CN106099978A - Metro braking energy back feed device, control method for reactive-load compensation - Google Patents

Abstract

The invention relates to a subway braking energy feedback device and a control method for reactive power compensation, and uses a double closed loop of a voltage outer loop and a current inner loop to perform SVPWM control on an AC/DC converter. Adding I ^* q in the current inner loop is the q-axis current given value given by the dispatching command, and comparing it with the q-axis current value generates the q-axis voltage given value U ^* q. The q-axis voltage given value U ^* q, the d-axis voltage given value U ^* d and the phase angle θ are used for SVPWM control to control each power tube of the AC/DC converter. The invention provides a braking energy feedback device with both energy feedback and reactive power compensation functions, which improves the power factor of the line, is beneficial to the stability of the power grid and reduces operating costs.

Description

Subway braking energy feedback device and control method for reactive power compensation

technical field

The invention relates to a control method of a large-capacity subway braking energy feedback device with reactive power compensation function.

Background technique

With the continuous enhancement of my country's economic strength, the construction of urban rail transit projects across the country has entered a period of rapid development. The subway power supply system is a large electricity consumer in cities. The braking energy of subway vehicles accounts for more than 40% of the traction energy. The use of traditional resistance energy-consuming braking energy absorption devices results in wasteful consumption of braking energy, which not only fails to achieve energy saving, but increases burden on the environmental control system.

The Chinese patent document with publication number CN103475028A provides a brake feedback device. As shown in Figure 1 and Figure 2, in order to maximize the feedback utilization of subway braking, a medium-voltage grid-connected scheme is adopted. After DC/AC conversion, the braking energy is directly fed into the medium-voltage grid by the medium-voltage isolation transformer. The capacity of the medium-voltage power grid is large, and the instantaneous power will not cause an impact on the power grid. This scheme feeds the braking energy back to the medium-voltage grid, avoiding wasted energy consumption.

The load of the subway power supply system varies greatly. The power factor of the main substation reaches above 0.9 during the operation of the subway during the day, and the power factor of the main substation drops to about 0.3 when the load decreases at night. Insufficient power factor will not only affect the temperature of the grid, but also bring higher The cost, that is, the penalty due to insufficient power factor accounts for more than 10% of the total subway operation electricity fee.

Contents of the invention

The object of the present invention is to provide a control method of a subway braking energy feedback device with reactive power compensation function, so as to solve the problem that insufficient power factor affects the stability of the power grid. At the same time, the present invention also provides a subway braking energy feedback device using the above-mentioned control method.

To achieve the above object, the solution of the present invention includes:

The control method of the subway braking energy feedback device for reactive power compensation uses the double closed loop of the voltage outer loop and the current inner loop to perform PWM control on the AC/DC converter; the voltage given value U ^* dc and the AC/DC converter The difference between the DC side voltage Udc of the inverter is adjusted by PI as the current given value I ^* d of the current inner loop, and the difference between I ^* d and the d-axis current Id is used as the d-axis voltage given value U ^* d; the d-axis current Id, The q-axis current Iq is obtained by the coordinate transformation of the AC side current of the AC/DC converter, and the difference between I ^* q and Iq is adjusted by PI to obtain the given value of the q-axis voltage U ^* q; I ^* q is the q given by the dispatching instruction Axis current given value; d-axis voltage given value U ^* d, q-axis voltage given value U ^* q and phase angle θ are used for SVPWM control to control each power tube of AC/DC converter.

Further, the phase angle θ is obtained by collecting the voltage of the medium-voltage grid through a phase-locked PLL.

Furthermore, according to the real-time power factor of the line, the control center calculates the reactive power capacity that needs to be compensated and distributes it at each station on the whole line, and issues control commands to determine the I ^* q of each station.

The present invention also provides a subway braking energy feedback device for reactive power compensation, including an AC/DC converter, the DC side of the AC/DC converter is connected to a DC traction power grid, and the AC side is connected to a medium-voltage network through a transformer; The braking energy feedback device of the subway adopts the double closed loop of the voltage outer loop and the current inner loop to perform ^PWM control on the AC/DC converter; Adjust the current given value I ^* d as the current inner loop, the difference between I ^* d and the d-axis current Id is used as the d-axis voltage given value U ^* d; the d-axis current Id and the q-axis current Iq are converted by AC/DC The current on the AC side of the inverter is obtained through coordinate transformation, and the difference between I ^* q and Iq is adjusted by PI to obtain the given value of the q-axis voltage U ^* q; I ^* q is the given value of the q-axis current given by the dispatching command; the given value of the d-axis voltage is The fixed value U ^* d, the q-axis voltage given value U ^* q and the phase angle θ are used for SVPWM control to control each power tube of the AC/DC converter.

Further, the phase angle θ is obtained by collecting the voltage of the medium-voltage grid through a phase-locked PLL.

Furthermore, according to the real-time power factor of the line, the control center calculates the reactive power capacity that needs to be compensated and distributes it at each station on the whole line, and issues control commands to determine the I ^* q of each station.

Further, the medium voltage network is a 35kV network.

The invention provides a braking energy feedback device with both energy feedback and reactive power compensation functions, which can realize two control functions at the same time. The first is to convert the DC energy generated by subway braking into AC energy and feed it back to the medium voltage The network is used by the electrical equipment of the entire line to realize energy feedback and utilization; secondly, and more importantly, the converter provides reactive power compensation to the power supply system according to the dispatching instructions, thereby improving the power factor of the line , which is conducive to the stability of the power grid and the reduction of operating costs.

Description of drawings

Fig. 1 is a structural diagram of a braking energy feedback device;

Fig. 2 is the topological diagram of the AC/DC converter of the braking energy feedback device;

Fig. 3 is a control structure diagram of the braking energy feedback device.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings.

The present invention is a braking energy feedback device with both energy feedback and reactive power compensation functions, as shown in Figure 3, the specific control method is:

SVPWM is carried out on the AC/DC converter by adopting the double closed loop of the voltage outer loop and the current inner loop. Using SVPWM control can improve voltage utilization.

The difference between the voltage given value U ^* dc and the DC side voltage Udc of the AC/DC converter is adjusted by PI as the current given value I ^* d of the current inner loop, and the difference between I ^* d and the d-axis current Id is used as the d-axis voltage The given value U ^* d, Id, and Iq are obtained from the AC side current of the AC/DC converter through coordinate transformation, and the difference between I ^* q and Iq is adjusted by PI to obtain the given value of the q-axis voltage U ^* q; I ^* q is The given value of the q-axis current given by the scheduling instruction. The d-axis voltage given value U ^* d, the q-axis voltage given value U ^* q and the phase angle θ are used for SVPWM control to control each power tube of the AC/DC converter.

Among them, the phase angle θ is obtained by collecting the medium-voltage 35kV grid voltage through a phase-locked PLL.

The above control method uses the feedforward decoupling method to separate the active component and reactive component of the AC current, and controls the output active power through the active component, and controls the output reactive power through the reactive component. In this way, the control of feedback active power and reactive power compensation can be realized at the same time, and I ^* q can be given for dispatching instructions, realizing automatic compensation of reactive power. The feedback device conducts data communication with the control center of the power supply system through Ethernet. According to the real-time power factor of the line, the control center calculates the reactive power capacity that needs to be compensated and distributes it reasonably at each station on the whole line, and issues control commands to determine the power of each station. I ^* q.

In order to avoid affecting the normal operation of the rectifier unit when the feedback device fails, the feedback device is equipped with an independent frame protection. When the DC frame leakage or DC short circuit occurs in the feedback device, only the feedback device will stop running, which will not affect the normal operation of the power supply system. affect the normal operation of the subway.

The present invention meets the application requirements of large-capacity energy feedback and reactive power compensation of the subway regenerative braking, and designs a converter device with both energy feedback and reactive power compensation functions, which provides a solution to the problems of energy feedback and reactive power compensation in the subway power supply system. New solution ideas.

The specific embodiments related to the present invention are given above, but the present invention is not limited to the described embodiments. Under the idea given by the present invention, the technical means in the above-mentioned embodiments are transformed, replaced, and modified in ways that are easy for those skilled in the art, and the functions played are basically the same as those of the corresponding technical means in the present invention. 1. The purpose of the invention realized is also basically the same, and the technical solution formed in this way is formed by fine-tuning the above-mentioned embodiments, and this technical solution still falls within the protection scope of the present invention.

Claims (7)

1. for the control method of metro braking energy back feed device of reactive-load compensation, it is characterised in that use outer voltage and The two close cycles of current inner loop carries out PWM control to AC/DC current transformer；

Voltage set-point U^*The difference of dc with AC/DC current transformer DC voltage Udc is given as the electric current of current inner loop through PI regulation Definite value I^*D, I^*The difference of d Yu d shaft current Id is as d shaft voltage set-point U^*d；

D shaft current Id, q shaft current Iq are obtained through coordinate transform by AC/DC AC side of converter electric current, I^*The difference of q Yu Iq is passed through PI regulation obtains q shaft voltage set-point U^*q；I^*Q is the q shaft current set-point that dispatch command is given；

D shaft voltage set-point U^*D, q shaft voltage set-point U^*Q and phase angle theta control for SVPWM, control each of AC/DC current transformer Power tube.

The control method of the metro braking energy back feed device for reactive-load compensation the most according to claim 1, its feature Being, phase angle theta, by gathering medium voltage network voltage, obtains through phase-locked PLL.

The control method of the metro braking energy back feed device for reactive-load compensation the most according to claim 1, its feature Being, control centre, according to circuit realtime power factor situation, calculates the reactive power capacity needing to compensate and at the most each station Point distribution, sends control command, determines the I of each website^*q。

4. for the metro braking energy back feed device of reactive-load compensation, it is characterised in that include AC/DC current transformer, AC/DC unsteady flow Device DC side connects DC traction electrical network, and AC connects middle-voltage network by transformator；Metro braking energy back feed device is adopted With the two close cycles of outer voltage and current inner loop, AC/DC current transformer is carried out PWM control；

Voltage set-point U^*The difference of dc with AC/DC current transformer DC voltage Udc is given as the electric current of current inner loop through PI regulation Definite value I^*D, I^*The difference of d Yu d shaft current Id is as d shaft voltage set-point U^*d；

D shaft current Id, q shaft current Iq are obtained through coordinate transform by AC/DC AC side of converter electric current, I^*The difference of q Yu Iq is passed through PI regulation obtains q shaft voltage set-point U^*q；I^*Q is the q shaft current set-point that dispatch command is given；

D shaft voltage set-point U^*D, q shaft voltage set-point U^*Q and phase angle theta control for SVPWM, control each of AC/DC current transformer Power tube.

Metro braking energy back feed device for reactive-load compensation the most according to claim 4, it is characterised in that phase angle theta By gathering medium voltage network voltage, obtain through phase-locked PLL.

Metro braking energy back feed device for reactive-load compensation the most according to claim 4, it is characterised in that in control The heart, according to circuit realtime power factor situation, calculates the reactive power capacity needing to compensate and in each website distribution completely, sends Control command, determines the I of each website^*q。

Metro braking energy back feed device for reactive-load compensation the most according to claim 4, it is characterised in that in described Pressure network network is 35kV network.