# Two-Sided Matching Decision Method of Electricity Sales Package Based on Disappointment Theory
## 2 Construction of Evaluation Index System for Electric Power Customers and Power-Selling Companies
### Electric Power Customers' Evaluation Index of Electricity Sales Package
#### 2.1.2 Power Quality
Therefore, when formulating the power-selling plan, the power-selling company needs to consider the impact of harmonic current comprehensively and install some adaptive filters to reduce harmonic, thus reducing losses, reducing the burden of electricity charges of electric power customers, and protecting equipment and lines to a certain extent, which can effectively control the daily operation and maintenance costs [24]. The detection methods of harmonic active current, reactive current, and load harmonic current were described in detail in [25]. In the study of power grid power quality, the total harmonic distortion rate (THD) is generally used to characterize the harmonic level of the power grid, and the specific formula is as follows:  
\[THD=\frac{\sqrt{\sum\limits_{h=2}^{\infty}{U_{h}}^{2}}}{U_{1}}\times 100\% \tag{2}\]  
where \(U_{1}\), \(U_{h}\) are the amplitude of the harmonic voltage and the amplitude of the fundamental voltage. Three-phase voltage unbalance refers to the inconsistent amplitude or phase angle of three-phase voltage. When a three-phase voltage unbalance occurs, negative sequence current and zero sequence current will be generated correspondingly, which will cause serious loss and great voltage drop to the power line, and interfere with the communication system, resulting in the heating, vibration, and loss of the rotating motor and transformer, and affecting the service life of the electrical equipment [26]. Its degree is characterized by three-phase voltage unbalance, which is generally calculated by the ratio of the effective value of the negative sequence component of voltage or current to the positive sequence component. Three-phase voltage imbalance has different degrees of impact on the power supply and distribution system, mainly on transformers, electrical equipment, and transmission lines. It will lead to an increase in transformer load loss, a reduction in overload capacity, an increase in core eddy current loss, and an intensification of heating, reducing the service life of the transformer. For ordinary electric power customers, three-phase load asymmetry will lead to the deviation of the neutral point, resulting in the problem of user voltage deviation, and leading to the unstable operation of electrical equipment. In the process of current transmission, the greater the three-phase unbalance, the greater the line loss, and the lower the economy of power transmission will be [27]. Therefore, when electric power customers choose power-selling companies, three-phase voltage unbalance is also an important consideration index. The lower its value, the more economical and high-quality the power supply will be. In a three-phase power system, three-phase unbalance is usually expressed quantitatively by three-phase voltage unbalance rate (PVUR):  
\[PVUR=\frac{\max\{|V_{A}-\overline{V}|,|V_{B}-\overline{V}|,|V_{C}-\overline{V }|\}}{\overline{V}}\times 100\% \tag{3}\]  
where \(V_{A},~{}V_{B},~{}V_{C}\) respectively represents the \(A,~{}B,~{}C\) phase voltage, and \(\overline{V}\) is the value of three-phase voltage.