Multi-target AC-DC rectifier input current waveform gap shaping method

Abstract

The invention relates to a multi-target AC-DC rectifier input current waveform gap shaping method, which is suitable for an AC-DC rectifier of which the output voltage is smaller than the amplitude of the input voltage. In order to consider a plurality of indexes such as PF, THDi, each harmonic current limit value, CF, WF, AF, active compensation loss rate and the like, a gap is filled on the basis of single odd harmonic injection, and an input current reference implanted into an AC-DC rectifier input current control loop and an input current waveform compensation unit control loop is described in a form of m broken lines. By connecting specific end points, the input current reference can be quickly constructed, the requirements of PF, THDi and each harmonic current limiting value are met firstly, and then better CF, WF, AF or active compensation loss rate performance can be obtained through optimization.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for shaping AC-DC rectifier input current waveform to meet multiple target requirements, in particular, a method for shaping AC-DC rectifier input current waveform notch, which can adapt to the needs of different application occasions. BACKGROUND

[0002] When the alternating current is distorted, its harmonics not only cause the efficiency of power generation, transmission and utilization to decrease, electrical equipment to overheat, produce vibration and noise, insulation to age, service life to shorten, malfunction and burnout, but also interfere with the normal work of detection, communication, medical treatment, transportation and processing electrical equipment.

[0003] The more the alternating current deviates from the standard sinusoidal waveform, the more serious the harm of its harmonics. In order to control the harmonics, a series of specifications and standards related to power factor PF, total harmonic distortion of current THDi, harmonic current limit value, etc. have been introduced. The input current of AC-DC rectifier needs to meet the specifications and standards. The harmonic injection method is introduced into the input current control loop of AC-DC rectifier. By compensating for specific order harmonics, PF and THDi can be improved, and harmonic performance can be improved.

[0004] However, in addition to the harmonic performance, the AC-DC rectifier input current also needs to consider the indicators such as crest factor CF, waveform factor WF, average factor AF, etc. The CF value of the standard sinusoidal wave is , the WF value is , and the AF value is . Generally speaking, the lower the CF, WF and AF, the smaller the instantaneous current that the AC-DC rectifier needs to withstand, and the smaller the instantaneous power fluctuation. Therefore, the AC-DC rectifier input current waveform not only needs to meet multiple target values (such as PF, THDi, each harmonic current limit value, CF, WF, AF, etc.) at the same time, but also needs to be further optimized if there are multiple feasible solutions.

[0005] As for the AC-DC rectifier whose output voltage is less than the amplitude of the input voltage, its input current waveform has a "notch" (i.e. "dead zone") by nature, and has more harmonics, which needs to be treated more. SUMMARY

[0006] For the AC-DC rectifier whose output voltage is less than the amplitude of the input voltage, in order to overcome the shortcomings of the existing harmonic injection method which focuses on improving the harmonic performance, the present application proposes a method for shaping the notch of the AC-DC rectifier input current waveform with multiple targets.

[0007] As for the input voltage , , Vacm is the amplitude, fac is the frequency, Vdc is the output voltage, and t is the time , h is a positive odd number greater than 1, the application of the period Tac = 1 / fac, taking into account PF, THDi, each harmonic current limit, CF, WF, AF, active compensation rate and other indicators, according to an embodiment of the application A kind of multi-target AC-DC rectifier input current waveform gap shaping method, comprising the following steps:

[0008] According to the requirements of PF, THDi, each harmonic current limit, the ratio limit of each harmonic current and fundamental current is corrected, for example: the highest one of PF, THDi, each harmonic current limit can be taken to correct the ratio limit of each harmonic current and fundamental current, and the ratio limit of each harmonic current and fundamental current obtained can guarantee to meet the requirements of PF, THDi and each harmonic current limit;

[0009] Constructing harmonic injection current normalized by fundamental , parameter b satisfies: the ratio of h harmonic current of iac_norm(t)·rect(t) and fundamental current is less than the ratio of h harmonic current and fundamental current,

[0010] Rectangular window function , n is an integer,

[0011] Time t1b satisfies And t1b < tr;The initial value of h can be set to the harmonic order corresponding to the larger value of the ratio limit of each harmonic current and fundamental current, generally 3, 5, 7;

[0012] Based on the harmonic injection current normalized by fundamental iac_norm(t) and the rectangular window function rect(t), the input current reference iac_ref(t) is constructed, which has a period equal to Tac, is centrally symmetric at time t = Tac / 2, and is y-axis symmetric at t = Tac / 4, Period:

[0013] The input current reference iac_ref(t) is a m-segment polyline, m is a positive integer and , the m-segment polyline is sequentially connected in time order as follows (m+1) endpoints: (0, 0), (t1a, 0), (t1a, k·iac_norm(t1a)), (t1b, k·iac_norm(t1b)), (t1b, iac_norm(t1b)), (tr, iac_norm(tr)), (Tac / 4, iac_norm(tr)) and any (m-6) points conforming to (tj, iac_norm(tj)), time ​j is a positive integer and t1b < tj < tr, 0 < k < 1, 0 < t1a < t1b;

[0014] If the ratio of each harmonic current to the fundamental current of the input current reference iac_ref(t) is less than the limit of the ratio of each harmonic current to the fundamental current, then it is incorporated into the input current control loop of the AC-DC rectifier, for example, as the input current reference. Simultaneously, the straight line segment from (t1a, k·iac_norm(t1a)) to (t1b, k·iac_norm(t1b)) of the input current reference iac_ref(t) is incorporated into the control loop of the input current waveform compensation unit, for example, as the input current reference for input current waveform shaping. Otherwise, adjust parameters b, t1a, k, m, and h until the ratio of each harmonic current to the fundamental current of the input current reference iac_ref(t) is less than the limit of the ratio of each harmonic current to the fundamental current. The input current waveform compensation unit is a controllable AC current source that provides both active and reactive power compensation, and is connected in parallel to the input terminal of the AC-DC rectifier (see...). Figure 1 This is used to compensate for the input current gap, such as the combination of rectifier circuit and lossy compensation unit a disclosed in invention patent ZL 201910354882.4. When adjusting the above parameters, trial and error and disturbance methods can be used.

[0015] According to an embodiment of the present invention, in order to improve the performance of the input current CF, WF, AF of the AC-DC rectifier and the active power compensation loss rate P_com / Pac, an optimization function f_opt(CF, WF, AF, P_com / Pac) can be defined, which includes the active power compensation loss rate. Active power For example: f_opt(CF, WF, AF, P_com / Pac) = CF·(P_com / Pac) or WF·(P_com / Pac) or AF·(P_com / Pac), the optimal value is the minimum value;

[0016] Replace (tr, iac_norm(tr)) with (tra, iac_norm(tra)) and replace (Tac / 4, iac_norm(tr)) with (Tac / 4, iac_norm(tra)), while keeping the other endpoints unchanged. At time tra, t1b < tra < Tac / 4.

[0017] The reconstructed input current reference iac_ref(t) still has a period equal to Tac, remains centrally symmetric at time t = Tac / 2, and remains y-symmetric at t = Tac / 4. period:

[0018] The input current reference iac_ref(t) is still a single m-segment polyline, where m is a positive integer and The m segments of the broken line are connected sequentially in time to the following (m+1) endpoints: (0, 0), (t1a, 0), (t1a, k·iac_norm(t1a)), (t1b, k·iac_norm(t1b)), (t1b, iac_norm(t1b)), (tra, iac_norm(tra)), (Tac / 4, iac_norm(tra)) and any (m-6) points that satisfy (tj, iac_norm(tj)), at time... j is a positive integer and t1b < tj < tra, 0 < k < 1, 0 < t1a < t1b;

[0019] Based on the requirement that the ratio of each harmonic current to the fundamental current still needs to be satisfied according to the input current reference iac_ref(t), the range of values ​​for tra is determined; the initial value of tra can be set to tr; by changing tra, the range of values ​​for tra can be obtained by stepping.

[0020] Within the range of tra, the iac_ref(t) corresponding to the optimal value of the optimization function is taken as the optimized input current reference iac_ref_opt(t). The optimized input current reference iac_ref_opt(t) is implanted into the input current control loop of the AC-DC rectifier, such as: as the input current reference. At the same time, the straight line segment from (t1a, k·iac_norm(t1a)) to (t1b, k·iac_norm(t1b)) of the optimized input current reference iac_ref_opt(t) is implanted into the control loop of the input current waveform compensation unit, such as: as the input current reference, used for input current waveform shaping.

[0021] The beneficial effects of this invention are mainly reflected in the following aspects: it can take into account multiple indicators such as PF, THDi, harmonic current limits, CF, WF, AF, and active power compensation loss rate; it "fills the gap" based on the h-th harmonic injection; and it uses an m-segment piecewise linear form to describe the input current reference implanted in the AC-DC rectifier input current control loop and the input current waveform compensation unit control loop. In digital control, storing one m-segment piecewise linear line only requires information from (m+1) endpoints, occupying a small number of registers. Moreover, in the process of quickly determining the input current reference, there are multiple optional parameter combinations, providing room for optimization. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This invention relates to an AC-DC rectifier with a parallel input current waveform compensation unit on the input side.

[0024] Figure 2 This is a flowchart of Embodiment 1 of the present invention;

[0025] Figure 3 This is Embodiment 1 of the present invention. A schematic diagram of (t) and iac_norm(t)·rect(t) (taking h = 5);

[0026] Figure 4 This is a spectrum of the ratio of each harmonic current to the fundamental current of iac_norm(t)·rect(t) in Embodiment 1 of the present invention (with h = 5).

[0027] Figure 5 This is a schematic diagram of iac_norm(t)·rect(t) and iac_ref(t) in Embodiment 1 of the present invention (taking h = 5, b = 0.14, t1b ≈ 0.0835·Tac, t1a ≈ 0.05·Tac, k = 0.5, m = 6).

[0028] Figure 6 This is a spectrum of the ratio of each harmonic current to the fundamental current of iac_ref(t) in Embodiment 1 of the present invention (with h = 5, b = 0.14, t1b ≈ 0.0835·Tac, t1a ≈ 0.05·Tac, k = 0.5, m = 6).

[0029] Figure 7 This is a schematic diagram of iac_norm(t)·rect(t) and iac_ref(t) in Embodiment 1 of the present invention (taking h = 5, b = 0.14, t1b ≈ 0.0835·Tac, t1a ≈ 0.05·Tac, k = 0.5, m = 7).

[0030] Figure 8 This is a spectrum of the ratio of each harmonic current to the fundamental current of iac_ref(t) in Embodiment 1 of the present invention (with h = 5, b = 0.14, t1b ≈ 0.0835·Tac, t1a ≈ 0.05·Tac, k = 0.5, m = 7).

[0031] Figure 9 is the optimized sub - flow chart of Embodiment 2 of the present invention;

[0032] Figure 10 is a schematic diagram of iac_norm(t)·rect(t) and iac_ref_opt(t) in Embodiment 2 of the present invention (taking h = 5, b = 0.14, t1b ≈ 0.0835·Tac, t1a ≈ 0.05·Tac, k = 0.5, m = 7);

[0033] Figure 11 is the spectrum diagram of the ratio of each harmonic current of iac_ref_opt(t) to the fundamental current in Embodiment 2 of the present invention (taking h = 5, b = 0.14, t1b ≈ 0.0835·Tac, t1a ≈ 0.05·Tac, k = 0.5, m = 7). Detailed implementation manners

[0034] The following will specifically describe the preferred embodiments of the present invention with reference to the accompanying drawings. The accompanying drawings form a part of this application and are used together with the embodiments of the present invention to explain the principle of the present invention, rather than to limit the scope of the present invention.

[0035] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of the present invention. The phrase appears at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0036] Embodiment 1

[0037] The Buck PFC circuit is an AC - DC rectifier with an output voltage less than the amplitude of the input voltage, and there are congenital gaps in the waveform of its input current. Taking it as an example, its input voltage is , the output voltage Vdc < Vacm, Vacm is the amplitude, and fac is the frequency. When vac(t) < Vdc, the circuit does not work, and the corresponding input current is 0, that is, there is a dead zone. If it is required to satisfy: power factor PF >= PF0, total harmonic distortion rate of current THDi ≤ THDi0, effective value of n - th harmonic current Iacn ≤ Iacn0, where n is a positive integer and n > 1, 0 ≤ PF0 ≤ 1, THDi0 ≥ 0%, Iacn0 ≥ 0, it is necessary to connect an input current waveform compensation unit in parallel on the input side, such as Figure 1As shown. The input current waveform compensation unit is used to compensate for the input current gap, providing both active and reactive power compensation. A suitable input current waveform compensation unit is, for example, the combination of the rectifier circuit and loss compensation unit a disclosed in invention patent ZL 201910354882.4.

[0038] For a Buck PFC circuit with a parallel input current waveform compensation unit on the input side, such as Figure 2 As shown, a method for defining the input current waveform gap of a multi-objective AC-DC rectifier includes the following steps:

[0039] The relationship between THDi and Iacn satisfies equation (1), where Iac1 is the effective value of the fundamental current; when the phase factor DPF in PF is 1, the relationship between THDi and PF satisfies equation (2).

[0040] (1)

[0041] (2)

[0042] Based on equations (1) and (2), after conversion, the most stringent requirement among PF ≥ PF0, THDi ≤ THDi0, and Iacn ≤ Iacn0 is taken to correct the limit value of the ratio of each harmonic current to the fundamental current, Iacn_lim / Iac1. After correction, Iacn_lim ≤ Iacn0.

[0043] like Figure 3 and 4 As shown, a harmonic injection current normalized to the fundamental frequency is constructed. The parameter b satisfies the following condition: the ratio of the h-th harmonic current to the fundamental current of iac_norm(t)·rect(t) is less than 1 / 2. The ratio of the h-th harmonic current to the fundamental current.

[0044] Rectangular window function n is an integer.

[0045] Time t1b satisfies And t1b < tr; the initial value of h can be set to the harmonic order corresponding to the larger value among the limit values ​​of the ratio of each harmonic current to the fundamental current, which is generally 3, 5, or 7.

[0046] like Figure 5 As shown, based on the fundamental-normalized harmonic injection current and the rectangular window function, an input current reference iac_ref(t) is constructed. Its period is equal to Tac, and it is centrally symmetric at t = Tac / 2 and y-symmetric at t = Tac / 4. period:

[0047] The input current reference iac_ref(t) is a piecewise linear function with m segments, where m is a positive integer and The m-segment polylines are connected sequentially in time to the following (m+1) endpoints: (0, 0), (t1a, 0), (t1a, k·iac_norm(t1a)), (t1b, k·iac_norm(t1b)), (t1b, iac_norm(t1b)), (tr, iac_norm(tr)), (Tac / 4, iac_norm(tr)) and any (m-6) points conforming to (tj, iac_norm(tj)), at time... j is a positive integer and t1b < tj < tr, 0 < k < 1, 0 < t1a < t1b;

[0048] If the ratio of each harmonic current to the fundamental current of the input current reference iac_ref(t) is less than the limit of the ratio of each harmonic current to the fundamental current, then it is incorporated into the input current control loop of the Buck PFC circuit as the input current reference. Furthermore, the straight line segment from (t1a, k·iac_norm(t1a)) to (t1b, k·iac_norm(t1b)) is incorporated into the control loop of the input current waveform compensation unit as the input current reference for input current waveform shaping. Otherwise, adjust parameters b, t1a, k, m, and h until the ratio of each harmonic current to the fundamental current of the input current reference iac_ref(t) is less than the limit of the ratio of each harmonic current to the fundamental current. Trial and error methods and perturbation methods can be used to adjust these parameters.

[0049] For clarity, assume Vdc / Vacm = 0.5, PF0 = 0.9, THDi0 = 20%, and that all harmonic current limits comply with the Class C standard of IEC 61000-3-2. Calculations show that THDi ≤ 20% is the most stringent of the three, with the corrected result as follows: Iac3_lim / Iac1 = 0.07. The remaining ratio limits remain the same as the Class C standard of IEC 61000-3-2.

[0050] Let h = 5, b = 0.14, t1b ≈ 0.0835·Tac, t1a ≈ 0.05·Tac, k = 0.5, m = 6, as follows Figure 6 As shown, the ratios of each harmonic current to the fundamental current in the obtained iac_ref(t) are all less than the limit for the ratio of each harmonic current to the fundamental current, and PF ≈ 0.9901, THDi ≈ 14.17%, CF ≈ 1.394, WF ≈ 1.177, AF ≈ 1.642, and P_com / Pac = 2.964%, which meet the requirements.

[0051] Let h = 5, b = 0.14, t1b ≈ 0.0835·Tac, t1a ≈ 0.05·Tac, k = 0.5, and m = 7. Figure 7 The diagram shows iac_norm(t)·rect(t) and iac_ref(t); as shown Figure 8 As shown, the ratios of each harmonic current to the fundamental current in the obtained iac_ref(t) are all less than the limits for the ratio of each harmonic current to the fundamental current: PF ≈ 0.9904, THDi ≈ 13.96%, CF ≈ 1.413, WF ≈ 1.179, AF ≈ 1.666, and P_com / Pac = 3.002%, which also meets the requirements. However, except for THDi, the performance of the other parameters is slightly worse than that of m = 6.

[0052] Other parameter combinations (h, b, t1b, t1a, k, m) have similar effects, which will not be elaborated further.

[0053] For input current waveform shaping, the above-mentioned iac_ref(t) that meets the requirements can be implanted into the input current control loop of the Buck PFC circuit as the input current reference. At the same time, its straight line segment from (t1a, k·iac_norm(t1a)) to (t1b, k·iac_norm(t1b)) can be implanted into the control loop of the input current waveform compensation unit as the input current reference.

[0054] Example 2

[0055] Using a parameter combination (h = 5, b = 0.14, t1b ≈ 0.0835·Tac, t1a ≈ 0.05·Tac, k = 0.5, m = 6), Example 1 is optimized to improve the performance of CF, WF, AF, and active power compensation loss rate. An optimization function f_opt(CF, WF, AF, P_com / Pac) = CF·(P_com / Pac) is defined, with its optimized value being the minimum.

[0056] like Figure 9 As shown, a suitable method for defining the input current waveform gap of an AC-DC rectifier with multiple objectives includes the following optimization steps:

[0057] Replace (tr, iac_norm(tr)) with (tra, iac_norm(tra)) and replace (Tac / 4, iac_norm(tr)) with (Tac / 4, iac_norm(tra)), while keeping the other endpoints unchanged. At time tra, t1b < tra < Tac / 4.

[0058] The reconstructed input current reference iac_ref(t) still has a period equal to Tac, remains centrally symmetric at time t = Tac / 2, and remains y-symmetric at t = Tac / 4. period:

[0059] iac_ref(t) is still a polyline with m segments, where m is a positive integer and The m segments of the broken line are connected sequentially in time to the following (m+1) endpoints: (0, 0), (t1a, 0), (t1a, k·iac_norm(t1a)), (t1b, k·iac_norm(t1b)), (t1b, iac_norm(t1b)), (tra, iac_norm(tra)), (Tac / 4, iac_norm(tra)) and any (m-6) points that satisfy (tj, iac_norm(tj)), at time... j is a positive integer and t1b < tj <tra,0 < k < 1,0 < t1a < t1b;

[0060] Based on the requirement that the ratio of each harmonic current to the fundamental current still needs to be satisfied by iac_ref(t), the range of values ​​for tra is determined; the initial value of tra can be set to tr; by changing tra, the range of values ​​for tra can be obtained by stepping.

[0061] Within the range of tra, the iac_ref(t) corresponding to the optimal value of the optimization function is taken as the optimized input current reference iac_ref_opt(t), and it is implanted into the input current control loop of the Buck PFC circuit as the input current reference. At the same time, the straight line segment from (t1a, k·iac_norm(t1a)) to (t1b, k·iac_norm(t1b)) is implanted into the control loop of the input current waveform compensation unit as the input current reference for input current waveform shaping.

[0062] Figure 10 The figures shown are iac_norm(t)·rect(t) and iac_ref_opt(t), where tra is approximately 0.2085·Tac; Figure 11As shown, the optimal value of f_opt(CF, WF, AF, P_com / Pac) is 4.117%. The ratios of each harmonic current to the fundamental current in the obtained iac_ref_opt(t) are all less than the limits for the ratios of each harmonic current to the fundamental current: PF ≈ 0.9900, THDi ≈ 14.24%, CF ≈ 1.427, WF ≈ 1.181, AF ≈ 1.686, and P_com / Pac = 2.885%, which meets the requirements. Moreover, the performance of P_com / Pac is superior to that of Example 1. It can be implanted into the input current control loop and the control loop of the input current waveform compensation unit of the Buck PFC circuit as the input current reference and is shaped by the input current waveform.

[0063] In addition to Buck PFC circuits, this invention is also applicable to other AC-DC rectifiers with inherent gaps in their input current waveforms.

[0064] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-objective method for defining the input current waveform gap in an AC-DC rectifier, applicable to AC-DC rectifiers where the output voltage is less than the input voltage amplitude, and whose input voltage... ,in, Vacm is the amplitude, fac is the frequency, Vdc is the output voltage, and time is... The method is characterized by the following steps: h is a positive odd number greater than 1, and the period Tac = 1 / fac. Based on the requirements of PF, THDi, and the limits of each harmonic current, the limit of the ratio of each harmonic current to the fundamental current is modified. Constructing a harmonic injection current normalized to the fundamental frequency b satisfies: the ratio of the h-th harmonic current to the fundamental current of iac_norm(t)·rect(t) is less than 1 / 2. The ratio of the h-th harmonic current to the fundamental current. Among them, the rectangular window function n is an integer. Time t1b satisfies And t1b < tr; Construct an input current reference iac_ref(t) with a period equal to Tac, exhibiting central symmetry at time t = Tac / 2 and y-symmetry at t = Tac / 4. period; The input current reference iac_ref(t) is a piecewise linear function with m segments, where m is a positive integer and The m-segment polylines are connected sequentially in time to the following (m+1) endpoints: (0, 0), (t1a, 0), (t1a, k·iac_norm(t1a)), (t1b, k·iac_norm(t1b)), (t1b, iac_norm(t1b)), (tr, iac_norm(tr)), (Tac / 4, iac_norm(tr)) and any (m-6) points conforming to (tj, iac_norm(tj)), at time... j is a positive integer and t1b < tj <tr,0 < k < 1,0 < t1a < t1b; If the ratio of each harmonic current to the fundamental current of the input current reference iac_ref(t) is less than the limit of the ratio of each harmonic current to the fundamental current, then it is implanted into the input current control loop of the AC-DC rectifier. At the same time, the straight line segment from (t1a, k·iac_norm(t1a)) to (t1b, k·iac_norm(t1b)) of the input current reference iac_ref(t) is implanted into the control loop of the input current waveform compensation unit; otherwise, adjust parameters b, t1a, k, m and h until the ratio of each harmonic current to the fundamental current of the input current reference iac_ref(t) is less than the limit of the ratio of each harmonic current to the fundamental current. The input current waveform compensation unit is a controllable AC current source that provides both active and reactive power compensation and is connected in parallel to the input terminal of the AC-DC rectifier.

2. The method for determining the input current waveform gap of a multi-objective AC-DC rectifier as described in claim 1, characterized in that, It also includes an initialization method for h, which sets the initial value of h to the harmonic order corresponding to the larger of the ratio limits between each harmonic current and the fundamental current.

3. The method for determining the input current waveform gap of a multi-objective AC-DC rectifier as described in claim 1 or 2, characterized in that, It also includes an optimization method, which replaces (tr, iac_norm(tr)) with (tra, iac_norm(tra)) and (Tac / 4, iac_norm(tra)) with (Tac / 4, iac_norm(tr)) based on the input current reference iac_ref(t), while keeping the other endpoints unchanged, and at time tra, t1b < tra < Tac / 4; The reconstructed input current reference iac_ref(t) still has a period equal to Tac, remains centrally symmetric at time t = Tac / 2, and remains y-symmetric at t = Tac / 4. period; The input current reference iac_ref(t) is still a single m-segment polyline, where m is a positive integer and The m segments of the broken line are connected sequentially in time to the following (m+1) endpoints: (0, 0), (t1a, 0), (t1a, k·iac_norm(t1a)), (t1b, k·iac_norm(t1b)), (t1b, iac_norm(t1b)), (tra, iac_norm(tra)), (Tac / 4, iac_norm(tra)) and any (m-6) points that satisfy (tj, iac_norm(tj)), at time... j is a positive integer and t1b < tj < tra, 0 < k < 1, 0 < t1a < t1b; Based on the requirement that the ratio of each harmonic current to the fundamental current still needs to be satisfied according to the input current reference iac_ref(t), the range of values ​​for tra is determined. Within the range of tra, the iac_ref(t) corresponding to the optimal value of the optimization function is taken as the optimized input current reference iac_ref_opt(t), and it is implanted into the input current control loop of the AC-DC rectifier. At the same time, the straight line segment from (t1a, k·iac_norm(t1a)) to (t1b, k·iac_norm(t1b)) of iac_ref_opt(t) is implanted into the control loop of the input current waveform compensation unit. The variables of the optimization function include any combination of CF, WF, AF, and the active power compensation loss rate P_com / Pac, and the active power compensation loss. Active power .

4. The method for determining the input current waveform gap of a multi-objective AC-DC rectifier as described in claim 3, characterized in that, It also includes an initialization method for time tra, which sets the initial value of time tra equal to time tr.

Images