A contactless AC voltage stabilizer voltage regulation circuit

Abstract

The present invention relates to the technical field of voltage regulators, and discloses a contactless AC voltage regulator voltage stabilizing circuit, which solves the technical problems of circulating current, back pressure and low compensation accuracy existing in the voltage stabilizing circuits of traditional voltage regulators. The circuit includes: a compensation transformer TBa, a voltage regulating transformer Tvva, thyristors S1-S10, a three-port inductor DLa and a current sensor LCa; one ends of the thyristors S1 and S4 are commonly electrically connected to one end of the primary coil of the compensation transformer TBa, and one ends of the thyristors S2 and S3 are commonly electrically connected to the other end of the primary coil of the compensation transformer TBa; the other ends of the thyristors S1 and S2 are commonly electrically connected to the negative electrode of the voltage input end and the voltage output end, and the other ends of the thyristors S3 and S4 are commonly electrically connected to the middle connection end of the three-port inductor DLa. According to the above technical solution, a novel AC voltage regulator circuit design is designed to solve the problems of circulating current, back pressure and compensation accuracy, so as to achieve the purpose of high reliability and higher compensation accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of voltage regulators, and more specifically, it relates to a contactless AC voltage regulator circuit. Background Art

[0002] A voltage regulator refers to a device designed to automatically maintain a constant voltage in electronic engineering.

[0003] As Figure 1 shown Figure 1 The voltage regulator circuit of [[ ]] is the principle of the representative first-generation contactless voltage regulator circuit in the prior art, which consists of a voltage regulating transformer TB2 (secondary transformer), a thyristor module S0-10, and a drive circuit. TB2 (secondary transformer) is a multi-tap autotransformer, and each tap is controlled by 1 group of several thyristor switches. Thyristor switches S1~S5 are compensation voltage magnitude switching switches; thyristor switches S0, S7, S8, S9, and S10 are zero compensation, positive compensation, and negative compensation switching switches; by changing the conduction states of the thyristor switches S0~S10, the magnitude and direction of the voltage on the primary coil of the compensation transformer TB1 can be changed, so that a compensation voltage △U with variable magnitude and direction can be generated on the secondary of TB1. When the input voltage Ui n changes or the output voltage Uout changes due to load changes, the intelligent control circuit adjusts and switches the thyristor switches (S0~S10), thereby automatically maintaining the stability of the output voltage.

[0004] According to Figure 1 the circuit diagram of [[ ]] and the above analysis, the first-generation contactless voltage regulator circuit can provide a total of 11 levels of step-by-step compensation superposition of positive 5 levels, 0 compensation, and negative 5 levels. Its disadvantages are: ① Only eleven levels of step-by-step compensation can be completed by using ten thyristor switches; ② The compensation voltage regulation accuracy is not high, up to ±2.5%, that is, the mean value of the conventional phase voltage ±7-9V; ③ There is circulating current, resulting in poor output waveform. Circulating current means that: As Figure 1 known, the current flowing through the thyristors (S0-S10) is synchronized with the main circuit of the voltage regulator, and the current zero-crossing point depends on the actual load current in the main circuit of the voltage regulator. The loads of the voltage regulator are users in the vast market, and the load characteristics include inductive, resistive, capacitive, non-linear, etc. There are many situations such as lag and lead in the current zero-crossing point. When the current zero-crossing point lags, there will be a short-term circulating current when the thyristors (S0-S10) switch between on / off. The actual product uses an inductor to limit the current. When the inductive load is too heavy or there is a load startup impact, the thyristor fuse will be blown due to the surge current, and in severe cases, there is also a hidden danger of burning the secondary transformer.

[0005] As Figure 2 shown Figure 2 the voltage regulator circuit of [[ ]] is the principle of the representative second-generation contactless voltage regulator circuit in the prior art Figure 2The voltage stabilizing circuit uses three compensation transformers T1 / T2 / T3 with different turns ratios. In conventional products, they are respectively made into AC220V:5V, AC220V:10V, and AC220V:20V, which is called the 1-2-4 structure in the field. The secondary windings of the compensation transformers are connected in series in the main circuit, and the positive compensation, zero compensation, and negative compensation of T1 / T2 / T3 are respectively achieved by the on and off of the thyristor (S1-S8) switch combination. The secondary compensation voltages ΔU1 of T1 are +5V, OV, -5V respectively; the secondary compensation voltages ΔU2 of T2 are +10V, OV, -10V respectively; the secondary compensation voltages ΔU3 of T3 are +20V, OV, -20V respectively; the output phase voltage Uo of the voltage regulator is equal to the synthesis of the input phase voltage Ui and the secondary compensation voltages of the compensation transformers T1 / T2 / T3, that is: Uo = Ui ± ΔU1 ± ΔU2 ± ΔU3. After intelligent calculation by the single-chip microcomputer, the thyristor (S1-S8) is given corresponding trigger pulse signals, and the required thyristor on-off combination can be obtained, so as to obtain the required compensation voltage, and finally achieve the purpose of stabilizing the output voltage. Figure 2 The voltage stabilizing circuit is generally known as the superposition principle of 1, 2, 4 (+7, 0, -7 for a total of 15 levels).

[0006] The disadvantages of this voltage regulator circuit are as follows: ① There is no circulating current but there is a miss, that is, there is a reverse voltage. Having a reverse voltage means that: Figure 2It can be known that the current flowing through the thyristors (S1 - S8) is synchronized with the main circuit of the voltage regulator. The zero-crossing point of the current depends on the actual load current in the main circuit of the voltage regulator, and the load of the voltage regulator is the vast number of market users. The load characteristics include inductive, resistive, capacitive, non-linear, etc. There are many situations such as lag and lead in the zero-crossing point of the current. When the thyristor (S1 - S8) combination switches between on and off, it is necessary to ensure that the previous group of thyristors is completely turned off before turning on the next group of thyristors to be turned on. Therefore, this series of products all adopt the method of delaying about 90 degrees (5 milliseconds) after the voltage passes through zero and then turning on the next group of thyristor combinations (commonly known as voltage zero-crossing delay switching). And this switching method causes an open-circuit process of 0 - 5 milliseconds (inductive or resistive load), or even 5 - 10 milliseconds (pure capacitive load) in the primary of the compensation transformers T1 / T2 / T3. According to the electromagnetic induction principle of the transformer: this open circuit will cause a large voltage drop in the secondary of the compensation transformer (the output voltage of the voltage regulator will drop or rise instantaneously), and at the same time, there will be a very high reverse voltage in the primary (similar to the open circuit of the secondary of a current transformer), and many other hazards. Therefore, actual products need to take measures such as shunting resistance-capacitance absorption and varistors in parallel in the primary of the compensation transformers T1 / T2 / T3. However, due to the uncertainty of the load size of the voltage regulator (such as the starting impact current of the motor, the inrush current of the shunt capacitor for reactive power compensation, etc.) and the load characteristics (inductive, resistive, capacitive, non-linear), abnormal situations such as UPS alarms, frequency converter alarms or even shutdowns, data loss in the data center, abnormal conditions of radio and television transmitting equipment, and flashing of lighting equipment will still occur occasionally in the actual product application due to the instantaneous drop or rise of the output voltage waveform of the voltage regulator, and in severe cases, the equipment may even be damaged. ② The compensation voltage regulation accuracy is not high, up to ±2%, that is, the mean value of the conventional phase voltage ±7V; ③ The output waveform is poor, there are mutations, and the mutations are obvious when switching between 3 / 4 gears, and there are instantaneous flashes and vibrations.

[0007] Therefore, analyzing the main existing technical representatives of the voltage regulator above, they either have circulating current or have back pressure, with low reliability in use. At the same time, their compensation level is not high, resulting in insufficient compensation accuracy. Therefore, there is room for improvement. Summary of the Invention

[0008] Aiming at the technical problems of the voltage stabilizing circuit of the traditional voltage regulator in the background technology, such as having circulating current, having back pressure, and low compensation accuracy, the present invention designs a new type of AC voltage regulator circuit design to solve the problems of circulating current, back pressure, and compensation accuracy, so as to achieve the purpose of high reliability and higher compensation accuracy.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A contactless AC voltage regulator voltage stabilizing circuit includes: compensation transformer TBa, voltage regulating transformer Tvva, thyristors S1 - S10;

[0011] It also includes: a three-port inductor DLa and a current sensor LCa;

[0012] A compensation transformer TBa,

[0013] One end of the secondary coil of the compensation transformer TBa is connected to the positive pole of the voltage input terminal, and the other end of the secondary coil of the compensation transformer TBa is connected to the positive pole of the voltage output terminal;

[0014] The primary coil of the compensation transformer TBa is electrically connected through several of the thyristors S1 - S10, the control action of the three-port inductor DLa, the current sensor LCa, and the secondary coil of the voltage regulating transformer Tvva to obtain voltage compensation values of different levels;

[0015] A voltage regulating transformer Tvva,

[0016] The secondary coil of the voltage regulating transformer Tvva is a multi-tap autotransformer;

[0017] Thyristors S1 - S10,

[0018] One end of thyristor S1 and thyristor S4 is commonly electrically connected to one end of the primary coil of the compensation transformer TBa, and one end of thyristor S2 and thyristor S3 is commonly electrically connected to the other end of the primary coil of the compensation transformer TBa;

[0019] The other ends of thyristor S1 and thyristor S2 are commonly electrically connected to the negative poles of the voltage input terminal and the voltage output terminal, and the other ends of thyristor S3 and thyristor S4 are commonly electrically connected to the middle connection terminal of the three-port inductor DLa;

[0020] One end of thyristors S8, S9, and S10 is commonly electrically connected to one end of the three-port inductor DLa, and the other ends of thyristors S8, S9, and S10 are respectively electrically connected to the 2 / 10, 6 / 10, and 10 / 10 positions of the voltage regulating transformer Tvva;

[0021] One end of thyristors S5, S6, and S7 is commonly electrically connected to the other end of the three-port inductor DLa, and the other ends of thyristors S5, S6, and S7 are respectively electrically connected to the 0 / 10, 4 / 10, and 8 / 10 positions of the voltage regulating transformer Tvva;

[0022] A current sensor LCa is electrically connected between the parallel connection end of thyristors S3 and S4 and the middle connection terminal of the three-port inductor DLa;

[0023] Thyristor S3 is electrically connected to one end of the primary coil of the compensation transformer TBa where it is connected to thyristors S1 and S4 through a control switch QJa.

[0024] Through the above technical solutions:

[0025] It can perform a total of 21 levels of step-by-step compensation superposition principle for +10 levels, 0, and -10 levels;

[0026] The thyristor switches S5~S10 are compensation voltage magnitude switching switches, and the thyristor switches S1~S4 are zero compensation, positive compensation, and negative compensation switching switches. By changing the conduction states of the thyristor switches, the magnitude and direction of the voltage on the primary coil of the compensation transformer TBa can be changed, so that a compensation voltage △U with variable magnitude and direction can be generated on the secondary of TBa.

[0027] In the primary compensation circuit of the compensation transformer TBa ( Figure 3 at the position of the neutral line number 48), a current transformer (permanent magnet current sensor) LCa is added. The zero-crossing point of the synchronous current signal of the current transformer (permanent magnet current sensor) LCa is used as the synchronous signal for the non-contact AC switch switching of the thyristors (S1-10), ensuring that the non-contact voltage regulator accurately turns on the next set of thyristor combinations to be turned on after the previous set of thyristor combinations is naturally turned off, so as to ensure seamless, non-backpressure, and non-circulating smooth switching of the compensation voltage on the primary of the voltage regulator compensation transformer TB, and ultimately ensure that the output voltage waveform of the voltage regulator is intact, without drop, mutation, or distortion.

[0028] Due to the use of the current zero-crossing triggering method, step-by-step superposition switching compensation voltage regulation, safety and smoothness, no interference to the power grid, and stable output voltage regulation; it truly and effectively improves the dynamic stability of the voltage regulator and eliminates the common-mode current impact generated by the non-contact switch and the damage to the system and devices caused by overvoltage. It has strong instantaneous overload capacity, thus greatly improving the safety and reliability of the system operation.

[0029] The voltage regulating transformer Tvva is an ordinary single-phase autotransformer. When the input is single-phase AC220V, the output has 6 output combinations of 0V, AC60V, AC120V, AC180V, AC240V, and AC300V. The thyristor S5-S10 AC switch combination is connected in an equal-ratio cross manner to the corresponding output positions of the voltage regulating transformer Tvva. Specific connection method: S5 is connected to 0V, S6 is connected to AC120V, S7 is connected to AC240V, and then the other ends of the three thyristor S5 / S6 / S7 AC switches are connected in parallel and then connected to the head end of the three-port inductor DL; S8 is connected to 60V, S9 is connected to AC180V, S10 is connected to AC300V, and then the other ends of the three thyristor S8 / S9 / S10 AC switches are connected in parallel and then connected to the tail end of the three-port inductor DL; the middle end of the three-port inductor DL is connected to the parallel connection of the commutation thyristors S3 and S4.

[0030] Zero compensation (output equals input):

[0031] Input AC 216.7 - 223.3V - - Thyristors S1 - S4 conduct (zero compensation) ΔUTB = 0V Output Uo ≈ AC 216.7 - 223.3V.

[0032] Positive compensation (boost):

[0033] Input AC 216.7 - 213.4V - - Thyristors S2 / S4 / S5 / S8 conduct (+1 compensation) ΔUTB = 3.3V Output Uo ≈ AC 220 - 216.7V;

[0034] Input AC 213.4 - 210.1V - - Thyristors S2 / S4 / S8 conduct (+2 compensation) ΔUTB = 6.6V Output Uo ≈ AC 220 - 216.7V;

[0035] Input AC 210.1 - 206.8V - - Thyristors S2 / S4 / S6 / S8 conduct (+3 compensation) ΔUTB = 9.9V Output Uo ≈ AC 220 - 216.7V;

[0036] …

[0037] Input AC 190.3 - 187V - - Thyristors S2 / S4 / S7 / S10 conduct (+9 compensation) ΔUTB = 29.7V Output Uo ≈ AC 220 - 216.7V;

[0038] Input below AC 187V - - Thyristors S2 / S4 / S10 conduct (+10 compensation) ΔUTB = 33V Output Uo ≈ AC 220 - below 220V.

[0039] Negative compensation (step - down):

[0040] Input AC 223.3 - 226.6V - - Thyristors S1 / S3 / S5 / S8 conduct (-1 compensation) ΔUTB = -3.3V Output Uo ≈ AC 220 - 223.3V;

[0041] Input AC 226.6 - 229.9V - - Thyristors S1 / S3 / S8 conduct (-2 compensation) ΔUTB = -6.6V Output Uo ≈ AC 220 - 223.3V;

[0042] Input AC 249.7 - 253V - - Thyristors S1 / S3 / S7 / S10 conduct (-9 compensation) ΔUTB = -29.7V Output Uo ≈ AC 220 - 223.3V;

[0043] Input above AC 253V - - Thyristors S1 / S3 / S10 conduct (-10 compensation) ΔUTB = -33V Output Uo ≈ AC 220 - above 220V.

[0044] As long as the input phase voltage of the voltage regulator is within the range of AC187V - AC253V, it can ensure that the output phase voltage of the voltage regulator is within AC220V ± 3.3V, that is, it meets the design requirements of accuracy AC220V ± 1.5%.

[0045] In summary, the present invention has the following beneficial effects:

[0046] (1) No circulating current; The zero-crossing point of the synchronous current signal of the current transformer (permanent magnet current sensor) LCa is used as the synchronous signal for the switching of the thyristor (S1 - S10) non-contact AC switch, ensuring that the non-contact voltage regulator accurately turns on the next thyristor combination to be turned on after the previous thyristor combination naturally turns off, thereby ensuring seamless, non-backpressure, and non-circulating current smooth switching of the primary compensation voltage of the compensation transformer TB of the voltage regulator, and finally ensuring that the output voltage waveform of the voltage regulator is intact, without dips, mutations, or distortions;

[0047] (2) No backpressure;

[0048] (3) A total of 21 levels of current zero-crossing step-by-step superposition compensation of +10, 0, -10, with non-circulating current and non-backpressure smooth switching;

[0049] (4) Improved voltage regulation accuracy; The three-port inductor realizes smooth adjustment of the compensation voltage of the non-contact voltage regulator and improves the voltage regulation accuracy. As long as the input phase voltage of the voltage regulator is within the range of AC187V - 253V, it can ensure that the output phase voltage of the voltage regulator is within AC220V ± 3.3V, that is, it meets the design requirements of accuracy AC220V ± 1.5%;

[0050] (5) Good output waveform. Description of the Drawings

[0051] Figure 1 For background reference Figure 1 ;

[0052] Figure 2 For background reference Figure 2 ;

[0053] Figure 3 This is the voltage regulation circuit diagram of the AC voltage regulator of the present invention. Specific Embodiments

[0054] The following further elaborates on the present invention in detail in conjunction with the embodiments and the drawings, but the implementation manners of the present invention are not limited thereto.

[0055] A non-contact AC voltage regulator voltage regulation circuit, as Figure 3As shown, the circuit connection principle and structure are as follows, including: compensation transformer TBa, voltage regulating transformer Tvva, thyristors S1 - S10, three - port inductor DLa, and current sensor LCa. Among them, the connection method of compensation transformer TBa is: one end of the secondary coil of compensation transformer TBa is connected to the positive pole of the voltage input terminal, and the other end of the secondary coil of compensation transformer TBa is connected to the positive pole of the voltage output terminal; the primary coil of compensation transformer TBa is electrically connected through several of thyristors S1 - S10, three - port inductor DLa, the control action of current sensor LCa, and the secondary coil of voltage regulating transformer Tvva to obtain voltage compensation values of different levels.

[0056] Among them, the connection method of voltage regulating transformer Tvva is: the secondary coil of voltage regulating transformer Tvva is a multi - tap autotransformer. Among them, the connection method of thyristors S1 - S10 is: one end of thyristor S1 and thyristor S4 is commonly electrically connected to one end of the primary coil of compensation transformer TBa, and one end of thyristor S2 and thyristor S3 is commonly electrically connected to the other end of the primary coil of compensation transformer TBa. The other ends of thyristor S1 and thyristor S2 are commonly electrically connected to the negative poles of the voltage input terminal and the voltage output terminal, and the other ends of thyristor S3 and thyristor S4 are commonly electrically connected to the middle connection terminal of three - port inductor DLa.

[0057] One end of thyristors S8, S9, and S10 is commonly electrically connected to one end of three - port inductor DLa, and the other ends of thyristors S8, S9, and S10 are respectively electrically connected to the 2 / 10, 6 / 10, and 10 / 10 positions of voltage regulating transformer Tvva. One end of thyristors S5, S6, and S7 is commonly electrically connected to the other end of three - port inductor DLa, and the other ends of thyristors S5, S6, and S7 are respectively electrically connected to the 0 / 10, 4 / 10, and 8 / 10 positions of voltage regulating transformer Tvva;

[0058] A current sensor LCa is electrically connected between the parallel connection end of thyristors S3 and S4 and the middle connection terminal of three - port inductor DLa. Thyristor S3 is electrically connected to one end of the primary coil of compensation transformer TBa where it is connected to thyristors S1 and S4 through a control switch QJa.

[0059] The working principle is as follows: The voltage regulating transformer Tvva is an ordinary single-phase autotransformer. When the input is single-phase AC220V, it has 6 output combinations of 0V, AC60V, AC120V, AC180V, AC240V, and AC300V. The thyristor S5 - S10 AC switch combination is cross-connected to the corresponding output positions of the voltage regulating transformer Tvva in geometric progression. Specific connection method: S5 is connected to 0V, S6 is connected to AC120V, S7 is connected to AC240V, and then the other ends of the three thyristor S5 / S6 / S7 AC switches are connected in parallel and then connected to the head end of the three-port inductor DL; S8 is connected to 60V, S9 is connected to AC180V, S10 is connected to AC300V, and then the other ends of the three thyristor S8 / S9 / S10 AC switches are connected in parallel and then connected to the tail end of the three-port inductor DL; the middle end of the three-port inductor DL is connected to the parallel connection of the commutation thyristors S3 and S4, so that a total of 21 levels of step-by-step compensation superposition principle of +10 levels, 0, and -10 levels can be carried out.

[0060] The specific compensation principle for each level is as follows:

[0061] The first case: zero compensation (output equals input):

[0062] Input AC216.7 - 223.3V - The thyristors S1 - S4 are turned on (zero compensation) ΔUTB = 0V, and the output Uo ≈ AC216.7 - 223.3V.

[0063] The second case: positive compensation (boost):

[0064] Input AC216.7 - 213.4V - The thyristors S2 / S4 / S5 / S8 are turned on (+1 compensation) ΔUTB = 3.3V, and the output Uo ≈ AC220 - 216.7V;

[0065] Input AC213.4 - 210.1V - The thyristors S2 / S4 / S8 are turned on (+2 compensation) ΔUTB = 6.6V, and the output Uo ≈ AC220 - 216.7V;

[0066] Input AC210.1 - 206.8V - The thyristors S2 / S4 / S6 / S8 are turned on (+3 compensation) ΔUTB = 9.9V, and the output Uo ≈ AC220 - 216.7V;

[0067] Input AC190.3 - 187V - The thyristors S2 / S4 / S7 / S10 are turned on (+9 compensation) ΔUTB = 29.7V, and the output Uo ≈ AC220 - 216.7V;

[0068] Input below AC187V - The thyristors S2 / S4 / S10 are turned on (+10 compensation) ΔUTB = 33V, and the output Uo ≈ AC220 - below AC220V.

[0069] Negative compensation (step-down):

[0070] Input AC223.3 - 226.6V - Thyristors S1 / S3 / S5 / S8 conduct (-1 compensation) ΔUTB = -3.3V Output Uo ≈ AC220 - 223.3V;

[0071] Input AC226.6 - 229.9V - Thyristors S1 / S3 / S8 conduct (-2 compensation) ΔUTB = -6.6V Output Uo ≈ AC220 - 223.3V;

[0072] …

[0073] Input AC249.7 - 253V - Thyristors S1 / S3 / S7 / S10 conduct (-9 compensation) ΔUTB = -29.7V Output Uo ≈ AC220 - 223.3V;

[0074] Input above AC253V - Thyristors S1 / S3 / S10 conduct (-10 compensation) ΔUTB = -33V Output Uo ≈ AC220 - above 220V.

[0075] Therefore, as long as the input phase voltage of the voltage regulator is within the range of AC187V - AC253V, it can ensure that the output phase voltage of the voltage regulator is within AC220V ± 3.3V, that is, it meets the design requirements of the accuracy of AC220V ± 1.5%.

[0076] At the same time, the zero-crossing point of the current signal of the current transformer (permanent magnet current sensor) LCa is used as the synchronization signal for the switching of the contactless AC switch of the thyristors (S1 - S10), ensuring that the contactless voltage regulator accurately turns on the next set of thyristor combinations to be turned on after the previous set of thyristor combinations is naturally turned off, thereby ensuring that the primary compensation voltage of the compensation transformer TB of the voltage regulator is uninterrupted, without reverse voltage, and without circulating current.

[0077] The above is only the preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A contactless AC voltage stabilizer voltage regulation circuit, characterized in that, comprising: A three-port inductor DLa and a current sensor LCa; A compensation transformer TBa, One end of the secondary coil of the compensation transformer TBa is connected to the positive pole of the voltage input terminal, and the other end of the secondary coil of the compensation transformer TBa is connected to the positive pole of the voltage output terminal; The primary coil of the compensation transformer TBa is electrically connected through several of the thyristors S1 - S10, the control action of the three-port inductor DLa, the current sensor LCa, and the secondary coil of the voltage regulating transformer Tvva to obtain different levels of voltage compensation values; A voltage regulating transformer Tvva, The secondary coil of the voltage regulating transformer Tvva is a multi-tap autotransformer; Thyristors S1 - S10, One end of thyristor S1 and thyristor S4 are commonly electrically connected to one end of the primary coil of the compensation transformer TBa, and one end of thyristor S2 and thyristor S3 are commonly electrically connected to the other end of the primary coil of the compensation transformer TBa; The other ends of thyristor S1 and thyristor S2 are commonly connected to the negative poles of the voltage input terminal and the voltage output terminal, and the other ends of thyristor S3 and thyristor S4 are commonly connected to the middle connection terminal of the three-port inductor DLa; One end of thyristors S8, S9, and S10 are commonly connected to one end of the three-port inductor DLa, and the other ends of thyristors S8, S9, and S10 are respectively connected to the 2 / 10, 6 / 10, and 10 / 10 positions of the voltage regulating transformer Tvva; One end of thyristors S5, S6, and S7 are commonly connected to the other end of the three-port inductor DLa, and the other ends of thyristors S5, S6, and S7 are respectively connected to the 0 / 10, 4 / 10, and 8 / 10 positions of the voltage regulating transformer Tvva; A current sensor LCa is electrically connected between the parallel connection end of thyristors S3 and S4 and the middle connection terminal of the three-port inductor DLa; Thyristor S3 is electrically connected to the end of the primary coil of the compensation transformer TBa where it is connected to thyristors S1 and S4 through a control switch QJa.

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