Power conversion system, power conversion system control method, and controller
Patent Information
- Application Number
- PCT/CN2026/075521
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-11-21
- Filing Date
- 2026-01-28
- Publication Date
- 2026-08-27
Smart Images
Figure CN2026075521_27082026_PF_FP_ABST
Abstract
Description
Power conversion system, control method and controller for power conversion system
[0001] This disclosure claims priority to Chinese patent applications filed on February 20, 2025, with application number 202510192306X, entitled "Power Conversion System and Control Method for Power Conversion System"; and filed on November 21, 2025, with application number 202511724924.0, entitled "Power Conversion System, Control Method and Controller", the entire contents of which are incorporated herein by reference. Technical Field
[0002] This disclosure relates to the field of power electronics technology, and in particular to a power conversion system, a control method for the power conversion system, and a controller. Background Technology
[0003] In power conversion systems, AC-DC converter circuits are typically used to convert alternating current (AC) to direct current (DC). Single-stage AC-DC converter circuits offer advantages over traditional two-stage topologies, including fewer components and higher efficiency. They can directly convert AC to DC or vice versa.
[0004] However, since the AC power of a single-stage AC-DC converter circuit varies with the sinusoidal phase of the power grid, if there is no voltage source on the DC side, the DC voltage will fluctuate significantly with the AC power, which will cause the DC voltage to exceed the normal operating voltage range of the DC-DC converter circuit, thus preventing the DC-DC converter circuit from working properly. Summary of the Invention
[0005] The following is an overview of the detailed description of this disclosure. This overview is not intended to limit the scope of the claims.
[0006] In a first aspect, embodiments of this disclosure provide a power conversion system, including: a single-stage AC-DC conversion circuit and a controller;
[0007] The DC side of the single-stage ACDC converter circuit is configured to connect the capacitor and the DC-DC converter circuit;
[0008] The controller is configured to determine the DC-side output power of a single-stage AC-CDC converter circuit;
[0009] The controller is also configured to control the average output voltage of the DC side of the single-stage ACDC converter circuit within the range of the average output voltage, wherein the range of the average output voltage is determined based on the output power and the upper and lower limits of the input voltage of the DCDC converter circuit.
[0010] In some embodiments, the DC side of the single-stage ACDC converter circuit is further configured to be connected to at least one of a first voltage source and a first DC load via the DCDC converter circuit.
[0011] In some embodiments, the DC side of the single-stage ACDC converter circuit is further configured to be connected to a second voltage source via a switching network, and the switching network is in an open state; wherein, when the switching network is in an open state, the second voltage source can stabilize the voltage on the DC side of the single-stage ACDC converter circuit.
[0012] In some embodiments, the controller is configured to control the average output voltage on the DC side of the single-stage AC-DC converter circuit to be within the range of the average output voltage, specifically:
[0013] The controller is configured to determine the median of the average output voltage within the range of the average output voltage; and,
[0014] The controller is also configured to control the average value of the DC-side output voltage of the single-stage ACCDC converter circuit to be equal to the median of the average output voltage.
[0015] In some embodiments, the controller is configured to control the average output voltage on the DC side of the single-stage AC-DC converter circuit to be within the range of the average output voltage, specifically:
[0016] The controller is configured to determine the target average output voltage corresponding to the highest conversion efficiency of the single-stage AC-CDC converter within the average output voltage range; and,
[0017] The controller is also configured to control the average output voltage on the DC side of the single-stage ACCDC converter circuit to be equal to the target average output voltage.
[0018] In some embodiments, the output power includes the maximum output power on the DC side of the single-stage ACCDC converter circuit, or the output power includes the current output power on the DC side of the single-stage ACCDC converter circuit.
[0019] In some embodiments, the average output voltage range is determined based on the DC-side voltage fluctuation range of the single-stage ACDC converter circuit, as well as the upper and lower limits of the input voltage of the ACDC converter circuit; the DC-side voltage fluctuation range is determined based on the ripple power of the capacitor and the capacitance value of the capacitor, with the average output voltage as an unknown; the ripple power of the capacitor is determined based on the output power and the AC angular frequency of the AC side of the single-stage ACDC converter circuit.
[0020] In some embodiments, the controller is configured to, when it is determined that a second voltage source is not connected to the DC side of the single-stage ACDC converter circuit, determine an average output voltage range based on the output power and the upper and lower limits of the input voltage of the DCDC converter circuit, and, if the average output voltage range does not exist, provide an alarm and reduce the output power of the DC side of the single-stage ACDC converter circuit.
[0021] In a second aspect, embodiments of this disclosure provide a control method for a power conversion system, the power conversion system including a single-stage ACCDC conversion circuit, wherein the DC side of the single-stage ACCDC conversion circuit is configured to connect a capacitor and a DCCDC conversion circuit.
[0022] Control methods include:
[0023] Determine the DC-side output power of a single-stage AC-DC converter circuit;
[0024] The average output voltage of the DC side of the control single-stage ACDC converter circuit is within the range of the average output voltage, wherein the range of the average output voltage is determined based on the output power and the upper and lower limits of the input voltage of the DCDC converter circuit.
[0025] In some embodiments, controlling the average value of the DC-side output voltage of a single-stage ACDC converter circuit to be within the range of the average output voltage is specifically as follows:
[0026] Determine the median of the average output voltage within the range of the average output voltage; and,
[0027] The average value of the DC-side output voltage of a single-stage AC-DC converter circuit is equal to the median of the average output voltage.
[0028] In some embodiments, controlling the average value of the DC-side output voltage of a single-stage ACDC converter circuit to be within the range of the average output voltage is specifically as follows:
[0029] Determine the target average output voltage corresponding to the highest conversion efficiency of the single-stage AC-CDC converter circuit within the range of average output voltage; and...
[0030] The average value of the DC-side output voltage of the control single-stage AC-DC converter circuit is equal to the average value of the target output voltage.
[0031] In some embodiments, the output power includes the maximum output power on the DC side of the single-stage ACCDC converter circuit, or the output power includes the current output power on the DC side of the single-stage ACCDC converter circuit.
[0032] In some embodiments, the step of determining the average range of the output voltage based on the output power and the upper and lower limits of the input voltage of the DC-DC converter circuit includes:
[0033] The capacitor's ripple power is determined based on the output power and the AC angular frequency on the AC side of the single-stage AC-DC converter circuit.
[0034] Based on the ripple power of the capacitor and the capacitance value, the range of DC-side voltage fluctuation with the average output voltage as the unknown is determined.
[0035] The average range of the output voltage is determined based on the DC-side voltage fluctuation range, as well as the upper and lower limits of the input voltage of the DC-DC converter circuit.
[0036] In some embodiments, if the average output voltage range is not available, at least one of the following is performed: issuing an alarm and reducing the output power on the DC side of the single-stage AC-DC converter circuit.
[0037] Thirdly, embodiments of this disclosure provide a controller, including a memory and a processor, wherein computer program instructions are stored in the memory, and the processor executes the control method of any one of the second aspects when processing the program instructions.
[0038] To make the above-mentioned objects, features and advantages of this disclosure more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings.
[0039] Brief description of the attached figures
[0040] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0041] Figure 1 is a schematic diagram of a power conversion system provided in an embodiment of this disclosure;
[0042] Figure 2 is a schematic diagram of a single-stage AC-DC conversion circuit provided in an embodiment of this disclosure;
[0043] Figure 3 is a schematic diagram of another single-stage AC-DC conversion circuit provided in an embodiment of this disclosure;
[0044] Figure 4 is a schematic diagram of another single-stage AC-DC conversion circuit provided in the embodiments of this disclosure;
[0045] Figure 5 is a schematic diagram of another single-stage AC-DC conversion circuit provided in an embodiment of this disclosure;
[0046] Figure 6 is a schematic diagram of the power when the AC current changes in phase with the AC voltage according to an embodiment of this disclosure;
[0047] Figure 7 is a schematic diagram of the DC-side voltage waveform when the DC side is not connected to the first voltage source according to an embodiment of this disclosure; and...
[0048] Figure 8 is a flowchart illustrating the control method of the power conversion system provided in an embodiment of this disclosure. Embodiments of the present invention
[0049] In the following description, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. As will be appreciated by those skilled in the art, the described embodiments can be modified in various ways without departing from the concept or scope of the present disclosure. Therefore, the drawings and description are to be considered exemplary in nature and not restrictive. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concepts of the present disclosure.
[0050] The accompanying drawings illustrate various structural schematics according to embodiments of the present disclosure. These drawings are not to scale, and some details have been enlarged for clarity, while others may be omitted. The shapes of the various structures and devices shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design alternatives according to actual needs. The following related technologies are optional solutions and can be arbitrarily combined with the technical solutions of the embodiments of the present disclosure, all of which fall within the protection scope of the embodiments of the present disclosure.
[0051] The power conversion system provided in this disclosure is not specifically limited to any particular application scenario. It can be applied to any scenario including a single-stage AC-DC conversion circuit, two voltage sources, and a DC load. The first voltage source and the second voltage source can be energy storage voltage sources, such as batteries.
[0052] The power conversion system will now be described in detail with reference to the accompanying drawings. Figure 1 is a schematic diagram of a power conversion system provided by an embodiment of the present disclosure. As shown in Figure 1, the power conversion system provided by the present disclosure includes: a single-stage AC-DC conversion circuit and a controller (not shown in the figure).
[0053] In this single-stage AC-CDC converter circuit, the DC side is configured to connect a capacitor and the DC-CDC converter circuit. For example, the AC side of the single-stage AC-CDC converter circuit is configured to connect the live wire L and the neutral wire N of the AC mains.
[0054] The single-stage AC-CDC converter circuit is an isolated converter circuit, including a primary-side converter circuit, a transformer, and a secondary-side converter circuit. The input terminal of the primary-side converter circuit is configured to connect to AC power, the output terminal of the primary-side converter circuit is configured to connect to the primary winding of the transformer, the secondary winding of the transformer is configured to connect to the secondary-side converter circuit, and the output terminal of the secondary-side converter circuit outputs DC power, configured to supply power to a DC load. This disclosure does not specifically limit the specific topology of the single-stage AC-CDC converter circuit; it can be a unidirectional or bidirectional converter circuit. Several implementation methods of the single-stage AC-CDC converter circuit are described below with reference to the accompanying drawings.
[0055] Referring to Figure 2, this figure is a schematic diagram of a single-stage AC-DC conversion circuit provided in an embodiment of this disclosure.
[0056] The primary-side converter circuit comprises two bridge arms. The upper half of the first bridge arm includes series-connected switches Q2 and Q1, and the lower half includes series-connected switches Q5 and Q6. The upper half of the second bridge arm includes series-connected switches Q3 and Q4, and the lower half includes series-connected switches Q8 and Q7. The primary-side converter circuit converts AC power at mains frequency into high-frequency AC power, which is then transferred to the secondary-side converter circuit via transformer Tr. The primary winding of the transformer is connected to an impedance network Zo, and the secondary winding is connected to an impedance network Z1. The secondary-side converter circuit is a rectifier converter circuit configured to output rectified DC power.
[0057] Referring to Figure 3, this figure is a schematic diagram of another single-stage AC-DC conversion circuit provided in an embodiment of this disclosure.
[0058] The primary-side converter circuit comprises two arms. The upper half of the first arm includes series-connected switches Q2 and Q1, and the lower half includes series-connected switches Q5 and Q6. The second arm is a capacitor arm, with the upper half including capacitor C1 and the lower half including capacitor C2. The primary-side converter circuit converts AC power at mains frequency into high-frequency AC power, which is then transferred to the secondary-side converter circuit via transformer Tr. The primary winding of the transformer is connected to impedance network Zo, and the secondary winding is connected to impedance network Z1. The secondary-side converter circuit is a rectifier converter circuit configured to output rectified DC power.
[0059] Referring to Figure 4, this figure is a schematic diagram of another single-stage AC-DC conversion circuit provided in an embodiment of this disclosure.
[0060] The difference between the primary-side converter circuit shown in Figure 4 and those in Figures 2 and 3 is that Figure 4 is a unidirectional converter circuit. The primary-side converter circuit uses an uncontrolled rectifier circuit to rectify the voltage, and then converts it into high-frequency AC power through a high-frequency conversion circuit. The transformer and secondary-side converter circuit are similar to those in Figures 2 and 3, and will not be described in detail here.
[0061] Referring to Figure 5, this figure is a schematic diagram of another single-stage AC-DC conversion circuit provided in an embodiment of this disclosure.
[0062] The difference between the primary-side conversion circuit shown in Figure 5 and Figure 4 is that the L line in Figure 5 is connected to the midpoints of the first and second half-bridges respectively through two inductors. These two half-bridges operate at high frequency, and the midpoints of these two half-bridges are connected to the impedance unit Zo and the primary side of the transformer, transferring high-frequency AC energy to the secondary side. The two parallel common points of the third half-bridge are connected in parallel to the capacitor C. The third half-bridge connected by the N line operates at the power frequency, performing the LN AC positive and negative voltage reversal function. The transformer and secondary-side conversion circuit are similar to those in Figures 2 and 3, and will not be described again here.
[0063] This disclosure does not specifically limit the topology of the DC-DC converter circuit. The DC-DC converter circuit can be, for example, an isolated DC-DC converter circuit or a non-isolated DC-DC converter circuit. Commonly used topologies include resonant DC-DC converter circuits, dual active bridge (DAB) circuits, Buck circuits, Boost circuits, and Buck-Boost circuits. The DC-DC converter circuit may be connected only to the first voltage source, only to the first DC load, or to both the first voltage source and the first DC load; this disclosure does not impose specific limitations on these aspects.
[0064] In the power conversion system described above, the DC side of the single-stage ACDC converter circuit is not connected to a voltage source, and the single-stage ACDC converter circuit operates in rectification mode. Figure 6 is a schematic diagram of the power when the AC current changes in phase with the AC voltage according to an embodiment of this disclosure. As shown in Figure 6, in the above situation, if the AC side current Iac of the single-stage ACDC converter circuit changes sinusoidally in phase with the AC side voltage Vac, the power Pac on the AC side will be transferred to the DC side of the single-stage ACDC converter circuit. Consequently, the DC side voltage will fluctuate significantly due to the change in AC side power, causing the DC side voltage to exceed the normal operating voltage range of the ACDC converter circuit, making the ACDC converter circuit unable to operate normally.
[0065] Based on the above, the controller provided in this embodiment is configured to determine the output power of the DC side of a single-stage ACDC converter circuit. The controller is further configured to determine the average output voltage range corresponding to the DC side of the single-stage ACDC converter circuit based on the output power and the upper and lower limits of the input voltage of the ACDC converter circuit. The controller is also configured to control the average output voltage of the DC side of the single-stage ACDC converter circuit to be within the average output voltage range. It is understood that the average output voltage range is determined based on the output power of the DC side and the operating voltage range of the ACDC converter circuit (i.e., the upper and lower limits of the input voltage of the ACDC converter circuit). Therefore, when the average output voltage of the DC side of the single-stage ACDC converter circuit is controlled within the average output voltage range, the output voltage of the DC side of the single-stage ACDC converter circuit will also be within the operating voltage range of the ACDC converter circuit, thereby ensuring that the output voltage of the DC side meets the requirements for normal operation of the ACDC converter circuit. The controller can control the average output voltage of the DC side of the single-stage ACDC converter circuit by sending control signals to the devices in the single-stage ACDC converter circuit. For example, the controller can monitor the average output voltage of the DC side of the single-stage ACDC converter circuit in real time, compare the average output voltage with the average output voltage range, determine the corresponding drive control signal by performing proportional integration on the comparison error, and then send the drive control signal to the semiconductor devices in the single-stage ACDC converter circuit to control the average output voltage of the DC side of the single-stage ACDC converter circuit within the average output voltage range.
[0066] The power conversion system provided in this embodiment can determine the average output voltage range of the DC side by means of the output power of the DC side of the single-stage ACDC converter circuit and the upper and lower limits of the input voltage of the DCDC converter circuit when no voltage source is connected to the DC side of the single-stage ACDC converter circuit. Then, the average output voltage of the DC side of the single-stage ACDC converter circuit can be controlled according to the average output voltage range, so that the DC side output voltage can meet the normal operation of the DCDC converter circuit.
[0067] In one embodiment, as shown in FIG1, the DC side of the single-stage ACDC converter circuit is further configured to be connected to at least one of a first voltage source and a first DC load via the DCDC converter circuit. The first DC load is an energy-consuming device configured to consume the electrical energy output from the output side of the DCDC converter circuit; the first voltage source can be an energy storage type voltage source, such as a battery, which can store the electrical energy output from the output side of the DCDC converter circuit. It is understood that when the output side of the DCDC converter circuit is simultaneously connected to both the first voltage source and the first DC load, the first voltage source can also supply power to the first DC load based on its stored energy.
[0068] In one embodiment, as shown in FIG1, in this power conversion system, the DC side of the single-stage ACDC converter circuit is further configured to be connected to a second voltage source through a switching network, and the switching network is in an open state; wherein, when the switching network is in an open state, the second voltage source can stabilize the voltage on the DC side of the single-stage ACDC converter circuit.
[0069] For example, in the power conversion system provided in this disclosure embodiment, the DC side of the single-stage ACDC converter circuit is further configured to be connected to a second voltage source via a switching network. It is understood that the switching network can be controlled by a controller; for example, the controller can control the switching network to disconnect, thereby disconnecting the second voltage source from the single-stage ACDC converter circuit; or the controller can control the switching network to close, thereby connecting the second voltage source to the DC side of the single-stage ACDC converter circuit. In this disclosure embodiment, the switching network is in an open state, and this disclosure embodiment does not specifically limit the specific type of the switching network; the switching network only needs to be a controllable switching device. Furthermore, when the switching network is in a connected state, the second voltage source can stabilize the voltage on the DC side of the single-stage ACDC converter circuit, ensuring that the DC side voltage is within the normal operating voltage range of the ACDC converter circuit.
[0070] In this embodiment, the capacity and voltage level of the first voltage source and the second voltage source are not limited. It can be understood that the capacity and voltage level of the first voltage source and the second voltage source can be the same or different.
[0071] The controller can control the average output voltage on the DC side of a single-stage ACDC converter circuit to be within the range of the average output voltage, which can include the following methods:
[0072] In one embodiment, the controller is configured to control the average output voltage of the DC side of the single-stage ACDC converter circuit to be within the range of the average output voltage, specifically: the controller is configured to determine the median of the average output voltage within the range of the average output voltage; and the controller is further configured to control the average output voltage of the DC side of the single-stage ACDC converter circuit to be equal to the median of the average output voltage.
[0073] Specifically, the controller can first determine the median of the average output voltage within the range of average output voltage values. This median can be the average of the minimum and maximum average output voltage values within the range. After determining the median, the controller consistently ensures that the average output voltage on the DC side of the single-stage ACDC converter circuit is equal to this median. Controlling the average output voltage on the DC side of the single-stage ACDC converter circuit within the median value provides better safety and better ensures that the output voltage on the DC side of the single-stage ACDC converter circuit remains within the normal operating voltage range of the DCDC converter circuit.
[0074] For example, the controller can control the average output voltage of the DC side of the single-stage ACDC converter circuit by sending control signals to the devices in the single-stage ACDC converter circuit. For instance, the controller can monitor the average output voltage of the DC side of the single-stage ACDC converter circuit in real time, compare the average output voltage with the median of the average output voltage, determine the corresponding drive control signal by performing proportional integration or other methods on the comparison error, and then send the drive control signal to the semiconductor devices in the single-stage ACDC converter circuit to control the average output voltage of the DC side of the single-stage ACDC converter circuit to be equal to the median of the average output voltage.
[0075] For example, the controller can also determine an intermediate average output voltage range within the average output voltage range. This intermediate average output voltage range can be, for example, a small range of values near the median value within the average output voltage range. This allows the controller to control the average output voltage on the DC side of the single-stage ACDC converter circuit to be within this intermediate average output voltage range, thereby ensuring that the ACDC converter circuit can operate normally.
[0076] In one embodiment, the controller is configured to control the average output voltage of the DC side of the single-stage ACDC converter circuit to be within the range of the average output voltage, specifically: the controller is configured to determine the target average output voltage corresponding to the highest conversion efficiency of the single-stage ACDC converter circuit within the range of the average output voltage; and the controller is further configured to control the average output voltage of the DC side of the single-stage ACDC converter circuit to be equal to the target average output voltage.
[0077] It is understandable that the conversion efficiency of a single-stage AC-CDC converter varies depending on the average output voltage. Higher conversion efficiency results in lower heat generation and lower losses. Based on this, the controller can determine the conversion efficiency of the single-stage AC-CDC converter for different average output voltage values within a given range. The controller then identifies the average output voltage with the highest conversion efficiency within this range as the target average output voltage. Consequently, the controller controls the average DC-side output voltage of the single-stage AC-CDC converter to be within this target range. In this case, the conversion efficiency of the single-stage AC-CDC converter is high, and the losses are low.
[0078] For example, the controller can control the average output voltage of the DC side of the single-stage ACDC converter circuit by sending control signals to the devices in the single-stage ACDC converter circuit. For instance, the controller can monitor the average output voltage of the DC side of the single-stage ACDC converter circuit in real time, compare the average output voltage with the target average output voltage, determine the corresponding drive control signal by performing proportional integration or other methods on the comparison error, and then send the drive control signal to the semiconductor devices in the single-stage ACDC converter circuit to control the average output voltage of the DC side of the single-stage ACDC converter circuit to be equal to the target average output voltage.
[0079] It should be noted that the above-described method of controlling the average output voltage of the DC side of the single-stage ACDC converter circuit to be within the range of the average output voltage is merely exemplary. This disclosure does not impose any specific limitations on it, as long as the technical principles of this disclosure can be achieved.
[0080] In one embodiment, the output power includes the maximum output power on the DC side of the single-stage ACCDC converter circuit, or the current output power on the DC side of the single-stage ACCDC converter circuit.
[0081] Specifically, the DC-side output power of a single-stage ACDC converter circuit can include the maximum output power, which can be known in advance. It is understood that the higher the output power, the smaller the determined average output voltage range. When the DC-side output power is at its maximum, the determined average output voltage range is the minimum average output voltage range. Therefore, regardless of whether the DC-side output power is at its maximum or less, as long as the average output voltage of the single-stage ACDC converter circuit is controlled within the range determined based on the maximum output power, the DC-side output voltage of the single-stage ACDC converter circuit will meet the requirements for normal operation of the DCDC converter circuit.
[0082] The DC-side output power of a single-stage AC-DC converter circuit can include the current output power. If the average output voltage range is determined based on the current output power, the current output power needs to be determined in real time or periodically so that the average output voltage range can be re-determined in a timely manner when the current output power differs from the historical output power.
[0083] In one embodiment, where the output power includes the current output power on the DC side, the controller is configured to determine the output power on the DC side of the single-stage ACDC converter circuit, specifically including: the controller being configured to acquire the current voltage and current on the DC side of the single-stage ACDC converter circuit; the controller being further configured to determine the output power on the DC side of the single-stage ACDC converter circuit based on the current voltage and current.
[0084] Specifically, when the output power includes the current output power on the DC side, the controller can obtain the current voltage and current on the DC side of the single-stage ACCDC converter circuit, and then calculate and determine the output power on the DC side of the single-stage ACCDC converter circuit using the current voltage and current.
[0085] In one embodiment, as shown in FIG1, at least one second DC load can also be connected to the DC side of the single-stage AC-CDC converter circuit. It is understood that when a second voltage source and a second DC load are connected to the DC side of the single-stage AC-CDC converter circuit, the second voltage source is typically an energy storage type voltage source. When the switching network connecting the second voltage source to the single-stage AC-CDC converter circuit is turned off, and the single-stage AC-CDC converter circuit and the second voltage source are connected, the second voltage source can supply power to each of the second DC loads on the DC side.
[0086] In one embodiment, the average output voltage range is determined based on the DC-side voltage fluctuation range of the single-stage ACDC converter circuit, as well as the upper and lower limits of the input voltage of the ACDC converter circuit; the DC-side voltage fluctuation range is determined based on the ripple power of the capacitor and the capacitance value of the capacitor, with the average output voltage as an unknown; the ripple power of the capacitor is determined based on the output power and the AC angular frequency of the AC side of the single-stage ACDC converter circuit.
[0087] Specifically, when no second voltage source is connected to the DC side of a single-stage ACDC converter circuit, power is transferred from the AC side to the DC side. The power on the AC side is denoted as Pac. If we assume that the power consumed by each second DC load on the DC side of the single-stage ACDC converter circuit and the power consumed by the DC-DC converter circuit (i.e., the output power on the DC side) are constant values Po, then the ripple power is entirely borne by the capacitors on the DC side. After determining the output power Po, the AC angular frequency on the AC side of the single-stage ACDC converter circuit is known. In this case, the output power of a single-stage AC-DC converter circuit is expressed as: Then the ripple power of the capacitor is expressed as: , where t represents time.
[0088] After determining the capacitor's ripple power, assuming the average output voltage on the DC side is Vo_avg, then the average voltage across the capacitor is also Vo_avg. The ripple current flowing through the capacitor can be approximated as: Integrating the current ic yields the peak value of the charge change on the capacitor. Based on the peak value of the charge change and the capacitance value, the peak value of the ripple voltage across the capacitor can be approximately expressed as: .
[0089] After determining the peak ripple voltage, the voltage fluctuation range on the DC side of the single-stage ACDC converter circuit, with the average output voltage as the unknown, can be determined. This DC side voltage fluctuation range is: .
[0090] It is understandable that controlling the DC-side voltage fluctuation range within the normal operating voltage range of the DC-DC converter circuit ensures its normal operation. Since the capacitor value, AC angular frequency, and output power are known, the DC-side output voltage fluctuation range can be adjusted by controlling the average output voltage Vo_avg. Therefore, given the upper input voltage limit Vo_max and lower input voltage limit Vo_min of the DC-DC converter circuit, and after determining the voltage fluctuation range expression, ensuring the DC-side voltage fluctuation range remains within the normal operating voltage range of the DC-DC converter circuit can be expressed by the following formula:
[0091] ;
[0092] ;
[0093] The range of the average output voltage can be determined using the two inequalities mentioned above. Figure 7 is a schematic diagram of the DC-side voltage waveform when the DC side is not connected to a second voltage source, according to an embodiment of this disclosure. As shown in Figure 7, when the magnitude of the average output voltage Vo_avg is controlled within the range of the average output voltage, the DC-side output voltage Vo will be within the normal operating voltage range [Vo_min, Vo_max] of the DC-DC converter circuit. It can be understood that when calculating the range of the average output voltage, the two inequalities mentioned above... It can also be equal to Vo_min. It can also be equal to Vo_max.
[0094] In one embodiment, the controller is configured to determine an average output voltage range based on the output power, the upper limit of the input voltage and the lower limit of the input voltage of the DC-DC converter circuit, when it is determined that a second voltage source is not connected to the DC side of the single-stage ACDC converter circuit, and, if the average output voltage range does not exist, to issue an alarm and reduce the output power of the DC side of the single-stage ACDC converter circuit.
[0095] It is understandable that, based on the process of determining the average output voltage range described above, if the output power is too high, the average output voltage range that meets the normal operating voltage range of the DC-DC converter circuit will not exist. In this case, the DC-DC converter circuit cannot work properly.
[0096] Therefore, if the controller determines that the average output voltage range does not exist, it can issue an alarm. This alarm can instruct the controller to ensure that the DC-side output voltage fluctuation of the single-stage ACDC converter circuit remains within the normal operating voltage range of the DCDC converter circuit by reducing the output power and / or replacing the capacitor with one of a larger value. Furthermore, if the controller determines that the average output voltage range does not exist, it can also directly reduce the DC-side output power of the single-stage ACDC converter circuit via control commands, for example, by reducing the load power and reducing the power of the DCDC converter circuit itself.
[0097] Based on the power conversion system provided in the above embodiments, this disclosure also provides a control method for the power conversion system, which will be described in detail below with reference to the accompanying drawings.
[0098] Figure 8 is a flowchart illustrating the control method of the power conversion system provided in this embodiment of the present disclosure. As shown in Figure 8, the power conversion system provided in this embodiment of the present disclosure includes a single-stage AC-DC conversion circuit, and the DC side of the single-stage AC-DC conversion circuit is configured to connect a capacitor and a DC-DC conversion circuit.
[0099] The control method 800 includes: step 801, determining the output power of the DC side of a single-stage ACDC converter circuit; and step 802, controlling the average output voltage of the DC side of the single-stage ACDC converter circuit to be within the range of the average output voltage, wherein the range of the average output voltage is determined based on the output power and the upper and lower limits of the input voltage of the DCDC converter circuit.
[0100] In the power conversion system described above, the DC side of the single-stage ACDC converter circuit is not connected to a voltage source, and the single-stage ACDC converter circuit operates in rectification mode. Figure 6 is a schematic diagram of the power when the AC current changes in phase with the AC voltage according to an embodiment of this disclosure. As shown in Figure 6, in the above situation, if the AC side current Iac of the single-stage ACDC converter circuit changes sinusoidally in phase with the AC side voltage Vac, the power Pac on the AC side will be transferred to the DC side of the single-stage ACDC converter circuit. Consequently, the DC side voltage will fluctuate significantly due to the change in AC side power, which will cause the DC side voltage to exceed the normal operating voltage range of the ACDC converter circuit, making the ACDC converter circuit unable to operate normally.
[0101] Based on the above, the control method provided in this disclosure first determines the DC output power of a single-stage ACDC converter circuit, and then determines the average output voltage range based on the output power and the upper and lower limits of the input voltage of the ACDC converter circuit. This allows the average output voltage to be controlled within the average output voltage range. It is understood that the average output voltage range in the above control method is determined based on the DC output power and the operating voltage range of the ACDC converter circuit (i.e., the upper and lower limits of the input voltage of the ACDC converter circuit). Therefore, by controlling the average output voltage of the DC side of the single-stage ACDC converter circuit within the average output voltage range, the output voltage of the DC side of the single-stage ACDC converter circuit will also be within the operating voltage range of the ACDC converter circuit, thus ensuring that the DC output voltage meets the requirements for normal operation of the ACDC converter circuit. This method controls the average output voltage of the DC side of a single-stage ACDC converter circuit by sending control signals to the devices in the circuit. For example, the average output voltage of the DC side of the single-stage ACDC converter circuit can be monitored in real time, and the average output voltage can be compared with the range of average output voltage. The corresponding drive control signal is determined by proportional integration or other methods based on the comparison error, and then the drive control signal is sent to the semiconductor devices in the single-stage ACDC converter circuit to control the average output voltage of the DC side of the single-stage ACDC converter circuit within the range of average output voltage.
[0102] The control method for the power conversion system provided in this embodiment can determine the average output voltage range of the DC side by means of the output power of the DC side of the single-stage ACDC converter circuit and the upper and lower limits of the input voltage of the DCDC converter circuit when no voltage source is connected to the DC side of the single-stage ACDC converter circuit. Then, the average output voltage of the DC side of the single-stage ACDC converter circuit can be controlled according to the average output voltage range, so that the DC side output voltage can meet the normal operation of the DCDC converter circuit.
[0103] In one embodiment, in the power conversion system, the DC side of the single-stage AC-DC converter circuit is further configured to be connected to a second voltage source via a switching network, and the switching network is in an open state.
[0104] For example, in the power conversion system provided in this disclosure embodiment, the DC side of the single-stage ACDC converter circuit is further configured to be connected to a second voltage source via a switching network. It is understood that the second voltage source can be disconnected from the single-stage ACDC converter circuit by controlling the switching network, for example, by controlling the switching network to open; or by controlling the switching network to close, the second voltage source can be connected to the DC side of the single-stage ACDC converter circuit. In this disclosure embodiment, the switching network is in an open state, and this disclosure embodiment does not specifically limit the specific type of the switching network; the switching network only needs to be a controllable switching device.
[0105] In this embodiment, the capacity and voltage level of the first voltage source and the second voltage source are not limited. It can be understood that the capacity and voltage level of the first voltage source and the second voltage source can be the same or different.
[0106] The methods for controlling the average output voltage on the DC side of a single-stage ACDC converter circuit to remain within the range of the average output voltage can include the following:
[0107] In one embodiment, controlling the average output voltage of the DC side of the single-stage ACDC converter circuit to be within the range of the average output voltage specifically involves: determining the median of the average output voltage within the range of the average output voltage; and controlling the average output voltage of the DC side of the single-stage ACDC converter circuit to be equal to the median of the average output voltage.
[0108] Specifically, the median of the average output voltage can be determined first within the range of average output voltage values. This median can be the average of the minimum and maximum average output voltage values within the range. After determining the median, the average output voltage on the DC side of the single-stage ACDC converter circuit is always kept equal to this median. Controlling the average output voltage on the DC side of the single-stage ACDC converter circuit within the range of the median output voltage values provides better safety and ensures that the output voltage on the DC side of the single-stage ACDC converter circuit remains within the normal operating voltage range of the DCDC converter circuit.
[0109] For example, the average output voltage of the DC side of a single-stage ACDC converter circuit can be controlled by sending control signals to the devices in the circuit. For instance, the average output voltage of the DC side of the single-stage ACDC converter circuit can be monitored in real time, and the average output voltage can be compared with the median of the average output voltage. The corresponding drive control signal can be determined by performing proportional integration or other methods on the comparison error, and then the drive control signal can be sent to the semiconductor devices in the single-stage ACDC converter circuit to control the average output voltage of the DC side of the single-stage ACDC converter circuit to be equal to the median of the average output voltage.
[0110] For example, an intermediate average output voltage range can also be determined within the average output voltage range. This intermediate average output voltage range can be, for example, a small range of values near the median value within the average output voltage range. This allows the average output voltage of the DC side of the single-stage ACDC converter circuit to be controlled within this intermediate average output voltage range, ensuring that the DCDC converter circuit can operate normally.
[0111] In one embodiment, controlling the average output voltage of the DC side of the single-stage ACDC converter circuit to be within the range of the average output voltage range specifically involves: determining the target average output voltage corresponding to the highest conversion efficiency of the single-stage ACDC converter circuit within the range of the average output voltage range; and controlling the average output voltage of the DC side of the single-stage ACDC converter circuit to be equal to the target average output voltage.
[0112] It is understandable that the conversion efficiency of a single-stage AC-CDC converter varies depending on the average output voltage. Higher conversion efficiency results in lower heat generation and lower losses. Therefore, we can first determine the conversion efficiency of the single-stage AC-CDC converter for each different average output voltage within the range. The average output voltage with the highest conversion efficiency within this range is then identified as the target average output voltage. Subsequently, the average DC-side output voltage of the single-stage AC-CDC converter is controlled to be within this target range. In this case, the conversion efficiency of the single-stage AC-CDC converter is high, and the losses are low.
[0113] For example, the average output voltage of the DC side of a single-stage ACDC converter circuit can be controlled by sending control signals to the devices in the circuit. For instance, the average output voltage of the DC side of the single-stage ACDC converter circuit can be monitored in real time, and the average output voltage can be compared with the target average output voltage. The corresponding drive control signal can be determined by performing proportional integration or other methods on the comparison error, and then the drive control signal can be sent to the semiconductor devices in the single-stage ACDC converter circuit to control the average output voltage of the DC side of the single-stage ACDC converter circuit to be equal to the target average output voltage.
[0114] It is understood that the above-described method of controlling the average output voltage of the DC side of the single-stage ACDC converter circuit to be within the range of the average output voltage is merely an example. This disclosure does not impose any specific limitations on it, as long as the technical principles of this disclosure can be achieved.
[0115] In one embodiment, the output power includes the maximum output power on the DC side of the single-stage ACCDC converter circuit, or the current output power on the DC side of the single-stage ACCDC converter circuit.
[0116] Specifically, the DC-side output power of a single-stage ACDC converter circuit can include the maximum output power, which can be known in advance. It is understood that the higher the output power, the smaller the determined average output voltage range. When the DC-side output power is at its maximum, the determined average output voltage range is the minimum average output voltage range. Therefore, regardless of whether the DC-side output power is at its maximum or less, as long as the average output voltage of the single-stage ACDC converter circuit is controlled within the range determined based on the maximum output power, the DC-side output voltage of the single-stage ACDC converter circuit will meet the requirements for normal operation of the DCDC converter circuit.
[0117] The DC-side output power of a single-stage AC-DC converter circuit can include the current output power. If the average output voltage range is determined based on the current output power, the current output power needs to be determined in real time or periodically so that the average output voltage range can be re-determined in a timely manner when the current output power differs from the historical output power.
[0118] In one embodiment, when the output power includes the current output power on the DC side, determining the output power on the DC side of the single-stage ACCDC converter circuit specifically includes: acquiring the current voltage and current on the DC side of the single-stage ACCDC converter circuit; and determining the output power on the DC side of the single-stage ACCDC converter circuit based on the current voltage and current.
[0119] Specifically, when the output power includes the current output power on the DC side, the current voltage and current on the DC side of the single-stage ACDC converter circuit can be obtained, and then the output power on the DC side of the single-stage ACDC converter circuit can be calculated and determined using the current voltage and current.
[0120] In one embodiment, the DC side of the single-stage AC-DC converter circuit is also configured to be connected to at least one second DC load.
[0121] It is understandable that when a second voltage source and a second DC load are connected to the DC side of a single-stage ACCDC converter circuit, the second voltage source can typically be an energy storage type voltage source. When the switching network connecting the second voltage source to the single-stage ACCDC converter circuit is turned off, and the single-stage ACCDC converter circuit and the second voltage source are connected, the second voltage source can supply power to each of the second DC loads on the DC side.
[0122] In one embodiment, determining the average output voltage range of a single-stage ACDC converter circuit on the DC side based on the output power and the upper and lower limits of the input voltage of the ACDC converter circuit includes: determining the capacitor's ripple power based on the output power and the AC angular frequency of the AC side of the single-stage ACDC converter circuit; constructing an expression for the DC side voltage fluctuation range with the average output voltage as an unknown based on the capacitor's ripple power and capacitance value; and determining the average output voltage range based on the expression for the DC side voltage fluctuation range and the upper and lower limits of the input voltage of the ACDC converter circuit.
[0123] Specifically, in a single-stage AC-CDC converter circuit where no second voltage source is connected to the DC side, power is transferred from the AC side to the DC side. The power on the AC side is denoted as Pac. If we assume that the power consumed by the second DC load on each DC side of the single-stage AC-CDC converter circuit (i.e., the output power on the DC side) is a constant value Po, then the ripple power is entirely borne by the DC-side capacitors. After determining the output power Po, the AC angular frequency on the AC side of the single-stage AC-CDC converter circuit is known. In this case, the output power of a single-stage AC-DC converter circuit is expressed as: Then the ripple power of the capacitor can be expressed as , where t represents time.
[0124] After determining the capacitor's ripple power, assuming the average output voltage on the DC side is Vo_avg, then the average voltage across the capacitor is also Vo_avg. Therefore, the ripple current flowing through the capacitor can be approximated as: Integrating the current ic yields the peak value of the charge change on the capacitor. Based on the peak value of the charge change and the capacitance value, the peak value of the ripple voltage across the capacitor can be approximately expressed as: .
[0125] After determining the expression for the peak ripple voltage, an expression for the voltage fluctuation range on the DC side of a single-stage AC-CDC converter circuit with the average output voltage as the unknown is constructed: .
[0126] It is understandable that controlling the DC-side voltage fluctuation range within the normal operating voltage range of the DC-DC converter circuit ensures its normal operation. Since the capacitor value, AC angular frequency, and output power are known, the DC-side output voltage fluctuation range can be adjusted by controlling the average output voltage Vo_avg. Therefore, given the upper input voltage limit Vo_max and lower input voltage limit Vo_min of the DC-DC converter circuit, and after determining the voltage fluctuation range expression, ensuring the DC-side voltage fluctuation range remains within the normal operating voltage range of the DC-DC converter circuit can be expressed by the following formula:
[0127] ;
[0128] ;
[0129] The range of the average output voltage can be determined using the two inequalities mentioned above. Figure 7 is a schematic diagram of the DC-side voltage waveform when the DC side is not connected to a second voltage source, according to an embodiment of this disclosure. As shown in Figure 7, when the magnitude of the average output voltage Vo_avg is controlled within the range of the average output voltage, the DC-side output voltage Vo will be within the normal operating voltage range [Vo_min, Vo_max] of the DC-DC converter circuit. It can be understood that when calculating the range of the average output voltage, the two inequalities mentioned above... It can also be equal to Vo_min. It can also be equal to Vo_max.
[0130] In one embodiment, if the average output voltage range is not available, at least one of the following is performed: issuing an alarm and reducing the output power on the DC side of the single-stage AC-DC converter circuit.
[0131] It is understandable that, based on the process of determining the average output voltage range described above, if the output power is too high, the average output voltage range that meets the normal operating voltage range of the DC-DC converter circuit will not exist. In this case, the DC-DC converter circuit cannot work properly.
[0132] Therefore, if the average output voltage range is determined to be nonexistent, an alarm can be issued. This alarm can instruct the user to ensure that the DC-side output voltage fluctuation of the single-stage ACDC converter circuit remains within the normal operating voltage range of the DCDC converter circuit by either reducing the output power or replacing the capacitor with one of a larger capacitance value. Furthermore, if the average output voltage range is determined to be nonexistent, the DC-side output power of the single-stage ACDC converter circuit can also be directly reduced via control commands, for example, by reducing the load power or reducing the power of the DCDC converter circuit itself.
[0133] According to a third aspect of this application, a controller is also provided. This controller is capable of executing the control methods described in the various embodiments above. The principles and schemes of the control methods are described above in conjunction with the various embodiments and accompanying drawings, and will not be repeated here.
[0134] Those skilled in the art will understand that various modifications, combinations, partial combinations, and substitutions may be made to this disclosure depending on design requirements and other factors, provided that they are within the scope of the appended claims and their equivalents.
[0135] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.
[0136] Furthermore, the terms "first" and "second" are configured for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.
[0137] In this disclosure, unless otherwise stated, directional terms such as "up" and "down" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction; similarly, for ease of understanding and description, "left" and "right" are generally used in relation to the left and right shown in the accompanying drawings; "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself, but the above directional terms are not configured to limit this disclosure.
[0138] The above are merely exemplary embodiments of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope described in this disclosure, and these should all be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.
Claims
1. A power conversion system comprising: Single-stage AC-DC converter circuit and controller; The DC side of the single-stage ACDC converter circuit is configured to connect a capacitor and a DC-CDC converter circuit. The controller is configured to determine the DC-side output power of the single-stage AC-DC converter circuit; The controller is further configured to control the average output voltage of the DC side of the single-stage ACDC converter circuit within a range of average output voltage values, wherein the range of average output voltage values is determined based on the output power and the upper and lower limits of the input voltage of the DCDC converter circuit.
2. The power conversion system of claim 1, wherein, The DC side of the single-stage ACDC converter circuit is also configured to be connected to at least one of a first voltage source and a first DC load via the DCDC converter circuit.
3. The power conversion system of claim 1, wherein, The DC side of the single-stage ACDC converter circuit is further configured to be connected to a second voltage source via a switching network, and the switching network is in an open state; wherein, when the switching network is in an open state, the second voltage source can stabilize the voltage on the DC side of the single-stage ACDC converter circuit.
4. The power conversion system of claim 1, wherein, The controller is configured to control the average value of the DC-side output voltage of the single-stage ACDC converter circuit within the range of the average output voltage, specifically: The controller is configured to determine the median of the average output voltage within the range of the average output voltage; and, The controller is also configured to control the average value of the DC-side output voltage of the single-stage ACDC converter circuit to be equal to the median of the average output voltage.
5. The power conversion system of claim 1, wherein, The controller is configured to control the average value of the DC-side output voltage of the single-stage ACDC converter circuit within the range of the average output voltage, specifically: The controller is configured to determine a target average output voltage corresponding to the highest conversion efficiency of the single-stage ACDC converter circuit within the range of the average output voltage; and The controller is also configured to control the average value of the DC-side output voltage of the single-stage ACCDC converter circuit to be equal to the target average value of the output voltage.
6. The power conversion system of claim 1, wherein, The output power includes the maximum output power on the DC side of the single-stage ACDC converter circuit, or the output power includes the current output power on the DC side of the single-stage ACDC converter circuit.
7. The power conversion system of any one of claims 1 to 6, wherein, The average output voltage range is determined based on the DC-side voltage fluctuation range of the single-stage ACDC converter circuit, as well as the upper and lower limits of the input voltage of the ACDC converter circuit; the DC-side voltage fluctuation range is determined based on the ripple power of the capacitor and the capacitance value of the capacitor, with the average output voltage as an unknown quantity; the ripple power of the capacitor is determined based on the output power and the AC angular frequency of the AC side of the single-stage ACDC converter circuit.
8. The power conversion system of claim 1, wherein, The controller is configured to, when it is determined that the DC side of the single-stage ACDC converter is not connected to a second voltage source, determine the average range of the output voltage based on the output power and the upper and lower limits of the input voltage of the DCDC converter, and, if the average range of the output voltage does not exist, provide an alarm and reduce the output power of the DC side of the single-stage ACDC converter.
9. A control method for a power conversion system, the power conversion system comprising a single-stage AC-DC conversion circuit, wherein the DC side of the single-stage AC-DC conversion circuit is configured to connect a capacitor and a DC-DC conversion circuit; The control method includes: Determine the DC-side output power of the single-stage AC-DC converter circuit; The average output voltage of the DC side of the single-stage ACDC converter circuit is controlled to be within the range of the average output voltage, wherein the range of the average output voltage is determined based on the output power and the upper limit and lower limit of the input voltage of the DCDC converter circuit.
10. The control method according to claim 9, wherein Specifically, controlling the average output voltage of the DC side of the single-stage ACDC converter circuit to be within the range of average output voltage means: Determine the median of the average output voltage within the range of the average output voltage; and, The average value of the DC-side output voltage of the single-stage AC-DC converter circuit is equal to the median of the average output voltage.
11. The control method according to claim 9, wherein Specifically, controlling the average output voltage of the DC side of the single-stage ACDC converter circuit to be within the range of average output voltage means: Determine the target average output voltage corresponding to the highest conversion efficiency of the single-stage ACDC converter circuit within the range of the stated average output voltage; and, The average value of the DC-side output voltage of the single-stage AC-DC converter circuit is controlled to be equal to the target average value of the output voltage.
12. The control method according to claim 9, wherein The output power includes the maximum output power on the DC side of the single-stage ACDC converter circuit, or the output power includes the current output power on the DC side of the single-stage ACDC converter circuit.
13. The control method according to any one of claims 9 to 12, wherein The step of determining the average range of the output voltage based on the output power and the upper and lower limits of the input voltage of the DC-DC converter circuit includes: The ripple power of the capacitor is determined based on the output power and the AC angular frequency on the AC side of the single-stage AC-CDC converter circuit. Based on the ripple power of the capacitor and the capacitance value of the capacitor, the DC side voltage fluctuation range is determined with the average output voltage as the unknown quantity. The average output voltage range is determined based on the DC-side voltage fluctuation range and the upper and lower limits of the input voltage of the DC-DC converter circuit.
14. The control method according to claim 9, wherein If the average output voltage range is not present, at least one of the following actions shall be taken: issuing an alarm or reducing the output power on the DC side of the single-stage AC-DC converter circuit.
15. A controller comprising a memory and a processor, wherein the memory stores computer program instructions, and the processor, when processing the program instructions, performs the control method of any one of claims 9-14.