is the external DC voltage V DC . Using the external DC voltage V DC or a signal corresponding to the external DC voltage V DC as the first converter signal s1 enables the main control loop 206 to regulate the external DC voltage V ref in accordance with the reference signal V DC .

[0070] The second converter signal s2 is used to provide ripple information to the auxiliary controller 208. As can be seen from the diagram 302, during rectifier operation, the external DC voltage V DC includes a ripple voltage on the DC component. Using the external DC voltage V DC or a signal corresponding to the external DC voltage V DC as the second converter signal s2 enables the auxiliary control loop 208 to reduce the ripple on the external DC power supply 112.

[0071] The main control loop 208 receives the second converter signal s2 and subtracts the second converter signal s2 from the reference signal V ref to generate a converter error signal e c . Applying the main compensation 116 to the converter error signal e c results in a main control signal x m . Unless an overly large bus capacitor C bus is used, the converter error signal e c will include a ripple component that may not be completely removed from the main control signal x m by the main compensation 116, as shown in the diagram 304.

[0072] The second converter control signal s2 corresponding to the external DC voltage V DC includes a ripple component on the DC value, as shown in the diagram 302.

[0073] As described above, the auxiliary control loop 208 applies the first band-pass filter 130 to the second converter signal s2 to generate a ripple signal r without a DC component, as shown in the diagram 308. Applying the auxiliary compensation 126 to the ripple signal r results in a ripple control signal x r . The second band-pass filter 124 is applied to the ripple control signal x r to generate an auxiliary control signal x a that includes only the ripple component and no DC component, as shown in the diagram 310.

[0074] Applying the auxiliary control signal xa Add 320 to the main control signal x m to produce a converter control signal x that includes amplified ripple components r , as shown in Chart 306. Add the auxiliary control signal x a Add 320 to the main control signal x m to increase the loop gain of the main control loop 206 only at the ripple frequency f r to better suppress the ripple.

[0075] When operating as a rectifier, the bidirectional AC-DC switch converter stage 102 regulates the DC bus power supply 110, and the external DC voltage V DC is controlled by the DC-DC switch converter stage 104, which is regulated by the main control loop 206. In a conventional controller, a PIR type controller is used to eliminate the ripple in the output. However, this type of controller is not suitable for inverter operation, and thus when applied to a bidirectional converter (e.g., the exemplary two-stage bidirectional AC-DC switch power converter 150), it greatly increases the complexity.

[0076] Figure 4 An exemplary controller 400 configured to reduce the ripple in a power converter that exhibits non-linear load behavior in combination with various aspects of the disclosed embodiments is shown. The exemplary controller 400 is suitable for controlling a bidirectional AC-DC switch power converter, e.g., the bidirectional AC-DC switch power converter 150 described above and in combination with Figure 1 described above. The exemplary controller 400 includes elements similar to the exemplary controller 106, where like reference numerals represent like elements.

[0077] When operating as an inverter, the AC output current i ac of the bidirectional AC-DC switch power converter 150 can be non-linear, thereby generating a non-sinusoidal ripple on the external DC current I DC . To better eliminate the non-sinusoidal ripple, multiple band-pass filters can be included in the auxiliary controller to isolate the additional higher harmonics of the ripple, thereby more closely tracking the non-sinusoidal characteristics of the ripple generated on the external DC current I DC .

[0078] The main control loop 114 remains as described above, where a first converter signal s1 corresponding to the DC bus voltage V bus is compared with a reference voltage V ref to produce a converter error signal e c , and the main compensation 116 is applied to the converter error signal e c to produce a main control signal x m. Due to the non - sinusoidal characteristics of the load, non - sinusoidal ripples can be generated on the external DC current I drawn from the external DC power supply 112. DC .

[0079] To better reduce the non - sinusoidal ripples generated on the external DC current I DC , the auxiliary controller 416 in the exemplary controller 400 is used to generate a non - sinusoidal auxiliary control signal x a . The first band - pass filter 430 employs a first plurality of band - pass filters 410, 412... 414 to more closely track the non - sinusoidal ripples, where the center frequency of each band - pass filter in the first plurality of band - pass filters 410, 412... 414 is set to a different integer multiple f r of the ripple frequency, 2f r ... nf r . When represented using the line frequency f L , the center frequency of each band - pass filter in the first plurality of band - pass filters 410, 412... 414 is set to a different integer multiple 2f L of twice the line frequency, 4f L ... 2nf L .

[0080] The outputs of each band - pass filter in the first plurality of band - pass filters 404, 406... 408 are added together 418 to form a ripple signal r. Applying an auxiliary compensation 402 to the ripple signal r generates a ripple control signal x r . The auxiliary compensation can be any desired type of control algorithm, e.g., a PI algorithm, a PID algorithm, or other suitable control algorithms for reducing the ripples in the external DC current I DC .

[0081] The second band - pass filter 424 is used to remove unwanted frequency components from the ripple control signal x r and generate an auxiliary control signal x a . Similar to the first band - pass filter 430, the second band - pass filter 424 includes a second plurality of band - pass filters 404, 406... 408, where the center frequency of each band - pass filter in the second plurality of band - pass filters 404, 406... 408 is set to a different integer multiple f r of the ripple frequency, 2f r ... nf r . The outputs of each band - pass filter in the second plurality of band - pass filters 404, 406... 408 are added together 420 to produce the auxiliary control signal x a .

[0082] Then, the auxiliary control signal x m is subtracted 422 from the main control signal xa to generate a converter control signal x c . As described above, subtracting the auxiliary control signal x m from the main control signal x a will reduce the loop gain of the main controller 114 only at the frequencies selected by the first plurality of band-pass filters 430 and the second plurality of band-pass filters 424, without affecting the transient or dynamic response of the DC bus power supply 110.

[0083] Referring now to Figure 5 , a flowchart of an exemplary method 500 for controlling a two-stage bidirectional AC-DC power converter that combines aspects of the disclosed embodiments can be seen. Method 500 is applicable to controlling a two-stage bidirectional AC-DC power converter, for example, the two-stage bidirectional AC-DC switched power converter 150 described above and in connection with Figure 1 . The converter includes: a bidirectional AC-DC switched converter stage 102 configured to transfer power between an external AC power supply 108 and a DC bus power supply 110; and a bidirectional DC-DC switched converter stage 104 configured to receive a converter control signal x c and transfer power between the DC bus power supply 110 and an external DC power supply 112. The bidirectional DC-DC switched converter stage 104 is configured to transfer power in accordance with the converter control signal x c .

[0084] Method 500 includes: generating 502 a converter error signal e ref by comparing a first converter signal s1 with a reference signal V c . For example, the above comparison can be achieved by subtracting the first converter signal s1 from the reference signal V ref . The first converter signal s1 corresponds to the output of the bidirectional DC-DC switched converter stage 104.

[0085] When the two-stage bidirectional AC-DC switched power converter 150 operates as an inverter, a suitable first converter signal s1 can be the voltage V bus of the DC bus power supply 110, or a signal corresponding to the voltage V bus of the DC bus power supply 110. When the two-stage bidirectional AC-DC switched power converter 150 operates as an inverter, the first converter signal s1 can be suitably selected as the voltage of the external DC power supply 112, or a signal corresponding to the voltage of the external DC power supply 112.

[0086] By applying a main control algorithm to the converter error signal e c , generating 504 a main control signal x mAny suitable control algorithm may be used as the primary control algorithm, for example, a PI control algorithm, a gain-adjusted PI control algorithm, a PID control algorithm, or other suitable control algorithms as desired.

[0087] The ripple signal r is generated 506 by bandpass filtering the second converter signal s2, wherein the second converter signal s2 is selected to provide ripple information suitable for use in removing ripple from the external DC power source 112. For example, when the two-stage bidirectional AC-DC switching power converter 150 operates as an inverter, the second converter signal s2 may be the current I DC , or when the two-stage bidirectional AC-DC switching power converter 150 operates as a rectifier, the second converter signal s2 may be the voltage V of the external DC power source 112 DC .

[0088] The bandpass filter is configured to attenuate the second converter signal s2 above or below the ripple frequency f r The ripple frequency is the line frequency f of the external AC power source 108. L Optionally, the bandpass filter can be configured to attenuate frequencies greater than or less than a predetermined frequency range, wherein the predetermined frequency range is based on the ripple frequency f r As the center.

[0089] By applying the auxiliary control algorithm to the ripple signal r, a ripple control signal x is generated 508 r The auxiliary control algorithm may be any suitable control algorithm, for example, a PI algorithm, a gain-adjusted PI algorithm, a PID algorithm, or other suitable control algorithm as desired. In certain embodiments, it may be advantageous to employ the same control algorithm as the primary control algorithm and the auxiliary control algorithm. Alternatively, the primary control algorithm may be a different control algorithm than that used as the auxiliary control algorithm.

[0090] By controlling the ripple control signal x r Bandpass filtering is performed to remove any unwanted frequency components that may be introduced by the auxiliary control algorithm, generating 510 an auxiliary control signal x a .

[0091] By passing the main control signal x m With auxiliary control signal x a Combination, generate 512 converter control signal x c Then, the converter control signal x c It can be used to regulate the bidirectional DC-DC switching converter stage 104 .

[0092] When operating as an inverter, a converter control signal x is generated 512 cincluding: subtracting the auxiliary control signal x from the main control signal x m to reduce the ripple on the external DC power supply 112 without adversely affecting the transient or dynamic response of the DC bus power supply 110. When operating as a rectifier, generating the 512 converter control signal x a including: adding the auxiliary control signal x c to the main control signal x a to improve the ability of the controller to remove the ripple on the external DC power supply 112. m

[0093] Accordingly, although the basic novel features of the invention have been shown, described, and pointed out as applied to the exemplary embodiments of the invention, it should be understood that various omissions, substitutions, and changes in the form and details of the devices and methods shown may be made by those skilled in the art without departing from the spirit and scope of the invention. In addition, all combinations of elements that perform substantially the same function in substantially the same way to achieve the same result are intended to be within the scope of the invention. Moreover, it should be recognized that structures and / or elements shown and / or described in connection with any form or embodiment of the disclosed invention may be incorporated as a general item of design choice into any other form or embodiment disclosed or described or suggested. Accordingly, the intention is limited only to the scope as set forth in the appended claims herein.

Claims

1. An apparatus (100), characterized in that, The device (100) includes: A bidirectional AC-DC switch converter stage (102) configured to transfer power between an external AC power supply (108) and a DC bus power supply (110); Bidirectional DC-DC switching converter stage (104), configured to receive a converter control signal (x c ), and transfer power between the DC bus power supply (110) and an external DC power supply (112) in accordance with the converter control signal (x c ); and A controller (106), where the controller (106) includes a main controller (114) and an auxiliary controller (122), wherein the main controller (114) is configured to: Receive a first converter signal (s1) and a reference signal (V ref ); Generate a converter error signal (e ref ) based on the first converter signal (s1) and the reference signal (V c ); and By applying a main compensation (116) to the converter error signal (e c ), a main control signal (x m ) is generated, and wherein the auxiliary controller (122) includes: A first band-pass filter (130) configured to generate a ripple signal (r) based on a second converter signal (s2); Auxiliary compensation (126), configured to generate a ripple control signal (x) by applying the auxiliary compensation (126) to the ripple signal (r) r ); and A second band-pass filter (124), configured to generate an auxiliary control signal (x r ) according to the ripple control signal (x a ), Wherein, the controller (106) is configured to generate the converter control signal (x m ) by combining the main control signal (x a ) with the auxiliary control signal (x c ).

2. The device (100) according to claim 1, characterized in that, The first converter signal (s1) and the second converter signal (s2) include one or more of the voltage (V bus ) of the DC bus, the voltage (V DC ) of the external DC power supply, and the current (I DC ) of the external DC power supply.

3. The device (100) according to any one of the preceding claims, characterized in that, The first band-pass filter (130) and the second band-pass filter (124) are configured to attenuate frequencies above and below a ripple frequency (f r ), where the ripple frequency (f r ) is twice the line frequency (f L ) of the external AC power supply (108).

4. The device (100) according to any one of the preceding claims, characterized in that, One or more of the main compensation (116) and the auxiliary compensation (126) includes a proportional-integral compensation algorithm.

5. The device (100) according to any one of the above claims, characterized in that, The main compensation (116) and the auxiliary compensation (126) include the same control algorithm.

6. The device (100) according to any one of the above claims, characterized in that The first band-pass filter (430) includes a first plurality of band-pass filters (410, 412... 414), and the outputs generated by each of the first plurality of band-pass filters (410, 412... 414) are added together to generate the ripple signal (r). The center frequency of each of the first plurality of band-pass filters is an integer multiple (n*2f L ) of twice the line frequency; and The second band-pass filter (424) includes a second plurality of band-pass filters (404, 406... 408), and outputs generated by each of the second plurality of band-pass filters (404, 406... 408) are added together to generate the auxiliary control signal (x a ), and the center frequency of each of the second plurality of band-pass filters (404, 406... 408) is the same as the center frequency of a corresponding one of the first plurality of band-pass filters (410, 412... 414).

7. The device (100) according to any one of the above claims, characterized in that The device (100) operates as an inverter; The first converter signal (s1) is the voltage (V bus ) of the DC bus; The second converter signal (s2) is the current (I DC ) of the external DC power supply; and The master controller (114) is configured to subtract the auxiliary control signal (x m ) from the master control signal (x a ).

8. The device (100) according to any one of the above claims, characterized in that The device (100) operates as a rectifier; The first converter signal (s1) is the voltage (V DC ) of the external DC power supply; The second converter signal (s2) is the voltage (V DC ) of the external DC power supply; and The main controller (114) is configured to add the auxiliary control signal (x a ) to the main control signal (x m ).

9. A method (500) for controlling a power converter, characterized in that, The power converter includes: a bidirectional AC-DC switched converter stage (102) configured to transfer power between an external AC power supply (108) and a DC bus power supply (110); and a bidirectional DC-DC switched converter stage (104) configured to receive a converter control signal (x c ), and transfer power between the DC bus power supply (110) and an external DC power supply (112) according to the converter control signal (x c ), the method including: By comparing a first converter signal (s1) with a reference signal (V ref ), a converter error signal (e c ) is generated (502); By applying a main control algorithm to the converter error signal (e c ), a main control signal (x m ) is generated (504); By band-pass filtering the second converter signal (s2), a ripple signal (r) is generated (506); By applying an auxiliary control algorithm to the ripple signal (r), a ripple control signal (x r ) is generated (508); By performing band-pass filtering on the ripple control signal (x r ), an auxiliary control signal (x a ) is generated; and By combining the main control signal (x m ) with the auxiliary control signal (x a ), the converter control signal (x c ) is generated (512).

10. The method (500) according to claim 9, characterized in that, The first converter signal (s1) and the second converter signal (s2) include one or more of the voltage (V bus ) of the DC bus, the voltage (V DC ) of the external DC power supply, and the current (I DC ) of the external DC power supply.

11. The method (500) according to claim 9 or 10, characterized in that, The band-pass filtering includes: frequencies above and below a ripple attenuation frequency (f r ), where the ripple frequency (f r ) is twice the line frequency (f L ) of the external AC power supply (108).

12. The method (500) according to any one of claims 9 to 11 above, characterized in that, The bandpass filtering includes: attenuating frequencies greater than or less than a predetermined frequency range, wherein the predetermined frequency range is centered on the ripple frequency (f r ).

13. The method (500) according to any one of claims 9 to 11 above, characterized in that, One or more of the main control algorithm and the auxiliary control algorithm includes a proportional-integral control algorithm.

14. The method (500) according to any one of the preceding claims 9 to 12, characterized in that The main control algorithm and the auxiliary control algorithm include the same control algorithm.

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