Three-phase balancing and reactive power compensation device and control method for electric railway single-phase traction substation

Abstract

The present invention discloses a three-phase balancing and reactive power compensation device and control method for an electric railway single-phase traction substation, which relates to the technical field of electrified railways, and includes: two single-phase compensation transformers and three single-phase voltage source converters; the first single-phase voltage source converter is connected to the transmission line and the positive feeder through a first connection reactor; the second single-phase voltage source converter is connected to the two electrical terminals of the low-voltage winding of the first single-phase compensation transformer through a second connection reactor; the third single-phase voltage source converter is connected to the two electrical terminals of the low-voltage winding of the second single-phase compensation transformer through a third connection reactor; the high-voltage winding terminals of the two single-phase compensation transformers are connected to a three-phase high-voltage power supply. The present invention alleviates the technical problems of high negative sequence content and three-phase imbalance in the single-phase traction substation in the prior art.

Description

Technical Field

[0001] The invention relates to the technical field of electrified railways, and in particular to a three-phase balancing and reactive power compensation device and a control method for an electric railway single-phase traction substation. Background Art

[0002] Electrified railways are typical nonlinear, volatile, and three-phase asymmetric loads, which produce power quality interference problems such as harmonic distortion, voltage fluctuations, flicker, and three-phase imbalance during operation. Currently, mainstream trains use new AC-DC-AC EMU traction, which significantly reduces the harmonic content and has fallen within the tolerance range of the power grid, and generally no filtering devices are installed.

[0003] The low-voltage side of the electric railway traction substation is single-phase or two-phase power supply, and its asymmetric power supply will generate negative sequence components in the power system. Although the unbalanced impact of the electric railway has been reduced by connecting to grid nodes with larger short-circuit capacity and higher voltage levels, and by rotating phases between traction substations, the problem has not been effectively solved. Negative sequence current generates negative sequence rotating magnetic field and pulsating torque in the generator, causing the generator to vibrate and the rotor to overheat locally, which harms the equipment. Compared with the three-phase V, v (x) connection traction transformer used in traction substations, the use of single-phase transformers has the advantages of better adaptability to changes in traction loads, stronger power supply capacity of the traction power supply system, and smaller project investment. At present, more and more traction substation transformers use single-phase transformers. However, the negative sequence content of single-phase transformers is higher, the three-phase imbalance problem is more serious, and its management is more difficult.

[0004] The locomotive has a high natural power factor and does not generate reactive power. However, due to the existence of no-load current and leakage reactance, the traction transformer generally has a reactive loss of about 10%. This reactive component will also lower the power factor, increase network losses, and cause problems such as voltage drop, voltage fluctuation and flicker in the traction substation, reduce the economic efficiency of the grid operation, and even affect the safe and stable operation of the locomotive. With the development of electrified railways and the increase in the load of electrified railways, the above-mentioned negative sequence and reactive power problems still seriously affect the safe operation of the grid. In order to limit the impact and harm of electrified railways on the grid and ensure the safe and stable operation of the grid and traction power supply system, corresponding power quality management measures should be taken to balance the three-phase current on the high-voltage power supply line side of the traction substation, increase the power factor to 1.0, and minimize the impact and harm of the traction substation on the power quality of the grid.

[0005] In order to control the negative sequence and imbalance problems of the electric railway system, domestic and foreign engineers have proposed many related patent technologies. For example, the domestic invention patent of the same type "Compensation device for reactive power compensation and power quality control of electrified railways (application number: CN200610089396.7)" provides a compensation device for reactive power compensation and power quality control of electrified railways, which is not suitable for traction substations using single-phase transformers. For example, the domestic invention patent of the same type "An electric railway traction power supply network power quality comprehensive management device (application number: CN201310353901.4)" discloses an electric railway traction power supply network power quality comprehensive management device, which is suitable for harmonic filtering and has a very limited improvement on three-phase imbalance. Summary of the invention

[0006] The purpose of the present invention is to provide a three-phase balancing and reactive power compensation device and control method for a single-phase traction substation of an electric railway in order to solve at least one of the above-mentioned technical problems.

[0007] In the first aspect, an embodiment of the present invention provides a three-phase balancing and reactive power compensation device for a single-phase traction substation of an electric railway, which is applied to the traction substation of the electric railway; the high-voltage winding terminals of the single-phase traction transformer of the traction substation are connected to the three-phase high-voltage power supply of the traction substation, and the low-voltage winding terminals of the single-phase traction transformer are connected to the transmission line and the positive feeder line of the electric railway; the compensation device includes: a first single-phase compensation transformer and a second single-phase compensation transformer which are hot standby for each other, and a first single-phase voltage source converter, a second single-phase voltage source converter and a third single-phase voltage source converter connected in parallel on the DC side; the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter share a group of supporting capacitors; the first AC port of the first single-phase voltage source converter is connected through a first The connecting inductor is connected to the transmission line, and the second AC port of the first single-phase voltage source converter is connected to the positive feed line; the first AC port of the second single-phase voltage source converter is connected to one end of the second connecting inductor, and the second AC port of the second single-phase voltage source converter and the other end of the second connecting inductor are respectively connected to the two electrical terminals of the low-voltage winding of the first single-phase compensation transformer; the first AC port of the third single-phase voltage source converter is connected to one end of the third connecting inductor, and the second AC port of the third single-phase voltage source converter and the other end of the third connecting inductor are respectively connected to the two electrical terminals of the low-voltage winding of the second single-phase compensation transformer; the high-voltage winding terminals of the first single-phase compensation transformer and the second single-phase compensation transformer are connected to the three-phase high-voltage power supply.

[0008] Furthermore, the high-voltage winding terminals of the single-phase traction transformer are connected to phases A and B of the three-phase high-voltage power supply; the high-voltage winding terminals of the first single-phase compensation transformer are connected to phases B and C of the three-phase high-voltage power supply; and the high-voltage winding terminals of the second single-phase compensation transformer are connected to phases C and A of the three-phase high-voltage power supply.

[0009] Furthermore, a midpoint terminal of the low-voltage winding of the single-phase traction transformer is grounded.

[0010] Furthermore, the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter are all single-phase bridge voltage source converters.

[0011] Furthermore, the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter all adopt a two-level full-bridge topology structure, and the power devices adopt insulated gate bipolar transistors.

[0012] In the second aspect, an embodiment of the present invention further provides a control method for a three-phase balancing and reactive compensation device of a single-phase traction substation of an electric railway, which is applied to the three-phase balancing and reactive compensation device of a single-phase traction substation of an electric railway provided by an embodiment of the present invention; the method comprises: obtaining the effective value and phase angle of the current flowing into the transmission line on the low-voltage side of the single-phase traction transformer; based on the effective value of the current and the phase angle, respectively determining the target currents of the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter; based on the target currents and actual working currents of the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter, using current hysteresis comparison, PWM modulation and carrier phase shift PWM methods, respectively outputting power device control signals of the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter.

[0013] Furthermore, the target current of the first single-phase voltage source converter includes:

[0014]

[0015] Among them, I VSC1 is the target current of the first single-phase voltage source converter, I VSC1-p is the active current component of the first single-phase voltage source converter, I VSC1-q is the reactive current component of the first single-phase voltage source converter, I rms is the effective value of the current, θ is the phase angle, K P is the proportional gain coefficient, U dc is the DC voltage across the supporting capacitor, U dcrefis the target DC voltage of the support capacitor, K i is the integral gain coefficient, ω is the electrical angle per unit time, t is the time, β is the load rate, U k is the short-circuit voltage drop percentage of the single-phase traction transformer, I n2 is the rated current of the low-voltage winding of the single-phase traction transformer, and I0 is the no-load current percentage of the single-phase traction transformer.

[0016] Furthermore, the target current of the second single-phase voltage source converter includes:

[0017]

[0018] Among them, I VSC2 is the target current of the second single-phase voltage source converter, I VSC2-q1 is the reactive current component of the second single-phase voltage source converter used for balancing the three-phase traction load, I VSC2-q2 is the reactive current component used by the second single-phase voltage source converter to compensate for the reactive loss of the first single-phase compensation transformer itself, U kc is the short-circuit voltage drop percentage of the first single-phase compensating transformer and the second single-phase compensating transformer, I nc2 is the rated current of the low voltage winding of the first single-phase compensating transformer and the second single-phase compensating transformer, I 0c It is the no-load current percentage of the first single-phase compensating transformer and the second single-phase compensating transformer.

[0019] Furthermore, the target current of the third single-phase voltage source converter includes:

[0020]

[0021] Among them, I VSC3 is the target current of the third single-phase voltage source converter, I VSC3-q1 is the reactive current component of the third single-phase voltage source converter used for balancing the three-phase traction load, I VSC3-q2 The reactive current component of the third single-phase voltage source converter used to compensate for the reactive loss of the second single-phase compensation transformer itself.

[0022] Further, based on the target current and actual working current of the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter, current hysteresis comparison, PWM modulation and carrier phase-shift PWM methods are adopted to output power device control signals of the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter respectively, including: based on the target current and actual working current of the first single-phase voltage source converter, current hysteresis comparison, PWM modulation and carrier phase-shift PWM methods are adopted to output the power device control signal of the first single-phase voltage source converter; based on the target current and actual working current of the second single-phase voltage source converter, current hysteresis comparison, PWM modulation and carrier phase-shift PWM methods are adopted to output the power device control signal of the second single-phase voltage source converter; based on the target current and actual working current of the third single-phase voltage source converter, current hysteresis comparison, PWM modulation and carrier phase-shift PWM methods are adopted to output the power device control signal of the third single-phase voltage source converter.

[0023] The present invention provides a three-phase balancing and reactive power compensation device and control method for a single-phase traction substation of an electric railway, which can dynamically track and compensate, and has a good control effect on voltage fluctuations and flicker interference caused by rapid fluctuations in active power and reactive power of the traction substation, thereby alleviating the technical problems of high negative sequence content and three-phase imbalance in single-phase traction substations in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 An electrical main wiring diagram of a three-phase balancing and reactive power compensation device for a single-phase traction substation of an electric railway provided by an embodiment of the present invention;

[0026] Figure 2 A flow chart of a control method for a three-phase balancing and reactive power compensation device of a single-phase traction substation of an electric railway provided by an embodiment of the present invention;

[0027] Figure 3 A flow chart of calculating a target current for a first single-phase voltage source converter provided by an embodiment of the present invention;

[0028] Figure 4 A flow chart of calculating a target current for a second single-phase voltage source converter provided by an embodiment of the present invention;

[0029] Figure 5 A flow chart of calculating a target current for a third single-phase voltage source converter provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Embodiment 1

[0032] Figure 1 This is the main electrical connection diagram of a three-phase balancing and reactive power compensation device for a single-phase traction substation of an electric railway provided according to an embodiment of the present invention. Figure 1 As shown, the compensation device is applied to the traction substation of the electric railway; the high-voltage winding terminals of the single-phase traction transformer B0 of the traction substation are connected to the three-phase high-voltage power supply of the traction substation, and the low-voltage winding terminals of the single-phase traction transformer B0 are connected to the transmission line (T) and the positive feeder line (F) of the electric railway.

[0033] Specifically, Figure 1 As shown, the compensation device provided by the embodiment of the present invention includes: a first single-phase compensation transformer B1 and a second single-phase compensation transformer B2 which are hot standby for each other, and a first single-phase voltage source converter VSC1, a second single-phase voltage source converter VSC2 and a third single-phase voltage source converter VSC3 which are connected in parallel on the DC side; the first single-phase voltage source converter VSC1, the second single-phase voltage source converter VSC2 and the third single-phase voltage source converter VSC3 share a group of supporting capacitors C.

[0034] Specifically, the first AC port of the first single-phase voltage source converter VSC1 is connected to the transmission line through the first connecting reactor L1, and the second AC port of the first single-phase voltage source converter VSC1 is connected to the positive feeder line;

[0035] The first AC port of the second single-phase voltage source converter VSC2 is connected to one end of the second connection reactor L2, and the second AC port of the second single-phase voltage source converter VSC2 and the other end of the second connection reactor L2 are respectively connected to two electrical terminals of the low-voltage winding of the first single-phase compensation transformer B1;

[0036] The first AC port of the third single-phase voltage source converter VSC3 is connected to one end of the third connection reactor L3, and the second AC port of the third single-phase voltage source converter VSC3 and the other end of the third connection reactor L3 are respectively connected to two electrical terminals of the low-voltage winding of the second single-phase compensation transformer B2;

[0037] The high-voltage winding terminals of the first single-phase compensating transformer B1 and the second single-phase compensating transformer B2 are connected to a three-phase high-voltage power supply.

[0038] Specifically, the high-voltage winding terminals of the single-phase traction transformer B0 are connected to the A-phase and B-phase of the three-phase high-voltage power supply; the high-voltage winding terminals of the first single-phase compensation transformer B1 are connected to the B-phase and C-phase of the three-phase high-voltage power supply; the high-voltage winding terminals of the second single-phase compensation transformer B2 are connected to the C-phase and A-phase of the three-phase high-voltage power supply. The midpoint terminal of the low-voltage winding of the single-phase traction transformer B0 is grounded.

[0039] In the embodiment of the present invention, the traction substation introduces two independent high-voltage power supplies, which are hot standby for each other. When one circuit fails, the other circuit can still supply power normally. The traction substation is equipped with two single-phase traction transformers, one of which is in operation and the other is in standby. Since the traction substation uses a single power supply and a single-phase transformer for power supply in normal operation, in order to simplify the wiring diagram, the traction substation in the present invention only draws a single three-phase power supply and a single-phase transformer, such as Figure 1 shown.

[0040] The single-phase traction transformer B0 has two windings and five terminals, of which the high-voltage winding terminals are 1 and 2, and the low-voltage winding terminals are 3, 4 and 5. Terminals 1 and 3 are the same-name terminals, and terminal 4 is the midpoint of the low-voltage winding. Two phases of the three-phase high-voltage power supply A, B, and C are connected to the high-voltage terminals 1 and 3 of the single-phase traction transformer B0 (such as Figure 1 As shown, the connected phases are A and B). The low voltage terminal 3 of the single-phase traction transformer B0 is connected to the transmission line (T), the low voltage terminal 5 is connected to the positive feeder (F), and the low voltage midpoint terminal 4 is directly grounded and has the same potential as the rail.

[0041] Specifically, Figure 1 As shown, the AC ports of the first single-phase voltage source converter VSC1 are K1 and K2, and the first connection inductor L1 is connected to the AC port K1; the AC ports of the second single-phase voltage source converter VSC2 are K3 and K4, and the second connection inductor L2 is connected to the AC port K3; the AC ports of the third single-phase voltage source converter VSC3 are K5 and K6, and the third connection inductor L3 is connected to the AC port K5.

[0042] The electrical terminal K1 of the first single-phase voltage source converter VSC1 is connected to the transmission line (T) through the first connecting inductor L1, and the electrical terminal K2 is directly connected to the positive feeder (F); the electrical terminal K3 of the second single-phase voltage source converter VSC2 is connected to the electrical terminal 3 of the first single-phase compensation transformer B1 through the second connecting inductor L2, and the electrical terminal K4 is directly connected to the electrical terminal 4 of the first single-phase compensation transformer B1; the electrical terminal K5 of the third single-phase voltage source converter VSC3 is connected to the electrical terminal 3 of the second single-phase compensation transformer B2 through the third connecting inductor L3, and the electrical terminal K6 is directly connected to the electrical terminal 4 of the second single-phase compensation transformer B2.

[0043] Specifically, Figure 1 As shown, the first single-phase compensating transformer B1 has two windings and four terminals, of which the high-voltage winding terminals are 1 and 2, and the low-voltage winding terminals are 3 and 4, and terminals 1 and 3 are terminals of the same name. The high-voltage terminal 1 of the first single-phase compensating transformer B1 is connected to the high-voltage power supply phase B, the high-voltage terminal 2 is connected to the high-voltage power supply phase C, the low-voltage terminal 3 is connected to the electrical terminal K3 of the second single-phase voltage source converter VSC2 through the second connecting reactor L2, and the low-voltage terminal 4 is directly connected to the electrical terminal K4 of the second single-phase voltage source converter VSC2.

[0044] Specifically, Figure 1 As shown, the second single-phase compensating transformer B2 has two windings and four terminals, of which the high-voltage winding terminals are 1 and 2, and the low-voltage winding terminals are 3 and 4, and terminals 1 and 3 are terminals of the same name. The high-voltage terminal 1 of the second single-phase compensating transformer B2 is connected to the high-voltage power supply phase C, the high-voltage terminal 2 is connected to the high-voltage power supply phase A, the low-voltage terminal 3 is connected to the electrical terminal K5 of the third single-phase voltage source converter VSC3 through the third connecting reactor L3, and the low-voltage terminal 4 is directly connected to the electrical terminal K6 of the third single-phase voltage source converter VSC3.

[0045] The above wiring method is explained by connecting the high-voltage winding terminal 1 of the single-phase traction transformer B0 of the traction substation to the high-voltage power supply phase A, and the high-voltage winding terminal 2 to the high-voltage power supply phase B. When the traction substation adopts other wiring phases, the wiring of the compensation device shall be adjusted accordingly. The principle of adjustment is to ensure that the high-voltage power supply connected to the high-voltage side terminals 1 and 2 of the first single-phase compensation transformer B1 lags behind the high-voltage power supply connected to the high-voltage winding terminals 1 and 2 of the single-phase traction transformer B0 by 120 degrees, while the high-voltage power supply connected to the high-voltage side terminals 1 and 2 of the second single-phase compensation transformer B2 is 120 degrees ahead of the high-voltage power supply connected to the high-voltage winding terminals 1 and 2 of the single-phase traction transformer B0.

[0046] In the embodiment of the present invention, the first single-phase voltage source converter VSC1, the second single-phase voltage source converter VSC2 and the third single-phase voltage source converter VSC3 are all single-phase bridge voltage source converters.

[0047] Optionally, the first single-phase voltage source converter VSC1, the second single-phase voltage source converter VSC2 and the third single-phase voltage source converter VSC3 may adopt a two-level, three-level or cascade multi-level topology structure, and the power devices may be composed of turn-off devices such as IGBT and IGCT. Preferably, the first single-phase voltage source converter VSC1, the second single-phase voltage source converter VSC2 and the third single-phase voltage source converter VSC3 all adopt a two-level full-bridge topology structure, and the power devices are insulated-gate bipolar transistors (IGBT) G1~G 12 .

[0048] Specifically, Figure 1 As shown, the first connected reactor L1 and the fully controlled G1~G4 are combined into a first single-phase voltage source converter VSC1, the second connected reactor L2 and the fully controlled G5~G8 are combined into a second single-phase voltage source converter VSC2, and the third connected reactor L3 and the fully controlled G9~G 12 Combined into a third single-phase voltage source converter VSC3.

[0049] In the embodiment of the present invention, the power devices G1~G 12 The control signal is T1~T 12 When the control model T1 is greater than 0, the full-control device G1 is turned off; when the control model T1 is less than 0, the full-control device G1 is turned on; and so on.

[0050] In an optional implementation provided by the embodiment of the present invention, in order to save equipment space, a Vv connection transformer may be used to replace the two single-phase compensation transformers B1 and B2.

[0051] The equipment parameters of a three-phase balancing and reactive power compensation device for a single-phase traction substation of an electric railway provided by an embodiment of the present invention are as follows:

[0052] The rated voltage of the single-phase traction transformer B0 is U1 / U2, where U1 is the rated voltage of the high-voltage winding and U2 is the rated voltage of the low-voltage winding, in kV, and the transformation ratio K=U1 / U2; the rated capacity is S n , unit MVA; short-circuit impedance U k , unit: %; no-load current I0, unit: %; I n2 It is the rated current of low voltage winding, unit is A.

[0053] The rated voltage of the first single-phase compensation transformer B1 is also U1 / U2, where U1 is the rated voltage of the high-voltage winding, U2 is the rated voltage of the low-voltage winding, the unit is kV, the transformation ratio K=U1 / U2, and the rated capacity is S nc , unit MVA, short-circuit impedance Ukc , unit %, no-load current I 0c , unit:%I nc2 It is the rated current of low voltage winding, unit is A.

[0054] The rated voltage of the second single-phase compensation transformer B2 is also U1 / U2, where U1 is the rated voltage of the high-voltage winding, U2 is the rated voltage of the low-voltage winding, the unit is kV, the transformation ratio K=U1 / U2, and the rated capacity is also S nc , unit MVA, short-circuit impedance is also U kc , unit %, no-load current is also I 0c , unit:%I nc2 Also the rated current of the low voltage winding, unit is A.

[0055] The rated capacity S of the first single-phase compensation transformer B1 nc , the rated capacity Snc of the second single-phase compensation transformer B2 and the rated capacity Snc of the single-phase traction transformer B0 n Satisfies the following relationship:

[0056] The inductance values ​​of the first connected reactor L1, the second connected reactor L2, and the third connected reactor L3 are all L c .

[0057] The capacitance value of the supporting capacitor C is C f , the unit is uF.

[0058] For example, in an optional implementation manner provided by an embodiment of the present invention, the device parameters are as follows:

[0059] The voltage on the grid side is 110kV, the system equivalent resistance is R=2Ω, and the equivalent reactance is L=10mH.

[0060] The locomotive load of the traction substation is equivalent to 20Ω, corresponding to a working current of 1375A, an active power of 37.8MW, and a power factor of approximately 1.

[0061] The rated voltage of the single-phase traction transformer B0 is 110 / 27.5kV, of which U1 is the high-voltage winding rated voltage of 115kV, U2 is the low-voltage winding rated voltage of 27.5kV, and the transformation ratio K=U1 / U2=4; the rated capacity is S n =50MVA; short-circuit impedance U k =10.5%; no-load current I0=0.2%; I n2 is the rated current of the low voltage winding, I n2 =1818A.

[0062] The rated voltage of the first single-phase compensating transformer B1 is also 110 / 27.5kV, where U1 is the rated voltage of the high-voltage winding 115kV, U2 is the rated voltage of the low-voltage winding 27.5kV, and the transformation ratio K=U1 / U2=4; the rated capacity is S nc =28.87MVA, short-circuit impedance U kc =10.5%; no-load current I 0c =0.2%; I nc2 is the rated current of the low voltage winding, I nc2 =1050A.

[0063] The rated voltage of the second single-phase compensation transformer B2 is also 110 / 27.5kV, where U1 is the rated voltage of the high-voltage winding 115kV, U2 is the rated voltage of the low-voltage winding 27.5kV, and the transformation ratio K=U1 / U2=4; the rated capacity is S nc =28.87MVA, short-circuit impedance U kc =10.5%; no-load current I 0c =0.2%; I nc2 is the rated current of the low voltage winding, I nc2 =1050A.

[0064] The inductance values ​​of the first connected reactor L1, the second connected reactor L2, and the third connected reactor L3 are all L c =50mH.

[0065] The capacitance value C of the supporting capacitor C f =10000uF.

[0066] Embodiment 2

[0067] Figure 2 This is a flow chart of a control method of a three-phase balancing and reactive power compensation device for a single-phase traction substation of an electric railway provided according to an embodiment of the present invention. The algorithm is applied to the three-phase balancing and reactive power compensation device for a single-phase traction substation of an electric railway provided according to an embodiment of the present invention. Figure 2 As shown, the method specifically comprises the following steps:

[0068] Step S202, obtaining the effective value and phase angle of the current flowing into the transmission line on the low-voltage side of the single-phase traction transformer.

[0069] Step S204, based on the effective value of the current and the phase angle, respectively determine the target currents of the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter.

[0070] Step S206, based on the target current and actual operating current of the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter, adopt current hysteresis comparison, PWM modulation and carrier phase-shift PWM method to output power device control signals of the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter respectively.

[0071] Specifically, in order to achieve three-phase balancing and dynamic reactive power compensation, the effective value of the current I flowing into the transmission line (T) on the low-voltage side of the single-phase traction transformer B0 should be rms and phase angle θ for detection, where the effective current value I rms The unit is A, and the unit of phase angle θ is electrical degree °. It should be noted that the phase angle θ refers to the phase angle difference between the voltage between the low-voltage winding terminal 3 and the terminal 5 of the single-phase traction transformer B0 and the current flowing into the transmission line (T) from the low-voltage terminal 3. Currently, mainstream trains are all pulled by AC-DC-AC EMUs. The load characteristics of AC-DC-AC EMUs are characterized by a high power factor (the full-load power factor is generally close to 1), so the value of the current electrical angle θ is relatively small.

[0072] The current expression of the low voltage winding terminal 3 of the single-phase traction transformer B0 flowing into the transmission line (T) is:

[0073] Decompose the current I into active current I p and reactive current I q Two components:

[0074]

[0075] The output current of the first single-phase voltage source converter VSC1 is I1, the output current of the second single-phase voltage source converter VSC2 is I2, and the output current of the third single-phase voltage source converter VSC3 is I3. The current detection point and the positive direction are as follows: Figure 1 shown.

[0076] Figure 3 1 is a flow chart of calculating a target current of a first single-phase voltage source converter according to an embodiment of the present invention. Specifically, Figure 3 As shown, the calculation process of the target current of the first single-phase voltage source converter is as follows:

[0077] Establishing a stable DC voltage across the DC stabilizing capacitor (ie, the supporting capacitor C) is a prerequisite for the normal operation of the compensation device provided by the present invention, and this function is completed by the first single-phase voltage source converter VSC1.

[0078] The DC voltage across the DC stabilizing capacitor C is U dc , the target DC voltage is Udcref , will U dc and U dcref The proportional-integral control is performed on the difference, and the proportional-integral control output is calculated as the active current component I of the first single-phase voltage source converter VSC1 according to the following formula: VSC1-p :

[0079]

[0080] Where: K P is the proportional gain coefficient, K i is the integral gain coefficient; ω is the electrical angle per unit time, in degrees / s. ; t is time, the unit is s.

[0081] The reactive current component I of the first single-phase voltage source converter VSC1 VSC1-q It consists of two parts. The first part is the reactive current component I of the current flowing into the transmission line (T) from the low-voltage terminal 3. q The compensation value is calculated as follows:

[0082]

[0083] Where: I rms is the effective value of the current flowing into the transmission line (T) from the low-voltage side terminal 3 of the single-phase traction transformer B0, and the unit is A; θ is the electrical angle of the current flowing into the transmission line (T) from the low-voltage side terminal 3 of the single-phase traction transformer B0, and the unit is °.

[0084] The second part is the reactive power loss compensation of the single-phase traction transformer B0, and the calculation method is as follows:

[0085]

[0086] Where: I0 is the no-load current percentage of the single-phase traction transformer B0, unit is %; U k is the short-circuit voltage drop percentage of the single-phase traction transformer B0, in %; I n2 is the rated current of the low-voltage winding of the single-phase traction transformer B0, in A; β is the load factor, in %, and the calculation method is: .

[0087] The reactive current component I of the first single-phase voltage source converter VSC1 VSC1-q The calculation method is as follows:

[0088]

[0089] The active current component I of the first single-phase voltage source converter VSC1 is VSC1-p and reactive current component I VSC1-qThe target current of the first single-phase voltage source converter VSC1 is obtained by summing the currents, as shown in the following formula:

[0090]

[0091] Among them, I VSC1 is the target current of the first single-phase voltage source converter, I VSC1-p is the active current component of the first single-phase voltage source converter VSC1, I VSC1-q is the reactive current component of the first single-phase voltage source converter VSC1.

[0092] Figure 4 FIG. 1 is a flow chart of calculating a target current for a second single-phase voltage source converter according to an embodiment of the present invention. Specifically, Figure 4 As shown, the calculation process of the target current of the second single-phase voltage source converter is as follows:

[0093] The current component of the second single-phase voltage source converter VSC2 consists of two parts.

[0094] The first part is used for three-phase balancing of traction load, and the calculation method is as follows:

[0095]

[0096] The second part is used to compensate for the reactive power loss of the first single-phase compensation transformer B1 itself. The calculation method is as follows:

[0097]

[0098] Where: I 0C is the no-load current percentage of the first single-phase compensation transformer B1, in %; U kc is the short-circuit voltage drop percentage of the first single-phase compensation transformer B1, in units of %; I nc2 It is the rated current of the low-voltage winding of the first single-phase compensation transformer B1, in A.

[0099] The reactive current component I of the second single-phase voltage source converter VSC2 VSC2-q1 and reactive current component I VSC2-q2 The target current of the second single-phase voltage source converter VSC2 is obtained by summing the currents, as shown in the following formula:

[0100]

[0101] Among them, I VSC2 is the target current of the second single-phase voltage source converter, I VSC2-q1 is the reactive current component of the second single-phase voltage source converter used for balancing the three-phase traction load, I VSC2-q2It is the reactive current component used by the second single-phase voltage source converter to compensate for the reactive loss of the first single-phase compensation transformer itself.

[0102] Figure 5 FIG. 1 is a flow chart of calculating a target current for a third single-phase voltage source converter according to an embodiment of the present invention. Specifically, Figure 5 As shown, the calculation process of the target current of the third single-phase voltage source converter is as follows:

[0103] The current component of the third single-phase voltage source converter VSC3 consists of two parts.

[0104] The first part is used for three-phase balancing of traction load, and the calculation method is as follows:

[0105]

[0106] The second part is used for the reactive power loss compensation of the second single-phase compensation transformer B2 itself, and the calculation method is as follows:

[0107]

[0108] Where: I 0C is the no-load current percentage of the second single-phase compensation transformer B2, in %; U kc is the short-circuit voltage drop percentage of the second single-phase compensation transformer B2, in %; I nc2 is the rated current of the low voltage winding of the second single-phase compensating transformer B2, in A. It should be noted that, in the embodiment of the present invention, the equipment parameters of the first single-phase compensating transformer B1 and the second single-phase compensating transformer B2 are the same.

[0109] The reactive current component I VSC3-q1 and reactive current component I VSC3-q2 The target current of the third single-phase voltage source converter VSC3 is obtained by summing the currents, as shown in the following formula:

[0110]

[0111] Among them, I VSC3 is the target current of the third single-phase voltage source converter, I VSC3-q1 is the reactive current component of the third single-phase voltage source converter used for three-phase balancing of the traction load, I VSC3-q2 It is the reactive current component used by the third single-phase voltage source converter to compensate for the reactive loss of the second single-phase compensation transformer itself.

[0112] In the embodiment of the present invention, the actual working currents I1, I2, and I3 of the three groups of single-phase bridge voltage source converters VSC1, VSC2, and VSC3 should quickly and accurately track the target current I VSC1 ,IVSC2 ,I VSC3 Specifically, step S206 also includes the following steps:

[0113] Step S2061: based on the target current I of the first single-phase voltage source converter VSC1 VSC1 and the actual working current I1, and outputting the power device control signal of the first single-phase voltage source converter VSC1 by using current hysteresis comparison, PWM modulation and carrier phase shift PWM method;

[0114] Step S2062: based on the target current I of the second single-phase voltage source converter VSC2 VSC2 and the actual working current I2, and outputting the power device control signal of the second single-phase voltage source converter VSC2 by using current hysteresis comparison, PWM modulation and carrier phase shift PWM method;

[0115] Step S2063: based on the target current I of the third single-phase voltage source converter VSC3 VSC3 and the actual working current I3, and adopt current hysteresis comparison, PWM modulation and carrier phase-shift PWM method to output the power device control signal of the third single-phase voltage source converter VSC3.

[0116] The three-phase balancing and reactive power compensation device and control method of a single-phase traction substation of an electric railway provided by the embodiment of the present invention have the following technical effects compared with the prior art:

[0117] (1) The amount of detection is small, and only the effective value of the current I flowing into the transmission line (T) on the low-voltage side of the single-phase traction transformer B0 is required. rms By detecting the phase angle θ, the compensation target current calculation of the three groups of single-phase voltage source converters in the complete set can be realized;

[0118] (2) The compensation index is comprehensive. The compensation device and control method adopted by the present invention can not only achieve a power factor of 1 on the high-voltage incoming line side of the traction substation, but also make the three-phase current values ​​on the high-voltage power incoming line side consistent, the phases symmetrical, and the negative sequence current approximately 0, thereby minimizing the reactive power and negative sequence impact on the power grid;

[0119] (3) Dynamic tracking compensation. The compensation device and control method adopted by the present invention can dynamically track compensation, and also have a good control effect on the voltage fluctuation and flicker interference caused by the rapid fluctuation of active and reactive power in the traction substation.

[0120] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0121] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A three-phase balancing and reactive power compensation device for a single-phase traction substation of an electric railway, characterized in that: The invention is applied to a traction substation of an electric railway; the high-voltage winding terminal of the single-phase traction transformer of the traction substation is connected to the three-phase high-voltage power supply of the traction substation, and the low-voltage winding terminal of the single-phase traction transformer is connected to the transmission line and the positive feeder line of the electric railway; the compensation device comprises: a first single-phase compensation transformer and a second single-phase compensation transformer which are hot standby for each other, and a first single-phase voltage source converter, a second single-phase voltage source converter and a third single-phase voltage source converter which are connected in parallel with the DC side; the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter share a group of support capacitors; The first AC port of the first single-phase voltage source converter is connected to the transmission line through a first connecting reactor, and the second AC port of the first single-phase voltage source converter is connected to the positive feeder; The first AC port of the second single-phase voltage source converter is connected to one end of the second connection reactor, and the second AC port of the second single-phase voltage source converter and the other end of the second connection reactor are respectively connected to two electrical terminals of the low-voltage winding of the first single-phase compensation transformer; The first AC port of the third single-phase voltage source converter is connected to one end of the third connection reactor, and the second AC port of the third single-phase voltage source converter and the other end of the third connection reactor are respectively connected to two electrical terminals of the low-voltage winding of the second single-phase compensation transformer; The high-voltage winding terminals of the first single-phase compensating transformer and the second single-phase compensating transformer are connected to the three-phase high-voltage power supply; The high-voltage winding terminals of the single-phase traction transformer are connected to the A-phase and B-phase of the three-phase high-voltage power supply; the high-voltage winding terminals of the first single-phase compensation transformer are connected to the B-phase and C-phase of the three-phase high-voltage power supply; the high-voltage winding terminals of the second single-phase compensation transformer are connected to the C-phase and A-phase of the three-phase high-voltage power supply; The midpoint terminal of the low voltage winding of the single-phase traction transformer is grounded; The first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter are all single-phase bridge voltage source converters.

2. The three-phase balancing and reactive power compensation device for electric railway single-phase traction substation according to claim 1 is characterized in that: The first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter all adopt a two-level full-bridge topology structure, and the power devices adopt insulated gate bipolar transistors.

3. A control method for a three-phase balancing and reactive power compensation device of an electric railway single-phase traction substation, characterized in that: The three-phase balancing and reactive power compensation device for a single-phase traction substation of an electric railway as described in claim 1; the method comprises: Obtaining the effective value and phase angle of the current flowing into the transmission line from the single-phase traction transformer at the low voltage side; Based on the current effective value and the phase angle, respectively determine the target currents of the first single-phase voltage source converter, the second single-phase voltage source converter, and the third single-phase voltage source converter; Based on the target current and actual operating current of the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter, current hysteresis comparison, PWM modulation and carrier phase-shift PWM methods are adopted to output power device control signals of the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter respectively.

4. The method according to claim 3, characterized in that: The target current of the first single-phase voltage source converter includes: Among them, I VSC1 is the target current of the first single-phase voltage source converter, I VSC1-p is the active current component of the first single-phase voltage source converter, I VSC1-q is the reactive current component of the first single-phase voltage source converter, I rms is the effective value of the current, θ is the phase angle, K P is the proportional gain coefficient, U dc is the DC voltage across the supporting capacitor, U dcref is the target DC voltage of the support capacitor, K i is the integral gain coefficient, ω is the electrical angle per unit time, t is the time, β is the load rate, U k is the short-circuit voltage drop percentage of the single-phase traction transformer, I n2 is the rated current of the low-voltage winding of the single-phase traction transformer, and I0 is the no-load current percentage of the single-phase traction transformer.

5. The method according to claim 4, characterized in that: The target current of the second single-phase voltage source converter includes: Among them, I VSC2 is the target current of the second single-phase voltage source converter, I VSC2-q1 is the reactive current component of the second single-phase voltage source converter used for balancing the three-phase traction load, I VSC2-q2 is the reactive current component used by the second single-phase voltage source converter to compensate for the reactive loss of the first single-phase compensation transformer itself, U kc is the short-circuit voltage drop percentage of the first single-phase compensating transformer and the second single-phase compensating transformer, I nc2 is the rated current of the low voltage winding of the first single-phase compensating transformer and the second single-phase compensating transformer, I 0c It is the no-load current percentage of the first single-phase compensating transformer and the second single-phase compensating transformer.

6. The method according to claim 5, characterized in that: The target current of the third single-phase voltage source converter comprises: Among them, I VSC3 is the target current of the third single-phase voltage source converter, I VSC3-q1 is the reactive current component of the third single-phase voltage source converter used for balancing the three-phase traction load, I VSC3-q2 The reactive current component of the third single-phase voltage source converter used to compensate for the reactive loss of the second single-phase compensation transformer itself.

7. The method according to claim 3, characterized in that: Based on the target current and the actual working current of the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter, current hysteresis comparison, PWM modulation and carrier phase shift PWM methods are adopted to output power device control signals of the first single-phase voltage source converter, the second single-phase voltage source converter and the third single-phase voltage source converter respectively, including: Based on the target current and the actual working current of the first single-phase voltage source converter, a power device control signal of the first single-phase voltage source converter is outputted by using a current hysteresis comparison, PWM modulation and carrier phase shift PWM method; Based on the target current and the actual working current of the second single-phase voltage source converter, a power device control signal of the second single-phase voltage source converter is outputted by using a current hysteresis comparison, PWM modulation and a carrier phase shift PWM method; Based on the target current and actual operating current of the third single-phase voltage source converter, current hysteresis comparison, PWM modulation and carrier phase-shift PWM methods are adopted to output power device control signals of the third single-phase voltage source converter.

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