Three-phase single-stage SWISS rectifier control method for realizing phase compensation and reducing input current harmonics

Abstract

The invention belongs to the technical field of SWISS rectifier control, and particularly relates to a three-phase single-stage SWISS rectifier control method for realizing phase compensation and reducing input current harmonics, and the method carries out voltage outer loop control through a single PI controller, and avoids a complex parameter adjustment process in a traditional double-PI control method. The single-cycle control based on the inductive current average value directly tracks a three-phase input current instruction, the influence of direct current side inductive current fluctuation on a control loop is reduced, and input current harmonics are reduced. The problem that the grid-side power factor is reduced due to the filter capacitor is solved through a phase compensation mechanism, and the power factor of the rectifier is improved. The method shows higher grid-side power factors and lower input current harmonics under different power levels, has the characteristics of simplicity in control and excellent performance, and is suitable for application scenes needing high-efficiency energy conversion and low harmonic pollution, such as new energy automobile charging piles and aviation power supplies.

Description

Technical Field

[0001] The present invention belongs to the technical field of SWISS rectifier control, and specifically relates to a control method for a three-phase single-stage SWISS rectifier that realizes phase compensation and reduces input current harmonics. Background Art

[0002] With the gradual depletion of traditional energy sources and the increasing importance of electricity as a clean energy source, the rapid development of new energy electric vehicles has driven the demand for efficient charging infrastructure, especially high-power AC-DC conversion power modules. Due to design limitations, traditional diode rectifier circuits cause serious harmonic pollution, affecting the quality and stability of the power grid. To solve this problem, three-phase high-power rectifiers with power factor correction (PFC) functions have been proposed, which not only achieve efficient energy conversion but also significantly improve the quality of the input current. The SWISS rectifier topology proposed by Professor J.W. Kolar in 2012 has become an ideal choice as an advanced solution, with advantages such as unity power factor operation and low input current harmonics. The SWISS rectifier has advantages such as low system cost, high power density, and applicability to multiple scenarios, and is widely used in fields such as new energy vehicle charging piles and aviation power supplies.

[0003] Although the SWISS rectifier has many advantages, its control process is relatively complex. Especially in engineering applications, existing control methods often have the following problems: First, the traditional dual-PI control method (CDPIC) requires a complex parameter adjustment process, and the fluctuation of the inductor current on the DC side is introduced into the current control through the inner loop, resulting in an increase in the harmonic content of the input current; second, existing control methods do not fully consider the influence of the filter capacitor on the grid-side power factor, resulting in a decrease in the grid-side power factor; in addition, existing control methods perform poorly in terms of dynamic response and anti-interference ability, and it is difficult to meet the requirements of actual engineering applications. Therefore, there is an urgent need for a control method that is easy to implement and can effectively reduce input current harmonics and improve the grid-side power factor. Summary of the Invention

[0004] The purpose of the present invention is to provide a control method for a three-phase single-stage SWISS rectifier that realizes phase compensation and reduces input current harmonics, so as to solve the problems in the prior art that the control method of the SWISS rectifier is complex, and the fluctuation of the inductor current on the DC side and the influence of the filter capacitor result in an increase in input current harmonics and a decrease in the grid-side power factor.

[0005] The present invention realizes the above purpose through the following technical solutions:

[0006] The present invention proposes a control method for a three-phase single-stage SWISS rectifier that realizes phase compensation and reduces input current harmonics, and the method includes the following steps:

[0007] S1. Based on a single PI controller, perform voltage outer-loop control on the SWISS rectifier to obtain the reference value of the d-axis component of the machine-side current;

[0008] S2. Determine the capacitance value of the filter capacitor of the SWISS rectifier, the grid angular frequency, and the grid d-axis component, calculate the phase compensation value, and adjust the reference value of the q-axis component of the machine-side current according to the phase compensation value;

[0009] S3. Transform the reference value of the d-axis component of the machine-side current and the reference value of the q-axis component of the machine-side current into the reference value of the three-phase current through coordinate transformation;

[0010] S4. In each control period, sample and obtain the average value of the input current of the SWISS rectifier, and adjust the duty cycle of the high-frequency switching tube of the SWISS rectifier according to the error between the average value of the input current and the reference value of the three-phase current.

[0011] Further, step S1 includes:

[0012] S1.1. Monitor the DC output voltage of the SWISS rectifier;

[0013] S1.2. Compare the monitored DC output voltage with the preset DC voltage reference value to obtain a voltage error signal;

[0014] S1.3. Input the voltage error signal into a single PI controller, and after proportional-integral operation, output the reference value of the d-axis component of the machine-side current.

[0015] Further, step S2 includes:

[0016] S2.1. Confirm that the three-phase power grid of the SWISS rectifier is symmetric and the capacitance values of the three-phase filter capacitors are equal, and maintain the reactive current of the three-phase capacitor voltage as:

[0017] i Cq = ωC s e d

[0018] where is the angular frequency obtained by grid phase-locking, C s is the capacitance value of the filter capacitor, e d is the grid d-axis component obtained by coordinate transformation of the power grid;

[0019] S2.2. Perform phase compensation according to the reactive current and adjust the reference value of the q-axis component of the machine-side current i q_ref , so that the phase of the machine-side current is synchronized with the grid voltage. Then, the calculation formula for the reference value of the q-axis component of the machine-side current i q_ref is:

[0020] iq_ref = -ωC s e d

[0021] S2.3. Obtain the reference value \(i_{qref}\) of the q - axis component of the machine - side current according to the constraint that the machine - side current cannot be discontinuous. q_ref The final expression of

[0022]

[0023] where \(i_{dref}\) d_ref is the reference value of the d - axis component of the machine - side current; the specific constraint is that the phase - angle difference between the machine - side current and the grid voltage shall not exceed ±30°, and the expression is:

[0024] Furthermore, in step S3, the calculation formula for converting the reference values of the d - axis and q - axis components of the machine - side current into the orthogonal relationship with the grid current is:

[0025] \(i_{dref}\) x_ref = \(i_{refmax}\) d_ref ·cos(θ x ) - \(i_{refmin}\) q_ref ·sin(θ x )

[0026] \(i_{qref}\) z_ref = \(i_{refmax}\) d_ref ·cos(θ z ) - \(i_{refmin}\) q_ref ·sin(θ z )

[0027] where \(i_{refmax}\) x_ref and \(i_{refmin}\) z_ref are the reference values of the input currents corresponding to the maximum - phase and minimum - phase of the input voltage of the SWISS rectifier respectively, and θ x and θ z are the phase - angles of the maximum - phase and minimum - phase of the grid voltage respectively.

[0028] Furthermore, in step S4, the step of controlling the duty cycle of the high - frequency switching transistor is based on the average value of the inductor current for single - cycle control.

[0029] Furthermore, step S4 includes:

[0030] S4.1. In each control cycle, sample and obtain the average value \(I_{avg}\) of the input current of the SWISS rectifier; dc ;

[0031] S4.2. Compare the average value \(I_{avg}\) of the input current dc with the three - phase current reference values \(i_{aref}\) x_ref and \(i_{cref}\) z_re f to obtain the current error signal;

[0032] S4.3. Adjust the duty ratio of the high-frequency switching transistors of the SWISS rectifier according to the current error signal, so that the average value of the input current directly tracks the three-phase current reference value. The calculation formula is as follows:

[0033]

[0034] where d p and d n are the duty ratios of the high-frequency switching transistors S p and S n of the SWISS rectifier respectively.

[0035] Furthermore, the method further includes:

[0036] During the control process of the SWISS rectifier, determine the maximum phase, intermediate phase, and minimum phase of the grid voltage through sorting, and generate the driving signals S a , S b and S c of the low-frequency switching transistors according to the sorting result.

[0037] The beneficial effects of the present invention are as follows:

[0038] 1. By adopting a single PI controller for voltage outer-loop control, the present invention avoids the complex parameter adjustment process in the traditional dual-PI control method and reduces the complexity of the control system; through single-cycle control based on the average value of the inductor current, it directly tracks the three-phase input current command, effectively reducing the influence of the DC-side inductor current fluctuation on the control loop, thereby reducing the harmonic content of the input current.

[0039] 2. The present invention also solves the problem of reduced grid-side power factor caused by the filter capacitor through a phase compensation mechanism, significantly improving the grid-side power factor of the rectifier. This method exhibits a higher grid-side power factor and lower input current harmonics at different power levels, and also has better dynamic response and anti-interference capabilities than the traditional control method. Therefore, the present invention not only simplifies the control implementation but also significantly improves the overall performance of the SWISS rectifier, having high engineering application value. Description of the Drawings

[0040] Figure 1 is a schematic flow chart of a three-phase single-stage SWISS rectifier control method for realizing phase compensation and reducing input current harmonics provided by an embodiment of the present application;

[0041] Figure 2 is a control block diagram of the SWISS rectifier in an embodiment of the present application;

[0042] Figure 3Schematic diagram of the specific process of SWISS rectifier instruction calculation in the embodiments of the present application;

[0043] Figure 4 Physical platform of part of the SWISS rectifier in the case of the present application;

[0044] Figure 5 Experimental waveform diagram of power factor correction of the control method without phase compensation based on the CDPIC method and the method proposed in the present application in Comparative Experiment 1 of the present application;

[0045] Figure 6 Experimental waveform diagram of power factor correction of the control method with phase compensation based on the method proposed in the present application in Comparative Experiment 1 of the present application;

[0046] Figure 7 Experimental waveform diagram of the steady-state performance comparison between the CDPIC method and the control method with phase compensation based on the method proposed in the present application at the power level of 2.7 kW in Comparative Experiment 2 of the present application.

[0047] Figure 8 Experimental waveform diagram of the steady-state performance comparison between the CDPIC method and the control method with phase compensation based on the method proposed in the present application at the power level of 2 kW in Comparative Experiment 2.

[0048] Figure 9 Experimental waveform diagram of the load sudden increase of the CDPIC method and the control method with phase compensation based on the method proposed in the present application in Comparative Experiment 3;

[0049] Figure 10 Experimental waveform diagram of the load sudden decrease of the CDPIC method and the control method with phase compensation based on the method proposed in the present application in Comparative Experiment 3. Detailed implementation manners

[0050] The following further describes the present application in detail with reference to the accompanying drawings. It is necessary to point out here that the following specific implementation manners are only used to further illustrate the present application and cannot be understood as limiting the protection scope of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application according to the above application content.

[0051] Embodiment 1

[0052] As Figure 1 shown, this embodiment proposes a three-phase single-stage SWISS rectifier control method for realizing phase compensation and reducing input current harmonics. The method includes the following steps:

[0053] S1. Perform voltage outer-loop control on the SWISS rectifier based on a single PI controller to obtain the reference value of the d-axis component of the machine-side current.

[0054] More specifically, step S1 includes:

[0055] S1.1. Monitor the DC output voltage of the SWISS rectifier;

[0056] S1.2. Compare the monitored DC output voltage with a preset DC voltage reference value to obtain a voltage error signal;

[0057] S1.3. Input the voltage error signal into a single PI controller, and after proportional-integral operation, output the reference value of the d-axis component of the machine-side current.

[0058] S2. Determine the capacitance value of the filter capacitor of the SWISS rectifier, the grid angular frequency, and the grid d-axis component, calculate the phase compensation value, and adjust the reference value of the q-axis component of the machine-side current according to the phase compensation value.

[0059] More specifically, step S2 includes:

[0060] S2.1. Confirm that the three-phase power grid of the SWISS rectifier is symmetric and the capacitance values of the three-phase filter capacitors are equal, and maintain the reactive current of the three-phase capacitor voltages as:

[0061] i Cq = ωC s e d

[0062] Wherein, is the angular frequency obtained by grid phase-locking, C s is the capacitance value of the filter capacitor, e d is the grid d-axis component obtained by coordinate transformation of the power grid;

[0063] S2.2. Perform phase compensation according to the reactive current and adjust the reference value of the q-axis component of the machine-side current i q_ref , so that the phase of the machine-side current is synchronized with the grid voltage. Then, the calculation formula for the reference value of the q-axis component of the machine-side current i q_ref is:

[0064] i q_ref = -ωC s e d

[0065] S2.3. According to the constraint condition that the machine-side current cannot be discontinuous, obtain the final expression of the reference value of the q-axis component of the machine-side current i q_ref as:

[0066]

[0067] Wherein, i d_refis the reference value of the d-axis component of the machine-side current; the constraint condition is specifically that the phase angle difference between the machine-side current and the grid voltage shall not exceed ±30°, and the expression is:

[0068] It should be noted that the control block diagram of the SWISS rectifier is as Figure 2 shown. The phase angle of the grid is obtained by phase-locking the three-phase grid on the AC side After the three-phase grid coordinate transformation, the d-axis component e of the grid is obtained d . Both of these parameters are necessary parameters for the control method proposed in this application. Of course, by sorting the instantaneous values of the three-phase grid, the intermediate phase of the grid instantaneous values within the power frequency period can also be determined, so as to obtain the driving signals S a 、S b 、S c of the three-phase low-frequency tubes of the SWISS rectifier.

[0069] In addition to the grid-related information and the capacitance value C of the filter capacitor on the AC side s , the method proposed in this application also needs to obtain the reference value of the d-axis component of the machine-side current of the SWISS rectifier, that is, i d_ref . This value is obtained through the PI control of the DC-side voltage, that is:

[0070] i d_ref =K P (u ref -u dc )+K I ∫(u ref -u dc )dt

[0071] Among them, u ref and u dc are the reference value and the sampled value of the DC-side output voltage of the SWISS rectifier respectively, and K P and K I are the proportional and integral coefficients of the voltage outer-loop PI regulator respectively. The output of the command calculation link is the reference value i x_ref of the input current corresponding to the maximum input voltage of the SWISS rectifier and the reference value i z_ref of the input current corresponding to the minimum input voltage. By performing PWM modulation with the inductor current I dc , the final driving signals of the two high-frequency switches can be obtained.

[0072] S3. Transform the reference value of the d-axis component of the machine-side current and the reference value of the q-axis component of the machine-side current into the reference value of the three-phase current through coordinate transformation.

[0073] In step S3, the calculation formula for converting the reference values of the d-axis and q-axis components of the machine-side current into the orthogonal relationship with the grid current is as follows:

[0074]

[0075] i z_ref =i d_ref ·cox(θ z )-i q_ref ·sin(θ z )

[0076] where, i x_ref and i z_ref are the reference values of the input currents corresponding to the maximum phase and the minimum phase of the input voltage of the SWISS rectifier respectively, and θ x and θ z are the phase angles of the maximum phase and the minimum phase of the grid voltage respectively.

[0077] S4. In each control cycle, sample and obtain the average value of the input current of the SWISS rectifier, and adjust the duty ratio of the high-frequency switching tubes of the SWISS rectifier according to the error between the average value of the input current and the three-phase current reference values.

[0078] In step S4, the step of controlling the duty ratio of the high-frequency switching tubes is based on the average value of the inductor current for single-cycle control, so that the average value of the input current can directly track the three-phase current reference values, to achieve phase compensation of the SWISS rectifier, reduce the input current harmonics, and improve the overall performance of the rectifier.

[0079] More specifically, step S4 includes:

[0080] S4.1. In each control cycle, sample and obtain the average value of the input current I dc ;

[0081] S4.2. Compare the average value of the input current I dc with the three-phase current reference values i x_ref and i z_re f to obtain the current error signal;

[0082] S4.3. Adjust the duty ratio of the high-frequency switching tubes of the SWISS rectifier according to the current error signal, so that the average value of the input current directly tracks the three-phase current reference values. The calculation formula is:

[0083]

[0084] where, dp and dn are the duty ratios of the high-frequency switching tubes Sp and Sn of the SWISS rectifier respectively.

[0085] It should be noted that the core control of the instruction calculation link in the above solution is as Figure 3 shown. Among them, the reference value i of the q-axis component of the machine-side current q_ref The main function of the final expression is to perform phase compensation to obtain i q_ref . Combining the i obtained from the voltage outer loop d_ref Perform coordinate transformation to obtain the reference instruction of the machine-side input current of the SWISS rectifier. After sorting, the current modulation signals required for the two high-frequency tubes of the SWISS rectifier to be output by the method proposed in this application can be obtained.

[0086] In a specific embodiment, the method further includes: during the control process of the SWISS rectifier, determine the maximum phase, intermediate phase, and minimum phase of the grid voltage through sorting, and generate the driving signals S a , S b and S c of the low-frequency switching tubes according to the sorting result. Determine the maximum phase, intermediate phase, and minimum phase of the grid voltage through sorting, and generate the driving signals S a , S b and S c of the low-frequency switching tubes according to the sorting result. This step plays a key role in the control process of the SWISS rectifier. It ensures the correctness of the current injection path, optimizes the current distribution and energy conversion efficiency, reduces the input current harmonics, improves the dynamic response ability and anti-interference ability of the system. At the same time, this mechanism simplifies the control logic, ensures the continuity of the machine-side current, and thus improves the overall performance and reliability of the rectifier. By sorting the instantaneous value of the grid voltage in real time and generating the corresponding driving signals, the system can quickly respond to the changes in the grid voltage, ensuring that the rectifier can still maintain a stable working state when the grid voltage fluctuates or the load changes suddenly.

[0087] It can be understood that when this solution is specifically implemented, its implementation process mainly includes the following steps:

[0088] Voltage outer loop control: First, detect the DC-side output voltage of the SWISS rectifier through a voltage sensor, and compare it with the set reference voltage. Use a PI controller to adjust the voltage error to obtain the reference value i d_ref of the d-axis current. This PI controller constitutes the voltage outer loop, and obtains the q-axis current reference value through phase compensation. In order to achieve phase compensation, it is necessary to calculate the reference value i q_ref of the q-axis current.

[0089] Phase compensation: In the solution of this application, the specific implementation of the phase compensation link is to calculate i q_ref。Its formula combines the phase information of the grid voltage and the d-axis current reference value id_ref obtained from the outer voltage loop to ensure that the input current of the SWISS rectifier maintains an appropriate phase relationship with the grid voltage.

[0090] Implementation of the current inner loop (based on average value control): Different from the traditional CDPIC method, this scheme does not adopt the PI inner loop control based on the instantaneous sampling value of the inductor current. Instead, it performs single-cycle control based on the average value of the inductor current. By controlling the duty cycles of the two high-frequency switches, the input average current within a single control cycle directly tracks the three-phase input current commands (i.e., i d_ref and i q_ref the three-phase current commands obtained through coordinate inverse transformation). This control method avoids the interference of the DC output inductor current fluctuation of the SWISS rectifier on the control loop, thereby reducing the harmonic content of the input current.

[0091] Sorting and modulation signal generation: After obtaining the three-phase current commands, it is necessary to sort them to determine the current modulation signals required for the two high-frequency switches of the SWISS rectifier to ensure the efficient operation of the SWISS rectifier and the low harmonic content of the input current.

[0092] Execute high-frequency modulation: Finally, modulate the high-frequency switches of the SWISS rectifier according to the generated modulation signals, thereby realizing the control of the three-phase single-stage SWISS rectifier considering phase compensation and reducing the harmonic of the input current.

[0093] In summary, this control method obtains the d-axis current reference value through the outer voltage loop, obtains the q-axis current reference value through phase compensation, and performs single-cycle control based on the average value of the inductor current to achieve effective control of the SWISS rectifier. This method not only reduces the harmonic content of the input current, but also improves the anti-interference ability and engineering applicability of the SWISS rectifier.

[0094] To more clearly illustrate the present invention and its advantages, the following will further explain the method provided by the present invention in combination with specific examples and relevant parts of the drawings.

[0095] The physical platform of the SWISS rectifier is as Figure 4As shown in the figure, it mainly consists of a power supply board, a main control board, a main power circuit, and a heat dissipation system. The core parameters related to the experiment are shown in Table 1. The experimental equipment used in the experiment includes: a physical platform of SWISS rectifier, various power supplies, a YOKOGAWA DLM3024 oscilloscope, a YOKOGAWA 700924 high-voltage differential probe, a Tektronix A621 current clamp, a Fluke 12E+ voltmeter, and a load resistor, etc. The DSP carried on the SWISS rectifier platform is the MC56F84789 chip of Freescale. The high-frequency power transistor uses the IKW75N60H3 type IGBT of Infineon.

[0096] It should be noted that the discussion of this application is only based on the condition of balanced three-phase power grid. Therefore, the control of three-phase current and the actual waveform have similar characteristics. In order to more clearly show the experimental results, only the current and voltage waveforms of phase a are retained in the experimental part of this application. In addition to the input grid voltage and input current waveforms of the SWISS rectifier, the experimental part of this application also intercepts the fluctuation amount Δ udc of the output voltage on the DC side and the fluctuation amount Δ idc of the inductor current on the DC side for comparison to more comprehensively compare the performance of different control methods.

[0097] Table 1 Experimental parameters of SWISS rectifier

[0098]

[0099] Case 1. Comparative experiment on phase compensation ability

[0100] This group of experiments is a performance comparison experiment on the phase compensation ability of the CDPIC method and the method proposed in this application. In order to fully demonstrate the applicability and effectiveness of the phase compensation algorithm proposed in this application, in this group of experiments, the control method proposed in this application is discussed separately under two control conditions: with phase compensation and without phase compensation.

[0101] As Figure 5 shown are the experimental waveforms of the CDPIC method and the control method proposed in this application (with phase compensation and without phase compensation) under the experimental conditions of a load resistance of 10Ω (output power of 4kW). It can be found from the figure that the output voltage on the DC side of the three methods is 200V, and the fluctuation amount of the DC side voltage is less than 1V. The waveforms of the three-phase current are relatively sinusoidal, and the three methods can all effectively control the SWISS rectifier. Specifically, Figure 5 the fluctuations of the output voltage on the DC side and the inductor current under the CDPIC method shown on the left in Figure 5As shown on the right side of the figure, the power factor under the control method without phase compensation proposed in this application is 0.92, and the THD of the current waveform is 2.30%. Figure 6 As shown in the figure, the power factor under the control method with phase compensation proposed in this application is 0.97, and the THD of the current waveform is 1.52%. Comparing the above experimental results, it can be seen that the control method with phase compensation proposed in this application has better phase compensation ability and better current waveform quality than the CDPIC method.

[0102] Case 2. Comparative experiment on steady-state performance under different power levels

[0103] This group of experiments mainly verifies the comparison of the steady-state performance between the CDPIC method and the control method with phase compensation proposed in this application for the SWISS rectifier under different power levels. The maximum experimental power of the SWISS rectifier involved in this application is 4kW, and the corresponding experimental results are as Figure 7 and 8 shown.

[0104] When the operating power of the SWISS rectifier is reduced to 2.7kW, the comparison results of the two methods are as Figure 7 shown. At this time, the load resistance is 15Ω, and the target output voltage on the DC side is 200V. From the experimental results, it can be seen that Figure 7 under the CDPIC method shown on the left side of the figure, the power factor is 0.9, which is lower than the power factor of 0.97 of the method proposed in this application. At the same time, the THD of the current waveform is 5.54%, which is higher than Figure 7 4.79% of the method shown on the right side of the figure. It shows that under the condition of lower power, the control method proposed in this application still has lower input current harmonics. In addition, the two methods have similar characteristics in terms of the fluctuations of the output voltage on the DC side and the inductor current on the DC side. Considering that the absolute value of the fluctuation amount is too small, no further comparative analysis is carried out here.

[0105] When the operating power of the SWISS rectifier is further reduced to 2kW, the experimental results of the two control methods are as Figure 8 shown. At this time, the load resistance is 20Ω, and the target output voltage on the DC side is 200V. The grid-side power factor under the CDPIC method is 0.91, and the grid-side power factor under the control method proposed in this application is 0.97, which is consistent with the previous experimental results. In addition, the THD of the grid-side input current under the CDPIC method is 7.07%, and the THD of the grid-side input current under the method proposed in this application is 5.14%, with lower harmonic current content. The fluctuation amount of the output voltage on the DC side under the two control methods is less than 1V, and the fluctuation amount of the inductor current on the DC side is less than 2A. However, from the experimental waveforms, the fluctuation of the output voltage on the DC side under the CDPIC method is more severe, but the fluctuation of the inductor current on the DC side of the control method proposed in this application is more severe.

[0106] Case 3. Dynamic Performance Comparison Experiment

[0107] This group of experiments is a dynamic performance comparison based on the steady-state experiment. The experimental process is mainly carried out in two cases: sudden load increase and sudden load decrease. The corresponding physical meaning is that when the output power of the SWISS rectifier changes suddenly, the dynamic recovery time of the output voltage on the DC side under different control methods is compared, as well as the voltage spike situation generated at the moment of power mutation, etc. Figure 9 The results of the sudden load increase experiment are shown. The experimental condition of the sudden load increase of the load resistance is achieved by paralleling two 20Ω resistors into an equivalent load with a resistance value of 10Ω at the mutation moment. Before and after the sudden load increase, the input current of the SWISS rectifier increases, but the output voltage on the DC side needs to remain unchanged. The voltage spike on the DC side under the CDPIC method reaches about 15V, and the dynamic recovery moment is about 40ms. The voltage spike of the method proposed in this application is about 10A, and the dynamic recovery moment is about 20ms. In terms of dynamic performance in the case of sudden load increase, the method proposed in this application has more advantages.

[0108] Figure 10 The dynamic experimental results of the two methods in the case of sudden load decrease are shown. Similar to the sudden load increase experiment, the experimental condition of the sudden load decrease is achieved by removing two paralleled 20Ω resistors (equivalent to a 10Ω load) at the mutation moment and only retaining one 20Ω resistor. Before and after the sudden load decrease, the input current of the SWISS rectifier decreases, but the output voltage on the DC side needs to recover to be unchanged. It can be seen from the experimental results that the maximum voltage jump spike generated by the CDPIC method at the moment of sudden load decrease is 15V, while the corresponding jump spike generated by the method proposed in this application is at most 10V. It takes about 40ms for the DC side voltage to recover to the voltage value before the mutation under the CDPIC method, while the method proposed in this application only takes about 15ms. The dynamic response characteristics of the two methods are similar to those in the case of sudden load increase.

[0109] The above experimental results prove that this phase compensation method can effectively correct the grid-side power factor and improve the application performance of the SWISS rectifier. The control method with phase compensation proposed in this application has better steady-state performance and anti-interference ability than the traditional dual-PI control method, and has good engineering application value.

[0110] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present application.

Claims

1. A control method for a three-phase single-stage SWISS rectifier to achieve phase compensation and reduce input current harmonics, characterized in that The method includes the following steps: S1. Based on a single PI controller, perform voltage outer-loop control on the SWISS rectifier to obtain the reference value of the d-axis component of the machine-side current; S2. Determine the capacitance value of the filter capacitor of the SWISS rectifier, the grid angular frequency, and the d-axis component of the grid, calculate the phase compensation value, and adjust the reference value of the q-axis component of the machine-side current according to the phase compensation value; S3. Transform the reference value of the d-axis component of the machine-side current and the reference value of the q-axis component of the machine-side current into the reference value of the three-phase current through coordinate transformation; S4. In each control cycle, sample and obtain the average value of the input current of the SWISS rectifier, and adjust the duty ratio of the high-frequency switching tube of the SWISS rectifier according to the error between the average value of the input current and the reference value of the three-phase current.

2. The three-phase single-stage SWISS rectifier control method for realizing phase compensation and reducing input current harmonics according to claim 1, characterized in that, Step S1 includes: S1.

1. Monitor the DC output voltage of the SWISS rectifier; S1.

2. Compare the monitored DC output voltage with the preset DC voltage reference value to obtain a voltage error signal; S1.

3. Input the voltage error signal into a single PI controller, and after proportional-integral operation, output the reference value of the d-axis component of the machine-side current.

3. The three-phase single-stage SWISS rectifier control method for realizing phase compensation and reducing input current harmonics according to claim 1, wherein, Step S2 includes: S2.

1. Confirm that the three-phase power grid of the SWISS rectifier is symmetric and the capacitance values of the three-phase filter capacitors are equal, and maintain the reactive current of the three-phase capacitor voltage as: i Cq = ωC s e d Among them, ω is the angular frequency obtained by grid phase-locking, C s is the capacitance value of the filter capacitor, e d is the d-axis component of the grid obtained by coordinate transformation of the grid; S2.

2. Perform phase compensation according to the reactive current and adjust the reference value \(i_{qref}\) of the q-axis component of the machine-side current q_ref , so that the phase of the machine-side current is synchronized with the grid voltage. Then, the calculation formula for the reference value \(i_{qref}\) of the q-axis component of the machine-side current q_ref is as follows: i q_ref = -ωCsed S2.

3. According to the constraint condition that the machine-side current cannot be discontinuous, the final expression of the q-axis component reference value i q_ref of the machine-side current is as follows: where i d_ref is the reference value of the d-axis component of the machine-side current; the specific constraint condition is that the phase angle difference between the machine-side current and the grid voltage shall not exceed ±30°, and the expression is:

4. The three-phase single-stage SWISS rectifier control method for realizing phase compensation and reducing input current harmonics according to claim 3, characterized in that, In step S3, the calculation formula for converting the reference values of the d-axis and q-axis components of the machine-side current into the orthogonal relationship with the grid current is: i x_ref = i d_ref · cos(θ x ) - i q_ref · sin(θ x ) i z_ref = i d_ref · cos(θ z ) - i q_ref · sin(θ z ) where \(i\) x_ref and \(i\) z_ref are the reference values of the input currents corresponding to the maximum phase and the minimum phase of the input voltage of the SWISS rectifier respectively, and \(\theta\) x and \(\theta\) z are the phase angles of the maximum phase and the minimum phase of the grid voltage respectively.

5. The three-phase single-stage SWISS rectifier control method for realizing phase compensation and reducing input current harmonics according to claim 1, characterized in that, In step S4, the step of controlling the duty ratio of the high-frequency switching tube is based on the average value of the inductor current for single-cycle control.

6. The three-phase single-stage SWISS rectifier control method for realizing phase compensation and reducing input current harmonics according to claim 4, wherein, Step S4 includes: S4.

1. During each control period, sample and obtain the average input current I of the SWISS rectifier dc ; S4.

2. Compare the average value of the input current, I dc with the three-phase current reference values, i x_ref and i z_re f to obtain a current error signal; S4.

3. Adjust the duty ratio of the high-frequency switching tube of the SWISS rectifier according to the current error signal, so that the average value of the input current directly tracks the reference value of the three-phase current. The calculation formula is: where d p and d n are the duty cycles of the high-frequency switching transistors S p and S n of the SWISS rectifier, respectively.

7. The three-phase single-stage SWISS rectifier control method for realizing phase compensation and reducing input current harmonics according to claim 6, characterized in that, The method further includes: During the control process of the SWISS rectifier, the maximum phase, intermediate phase, and minimum phase of the grid voltage are determined by sorting, and drive signals S a , S b , and S c of the low-frequency switching tubes are generated according to the sorting result.

Images