A control mode for wide load range operation of a Vienna rectifier

Abstract

The present application relates to a kind of Vienna rectifier wide load range operation control method mode, proposes a load power estimation algorithm, by collecting three-phase voltage, three-phase current, DC side upper and lower voltage and combining forgetting iterative filtering algorithm and sliding window filtering algorithm, accurately estimate load power and filter out the noise caused by sampling error.Based on the proposed load power algorithm, a new outer ring structure is proposed, which uses capacitor energy storage feedback and load power feedforward control to separate the control of DC side energy storage capacitor and DC load control.When load mutation occurs, the demand of load can be estimated in advance, and the calculation is introduced to the current loop, which improves the response speed of the system and better stabilizes the DC side voltage.The present application solves the problem of parameter design difficulty of the outer ring of traditional control mode of Vienna rectifier, improves the response speed when load mutation occurs, and solves the overvoltage problem during light load start.

Description

Technical Field

[0001] This invention belongs to the field of rectifier control technology, and particularly relates to a wide load range operation control method for Vienna rectifiers. Background Technology

[0002] With the rapid development of power electronic devices in the field of power grid conversion, power factor correction (PFC) circuits have become a research hotspot in this field. Vienna rectifiers, as a type of three-phase three-level PFC circuit, are widely used in high-power applications such as power communication power supplies and electric vehicle charging due to their high efficiency and reliability. However, this has also brought new challenges. The topology of the Vienna rectifier dictates that energy can only flow in one direction, which poses difficulties for the design of the outer voltage loop: when voltage overshoot occurs during dynamic adjustment, the Vienna rectifier cannot feed the excess energy back to the grid via inverter storage; instead, it can only dissipate the excess energy through the load. Therefore, when the load on the Vienna rectifier suddenly decreases, the DC-side voltage response is very slow, leading to overvoltage. This also brings about the problem of designing the outer loop parameters of the Vienna rectifier. When the Vienna rectifier is running under light load with full load design parameters, the power that the load can consume is limited, and it cannot consume the extra capacitor energy generated by overshoot in time, which will lead to a large voltage overshoot under light load. If the Vienna rectifier is running under full load with light load design parameters, the outer loop PI parameter is small at this time, and it cannot quickly increase the DC side voltage.

[0003] To address the overvoltage issue caused by a sudden load reduction during Vienna rectifier operation, the traditional solution is to turn off the switching transistor and block the ripple generation when the DC side voltage becomes overvoltaged, entering a hiccup mode to wait for the load to consume the excess energy stored in the DC capacitor. However, this is accompanied by the problem of AC current ripple.

[0004] Therefore, there is a need to provide an outer loop control method that can simultaneously improve system response speed, reduce the difficulty of outer loop parameter design, and avoid current ripple caused by current discontinuity. Summary of the Invention

[0005] The purpose of this invention is to provide a wide load range operation control method for Vienna rectifiers in order to solve the above-mentioned problems.

[0006] The present invention achieves the above objectives through the following technical solutions:

[0007] A wide-load-range operation control method for a Vienna rectifier includes the following steps:

[0008] S1: Collect DC-side data from the Vienna rectifier, establish an energy transfer model based on the DC-side data, and calculate the DC-side load power P according to the energy transfer model. Load ;

[0009] S2: Regarding the DC-side load power P Load The filtered load power P is obtained after hybrid filtering. Load * (n);

[0010] S3: Based on the filtered load power P Load * The active current i is calculated from (n) and the DC side data. d * This enables control over the wide load range operation of the Vienna rectifier.

[0011] As a further optimization of the present invention, the DC-side data includes the upper capacitor voltage u on the DC side of the Vienna rectifier. C1 Lower capacitor voltage u C2 Three-phase output phase current i a i b i c Three-phase output phase voltage u a u b u c Three-phase grid voltage e a e b e c Grid-side filter inductor L s and parasitic resistance R s .

[0012] As a further optimization of the present invention, the specific steps in S1 of establishing an energy transfer model based on the DC-side data and calculating the DC-side load power according to the energy transfer model are as follows:

[0013] S11: Based on Kirchhoff's voltage law and the DC-side data, the voltage equation for the Vienna rectifier is as follows:

[0014]

[0015] Performing the Clark transformation on equation (1) yields the mathematical model in the αβ coordinate system:

[0016]

[0017] S12: Multiply the first row of equation (2) by i α The second row multiplied by i β By adding them together, we obtain the power transfer model of the Vienna rectifier:

[0018]

[0019] Wherein, the left side of equation (3) is the input power P obtained from the grid. in The first term on the right is the active power P consumed in the parasitic resistance of the inductor. S The second term is the charging power P of the filter inductor. L The third term is the DC-side absorption power P. DC ;

[0020] S13: Construct an energy transfer model for the Vienna rectifier based on equation (3):

[0021]

[0022] Among them, P in P is the total input power of the system. S P is the power of the parasitic resistance on the AC filter inductor. L P is the charging power of the filter inductor. DC The power absorbed on the DC side includes the charging power P of the capacitor. C and DC side load power P Load ;

[0023] S14: Obtain the DC-side load power P based on the energy transfer model. Load :

[0024]

[0025] As a further optimization of the present invention, obtaining the filtered load power in S2 specifically includes the following steps:

[0026] For the DC-side load power P Load The load power P after forgetting iterative filtering and sliding window filtering are obtained respectively. Load '(n) and load power after sliding window filtering The formula is as follows:

[0027] P′ Load (n)=(1-k)P Load (n)+kP′ Load (n-1) (6)

[0028]

[0029] (6) In the formula P Load (n) represents the DC-side load power before filtering in the current control cycle, P Load '(n) represents the load power after forgetting iterative filtering in the current control cycle, PLoad '(n-1) represents the filtered load power of the previous control cycle, and k is the forgetting factor; (7) where The load power is the result of sliding window filtering, and N is the window width.

[0030] The load power P after forgetting iterative filtering Load '(n) and load power after sliding window filtering The weighted average is used to obtain the filtered load power P. Load * (n):

[0031]

[0032] Where K is the proportionality coefficient.

[0033] As a further optimization of the present invention, the specific steps in S3 for calculating the active current based on the final filtered load power and the DC side data are as follows:

[0034] According to the upper capacitor voltage u C1 and the lower capacitor voltage u C2 Calculate the actual DC-side capacitor energy storage W C for:

[0035]

[0036] u dc =u C1 +u C2

[0037] Based on the given DC side voltage u dc * Calculate the given DC-side capacitor energy storage value W C * for:

[0038]

[0039] The given DC-side capacitor energy storage value W C * The actual DC-side capacitor energy storage W C and the final filtered load power P Load * (n) Substitute into the outer loop control structure to calculate the active current i d * :

[0040] P C * =k P (W C * -WC )+k I ∫(W C * -W C )dt

[0041]

[0042] Where, k P and k I These are the proportional and integral coefficients of the PI controller, P C * represents the output value of the PI controller.

[0043] The beneficial effects of this invention are as follows:

[0044] 1) The DC-side load power estimation algorithm and hybrid filtering algorithm proposed in this invention can accurately estimate the DC-side load power and effectively eliminate noise caused by sampling errors;

[0045] 2) The method proposed in this invention can achieve a fast DC-side voltage response speed across the entire load range;

[0046] 3) This invention requires no additional peripherals, has low system cost, and the control method is simple and easy to implement. Attached Figure Description

[0047] Figure 1 This is a flowchart of the method of the present invention;

[0048] Figure 2 This is the main circuit topology diagram of the Vienna rectifier of the present invention;

[0049] Figure 3 This is a block diagram of the outer loop control of the present invention;

[0050] Figure 4 The waveforms are for traditional voltage feedback control and capacitor energy storage feedback control;

[0051] Figure 5 The waveforms are those of traditional waveforms without load power feedback and waveforms with load power feedback. Detailed Implementation

[0052] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0053] A control method for wide-load-range operation of a Vienna rectifier includes the following steps:

[0054] Collect the voltage u of the upper capacitor on the DC side of the Vienna rectifier. C1 Lower capacitor voltage u C2 Three-phase output phase current i m (m = a, b, c), three-phase grid voltage e m (m=a,b,c), and based on the grid-side filter inductance and parasitic resistance of the Vienna rectifier, establish the energy transfer model of the Vienna rectifier, calculate the DC-side power, and obtain the processed data;

[0055] like Figure 2 The topology diagram is shown, where e a e b e c For the phase voltage of a three-phase power grid; i a i b i c For three-phase grid-connected current; u a u b u c The output voltage of the Vienna rectifier; u dc The total voltage on the upper and lower DC sides; L s and R s These are the grid-side filter inductor and its parasitic resistance, respectively.

[0056] From Kirchhoff's Voltage Law (KVL), a continuous mathematical model of Vienna can be obtained:

[0057]

[0058] Performing the Clark transformation on equation (1) yields the mathematical model in the αβ coordinate system:

[0059]

[0060] Multiply the first row of the equation by i α The second row multiplied by i β By adding them together, we obtain the power transfer model of the Vienna rectifier:

[0061]

[0062] In this equation, the left side represents the input power obtained from the grid, the first term on the right side represents the active power consumed in the parasitic resistance of the inductor, the second term represents the charging power of the filter inductor (which is zero when entering the steady state), and the third term represents the power absorbed by the rectifier (which is equal to the power transferred to the DC side when the losses on the switching transistor are not considered).

[0063] Further simplification of the above equation yields:

[0064]

[0065] Among them, P in P is the total input power of the system. S P is the power of the parasitic resistance on the AC filter inductor. L The charging power of the filter inductor, the power P flowing into the DC side DC It can be divided into two parts. The first part is the charging power P of the capacitor. C The second part is the power P consumed by the DC load. Load At this point, the energy exchange model for the Vienna rectifier is complete.

[0066] Using Vienna's energy exchange model, the power of the DC load can be estimated as follows:

[0067]

[0068] Since the calculation of inductor power and capacitor power involves differential terms, it is easily affected by sampling errors. Therefore, a hybrid filtering algorithm is used here to estimate the load power P. Load Perform filtering.

[0069] First, the load power estimated by equation (5) is subjected to forgetting iterative filtering:

[0070] P′ Load (n)=(1-k)P Load (n)+kP′ Load (n-1) (6)

[0071] In the formula, P Load (n) represents the load power before filtering in the current control cycle, P Load '(n) represents the load power after forgetting iterative filtering in the current control cycle, P Load '(n-1) represents the filtered load power in the previous control cycle, and k is the forgetting factor. Generally, the larger the value of k, the weaker the signal tracking ability, but the less sensitive it is to noise and the better the filtering effect; the smaller the value of k, the stronger the signal tracking ability, but the more sensitive it is to noise.

[0072] Then, a sliding window filter is applied to the load power estimated by equation (5):

[0073]

[0074] In the formula, P Load (n) represents the load power before filtering. Where N is the filtered load power, and N is the window width. The larger the window width, the better the filtering effect and the worse the tracking effect; the smaller the window width, the worse the filtering effect and the worse the tracking capability.

[0075] The load power P of the forgetting iterative filter Load '(n) and load power of sliding window filtering The weighted average yields the final load power filtering result P. Load * (n):

[0076]

[0077] Where K is the proportionality coefficient.

[0078] The DC side voltage u sampled dc The energy stored in the capacitor, W, can be calculated. C for:

[0079]

[0080] u dc =u C1 +u C2

[0081] Based on the given DC side voltage u dc * Calculate the given DC-side capacitor energy storage value W C * :

[0082]

[0083] Given a DC-side energy storage W C * Actual DC-side capacitor energy storage W C and estimated load power P Load * (n) Substitute Figure 3 The control loop shown can be used to obtain:

[0084] P C * =k P (W C * -W C )+k I ∫(W C * -W C )dt

[0085]

[0086] Among them W C * represents the given DC-side capacitor energy storage value calculated based on the given DC-side voltage, W. C k represents the actual DC-side capacitor energy storage value calculated based on the actual DC-side voltage sampling value. P and kI These are the proportional and integral coefficients of the PI controller, P C * represents the output value of the PI controller, P* Load i represents the estimated load power obtained after hybrid filtering. d * represents the final calculated active current value.

[0087] Based on the above content and combined Figure 3 As shown in the control loop, after adopting the proposed capacitor energy storage feedback and load power feedforward for Vienna, the change in load power no longer affects the loop of Vienna rectifier, which greatly improves the response speed of Vienna rectifier to load changes.

[0088] To verify the correctness of the above analysis, experimental results based on the parameters in the table below are presented.

[0089]

[0090] Figure 4 These are waveforms for traditional voltage feedback control and capacitor energy storage feedback control.

[0091] Figure 5 The waveforms are those of traditional power feedforward without load and those of power feedforward with load.

[0092] In summary, the proposed method can improve the load operating range of the Vienna rectifier to a certain extent and enhance its control performance.

[0093] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A wide-load-range operation control method for a Vienna rectifier, characterized in that: Includes the following steps: S1: Collect DC-side data from the Vienna rectifier, establish an energy transfer model based on the DC-side data, and calculate the DC-side load power according to the energy transfer model. P Load ; S2: Regarding the DC-side load power P Load The filtered load power is obtained after hybrid filtering. ; S3: Based on the filtered load power The active current is calculated from the DC side data. i d * This enables control over the wide load range operation of the Vienna rectifier.

2. The wide load range operation control method for a Vienna rectifier according to claim 1, characterized in that: The DC-side data includes the voltage of the upper capacitor on the DC side of the Vienna rectifier. u C1 Lower capacitor voltage u C2 Three-phase output phase current i a , i b , i c Three-phase output phase voltage u a , u b , u c Three-phase power grid voltage e a , e b , e c Grid-side filter inductor L s and parasitic resistance R s .

3. The wide load range operation control method for a Vienna rectifier according to claim 2, characterized in that: The specific steps for establishing an energy transfer model based on the DC-side data in step S1, and calculating the DC-side load power according to the energy transfer model, are as follows: S11: Based on Kirchhoff's voltage law and the DC-side data, the voltage equation for the Vienna rectifier is as follows: （1） Perform equation (1) Clark Transformation yields the mathematical model in the αβ coordinate system: （2） S12: Multiply the first row of equation (2) i α The second row multiplied i β By adding them together, we obtain the power transfer model of the Vienna rectifier: （3） Wherein, the left side of equation (3) represents the input power obtained from the power grid. P in The first item on the right is the active power consumed by the parasitic resistance of the inductor. P S The second item is the charging power of the filter inductor. P L The third item is the DC-side absorption power. P DC ; S13: Construct an energy transfer model for the Vienna rectifier based on equation (3): （4） in, P in The total input power of the system, P S The power of the parasitic resistance on the AC filter inductor. P L This refers to the charging power of the filter inductor. P DC Power absorbed on the DC side, including the charging power of the capacitor. P C and DC side load power P Load ; S14: Obtain the DC-side load power based on the energy transfer model. P Load : （5）。 4. The wide load range operation control method for a Vienna rectifier according to claim 3, characterized in that: The process of obtaining the filtered load power in S2 specifically includes the following steps: For the DC-side load power P Load Forgetting iterative filtering and sliding window filtering are performed separately to obtain the load power after forgetting iterative filtering. P Load ’(n) Load power after sliding window filtering The formula is as follows: （6） （7） (6) In the formula P Load (n) The current control cycle's DC-side load power before filtering. P Load ’(n) The load power after forgetting iterative filtering in the current control cycle. P Load ’(n-1) This represents the filtered load power from the previous control cycle. k Forgetting factor; (7) The load power after sliding window filtering. N The width of the window; Forgotten iterative filtering of load power P Load ’(n) Load power after sliding window filtering Perform a weighted average to obtain the filtered load power. : （8） in, K This is the proportionality coefficient.

5. The wide load range operation control method for a Vienna rectifier according to claim 4, characterized in that: The S3 is based on the filtered load power The specific steps for calculating the active current from the DC-side data are as follows: According to the upper capacitor voltage u C1 and the lower capacitor voltage u C2 Calculate the actual DC-side capacitor energy storage W C for: （9） Based on the given DC side voltage u dc * Calculate the given DC-side capacitor energy storage value W C * for: （10） The given DC-side capacitor energy storage value W C * The actual DC-side capacitor energy storage W C and the filtered load power The active current is calculated by substituting it into the outer loop control structure. i d * : （11） in, k P and k I They are respectively PI The proportional and integral coefficients of the controller, P C * for PI The output value of the regulator.

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